The heat pump air water transforms the energy of the external environment into heat that heats the interior space. That is, with the help of this device, a dwelling or building can be “heated” with ordinary air. Moreover, the air does not burn in the furnace, but simply gives up its calories to a complex unit - a heat pump, which transports this energy into the room and gives it to the heating system.
Agree, such manipulations with energies are similar to magic. But there is nothing fantastic in heat pumps of this type. And in this article we will consider the principles of operation and the device of such a unit.
The scheme of operation of an air source heat pump is copied from a refrigerator or air conditioner, namely:
- A low-calorie energy carrier (air) boils a refrigerant filled into a cyclic circuit that connects an evaporator (heat trap) to a condenser (heat emitter).
- In the condenser, the refrigerant vapors pass into a different state of aggregation (liquid) and give off energy to the heating system.
- After that, the liquid refrigerant again goes to the evaporator, where it turns into vapor. And everything starts over.
That is, the same inverse Carnot principle is used in the work, but the main part of the installation is not an evaporator that accumulates heat from the surrounding space, but a condenser that gives the accumulated calories to the consumer.
|
|
At the same time, the cyclical operation of the unit is provided by a special compressor, which not only pumps the refrigerant along the circuit, but also compresses it, thereby increasing the heat transfer on the condenser. However, this is not the only power unit of the installation - the heat pump is equipped with a sufficiently powerful fan that blows over the evaporator.
Well, as a heat consumer, either a convector warms up the air inside the room, or a “warm floor” system or other radiators with a large area.
But with standard batteries, thermal fans do not work very efficiently.
Moreover, the convector with a condenser is mounted indoors, and the evaporator with a fan is either outside, on the facade, or in the inside of the exhaust branch of the ventilation system.
Advantages and disadvantages of air source heat pumps
Reviews about the air-to-water heat pump are both good and bad. After all, this device, with all its undeniable advantages, is not without some drawbacks.
Moreover, the advantages include the following facts:
- Firstly, such a unit is easy to mount. Indeed, for the primary circuit, closed to the evaporator, neither earthworks nor reservoirs are needed.
- Secondly, the air eats everywhere, but the land, in personal ownership, is only outside the city, but there are even more problems with artificial or natural reservoirs. Therefore, air source heat pumps for heating can be installed even in urban areas without asking permission from the regulatory authorities.
- Thirdly, the air pump can be combined with the ventilation system, using the power of the unit to increase the efficiency of air exchange in the room.
In addition, such a pump operates almost silently and is easy to program.
Well, the inevitable disadvantages can be represented as such a list:
- The efficiency of the unit depends on the ambient temperature. Therefore, the efficiency of the device in summer is higher than in winter.
- The air pump can only be turned on in relatively light frosts. Moreover, at -7 degrees Celsius, a household air pump will no longer work. Although industrial units are switched on at -25 degrees Celsius.
In addition, an air pump is not a completely autonomous power plant. The unit consumes electricity, transforming 1 kWh into 11-14 MJ.
DIY air source heat pump: assembly diagram
Unlike rather complex geothermal and hydrothermal systems, an air-to-water heat pump is available for manufacturing even on your own.
Moreover, for the manufacture of an air system, we need a relatively cheap set consisting of the following parts and assemblies:
- Split system compressor - it can be purchased at a service center or repair shop
- 100-liter stainless steel tank - it can be removed from any old washing machine
- A polymer container with a wide mouth - an ordinary can or polypropylene is suitable.
- Copper pipes with a throughput diameter of more than 1 mm. They will have to be bought, but this is the only expensive purchase in the entire project.
- A set of shut-off and control valves, which will include a drain valve, an air etching valve, a safety valve.
- Fasteners - brackets, clips for pipes, clamps and other things.
In addition, we need the cheapest refrigerant - freon and at least the simplest control unit, without which the use of heat pumps will be very difficult, due to the need to synchronize the operation of the compressor with the temperature on the surface of the evaporator and condenser.
Assembly of the unit
Well, the build process itself is as follows:
- We make a coil from a copper pipe, the dimensions of which must correspond to the cross section and height of the steel tank.
- We mount the coil in the tank, leaving the outlets of the copper pipe outside. Next, we seal the tank and equip it with an inlet (bottom) and outlet (top) fitting. As a result, the first element of the system is obtained - a condenser - with ready-made taps for a straight heating pipe (upper fitting) and a return pipe (lower fitting)
- We mount the compressor on the wall (using the bracket). We connect the pressure fitting of the compressor with the upper outlet of the copper pipe.
- We make a second coil from a copper pipe, the dimensions of which coincide with the cross section and height of the polymer can.
- We mount the coil in a can by installing a fan at its end that blows air onto the coil. Moreover, two issues should come out of the can. As a result, this whole structure, which is the evaporator of the system, is mounted on the facade or in the ventilation shaft.
- We connect the lower outlet of the tank (condenser) with the lower outlet of the can (evaporator) by inserting a control throttle into this pipeline.
- We connect the upper outlet of the can with the suction pipe of the compressor.
That's basically it. Using the principle of operation of an air source heat pump, the system is almost ready. It remains only to fill the refrigerant into the compressor and connect the throttle valve to the control unit.
Air heating with a heat pump: calculation of the installation capacity
The power of a heat pump depends on many factors, namely: the volume of refrigerant, the surface area of the coils in the evaporator and condenser, the expected volume of heat transfer to the heating system, and so on. Therefore, in most cases, the calculation of power is carried out in special programs that take into account other input data.
In a simplified form, these programs are designed as online "calculators", with open fields for entering the following parameters:
- The area of the room and the height of the ceilings - they are used to calculate the volume.
- The region where the building is located - using this parameter, the average annual air temperature is determined, which affects the performance of the evaporator.
- The degree of insulation of the task - using this parameter, the expected "caloric content" of the heating system is determined.
At the final stage, the last two parameters are converted into coefficients by which the volume of the room is multiplied. The figure obtained as a result of such manipulations is compared with tabular values that link the pump power with the heated volume.
As a result, it turns out that heating a house with an area of 100 square meters, as a rule, requires a 5-kilowatt heat pump, and a dwelling of 350 square meters can be heated with a 28-kilowatt pump.
Air source heat pump: the nuances of unit maintenance
The air-to-water heat pump does not require any special maintenance, with partial disassembly/assembly.
To maintain the system's performance, the owner will only have to perform the following manipulations:
- Periodic cleaning of the fan and grill on the evaporator from clogged debris (leaves, dust, and so on).
- Periodic lubrication of the compressor, performed according to the scheme provided by the manufacturer.
- Oil change in power units (compressor, fan).
- Periodically check the integrity of the copper refrigerant piping and power cable that feeds the compressor and fan.
One type of heat pump with a simple design is the air-to-air heat pump. The principle of operation of the pump is similar to that of a geothermal heat pump. The difference lies in the fact that the heat is not taken from the ground or water, but from the outside air masses. Accordingly, the heating of the building occurs by heating the air in the premises.
We can say that an air-to-air heat pump is an air conditioner in reverse. This is the main advantage of an air-to-air heat pump - for its installation and operation, drilling of wells and laying an underground circuit is not required.
If, for a number of reasons, it is not possible to lay the contour of an underground heat exchanger for heat extraction (there is no financial opportunity, there is not enough space on the site for horizontal laying, there is no groundwater under the site or there is no lake next to it, the presence of a granite layer at shallow depths) - a heat pump air-to-air type will be the most acceptable solution for economical and environmentally friendly heating.
The device and principle of operation of the air-to-air heat pump
The air-to-air heat pump consists of outdoor and indoor units. The outer, also known as the evaporation unit, is located outside the building. It is with its help that heat is extracted from the outside air. This heat heats the refrigerant, which boils into a gaseous state. The compressor then compresses this gas, significantly raising its temperature. The heat of the compressed gas is transferred to the condenser (indoor unit), which is located indoors. The condenser gives off heat to the indoor air. This process takes place continuously and is controlled automatically until the desired room temperature is reached.
If there is a need to heat several rooms or one large one, then in this case various systems of distribution and supply of warm air are used.
Due to the fact that heat pumps of this type heat only the air in the premises (there is direct air heating), such heat pumps can only be used for heating. That is, for heating water in the bathroom or kitchen, it is necessary to provide other solutions.
Pros of using
The advantage of an air-to-air heat pump, compared to an air-to-water pump, is the low temperature of the air that passes through the condenser coil. Simply put, if air-to-water heat pumps for high-quality heating require heating of the heat carrier (water) to sufficiently high temperatures, then in the case of an air-to-air heat pump, the required air heating temperature is much lower. Moreover, the efficiency coefficient of a heat pump is the higher, the smaller the difference between the temperature of the heat source and the temperature in the heating system.
The main advantages of an air-to-air heat pump:
- simplicity of design, installation and operation - for the installation of such heat pumps there is no need for drilling, laying complex communications, allocating special rooms, etc.;
- the possibility of installation in almost any climatic zone;
- Heat pumps of this type can be installed in an already built house with an existing conventional heating system, thereby achieving significant savings in heating costs. Installation will require minimal modification and intervention to the existing design;
- have the lowest cost and the shortest payback period, in comparison with other types of heat pumps;
- low power consumption;
- autonomy, compactness and noiselessness of work;
- in summer, air-to-air heat pumps can be switched to cooling mode, and the presence of high-efficiency air filters will help create the required microclimate in the premises.
Disadvantages of an air-to-air heat pump
Unfortunately, air-to-air heat pumps also have their disadvantages. One of them is the dependence of the performance value on fluctuations in the outside air temperature.
At an outside air temperature of 0°C, the energy efficiency coefficient of the heat pump drops to the level of 2-2.5, that is, 2-2.5 kW of heat will be produced per 1 kW of energy consumed.
In comparison, at higher temperatures, these heat pumps have an energy efficiency factor of 3-4. And when the temperature drops to -20 ° C, the energy efficiency coefficient drops to 1. That is, it becomes necessary to heat the room by other means. Although, at the moment there are manufacturers with world-famous names that offer air-to-air heat pumps that can operate efficiently at temperatures down to -25°C.
Reading 7 min.
The term heat pump means a set of units designed to accumulate heat energy from various sources in the environment and transfer this energy to consumers.
For example, such sources can be sewage risers, waste from various large industries, heat generated during operation from various power plants, etc. As a result, various media and bodies with a temperature of more than one degree can act as a source.
The task of a heat pump is to convert the natural energy of water, earth or air into thermal energy for the needs of the consumer. Since these types of energy are constantly self-regenerating, we can consider them an unlimited source.
Heat pump for home heating working principle
The principle of operation of heat pumps is based on the ability of bodies and media to give their thermal energy to other similar bodies and media. According to this feature, various types of heat pumps are distinguished, in which an energy supplier and its recipient are necessarily present.
In the name of the pump, the source of thermal energy is indicated in the first place, and the type of carrier to which the energy is transferred is indicated in the second place.
In the design of each heat pump for heating a house, there are 4 main elements:
- A compressor designed to increase the pressure and temperature of the steam resulting from the boiling of freon.
- An evaporator, which is a tank in which freon passes from a liquid state to a gaseous state.
- In the condenser, the refrigerant transfers heat energy to the internal circuit.
- The throttle valve regulates the amount of refrigerant entering the evaporator.
The type of heat pump air air means that heat energy will be taken from the external environment (atmosphere) and transferred to the carrier, also air.
Heat pump air air: principle of operation The principle of operation of this system is based on the following physical phenomenon: the medium in the liquid state, evaporating, lowers the temperature of the surface, from where it is dissipated.
For clarity, let's briefly consider the operation of the refrigerator freezer. Freon, circulating through the tubes of the refrigerator, takes heat from the refrigerator and heats up itself. As a result, the heat collected by it is transferred to the external environment (that is, to the room in which the refrigerator is located). Then the refrigerant, compressing in the compressor, cools down again and the circulation continues. An air source heat pump works on the same principle - it takes heat from the outdoor air and heats the house.
The design of the unit consists of the following parts:
- The external pump unit consists of a compressor, an evaporator with a fan and an expansion valve.
- Thermally insulated copper tubes are used to circulate freon
- A condenser with a fan on it. It serves to dissipate already heated air over the area of \u200b\u200bthe premises.
During the operation of an air source heat pump, when heating a house, the following processes occur in a certain order:
- The fan draws outside air into the unit and passes through the external evaporator. Freon, which makes a cycle in the system, collects all the heat energy from the outdoor air. As a result, it passes from a liquid state to a gaseous state.
- Subsequently, gaseous freon is compressed in the condenser and passes into the indoor unit.
- Then the gas passes into a liquid state, while giving off the accumulated heat to the air of the room. This process takes place in a condenser located in the room.
- The excess pressure leaves through the expansion valve, and freon in a liquid state goes to a new circle.
Freon will constantly take thermal energy from the street air, since its temperature will always be lower. The exception is when it is very cold outside. Under such conditions, the efficiency of the heat pump will decrease.
To increase the power of the unit, maximize the surfaces of the condenser and evaporator.
Like any complex device, an air source heat pump has its pros and cons. Among the advantages it is worth highlighting:
1. Depending on the need, the unit can raise or lower the heating temperature of the house.
2. This type of pump does not pollute the environment with harmful products of fuel combustion.
3. The device is easy to install.
4. The air pump is absolutely safe in terms of fire.
5. The heat transfer coefficient of the pump is very high compared to energy costs (4 to 5 kW of heat is generated per 1 kW of electricity consumed)
6. Differ in reasonable price.
7. The device is convenient to use.
8. The system is controlled automatically.
Of the minuses of the air system, it is worth mentioning:
1. Slight noise generated by the operation of the device.
2. The efficiency of the device depends on the ambient temperature.
3. At low outdoor temperatures, electricity consumption increases. (below -10 degrees)
4. The system is entirely dependent on the availability of electricity. The problem can be solved by installing an autonomous generator.
5. Air pump cannot heat water.
In general, air-to-air devices are ideal for heating wooden houses, in which, due to the nature of the material, natural heat losses are reduced.
Before choosing an air pump, you should find out the following key points:
- Insulation index of rooms.
- Square of all rooms
- Number of people living in a private house
- climate conditions
In most cases, 10 sq. m. of the room should account for about 0.7 kW of device power.
Heat pumps for home heating water water.
When arranging a heating system in a private house, water-water class systems are well suited. In addition, they will be able to provide housing with hot water. Various reservoirs, groundwater, etc. are suitable as sources of natural heat.
The operation of the water-water pump is based on the law that a change in the state of aggregation (from liquid to gas and vice versa) of a substance, under the influence of various factors, entails the release or absorption of heat energy.
This type of pumps can be used for heating a house even at low ambient temperatures, since positive temperatures still remain in the deep layers of the earth.
The principle of operation of a water-to-water heat pump is as follows:
- A special pump drives water through the copper pipes of the system from an external source into the installation.
- In the device, water from the environment acts on the refrigerant (freon), the boiling point of which is from +2 to +3 degrees. Part of the heat energy of the water is transferred to freon.
- The compressor sucks in the gaseous refrigerant and compresses it. As a result of this process, the temperature of the refrigerant increases even more.
- Then the freon is sent to the condenser, where it heats the water to the required temperature (40-80 degrees). The heated water enters the pipeline of the heating system. Here the freon returns to a liquid state and the cycle begins anew.
It should be noted that water-water devices are used to heat a house with an area of 50-150 sq.m.
Heat pump water water: principle of operation When choosing a device of this class, you should pay attention to certain conditions:
- As a source of energy, preference should be given to open reservoirs (it is easier to install pipes), at a distance of no more than 100 m. In addition, the depth of the reservoir for more northern regions should be at least 3 meters (water usually does not freeze at such a depth). Pipes leading to water must be insulated.
- The hardness of the water greatly affects the operation of the pump. Not every model is able to function at high rates of rigidity. As a result, before purchasing the device, a water sample is taken and, based on the results, a pump is selected.
- According to the type of operation, the units are divided into monovalent and bivalent. The former will perfectly cope with the role of the main source of heat (due to their high power). The latter can act as an additional source of heating.
- With the power of the pump, its efficiency increases, but at the same time, the consumption of electricity also increases.
- Additional features of the device. For example: soundproof housing, domestic water heating function, automatic control, etc.
- To calculate the required power of the device, you need to multiply the total area of \u200b\u200bthe premises by 0.07 kW (energy indicator per 1 sq.m.). This formula is valid for standard rooms, with a height of no more than 2.7 m.
Any owner of a private house seeks to minimize the cost of heating the home. In this regard, heat pumps are significantly more profitable than other heating options, they provide 2.5-4.5 kW of heat per kilowatt of electricity consumed. The reverse side of the coin: to get cheap energy, you will have to invest a lot of money in equipment, the most modest heating installation with a capacity of 10 kW will cost 3500 USD. e. (starting price).
The only way to reduce costs by 2-3 times is to make a heat pump with your own hands (abbreviated as TN). Consider several real working options, collected and tested by enthusiastic craftsmen in practice. Since the manufacture of a complex unit requires basic knowledge of refrigeration machines, let's start with theory.
Features and principle of operation of HP
How does a heat pump differ from other installations for heating private houses:
- unlike boilers and heaters, the unit does not produce heat on its own, but, like an air conditioner, moves it inside the building;
- HP is called a pump, because it “pumps out” energy from sources of low-grade heat - ambient air, water or soil;
- the unit is powered exclusively by electricity consumed by the compressor, fans, circulation pumps and control board;
- the operation of the unit is based on the Carnot cycle used in all refrigeration machines, such as air conditioners and split systems.
Reference. Heat is contained in any substance whose temperature is above absolute zero (minus 273 degrees). Modern technologies make it possible to take the specified energy from air with a temperature of up to -30 ° C, earth and water - up to +2 ° C.
The Carnot heat exchange cycle involves the working fluid - freon gas, boiling at sub-zero temperatures. Alternately evaporating and condensing in two heat exchangers, the refrigerant absorbs the energy of the environment and transfers it inside the building. In general, the principle of operation of a heat pump repeats that included in heating:
- Being in the liquid phase, freon moves through the tubes of the external evaporator heat exchanger, as shown in the diagram. Receiving the heat of air or water through the metal walls, the refrigerant heats up, boils and evaporates.
- Then the gas enters the compressor, which pressurizes to the calculated value. Its task is to raise the boiling point of the substance so that the freon condenses at a higher temperature.
- Passing through the internal heat exchanger-condenser, the gas again turns into a liquid and gives the accumulated energy to the heat carrier (water) or room air directly.
- At the last stage, liquid freon enters the receiver-moisture separator, then into the throttling device. The pressure of the substance drops again, freon is ready to go through a second cycle.
The scheme of operation of a heat pump is similar to the principle of operation of a split system Note. Conventional split systems and factory heat pumps have in common - the ability to transfer energy in both directions and operate in 2 modes - heating / cooling. Switching is implemented using a four-way reversing valve that changes the direction of gas flow along the circuit.
In domestic air conditioners and HP, various types of thermostatic valves are used to reduce the pressure of the refrigerant before the evaporator. In household split systems, a simple capillary device plays the role of a regulator; an expensive thermostatic expansion valve (TRV) is installed in pumps.
Note that the above cycle occurs in all types of heat pumps. The difference lies in the methods of heat supply / removal, which we will list below.
Types of throttle fittings: capillary tube (photo on the left) and thermostatic expansion valve (TRV) Varieties of installations
According to the generally accepted classification, HPs are divided into types according to the source of energy received and the type of coolant to which it is transferred:
Reference. Varieties of heat pumps are listed in order of increasing cost of equipment along with installation. Air installations are the cheapest, geothermal installations are expensive.
The main parameter that characterizes a heat pump for heating a house is the efficiency coefficient COP, equal to the ratio between the energy received and the energy consumed. For example, relatively inexpensive air heaters cannot boast of high COP - 2.5 ... 3.5. We explain: having spent 1 kW of electricity, the installation supplies 2.5-3.5 kW of heat to the dwelling.
Methods for extracting heat from water sources: from a pond (left) and through wells (right) Water and soil systems are more efficient, their real coefficient lies in the range of 3…4.5. Performance is a variable value that depends on many factors: the design of the heat exchange circuit, immersion depth, temperature and water flow.
An important point. Hot water heat pumps are not capable of heating the coolant to 60-90 °C without additional circuits. The normal water temperature from the HP is 35 ... 40 degrees, the boilers clearly win here. Hence the recommendation of the manufacturers: connect the equipment to low-temperature heating - water.
Which TN is better to collect
We formulate the problem: you need to build a home-made heat pump at the lowest cost. A number of logical conclusions follow from this:
- The installation will have to use a minimum of expensive parts, so it will not be possible to achieve a high COP value. In terms of performance, our device will lose to factory models.
- Accordingly, it is pointless to make a pure air HP, it is easier to use it in heating mode.
- To get real benefits, you need to make an air-to-water, water-to-water heat pump or build a geothermal installation. In the first case, you can achieve a COP of about 2-2.2, in the rest - reach an indicator of 3-3.5.
- It will not be possible to do without floor heating circuits. A coolant heated to 30-35 degrees is incompatible with a radiator network, except in the southern regions.
Laying the external contour of the HP to the reservoir Comment. Manufacturers claim: the inverter split system operates at a street temperature of minus 15-30 ° C. In reality, the heating efficiency is significantly reduced. According to homeowners, on frosty days, the indoor unit delivers a barely warm air flow.
To implement the water version of the HP, certain conditions are required (optional):
- a reservoir 25-50 m from the dwelling, at a greater distance, electricity consumption will increase dramatically due to a powerful circulation pump;
- a well or well with a sufficient supply (debit) of water and a place for draining (pit, second well, gutter, sewerage);
- prefabricated sewer (if you are allowed to crash into it).
Groundwater flow is easy to calculate. In the process of taking heat, a home-made HP will lower their temperature by 4-5 ° C, from here the volume of the flow is determined through the heat capacity of water. To obtain 1 kW of heat (we take a delta of water temperatures of 5 degrees), you need to drive about 170 liters through a heat pump for an hour.
Heating a house with an area of 100 m² will require a power of 10 kW and a water consumption of 1.7 tons per hour - an impressive volume. Such a thermal water pump is suitable for a small country house of 30-40 m², preferably insulated.
Methods of heat extraction by geothermal heat pumps The assembly of a geothermal system is more realistic, although the process is quite laborious. The option of laying the pipe horizontally over an area at a depth of 1.5 m is immediately dismissed - you will have to shovel the entire area or pay money for the services of earthmoving equipment. The method of drilling wells is much easier and cheaper to implement, with virtually no disturbance to the landscape.
The simplest heat pump from a window air conditioner
As you might guess, for the manufacture of a water-to-air heat pump, a window cooler in working condition is required. It is highly desirable to buy a model equipped with a reversing valve and able to work for heating, otherwise you will have to redo the freon circuit.
Advice. When buying a used air conditioner, pay attention to the nameplate, which displays the technical characteristics of the household appliance. The parameter you are interested in is (indicated in kilowatts or British thermal units - BTU).
The heating capacity of the device is greater than the refrigeration one and is equal to the sum of two parameters - the performance plus the heat generated by the compressor With some luck, you don't even have to release freon and re-solder the tubes. How to convert an air conditioner into a heat pump:
Recommendation. If the heat exchanger cannot be placed in the tank without breaking the freon lines, try to evacuate the gas and cut the pipes at the right points (away from the evaporator). After assembling the water heat exchange unit, the circuit will have to be soldered and filled with freon. The amount of refrigerant is also indicated on the label.
Now it remains to start a home-made HP and adjust the water flow, achieving maximum efficiency. Please note: the improvised heater uses a completely factory "stuffing", you just moved the radiator from the air to the liquid. How the system works live, look at the video of the craftsman:
Making a geothermal installation
If the previous option allows you to achieve approximately double savings, then even a home-made earth circuit will give a COP in the region of 3 (three kilowatts of heat per 1 kW of electricity consumed). True, financial and labor costs will also increase significantly.
Although a lot of examples of assembling such devices have been published on the Internet, there is no universal instruction with drawings. We will offer a working version, assembled and tested by a real home master, although many things will have to be thought out and completed on their own - it is difficult to put all the information about heat pumps in one publication.
Calculation of the ground circuit and pump heat exchangers
Following our own recommendations, we proceed to the calculations of a geothermal pump with vertical U-shaped probes placed in wells. It is necessary to find out the total length of the outer contour, and then - the depth and number of vertical shafts.
Initial data for the example: you need to heat a private insulated house with an area of 80 m² and a ceiling height of 2.8 m, located in the middle lane. we will not produce for heating, we will determine the need for heat by area, taking into account thermal insulation - 7 kW.
Optionally, you can equip a horizontal collector, but then you will have to allocate a large area for excavation An important clarification. Engineering calculations of heat pumps are quite complex and require high qualifications of the performer; entire books are devoted to this topic. The article provides simplified calculations taken from the practical experience of builders and craftsmen - lovers of homemade products.
The intensity of heat exchange between the ground and the non-freezing liquid circulating along the contour depends on the type of soil:
- 1 running meter of a vertical probe immersed in groundwater will receive about 80 W of heat;
- in stony soils, heat removal will be about 70 W / m;
- clay soils saturated with moisture will give off about 50 W per 1 m of collector;
- dry rocks - 20 W / m.
Reference. The vertical probe consists of 2 loops of pipes lowered to the bottom of the well and filled with concrete.
An example of calculating the length of a pipe. To extract the required 7 kW of thermal energy from the raw clay rock, you need to divide 7000 W by 50 W / m, we get a total probe depth of 140 m. Now the pipeline is distributed over wells 20 m deep, which you can drill with your own hands. A total of 7 drillings of 2 heat exchange loops, the total length of the pipe is 7 x 20 x 4 = 560 m.
The next step is to calculate the heat exchange area of the evaporator and condenser. Various Internet resources and forums offer some calculation formulas, in most cases they are incorrect. We will not take the liberty of recommending such methods and misleading you, but we will offer some tricky option:
- Contact any well-known manufacturer of plate heat exchangers, such as Alfa Laval, Kaori, Anvitek, and so on. You can go to the official website of the brand.
- Fill out the heat exchanger selection form or call the manager and order the selection of the unit, listing the parameters of the media (antifreeze, freon) - inlet and outlet temperature, heat load.
- The company's specialist will make the necessary calculations and offer a suitable model of the heat exchanger. Among its characteristics you will find the main one - the exchange surface area.
Plate units are very efficient, but expensive (200-500 euros). It is cheaper to assemble a shell-and-tube heat exchanger from a copper tube with an outer diameter of 9.5 or 12.7 mm. Multiply the figure issued by the manufacturer by a safety factor of 1.1 and divide by the circumference of the pipe, get the footage.
A stainless steel plate heat exchanger is an ideal evaporator option, it is efficient and takes up little space. The problem is the high price of the product Example. The heat exchange area of the proposed unit was 0.9 m². Choosing a copper tube ½ "with a diameter of 12.7 mm, we calculate the circumference in meters: 12.7 x 3.14 / 1000 ≈ 0.04 m. Determine the total footage: 0.9 x 1.1 / 0.04 ≈ 25 m.
Equipment and materials
The future heat pump is proposed to be built on the basis of an outdoor unit of a split system of suitable capacity (indicated on the plate). Why is it better to use a used air conditioner:
- the device is already equipped with all components - a compressor, a throttle, a receiver and a starting electrician;
- home-made heat exchangers can be placed in the body of the refrigeration machine;
- there are convenient service ports for refueling freon.
Note. Users versed in the topic select equipment separately - compressor, expansion valve, controller, and so on. If you have experience and knowledge, such an approach is only welcome.
It is not advisable to assemble a heat pump on the basis of an old refrigerator - the power of the unit is too low. In the best case, it will be possible to “squeeze out” up to 1 kW of heat, which is enough to heat one small room.
In addition to the external "split" block, you will need the following materials:
- HDPE pipe Ø20 mm - to the earth circuit;
- polyethylene fittings for assembly of collectors and connection to heat exchangers;
- circulation pumps - 2 pcs.;
- manometers, thermometers;
- high-quality water hose or HDPE pipe with a diameter of 25-32 mm for the shell of the evaporator and condenser;
- copper tube Ø9.5-12.7 mm with a wall thickness of at least 1 mm;
- insulation for pipelines and freon lines;
- kit for sealing heating cables laid inside the water supply system (needed to seal the ends of copper pipes).
Bushing kit for sealed entry of copper tube As an external coolant, a saline solution of water or antifreeze for heating - ethylene glycol is used. You will also need a supply of freon, whose brand is indicated on the nameplate of the split system.
Assembly of the heat exchanger
Before starting installation work, the outdoor module must be disassembled - remove all covers, remove the fan and a large regular radiator. Disable the solenoid that controls the reversing valve if you do not plan to use the pump as a coolant. Temperature and pressure sensors must be retained.
Assembly order of the main HP unit:
- Fabricate the condenser and evaporator by inserting a copper tube inside the estimated length of the hose. At the ends, install tees for connecting the ground and heating circuits, seal the protruding copper pipes with a special heating cable kit.
- Using a piece of plastic pipe Ø150-250 mm as a core, wind home-made two-pipe circuits and bring the ends in the right direction, as is done in the video below.
- Place and fix both shell-and-tube heat exchangers in place of the standard radiator, solder the copper tubes to the corresponding terminals. A "hot" heat exchanger-condenser is best connected to the service ports.
- Install factory sensors that measure the temperature of the refrigerant. Insulate the bare sections of the tubes and the heat exchangers themselves.
- Install thermometers and pressure gauges on water lines.
Advice. If you plan to install the main unit outdoors, you need to take measures to prevent the oil in the compressor from freezing. Purchase and install a winter kit for electric oil sump heating.
On thematic forums, there is another way to make an evaporator - a copper tube is wound in a spiral, then inserted into a closed container (tank or barrel). The option is quite reasonable with a large number of turns, when the calculated heat exchanger simply does not fit in the air conditioner housing.
Ground loop device
At this stage, simple but time-consuming earthworks and the placement of probes in wells are carried out. The latter can be done manually or invite a drilling machine. The distance between adjacent wells is at least 5 m. Further work procedure:
- Dig a shallow trench between the holes for laying the supply pipes.
- Lower 2 loops of polyethylene pipes into each hole and fill the pits with concrete.
- Bring the lines to the connection point and mount the common manifold using HDPE fittings.
- Insulate pipelines laid in the ground and cover with soil.
On the left in the photo - lowering the probe into the casing plastic pipe, on the right - laying eyeliners in the trench An important point. Before concreting and backfilling, be sure to check the tightness of the circuit. For example, connect an air compressor to the manifold, pressurize 3-4 bar and leave for several hours.
When connecting the highways, be guided by the diagram below. Branches with taps will be needed when filling the system with brine or ethylene glycol. Bring the two main pipes from the collector to the heat pump and connect to the “cold” evaporator heat exchanger.
At the highest points of both water circuits, air vents must be installed; they are not conventionally shown in the diagram Do not forget to install the pumping unit responsible for the circulation of the liquid, the direction of flow is towards the freon in the evaporator. The media passing through the condenser and evaporator must move towards each other. How to properly fill the lines of the "cold" side, see the video:
Similarly, the condenser is connected to the house floor heating system. It is not necessary to install a mixing unit with a three-way valve due to the low flow temperature. If it is necessary to combine the HP with other heat sources (solar collectors, boilers), use multiple outputs.
Filling and starting the system
After installation and connection of the unit to the mains, an important stage begins - filling the system with refrigerant. A pitfall awaits here: you don’t know how much freon needs to be charged, because the volume of the main circuit has grown significantly due to the installation of a home-made condenser with an evaporator.
The issue is solved by the method of refueling according to the pressure and temperature of freon overheating, measured at the compressor inlet (the freon is supplied there in a gaseous state). Detailed instructions for filling in the temperature measurement method are set out in.
The second part of the presented video tells how to fill the system with R22 brand freon according to the pressure and temperature of the refrigerant superheat:
After refueling, turn on both circulation pumps to the first speed and start the compressor. Control the temperature of the brine and the internal coolant using thermometers. During the warm-up phase, the refrigerant lines may freeze, and then the frost should melt.
Conclusion
Making and running a geothermal heat pump with your own hands is very difficult. Surely, repeated improvements, bug fixes, tweaks will be required. As a rule, most malfunctions in home-made HPs occur due to improper assembly or filling of the main heat exchange circuit. If the unit immediately failed (safety automatics worked) or the coolant does not heat up, it is worth calling the refrigeration technician - he will diagnose and point out the mistakes made.
Heating equipment, for which rather expensive types of energy carriers are used, such as gas, electricity, solid and liquid fuels, has relatively recently received a worthy alternative - a water-to-water heat pump. For the operation of such equipment, which is just beginning to gain popularity in Russia, inexhaustible sources of energy are needed, characterized by low potential. At the same time, thermal energy can be extracted from almost any water sources, which can be used as natural and artificial reservoirs, wells, wells, etc. If the calculation and installation of such a pumping unit are performed correctly, then it is able to provide heating for both residential and industrial buildings throughout the winter.
Structural elements and principle of operation
For the heat pumps under consideration for heating a house, the principle of operation resembles the principle of operation of refrigeration equipment, only vice versa. If the refrigeration unit removes part of the heat from its internal chamber to the outside, thereby lowering the temperature in it, then the work of the heat pump is to cool the environment and heat the coolant that moves through the pipes of the heating system. Air-to-water and ground-to-water heat pumps operate on the same principle, which also use energy from low-grade sources to heat residential and industrial premises.
The design scheme of the water-to-water heat pump, which is the most productive among devices using energy sources with low potential, suggests the presence of such elements as:
- an external circuit along which water is pumped out of a water source;
- internal circuit, through the pipeline line of which the refrigerant moves;
- an evaporator in which the refrigerant is converted into a gas;
- a condenser in which the gaseous refrigerant becomes a liquid again;
- a compressor designed to increase the pressure of the gaseous refrigerant before it enters the condenser.
Thus, there is nothing complicated in the device of a water-to-water heat pump. If there is a natural or artificial reservoir near the house, then it is best to use a water-to-water heat pump for heating the building, the principle of operation and design features of which are as follows.
- The circuit, which is a primary heat exchanger through which antifreeze circulates, is located at the bottom of the reservoir. In this case, the depth at which the installation of the primary heat exchanger is performed must be below the freezing level of the reservoir. Antifreeze, passing through the primary circuit, is heated to a temperature of 6-8 °, and then fed to the heat exchanger, giving off heat to its walls. The task of the antifreeze circulating in the primary circuit is to transfer the heat energy of the water to the refrigerant (freon).
- In the event that the heat pump operation scheme provides for the intake and transfer of thermal energy from water pumped out from an underground well, the antifreeze circuit is not used. Water from the well is passed through a special pipe through the heat exchanger chamber, where it gives up its thermal energy to the refrigerant.
- The heat exchanger for heat pumps is the most important element of their design. This is a device consisting of two modules - an evaporator and a condenser. In the evaporator, freon, supplied through the capillary tube, begins to expand and turns into a gas. Upon contact of gaseous freon with the walls of the heat exchanger, low-potential thermal energy is transferred to the refrigerant. Freon charged with such energy is fed into the compressor.
- Freon gas is compressed in the compressor, as a result of which the temperature of the refrigerant rises. After compression in the compressor chamber, freon enters another module of the heat exchanger - the condenser.
- In the condenser, gaseous freon again turns into a liquid, and the thermal energy accumulated by it is transferred to the walls of the container in which the coolant is located. Entering the chamber of the second module of the heat exchanger, freon, which is in a gaseous state, condenses on the walls of the storage tank, imparts thermal energy to them, which is then transferred to the water in such a chamber. If at the exit from the evaporator the freon has a temperature of 6–8 degrees Celsius, then at the inlet to the condenser of a water-to-water heat pump, due to the above principle of operation of such a device, its value reaches 40–70 degrees Celsius.
Thus, the principle of operation of a heat pump is based on the fact that the refrigerant, when changing to a gaseous state, takes thermal energy from the water, and when changing to a liquid state in the condenser, it releases the accumulated energy to the liquid medium - the heat carrier of the heating system.
Air-to-water and ground-to-water heat pumps work exactly on the same principle, the difference is only in the type of source that is used to produce low-potential thermal energy. In other words, the heat pump has one principle of operation, which does not vary depending on the type or model of the device.
How efficiently the heat carrier of the heating system is heated by the heat pump is largely determined by fluctuations in the temperature of the water - a source of low-potential energy. Such devices demonstrate high efficiency when working with water from wells, where the temperature of the liquid medium during the year is in the range of 7–12 degrees Celsius.
The water-to-water pump is one of the ground source heat pumps
The principle of operation of a water-to-water heat pump, which ensures the high efficiency of this equipment, makes it possible to use such devices to equip heating systems for residential and industrial buildings not only in regions with warm winters, but also in northern regions.
In order for the heat pump, the operation scheme of which is described above, to demonstrate high efficiency, you should know how to choose the right equipment. It is highly desirable that the choice of a water-to-water heat pump (as well as "air - water" and "land - water") is carried out with the participation of a qualified and experienced specialist.
When choosing a heat pump for water heating, the following parameters of such equipment are taken into account:
- productivity, on which the area of \u200b\u200bthe building depends, the heating of which the pump can provide;
- brand under which the equipment is manufactured (this parameter must be taken into account because serious companies whose products are already appreciated by many consumers pay serious attention to both the reliability and functionality of the models produced);
- the cost of both the most selected equipment and its installation.
When choosing heat pumps water-water, air-water, ground-water, it is recommended to pay attention to the presence of additional options for such equipment. This includes, in particular, the possibility of:
- controlling the operation of equipment in automatic mode (heat pumps operating in this mode due to a special controller allow creating comfortable living conditions in the building they serve; changing operating parameters and other actions to control heat pumps that are equipped with a controller can be performed using a mobile device or remote control );
- use of equipment for heating water in the DHW system (pay attention to this option because it is not available in some (especially older) models of heat pumps, the collector of which is installed in open water bodies).
Equipment power calculation: execution rules
Before proceeding with the selection of a specific model of a heat pump, it is necessary to develop a project for the heating system that such equipment will serve, as well as calculate its power. Such calculations are necessary in order to determine the actual need for thermal energy of a building with certain parameters. At the same time, heat losses in such a building, as well as the presence of a DHW circuit in it, must be taken into account.
For a water-to-water heat pump, power calculation is performed according to the following method.
- First, the total area of the building is determined, for the heating of which the purchased heat pump will be used.
- Having determined the area of the building, it is possible to calculate the power of the heat pump capable of providing heating. Performing such a calculation, adhere to the rule: per 10 square meters. m of building area requires 0.7 kilowatts of heat pump power.
- If the heat pump will also be used to ensure the functioning of the DHW system, then 15–20% is added to the obtained value of its power.
The calculation of the heat pump power performed according to the method described above is relevant for buildings in which the ceiling height does not exceed 2.7 meters. More accurate calculations that take into account all the features of buildings that are to be heated by means of a heat pump are performed by employees of specialized organizations.
For an air-to-water heat pump, the power calculation is carried out according to a similar method, but taking into account some nuances.
How to make a heat pump yourself
Having well understood how a water-to-water heat pump works, you can make such a device with your own hands. In fact, a homemade heat pump is a set of ready-made technical devices, correctly selected and connected in a certain sequence. In order for a do-it-yourself heat pump to demonstrate high efficiency and not cause problems during operation, it is necessary to perform a preliminary calculation of its main parameters. To do this, you can use the appropriate programs and online calculators on the websites of manufacturers of such equipment or contact specialized specialists.
So, in order to make a heat pump with your own hands, you need to select the elements of its equipment according to pre-calculated parameters and perform their correct installation.
Compressor
The compressor for a home-made heat pump can be taken from an old refrigerator or split system, while paying attention to the power of such a device. The advantage of using compressors from split systems is the low level of noise generated during their operation.
Capacitor
As a condenser for a homemade heat pump, you can use a coil dismantled from an old refrigerator. Some make it on their own, using plumbing or a special refrigeration tube. As a container in which to place the condenser coil, you can take a stainless steel tank with a volume of approximately 120 liters. To place a coil in such a tank, it is first cut into two halves, and then, when the coil is installed, it is welded.
It is very important to calculate its area before choosing or self-manufacturing a coil. This requires the following formula:
P3 \u003d MT / 0.8PT
The parameters used in this formula are:
- МТ is the power of the heat generated by the heat pump (kW);
- PT is the difference between the temperatures at the inlet to and outlet of the heat pump.
To prevent air bubbles from forming in the heat pump condenser from the refrigerator, the inlet to the coil should be located at the top of the tank, and the outlet from it should be at the bottom.
Evaporator
As a container for the evaporator, you can use a simple plastic barrel with a capacity of 127 liters with a wide mouth. To create a coil, the area of \u200b\u200bwhich is determined in the same way as for a condenser, a copper tube is also used. In home-made heat pumps, as a rule, immersion-type evaporators are used, in which liquefied freon enters from below, and turns into gas at the top of the coil.
Very carefully, using soldering, when making the heat pump yourself, you should install the thermostat, since this element cannot be heated to a temperature exceeding 100 degrees Celsius.
To supply water to the elements of a self-made heat pump, as well as to drain it, ordinary sewer pipes are used.
Water-to-water heat pumps, when compared with air-to-water and ground-to-water devices, are simpler in design, but more efficient, so this type of equipment is most often made independently.
Assembling a homemade heat pump and putting it into operation
To assemble and start up a homemade heat pump, you will need the following consumables and equipment:
- welding machine;
- vacuum pump (to check the entire system for vacuum);
- a cylinder with freon, which is filled through a special valve (the valve must be installed in the system in advance);
- temperature sensors that are installed on the capillary pipes at the outlet of the entire system and at the outlet of the evaporator;
- start relay, fuse, DIN rail and electrical panel.
All welding and threaded connections during assembly should be performed with the highest quality to ensure absolute tightness of the system through which freon will move.
In the event that water in an open reservoir acts as a source of low-potential energy, it is additionally necessary to make a collector, the presence of which implies the principle of operation of heat pumps of this type. If it is supposed to use water from an underground source, it is necessary to drill two wells, into one of which water will be discharged after it has passed the entire system.
1 , average rating: 5,00
out of 5)
