Heat pump for heating a house: principle of operation, types and use. Principles of operation of a heat pump Design and principle of operation of heat pumps

By the end of the 19th century, powerful refrigeration units appeared that could pump at least twice as much heat as the energy required to operate them. It was a shock, because formally it turned out that a thermal perpetual motion machine was possible! However, upon closer examination, it turned out that the perpetual motion machine is still far away, and the low-grade heat produced using heat pump, and high-potential 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.

Working principle of a heat pump

Working principle of a heat pump is simple: due to mechanical work or other types of energy, it ensures the concentration of heat, previously evenly distributed over a certain volume, in one part of this volume. In the other part, accordingly, a heat deficit is formed, that is, cold.

Historically, heat pumps first began to be widely used as refrigerators - in essence, any refrigerator is a heat pump that pumps heat from refrigeration chamber outside (into the room or outside). There is still no alternative to these devices, and with all the variety of modern refrigeration equipment basic principle remains the same: pumping out heat 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 grille on the back wall of the cabinet) could also be used for heating. This was already the idea of ​​a heater based on a heat pump in her modern form- a refrigerator is the opposite, when heat is pumped into a closed volume (room) from an unlimited external volume (from the street). However, in this area, the heat pump has plenty of competitors - from traditional wood stoves and fireplaces to all sorts of modern heating systems. Therefore, for many years, while fuel was relatively cheap, this idea was viewed as nothing more than a curiosity - in most cases it was absolutely unprofitable economically, and only extremely rarely was such use justified - usually to recover 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 price of heating equipment and the relative reduction in the cost of production of heat pumps against this background, does such an idea become economically profitable in itself - after all, having paid once for a rather complex and expensive installation, then it will be possible to constantly save at 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 the heat pump is the essence of any refrigeration unit, we can say that the concept of “refrigeration machine” is its pseudonym. However, it should be borne in mind that despite the universality of the operating principles used, the designs of refrigeration machines are still focused specifically on producing cold, 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 a regular 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 using the Peltier effect, and the other includes evaporative ones, which in turn are divided into mechanical compressor (piston or turbine) and absorption (diffusion) ones. In addition, interest in the use of vortex tubes, in which the Ranque effect operates, as heat pumps is gradually increasing.

Heat pumps based on the Peltier effect

Peltier element

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

The physical essence of the effect is as follows. A Peltier element plate (also known as a “thermoelectric element”, English Thermoelectric Cooler, TEC) consists of two layers of semiconductor with different electron energy levels in the conduction band. When an electron moves under the influence of an external voltage to a higher-energy conduction band of another semiconductor, it must acquire energy. When it receives this energy, the contact point between the semiconductors cools (when current flows in the opposite direction, the opposite effect occurs - the contact point between the layers 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 absolute silent operation, compactness, complete indifference to spatial orientation (provided sufficient heat dissipation is ensured) 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 - approximately we can assume that per unit of pumped heat they will require twice as much external energy supplied. That is, by supplying 1 J of electrical energy, we can remove only 0.5 J of heat from the cooled area. It is clear that all the total 1.5 J will be released on the “warm” side of the Peltier element and will need to be diverted to the external environment. This is many times lower than the efficiency of compression evaporative heat pumps.

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

Use of Peltier elements

In accordance with their characteristics, the main area of ​​application of Peltier elements is currently usually limited to cases where it is necessary to cool something not very powerful, especially in conditions of strong shaking and vibration and with strict restrictions on weight and dimensions, - for example, various components and parts of electronic equipment, primarily military, aviation and space equipment. Perhaps the most widespread use of Peltier elements in everyday life is in low-power (5..30 W) portable car refrigerators.

Evaporative compression heat pumps

Diagram of the operating cycle of an evaporative compression heat pump

The operating principle of this class of heat pumps is as follows. The gaseous (wholly or partially) refrigerant is compressed by a compressor to a pressure at which it can turn into a liquid. Naturally, this heats up. The heated compressed refrigerant is supplied to the condenser radiator, where it is cooled to ambient temperature, releasing excess heat to it. This is the heating zone (the back wall of the kitchen refrigerator). If at the condenser inlet a significant part of the compressed hot refrigerant still remained in the form of vapor, then when the temperature decreases during heat exchange, it also condenses and turns into a liquid state. The relatively cooled liquid refrigerant is supplied to the expansion chamber, where, passing through a throttle or expander, it loses pressure, expands and evaporates, at least partially transforming into 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 vapor coolant 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 efficient heat removal. After this, the refrigerant in the form of vapor reaches the inlet of the compressor, which pumps it out and compresses it again. Then everything repeats all over again.

Thus, in the “hot” section of the compressor-condenser-throttle, the refrigerant is under high pressure and mainly in a liquid state, and in the “cold” section of the throttle-evaporator-compressor, the pressure is low, and the refrigerant is mainly in a vapor state. Both compression and vacuum are created by the same compressor. On the side of the tract opposite from the compressor, the high and low pressure separates the throttle that limits the flow of refrigerant.

Powerful industrial refrigerators use toxic but effective ammonia as a refrigerant, powerful turbochargers and sometimes expanders. In household refrigerators and air conditioners, the refrigerant is usually safer freons, and instead of turbo units, piston compressors and “capillary tubes” (chokes) are used.

IN general case a change in the state of aggregation of the refrigerant is not necessary - the principle will work for a constantly gaseous refrigerant - however, the large heat of change in the state of aggregation greatly increases the efficiency of the operating cycle. But if the refrigerant is in liquid form all the time, there will be no effect fundamentally - after all, the liquid is practically incompressible, and therefore neither increasing nor removing the pressure will change its temperature..

Chokes and expanders

The terms “throttle” and “expander” that are repeatedly used on this page usually mean little to people who are far from refrigeration technology. Therefore, a few words should be said about these devices and the main difference between them.

In technology, a throttle is a device designed to normalize flow by forcefully limiting it. In electrical engineering, this name is assigned to coils designed to limit the rate of current rise and usually used to protect electrical circuits from impulse noise. In hydraulics, throttles are usually called flow limiters, which are specially created narrowings of the channel with a precisely calculated (calibrated) clearance that provides the desired flow or the required flow resistance. A classic example of such chokes are jets, which were widely used in carburetor engines to ensure the calculated flow of gasoline during preparation. fuel mixture. The throttle valve in the same carburetors normalized the flow of air - the second necessary ingredient of this mixture.

In refrigeration engineering, a throttle is used to restrict the flow of refrigerant into the expansion chamber and maintain there the conditions necessary for efficient evaporation and adiabatic expansion. Too much flow can generally lead to the expansion chamber being filled with refrigerant (the compressor simply will not have time to pump it out) or, at least, to the loss of the necessary vacuum there. But it is the evaporation of the liquid refrigerant and the adiabatic expansion of its vapor that ensures the drop in the refrigerant temperature below the ambient temperature necessary for the operation of the refrigerator.

Operating principles of a throttle (left), piston expander (center) and turboexpander (left).

In the expander, the expansion chamber is somewhat modernized. In it, the evaporating and expanding refrigerant additionally performs mechanical work, moving the piston located there or rotating the turbine. In this case, the refrigerant flow can be limited 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, when using expanders, the main flow rationing can be carried out by a throttle (calibrated narrowing of the liquid refrigerant supply channel).

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

The advantage of an expander over a throttle 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 thermal cycle. Moreover, this work can then be put to good use, say, to drive pumps and compressors, as is done in the Zysin refrigerator. But a simple throttle 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 cost of production, it leaves the expander far behind. It is these reasons that usually limit the scope of use of expanders to powerful cryogenic equipment, and in household refrigerators less efficient, but almost eternal chokes are used, called “capillary tubes” there and representing a simple copper tube enough long length with a small diameter clearance (usually from 0.6 to 2 mm), which provides the necessary hydraulic resistance for the design refrigerant flow.

Advantages of compression heat pumps

The main advantage of this type of heat pump is its high efficiency, the highest among modern heat pumps. The ratio of externally supplied and pumped energy can reach 1:3 - that is, for every joule of energy supplied, 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 it generates (1 J) does not have to be removed to the external environment in the same place where 3 J of heat is released, pumped out from the cooling zone.

By the way, there is a theory of thermodynamic phenomena that differs from the generally accepted one, but is very interesting and convincing. So, one of its conclusions is that the work of compressing a gas, in principle, can only account for about 30% of its total energy. This means that the ratio of supplied and pumped energy of 1:3 corresponds to the theoretical limit and cannot be improved in principle using thermodynamic methods of heat pumping. However, some manufacturers are already claiming to achieve a ratio of 1:5 and even 1:6, and this is true - after all, in real refrigeration cycles, not only compression of the gaseous refrigerant is used, but also a change in its state of aggregation, and it is the latter process that is the main one.. .

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 along its entire operating path. However, household compression refrigerators that operate continuously for 20 years or more without any repairs are not at all uncommon. Another feature is a fairly high sensitivity to position in space. On its side or upside down, both the refrigerator and the air conditioner are unlikely to work. But this is due to the characteristics of specific designs, and not to the general principle of operation.

As a rule, compression heat pumps and refrigeration units are designed with the expectation that all refrigerant at the compressor inlet is in a vapor state. Therefore, if a large amount of unevaporated liquid refrigerant enters the compressor inlet, it can cause hydraulic shock and, as a result, serious damage to the unit. The reason for this situation may be either equipment wear or too low a condenser temperature - the refrigerant entering the evaporator is too cold and evaporates too sluggishly. For regular refrigerator This situation may 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 the cold. For a compression heat pump operating for heating, this can happen if you try to warm up a frozen room with it, even though it is also cold outside. Not very complex technical solutions eliminate this danger, but they increase the cost of the design, and during normal operation the mass household appliances there is no need for them - such situations do not arise.

Using compression heat pumps

Due to its high efficiency, this particular type of heat pump has become almost universally widespread, displacing all others into various exotic applications. 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

Duty cycle of evaporator absorption heat pumps is very similar to the operating cycle of evaporative compression units discussed just above. The main difference is that if in the previous case the vacuum necessary for evaporation of the refrigerant is created by mechanical suction of vapors by a compressor, then in absorption units the evaporated refrigerant flows from the evaporator into the absorber block, where it is absorbed (absorbed) by another substance - the absorbent. Thus, steam 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” between the refrigerant and the absorbent so that their binding forces during absorption can create a significant vacuum in the volume of the evaporator. Historically, the first and still widely used pair of substances is ammonia NH3 (refrigerant) and water (absorbent). When absorbed, ammonia vapor dissolves in water, penetrating (diffusing) into its thickness. From this process came the alternative names of such heat pumps - diffusion or absorption-diffusion.
In order to re-separate the refrigerant (ammonia) and the absorbent (water), the spent ammonia-rich water-ammonia mixture is heated in the desorber by an external source of thermal energy until boiling, then cooled somewhat. Water condenses first, but when high temperature Immediately after condensation, it is able to hold very little ammonia, so the bulk of the ammonia remains in the form of vapor. Here, the pressurized liquid fraction (water) and gaseous fraction (ammonia) are separated and separately cooled to ambient temperature. Cooled water with a low ammonia content is sent to the absorber, and when cooled in the condenser, the ammonia becomes liquid and enters the evaporator. There, the pressure drops and the ammonia evaporates, again cooling the evaporator and taking heat from outside. Then the ammonia vapor is recombined with water, removing excess ammonia vapor from the evaporator and maintaining a low pressure there. The ammonia-enriched solution is again sent to the desorber for separation. In principle, to desorption of ammonia it is not necessary to boil the solution; it is enough to simply heat it close to the boiling point, and the “excess” ammonia will evaporate from the water. But boiling allows the separation to be carried out most quickly and efficiently. The quality of such 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 organization and number of stages of the operating cycle, absorption-diffusion heat pumps are perhaps the most complex of all common types of similar equipment.

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

Absorption-diffusion refrigeration unit (ADHA) of the Morozko-ZM refrigerator. 1 - heat exchanger; 2 - solution collection; 3 - hydrogen battery; 4 - absorber; 5 - regenerative gas heat exchanger; 6 - reflux condenser (“dehydrator”); 7 - capacitor; 8 - evaporator; 9 - generator; 10 - thermosyphon; 11 - regenerator; 12 - weak solution tubes; 13 - steam pipe; 14 - electric heater; 15 - thermal insulation.

The first absorption refrigeration machines (ABRM) using an ammonia-water mixture appeared in the second half of the 19th century. They were not widely used in everyday life due to the toxicity of ammonia, but were very widely used in industry, providing cooling down to –45°C. In single-stage ABCMs, theoretically, the maximum cooling capacity is equal to the amount of heat spent on heating (in reality, of course, it is noticeably less). It was this fact that reinforced the confidence of the defenders of the very formulation of the second law of thermodynamics, which was discussed 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 ABHMs (refrigerant - water, absorbent - lithium bromide LiBr) appeared. Three-stage ABHM variants were patented in 1985-1993. Their prototypes are 30–50% more efficient than two-stage ones and are closer to mass-produced models of compression units.

Advantages of absorption heat pumps

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

The second advantage of these units, especially valuable in household applications, is the possibility of creating structures that do not contain moving parts, and therefore are practically silent (in Soviet models of this type, you could sometimes hear a quiet gurgle or a slight hiss, but, of course, this cannot be compared 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 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 it is impossible to notice a strong leak is impossible, and the room with the emergency unit will have to be left and ventilated “automatically”; ultra-low concentrations of ammonia are natural and absolutely harmless). In industrial installations, 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 ozone layer and does not cause a greenhouse effect.

Disadvantages of absorption heat pumps

Main disadvantage this type of heat pump- lower efficiency compared to compression ones.

The second disadvantage is the complexity of the design of the unit itself and the rather high corrosion load from the working fluid, either requiring the use of expensive and difficult to process corrosion-resistant materials, or reducing the service life of the unit to 5..7 years. As a result, the cost of hardware is noticeably higher than that of compression units of the same performance (primarily this applies to 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 if they deviated by a few degrees. The use of forced movement of the working fluid using pumps largely alleviates the severity of this problem, but lifting with a silent thermosiphon 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 is simply reduced. But it’s not for nothing that I placed this paragraph in the disadvantages section, because this does not mean that they can work in severe cold - in the cold, an aqueous solution of ammonia will simply freeze, 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 operate, even if it has not been disconnected from the network all this time - after all, it does not have mechanical pumps and compressors, and the heating power in household models is low enough for boiling in the area the heater did not become too intense. However, all this depends on the specific design features...

Using 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 presolar heating). In particular, special models of refrigerators powered by gas burners are produced, intended for motorists and yachtsmen.

Currently in Europe gas boilers sometimes replaced by absorption heat pumps heated by gas burner or from diesel fuel - they allow you not only to utilize the heat of combustion of fuel, but also to “pump up” additional heat from the street or from deep in the earth!

As experience shows, options with electric heating are also quite competitive in everyday life, primarily in the low power range - somewhere from 20 to 100 W. Lower powers are the domain of thermoelectric elements, but at higher powers the advantages of compression systems are still undeniable. In particular, among the Soviet and post-Soviet brands of refrigerators of this type, “Morozko”, “Sever”, “Kristall”, “Kiev” were popular with a typical volume of the refrigerating chamber from 30 to 140 liters, although there are also models with 260 liters (“ Crystal-12"). By the way, when assessing energy consumption, it is worth considering the fact that compression refrigerators almost always operate in short-term 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 average daily energy consumption may be completely different.

Vortex heat pumps

Vortex heat pumps The Ranque effect is used to separate warm and cold air. The essence of the effect is that gas, tangentially supplied into a pipe at high speed, swirls and separates inside this pipe: cooled gas can be taken from the center of the pipe, and heated gas 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 does not contain moving parts, and this ensures its high reliability and long service life. Vibration and position in space have virtually no effect on its operation.

A powerful air flow prevents freezing well, and the efficiency of vortex tubes depends little on the temperature of the inlet flow. The practical absence of fundamental temperature restrictions associated with hypothermia, overheating or freezing of the working fluid is also very important.

In some cases, the ability to achieve a record high temperature separation in one stage plays a role: in the literature, cooling figures of 200° or more are given. Typically one stage cools the air by 50..80°C.

Disadvantages of vortex heat pumps

Unfortunately, the efficiency of these devices is currently noticeably inferior to that of evaporative compression units. In addition, for efficient work they require a high flow rate of the working fluid. Maximum efficiency is noted at an input flow rate equal to 40..50% of the speed of sound - such a flow itself creates a lot of noise, and in addition, requires a productive and powerful compressor - the device is also by no means 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 a largely empirical exercise, where the result depends heavily on luck: “right or wrong.” A more or less reliable result is obtained only by reproducing already created successful samples, and the results of attempts significant change certain parameters are not always predictable and sometimes look paradoxical.

Using 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 explosion hazardous industries - after all, supplying a stream of air under pressure into a dangerous area is often much safer and cheaper than pulling protected electrical wiring there and installing electric motors in a special design .

Heat pump efficiency limits

Why are heat pumps still not widely used for heating (perhaps the only relatively common class of such devices are air conditioners with inverters)? There are several reasons for this, and in addition to the subjective ones associated with the lack of heating traditions using this technique, there are also objective ones, the main ones being 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 overcooling and freezing. They do not use a change in the aggregate state of the working fluid, and a powerful air flow performs the functions of the “No Frost” system. However, their efficiency is much less 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 back. 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 is completely excluded from the operating cycle, and the efficiency of the compression unit drops significantly, and if the refrigerant remains constantly liquid, it will not work at all.

Freezing

Heat extraction from air

Even if the temperatures of all heat pump units remain within the required range, during operation the heat extraction unit - the evaporator - is always covered with drops of moisture condensing from the surrounding air. But liquid water drains from it on its own, without particularly interfering with heat exchange. When the evaporator temperature becomes 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 regular refrigerator. As a result, the efficiency of heat exchange is significantly reduced, and then it is necessary to stop operation and defrost the evaporator. As a rule, in the refrigerator evaporator the temperature drops by 25..50°C, and in air conditioners, due to their specifics, the temperature difference is smaller - 10..15°C. Knowing this, it becomes clear why most air conditioners cannot be adjusted to a lower temperature +13..+17°С - this threshold is set by their designers to avoid icing of the evaporator, because its defrosting mode is usually not provided. This is also one of the reasons why almost all air conditioners with inverter mode do not work even at not very high temperatures. negative temperatures- only at the very Lately Models designed to operate in temperatures down to –25°C began to appear. In most cases, already at –5..–10°C, energy costs for defrosting become comparable to the amount of heat pumped from the street, and pumping heat from the street turns out to be ineffective, especially if the humidity of the outside air is close to 100% - then the external heat sink becomes covered with ice especially fast.

Heat extraction from soil and water

In this regard, heat from the depths of the earth has recently been increasingly considered as a non-freezing source of “cold heat” for heat pumps. This does not mean heated layers 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 “ordinary” heat of soil layers located at a depth of 5 to 50 meters. As is known, in middle lane the soil at such depths has a temperature of about +5°C, which changes very little throughout the year. In more southern areas, this temperature can reach +10°C and higher. Thus, the temperature difference between a comfortable +25°C and the ground around the heat sink is very stable and does not exceed 20°C, regardless of the frost outside (it should be noted that usually the temperature at the outlet of the heat pump is +50..+60°C, but and a temperature difference of 50°C is quite within the capabilities of heat pumps, including modern household refrigerators, which can easily provide –18°C in the freezer at room temperatures above +30°C).

However, if you bury one compact but powerful heat exchanger, it is unlikely that you will be able to achieve the desired effect. In fact, the heat sink in this case acts as an evaporator freezer, and if in the place where it is placed there is no powerful influx of heat (geothermal source or underground river), it will quickly freeze the surrounding soil, which will end all pumping of heat. 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 extractor covering thousands of cubic meters of soil at a considerable depth will most likely make this solution absolutely unprofitable economically. A less expensive option is to drill several wells at intervals of several meters from each other, as was done in the experimental “active house” near Moscow, but this is not cheap either - anyone who has made a well for water can independently estimate the costs of creating a geothermal fields of 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 reduce the temperature of the soil around the heat extractors 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 deteriorate. However, you can try to partially compensate for winter heat loss by increasing its injection to depth in the summer heat. But even without taking into account the additional energy costs 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 clearly will not be enough for the entire Russian winter, although such a supply of heat is still better than nothing. Moreover, there is very great importance has a level, volume and flow rate groundwater- abundantly moist soil with a sufficiently high speed of water flow will not allow you to make “reserves for the winter” - flowing water will take the pumped heat with it (even a tiny movement of groundwater by 1 meter per day in just a week will carry the stored heat aside by 7 meters, and it will be outside working area heat exchanger). True, the same flow of groundwater will reduce the degree of cooling of the soil in winter - new portions of water will bring new heat received away from the heat exchanger. Therefore, if there is a deep lake, large pond or river nearby 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 stationary soil, even in a stagnant pond or lake, convection of free water can provide much more efficient heat supply to the heat extractor from a significant volume of the reservoir. But here it is necessary to make sure that the heat exchanger under no circumstances overcools to the freezing point of water and does not begin to freeze 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 is often not so different strongly, and an attempt to use the enormous heat of crystallization of water in ground heat removal under certain conditions can be justified).

Operating principle of a geothermal heat pump is based on collecting heat from soil or water and transferring it to the building’s heating system. To collect heat, an antifreeze liquid flows through a pipe located in the soil or body of water near the building to the heat pump. A heat pump, like a refrigerator, cools a liquid (removes heat), and the liquid is cooled by approximately 5 °C. The liquid again flows through the pipe in the external soil or water, restores its temperature, and again enters the heat pump. The heat collected by the heat pump is transferred to the heating system and/or to heat hot water.

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

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

Having refrigerators and air conditioners in their home, few people know that the principle of operation of a heat pump is implemented in them.

About 80% of the power provided by a heat pump comes from ambient heat in the form of dissipated heat. solar radiation. It is this pump that simply “pumps” it from the street into the house. The operation of a heat pump is similar to the principle of operation of a refrigerator, but the direction of heat transfer is different.

Simply put…

To cool the bottle mineral water, You put it in the refrigerator. The refrigerator must “take” part of the thermal energy from the bottle and, according to the law of conservation of energy, move it somewhere and give it away. The refrigerator transfers heat to a radiator, usually located on the rear wall. At the same time, the radiator heats up, releasing its heat into the room. In fact, it heats the room. This is especially noticeable in small minimarkets in the summer, when several refrigerators are turned on in the room.

We invite you to dream up your imagination. Let's assume that we will constantly put warm objects in the refrigerator, and by cooling them, it will heat the air in the room. Let's go to the “extremes”... Let's place the refrigerator in window opening with the freezer door open to the outside. The refrigerator radiator will be located indoors. During operation, the refrigerator will cool the air outside, transferring the “taken” heat into the room. This is how a heat pump works, taking dispersed heat from the environment and transferring it into the room.

Where does the pump get the heat?

The operating principle of a heat pump is based on the “exploitation” of natural low-potential heat sources from the environment.

They may be:

• just outside air;
• warmth of water bodies (lakes, seas, rivers);
• warmth of the soil, groundwater (thermal and artesian).

How does a heat pump and the heating system with it work?

The heat pump is integrated into the heating system, which consists of 2 circuits + a third circuit - the system of the pump itself. A non-freezing coolant circulates along the external circuit, which absorbs heat from the surrounding space.

Getting into the heat pump, or more precisely its evaporator, the coolant releases an average of 4 to 7 °C to the heat pump refrigerant. And its boiling point is -10 °C. As a result, the refrigerant boils and then transforms into a gaseous state. The coolant of the external circuit, already cooled, goes to the next “turn” in the system to set the temperature.

The functional circuit of the heat pump includes:

• evaporator;
• compressor (electric);
• capillary;
• capacitor;
• refrigerant;
• thermostatic control device.

The process looks something like this!

The refrigerant that has “boiled” in the evaporator is supplied through a pipeline to a compressor powered by electricity. This “hard worker” compresses the gaseous refrigerant to high pressure, which, accordingly, leads to an increase in its temperature.

The now hot gas then enters another heat exchanger, which is called a condenser. Here, the heat of the refrigerant is transferred to the room air or coolant, which circulates through the internal circuit of the heating system.

The refrigerant cools while simultaneously turning into a liquid. It then passes through the capillary pressure reducing valve, where it “loses” pressure and again enters the evaporator.

The cycle is closed and ready to repeat!

Approximate calculation of the heating output of the installation

Within an hour, up to 2.5-3 m 3 of coolant flows through the external collector through the pump, which the earth can heat by ∆t = 5-7 °C.

To calculate the thermal power of such a circuit, use the formula:

Q = (T_1 - T_2)*V_heat

V_heat - volumetric flow rate of coolant per hour (m^3/hour);

T_1 - T_2 - temperature difference between inlet and inlet (°C).

Types of heat pumps

Heat pumps are classified according to the type of dissipated heat used:

• ground-water (use closed ground contours or deep geothermal probes and a water heating system);
• water-water (they use open wells for the intake and discharge of groundwater - the external circuit is not looped, the internal heating system is water);
• water-air (use of external water circuits and an air-type heating system);
• (use of dissipated heat from external air masses complete with air heating system of the house).

Advantages and benefits of heat pumps

Cost effective. The operating principle of a heat pump is based not on the production, but on the transfer (transportation) of thermal energy, so it can be argued that its efficiency is greater than one. What nonsense? - you say. The topic of heat pumps includes a value - the heat conversion coefficient (HCT). It is by this parameter that units of similar types are compared with each other. Its physical meaning is to show the ratio of the amount of heat received to the amount of energy expended for this. For example, with KPT = 4.8, the 1 kW of electricity expended by the pump will allow us to obtain 4.8 kW of heat free of charge, that is, free of charge from nature.

Universal ubiquity of application. Even in the absence of accessible power lines, the heat pump compressor can be powered by a diesel drive. And “natural” heat is available in every corner of the planet - the heat pump will not remain “hungry”.

Environmentally friendly use. There are no combustion products in the heat pump, and its low energy consumption “operates” power plants less, indirectly reducing harmful emissions from them. The refrigerant used in heat pumps is ozone-friendly and does not contain chlorocarbons.

Bidirectional operating mode. A heat pump can heat a room in winter and cool it in summer. The “heat” taken from the room can be used effectively, for example, to heat water in a swimming pool or in a hot water system.

Operational safety. In the principle of operation of a heat pump, you will not consider dangerous processes. Absence open fire and harmful emissions hazardous to humans, the low temperature of the coolant makes the heat pump a “harmless” but useful household appliance.

Some nuances of operation

Effective use of the heat pump operating principle requires compliance with several conditions:

• the room that is heated must be well insulated (heat loss up to 100 W/m2) - otherwise, taking heat from the street, you will heat the street at your own expense;
• Heat pumps are advantageous to use for low-temperature heating systems. Underfloor heating systems (35-40 °C) are ideal for such criteria. The heat conversion coefficient significantly depends on the temperature ratio of the input and output circuits.

Let's summarize what has been said!

The essence of the principle of operation of a heat pump is not in the production, but in the transfer of heat. This allows you to get high coefficient(from 3 to 5) thermal energy conversion. Simply put, every 1 kW of electricity used will “transfer” 3-5 kW of heat into the house. Anything else that needs to be said?

Let's try to explain in the language of the common man what " HEAT PUMP«:

Heat pump - This is a special device that combines a boiler, a source of hot water supply and an air conditioner for cooling. The main difference between a heat pump and other heat sources is the ability to use renewable low-potential energy taken from the environment (land, water, air, Wastewater) to cover heat needs during heating season, heating water for hot water supply and cooling the house. The heat pump therefore provides a highly efficient energy supply without gas or other hydrocarbons.

Heat pump is a device that works on the principle of a reverse chiller, transferring heat from a low-temperature source to a higher-temperature environment, such as your home's heating system.

Each heat pump system has the following main components:

- primary circuit - closed circulation system, which serves to transfer heat from the ground, water or air to the heat pump.
- secondary circuit - closed system, which serves to transfer heat from the heat pump to the heating system, hot water supply or ventilation (supply heating) in the house.

Working principle of a heat pump similar to the operation of an ordinary refrigerator, only in reverse. The refrigerator takes heat from food and transfers it outside (to a radiator located on its rear wall). A heat pump transfers heat accumulated in the soil, ground, reservoir, groundwater or air into your home. Like a refrigerator, this energy-efficient heat generator has the following main elements:

- condenser (heat exchanger in which heat is transferred from the refrigerant to the elements of the room heating system: low-temperature radiators, fan coils, warm floor, radiant heating/cooling panels);
— throttle (a device that serves to reduce pressure, temperature and, as a result, close the heating cycle in the heat pump);
— evaporator (heat exchanger in which heat is taken from a low-temperature source to the heat pump);
- compressor (a device that increases the pressure and temperature of refrigerant vapors).

Heat pump arranged in such a way as to make heat move in different directions. For example, when heating a house, heat is taken from some cold external source (ground, river, lake, outside air) and transferred to the house. To cool (condition) a house, heat is taken from more warm air in the house and is transmitted outside (discharged). In this respect, a heat pump is similar to a conventional hydraulic pump, which pumps liquid from a lower level to an upper level, whereas under normal conditions the liquid always moves with top level to the lower one.

Today, the most common are vapor compression heat pumps. The principle of their action is based on two phenomena: firstly, the absorption and release of heat by a liquid when the state of aggregation changes - evaporation and condensation, respectively; secondly, the change in evaporation (and condensation) temperature with a change in pressure.

In the evaporator of a heat pump, the working fluid is a refrigerant that does not contain chlorine; it is under low pressure and boils at a low temperature, absorbing heat from a low-potential source (for example, soil). Then the working fluid is compressed in a compressor, which is driven by an electric or other motor, and enters a condenser, where at high pressure it condenses at a higher temperature, releasing the condensation heat to a heat receiver (for example, the coolant of a heating system). From the condenser, the working fluid again enters the evaporator through the throttle, where its pressure decreases and the process of refrigerant boiling begins anew.

Heat pump capable of removing heat from various sources, for example, air, water, soil. Also, it can release heat into air, water or ground. The warmer medium that receives heat is called a heat sink.

Heat pump X/Y uses medium X as a heat source and heat carrier Y. Pumps are distinguished “air-water”, “ground-water”, “water-water”, “air-air”, “ground-air”, “water-air”.

Ground-to-water heat pump:

Air-to-water heat pump:

Regulation of the operation of a heating system using heat pumps in most cases is carried out by turning it on and off according to a signal from a temperature sensor, which is installed in the receiver (when heating) or the source (when cooling) of heat. Setting up a heat pump is usually done by changing the cross-section of the throttle (thermostatic valve).

Like a refrigeration machine, a heat pump uses mechanical (electrical or other) energy to drive a thermodynamic cycle. This energy is used to drive the compressor (modern heat pumps with a power of up to 100 kW are equipped with highly efficient scroll compressors).

(transformation or efficiency ratio) of a heat pump is the ratio of the amount of thermal energy that the heat pump produces to the amount of electrical energy that it consumes.

COP conversion factor depends on the temperature level in the evaporator and condenser of the heat pump. This value varies for various heat pump systems in the range from 2.5 to 7, that is, for 1 kW of electrical energy expended, the heat pump produces from 2.5 to 7 kW of thermal energy, which is beyond the power of either a condensing gas boiler or any other generator. heat.

Therefore it can be argued that Heat pumps produce heat using a minimal amount of expensive electrical energy.

Energy saving and efficiency of use of a heat pump primarily depends on where you decide to draw low-temperature heat from, secondly - from the method of heating your home (water or air) .

The fact is that the heat pump works as a “transfer base” between two thermal circuits: one heating at the inlet (on the evaporator side) and the second, heating at the outlet (condenser).

All types of heat pumps have a number of features that you need to remember when choosing a model:

Firstly, a heat pump only pays off in a well-insulated house. The warmer the house, the greater the benefit from using this device. As you understand, heating the street using a heat pump, collecting crumbs of heat from it, is not entirely reasonable.

Secondly, the greater the difference in coolant temperatures in the input and output circuits, the lower the heat conversion coefficient (COR), that is, the lower the savings in electrical energy. That is why more profitable connection of a heat pump to low-temperature heating systems. First of all, we are talking about heating with water heated floors or infrared water ceiling or wall panels. But the more hot water The heat pump prepares for the output circuit (radiators or shower), the less power it develops and the more electricity it consumes.

Thirdly, to achieve greater benefits, it is practiced to operate a heat pump with an additional heat generator (in such cases they talk about using bivalent heating circuit ).

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Heat pumps for home heating: pros and cons

1. Features of heat pumps
2. Types of heat pumps
3. Geothermal heat pumps
4. Advantages and disadvantages of heat pumps

One of the highly efficient methods of heating a country house is the use of heat pumps.

The operating principle of heat pumps is based on the extraction of thermal energy from the soil, reservoirs, groundwater, and air. Heat pumps for heating your home do not have a harmful impact on the environment. You can see what such heating systems look like in the photo.

Such organization of home heating and hot water supply has been possible for many years, but it began to become widespread only recently.

Features of heat pumps

The operating principle of such devices is similar to refrigeration equipment.

Heat pumps take heat, accumulate it and enrich it, and then transfer it to the coolant. A condenser is used as a heat-generating device, and an evaporator is used to recover low-potential heat.

The constant increase in the cost of electricity and the imposition of strict requirements for environmental protection is causing the search for alternative methods of generating heat for heating houses and heating water.

One of them is the use of heat pumps, since the amount of thermal energy received is several times greater than the electricity consumed (more details: “Economical heating with electricity: pros and cons”).

If we compare heating with gas, solid or liquid fuel, with heat pumps, the latter will be more economical. However, the installation of a heating system with such units is much more expensive.

Heat pumps consume the electricity needed to run the compressor. Therefore, this type of heating of buildings is not suitable if there are frequent problems with power supply in the area.

Heating a private house with a heat pump can have different efficiency; its main indicator is heat conversion - the difference between the electricity consumed and the heat received.

There is always a difference between the evaporator and condenser temperatures.

The higher it is, the lower the efficiency of the device. For this reason, when using a heat pump, you need to have a considerable source of low potential heat. Based on this, it follows that the larger the size of the heat exchanger, the lower the energy consumption. But at the same time, devices with large dimensions have a much higher cost.

Heating using a heat pump is found in many developed countries.

Moreover, they are also used for heating apartments and public buildings - this is much more economical than the heating system familiar in our country.

Types of heat pumps

These devices can be used over a wide temperature range. Usually they work normally at temperatures from – 30 to + 35 degrees.

The most popular are absorption and compression heat pumps.

The latter of them use mechanical and electrical energy to transfer heat. Absorption pumps are more complex, but they are able to transfer heat using the source itself, thereby significantly reducing energy costs.

As for heat sources, these units are divided into the following types:

• air;
• geothermal;
• secondary heat.

Air heat pumps for heating take heat from the surrounding air.

Geothermal uses the thermal energy of the earth, underground and surface waters (for more details: “Geothermal heating: principles of operation with examples”). Recycled heat pumps take energy from sewage and central heating - these devices are mainly used to heat industrial buildings.

This is especially beneficial if there are sources of heat that must be recycled (read also: “We use the heat of the earth to heat the house”).

Heat pumps are also classified by type of coolant; they can be air, soil, water, or combinations thereof.

Geothermal heat pumps

Heating systems that use heat pumps are divided into two types - open and closed. Open structures are designed to heat the water passing through the heat pump. After the coolant passes through the system, it is discharged back into the ground.

Such a system works ideally only if there is a significant volume of clean water, taking into account the fact that its consumption will not harm the environment and will not conflict with current legislation. Therefore, before using a heating system that receives energy from groundwater, you should consult with the relevant organizations.

Closed systems are divided into several types:

1. Geothermal with a horizontal arrangement involves laying the collector in a trench below the freezing depth of the soil.

   This is approximately 1.5 meters. The collector is laid in rings in order to reduce the excavation area to a minimum and provide a sufficient circuit in a small area (read: “Geothermal heat pumps for heating: the principle of the system”).

   This method is only suitable if there is sufficient free area available.

2. Geothermal structures with a vertical arrangement involve placing the collector in a well up to 200 meters deep. This method is used when it is not possible to place the heat exchanger over a large area, which is necessary for a horizontal well.

   Also, geothermal systems with vertical wells are made in case of uneven terrain of the site.

3. Geothermal water means placing the collector in a reservoir at a depth below the freezing level. Laying is done in rings. Such systems cannot be used if the reservoir is small or insufficiently deep.

   It must be taken into account that if the reservoir freezes at the level where the collector is located, the pump will not be able to work.

Heat pump air water - features, details on video:

Advantages and disadvantages of heat pumps

Heating a country house with a heat pump has both positive and negative sides. One of the main advantages of heating systems is environmental friendliness.

Heat pumps are also economical, unlike other heaters that consume electricity. Thus, the amount of generated thermal energy is several times greater than the consumed electricity.

Heat pumps are characterized by increased fire safety; they can be used without additional ventilation.

Since the system has a closed loop, financial expenses during operation are minimized - you only have to pay for the electricity consumed.

The use of heat pumps also allows you to cool the room in the summer - this is possible by connecting fan coils and a “cold ceiling” system to the collector.

These devices are reliable, and the control of work processes is fully automatic. Therefore, no special skills are required to operate heat pumps.

The compact size of the devices is also important.

The main disadvantage of heat pumps:

• high price and significant installation costs. It is unlikely that you will be able to construct heating with a heat pump yourself without special knowledge. It will take more than one year for the investment to pay off;
• The service life of the devices is approximately 20 years, after which there is a high probability that major repairs will be required.

  This won't be cheap either;

• the price of heat pumps is several times higher than the cost of boilers running on gas, solid or liquid fuel. You will have to pay a lot of money for drilling wells.

But on the other hand, heat pumps do not require regular maintenance, as is the case with many other heating devices.

Despite all the advantages of heat pumps, they are still not widely used. This is due, first of all, to the high cost of the equipment itself and its installation. It will be possible to save only if you create a system with a horizontal heat exchanger, if you dig trenches yourself, but this will take more than one day. As for operation, the equipment turns out to be very profitable.

Heat pumps are an economical way to heat buildings that are environmentally friendly.

They may not be widely used due to their high cost, but the situation may change in the future. In developed countries, many owners of private houses use heat pumps - there the government encourages concern for the environment, and the cost of this type of heating is low.

Thermal ground or geothermal pump is one of the most energy efficient alternative energy systems. Its operation does not depend on the season and ambient temperature, as for an air-to-air pump, and is not limited by the presence of a reservoir or well with groundwater near the house, like a water-to-water system.

A ground-to-water heat pump, which uses heat taken from the soil to heat the coolant in the heating system, has the highest and most constant efficiency, as well as an energy conversion coefficient (ECR).

Its value is 1:3.5-5, that is, every kilowatt of electricity spent on pump operation is returned in 3.5-5 kilowatts of thermal energy. Thus, the heating power of the soil pump makes it possible to use it as the only source of heat even in a house with a large area, of course, when installing a unit of appropriate power.

A submersible soil pump requires equipment in a soil circuit with a circulating coolant to extract heat from the earth.

There are two possible options for its placement: a horizontal soil collector (a pipe system at a shallow depth, but a relatively large area) and a vertical probe placed in a well from 50 to 200 m deep.

The efficiency of heat exchange with soil significantly depends on the type of soil - moisture-filled soil gives off much more heat than, for example, sandy soil.

The most common are pumps operating on the ground-water principle, in which the coolant stores the energy of the soil and, as a result of passing through a compressor and heat exchanger, transfers it to water as a coolant in the heating system. The prices for this type of soil pumps correspond to their high efficiency and productivity.

Submersible Soil Pump

Any complex high-tech units, such as GRAT ground pumps, as well as soil heat pumps, require the attention of professionals.

Heat pump

We offer a full range of services for the sale, installation and maintenance of heating and hot water supply systems based on heat pumps.

Today, among the countries producing such units on the market, European countries and China are especially popular.

The most famous heat pump models: Nibe, Stiebel Eltron, Mitsubishi Zubadan, Waterkotte. The domestic ground source heat pump is also in no less demand.

Our company prefers to work only with equipment from reliable European manufacturers: Viessmann and Nibe.

The heat pump extracts accumulated energy from various sources - groundwater, artesian and thermal waters - waters of rivers, lakes, seas; treated industrial and domestic wastewater; ventilation emissions and flue gases; soil and the bowels of the earth - transfers and converts higher temperatures into energy.

Heat pump – highly economical, environmentally friendly heating and comfort technology

Thermal energy exists around us, the problem is how to extract it without spending significant energy resources.

Heat pumps extract accumulated energy from various sources - ground, artesian and thermal waters - waters of rivers, lakes, seas; treated industrial and domestic wastewater; ventilation emissions and flue gases; soil and the bowels of the earth - transfers and converts higher temperatures into energy.

The choice of the optimal heat source depends on many factors: the size of the energy needs of your home, the installed heating system, and the natural conditions of the region where you live.

Design and principle of operation of a heat pump

The heat pump functions like a refrigerator - only in reverse.

The refrigerator transfers heat from inside to outside.

A heat pump transfers heat accumulated in the air, soil, subsoil or water into your home.

The heat pump consists of 4 main units:

Evaporator,

Capacitor,

Expansion valve (discharge valve-
throttle, lowers pressure),

Compressor (increases pressure).

These units are connected by a closed pipeline.

The piping system circulates refrigerant, which is a liquid in one part of the cycle and a gas in the other.

The Earth's interior as a deep heat source

The earth's interior is a free heat source that maintains the same temperature all year round. Using the heat of the earth's interior is an environmentally friendly, reliable and safe technology for providing heat and hot water supply to all types of buildings, large and small, public and private. The level of investment is quite high, but in return you will receive an alternative heating system that is safe to operate, with minimal maintenance requirements and has the longest service life. Heat conversion coefficient (see. page 6) high, reaches 3. The installation does not require much space and can be installed on a small plot of land. The amount of restoration work after drilling is insignificant, the impact of the drilled well on the environment is minimal. There is no impact on groundwater levels since groundwater is not consumed. Thermal energy is transferred to the convection water heating system and used for hot water supply.

Ground heat - nearby energy

Heat accumulates in the surface layer of the earth during the summer.

Using this energy for heating is advisable for buildings with high energy consumption. The greatest amount of energy is extracted from soil with the highest moisture content.

Ground heat pump

Water heat sources

The sun heats the water in seas, lakes and other water sources.

Solar energy accumulates in water and bottom layers. Rarely does the temperature drop below +4 °C. The closer to the surface, the more the temperature varies throughout the year, but in depth it is relatively stable.

Heat pump with water heat source

The heat transfer hose is laid at the bottom or in the bottom soil, where the temperature is still slightly higher,
than the water temperature.

It is important that the hose be weighted to prevent
the hose floats to the surface. The lower it lies, the lower the risk of damage.

A water source as a heat source is very effective for buildings with relatively high heat energy needs.

Heat of groundwater

Even groundwater can be used to heat buildings.

This requires a drilled well, from where water is pumped into the heat pump.

When using groundwater, high demands are placed on its quality.

Heat pump with ground water as heat source

After passing through the heat pump, the water can be transported to a drainage channel or well. Such a solution may lead to an undesirable decrease in groundwater levels, as well as reduce the operational reliability of the installation and have a negative impact on nearby wells.

Nowadays this method is used less and less.

Groundwater can also be returned to the ground through partial or complete infiltration.

Such a profitable heat pump

Heat conversion coefficient The higher the efficiency of the heat pump, the more profitable it is. Efficiency is determined by the so-called heat conversion coefficient or temperature transformation coefficient, which is the ratio of the amount of energy generated by the heat pump to the amount of energy expended in the heat transfer process. For example: The temperature transformation coefficient is 3. This means that the heat pump supplies 3 times more energy than it consumes. In other words, 2/3 was received “for free” from the heat source. How to make a heat pump for heating a house with your own hands: operating principle and diagrams The higher the energy needs of your home, the more money you save. Note The value of the temperature transformation coefficient is affected by the presence/ignoring of parameters of additional equipment (circulation pumps) in the calculations, as well as various temperature conditions. The lower the temperature distribution, the higher the temperature transformation coefficient becomes; heat pumps are most effective in heating systems with low temperature characteristics.

When selecting a heat pump for your heating system, it is not profitable to orient power indicators of the heat pump for maximum power requirements (to cover energy costs in the heating circuit on the coldest day of the year). Experience shows that the heat pump should generate about 50-70% of this maximum, the heat pump should cover 70-90% (depending on the heat source) of the total annual energy demand for heating and hot water supply. At low external temperatures, the heat pump is used with existing boiler equipment or a peak closer, which is equipped with the heat pump.

Comparison of costs for installing a heating system for an individual house based on a heat pump and an oil boiler.

For analysis, let’s take a house with an area of ​​150-200 sq.m.

The most common version of a modern country house for permanent use today.
The use of modern building materials and technologies ensures the building’s heat loss at the level of 55 W/sq.m of floor.
To cover the total needs for thermal energy spent on heating and hot water supply of such a house, it is necessary to install a heat pump or boiler with a thermal capacity of approximately 12 kW/h.
The cost of the heat pump or diesel boiler itself is only a fraction of the costs that must be incurred to commission the heating system as a whole.

Below is a far from complete list of the main associated costs for installing a turnkey heating system based on a liquid fuel boiler, which are absent when using a heat pump:

air vent filter, fix package, safety group, burner, boiler piping system, control panel with weather-dependent automatics, emergency electric boiler, fuel tank, chimney, boiler.

All this adds up to at least 8000-9000 euros. Taking into account the need to install the boiler room itself, the cost of which, taking into account all the requirements of the supervisory authorities, is several thousand euros, we come to a conclusion that is paradoxical at first glance, namely, the practical comparability of the initial capital costs when installing a turnkey heating system based on a heat pump and a liquid fuel boiler.

In both cases, the cost is close to 15 thousand euros.

Considering the following undeniable advantages of a heat pump, such as:
Economical. At the cost of 1 kW of electricity is 1 ruble 40 kopecks, 1 kW of thermal power will cost us no more than 30-45 kopecks, while 1 kW of thermal energy from the boiler will already cost 1 ruble 70 kopecks (at a price of diesel fuel of 17 rubles/l);
Ecology. An environmentally friendly heating method for both the environment and the people in the room;
Safety. There is no open flame, no exhaust, no soot, no diesel smell, no gas leakage, no fuel oil spill.

There are no fire hazardous storage facilities for coal, firewood, fuel oil or diesel fuel;

Reliability. A minimum of moving parts with a high service life. Independence from the supply of fuel material and its quality. Virtually no maintenance required. The service life of the heat pump is 15 – 25 years;
Comfort. The heat pump operates silently (no louder than a refrigerator);
Flexibility. The heat pump is compatible with any circulation heating system, and its modern design allows it to be installed in any room;

An increasing number of individual home owners are choosing a heat pump for heating, both in new construction and when upgrading an existing heating system.

Heat pump device

The near-surface technology of using low-grade thermal energy using a heat pump can be considered as some kind of technical and economic phenomenon or a real revolution in the heat supply system.

Heat pump device. The main elements of a heat pump are an evaporator, a compressor, a condenser and a flow regulator connected by a pipeline - a throttle, expander or vortex tube (Fig. 16).

Schematically, a heat pump can be represented as a system of three closed circuits: in the first, external, a heat sink (a coolant that collects heat from the environment) circulates, in the second - a refrigerant (a substance that evaporates, taking away the heat of the heat sink, and condenses, giving up heat to the heat sink) , in the third - a heat receiver (water in the heating and hot water supply systems of the building).

16. Heat pump device

The external circuit (collector) is a pipeline laid in the ground or in water in which a non-freezing liquid - antifreeze - circulates. It should be noted that the source of low-potential energy can be either heat of natural origin (outside air; heat of ground, artesian and thermal waters; water of rivers, lakes, seas and other non-freezing natural bodies of water) and man-made origin (industrial discharges, wastewater treatment plants, heat from power transformers and any other waste heat).

The temperature required for pump operation is usually 5-15 °C.

The second circuit, where the refrigerant circulates, has built-in heat exchangers - an evaporator and a condenser, as well as devices that change the pressure of the refrigerant - a choke (a narrow calibrated hole) that sprays it in the liquid phase and a compressor that compresses it in the gaseous state.

Duty cycle. The liquid refrigerant is forced through the throttle, its pressure drops, and it enters the evaporator, where it boils, taking away the heat supplied by the collector from the environment.

Next, the gas into which the refrigerant has turned is sucked into the compressor, compressed and, heated, pushed into the condenser. The condenser is the heat-releasing unit of the heat pump: here the heat is received by the water in the heating circuit system. In this case, the gas cools and condenses in order to be discharged again in the expansion valve and return to the evaporator. After this, the working cycle is repeated.

In order for the compressor to work (maintain high pressure and circulation), it must be connected to electricity.

But for every kilowatt-hour of electricity expended, the heat pump produces 2.5-5 kilowatt-hours of thermal energy.

Heat pump for heating: principle of operation and advantages of use

This ratio is called the transformation ratio (or heat conversion ratio) and serves as an indicator of the efficiency of the heat pump.

The value of this value depends on the difference in temperature levels in the evaporator and condenser: the greater the difference, the smaller it is. For this reason, the heat pump should use as much of the low-grade heat source as possible, without trying to cool it too much.

Types of heat pumps.

Heat pumps come in two main types – closed loop and open loop.

Open circuit pumps They use water from underground sources as a heat source - it is pumped through a drilled well into a heat pump, where heat exchange occurs, and the cooled water is discharged back into the underwater horizon through another well.

This type of pump is advantageous because the underground water maintains a stable and fairly high temperature all year round.

Closed cycle pumps There are several types: vertical and g horizontal(Fig. 17).

Pumps with a horizontal heat exchanger have a closed external circuit, the main part of which is dug horizontally into the ground, or laid along the bottom of a nearby lake or pond.

The depth of underground pipes in such installations is up to a meter. This method of obtaining geothermal energy is the cheapest, but its use requires a number of technical conditions that are not always available in the area being developed.

The main thing is that the pipes should be laid in such a way as not to interfere with the growth of trees or agricultural work, so that there is a low probability of damage to underwater pipes during agricultural or other activities.

Rice. 17. Near-surface geothermal system with heat exchange

Pumps with vertical heat exchanger include an external contour dug deep into the ground - 50-200 m.

This is the most efficient type of pump and produces the cheapest heat, but is much more expensive to install than previous types. The benefit in this case is due to the fact that at a depth of more than 20 meters, the temperature of the earth is stable all year round and amounts to 15-20 degrees, and only increases with increasing depth.

Air conditioning using heat pumps. One of the important qualities of heat pumps is the ability to switch from heating mode in winter to air conditioning mode in summer: only fan coils are used instead of radiators.

A fan coil is an internal unit into which heat or coolant and air driven by a fan are supplied, which, depending on the temperature of the water, is either heated or cooled.

Includes: heat exchanger, fan, air filter and control panel.

Since fan coil units can operate for both heating and cooling, several piping options are possible:
- S2 - pipe - when the role of heat and coolant is played by water and their mixing is allowed (and, as an option, a device with an electric heater and a heat exchanger that works only for cooling);
- S4 - pipe - when the coolant (for example, ethylene glycol) cannot be mixed with the coolant (water).

The power of fan coil units for cold ranges from 0.5 to 8.5 kW, and for heat – from 1.0 to 20.5 kW.

They are equipped with low-noise (from 12 to 45 dB) fans with up to 7 rotation speeds.

Prospects. The widespread use of heat pumps is hampered by lack of public awareness. Potential buyers are frightened by the rather high initial costs: the cost of the pump and installation of the system is $300-1200 per 1 kW of required heating power. But a competent calculation convincingly proves the economic feasibility of using these installations: capital investments pay off, according to rough estimates, in 4-9 years, and heat pumps last 15-20 years before major repairs.

Paying for electricity and heating becomes more difficult every year. When building or purchasing a new home, the problem of economical energy supply becomes especially acute. Due to periodically recurring energy crises, it is more profitable to increase the initial costs of high-tech equipment in order to then receive heat at a minimal cost for decades.

The most cost-effective option in some cases is a heat pump for heating a home; the operating principle of this device is quite simple. It is impossible to pump heat in the literal sense of the word. But the law of conservation of energy allows technical devices to lower the temperature of a substance in one volume, while simultaneously heating something else.

What is a heat pump (HP)

Let's take an ordinary household refrigerator as an example. Inside the freezer, water quickly turns to ice. On the outside there is a radiator grille that is hot to the touch. From it, the heat collected inside the freezer is transferred to the room air.

The TN does the same thing, but in reverse order. The radiator grille, located on the outside of the building, is much larger in order to collect enough heat from the environment to heat the home. The coolant inside the radiator or manifold tubes transfers energy to the heating system inside the house and is then heated again outside the house.

Device

Providing heat to a home is a more complex technical task than cooling a small volume of a refrigerator where a compressor with freezing and radiator circuits is installed. The design of an air heat pump is almost as simple, it receives heat from the atmosphere and heats the internal air. Only fans are added to blow the circuits.

It is difficult to obtain a large economic effect from installing an air-to-air system due to the low specific gravity of atmospheric gases. One cubic meter of air weighs only 1.2 kg. Water is about 800 times heavier, so the calorific value also has a multiple difference. From 1 kW of electrical energy spent by an air-to-air device, only 2 kW of heat can be obtained, and a water-to-water heat pump provides 5–6 kW. TN can guarantee such a high coefficient of efficiency (efficiency).

Composition of pump components:

1. Home heating system, for which it is better to use heated floors.
2. Boiler for hot water supply.
3. A condenser that transfers energy collected externally to the indoor heating fluid.
4. An evaporator that takes energy from the coolant that circulates in the external circuit.
5. A compressor that pumps refrigerant from the evaporator, converting it from a gaseous to a liquid state, increasing the pressure and cooling it in the condenser.
6. An expansion valve is installed in front of the evaporator to regulate the refrigerant flow.
7. The outer contour is laid on the bottom of the reservoir, buried in trenches or lowered into wells. For air-to-air heat pumps, the circuit is an external radiator grille, blown by a fan.
8. Pumps pump coolant through pipes outside and inside the house.
9. Automation for control according to a given room heating program, which depends on changes in outside air temperature.

Inside the evaporator, the coolant of the external pipe register is cooled, giving off heat to the refrigerant of the compressor circuit, and then is pumped through the pipes at the bottom of the reservoir. There it heats up and the cycle repeats again. The condenser transfers heat to the cottage heating system.

Prices for different heat pump models

Heat pump

Principle of operation

The thermodynamic principle of heat transfer, discovered at the beginning of the 19th century by the French scientist Carnot, was later detailed by Lord Kelvin. But the practical benefits of their works devoted to solving the problem of heating housing from alternative sources have appeared only in the last fifty years.

In the early seventies of the last century, the first global energy crisis occurred. The search for economical heating methods has led to the creation of devices capable of collecting energy from the environment, concentrating it and directing it to heat the house.

As a result, a HP design was developed with several thermodynamic processes interacting with each other:

1. When the refrigerant from the compressor circuit enters the evaporator, the pressure and temperature of the freon drops almost instantly. The resulting temperature difference contributes to the extraction of thermal energy from the coolant of the external collector. This phase is called isothermal expansion.
2. Then adiabatic compression occurs - the compressor increases the pressure of the refrigerant. At the same time, its temperature rises to +70 °C.
3. Passing the condenser, freon becomes a liquid, since at increased pressure it gives off heat to the in-house heating circuit. This phase is called isothermal compression.
4. When the freon passes through the choke, the pressure and temperature drop sharply. Adiabatic expansion occurs.

Heating the internal volume of a room according to the HP principle is possible only with the use of high-tech equipment equipped with automation to control all of the above processes. In addition, programmable controllers regulate the intensity of heat generation according to fluctuations in outside air temperature.

Alternative fuel for pumps

There is no need to use carbon fuel in the form of firewood, coal, or gas to operate the HP. The source of energy is the heat of the planet scattered in the surrounding space, inside of which there is a constantly operating nuclear reactor.

The solid shell of continental plates floats on the surface of liquid hot magma. Sometimes it breaks out during volcanic eruptions. Near the volcanoes there are geothermal springs, where you can swim and sunbathe even in winter. A heat pump can collect energy almost anywhere.

To work with various sources of dissipated heat, there are several types of heat pumps:

1. "Air-to-air." Extracts energy from the atmosphere and heats the air masses indoors.
2. "Water-air". Heat is collected by an external circuit from the bottom of the reservoir for subsequent use in ventilation systems.
3. "Ground-water". Heat collection pipes are located horizontally underground below the freezing level, so that even in the most severe frost they can receive energy to heat the coolant in the heating system of the building.
4. "Water-water." The collector is laid out along the bottom of the reservoir at a depth of three meters, the collected heat heats the water circulating in the heated floors inside the house.

There is an option with an open external collector, when you can get by with two wells: one for collecting groundwater, and the second for draining back into the aquifer. This option is only possible if the quality of the liquid is good, because the filters quickly become clogged if the coolant contains too many hardness salts or suspended microparticles. Before installation, it is necessary to do a water analysis.

If a drilled well quickly silts up or the water contains a lot of hardness salts, then stable operation of the HP is ensured by drilling more holes in the ground. The loops of the sealed outer contour are lowered into them. Then the wells are plugged using plugging made from a mixture of clay and sand.

Using dredge pumps

You can extract additional benefit from areas occupied by lawns or flower beds using ground-to-water HP. To do this, you need to lay pipes in trenches to a depth below the freezing level to collect underground heat. The distance between parallel trenches is at least 1.5 m.

In the south of Russia, even in extremely cold winters, the ground freezes to a maximum of 0.5 m, so it is easier to completely remove the layer of earth at the installation site with a grader, lay the collector, and then fill the pit with an excavator. Shrubs and trees, whose roots can damage the external contour, should not be planted in this place.

The amount of heat received from each meter of pipe depends on the type of soil:

• dry sand, clay - 10–20 W/m;
• wet clay - 25 W/m;
• moistened sand and gravel - 35 W/m.

The area of ​​land adjacent to the house may not be sufficient to accommodate an external pipe register. Dry sandy soils do not provide sufficient heat flow. Then they use drilling wells up to 50 meters deep to reach the aquifer. U-shaped collector loops are lowered into the wells.

The greater the depth, the higher the thermal efficiency of the probes inside the wells increases. The temperature of the earth's interior increases by 3 degrees every 100 m. The efficiency of energy removal from a well collector can reach 50 W/m.

Installation and commissioning of HP systems is a technologically complex set of works that can only be performed by experienced specialists. The total cost of equipment and component materials is significantly higher when compared with conventional gas heating equipment. Therefore, the payback period for initial costs extends over years. But a house is built to last for decades, and geothermal heat pumps are the most profitable heating method for country cottages.

Annual savings compared to:

• gas boiler - 70%;
• electric heating - 350%;
• solid fuel boiler - 50%.

When calculating the payback period of a HP, it is worth taking into account the operating costs for the entire service life of the equipment - at least 30 years, then the savings will many times exceed the initial costs.

Water-to-water pumps

Almost anyone can place polyethylene collector pipes at the bottom of a nearby reservoir. This does not require much professional knowledge, skills, or tools. It is enough to evenly distribute the coils of the coil over the surface of the water. There must be a distance between the turns of at least 30 cm, and a flooding depth of at least 3 m. Then you need to tie the weights to the pipes so that they go to the bottom. Substandard brick or natural stone are quite suitable here.

Installing a water-to-water HP collector will require significantly less time and money than digging trenches or drilling wells. The cost of purchasing pipes will also be minimal, since heat removal during convective heat exchange in an aquatic environment reaches 80 W/m. The obvious benefit of using HP is that there is no need to burn carbon fuel to produce heat.

An alternative method of heating a home is becoming increasingly popular, as it has several more advantages:

1. Environmentally friendly.
2. Uses a renewable energy source.
3. After commissioning is completed, there are no regular costs of consumables.
4. Automatically adjusts the heating inside the house based on the outside temperature.
5. The payback period for initial costs is 5–10 years.
6. You can connect a boiler for hot water supply to the cottage.
7. In summer it works like an air conditioner, cooling the supply air.
8. The service life of the equipment is more than 30 years.
9. Minimum energy consumption - generates up to 6 kW of heat using 1 kW of electricity.
10. Complete independence of heating and air conditioning of the cottage in the presence of an electric generator of any type.
11. Adaptation to the “smart home” system for remote control and additional energy savings is possible.

To operate a water-to-water HP, three independent systems are required: external, internal and compressor circuits. They are combined into one circuit by heat exchangers in which various coolants circulate.

When designing a power supply system, it should be taken into account that pumping coolant through the external circuit consumes electricity. The longer the length of the pipes, bends, and turns, the less profitable the VT. The optimal distance from the house to the shore is 100 m. It can be extended by 25% by increasing the diameter of the collector pipes from 32 to 40 mm.

Air - split and mono

It is more profitable to use air HP in the southern regions, where the temperature rarely drops below 0 °C, but modern equipment can operate at -25 °C. Most often, split systems are installed, consisting of indoor and outdoor units. The external set consists of a fan blowing through the radiator grille, the internal set consists of a condenser heat exchanger and a compressor.

The design of split systems provides for reversible switching of operating modes using a valve. In winter, the external unit is a heat generator, and in summer, on the contrary, it releases it to the outside air, working like an air conditioner. Air heat pumps are characterized by extremely simple installation of the external unit.

Other benefits:

1. The high efficiency of the outdoor unit is ensured by the large heat exchange area of ​​the evaporator radiator grille.
2. Uninterrupted operation is possible at outdoor temperatures down to -25 °C.
3. The fan is located outside the room, so the noise level is within acceptable limits.
4. In summer, the split system works like an air conditioner.
5. The set temperature inside the room is automatically maintained.

When designing the heating of buildings located in regions with long and frosty winters, it is necessary to take into account the low efficiency of air heaters at subzero temperatures. For 1 kW of consumed electricity there is 1.5–2 kW of heat. Therefore, it is necessary to provide additional sources of heat supply.

The simplest installation of VT is possible when using monoblock systems. Only the coolant pipes go inside the room, and all other mechanisms are located outside in one housing. This design significantly increases the reliability of the equipment and also reduces noise to less than 35 dB - this is at the level of a normal conversation between two people.

When installing a pump is not cost-effective

It is almost impossible to find free plots of land in the city for the location of the external contour of a ground-to-water HP. It is easier to install an air source heat pump on the external wall of the building, which is especially beneficial in the southern regions. For colder areas with prolonged frosts, there is a possibility of icing of the external radiator grille of the split system.

High efficiency of HP is ensured if the following conditions are met:

1. The heated room must have insulated external enclosing structures. The maximum amount of heat loss cannot exceed 100 W/m2.
2. TN is able to work effectively only with an inertial low-temperature “warm floor” system.
3. In the northern regions, HP should be used in conjunction with additional heat sources.

When the outside air temperature drops sharply, the inertial circuit of the “warm floor” simply does not have time to warm up the room. This happens often in winter. During the day the sun was warm, the thermometer showed -5 °C. At night, the temperature can quickly drop to -15 ° C, and if a strong wind blows, the frost will be even stronger.

Then you need to install regular batteries under the windows and along the outer walls. But the temperature of the coolant in them should be twice as high as in the “warm floor” circuit. A fireplace with a water circuit can provide additional energy in a country cottage, and an electric boiler can provide additional energy in a city apartment.

It remains only to determine whether the HP will be the main or supplementary heat source. In the first case, it must compensate for 70% of the total heat loss of the room, and in the second - 30%.

Video

The video provides a visual comparison of the advantages and disadvantages of various types of heat pumps and explains in detail the structure of the air-water system.

Evgeniy AfanasyevChief Editor

Author of the publication 05.02.2019

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