The first versions of heat pumps could only partially satisfy the needs for thermal energy. Modern varieties are more efficient and can be used for heating systems. That is why many homeowners are trying to mount a heat pump with their own hands.
We will tell you how to choose the best option for a heat pump, taking into account the geo-data of the area where it is planned to be installed. The article proposed for consideration describes in detail the principle of operation of systems for using “green energy,” and lists the differences. With our advice, you will no doubt dwell on the effective type.
For independent masters, we present the technology of assembly of the heat pump. The information presented for consideration is complemented by visual diagrams, photo selections and detailed video briefing in two parts.
The content of the article:
- What is a heat pump and how does it work?
- The main design elements of heat pumps
- Select the type of heat pump
- Building a heat pump yourself
- Conclusions and useful video on the topic
What is a heat pump and how does it work?
The term heat pump refers to a set of specific equipment. The main function of this equipment is the collection of heat energy and its transportation to the consumer. The source of such energy can be any body or medium that has a temperature of + 1º or more degrees.
In our environment, sources of low-temperature heat are more than enough. These are industrial wastes of enterprises, thermal and nuclear power plants, sewage, etc. For the operation of heat pumps in the field of home heating, three self-regenerating natural sources are needed - air, water, land.
Heat pumps “draw” energy from processes that regularly occur in the environment. The flow of processes never stops, because sources are considered inexhaustible by human criteria.
The three potential energy providers listed are directly related to the energy of the sun, which by means of heating drives air with the wind and transfers thermal energy to the earth. It is the choice of the source that is the main criterion according to which heat pump systems are classified.
The principle of operation of heat pumps is based on the ability of bodies or media to transfer heat energy to another body or medium. Recipients and suppliers of energy in heat pump systems usually work in pairs.
So distinguish the following types of heat pumps:
- Air is water.
- Earth is water.
- Water is air.
- Water is water.
- Earth is air.
- Water - water
- Air is air.
In this case, the first word determines the type of medium in which the system takes low-temperature heat. The second indicates the type of carrier to which this heat energy is transferred. So, in heat pumps water is water, heat is taken from the water medium and liquid is used as a heat carrier.
Heat pumps of a constructive type are vapor compression installations. They extract heat from natural sources, process and transport it to consumers (+)
Modern heat pumps use three main heat source. This - the soil, water and air. The easiest of these options is air heat pump. The popularity of such systems is associated with their rather simple design and ease of installation.
A photo of
The heat pump includes an indoor and outdoor unit. The outer part is intended for natural energy intake, internal for its processing
The external air-to-air heat pump unit is similar to the outside of an air conditioner, it uses similar principles.
If you wish to increase the performance of the air-to-air heat system, increase the area of its evaporator.
Thermal systems using heat from the earth’s interior are significantly more complex and expensive to build. Among them are vertical workings - wells
For the construction of a horizontal evaporator systems that take heat from the soil, large areas free from building are needed.
The evaporator tubes can be laid in numerous loops in the trenches. The main thing is to dig into the ground the required footage of the energy receiver
A well for the use of groundwater energy is constructed according to principles similar to the rules of the device evaporator systems with ground energy intake
For the device of the vertical evaporator of a heat pump that uses the energy of water, you need a nearby reservoir of sufficient area
The standard principle of the heat pump device
External air-to-air heat pump unit
Variety of air-to-air thermal installation
Horizontal evaporator system of the earth-water
The device heat receiver pump ground-to-air
Evaporator in selected earth trenches
Water well for water-to-water heat pump
Horizontal receivers of water energy
However, despite this popularity, these varieties have a rather low productivity. In addition, the efficiency is unstable and depends on seasonal fluctuations in temperature.
With decreasing temperature, their performance drops significantly. Such variants of heat pumps can be considered as an addition to the existing main source of thermal energy.
Equipment options using ground heatare considered more effective. The soil receives and accumulates thermal energy not only from the Sun, it is constantly heated by the energy of the earth’s core.
That is, the soil is a kind of heat accumulator, the capacity of which is practically unlimited. Moreover, the temperature of the soil, especially at a certain depth, is constant and varies in insignificant limits.
Scope of energy generated by heat pumps:
A photo of
Heat pumps serve as energy suppliers for the needs of low-temperature heating circuits and water heating systems.
Heat pumps have found the most active use as an energy supplier to air heating circuits.
Heat pumps are able to fully provide the system with a warm floor with the required amount of coolant required temperature
The small-sized heat pump of small or medium power perfectly cope with heated water for a private pool
Heat pumps in heating and hot water
Application in circuits of air heating
Heat carrier preparation for underfloor heating systems
Thermal installation in the pool water heating
The constancy of the source temperature is an important factor in the stable and efficient operation of this type of power equipment. Similar characteristics have systems in which the aquatic environment is the main source of thermal energy. The collector of such pumps is located either in the well, where it is located in the aquifer, or in a reservoir.
The average annual temperature of such sources as soil and water varies from + 7º to + 12º C. This temperature is quite enough to ensure the effective operation of the system.
The most effective are heat pumps that extract heat energy from sources with stable temperature indices, i.e. from water and soil
The main design elements of heat pumps
In order for the power generation plant to work according to the principles of operation of the heat pump, its design must include 4 main units, these are:
- Throttle valve.
An important element of the heat pump design is a compressor. Its main function is to increase the pressure and temperature of vapors resulting from the boiling of the refrigerant. In particular, modern scroll compressors are used for HVAC equipment and heat pumps.
Liquids with a low boiling point are used as the working medium that carries out the direct transfer of thermal energy. Ammonia and freons (+) are generally used.
Such compressors are designed to operate at sub-zero temperatures. Unlike other varieties, scroll compressors produce little noise and operate both at low gas boiling temperatures and high condensing temperatures. The undoubted advantage is their compact size and low specific weight.
Almost all the energy of the heat pump is spent on the transportation of thermal energy from the outside into the room. So, the work of the systems takes about 1 energy unit in the production of 4 - 6 units (+)
The evaporator as a structural element is a tank in which the conversion of liquid refrigerant to vapor occurs. The refrigerant, circulating in a closed circuit, passes through the evaporator. In it the refrigerant warms up and turns into steam. The resulting vapor under low pressure is directed towards the compressor.
In a compressor, refrigerant vapors are subjected to pressure and their temperature rises. The compressor pumps the heated steam under high pressure towards the condenser.
The compressor compresses the medium circulating in the circuit, as a result of which its temperature and pressure increase. Then the compressed medium enters the heat exchanger (condenser), where it is cooled, transferring heat to water or air
The next structural element of the system is a capacitor. Its function is reduced to the return of thermal energy to the internal circuit of the heating system.
Serial samples manufactured by industrial enterprises are equipped with plate heat exchangers. The main material for such capacitors is alloyed steel or copper.
For self-manufacturing heat exchanger suitable copper tube with a diameter of half an inch. The wall thickness of the pipes used to manufacture the heat exchanger must be at least 1 mm
A thermostatic, or otherwise choke, valve is installed at the beginning of that part of the hydraulic circuit where the high pressure circulating medium is converted to a low pressure medium. More precisely, a throttle paired with a compressor divides the heat pump circuit into two parts: one with high pressure parameters, the other with low ones.
When passing through an expansion throttle valve, the liquid circulating in a closed circuit partially evaporates, as a result of which the pressure drops with temperature. Then enters the heat exchanger, communicating with the environment. It captures the energy of the medium and transfers it back to the system.
By means of the throttle valve, the refrigerant flow is controlled towards the evaporator. When choosing a valve, the system parameters must be taken into account. The valve must comply with these parameters.
When passing through the heat-regulating valve, the heat-transfer fluid partially evaporates, and the flow temperature decreases (+)
Select the type of heat pump
The main indicator of this heating system is power. From the power in the first place will depend on the financial costs for the purchase of equipment and the choice of one or another source of low-temperature heat. The higher the capacity of the heat pumping system, the greater the cost of the component elements.
First of all, this refers to the capacity of the compressor, the depth of the wells for geothermal probes, or the area to accommodate the horizontal reservoir. Proper thermodynamic calculations are a kind of guarantee that the system will work efficiently.
If there is a water reservoir next to the personal area, the water-to-water heat pump will be the most cost-effective and productive choice.
To begin with it is necessary to study a site which is planned for installation of the pump. The ideal condition is the presence of a reservoir on this site. Using water-water type significantly reduce the amount of earthworks.
Using the heat of the earth, on the contrary, involves a large number of works related to excavation. Systems that use aquatic environment as low-grade heat are considered to be the most efficient.
The device of the heat pump, which extracts thermal energy from the soil, involves an impressive amount of earthworks. A collector is laid below the seasonal freezing level.
Use the thermal energy of the soil in two ways. The first involves drilling wells with a diameter of 100-168 mm. The depth of such wells, depending on the parameters of the system, can reach 100 m or more.
Special probes are placed in these wells. The second method uses a collector of pipes. Such a collector is placed underground in a horizontal plane. For this option, you need a large enough area.
For laying the collector, areas with wet ground are considered ideal. Naturally, the drilling of wells will cost more than the horizontal location of the reservoir. However, not every site has free space. For one kW of heat pump power you need from 30 to 50 m² of area.
A facility for taking thermal energy from one deep well may be a little cheaper than digging a pit. But a weighty plus is the significant savings in space, which is important for owners of small areas.
In the case of the presence on the site of a high-lying groundwater horizon, heat exchangers can be arranged in two wells located at a distance of about 15 m from each other.
The selection of thermal energy in such systems by pumping groundwater in a closed loop, parts of which are located in wells. Such a system needs to install a filter and periodically clean the heat exchanger.
The simplest and cheapest heat pump scheme is based on the extraction of thermal energy from the air. Once it became the basis for the device refrigerators, later according to its principles were developed air conditioners.
The simplest heat pump system draws energy from the air mass. In the summer she participates in heating, in the winter in air conditioning. The minus of the system is that in an independent version the unit with insufficient power
The effectiveness of different types of this equipment is not the same. The lowest indicators have the pumps using the air environment. In addition, these figures are directly dependent on weather conditions.
Soil types of heat pumps have stable performance. The efficiency coefficient of these systems varies in the range of 2.8 -3.3. The most effective systems have water-water. This is due primarily to the stability of the source temperature.
It should be noted that the deeper the pump collector is located in the reservoir, the more stable the temperature will be. To obtain a system power of 10 kW, you need about 300 meters of pipeline.
The main parameter characterizing the efficiency of the heat pump, is considered to be its conversion coefficient. The higher the conversion factor, the more efficient the heat pump is considered.
The conversion rate of the heat pump is expressed in terms of the ratio of the heat flow and the electrical power consumed by the compressor.
Building a heat pump yourself
Knowing the scheme of action and the device of the heat pump, assemble and assemble independently alternative heating system quite possible. Before starting work, it is necessary to calculate all the basic parameters of the future system. To calculate the parameters of the future pump, you can use the software designed to optimize cooling systems.
The simplest construction option is air-water system. It does not require complex work on the device of the external circuit, which is inherent in water and ground varieties of heat pumps. For the installation, only two channels will be needed, one of which will be supplied with air, the second one will be used for exhaust mass.
The easiest way to do it yourself is to have a heat pump with heat drawn from the air mass. An outdoor fan blows air to the evaporator.
In addition to the fan, you need to acquire a compressor of the required power. For such a unit is quite suitable compressor, which are equipped with conventional split systems. It is not necessary to buy a new unit.
You can remove it from old equipment or use it. old refrigerator accessories. It is advisable to use a spiral version. These compressor options, in addition to possessing sufficient efficiency, create a high pressure, which provides an increase in temperature.
To build a capacitor, you need a tank and a copper pipe. From the pipe is a coil. For its manufacture using any cylindrical body of the desired diameter. Having coiled a copper pipe on it, you can easily and quickly manufacture this structural element.
Ready coil is mounted in a pre-cut in half capacity. For the manufacture of containers is better to use materials resistant to corrosion processes. After placing the coil in it, the halves of the tank are welded.
The coil area is calculated using the following formula:
MT / 0.8 RT,
- Mt - the power of thermal energy, which gives the system.
- 0,8 - coefficient of thermal conductivity in the interaction of water with the material of the coil.
- RT - the difference between the inlet and outlet water temperatures.
Choosing a copper pipe for self-manufacture of the coil, you need to pay attention to the thickness of the walls. It must be at least 1 mm. Otherwise, when winding the pipe will be deformed. The pipe through which the refrigerant inlet is located at the top of the tank.
The heat exchanger is made of copper tube by winding the copper tube on the object with a cylindrical shape. The larger the surface area of the coil, the higher the pump performance
The evaporator of the heat pump can be made in two versions - in the form of a tank with a coil in it and in the form of a pipe in a pipe. Since the temperature of the liquid in the evaporator is small, the capacity can be made of a plastic barrel. In this container is placed the circuit, which is made of copper pipe.
In contrast to the condenser, the coil of the evaporator coil must correspond to the diameter and height of the selected container. The second variant of the evaporator: a pipe in the pipe. In this embodiment, the refrigerant pipe is placed in a plastic pipe of a larger diameter through which water circulates.
The length of such a pipe depends on the planned power of the pump. It can be from 25 to 40 meters. This tube is coiled into a spiral.
Thermostatic valve refers to the shut-off and control valves. A needle is used as a locking element in the expansion chamber. The position of the valve is determined by the temperature in the evaporator.
This is an important element of the system has a rather complex structure. It includes:
- Capillary tube.
These elements may become unusable at high temperatures. Therefore, during work on the soldering system, the valve should be isolated with asbestos cloth. The control valve must match the capacity of the evaporator.
After work on the manufacture of basic structural parts, the crucial moment comes for assembling the entire structure into a single unit. The most crucial stage is refrigerant injection process or coolant in the system.
Independently carrying out such an operation is hardly possible for a simple man in the street. There will have to turn to professionals who are engaged in repair and maintenance of climatic equipment.
The workers in this area, as a rule, have the necessary equipment. In addition to charging the refrigerant, they can test the operation of the system. Self-refrigerant injection can lead not only to structural failure, but also to serious injuries. In addition, to start the system, you also need special equipment.
When starting the system, a peak starting load occurs, which is usually around 40 A. Therefore, starting the system without a start relay is not possible. After the first start-up, adjustment of the valve and the refrigerant pressure is necessary.
The choice of refrigerant should be taken seriously. After all, this substance is essentially considered the main “carrier” of useful thermal energy. Of the existing modern refrigerants, freons are the most popular. These are derivatives of hydrocarbon compounds in which a part of carbon atoms is replaced by other elements.
As a result, the assembly of the individual elements of the heat pump should have a closed loop through which the working medium circulates.
As a result of this work, a closed loop system was obtained. The refrigerant will circulate in it, ensuring the selection and transfer of thermal energy from the evaporator to the condenser. When connecting heat pumps to the house heat supply system, it should be taken into account that the temperature of the water leaving the condenser does not exceed 50 - 60 degrees.
Due to the low temperature of the heat energy generated by the heat pump, you need to choose specialized heating devices as a heat consumer. This may be a warm floor or volume low-inertia radiators made of aluminum or steel with a large radiation area.
Self-made versions of heat pumps are most appropriate to consider as ancillary equipment that supports and complements the work of the main source.
Every year the designs of heat pumps are improving. In industrial designs intended for domestic use, more efficient heat transfer surfaces are used. As a result, system performance is constantly increasing.
An important factor that stimulates the development of such technology for the production of heat energy is the environmental component. Such systems, in addition to being fairly efficient, do not pollute the environment. The absence of an open flame makes it work absolutely safe.
Conclusions and useful video on the topic
Video # 1. How to make the simplest homemade heat pump with a heat exchanger from PEX pipe:
Video # 2. Continuing instruction:
Heat pumps have been used as alternative heating systems for a long time. These systems are reliable, have a long service life and, importantly, are environmentally friendly. They are seriously beginning to be considered as another step towards the development of efficient and safe heating systems.
Do you want to ask a question or tell about an interesting method of building a heat pump, not mentioned in the article? Please write comments in the box below.