Thermal working principle. Heat pump heating system. Efficiency limits of heat pumps
Let's try to explain in the language of a common man in the street what is “ HEAT PUMP«:
Heat pump Is a special device that combines a boiler, a hot water supply and an air conditioner for cooling. The main difference heat pumpfrom other heat sources is the possibility of using renewable low-grade energy taken from the environment (land, water, air, wastewater) to cover heat needs during the heating season, heating water for hot water supply and cooling the house. Therefore, the heat pump 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 - a closed circulation system, which serves to transfer heat from the ground, water or air to the heat pump.
- secondary circuit - a closed system that serves to transfer heat from the heat pump to the heating system, hot water supply or ventilation (inflow heating) in the house.
How the heat pump works similar to the work of an ordinary refrigerator, just the opposite. The refrigerator removes heat from food products and transfers it to the outside (to the radiator located on its rear wall). A heat pump, on the other hand, transfers the heat stored in soil, earth, water, groundwater or air to your home. Like the refrigerator, this energy efficient heat generator has the following main elements:
- condenser (a heat exchanger in which heat is transferred from the refrigerant to the elements of the room heating system: low-temperature radiators, fan coil units, warm floor, radiant heating / cooling panels);
- throttle (a device that serves to reduce pressure, temperature and, as a result, to close the heating cycle in the heat pump);
- an evaporator (a heat exchanger in which heat is taken from a low-temperature source to a heat pump);
- a compressor (a device into which the pressure and temperature of refrigerant vapors increases).
Heat pump equipped in such a way as to make the heat move in different directions. For example, when a house is heated, heat is taken from some cold external source (land, river, lake, outside air) and transferred to the house. To cool (air-condition) a house, heat is taken from the warmer air in the house and transferred to the outside (dumped). 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 from the upper level to the lower level.
Today, the most common are vapor compression heat pumps. The principle of their action is based on two phenomena: first, the absorption and release of heat by the liquid when changing aggregate state - evaporation and condensation, respectively; secondly, the change in the evaporation (and condensation) temperature when the pressure changes.
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 the heat of 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 the condenser, where at high pressure condenses at more high temperature, giving off the heat of condensation to the heat receiver (for example, the heat carrier of the heating system). From the condenser, the working fluid through the throttle again enters the evaporator, where its pressure decreases, and the refrigerant boiling process begins anew.
Heat pump able to extract heat from various sources, for example, air, water, soil. Also, it can release heat into air, water or earth. A warmer environment that absorbs heat is called a heat sink.
Heat pump X / Y uses medium X as a heat source, heat carrier Y. Distinguish between pumps "Air-water", "soil-water", "water-water", "air-air", "soil-air", "water-air".
Heat pump "soil-water":
Air-to-water heat pump:
In most cases, the regulation of the heating system using heat pumps is carried out by turning it on and off according to the signal from the temperature sensor, which is installed in the receiver (when heating) or the source (when cooling) heat. The heat pump is usually adjusted by changing the cross-section of the throttle (thermostatic expansion valve).
Like refrigeration machine, a heat pump uses mechanical (electrical or other) energy to implement a thermodynamic cycle. This energy is used to drive the compressor (modern heat pumps up to 100 kW are equipped with highly efficient scroll compressors).
(transformation ratio or efficiency) of a heat pump is the ratio of the amount of heat 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 fluctuates for various heat pump systems in the range from 2.5 to 7, that is, per 1 kW of consumed electrical energy, the heat pump generates 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 minimum of expensive electrical energy.
The energy saving and efficiency of a heat pump primarily depends on the where do you decide to draw low-temperature heat, in the second - from the method of heating your house (water or air) .
The fact is that the heat pump works as a “transshipment base” between two heating circuits: one heating at the inlet (on the evaporator side) and the second, heated at the outlet (condenser).
All types of heat pumps are characterized by a number of features that you need to keep in mind when choosing a model:
Firstly, a heat pump is only justified in a well-insulated house. The more warm house, the greater the benefit when using this device. As you understand, heating the street with a heat pump, collecting crumbs of heat from it is not entirely reasonable.
Secondly, the greater the temperature difference between the coolants in the input and output circuits, the lower the heat conversion coefficient (COP), that is, the lower the savings in electrical energy. That is why more profitable connection of the heat pump to low-temperature heating systems... First of all, we are talking about heating with water underfloor heating 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. Heat pumps of geothermal type
4. Advantages and disadvantages of heat pumps
One of the highly efficient ways to heat a country house is the use of heat pumps.
The principle of operation of heat pumps is based on the extraction of thermal energy from soil, reservoirs, groundwater, air. Heat pumps for home heating do not have a harmful effect on the environment. You can see how such heating systems look in the photo.
Such an organization of home heating and hot water supply has been possible for many years, but it has begun to spread quite recently.
Features of heat pumps
The principle of operation of such devices is similar to refrigeration equipment.
Heat pumps take heat, accumulate 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 heat with a low potential.
The constant increase in the cost of electricity and the imposition of stringent requirements for environmental protection are 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 heat energy received is several times higher than the consumed electricity (more: "Economical heating with electricity: pros and cons").
If we compare heating with gas, solid or liquid fuels, with heat pumps, then the latter will turn out to be more economical. However, the very arrangement of the heating system with such units is much more expensive.
Heat pumps consume the energy required to operate the compressor. Therefore, this type of building heating is not suitable if there are frequent power supply problems in the area.
Heating a private house with a heat pump can have different efficiency, its main indicator is the conversion of heat - the difference between consumed electricity and received heat.
There is always a difference between the evaporator and condenser temperatures.
The larger it is, the lower the efficiency of the device. For this reason, using a heat pump requires a significant 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 larger dimensions have a much higher cost.
Heating with a heat pump is found in many developed countries.
Moreover, they are also used to heat multi-apartment 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. They usually 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 ambient air.
Geothermal uses the thermal energy of the earth, ground and surface waters (in more detail: "Geothermal heating: the principle of work by examples"). Heat pumps for waste heat take energy from sewage, central heating - these devices are mainly used to heat industrial buildings.
This is especially beneficial if there are sources of heat that must be utilized (read also: "Using the heat of the earth to heat a house").
Heat pumps are also classified according to the type of heat carrier; they can be air, soil, water, as well as their combinations.
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 in the presence of a significant amount of clean water, given the fact that its consumption will not harm the environment and will not contradict the current legislation. Therefore, before using a heating system that receives energy from groundwater, you should consult the relevant organizations.
Closed systems are divided into several types:
- Geothermal with a horizontal arrangement means laying a collector in a trench below the depth of soil freezing.
This is about 1.5 meters. The collector is laid in rings in order to reduce the excavation area to a minimum and to provide a sufficient contour in a small area (read: "Geothermal heat pumps for heating: system design principle").
This method is only suitable if there is sufficient free space available on the site.
- Vertical geothermal structures provide for the placement of a reservoir in a well with a depth of 200 meters. This method is used when it is not possible to locate the heat exchanger over a large area, which is necessary for a horizontal well.
Also, geothermal systems with vertical wells are made in the case of an uneven landscape of the site.
- Geothermal water means placing a collector in a reservoir to a depth below the freezing level. Laying is done in rings. Such systems cannot be used if the body of water is small or not deep enough.
It must be borne in mind that in the event of freezing of the reservoir at the level where the collector is located, the pump will not be able to work.
Heat pump air water - features, details on the 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.
Also, heat pumps are economical, unlike other heaters that consume electricity. Thus, the amount of generated heat 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 costs during operation are minimized - you have to pay only for the electricity consumed.
The use of heat pumps also makes it possible to cool the premises in the summer - this is possible thanks to the connection to the fan coil collector and the cold ceiling system.
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 cost and significant costs of installation work. It is unlikely that it will be possible to design heating with a heat pump with your own hands 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 will also cost a lot;
- the price of heat pumps is several times higher than the cost of boilers operating on gas, solid or liquid fuels. A lot of money will have to be paid for drilling wells.
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 money only if a system with a horizontal heat exchanger is created, if you dig trenches yourself, but this will take more than one day. As for the operation, the equipment turns out to be very profitable.
Heat pumps are an economical way to heat buildings in an environmentally friendly way.
They may not be widely adopted due to their high cost, but this may change in the future. In developed countries, many owners of private houses use heat pumps - there the government encourages environmental concern, and the cost of this type of heating is low.
A ground source or ground source heat pump is one of the most energy efficient alternative energy systems. Its operation does not depend on the season and the ambient temperature, as for an air-to-air pump, it is not limited by the presence of a reservoir or a well with groundwater next to the house, like a water-water system.
A soil-to-water heat pump, which uses heat taken from the soil to heat the heat carrier in the heating system, has the highest and constant efficiency, as well as the energy conversion coefficient (COP).
Its value is 1: 3.5-5, that is, each kilowatt of electricity consumed for the operation of the pump is returned by 3.5-5 kilowatts of thermal energy. Thus, the heating power of the dredge pump allows it to be used 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 dredge pump requires a soil circuit with a circulating coolant to extract the heat from the earth.
There are two options for its placement: a horizontal soil reservoir (a pipe system at a shallow depth, but a sufficiently large area) and a vertical probe placed in a borehole from 50 to 200 m deep.
The efficiency of heat exchange with the soil depends significantly on what kind of soil lies - moisture-filled soil gives off much more heat than, for example, sandy soil.
The most common pumps operating on the ground-water principle, in which the coolant stores the energy of the soil and, as a result of passing through the compressor and the heat exchanger, transfers it to the water as a heat carrier in the heating system. The prices for dredge pumps of this type correspond to their high efficiency and productivity.
Submersible dredge pump
Any sophisticated high-tech equipment, such as ground pumps GrAT, as well as ground heat pumps require the attention of professionals.
Heat pump
We offer a full range of services for the implementation, installation and maintenance of heating and hot water supply systems based on heat pumps.
Today, European countries and China are especially popular among the manufacturing countries of such units on the market.
The most famous heat pump models are: Nibe, Stiebel Eltron, Mitsubishi Zubadan, Waterkotte. The domestic ground source heat pump is also in demand.
Our company prefers to work only with equipment from reliable European manufacturers: Viessmann and Nibe.
The heat pump extracts the stored 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 earth's interior - transfers and converts into energy of higher temperatures.
Heat pump - highly economical, environmentally friendly technology for heating and comfort
Thermal energy exists around us, the problem is how to extract it without spending significant energy resources.
Heat pumps extract stored 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 earth's interior - transfers and converts into energy of higher temperatures.
The choice of the optimal heat source depends on many factors: the size of the energy needs of your home, the installed heating system, the natural conditions of the region of your residence.
The device and principle of operation of the heat pump
The heat pump functions like a refrigerator - just the opposite.
The refrigerator transfers heat from the inside to the outside.
A heat pump transfers heat stored in the air, soil, subsoil or water to 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 liquid in one part of the cycle and gas in the other.
Earth's interior as a deep heat source
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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 investment level is quite high, but in return you will get a safe in operation, with minimum service requirements, an alternative heating system with the longest possible service life. Heat conversion factor (see. p. 6) high, reaches 3. The installation does not require much space and can be installed on a small area of \u200b\u200bland. Post-drilling recovery work is negligible, and the impact of the drilled well on the environment is minimal. The groundwater level is not affected since groundwater is not consumed. Thermal energy is transferred to a convection hot water heating system and used for hot water supply. |
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Ground heat - nearby energy
Heat accumulates in the surface layer of the earth during the summer.
The use of this energy for heating is advisable for buildings with high energy consumption. The greatest amount of energy is extracted from soil with a high moisture content.
Ground heat pump
Water heat sources
The sun heats the water in the seas, lakes and other water sources.
Solar energy is stored 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, and 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 even slightly higher,
than the water temperature.
It is important that the hose is equipped with a weight to prevent
ascent of the hose to the surface. The lower it lies, the lower the risk of damage.
The water source as a heat source is very efficient for buildings with relatively high heat energy requirements.
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 a heat source
After passing through the heat pump, the water can be transported to the branch channel or well. This solution can lead to an undesirable decrease in the groundwater level, as well as reduce the operational reliability of the installation and have a negative impact on nearby wells.
Now this method is used less and less.
Groundwater can also be returned to the ground by partial or complete infiltration.
Such a profitable heat pump
Heat conversion factorThe higher the efficiency of the heat pump, the more profitable it is. Efficiency is determined by the so-called heat conversion ratio or temperature conversion ratio, 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 thermal transformation ratio is 3. This means that the heat pump supplies 3 times more energy than it consumes. In other words, 2/3 was received "free" from the heat source. How to make a heat pump for heating a house with your own hands: the principle of operation and schemesThe higher the energy demand of your home, the more you save money. Note The value of the coefficient of temperature transformation is influenced by the presence / neglect in the calculations of the parameters of additional equipment (circulation pumps), as well as different temperature conditions. The lower the temperature distribution, the higher becomes the coefficient of temperature transformation, heat pumps are most effective in heating systems with low temperature characteristics. |
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When selecting a heat pump for your heating system, it is unprofitable to orient 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 the available boiler equipment or a peak closer, which is supplied with the heat pump. |
Comparison of the costs of installing a heating system for an individual house based on a heat pump and an oil boiler.
Let's take a house with an area of \u200b\u200b150-200 sq.m.
The most common variant of a modern country house for permanent use today.
The use of modern building materials and technologies ensures the value of the building's heat loss at the level of 55 W / sq.
To cover the total needs for heat energy consumed for 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 itself or the diesel fuel boiler 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 the installation of a turnkey heating system based on a liquid fuel boiler, which are absent in the case of a heat pump:
air vent filter, fix pack, safety group, burner, boiler piping system, control panel with weather-dependent automation, emergency electric boiler, fuel tank, chimney, boiler.
All this adds up to no less than 8000-9000 euros. Taking into account the need for the installation of the boiler room itself, the cost of which, taking into account all the requirements of the supervisory authorities, amounts to several thousand euros, we come to a paradoxical at first glance conclusion, namely, the practical comparability of the initial capital costs when installing a "turnkey" heating system based on a heat pump and an oil-fired boiler.
In both cases, the cost is close to 15 thousand euros.
Considering the following undeniable advantages of a heat pump, such as:
Profitability. At a cost of 1 kW of electricity, 1 ruble 40 kop, 1 kW of thermal power will cost us no more than 30-45 kopecks, while 1 kW of thermal energy from the boiler will cost 1 ruble 70 kopecks (with a diesel fuel price of 17 rubles / l);
Ecology. An environmentally friendly heating method both for the environment and for people in the room;
Security. No open flame, no exhaust, no soot, no diesel smell, no gas leakage, no fuel oil spill.
No fire hazardous storage facilities for coal, firewood, fuel oil or diesel fuel;
Reliability. A minimum of moving parts with a long service life. Independence from the supply of fuel material and its quality. Virtually maintenance-free. The service life of the heat pump is 15 - 25 years;
Comfort. The heat pump works silently (no louder than the refrigerator);
Flexibility. The heat pump is compatible with any circulating heating system, and its modern design allows it to be installed in any room;
an increasing number of individual house owners are choosing a heat pump for heating both in new construction and when modernizing 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 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 - a throttle, an expander or a vortex tube, connected by a pipeline (Fig. 16).
Schematically, a heat pump can be represented as a system of three closed circuits: in the first, external, a heat exchanger circulates (a heat carrier that collects the heat of the environment), in the second - a refrigerant (a substance that evaporates, taking away the heat of the heat sink, and condenses, giving off heat to the heat receiver) , 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 an anti-freeze liquid circulates. It should be noted that both natural heat (outside air; heat of ground, artesian and thermal waters; waters of rivers, lakes, seas and other non-freezing natural reservoirs) and man-made origin (industrial discharges, treatment facilities, water treatment plants) can act as a source of low-potential energy. heat from power transformers and any other waste heat).
The temperature required for pump operation is usually 5-15.
In the second circuit, where the refrigerant circulates, there are built-in heat exchangers - an evaporator and a condenser, as well as devices that change the pressure of the refrigerant - a throttle spraying it in the liquid phase (narrow calibrated hole) and a compressor that squeezes it in the gaseous state.
Working cycle. 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.
Further, the gas, which has become the refrigerant, is sucked into the compressor, compressed and heated, pushed into the condenser. The condenser is the heat transfer unit of the heat pump: here the heat is taken up by the water in the heating circuit system. In this case, the gas is cooled and condensed in order to undergo a discharge in the expansion valve and return to the evaporator. After that, 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 spent, the heat pump generates 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 larger 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 seeking to cool it down too much.
Types of heat pumps.
Heat pumps are of two main types - closed loop and open loop.
Open circuit pumps ground source water is used as a heat source - it is pumped through a drilled well into a heat pump, where heat exchange takes place, and the cooled water is removed back into the underwater horizon through another well.
This type of pump is beneficial in that the groundwater maintains a stable and sufficiently high temperature all year round.
Closed loop pumps there are several types: verticaland r 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 runs along the bottom of a nearby lake or pond.
The depth of pipe laying underground 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, which are not always available in the developed area.
The main one is that the pipes should be laid so as not to interfere with the growth of trees, agricultural work, so that there is a low probability of damage to underwater pipes during agricultural or other activities.
Figure: 17. Surface geothermal heat transfer system
Vertical heat exchanger pumps include an outer contour, dug deep into the ground - 50-200 m.
It 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 is 15-20 degrees, and with increasing depth it only grows.
Air conditioning with heat pumps.One of the important qualities of heat pumps is the ability to switch from heating in winter to air conditioning in summer: only fan coils are used instead of radiators.
A fan coil unit is an indoor unit, which is supplied with heat or coolant and air driven by a fan, which, depending on the water temperature, is either heated or cooled.
Includes: heat exchanger, fan, air filter and control panel.
Since fan coil units can work 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 operating only for cooling);
- S4 - pipe - when the coolant (for example, ethylene glycol) cannot mix with the coolant (water).
The power of fan coil units for cold conditions 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 speeds.
Perspectives.The widespread use of heat pumps is hindered by a lack of public awareness. Potential buyers are intimidated by the rather high initial costs: the cost of the pump and installation of the system is $ 300-1200 per 1 kW of the required heating power. But a competent calculation convincingly proves the economic feasibility of using these installations: the investment pays off, according to rough estimates, in 4-9 years, and heat pumps serve for 15-20 years before overhaul.
Economical home heating systems are replacing traditional types of heating using gas, solid fuels and electricity. An air source heat pump is one of the most popular alternative solutions.
Among the advantages, one can note the low, in comparison with geothermal installations, cost, the possibility of using it when creating new heating systems and renovating old ones. The heat pump is especially in demand in "passive house" systems - residential premises designed according to the principle of minimum heat consumption and the introduction of energy-saving technologies.
What is an air heat pump
The simplest heat pump was designed back in 1852 and received the name “heat multiplier”. Lord Kelvin discovered the fundamental operating principles that formed the basis of all modern heating equipment.According to the laws of physics, heat is transferred from a heated body to something that has a lower temperature. But, the reverse process is possible, provided that additional energy is used for this.
A little later, the principle of the inverse Carnot cycle was discovered. The substance, upon evaporation, absorbs heat, and after condensation on the surface, gives it off. It is this law that underlies refrigerators and air conditioners. The low-temperature air heat pump works like these household appliances, only in the "opposite direction".
Some air conditioner manufacturers use this principle by offering the consumer air conditioners capable of heating a room. But air conditioning systems have low efficiency at negative temperatures, since the main purpose of equipment is cooling, not heating.
Low temperature air source heat pumps for home heating work using this physical law. How is heating done in practice?
- Any body, even a cooled one, has high or low potential energy. Even at subzero temperatures, the air contains a certain amount of heat. At -15 ° C, warmer than at -25 ° C. At -5 ° C, more heat is in the air. The principle of operation of an air heat pump allows you to extract that small amount of heat energy that remains in the winter season and transfer it to the room.
- In the outdoor unit, installed outdoors, there is a coil with an evaporator. Freon circulates inside the circuit - a liquid that freely passes into a gaseous state and back. Freon evaporates, while the heat is absorbed, which remains even at negative temperatures.
- The gas enters the compressor. The compressor creates high pressure and conditions for converting freon back into liquid.
- Under pressure, freon heats up and enters the condenser. In the block, the gas finally becomes a liquid, while giving off all the heat that it received in the outdoor block installed on the street.
- Freon, in a closed loop, returns back to the evaporator.
There are several types of air heat pumps, which differ in the principle used for space heating.
Air / water heat pumps
Household heating and hot water supply systems based on air heat pumps are very effective for use in the temperate latitudes of the Russian Federation. Average COP (conversion factor) 3. It turns out that for every 1 kW spent, there is 3 kW of produced thermal energy.The principle of operation is the same as in pumps of other modifications, but with certain differences:
- The condenser is located inside the storage tank connected to the heating and hot water supply system.
- The heat released during the condensation of freon is used for indirect heating of the coolant.
- With the help, the heated coolant enters the DHW system and heating.
The intensity of heating the coolant varies from + 30 ° C to + 60 ° C. At temperatures below -15 ° C, combined heat supply with an air heat pump is turned on, which is indispensable in cold climates. Any boiler (electricity, gas, firewood) compensates for the lack of heat.
Since the installation of the outdoor unit is carried out outdoors, an additional advantage will be the anti-freeze or thaw function.
Air heating heat pumps
Air heating heat pumps are used to heat individual rooms. The principle of operation is largely similar to that used by a fan heater, only a condenser plays the function of a heating coil.The casing of the indoor unit of the heat pump is similar to an air conditioner and can also operate for air heating and cooling.
The consumer is offered various solutions to the heating issue:
- Installation of separate independent heaters.
- Installation of several heat pumps integrated into a single network.
- Maximum efficiency - no need for preheating the coolant leads to a more economical power consumption. The air heats up only to a temperature of 20-40 ° C, and this, in turn, provides a higher COP coefficient equal to 4.
- Fast heating of the building - warm air begins to flow into the room a few seconds after switching on.
- Versatility - the equipment can be used as an air conditioner in summer. The basic configuration includes a room cooling function.
When a negative temperature critical for operation is reached, the reserve heat source is automatically turned on when using an air HP. Thus, it is possible to compensate for the lack of thermal energy.
What is the difference between an air conditioner and an air HP
Indeed, the supply of heat to premises with air heat pumps in cold climates is in many ways similar to heating with conventional air conditioners. Internal and external blocks of a similar structure are used. Even in the internal structure there are many similarities. The difference is that indoor air heaters are more efficient in heating than in cooling, and air conditioners, on the contrary.You can feel the difference by comparing some of the characteristics of the equipment. The air conditioner stops working for heating at a temperature of about -5 ° C. The operating mode of heat pumps is from -25 ° C to + 45 ° C.
Since there is a tendency to improve air heat pumps for "passive" houses, soon, for a wide range of consumers, equipment models that can remain operational when the temperature drops to -32 ° C will become available.
The difference between an air HP and an air conditioner lies in different technical characteristics, although there are many similarities between them.
How to choose an air heat pump
The choice of an air TN is not as difficult as it might seem at first glance. When choosing a suitable model, you should focus on the following parameters:- Heating type.
- Heated area.
- Manufacturer.
Which brand to choose an air-type heat pump
If we analyze the reviews about air heat pumps, it is quite easy to determine the equipment manufacturers that are in greatest demand among the domestic consumer:- Stiebel Eltron is a German company that began its journey with the invention of the boiler. Over time, the product range has been constantly expanding. Today, Stiebel Eltron is a leader in the production of water heating and heating technology. The company offers two types of heat pumps: geothermal and air, which work to heat the heat carrier and air.
- Is another German manufacturer with over 30 years of experience in the production of air pumps. The Viessmann stations that are connected to the water heating circuit deserve the greatest praise. The advantages are the presence of weather-dependent control sensors and many additional functions available in the basic configuration.
- Mitsubishi is a Japanese corporation that pioneered Zubadan technology. The solution allowed to increase the COP (which is the highest among similar equipment) and expand the scope of application. Mitsubishi was one of the first to offer the consumer heating air conditioners and air source heat pumps. New technologies are constantly being introduced to increase the scope of products.
- - the company has developed a whole series of economical geoTHERM equipment. The range includes equipment that extracts heat from earth, water, air and sunlight. Vaillant products are maximally adapted for use in the Russian Federation.
The cost of air TN with installation
The most expensive are heat pumps that heat a room with a coolant. The equipment will cost about 80 thousand rubles. (capacity 4.5 kW), up to 800 thousand rubles. (18.5 kW). Heat pumps for air heating will cost from 50 thousand rubles. (for 4 kW) up to 120 thousand rubles. (for 8 kW).The cost of installing an air heating unit is calculated individually, based on the technical parameters of the room and other factors.
The service life of the equipment is at least 20 years. The installed equipment pays for itself after 3-5 heating seasons, depending on the intensity of operation.
Pros and cons of using air heat pumps
Literally 5 years ago, the domestic consumer had practically no experience in heating buildings in winter using air heat pumps. I had to be content with statements and extremely positive comments posted on the websites of various manufacturers of equipment, which did not give a clear idea of \u200b\u200bthe capabilities of the equipment. Since then, a certain experience of use has appeared, which made it possible to identify not only the advantages, but also the disadvantages of air TN.Benefits
- The advantages of using air-water heat pumps - the main advantage is complete independence from gas heating. In some regions of the Russian Federation, just bringing the pipeline to the house is more expensive than buying and installing a heat pump. No commissioning authorization required.
- The systems are designed to be installed in a "passive house" environment. Therefore, they were originally designed for economical heating of the house and heating hot water. For 1 kW of consumed electricity, heat generation is 3-5 kW. A simple calculation of costs when using a heat pump will show that a full payback of the equipment is achieved within 3-5 years.
- The operation of the pump does not negatively affect human health. To ensure hygienic conditions, in systems using the principle of air heating, it is sufficient to clean the filters from time to time.
disadvantages
- The high cost of equipment - a system with a capacity sufficient to heat a residential building will cost 800-1200 thousand rubles, which is an unaffordable amount for most buyers.
- Dependence on ambient temperature. The features of autonomous heating of a house with an air heat pump are directly related to the total amount of heat energy received. The lower the outside temperature, the worse the pump works. Starting from -15 ° C, you will have to connect a backup heat source.
Considering that in most territories of the Russian Federation the average temperature regime is higher, then the expediency of this installation becomes clear. The optimal climatic zones for the use of air heating heat pumps are parts of Russia with a temperate climate and an average temperature in winter of at least -15 ° C.
Recently, manufacturers have somewhat reduced the cost of heating plants, which allowed even more buyers to appreciate the dignity of the stations. If the trend continues, an increased demand for heat pumps can be expected.
Paying for electricity and heat supply becomes more difficult every year. When building or buying a new home, the problem of efficient 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 get heat for decades later at the lowest cost.
The most cost-effective option in some cases is a heat pump for heating a house, the principle of operation 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 in another place.
What is a heat pump (HP)
Take a typical household refrigerator as an example. Inside the freezer, water quickly turns to ice. Outside, there is a hot-to-touch grille. From it, the heat collected inside the freezer is transferred to the room air.
The same thing, but in reverse order, is done by TH. The radiator grille located outside the building is much larger to collect enough heat from the environment to heat the home. The coolant inside the radiator or collector tubes releases energy to the heating system inside the house and then heats up again outside the house.
Device
Providing a house with heat is a more difficult technical task than cooling a small volume of a refrigerator, where a compressor with freezing and radiator circuits is installed. The air HP is almost as simple as it receives heat from the atmosphere and heats up the internal air. Only fans are added to blow the circuits.
It is difficult to obtain a large economic effect from the installation of 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 consumed by an air-to-air device, only 2 kW of heat can be obtained, and the water-to-water heat pump gives 5–6 kW. The HP can guarantee such a high coefficient of performance (COP).
The composition of the pump components:
- House heating system, for which it is better to apply warm floors.
- Hot water boiler.
- A condenser that transfers the energy collected externally to the heating medium of the building's heating system.
- An evaporator that takes energy from the heat carrier, which circulates in the external circuit.
- A compressor that pumps refrigerant from an evaporator, converting it from a gaseous to a liquid state, increasing pressure and cooling in the condenser.
- Expansion valve installed before the evaporator to regulate the refrigerant flow.
- 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 external radiator grille, blown by a fan, serves as a circuit.
- Pumps pump coolant through pipes outside and inside the house.
- Automation for control according to a given program of space heating, which depends on changes in the outside air temperature.
Inside the evaporator, the coolant from the external pipe register is cooled, giving off heat to the refrigerant in the compressor circuit, and then pumped through the pipes at the bottom of the reservoir by a pump. There it heats up and the cycle repeats again. The condenser transfers heat to the heating system of the cottage.
Prices for different models of heat pumps
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 use of their works devoted to solving the problem of heating housing from alternative sources has 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 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:
- When the refrigerant in the compressor circuit enters the evaporator, the pressure and temperature of the freon drop almost instantly. The resulting temperature difference contributes to the selection of thermal energy from the coolant of the external collector. This phase is called isothermal expansion.
- Then adiabatic compression occurs - the compressor increases the refrigerant pressure. At the same time, its temperature rises to + 70 ° С.
- Passing the condenser, freon becomes a liquid, since at elevated pressure it gives off heat to the internal heating circuit. This phase is called isothermal compression.
- When the freon passes the throttle, the pressure and temperature drop sharply. Adiabatic expansion occurs.
Heating of the internal volume of the room according to the TH principle is possible only with the use of high-tech equipment equipped with automation to control all of the above processes. In addition, the programmable controllers adjust the heat generation rate according to the fluctuating outdoor temperature.
Alternative fuel for pumps
It is not at all necessary to use carbon fuel in the form of firewood, coal, gas for the HP operation. The source of energy is the heat of the planet dispersed in the surrounding space, inside which there is a constantly operating nuclear reactor.
The solid shell of the continental plates floats on the surface of hot liquid magma. Sometimes it breaks out during volcanic eruptions. There are geothermal springs near volcanoes, where you can swim and sunbathe even in winter. A heat pump is capable of harvesting energy almost everywhere.
There are several types of VTs to work with various sources of dissipated heat:
- Air-to-air. Extracts energy from the atmosphere and heats indoor air masses.
- "Water-air". Heat is collected by an external circuit from the bottom of the reservoir for subsequent use in ventilation systems.
- "Ground-water". Pipes for collecting heat are located horizontally underground below the freezing level in order to receive energy even in the most severe frost to heat the coolant in the building's heating system.
- "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 warm floors inside the house.
There is an option with an open external collector, when you can get by with two wells: one for the intake of groundwater, and the other for draining back into the aquifer. This option is possible only if the quality of the liquid is good, because the filters quickly become clogged if there are too many hardness salts or suspended microparticles in the coolant. Before installation, it is imperative to make a water analysis.
If the drilled well is quickly silted up or the water contains a lot of hardness salts, then the stable operation of the HP is ensured by drilling more holes in the ground. Loops of a sealed external circuit are lowered into them. Then the wells are plugged with plugging from a mixture of clay and sand.
Using dredge pumps
You can get additional benefit from areas occupied by lawns or flower beds with the help of TH type "ground-water". To do this, it is necessary 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 remove the entire layer of earth at the installation site with a grader, lay the collector, and then fill the pit with an excavator. Shrubs and trees should not be planted in this place, the roots of which can damage the outer contour.
The amount of heat received from each meter of the pipe depends on the type of soil:
- dry sand, clay - 10–20 W / m;
- wet clay - 25 W / m;
- wet sand and gravel - 35 W / m.
The area of \u200b\u200bthe land adjacent to the house may not be enough to accommodate the external register of pipes. Dry sandy soils do not provide sufficient heat flow. Then they use drilling of wells up to 50 meters deep to reach the aquifer. U-shaped reservoir loops are lowered into the wells.
The deeper the depth, the higher the thermal efficiency of the probes inside the wells increases. The temperature of the earth's interior rises by 3 degrees every 100 m. The efficiency of energy extraction from a downhole reservoir 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 accessories is much higher when compared with conventional gas heating equipment. Therefore, the payback period of the initial costs stretches over years. But the house is under construction for decades, and geothermal heat pumps are the most profitable way of heating for country cottages.
Annual savings versus:
- gas boiler - 70%;
- electric heating - 350%;
- solid fuel boiler - 50%.
When calculating the payback period of a heat pump, it is worth considering 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 great professional knowledge, skills, tools. It is enough to evenly distribute the turns of the coil over the water surface. There should be a distance of at least 30 cm between the turns, and the flooding depth should be at least 3 m. Then weights must be tied to the pipes so that they go to the bottom. Substandard brick or natural stone is quite suitable here.
The installation of a “water-to-water” type HP collector will take much 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 aqueous medium reaches 80 W / m. The obvious benefit of using HP is that you do not need to burn carbon fuel to generate heat.
An alternative way to heat a house is becoming more and more popular, since it has several more advantages:
- Environmentally friendly.
- Uses a renewable energy source.
- After the completion of commissioning, there are no regular expenditures of consumables.
- Automatically regulates the heating inside the house according to the outside temperature.
- The payback period for initial costs is 5–10 years.
- You can connect a boiler for hot water supply to the cottage.
- In summer it works as an air conditioner, cooling the supply air.
- The service life of the equipment is over 30 years.
- Minimum energy consumption - generates up to 6 kW of heat using 1 kW of electricity.
- Complete independence of heating and air conditioning of the cottage in the presence of an electric generator of any type.
- Adaptation to the “smart home” system for remote control, additional energy saving is possible.
Three independent systems are required for the operation of a water-to-water heat pump: an external, an in-house and a compressor circuit. They are combined into one circuit by heat exchangers in which various heat carriers circulate.
When designing the power supply system, it should be borne in mind that electricity is consumed for pumping the coolant through the external circuit. The longer the length of pipes, bends, bends, the less profitable the heat pump. The optimal distance from the house to the shore is 100 m. It can be lengthened 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 heat pumps in the southern regions, where the temperature rarely drops below 0 ° С, but modern equipment is capable of operating even at -25 ° С. Most often, split systems are installed, consisting of an indoor and outdoor unit. The outer set consists of a fan blowing over the radiator grille, the inner one consists of a condenser heat exchanger and a compressor.
The design of the split systems provides for reversible switching of operating modes using a valve. In winter, the outdoor unit is a heat generator, and in summer, on the contrary, it gives it to the outside air, working as an air conditioner. Air VTs are distinguished by extremely simple installation of an external unit.
Other benefits:
- The high efficiency of the outdoor unit is provided by the large heat exchange area of \u200b\u200bthe evaporator radiator grill.
- Uninterrupted operation is possible at ambient temperatures down to -25 ° C.
- The fan is located outside the room, so the noise level is within acceptable limits.
- In summer, the split system works like an air conditioner.
- The set indoor temperature 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 heating units at negative temperatures. 1 kW of consumed electricity accounts for 1.5–2 kW of heat. Therefore, it is necessary to provide for additional sources of heat supply.
The simplest installation of VT is possible in the case of using monoblock systems. Only tubes with a coolant enter the room, and all other mechanisms are located outside in the same 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 unprofitable
It is practically impossible to find free land plots in the city for the location of the external contour of the “ground-water” type HP. It is easier to install an air heat pump on the outer wall of the building, which is especially beneficial in the southern regions. For colder areas with prolonged frosts, there is a possibility of icing on the outer grille of the split system.
The high efficiency of the HP is provided under the following conditions:
- The room to be heated must have insulated external enclosing structures. The maximum value of heat losses cannot exceed 100 W / m 2.
- ТН is able to work effectively only with the inertial low-temperature system "warm floor".
- 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. In the afternoon, the sun warmed up, on the thermometer -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 it is necessary to install ordinary batteries under 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. Additional energy in a country cottage can be provided by a fireplace with a water circuit, and an electric boiler in a city apartment.
It remains only to determine whether the HP will be the main or complementary 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 different types of heat pumps, explains in detail the structure of the air-water system.
Evgeny Afanasievchief Editor
Author of the publication05.02.2019
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 heat pump's power comes from ambient heat in the form of diffused solar radiation. It is his pump that simply "pumps" from the street to the house. The operation of a heat pump is similar to that of a refrigerator, only the direction of heat transfer is different.
Simply put…
To chill a bottle of 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, give it away. The refrigerator transfers heat to a radiator, usually located on the back of the refrigerator. In this case, the radiator heats up, giving off its heat to the room. In fact, he heats the room. This is especially noticeable in small minimarkets in the summer, when several refrigerators are on in the room.
We offer to dream up. Suppose that we will constantly put warm objects in the refrigerator, and it will, by cooling them, heat the air in the room. Let's go to the "extremes" ... Place the refrigerator in the window opening with the open door of the "freezer" outward. The refrigerator radiator will be in the room. During operation, the refrigerator will cool the air outside, transferring the "taken" heat into the room. This is how the heat pump works, taking the dispersed heat from the environment and transferring it to the room.
Where does the pump get heat?
The principle of operation of a heat pump is based on the "exploitation" of natural low-grade heat sources from the environment.
They can be:
- just outside air;
- heat of reservoirs (lakes, seas, rivers);
- warmth of the ground, groundwater (thermal and artesian).
How does a heat pump and a heating system work with it?
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 takes heat from the surrounding space.
Getting into the heat pump, or rather its evaporator, the heat carrier gives on average 4 to 7 ° C to the heat pump coolant. And its boiling point is -10 ° C. As a result, the refrigerant boils with a subsequent transition to a gaseous state. The coolant of the external circuit, already cooled, goes to the next "loop" through 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 "boiled" in the evaporator is piped to the compressor powered by electricity. This "hard worker" compresses the gaseous refrigerant to a high pressure, which, accordingly, leads to an increase in its temperature.
Now the hot gas then enters another heat exchanger called a condenser. Here, the heat of the refrigerant is transferred to the room air or heat carrier, which circulates along the internal circuit of the heating system.
The refrigerant cools down while simultaneously becoming a liquid. It then passes through a capillary pressure reducing valve where it "loses" pressure and re-enters the evaporator.
The loop is closed and ready to repeat!
Approximate calculation of the heating capacity of the installation
Within an hour, up to 2.5-3 m 3 of coolant flows through the pump through the external collector, which the earth can heat by ∆t \u003d 5-7 ° C.
To calculate the thermal power of such a circuit, use the formula:
Q \u003d (T_1 - T_2) * V_heat
V_heat - volumetric flow rate of the heat carrier per hour (m ^ 3 / hour);
T_1 - T_2 - temperature difference between inlet and inlet (° C).
Varieties of heat pumps
Heat pumps are distinguished by the type of dissipated heat used:
- ground-water (using closed ground loops or deep geothermal probes and a water heating system of the room);
- water-water (open wells are used 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 air-type heating systems);
- (use of the dissipated heat of external air masses complete with an air heating system at home).
Advantages and advantages of heat pumps
Cost effective efficiency. The principle of operation of a heat pump is based not on production, but on the transfer (transportation) of thermal energy, then it can be argued that its efficiency is greater than unity. What nonsense? - you say. In the subject of heat pumps, there is a quantity - the coefficient of conversion (transformation) of heat (CHT). It is by this parameter that aggregates of this type are compared with each other. Its physical meaning is to show the ratio of the amount of heat received to the amount spent for this energy. For example, with KPT \u003d 4.8, 1 kW of electricity consumed by the pump will allow it to receive 4.8 kW of heat with it free of charge, that is, a gift from nature.
Universal ubiquity of use. Even if no power lines are available, the compressor in the heat pump can be diesel driven. And there is "natural" heat in every corner of the planet - the heat pump will not remain "hungry".
Environmental friendliness of use. There are no combustion products in the heat pump, and its low energy consumption "exploits" power plants less, indirectly reducing harmful emissions from them. The refrigerant used in heat pumps is ozone friendly and does not contain chlorocarbons.
Bi-directional mode of operation. The heat pump can heat the room in winter and cool in summer. The "heat" taken from the room can be used effectively, for example, to heat the water in the pool or in the hot water system.
Operational safety. In principle, the operation of a heat pump, you will not consider dangerous processes. The absence of open flames and harmful secretions dangerous to humans, the low temperature of the heat carriers make the heat pump a "harmless" but useful household appliance.
Some nuances of operation
Effective use of the principle of operation of a heat pump requires compliance with several conditions:
- the room that is heated must be well insulated (heat loss up to 100 W / m 2) - otherwise, taking heat from the street, you will warm the street for your own money;
- heat pumps are beneficial to use for low-temperature heating systems. Under such criteria, floor heating systems (35-40 ° C) are excellent. The heat conversion coefficient significantly depends on the ratio of the temperatures of the inlet and outlet circuits.
Let's summarize what has been said!
The essence of the principle of operation of a heat pump is not in production, but in heat transfer. This allows to obtain a high coefficient (from 3 to 5) of thermal energy conversion. Simply put, each used 1 kW of electricity will "transfer" 3-5 kW of heat into the house. Is there anything else to say?
A heat pump is a device that transfers heat energy from a less heated body to a more heated body, increasing its temperature. In recent years, heat pumps have been in high demand as a source of alternative heat energy that allows you to get really cheap heat without polluting the environment.
Today they are produced by many manufacturers of heating equipment, and the general trend is that in the coming years it is heat pumps that will take the leading position in the range of heating equipment.
Typically, heat pumps use warmth of groundwater, the temperature of which is approximately at the same level all year round and is + 10C, the heat of the environment or water bodies.
The principle of their operation is based on the fact that any body with a temperature higher than the value of absolute zero has a reserve of thermal energy, which is directly proportional to its mass and specific heat capacity. It is clear that the seas, oceans, as well as underground waters, the mass of which is large, have a tremendous supply of thermal energy, the partial use of which for heating a home does not in any way affect their temperature and the ecological situation on the planet.
"Take away" heat energy from any body can only be cooled. The amount of heat released during this (in a primitive form) can be calculated by the formula
Q \u003d CM (T2-T1) where
Q- received heat
C -heat capacity
M - weight
T1 T2 - the difference in temperatures by which the body was cooled
The formula shows that when one kilogram of coolant is cooled from 1000 degrees to 0 degrees, the same amount of heat can be obtained as when 1000 kg of coolant is cooled from 1C to 0C.
The main thing is to be able to use thermal energy and direct it to heating residential buildings and industrial premises.
The idea of \u200b\u200busing the thermal energy of less heated bodies arose in the middle of the 19th century, and its authorship belongs to the famous scientist of that time, Lord Kelvin. However, his business did not progress further than the general idea. The first heat pump project was proposed in 1855 and belonged to Peter Ritter for Rittenger. But he did not receive support and found no practical application.
The "rebirth" of the heat pump dates back to the mid-forties of the last century, when ordinary household refrigerators became widespread. It was they who pushed the Swiss Robert Weber to the idea of \u200b\u200busing the heat generated by the freezer to heat water for household needs.
The effect obtained was stunning: the amount of heat was so great that it was enough not only for hot water supply, but also for heating water for heating. True, at the same time it was necessary to work hard and come up with a system of heat exchangers that allows you to utilize the thermal energy released by the refrigerator.
However, at first, Robert Weber's invention was seen as a fun idea, and was perceived like ideas from the modern famous heading "Crazy Hands". Real interest in it arose much later, when the question of finding alternative energy sources was really acute. It was then that the idea of \u200b\u200ba heat pump got its modern shape and practical application.
Modern heat pumps can be classified according to the source of low-temperature heat, which can be soil, water (in an open or underground reservoir), and outside air.
The resulting heat energy can be transferred to water and used for hot water heating and hot water supply, as well as air, and used for heating and air conditioning. With this in mind, heat pumps are divided into 6 types:
- From soil to water (soil to water)
- From soil to air (soil to air)
- From water to water (water to water)
- From water to air (water to air)
- Air to water (air to water)
- Air to air (air to air)
Each type of heat pump has its own characteristic installation and operation.
Installation method and features of operation of the heat pump GROUND-WATER
- Soil one-stop supplier of low temperature thermal energy
The soil has a colossal amount of low-temperature thermal energy. It is the earth's crust that constantly accumulates solar heat and at the same time is heated from the inside, from the core of the planet. As a result, at a depth of several meters, the soil always has a positive temperature. As a rule, in the central part of Russia we are talking about 150-170 cm.It is at this depth that the soil temperature has a positive value and does not fall below 7-8 C.
Another feature of the soil is that, even in severe frosts, it freezes gradually. As a result, the minimum soil temperature at a depth of 150 cm is observed when the calendar spring is already on the surface and the heat demand for heating decreases.
This means that in order to "take away" heat from the ground in the central region of Russia, heat exchangers for accumulating heat energy must be located at a depth below 150 cm.
In this case, the coolant circulating in the heat pump system, passing through the heat exchangers, will be heated due to the heat of the ground, then, entering the evaporator, transfer heat to the water circulating in the heating system and return for a new portion of thermal energy.
- What can be used as a coolant
The so-called "brine" is most often used as a heat carrier in ground-water heat pumps. It is prepared from water and ethylene glycol or propylene glycol. Some systems use freon, which greatly complicates the design of the heat pump and leads to an increase in its cost. The fact is that the heat exchanger of this type of pump must have a large heat exchange area, therefore, and the internal volume, which requires an appropriate amount of heat carrier.
Freon use although it increases the efficiency of the heat pump, it requires absolute tightness of the system and its resistance to high pressure.
For systems with "brine" heat exchangers are usually made of polymer pipes, most often polyethylene, with a diameter of 40-60 mm. Heat exchangers are designed as horizontal or vertical collectors.
It is a pipe laid in the ground at a depth below 170 cm. You can use any undeveloped piece of land for this. For convenience and to increase the area of \u200b\u200bheat exchange, the pipe is laid in a zigzag, loops, spiral, etc. In the future, this piece of land can be used as a lawn, flower bed or vegetable garden. It should be noted that heat transfer between the soil and the collector is better in a humid environment. Therefore, the surface of the soil can be safely watered and fertilized.
It is believed that an average of 1 m2 of soil gives from 10 to 40 watts of thermal energy. Depending on the need for heat energy, there can be any number of collector loops.
A vertical collector is a system of pipes installed vertically in the ground. For this, wells are drilled to a depth of several meters to tens, or even hundreds of meters. Most often, the vertical collector is in close contact with groundwater, but this is not a necessary condition for its operation. That is, a vertically installed underground reservoir can be "dry".
The vertical collector, just like the horizontal one, can be of almost any design. The most widespread systems are the "pipe-in-pipe" and "loop" systems, through which the brine is pumped down and rises back to the evaporator.
It should be noted that vertical collectors are the most productive. This is explained by their location at great depths, where the temperature is almost always at the same level and is 1-12 C. When using them from 1 m2, you can get from 30 to 100 watts of power. If necessary, the number of wells can be increased.
To improve the process of heat transfer between the pipe and the ground, the space between them is poured with concrete.
- Advantages and disadvantages of ground-to-water heat pumps
Installation of a ground-to-water heat pump requires significant financial investments, but its operation allows you to get almost free heat energy. This does not cause any damage to the environment.
Among the advantages of this type of heat pump should be noted:
- Durable: can work for decades in a row without repairs and maintenance
- Ease of operation
- Possibility of using a plot of land for farming
- Fast payback: when heating premises of a large area, for example, from 300 m2 and more, the pump pays for itself in 3-5 years.
Considering that the installation of a heat exchanger in the ground is a complex agrotechnical work, they must be performed with a preliminary development of the project.
How a heat pump works
The heat pump consists of the following elements:
- Compressor powered by a conventional electrical network
- Evaporator
- Capacitor
- Capillary
- Thermostat
- Working fluid or refrigerant, the role of which freon is most suitable
The principle of operation of a heat pump can be described using the well-known "Carnot Cycle" from the school physics course.
The gas (freon) entering the evaporator through the capillary expands, its pressure decreases, which leads to its subsequent evaporation, in which it, in contact with the walls of the evaporator, actively removes heat from them. The temperature of the walls decreases, which creates a temperature difference between them and the mass in which the heat pump is located. Typically, these are groundwater, sea water, lake or land mass. It is not difficult to guess that in this case the process of transfer of thermal energy from a more heated body to a less heated body begins, which in this case are the walls of the evaporator. At this stage of operation, the heat pump “pumps out” heat from the heat carrier medium.
In the next step, the refrigerant is sucked in by the compressor, then compressed and pressurized into the condenser. In the process of compression, its temperature rises and can range from 80 to 120 C, which is more than enough for heating and hot water supply of a residential building. In the condenser, the refrigerant gives up its reserve of thermal energy, cools down, turns into a liquid state, and then enters the capillary. Then the process is repeated.
To control the operation of the heat pump, a thermostat is used, with the help of which the supply of electricity to the system is stopped when the room reaches the set temperature and the pump resumes when the temperature drops below a predetermined value.
The heat pump can be used as a source of heat energy and can be combined with heating systems similar to heating systems based on a boiler or stove. An example of such a system is shown in the diagram above.
It should be noted that the operation of the heat pump is possible only when it is connected to a source of electrical energy. In this case, it may be mistakenly believed that the entire heating system is based on the use of electrical energy. In fact, to transfer 1 kW of thermal energy to the heating system, it is necessary to spend approximately 0.2-0.3 kW of electrical energy.
Heat pump advantages
Among the advantages of a heat pump are:
- High efficiency
- Possibility of switching from heating mode to air conditioning mode and its subsequent use in summer for cooling the premises
- Possibility to use an efficient automatic control system
- Environmental safety
- Compactness (no more than a household refrigerator)
- Quiet operation
- Fire safety, which is especially important for heating country houses
Among the disadvantages of a heat pump, it should be noted high cost and complexity of installation.
