The principle of operation of a heat pump for heating. Heat pump for home heating: principle of operation, varieties and use. Some features of the operation of pumps

By the end of the 19th century, powerful refrigeration units appeared that could pump heat at least twice as much as the energy wasted to activate them. It was a shock, because formally it turned out that a thermal perpetual motion machine is possible! However, upon closer examination, it turned out that it is still far from the perpetual motion machine, and the low-grade heat produced by a heat pump and the high-grade heat obtained, for example, by burning fuel, are two big differences. True, the corresponding formulation of the second principle was somewhat modified. So what are heat pumps? In a nutshell, a heat pump is a modern and high-tech appliance for heating and air conditioning. Heat pump collects heat from the street or from the ground and directs it into the house.

How the heat pump works

How the heat pump works simple: due to mechanical work or other types of energy, it provides a concentration of heat, previously uniformly distributed over a certain volume, in one part of this volume. In the other part, respectively, a heat deficit is formed, that is, cold.

Historically, heat pumps were first widely used as refrigerators - in fact, any refrigerator is a heat pump that pumps heat from the refrigeration chamber to the outside (into a room or outside). There is still no alternative to these devices, and with all the variety of modern refrigeration technology, the basic principle remains the same: heat pumping out from the refrigerating chamber due to additional external energy.

Naturally, almost immediately they noticed that the noticeable heating of the condenser heat exchanger (in a household refrigerator, it is usually made in the form of a black panel or grate on the back of the cabinet) could also be used for heating. This was already the idea of \u200b\u200ba heater based on a heat pump in its modern form - a refrigerator, on the contrary, when heat is pumped into a closed volume (room) from an unlimited external volume (from the street). However, the heat pump has a lot of competitors in this area - from traditional wood-burning stoves and fireplaces to all kinds of modern heating systems. Therefore, for many years, while fuel was relatively cheap, this idea was considered nothing more than a curiosity - in most cases it was absolutely unprofitable economically, and only very rarely was such use justified - usually for the recovery of heat pumped out by powerful refrigeration units in countries with not too cold climate. And only with the rapid rise in energy prices, the complication and rise in the cost of heating equipment and the relative decrease in the cost of production of heat pumps against this background, such an idea becomes economically viable in itself, because having paid once for a rather complex and expensive installation, then it will be possible to constantly save on reduced fuel consumption. Heat pumps are the basis of the increasingly popular ideas of cogeneration - the simultaneous production of heat and cold - and trigeneration - the production of heat, cold and electricity at once.

Since a heat pump is the essence of any refrigeration unit, it can be said that the term "refrigeration machine" is its pseudonym. True, it should be borne in mind that despite the versatility of the operating principles used, the designs of refrigeration machines are still focused specifically on the production of cold, and not heat - for example, the generated cold is concentrated in one place, and the resulting heat can be dissipated in several different parts of the installation. , because in an ordinary refrigerator the task is not to utilize this heat, but simply to get rid of it.

Heat pump classes

Currently, two classes of heat pumps are most widely used. One class includes thermoelectric ones based on the Peltier effect, and the other - evaporative ones, which, in turn, are subdivided into mechanical compressor (piston or turbine) and absorption (diffusion) ones. In addition, interest in the use of vortex tubes in which the Ranque effect works as heat pumps is gradually increasing.

Peltier heat pumps

Peltier element

The Peltier effect is that when a small DC voltage is applied to two sides of a specially prepared semiconductor wafer, one side of this wafer heats up and the other cools. So, in general, the thermoelectric heat pump is ready!

The physical essence of the effect is as follows. The plate of the Peltier element (aka "thermoelectric element", English Thermoelectric Cooler, TEC), consists of two semiconductor layers with different levels of electron energy in the conduction band. When an electron passes under the influence of an external voltage into a higher-energy conduction band of another semiconductor, it must acquire energy. When it receives this energy, the semiconductor contact point is cooled (when current flows in the opposite direction, the opposite effect occurs - the layer contact point heats up in addition to the usual ohmic heating).

Advantages of Peltier elements

The advantage of Peltier elements is the maximum simplicity of their design (what could be simpler than a plate to which two wires are soldered?) And the complete absence of any moving parts, as well as internal flows of liquids or gases. The consequence of this is the absolute quiet operation, compactness, complete indifference to orientation in space (provided sufficient heat dissipation is provided) and very high resistance to vibration and shock loads. And the operating voltage is only a few volts, so a few batteries or a car battery are enough for operation.

Disadvantages of Peltier elements

The main disadvantage of thermoelectric elements is their relatively low efficiency - roughly it can be considered that they will need twice as much of the supplied external energy per unit of pumped heat. That is, by supplying 1 J of electrical energy, we can remove only 0.5 J of heat from the cooled region. It is clear that all the total 1.5 J will be allocated on the "warm" side of the Peltier element and they will need to be taken to the external environment. This is many times lower than the efficiency of compressional evaporative heat pumps.

Against the background of such a low efficiency, the other disadvantages are usually not so important, and this is a low specific productivity combined with a high specific cost.

Using Peltier elements

In accordance with their characteristics, the main field of application of Peltier elements is currently usually limited to cases when it is required not to cool too much something that is not too powerful, especially in conditions of strong shaking and vibrations and with strict restrictions on weight and dimensions, for example, various units and parts of electronic equipment, primarily military, aviation and space. Perhaps, Peltier elements are most widely used in everyday life in low-power (5..30 W) portable car refrigerators.

Evaporative Compression Heat Pumps

Working cycle diagram of an evaporative compression heat pump

The principle of operation of this class of heat pumps is as follows. Gaseous (in whole or in part) refrigerant is compressed by the compressor to a pressure at which it can turn into liquid. Naturally, this heats up. The heated compressed refrigerant is fed to the condenser radiator, where it is cooled to ambient temperature, giving off excess heat to it. This is the heating zone (back of the kitchen refrigerator). If at the inlet of the condenser a significant part of the compressed hot refrigerant still remained in the form of vapor, then with a decrease in temperature during heat exchange it also condenses and turns into a liquid state. Relatively cooled liquid refrigerant is fed into the expansion chamber, where, passing through a throttle or expander, it loses pressure, expands and evaporates, at least partially turns into a gaseous form, and, accordingly, is cooled - significantly below the ambient temperature and even below the temperature in cooling zone of the heat pump. Passing through the channels of the evaporator panel, the cold mixture of liquid and vaporous heat transfer agent removes heat from the cooling zone. Due to this heat, the remaining liquid part of the refrigerant continues to evaporate, maintaining a consistently low evaporator temperature and ensuring effective heat extraction. After that, the refrigerant in the form of vapor reaches the compressor inlet, which evacuates and compresses it again. Then everything is repeated from the beginning.

Thus, in the "hot" section of the compressor-condenser-throttle, the refrigerant is under high pressure and predominantly in a liquid state, and in the "cold" section of the throttle-evaporator-compressor, the pressure is low, and the refrigerant is mainly in the vapor state. Both compression and vacuum are generated by the same compressor. On the opposite side from the compressor, the high and low pressure zones are separated by a throttle limiting the refrigerant flow.

High-power industrial refrigerators use toxic but effective ammonia as a refrigerant, high-performance turbochargers and sometimes expanders. In household refrigerators and air conditioners, the refrigerant is usually safer freons, and piston compressors and "capillary tubes" (throttles) are used instead of turbine units.

In the general case, a change in the state of aggregation of the refrigerant is not necessary - the principle will also work for a permanently gaseous refrigerant - however, the high heat of a change in the state of aggregation greatly increases the efficiency of the working cycle. But if the refrigerant stays in liquid form all the time, the effect will not be fundamental - after all, the liquid is practically incompressible, and therefore neither increasing nor relieving pressure will change its temperature.

Chokes and expanders

The terms "choke" and "expander", which are often used on this page, usually mean little to people far from refrigeration technology. Therefore, a few words should be said about these devices and the main difference between them.

A throttle in technology is a device designed to normalize the flow due to its forced limitation. In electrical engineering, this name was assigned to coils designed to limit the rate of rise of current and are usually used to protect electrical circuits from impulse noise. In hydraulics, throttles are usually called flow restrictors, which are specially created channel restrictions with a precisely calculated (calibrated) clearance that provides the required flow or the required flow resistance. A classic example of such chokes are jets, which are widely used in carburetor engines to provide the estimated gasoline flow when preparing the fuel mixture. The throttle valve in the same carburetors normalized the air flow - the second essential ingredient in this mixture.

In refrigeration technology, a throttle is used to restrict the flow of refrigerant into the expansion chamber and maintain conditions there for effective evaporation and adiabatic expansion. Too much flow can generally lead to filling the expansion chamber with refrigerant (the compressor simply does not have time to pump it out) or, at least, to the loss of the required vacuum there. But it is the evaporation of the liquid refrigerant and the adiabatic expansion of its vapors that provide the refrigerant temperature drop necessary for the operation of the refrigerator below the ambient temperature.

Principles of operation of the throttle (left), piston expander (center) and turbo expander (left).

In the expander, the expansion chamber has been slightly modernized. In it, the evaporating and expanding refrigerant performs additional mechanical work, moving the piston located there or rotating the turbine. In this case, the restriction of the refrigerant flow can be carried out due to the resistance of the piston or turbine wheel, although in reality this usually requires very careful selection and coordination of all system parameters. Therefore, even when using expanders, the main flow rate regulation can be carried out by a throttle (calibrated narrowing of the liquid coolant supply channel).

The turboexpander is effective only at large flows of the working fluid; at low flows, its efficiency is close to conventional throttling. A piston expander can work effectively with a much lower flow rate of the working fluid, but its design is an order of magnitude more complicated than a turbine: in addition to the piston itself with all the necessary guides, seals and a return system, inlet and outlet valves with appropriate control are required.

The advantage of the expander over the choke is more efficient cooling due to the fact that part of the thermal energy of the refrigerant is converted into mechanical work and in this form is removed from the heat cycle. Moreover, this work can then be used profitably for the cause, say, for driving pumps and compressors, as is done in the "Zysin refrigerator". But a simple choke has an absolutely primitive design and does not contain a single moving part, and therefore, in terms of reliability, durability, as well as simplicity and production cost, leaves the expander far behind. It is these reasons that usually limit the scope of application of expanders to powerful cryogenic technology, and in household refrigerators, less efficient, but practically eternal throttles are used, called there "capillary tubes" and which are a simple copper tube of a sufficiently long length with a small diameter lumen mm), which provides the required hydraulic resistance for the calculated refrigerant flow.

Advantages of compression heat pumps

The main advantage of this type of heat pump is their high efficiency, the highest among modern heat pumps. The ratio of the energy supplied from the outside to the pumped-in energy can reach 1: 3 - that is, for each joule of supplied energy, 3 J of heat will be pumped out from the cooling zone - compare with 0.5 J for Pelte elements! In this case, the compressor can stand separately, and the heat generated by it (1 J) does not have to be removed to the external environment in the same place where 3 J of heat pumped out from the cooling zone is given off.

By the way, there is a different from the generally accepted, but very curious and convincing theory of thermodynamic phenomena. So, one of her conclusions is that the work of compressing a gas, in principle, can be only about 30% of its total energy. And this means that the ratio of the supplied and pumped energy 1: 3 corresponds to the theoretical limit and with thermodynamic methods of heat transfer cannot be improved in principle. However, some manufacturers already claim to achieve a ratio of 1: 5 and even 1: 6, and this is true - after all, in real refrigeration cycles, not only the compression of the gaseous refrigerant is used, but also a change in its state of aggregation, and that is last trial is the main ...

Disadvantages of compression heat pumps

The disadvantages of these heat pumps include, firstly, the very presence of a compressor, which inevitably creates noise and is subject to wear, and secondly, the need to use a special refrigerant and maintain absolute tightness throughout its working path. However, household compression refrigerators that have been operating continuously for 20 years or more without any repairs are not at all uncommon. Another feature is a rather high sensitivity to position in space. Both the refrigerator and the air conditioner are unlikely to work on its side or upside down. But this is due to the peculiarities of specific designs, and not to the general principle of operation.

As a rule, compression heat pumps and refrigeration units are designed with all the refrigerant in vapor state at the compressor inlet. Therefore, a large amount of non-evaporated liquid refrigerant entering the compressor inlet can cause water hammer in it and, as a result, serious damage to the unit. The reason for this situation can be both equipment wear and a too low condenser temperature - the refrigerant entering the evaporator is too cold and evaporates too sluggishly. For an ordinary refrigerator, this situation can arise if you try to turn it on in a very cold room (for example, at a temperature of about 0 ° C and below) or if it has just been brought into a normal room from frost. For a heating compression heat pump, this can happen if you try to warm a frozen room with it, despite the fact that it is also cold outside. Not very complex technical solutions eliminate this danger, but they increase the cost of the design, and during the regular operation of mass household appliances they are not needed - such situations do not arise.

The use of compression heat pumps

Due to its high efficiency, this particular type of heat pump has become almost ubiquitous, displacing all others in various exotic areas of application. And even the relative complexity of the design and its sensitivity to damage cannot limit their widespread use - almost every kitchen has a compression refrigerator or freezer, or even more than one!

Evaporative absorption (diffusion) heat pumps

Working cycle of evaporative absorption heat pumps very similar to the duty cycle of the evaporative compression units discussed above. The main difference is that if in the previous case the vacuum required for the evaporation of the refrigerant is created by mechanical suction of vapors by the compressor, then in the absorption units the evaporated refrigerant flows from the evaporator to the absorber unit, where it is absorbed (absorbed) by another substance - the absorbent. Thus, the vapor is removed from the volume of the evaporator and the vacuum is restored there, ensuring the evaporation of new portions of the refrigerant. A necessary condition is such an "affinity" of the refrigerant and absorbent so that the forces of their binding during absorption could create a significant vacuum in the volume of the evaporator. Historically, the first and still widely used pair of substances are ammonia NH3 (refrigerant) and water (absorbent). When absorbed, ammonia vapors dissolve in water, penetrating (diffusing) into its thickness. From this process came alternative names such heat pumps - diffusion or absorption-diffusion.
In order to separate the refrigerant (ammonia) and absorbent (water) again, the spent and ammonia-rich ammonia-water mixture is heated in a desorber by an external source of thermal energy until boiling, then cooled somewhat. Water condenses first, but at high temperatures immediately after condensation, it is able to retain very little ammonia, so most of the ammonia remains in the form of vapor. Here, the pressurized liquid (water) and gaseous (ammonia) are separated and separately cooled to ambient temperature. The cooled water with a low ammonia content is sent to the absorber, and when cooled in the condenser, ammonia becomes liquid and enters the evaporator. There, the pressure drops, and the ammonia evaporates, again cooling the evaporator and taking heat from the outside. Then again the vapors of ammonia are combined with water, removing excess ammonia vapors from the evaporator and maintaining a low pressure there. The solution enriched with ammonia is again sent to the stripper for separation. In principle, to desorb ammonia, it is not necessary to boil the solution, it is enough just to heat it close to the boiling point, and the "excess" ammonia will evaporate from the water. But boiling allows for the fastest and most efficient separation. The quality of such a separation is the main condition that determines the vacuum in the evaporator, and therefore, the efficiency of the absorption unit, and many tricks in the design are aimed precisely at this. As a result, in terms of the organization and number of stages of the working cycle, absorption-diffusion heat pumps are perhaps the most complex of all common types of such equipment.

The "highlight" of the principle of operation is that to generate cold, the working fluid is heated here (up to its boiling). In this case, the type of heating source is not critical - it can even be an open fire (burner flame), so the use of electricity is not necessary. To create the required pressure difference, which determines the movement of the working fluid, sometimes mechanical pumps can be used (usually in powerful installations with large volumes of the working fluid), and sometimes, in particular in household refrigerators, elements without moving parts (thermosyphons).

Absorption-diffusion refrigeration unit (ADKhA) of the Morozko-ZM refrigerator. 1 - heat exchanger; 2 - a collection of solution; 3 - hydrogen accumulator; 4 - absorber; 5 - regenerative gas heat exchanger; 6 - reflux condenser ("degreaser"); 7 - capacitor; 8 - evaporator; 9 - generator; 10 - thermosiphon; 11 - regenerator; 12 - tubes of a weak solution; 13 - steam outlet pipe; 14 - electric heater; 15 - thermal insulation.

The first absorption refrigeration machines (ABCM) based on ammonia-water mixture appeared in the second half of the 19th century. In everyday life, due to the toxicity of ammonia, they did not receive much distribution at that time, but they were very widely used in industry, providing cooling down to –45 ° С. In single-stage ABHM, theoretically, the maximum refrigerating capacity is equal to the amount of heat spent on heating (in reality, of course, it is much less). It was this fact that reinforced the confidence of the defenders of the very formulation of the second law of thermodynamics, which was mentioned at the beginning of this page. However, absorption heat pumps have now overcome this limitation. In the 1950s, more efficient two-stage (two condensers or two absorbers) lithium bromide ABKhM appeared (the refrigerant is water, the absorbent is lithium bromide LiBr). Three-stage ABHM variants were patented in 1985-1993. Their prototype samples are superior in efficiency to two-stage ones by 30-50% and are close to the mass models of compression units.

Advantages of absorption heat pumps

The main advantage of absorption heat pumps is the ability to use for their work not only expensive electricity, but also any heat source of sufficient temperature and power - overheated or exhaust steam, gas, gasoline and any other burners flame - up to exhaust gases and free solar energy.

The second advantage of these units, especially valuable in domestic applications, is the ability to create structures that do not contain moving parts, and therefore are practically silent (in Soviet models of this type, sometimes you could hear a quiet gurgling or slight hiss, but, of course, this does not go either in what comparison with the noise of a running compressor).

Finally, in household models, the working fluid (usually a water-ammonia mixture with the addition of hydrogen or helium) in the volumes used there does not pose a great danger to others, even in the event of an emergency depressurization of the working part (this is accompanied by a very unpleasant stench, so that you do not notice a strong leak impossible, and the room with the emergency unit will have to leave and ventilate "automatically"; ultra-low concentrations of ammonia are natural and absolutely harmless). In industrial plants, the volumes of ammonia are large and the concentration of ammonia during leaks can be fatal, but in any case, ammonia is considered environmentally friendly - it is believed that, unlike freons, it does not destroy the ozone layer and does not cause a greenhouse effect.

Disadvantages of absorption heat pumps

The main disadvantage of this type of heat pump - lower efficiency compared to compression.

The second drawback is the complexity of the design of the unit itself and a rather high corrosion load from the working fluid, either requiring the use of expensive and difficult to machine corrosion-resistant materials, or reducing the service life of the unit to 5-7 years. As a result, the cost of "hardware" is significantly higher than that of compression plants of the same capacity (first of all, it concerns powerful industrial units).

Thirdly, many designs are very critical to placement during installation - in particular, some models of household refrigerators required installation strictly horizontally, and refused to work even after a deviation of several degrees. The use of forced displacement of the working fluid with the help of pumps largely alleviates the severity of this problem, but lifting with a silent thermosyphon and draining by gravity requires very careful alignment of the unit.

Unlike compression machines, absorption machines are not so afraid of too low temperatures - their efficiency simply decreases. But it's not for nothing that I put this paragraph in the disadvantages section, because this does not mean that they can work in a fierce cold - in the cold, an aqueous solution of ammonia will freeze banally, unlike freons used in compression machines, the freezing point of which is usually below -100 ° C. True, if the ice does not break anything, then after thawing, the absorption unit will continue to work, even if it has not been disconnected from the network all this time, because there are no mechanical pumps and compressors in it, and the heating power in household models is small enough to boil in the area the heater has not become too intense. However, all this already depends on the features of a particular design ...

The use of absorption heat pumps

Despite the somewhat lower efficiency and relatively higher cost compared to compression units, the use of absorption heat engines is absolutely justified where there is no electricity or where there are large volumes of waste heat (waste steam, hot exhaust or flue gases, etc. - up to pre-solar heating). In particular, special models of refrigerators are produced, powered by gas burners, intended for travelers, motorists and yachtsmen.

Currently in Europe gas boilers sometimes they are replaced by absorption heat pumps heated from a gas burner or diesel fuel - they allow not only to utilize the heat of combustion of the fuel, but also to "pump" additional heat from the street or from the depths of the earth!

Experience shows that in everyday life, options with electric heating are quite competitive, primarily in the range of low powers - somewhere from 20 to 100 W. Smaller powers are the domain of thermoelectric elements, while higher powers are still unconditional advantages of compression systems. In particular, among the Soviet and post-Soviet brands of refrigerators of this type were popular "Morozko", "Sever", "Kristall", "Kiev" with a typical volume of the refrigerating chamber from 30 to 140 liters, although there are models for 260 liters (" Crystal-12 "). By the way, when evaluating energy consumption, one should take into account the fact that compression refrigerators almost always operate in a short-period mode, while absorption refrigerators are usually turned on for a much longer period or generally operate continuously. Therefore, even if the rated power of the heater is much less than the power of the compressor, the ratio of the average daily energy consumption may be quite different.

Vortex heat pumps

Vortex heat pumps use the Ranque effect to separate warm and cold air. The essence of the effect lies in the fact that the gas tangentially supplied to the pipe at high speed swirls and separates inside this pipe: cooled gas can be taken from the center of the pipe, and heated gas can be taken from the periphery. The same effect, although to a much lesser extent, also applies to liquids.

Advantages of vortex heat pumps

The main advantage of this type of heat pump is its simplicity of design and high performance. The vortex tube contains no moving parts, which ensures high reliability and long service life. Vibration and position in space have practically no effect on its operation.

The powerful air flow is good at preventing freezing, and the efficiency of the vortex tubes is weakly dependent on the temperature of the inlet flow. It is also very important that there are no fundamental temperature limitations associated with hypothermia, overheating or freezing of the working fluid.

In some cases, the possibility of achieving a record high temperature separation at one stage plays a role: in the literature, cooling figures are given by 200 ° and more. Usually one stage cools the air by 50..80 ° С.

Disadvantages of vortex heat pumps

Unfortunately, the efficiency of these devices is now noticeably inferior to the efficiency of evaporative compression units. In addition, for efficient operation, they require a high feed rate of the working fluid. The maximum efficiency is observed at an input flow rate equal to 40..50% of the speed of sound - such a flow itself creates a lot of noise, and besides, it requires an efficient and powerful compressor - the device is also not quiet and rather capricious.

The lack of a generally accepted theory of this phenomenon, suitable for practical engineering use, makes the design of such units an empirical exercise in many respects, where the result is highly dependent on luck: “guessed - did not guess”. A more or less reliable result is provided only by the reproduction of already created successful samples, and the results of attempts to significantly change certain parameters are not always predictable and sometimes look paradoxical.

Use of vortex heat pumps

However, the use of such devices is currently expanding. They are justified primarily where there is already gas under pressure, as well as in various fire and explosive industries - after all, supplying a flow of air under pressure to a hazardous area is often much safer and cheaper than pulling protected electrical wiring there and installing electric motors in a special design ...

Efficiency limits of heat pumps

Why is it that heat pumps have not yet become widespread for heating (perhaps the only relatively common class of such devices is air conditioners with an inverter)? There are several reasons for this, and in addition to subjective ones associated with the lack of traditions of heating using this technique, there are also objective ones, the main ones of which are the freezing of the heat sink and a relatively narrow temperature range for effective operation.

In vortex (primarily gas) installations, there are usually no problems of hypothermia and freezing. They do not use a change in the state of aggregation of the working fluid, and a powerful air flow performs the functions of the "No Frost" system. However, their efficiency is much lower than that of evaporative heat pumps.

Hypothermia

In evaporative heat pumps, high efficiency is ensured by changing the state of aggregation of the working fluid - the transition from liquid to gas and vice versa. Accordingly, this process is possible in a relatively narrow temperature range. At too high temperatures, the working fluid will always remain gaseous, and at too low temperatures it will evaporate with great difficulty or even freeze. As a result, when the temperature goes beyond the optimal range, the most energy-efficient phase transition becomes difficult or completely excluded from the operating cycle, and the efficiency of the compression unit drops significantly, and if the refrigerant remains constantly liquid, then it will not work at all.

Freezing

Extraction of heat from the air

Even if the temperatures of all the heat pump units remain within the required limits, during operation the heat extraction unit - the evaporator - is always covered with moisture droplets condensing from the ambient air. But liquid water drains from it by itself, not particularly hindering heat transfer. When the temperature of the evaporator gets too low, the condensate drops freeze, and the newly condensed moisture immediately turns into frost, which remains on the evaporator, gradually forming a thick snow "coat" - this is exactly what happens in the freezer of a conventional refrigerator. As a result, the efficiency of heat exchange is significantly reduced, and then you have to stop work and thaw the evaporator. As a rule, in the refrigerator evaporator the temperature drops by 25..50 ° C, and in air conditioners due to their specificity the temperature difference is less - 10..15 ° C. Knowing this, it becomes clear why most air conditioners cannot be adjusted to a temperature lower +13 .. + 17 ° С - this threshold was set by their designers in order to avoid icing of the evaporator, because its defrosting mode is usually not provided. This is one of the reasons why almost all air conditioners with inverter mode do not work even at not very high negative temperatures - only in the very recent times models designed to operate in temperatures down to –25 ° C began to appear. In most cases, even at –5 ..– 10 ° C, the energy consumption for defrosting becomes comparable to the amount of heat pumped from the street, and heat pumping from the street turns out to be ineffective, especially if the outside air humidity is close to 100% - then the external heat collector is covered with ice especially fast.

Extraction of heat from soil and water

In this regard, heat from the depths of the earth is increasingly considered as a non-freezing source of "cold heat" for heat pumps. In this case, we mean by no means heated layers of the earth's crust, located at a depth of many kilometers, and not even geothermal water sources (although, if you are lucky and they are nearby, it would be foolish to neglect such a gift of fate). This refers to the "normal" heat of soil layers located at a depth of 5 to 50 meters. As you know, in the middle lane, the soil at such depths has a temperature of about + 5 ° C, which changes very little throughout the year. In more southern regions, this temperature can reach + 10 ° C and higher. Thus, the temperature difference between the comfortable + 25 ° С and the ground around the heat sink is very stable and does not exceed 20 ° С regardless of the frost outside the window (it should be noted that usually the temperature at the heat pump outlet is +50 .. + 60 ° С, but and a temperature difference of 50 ° C is quite capable of heat pumps, including modern household refrigerators, which calmly provide -18 ° C in the freezer when the room temperature is above + 30 ° C).

However, if you bury one compact but powerful heat exchanger, you will hardly be able to achieve the desired effect. In fact, the heat sink in this case acts as an evaporator of the freezer, and if in the place where it is located there is no powerful influx of heat (geothermal source or underground river), it will quickly freeze the surrounding soil, which will end all heat pumping. The solution may be to extract heat not from one point, but evenly from a large underground volume, however, the cost of building a heat sink, covering thousands of cubic meters of soil at a considerable depth, will most likely make this solution absolutely unprofitable economically. A less costly option is to drill several wells at intervals of several meters from each other, as was done in an experimental "active house" near Moscow, but this is not cheap either - everyone who has built a water well at home can independently estimate the costs of creating a geothermal fields from at least a dozen 30-meter wells. In addition, constant heat extraction, although less strong than in the case of a compact heat exchanger, will still lower the ground temperature around the heat sinks compared to the original one. This will lead to a decrease in the efficiency of the heat pump during its long-term operation, and the period of temperature stabilization at a new level may take several years, during which the conditions for heat extraction will worsen. However, one can try to partially compensate for the winter heat loss by its enhanced pumping to a depth in the summer heat. But even without taking into account the additional energy consumption for this procedure, the benefit from it will not be too great - the heat capacity of a ground heat accumulator of reasonable size is quite limited, and it is clearly not enough for the entire Russian winter, although such a heat supply is still better than nothing. In addition, the level, volume and speed of groundwater flow is of great importance here - abundantly moistened soil with a sufficiently high water flow rate will not allow making "reserves for the winter" - the flowing water will carry away the pumped heat with it (even a scanty movement of groundwater by 1 meter per day in just a week will carry the stored heat to the side by 7 meters, and it will be outside the working area of \u200b\u200bthe heat exchanger). True, the same groundwater flow will reduce the degree of soil cooling in winter - new portions of water will bring new heat received by them far from the heat exchanger. Therefore, if there is a deep lake nearby, a large pond or a river that never freezes to the bottom, then it is better not to dig the soil, but to place a relatively compact heat exchanger in the reservoir - unlike motionless soil, even in a stagnant pond or lake, convection of free water can provide much more efficient supply of heat to the heat sink from a significant volume of the reservoir. But here it is necessary to make sure that the heat exchanger under no circumstances will be overcooled to the freezing point of water and will not begin to freeze the ice, since the difference between convection heat transfer in water and the heat transfer of an ice coat is enormous (at the same time, the thermal conductivity of frozen and unfrozen soil often does not differ so much strongly, and an attempt to use the enormous heat of crystallization of water in ground heat extraction under certain conditions can justify itself).

The principle of operation of a geothermal heat pump based on the collection of heat from soil or water, and transfer to the heating system of the building. To collect heat, an anti-freeze liquid flows through a pipe located in the soil or water body near the building to the heat pump. A heat pump, like a refrigerator, cools the liquid (removes heat), while the liquid is cooled by about 5 ° C. The liquid flows again through the pipe in the external soil or water, regains its temperature, and again flows to the heat pump. The heat taken away by the heat pump is transferred to the heating system and / or for heating hot water.

It is possible to extract heat from underground water - underground water with a temperature of about 10 ° C is supplied from the well to a heat pump, which cools the water to +1 ... + 2 ° C and returns the water underground. Any object with a temperature higher than minus two hundred seventy three degrees Celsius - the so-called "absolute zero", has thermal energy.

That is, a heat pump can remove heat from any object - earth, water, ice, rock, etc. If the building, for example, in the summer, needs to be cooled (conditioned), then the opposite process occurs - heat is taken from the building and discharged into the ground (water body). The same heat pump can work in winter for heating, and in summer for cooling the building. Obviously, a heat pump can heat water for domestic hot water supply, air conditioning through fan coil units, heat a pool, cool, for example an ice rink, heat roofs and ice paths ...
One equipment can perform all the functions of heating and cooling a building.

The situation is such that the most popular way to heat a home at the moment is to use heating boilers - gas, solid fuel, diesel and much less often - electric. But such simple and at the same time high-tech systems like heat pumps have not received widespread distribution, and in vain. For those who love and know how to calculate everything in advance, their advantages are obvious. Heat pumps for heating do not burn irreplaceable reserves of natural resources, which is extremely important not only from the point of view of environmental protection, but also saves on energy resources, as they become more expensive every year. In addition, with the help of heat pumps, you can not only heat the room, but also heat up hot water for household needs, and condition the room in the summer heat.

How the heat pump works

Let us dwell in a little more detail on the principle of operation of a heat pump. Remember how the refrigerator works. The heat of the products placed in it is pumped out and discharged to the radiator located on the rear wall. It is easy to verify this by touching it. Household air conditioners have a similar principle: they pump heat out of the room and throw it out onto a radiator located on the outer wall of the building.

The operation of a heat pump, refrigerator and air conditioner is based on the Carnot cycle.

1. The coolant, moving along a source of low-temperature heat, for example, the ground, heats up by several degrees.
2. It then enters a heat exchanger called an evaporator. In the evaporator, the coolant transfers the accumulated heat to the refrigerant. Refrigerant is a special liquid that turns into steam at low temperatures.
3. Having taken over the temperature from the coolant, the heated refrigerant turns into steam and enters the compressor. The refrigerant is compressed in the compressor, i.e. an increase in its pressure, due to which its temperature also rises.
4. The hot compressed refrigerant enters another heat exchanger called a condenser. Here the refrigerant gives off its heat to another heat carrier, which is provided in the home heating system (water, antifreeze, air). This cools the refrigerant and turns it back into liquid.
5. Further, the refrigerant enters the evaporator, where it is heated by a new portion of the heated heat carrier, and the cycle is repeated.

The heat pump requires electricity to operate. But this is still much more profitable than using only an electric heater. Since an electric boiler or electric heater consumes exactly the same amount of electricity as it gives out heat. For example, if a power of 2 kW is written on the heater, then it spends 2 kW per hour and produces 2 kW of heat. A heat pump produces 3 - 7 times more heat than it consumes electricity. For example, 5.5 kW / h is used to operate the compressor and pump, and 17 kW / h of heat is obtained. It is this high efficiency that is the main advantage of the heat pump.

Advantages and disadvantages of the "heat pump" heating system

There are many legends and misconceptions around heat pumps, despite the fact that it is not such an innovative and high-tech invention. With the help of heat pumps, all "warm" states in the USA, practically all of Europe and Japan, where the technology has been worked out almost to the ideal and for a long time, are heated. By the way, do not think that such equipment is a purely foreign technology and came to us quite recently. Indeed, even in the USSR, such units were used at experimental facilities. An example of this is the Druzhba sanatorium in the city of Yalta. In addition to the futuristic architecture, reminiscent of a "hut on chicken legs", this sanatorium is also famous for the fact that since the 80s of the 20th century it has been using industrial heat pumps for heating. The source of heat is the nearby sea, and the pumping station itself not only heats all the premises of the sanatorium, but also provides hot water, heats the water in the pool and cools it down during a hot period. So let's try to dispel myths and determine whether it makes sense to heat a home in this way.

Benefits of heat pump heating systems:

• Energy savings.In connection with the rising prices for gas and diesel fuel, a very relevant advantage. In the column "monthly expenses" only electricity will be listed, which, as we have already written, needs much less than actually produced heat. When buying a unit, it is necessary to pay attention to such a parameter as the heat transformation coefficient "ϕ" (it can also be called the heat conversion coefficient, the power or temperature transformation coefficient). It shows the ratio of the amount of heat output to the energy expended. For example, if ϕ \u003d 4, then at a consumption of 1 kW / h we will get 4 kW / h of thermal energy.
• Maintenance savings... The heat pump does not require any special treatment. Maintenance costs are minimal.
• Can be installed in any location... The sources of low-temperature heat for the operation of the heat pump can be soil, water or air. Wherever you build a house, even in rocky terrain, there is always an opportunity to find "food" for the unit. In an area remote from the gas main, this is one of the most optimal heating systems. And even in regions without power lines, a gasoline or diesel engine can be installed to keep the compressor running.
• No need to monitor pump operation, add fuel, as is the case with a solid fuel or diesel boiler. The entire heat pump heating system is automated.
• You can leave for a long time and not be afraid that the system will freeze. At the same time, you can save money by installing a pump to provide a temperature of + 10 ° C in the living room.
• Safe for the environment. For comparison, when using traditional boilers that burn fuel, various oxides of CO, CO2, NOx, SO2, PbO2 are always formed, as a result, phosphoric, nitrous, sulfuric acids and benzoic compounds are deposited on the soil around the house. When the heat pump is running, nothing is emitted. And the refrigerants used in the system are absolutely safe.
• Here you can also note preservation of irreplaceable natural resources of the planet.
• Safety for people and property... In a heat pump, nothing gets hot enough to cause overheating or explosion. In addition, there is simply nothing to explode in it. So it can be classified as a completely fireproof unit.
• Heat pumps work successfully even at an ambient temperature of -15 ° C... So if it seems to someone that such a system can only heat a house in regions with warm winters up to +5 ° C, then they are wrong.
• Heat pump reversibility... An indisputable advantage is the versatility of the unit, with the help of which it is possible to heat both in winter and cool in summer. On hot days, the heat pump takes heat from the room and directs it into the ground for storage, from where it will take it again in winter. Please note that not all heat pumps are reversible, only some models.
• Durability... With proper care, heat pumps of a heating system can live from 25 to 50 years without major repairs, and only once every 15 to 20 years it will be necessary to replace the compressor.

Disadvantages of heat pump heating systems:

• Large initial investment. In addition to the fact that the prices for heat pumps for heating are quite high (from 3,000 to 10,000 cu), in addition to the arrangement of a geothermal system, you will need to spend no less than the pump itself. An exception is the air heat pump, which does not require additional work. The heat pump will not pay off soon (in 5 - 10 years). So the answer to the question, whether or not to use a heat pump for heating, rather depends on the preferences of the owner, his financial capabilities and construction conditions. For example, in a region where the supply of a gas main and connection to it costs the same as a heat pump, it makes sense to give preference to the latter.

• In regions where the temperature in winter drops below -15 ° C, it is necessary to use an additional heat source... It is called bivalent heating system, in which the heat pump provides heat while outdoors down to -20 ° C, and when it fails, for example, an electric heater or gas boiler, or a heat generator is connected.

• It is most advisable to use a heat pump in systems with a low-temperature heat carrier, such as underfloor heating system (+35 ° C) and fan coil units (+35 - +45 ° C). Fan coil unitsare a fan convector in which heat / cold is transferred from water to air. To equip such a system in an old house will require a complete redevelopment and reconstruction, which will entail additional costs. This is not a disadvantage when building a new home.
• Environmentally friendly heat pumpstaking heat from water and soil, somewhat relative. The fact is that in the process of work, the space around the pipes with the coolant cools, and this violates the established ecosystem. Indeed, even in the depths of the soil, anaerobic microorganisms live, providing the vital activity of more complex systems. On the other hand, compared to oil or gas production, the damage from a heat pump is minimal.

Heat sources for heat pump operation

Heat pumps take heat from natural sources that accumulate solar radiation during the warm season. Heat pumps also differ depending on the heat source.

Priming

The ground is the most stable source of heat that accumulates over the season. At a depth of 5 - 7 m, the soil temperature is almost always constant and is approximately +5 - + 8 ° С, and at a depth of 10 m, it is always constant + 10 ° С. There are two ways to collect heat from the ground.

Horizontal soil collector is a horizontally laid pipe through which the coolant circulates. The depth of the horizontal collector is calculated individually depending on the conditions, sometimes it is 1.5 - 1.7 m - the depth of soil freezing, sometimes lower - 2 - 3 m to ensure greater temperature stability and less difference, and sometimes only 1 - 1.2 m - here the soil begins to warm up faster in spring. There are times when a two-layer horizontal collector is equipped.

The horizontal manifold pipes are available in different diameters of 25 mm, 32 mm and 40 mm. The shape of their layout can also be different - snake, loop, zigzag, various spirals. The distance between the pipes in the snake must be at least 0.6 m, and usually 0.8 - 1 m.

Specific heat removal from each running meter of the pipe depends on the structure of the soil:

• Dry sand - 10 W / m;
• Dry clay - 20 W / m;
• Clay is more wet - 25 W / m;
• Clay with a very high water content - 35 W / m.

To heat a house with an area of \u200b\u200b100 m2, provided that the soil is wet clay, you will need 400 m2 of land for the collector. This is quite a lot - 4 - 5 ares. And given the fact that on this site there should be no buildings and only lawn and flower beds with annual flowers are allowed, then not everyone can afford to equip a horizontal collector.

A special liquid flows through the pipes of the collector, it is also called "brine" or antifreezeeg a 30% solution of ethylene glycol or propylene glycol. The "brine" collects the heat of the ground and is directed to the heat pump, where it transfers it to the refrigerant. The cooled “brine” flows back into the ground collector.

Vertical ground probe is a system of pipes buried 50 - 150 m. It can be just one U-shaped pipe, lowered to a great depth of 80 - 100 m and filled with concrete. Or maybe a system of U-shaped pipes lowered 20 m to collect energy from a larger area. Drilling to a depth of 100 - 150 m is not only expensive, but also requires a special permit, which is why they often go for a trick and equip several shallow probes. The distance between such probes is 5 - 7 m.

Specific heat removal from a vertical collector also depends on the rock:

• Dry sedimentary rocks - 20 W / m;
• Sedimentary rocks saturated with water and stony soil - 50 W / m;
• Stony soil with a high thermal conductivity coefficient - 70 W / m;
• Underground (crimp) waters - 80 W / m.

The area for a vertical collector is very small, but the cost of their arrangement is higher than that of a horizontal collector. The advantage of the vertical collector is also a more stable temperature and greater heat output.

Water

There are many ways to use water as a heat source.

Collector at the bottom of an open non-freezing reservoir - rivers, lakes, seas - represents pipes with "brine", submerged with the help of cargo. Due to the high temperature of the coolant, this method is the most profitable and economical. Only those from whom the reservoir is located no further than 50 m can equip the water collector, otherwise the efficiency of the installation will be lost. As you understand, not everyone has such conditions. But not using heat pumps for coastal residents is just shortsighted and stupid.

Sewer collector or waste water after technical installations can be used for heating houses and even high-rise buildings and industrial enterprises within the city, as well as for preparing hot water. What is being successfully done in some cities of our Motherland.

Borehole or ground water used less frequently than other collectors. Such a system implies the construction of two wells, from one water is taken, which transfers its heat to the refrigerant in the heat pump, and cooled water is discharged into the second. Instead of a well, there can be a filtration well. In any case, the discharge well should be located at a distance of 15 - 20 m from the first one, and even downstream (groundwater also has its own course). This system is rather difficult to operate, since the quality of the supplied water must be monitored - filtered, and the parts of the heat pump (evaporator) must be protected from corrosion and pollution.

Air

The simplest design is air source heat pump heating system... No additional manifold is needed. Air from the environment goes directly to the evaporator, where it transfers its heat to the coolant, which in turn transfers heat to the coolant inside the house. It can be air for fan coil units or water for underfloor heating and radiator.

The cost of installing an air heat pump is the lowest, but the performance of the installation is very dependent on the air temperature. In regions with warm winters (up to +5 - 0 ° С) it is one of the most economical heat sources. But if the air temperature drops below -15 ° C, the performance drops so much that it makes no sense to use a pump, but it is more profitable to turn on a conventional electric heater or boiler.

Reviews of air heat pumps for heating are very controversial. It all depends on the region of their use. It is beneficial to use them in regions with warm winters, for example, in Sochi, where a duplicate heat source is not even needed in case of severe frosts. It is also possible to install air source heat pumps in regions where the air is relatively dry and the winter temperature is down to -15 ° C. But in humid and cold climates, such installations suffer from icing and freezing. Icicles sticking to the fan prevent the entire system from working normally.

Heat pump heating: system cost and operating costs

The power of the heat pump is selected depending on the functions that will be assigned to it. If only heating, then calculations can be made in a special calculator that takes into account the heat losses of the building. By the way, the best performance of a heat pump with a building heat loss of no more than 80 - 100 W / m2. For simplicity, we will assume that a 10 kW pump is needed to heat a 100 m2 house with 3 m high ceilings and a heat loss of 60 W / m2. To heat water, you will have to take a unit with a power reserve of 12 or 16 kW.

Heat pump cost depends not only on the power, but also on the reliability and the manufacturer's requests. For example, a Russian-made 16 kW unit will cost $ 7,000, while a 17 kW foreign pump RFM 17 costs about $ 13,200. with all related equipment, except for the collector.

The next line of expenses will be collector arrangement... It also depends on the capacity of the installation. For example, for a house of 100 m2, in which underfloor heating (100 m2) or heating radiators of 80 m2 are installed everywhere, as well as for heating water to +40 ° C with a volume of 150 l / h, it will be necessary to drill wells for collectors. Such a vertical collector will cost $ 13,000.

A collector at the bottom of the reservoir will cost a little less. Under the same conditions, it will cost $ 11,000. But it is better to clarify the cost of installing a geothermal system in specialized companies, it can be very different. For example, the arrangement of a horizontal collector for a pump with a power of 17 kW will cost only 2500 USD. And for an air heat pump, a collector is not needed at all.

Total, the cost of the heat pump is 8000 USD. on average, the arrangement of the collector is 6000 USD. average.

The monthly cost of heating with a heat pump includes only electricity costs... You can calculate them like this - the power consumption must be indicated on the pump. For example, for the aforementioned 17 kW pump, the power consumption is 5.5 kW / h. In total, the heating system operates 225 days a year, i.e. 5400 hours. Taking into account the fact that the heat pump and the compressor in it work cyclically, the power consumption must be halved. During the heating season, 5400 h * 5.5 kW / h / 2 \u003d 14850 kW will be spent.

We multiply the number of kWh spent by the cost of the energy carrier in your region. For example, 0.05 c.u. for 1 kW / hour. In total, 742.5 USD will be spent for the year. For each month, in which the heat pump worked for heating, there are $ 100. electricity costs. If we divide the expenses by 12 months, then we will get 60 USD per month.

Please note that the lower the power consumption of the heat pump, the lower the monthly costs. For example, there are 17 kW pumps, which consume only 10,000 kW per year (costs $ 500). It is also important that the performance of a heat pump is greater, the smaller the temperature difference between the heat source and the coolant in the heating system. That is why they say that it is more profitable to install underfloor heating and fan coil units. Although standard heating radiators with a high-temperature heat carrier (+65 - +95 ° C) can also be installed, but with an additional heat accumulator, for example, an indirect heating boiler. A boiler is also used to reheat hot water.

Heat pumps are beneficial when used in bivalent systems. In addition to the pump, a solar collector can be installed, which will be able to fully provide the pump with electricity in the summer, when it will work for cooling. For winter security, you can add a heat generator, which will heat up the water for hot water supply and high-temperature radiators.

A heat pump is a device that transfers heat energy from a less heated body to a more heated body, increasing its temperature. In recent years, heat pumps have been in high demand as a source of alternative heat energy, which allows you to get really cheap heatwithout polluting the environment.

Today they are produced by many manufacturers of heating equipment, and the general trend is that in the coming years it is heat pumps that will take the leading positions in the range of heating equipment.

Typically, heat pumps use warmth of groundwater, the temperature of which is at approximately the same level all year round and is + 10C, the heat of the environment or water bodies.

The principle of their operation is based on the fact that any body with a temperature higher than the value of absolute zero has a reserve of thermal energy, which is directly proportional to its mass and specific heat capacity. It is clear that the seas, oceans, as well as underground waters, the mass of which is large, have a tremendous supply of thermal energy, the partial use of which for heating a home does not in any way affect their temperature and the ecological situation on the planet.

"Take away" heat energy from any body can only be cooled. The amount of heat released during this (in a primitive form) can be calculated by the formula

Q \u003d CM (T2-T1) where

Q- received heat

C -heat capacity

M - weight

T1 T2 - the temperature difference by which the body was cooled

The formula shows that when one kilogram of the coolant is cooled from 1000 degrees to 0 degrees, the same amount of heat can be obtained as when 1000 kg of the coolant is cooled from 1C to 0C.

The main thing is to be able to use thermal energy and direct it to heating residential buildings and industrial premises.

The idea of \u200b\u200busing the thermal energy of less heated bodies arose in the middle of the 19th century, and its authorship belongs to the famous scientist of that time, Lord Kelvin. However, his business did not progress further than the general idea. The first heat pump project was proposed in 1855 and belonged to Peter Ritter for Rittenger. But he did not receive support and found no practical application.

The “rebirth” of the heat pump dates back to the mid-forties of the last century, when ordinary household refrigerators became widespread. It was they who pushed the Swiss Robert Weber to the idea of \u200b\u200busing the heat generated by the freezer to heat water for household needs.

The resulting effect was overwhelming: the amount of heat was so great that it was enough not only for hot water supply, but also for heating water for heating. True, at the same time it was necessary to work hard and come up with a system of heat exchangers that allows you to utilize the thermal energy released by the refrigerator.

However, in the beginning, Robert Weber's invention was seen as a funny idea, and was perceived like ideas from the modern famous column "Crazy Hands". Real interest in it arose much later, when the question of finding alternative energy sources was really acute. It was then that the idea of \u200b\u200ba heat pump got its modern shape and practical application.

Modern heat pumps can be classified according to the source of low-temperature heat, which can be soil, water (in an open or underground reservoir), and outside air.

The resulting thermal energy can be transferred to water and used for hot water heating and hot water supply, as well as air, and used for heating and air conditioning. With this in mind, heat pumps are divided into 6 types:

• From soil to water (soil to water)
• From soil to air (soil to air)
• From water to water (water to water)
• From water to air (water to air)
• Air to water (air to water)
• Air to air (air to air)

Each type of heat pump has its own characteristic installation and operation features.

Installation method and features of operation of the heat pump GROUND-WATER

• Soil one-stop supplier of low temperature thermal energy

The soil has a colossal reserve of low-temperature thermal energy. It is the earth's crust that constantly accumulates solar heat and at the same time is heated from the inside, from the core of the planet. As a result, at a depth of several meters, the soil always has a positive temperature. As a rule, in the central part of Russia we are talking about 150-170 cm.It is at this depth that the soil temperature has a positive value and does not fall below 7-8 C.

Another feature of the soil is that, even in severe frosts, it freezes gradually. As a result, the minimum soil temperature at a depth of 150 cm is observed when the calendar spring is already on the surface and the demand for heat for heating decreases.

This means that in order to "take away" heat from the ground in the central region of Russia, heat exchangers for accumulating heat energy must be located at a depth below 150 cm.

In this case, the coolant circulating in the heat pump system, passing through the heat exchangers, will be heated due to the heat of the ground, then, entering the evaporator, transfer heat to the water circulating in the heating system and return for a new portion of thermal energy.

• What can be used as a coolant

The so-called "brine" is most often used as a heat carrier in ground-water heat pumps. It is prepared from water and ethylene glycol or propylene glycol. Some systems use freon, which greatly complicates the design of the heat pump and leads to an increase in its cost. The fact is that the heat exchanger of this type of pump must have a large heat exchange area, therefore, and the internal volume, which requires an appropriate amount of heat carrier.

Freon use although it increases the efficiency of the heat pump, it requires absolute tightness of the system and its resistance to high pressure.

For systems with "brine" heat exchangers are usually made of polymer pipes, most often polyethylene, with a diameter of 40-60mm. Heat exchangers are designed as horizontal or vertical collectors.

It is a pipe laid in the ground at a depth below 170 cm. You can use any undeveloped piece of land for this. For convenience and to increase the heat exchange area, the pipe is laid in a zigzag, loops, spiral, etc. In the future, this piece of land can be used as a lawn, flower bed or vegetable garden. It should be noted that heat transfer between the soil and the collector is better in a humid environment. Therefore, the surface of the soil can be safely watered and fertilized.

It is believed that an average of 1 m2 of soil gives from 10 to 40 watts of thermal energy. Depending on the need for heat energy, there can be any number of collector loops.

A vertical collector is a system of pipes installed vertically in the ground. For this, wells are drilled to a depth of several meters to tens, or even hundreds of meters. Most often, the vertical collector is in close contact with groundwater, but this is not necessary condition for its operation. That is, a vertically installed underground reservoir can be "dry".

The vertical collector, just like the horizontal one, can be of almost any design. The most widespread systems are the "pipe-in-pipe" and "loop" systems, through which the brine is pumped down and rises back to the evaporator.

It should be noted that vertical collectors are the most productive. This is explained by their location at great depths, where the temperature is almost always at the same level and is 1-12 C. When using them from 1 m2, you can get from 30 to 100 watts of power. If necessary, the number of wells can be increased.

To improve the process of heat transfer between the pipe and the ground, the space between them is poured with concrete.

• Advantages and disadvantages of ground-to-water heat pumps

Installation of a ground-to-water heat pump requires significant financial investments, but its operation allows you to get almost free heat energy. This does not cause any damage to the environment.

Among the advantages of this type of heat pump should be noted:

• Durable: can operate for decades in a row without repair and maintenance
• Ease of operation
• Possibility of using a plot of land for farming
• Fast payback: when heating premises of a large area, for example, from 300 m2 and more, the pump pays for itself in 3-5 years.

Considering that the installation of a heat exchanger in the ground is a complex agrotechnical work, they must be performed with a preliminary development of the project.

How a heat pump works

The heat pump consists of the following elements:

• Compressor powered by a conventional electrical network
• Evaporator
• Capacitor
• Capillary
• Thermostat
• Working fluid or refrigerant, the role of which freon is most suitable

The principle of operation of a heat pump can be described using the well-known from school course physics "Carnot Cycle".

The gas (freon) entering the evaporator through the capillary expands, its pressure decreases, which leads to its subsequent evaporation, in which it, in contact with the walls of the evaporator, actively removes heat from them. The temperature of the walls decreases, which creates a temperature difference between them and the mass in which the heat pump is located. Typically, these are groundwater, sea water, lake or land mass. It is not difficult to guess that in this case the process of transfer of thermal energy from a more heated body to a less heated body begins, which in this case are the walls of the evaporator. At this stage of operation, the heat pump “pumps out” heat from the heat carrier medium.

In the next step, the refrigerant is sucked in by the compressor, then compressed and pressurized into the condenser. In the process of compression, its temperature rises and can range from 80 to 120 C, which is more than enough for heating and hot water supply of a residential building. In the condenser, the refrigerant gives up its reserve of thermal energy, cools down, turns into a liquid state, and then enters the capillary. Then the process is repeated.

To control the operation of the heat pump, a thermostat is used, with the help of which the supply of electricity to the system is stopped when the room reaches the set temperature and the pump resumes when the temperature drops below a predetermined value.

The heat pump can be used as a source of heat energy and can be combined with heating systems similar to heating systems based on a boiler or stove. An example of such a system is shown in the diagram above.

It should be noted that the operation of the heat pump is possible only when connected to a source of electrical energy. At the same time, an opinion may arise that the entire heating system is based on the use of electrical energy. In fact, to transfer 1 kW of thermal energy to the heating system, it is necessary to spend approximately 0.2-0.3 kW of electrical energy.

Heat pump advantages

Among the advantages of a heat pump are:

• High efficiency
• The ability to switch from heating mode to air conditioning mode and its subsequent use in the summer to cool the premises
• Possibility to use an efficient automatic control system
• Environmental safety
• Compactness (no more than a household refrigerator)
• Quiet operation
• Fire safety, which is especially important for heating country houses

Among the disadvantages of a heat pump, it should be noted high cost and complexity of installation.

Article outline

A heat pump is a device that heats water from heating and hot water supply systems by compressing freon, initially heated from a low-grade heat source, with a compressor to 28 bar. Being exposed to high pressure, the gaseous heat carrier with an initial temperature of 5-10 ° C; generates a lot of heat. This allows heating the coolant of the consumption system up to 50-60 ° C, without using traditional fuels. Therefore, the heat pump is considered to provide the user with the cheapest heat.

For more details on the advantages and disadvantages, see the video:

Such equipment has been in operation for more than 40 years in Sweden, Denmark, Finland and other countries that support the development of alternative energy at the state level. Not so actively, but more confidently every year, heat pumps enter the Russian market.

Purpose of the article:review popular heat pump models. The information will be useful to those who seek to save as much as possible on heating and hot water supply for their own home.

The heat pump heats the house with the free energy of nature

In theory, heat extraction is possible from air, soil, groundwater, wastewater (including from a septic tank and sewage pumping station), open reservoirs. In practice, in most cases the expediency of using equipment that collects heat energy from air and soil has been proven.

Options with heat extraction from a septic tank or a sewage pumping station (SPS) are the most tempting. By driving a coolant from 15-20 ° C through the HP, at least 70 ° C can be obtained at the outlet. But this option is acceptable only for a hot water supply system. The heating circuit reduces the temperature in the "tempting" source. Which leads to a number of unpleasant consequences. For example, freezing of drains; and if the heat exchange circuit of the heat pump is located on the walls of the sump, then the septic tank itself.

The most popular heat pumps for the needs of CO and hot water supply are geothermal (using the heat of the earth) devices. They stand out for their best performance in warm and cold climates, in sandy and clayey soil with different groundwater levels. Because the temperature of the soil below the freezing depth remains almost unchanged throughout the year.

How the heat pump works

The heat carrier is heated from a low-grade (5 ... 10 ° C) heat source. The pump compresses the refrigerant, the temperature of which rises at the same time (50 ... 60 ° C) and heats the heat carrier of the heating system or hot water supply.

In the process of HP operation, three heating circuits are involved:

• outdoor (system with coolant and circulation pump);
• intermediate (heat exchanger, compressor, condenser, evaporator, throttle valve);
• consumer circuit (circulation pump, underfloor heating, radiators; for hot water supply - tank, draw-off points).

The process itself looks like this:

Heat recovery circuit

1. The soil heats up the brine.
2. The circulation pump lifts the brine into the heat exchanger.
3. The solution is cooled with a refrigerant (freon) and returned to the ground.

Heat exchanger

1. Liquid freon evaporates and takes heat energy from the brine.
2. The compressor compresses the refrigerant and its temperature rises sharply.
3. In the condenser, freon, through the evaporator, gives off energy to the heat carrier of the heating circuit and becomes liquid again.
4. The cooled refrigerant flows through the throttle valve to the first heat exchanger.

Heating circuit

1. The heated heat carrier of the heating system is drawn by the circulation pump to the dissipative elements.
2. Gives thermal energy to the air mass of the room.
3. The cooled coolant is returned through the return pipe to the intermediate heat exchanger.

Video from detailed description process:

Which is cheaper for heating: electricity, gas or a heat pump?

Here are the costs of connecting each type of heating. Let's take the Moscow region to present the big picture. In regions, prices may differ, but the price ratio will remain the same. In the calculations, we assume that the site is "bare" - without gas and electricity.

Connection costs

Heat pump.Laying a horizontal contour at MO prices - 10,000 rubles for changing an excavator with a still bucket (selects up to 1,000 m³ of soil in 8 hours). The system for a house of 100 m² will be dug in 2 days (this is true for loam, on which up to 30 W of heat energy can be removed from 1 lm of the circuit). About 5,000 rubles will be required to prepare the circuit for work. As a result, the horizontal option of placing the primary circuit will cost 25,000.

The well will come out more expensive (1,000 rubles per running meter, taking into account the installation of probes, piping them into one line, refueling with coolant and pressure testing.), But much more profitable for future operation. With a smaller occupied area of \u200b\u200bthe site, the return increases (for a well of 50 m - at least 50 W per meter). The needs of the pump are covered, additional potential appears. Therefore, the whole system will not work for wear and tear, but with some power reserve. Place 350 meters of the contour in vertical wells - 350,000 rubles.

Gas boiler. In the Moscow region, Mosoblgaz requests from 260,000 rubles for connection to the gas network, work on the site and installation of the boiler.

Electric boiler. Connecting a three-phase network will cost 10,000 rubles: 550 - for local power grids, the rest - for the switchboard, meter and other filling.

Consumption

To operate a heat pump with a thermal power of 9 kW, 2.7 kW / h of electricity is required - 9 rubles. 53 kopecks in hour,

Specific heat during combustion of 1 m³ of gas is the same 9 kW. Household gas for the Moscow region is set at 5 rubles. 14 kopecks per cubic meter

The electric boiler consumes 9 kW / h \u003d 31 rubles. 77 kopecks in hour. The difference with TN is almost 3.5 times.

Exploitation

• If gas is supplied, then the most cost-effective option for heating is a gas boiler. The equipment (9 kW) costs at least 26,000 rubles, the monthly payment for gas (12 hours per day) will be 1,850 rubles.
• Powerful electrical equipment is more profitable from the point of view of organizing a three-phase network and purchasing the equipment itself (boilers - from 10,000 rubles). A warm house will cost 11 437 rubles per month.
• Taking into account the initial investment in alternative heating (equipment 275,000 and installation of a horizontal circuit 25,000), a heat pump that consumes electricity by 3,430 rubles / month will pay off no earlier than in 3 years.

Comparing all heating options, provided that a system is created from scratch, it becomes obvious: gas will not be much more profitable than a geothermal heat pump, and heating with electricity in the future 3 years hopelessly loses to both of these options.

Detailed calculations in favor of operating a heat pump can be found by watching a video from the manufacturer:

Some additions and experience of effective operation are highlighted in this video:

Main characteristics

When choosing equipment from the whole variety of characteristics, pay attention to the following characteristics.

The main characteristics of heat pumps

Characteristics	Range of values	Features:
Thermal power, kW	Up to 8	Premises with an area of \u200b\u200bno more than 80 - 100 m², with a ceiling height of no more than 3 m.
	8-25	For single-level country houses with a ceiling of 2.5 m, an area of \u200b\u200b50 m²; cottages for permanent residence, up to 260 m².
	Over 25	It is advisable to consider for 2-3 level residential buildings with 2.7m ceilings; industrial facilities - no more than 150 m², with a ceiling height of 3 or more.
Power consumption of the main equipment (limiting consumption of auxiliary elements) kW / h	From 2 (from 6)	It characterizes the energy consumption of the compressor and circulation pumps (heating element).
Scheme of work	Air to air	The transformed thermal energy of the air is transferred to the room by a stream of heated air through the split system.
	Air - water	The energy taken from the air passed through the device is transferred to the coolant of the liquid heating system.
	Brine-water	The transfer of thermal energy from a renewable source is performed by a sodium or calcium solution.
	Water-water	Through the main line of the open primary circuit, groundwater carries heat energy directly to the heat exchanger.
Coolant outlet temperature, ° С	55-70	The indicator is important for calculating losses on a long heating circuit and when organizing an additional hot heating system.
Mains voltage, V	220, 380	Single-phase - power consumption no more than 5.5 kW, only for a stable (lightly loaded) household network; the cheapest - only through the stabilizer. If there is a 380 V network, then three-phase devices are preferable - a larger range of powers, less likely to "sink" the network.

Summary table of models

In the article, we examined the most popular models, identified their strengths and weaknesses. The list of models can be found in the following table:

Summary table of models

Model (country of origin)	Features:	price, rub.
Heat pumps for heating small rooms or for hot water supply
1.	Air-water system; works from a single-phase network; the protruding condensation line is inserted into the water tank.	184 493
2.	"Brine-water"; power supply from a three-phase network; variable power control; the ability to connect additional equipment - recuperator, multi-temperature equipment.	355 161
3.	An air-to-water heat pump powered by a 220V network and an anti-freeze function.	524 640
Equipment for heating systems of cottages for permanent residence
4.	The scheme "water - water". In order for the heat pump to be able to deliver a stable 62 ° C of the coolant in the heating system, the capabilities of a set of a compressor and pumps (1.5 kW) are complemented by an electric heater with a power of 6 kW.	408 219
5.	On the basis of the "air-water" circuit, in one device, consisting of two blocks, the potentials of the cooling and heating devices are realized.	275 000
6.	"Brine-water", the device heats up the heat carrier for radiators up to 60 ° C, can be used in the organization of cascade heating systems.	323 300
7.	A storage tank for a hot water supply system for 180 liters of coolant is located in one housing with a geothermal pump	1 607 830
Powerful heat pumps for heating and hot water supply
8.	Extraction of heat from soil and groundwater is possible; operation as part of cascade systems and remote control are possible; works from a three-phase network.	708 521
9.	Brine-water; compressor power and circulation pump speed control is carried out by means of frequency regulation; additional heat exchanger; network - 380 V.	1 180 453
10.	the scheme of work "water-water"; built-in pumps of the primary and secondary circuit; the possibility of connecting solar systems is provided.	630 125

Heat pumps for heating small rooms or for hot water supply

Purpose - economical heating of residential and auxiliary premises, maintenance of the hot water supply system. The lowest consumption (up to 2 kW) is allocated to single-phase models. To protect against voltage surges in the network, they need a stabilizer. The reliability of three-phase, is explained by the peculiarities of the network (the load is distributed evenly) and the presence of its own protective circuits that prevent damage to the device during voltage surges. Equipment in this category does not always cope with the simultaneous maintenance of the heating system and the hot water circuit.

1. Huch EnTEC VARIO PRC S2-E (Germany) - from 184 493 rubles.

Huch EnTEC VARIO cannot be operated independently. Only in conjunction with the storage tank of the hot water supply system. TH heats water for sanitary needs, cooling the air in the room.

Among the advantages are low power consumption of the device, acceptable water temperature in the DHW circuit and the function of cleaning the system (by periodic short-term heating up to 60 ° C) from pathogenic bacteria developing in a humid environment.

The disadvantages are that gaskets, flanges and a collar must be purchased separately. Be sure to original, otherwise there will be streaks.

When calculating, it must be remembered that the device pumps 500 m³ of air per hour, therefore, the minimum area of \u200b\u200bthe room in which Huch EnTEC VARIO is installed must be at least 20 m², with a ceiling height of 3 meters or more.

2. NIBE F1155-6 EXP (Sweden) - from 355 161 rubles.

The model is declared as "intelligent" equipment, with automatic adjustment to the needs of the facility. An inverter power supply circuit for the compressor has been introduced - it is now possible to adjust the output power.

The presence of such a function with a small number of consumers (draw-off points, heating radiators) makes heating a small house more profitable than in the case of a conventional, non-inverter heat pump (which do not have a soft start of the compressor and the output power is not regulated). Because at NIBE, at low power values, the heating elements are rarely turned on, and the heat pump's own maximum consumption is no more than 2 kW.

Noise (47 dB) is not acceptable in a small object. The best installation option is a separate room. Place the harness on the walls not adjacent to the rest rooms.

3. Fujitsu WSYA100DD6 (Japan) - from 524 640 rubles.

"Out of the box" only works for heating in one circuit. An optional kit for connecting a second circuit is offered, with the possibility of independent adjustment for each. But the heat pump itself is designed for a room heating system up to 100 m², with a ceiling height of no more than 3 meters.

The list of advantages includes small dimensions, operation from a household power supply, regulation of the outlet temperature from 8 to 55 ° C, which, according to the manufacturer, should somehow affect the comfort and accuracy of control of the connected systems.

But all was crossed out by low power. In our climate, heating the declared 100 m², the device will work for wear and tear. This is confirmed by the frequent transitions of the device to the "emergency" mode, with the pump disconnected and errors on the display. The case is not guaranteed. Corrected by restarting the equipment.

"Accidents" affect energy consumption. Because when the compressor stops, the heating element is turned on. Therefore, the joint connection of heating circuits and underfloor heating (or hot water supply) is permissible on an object with an area of \u200b\u200bno more than 70 m².

Equipment for heating systems of typical cottages for permanent residence

Here are geothermal, air and water (removing thermal energy from groundwater) devices. The declared output power (at least 8 kW) is enough to provide heat to all consumer systems of country houses (and permanent residence). Many heat pumps in this category have a cooling mode. The introduced inverter power circuits are responsible for the smooth start of the compressor, due to its smooth operation, the delta (temperature difference) of the coolant decreases. The optimal operating mode of the circuit is maintained (without unnecessary overheating and cooling). That allows to reduce power consumption in all modes of HP operation. The greatest economic effect is in air-to-air devices.

4. Vaillant geoTHERM VWW 61/3 (Germany) - from 408,219 rubles.

The use of water from the well as a primary coolant (only VWW) made it possible to simplify the design and reduce the cost of the HP without losing productivity.

The device features low power consumption in basic operation mode and low noise level.

Minus Vaillant - exactingness to water (known cases of damage to the supply line and heat exchanger with iron and manganese compounds); work with saline waters should be excluded. The situation is not guaranteed, but if the installation was carried out by the specialists of the service center, then there is someone to make a claim.

A dry, frost-free room with a volume of at least 6.1 m³ (2.44 m² with a ceiling of 2.5 m) is required. Droplet formation under the pump is not a defect (condensate drainage from the surfaces of insulated circuits is allowed).

5. LG Therma V AH-W096A0 (Korea) - from 275,000 rubles.

Air-to-water heat pump. The device consists of 2 modules: the external one takes heat energy from the air masses, the internal one transforms and transfers it to the heating system.

The main plus is versatility. Can be configured for both heating and cooling the object.

The disadvantage of this series LG Therma is that its (and the entire line) potential is not enough for the needs of a cottage with an area of \u200b\u200bmore than 200 m².

An important point: the working blocks of a two-component system cannot be spread more than 50 m horizontally and 30 m vertically.

6. STIEBEL ELTRON WPF 10MS (Germany) - from 323 300 rubles.

The WPF 10MS is the most powerful STIEBEL ELTRON heat pump.

Among the advantages are an automatically adjustable heating mode and the ability to connect 6 devices in a cascade (this is a parallel or series connection of devices in order to increase the flow rate, pressure or organize an emergency reserve) system with a capacity of up to 60 kW.

The downside is that the organization of a powerful electrical network for the simultaneous connection of 6 such devices is possible only with the permission of the local department of Rostekhnadzor.

There is a peculiarity in setting the modes: after making the necessary adjustments to the program, you should wait until the control lamp goes out. Otherwise, after closing the cover, the system will return to the original settings.

7. Daikin EGSQH10S18A9W (Japan) - from 1 607 830 rubles.

A powerful device for the simultaneous supply of heat to CO, DHW and underfloor heating of a residential building with an area of \u200b\u200bup to 130 m².

Programmable and user-controlled modes; all serviced circuits are monitored within the specified parameters; there is a built-in storage (for the needs of hot water supply) for 180 liters and auxiliary heaters.

Among the disadvantages - an impressive potential, which will not be fully utilized in the house of 130 m²; the price due to which the payback period is extended indefinitely; automatic adaptation to external climatic conditions not implemented in the basic configuration. Ambient thermistors (thermal resistors) are optional. That is, when the external temperature changes, it is proposed to set the operating mode manually.

Equipment for objects with high heat consumption

To fully meet the needs for thermal energy of residential and commercial buildings with an area of \u200b\u200bmore than 200 m². Remote control, cascade operation, interaction with recuperators and solar systems - expand the user's ability to create a comfortable temperature.

8. WATERKOTTE EcoTouch DS 5027.5 Ai (Germany) - from 708 521 rubles.

The DS 5027.5 Ai modification is the most powerful in the EcoTouch range. Stably heats up the heating agent of the heating circuit and provides heat energy to the DHW system in rooms up to 280 m².

Scroll (the most efficient of the existing) compressor; regulation of the flow rate of the coolant allows you to obtain stable indicators of the outlet temperature; color display; Russified menu; neat appearance and low noise level. Every detail for comfortable operation.

With the active use of the water points, the heating elements are turned on, due to which the energy consumption increases by 6 kW / h.

9. DANFOSS DHP-R ECO 42 (Sweden) - from 1 180 453 rubles.

Powerful enough equipment to provide thermal energy to the hot water supply system and heating circuits of a multi-level cottage with permanent residence.

Instead of an additional heater for domestic hot water, it uses the hot water flow from the heating circuit. Passing hot water through the desuperheater, the heat pump heats the water in the additional DHW heat exchanger to 90 ° C. A stable temperature in the CO and the DHW tank is maintained by automatically adjusting the speed of the circulation pumps. Suitable for cascade connection (up to 8 VT).

There are no heating elements for the heating circuit. Additional resources are taken from any combined boiler - the control unit will take from it as much heat as is required in a particular case.

When calculating the space for mounting the heat pump, it is necessary to leave a gap of 300 mm between the wall and the rear surface of the device (for the convenience of monitoring and maintaining communications).

10. Viessmann Vitocal 300-G WWC 110 (Germany) - from 630 125 rubles.

The primary coolant is groundwater. Hence the constant temperature at the first heat exchanger and the highest COP coefficient.

Among the pluses is an auxiliary electric heater of low power on the primary circuit and a proprietary controller (in fact, a wireless remote control) for remote control.

Minus - the operability of the circulation pump, the state of the main line and the heat exchanger of the primary circuit depends on the quality of the distilled groundwater. Filtering is required.

Groundwater analysis will help to eliminate the appearance of difficult-to-solve problems with expensive equipment. Which should be done before purchasing a water-to-water heat pump.

Editor's Choice

Many years of experience in the production and operation of heat pumps in Northern Europe have allowed our compatriots to reduce the search for the most profitable way to heat their home. Real options exist for any request.

Do you need to provide heat to the DHW circuit or the heating system of a residential building up to 80 - 100 m²? Consider the potential NIBE F1155 - its "intelligent" filling saves without damage to heat supply.

A stable temperature in the underfloor heating circuits, CO, DHW of a cottage of 130 m² will be ensured by a DHW heat exchanger (180 liters).

Provides a constant heat flow for all consumers simultaneously. The possibility of creating a cascade of 8 heat pumps allows providing heat to an object with an area of \u200b\u200bat least 3,000 m2.

Each of these models is not an absolute, but a basic option. If you have found a suitable TN - browse the entire line, explore optional offers. The range of equipment is large, there is a risk of missing your ideal option.

The article helped you find a profitable heating option, or if you need more information - write in the comments. We will respond immediately.

More and more Internet users are interested in heating alternatives: heat pumps.

For the majority, this is a completely new and unknown technology, which is why questions such as: "What is it?", "What does a heat pump look like?", "How does a heat pump work?" etc.

Here we will try to give simple and accessible answers to all these and many other questions related to heat pumps.

What is a Heat Pump?

Heat pump - a device (in other words "heat boiler") that takes the dissipated heat from the environment (soil, water or air) and transfers it to the heating circuit of your house.

Thanks to the sun's rays, which continuously enter the atmosphere and to the surface of the earth, there is a constant release of heat. This is how the surface of the earth receives heat energy all year round.

Air partially absorbs heat from the energy of the sun's rays. The remaining solar thermal energy is almost completely absorbed by the earth.

In addition, geothermal heat from the bowels of the earth constantly provides a soil temperature of + 8 ° C (starting from a depth of 1.5-2 meters and below). Even in cold winters, the temperature at the depth of reservoirs remains in the range of + 4-6 ° С.

It is this low-potential heat of soil, water and air that transfers the heat pump from the environment to the heating circuit of a private house, having previously increased the temperature level of the coolant to the required + 35-80 ° С.

VIDEO: How does the Ground-Water heat pump work?

What Does a Heat Pump Do?

Heat pumps - heat engines, which are designed to produce heat using a reverse thermodynamic cycle. transfer thermal energy from a source with a low temperature to a heating system with a higher temperature. During the operation of the heat pump, energy costs occur that do not exceed the amount of energy produced.

The operation of a heat pump is based on the reverse thermodynamic cycle (reverse Carnot cycle), consisting of two isotherms and two adiabats, but unlike the direct thermodynamic cycle (forward Carnot cycle), the process proceeds in the opposite direction: counterclockwise.

In the reverse Carnot cycle, the environment acts as a cold heat source. During the operation of the heat pump, the heat of the external environment is transferred to the consumer due to the performance of the work, but with a higher temperature.

It is possible to transfer heat from a cold body (soil, water, air) only at the expense of work (in the case of a heat pump, the cost of electrical energy for the operation of a compressor, circulation pumps, etc.) or another compensation process.

A heat pump can also be called a “reverse refrigerator”, since a heat pump is the same refrigerating machine, but unlike a refrigerator, the heat pump takes heat from the outside and transfers it to the room, that is, heats the room (the refrigerator cools by taking heat from the refrigerating chamber and throws it out through the capacitor).

How does a Heat Pump work?

Now talk about how a heat pump works. In order to understand how a heat pump works, we need to understand a few things.

1. The heat pump is capable of extracting heat even at negative temperatures.

Most future homeowners cannot understand the principle of operation (in principle, any air heat pump), since they do not understand how heat can be extracted from the air at negative temperatures in winter. Let's go back to the basics of thermodynamics and remember the definition of heat.

Heat - the form of motion of matter, which is a random movement of particles forming the body (atoms, molecules, electrons, etc.).

Even at 0˚C (zero degrees Celsius) when the water freezes, there is still warmth in the air. It is much less than, for example, at a temperature of + 36˚С, but nevertheless, at zero and negative temperatures, atoms move, and therefore heat is released.

The movement of molecules and atoms completely stops at a temperature of -273˚С (minus two hundred and seventy three degrees Celsius), which corresponds to absolute zero temperature (zero degrees on the Kelvin scale). That is, even in winter, at subzero temperatures, there is low-grade heat in the air, which can be extracted and transferred to the house.

2. Working fluid in heat pumps is a refrigerant (freon).

What is a refrigerant? Refrigerant - a working substance in a heat pump, which takes heat from the cooled object during evaporation and transfers heat to the working medium (for example, water or air) during condensation.

The peculiarity of refrigerants is that they are capable of boiling at both negative and relatively low temperatures. In addition, refrigerants can change from liquid to gas and vice versa. It is during the transition from liquid to gaseous (evaporation) that heat is absorbed, and during the transition from gaseous to liquid (condensation), heat is transferred (heat separation).

3. The operation of a heat pump is possible thanks to its four key components.

In order to understand the principle of operation of a heat pump, its device can be divided into 4 main elements:

1. Compressorwhich compresses the refrigerant to increase its pressure and temperature.
2. Expansion valve - a thermostatic expansion valve that dramatically lowers the pressure of the refrigerant.
3. Evaporator - a heat exchanger in which the low temperature refrigerant absorbs heat from the environment.
4. Capacitor - a heat exchanger, in which the already hot refrigerant after compression transfers heat to the working medium of the heating circuit.

It is these four components that enable chillers to produce cold and heat pumps to produce heat. In order to understand how each component of a heat pump works and why it is needed, we suggest watching a video about the principle of operation of a ground source heat pump.

VIDEO: The principle of operation of the Soil-Water heat pump

How the heat pump works

Now we will try to describe in detail each stage of the heat pump operation. As mentioned earlier, the operation of heat pumps is based on the thermodynamic cycle. This means that the operation of a heat pump consists of several cycle stages, which are repeated over and over again in a specific sequence.

The duty cycle of a heat pump can be divided into the following four stages:

1. Absorption of heat from the environment (refrigerant boiling).

The evaporator (heat exchanger) receives refrigerant, which is in a liquid state and has a low pressure. As we already know, at low temperatures, the refrigerant can boil and evaporate. The evaporation process is necessary for the substance to absorb heat.

According to the second law of thermodynamics, heat is transferred from a body with a high temperature to a body with a lower temperature. It is at this stage of the heat pump operation that the low-temperature refrigerant, passing through the heat exchanger, takes heat from the coolant (brine), which had previously risen from the wells, where it took away low-potential soil heat (in the case of ground-based heat pumps Ground-Water).

The fact is that the temperature of the soil underground at any time of the year is + 7-8 ° C. When used, vertical probes are installed through which the brine (heat carrier) circulates. The task of the coolant is to warm up to the maximum possible temperature while circulating through the deep probes.

When the heat carrier has taken heat from the ground, it enters the heat exchanger of the heat pump (evaporator) where it "meets" the refrigerant, which has a lower temperature. And according to the second law of thermodynamics, heat exchange occurs: heat from a more heated brine is transferred to a less heated refrigerant.

Here's a very important point: heat absorption is possible during evaporation of the substance conversely, the transfer of heat occurs during condensation. During the heating of the coolant from the coolant, it changes its phase state: the coolant passes from a liquid to a gaseous state (the process of boiling of the coolant occurs, it evaporates).

Coming through the evaporator the refrigerant is in the gaseous phase... It is no longer a liquid, but a gas that has taken heat from the coolant (brine).

2. Compression of the refrigerant by the compressor.

In the next stage, the gaseous refrigerant enters the compressor. Here, the compressor compresses freon, which, due to a sharp increase in pressure, heats up to a certain temperature.

The compressor of a conventional household refrigerator works in a similar way. The only significant difference between a refrigerator compressor and a heat pump compressor is a significantly lower performance.

VIDEO: How a refrigerator with a compressor works

3. Transfer of heat to the heating system (condensation).

After being compressed in the compressor, the high temperature refrigerant enters the condenser. In this case, the condenser is also a heat exchanger, in which, during condensation, heat is transferred from the refrigerant to the working medium of the heating circuit (for example, water in the underfloor heating system, or heating radiators).

In the condenser, the refrigerant changes from the gas phase to the liquid again. This process is accompanied by the release of heat, which is used for the heating system in the house and hot water supply (DHW).

4. Decrease in refrigerant pressure (expansion).

The liquid refrigerant must now be prepared for repeating the operating cycle. For this, the refrigerant flows through the narrow opening of the thermo-regulating valve (expansion valve). After "forcing" through the narrow opening of the throttle, the refrigerant expands, as a result of which its temperature and pressure drop.

This process is comparable to spraying an aerosol from a can. After spraying, the spray becomes colder for a short time. That is, there was a sharp drop in aerosol pressure due to pushing outward, the temperature also drops accordingly.

Now the refrigerant is again under such pressure that it is able to boil and evaporate, which we need to absorb heat from the coolant.

The task of the expansion valve (thermo-regulating valve) is to reduce the freon pressure by expanding it at the outlet of the narrow opening. Now freon is ready to boil again and absorb heat.

The cycle is repeated again until the heating and DHW system receives the required amount of heat from the heat pump.