There are several types of ground heat exchangers that can be used today. The possibility of arranging with your own hands, good efficiency, as well as the simplicity of the design itself made this type of ventilation very popular for arranging in a private house.
System Description
Today, it is known for sure that in all CIS countries the soil temperature at a depth of about two meters remains almost unchanged. The approximate ground temperature is +10 degrees Celsius all year round. Small changes are observed depending on the region, but they usually do not exceed two degrees. The installation of ground heat exchangers implies the use of this free energy. Thus, in the warm season, such ventilation will cool the air inside the room, and in winter, on the contrary, heat it up. In addition, the extra heat can help save the temperature that is generated by other heating elements.
Currently unpavedThe heat exchanger is most often used in conjunction with a recuperator. A recuperator is a heat exchange device that is designed to heat cold air at the expense of exhaust warm air. In addition, its system includes fans, filters, piping and a heating device.
Using the system
Such a scheme of a ground heat exchanger allows you to get air from the ground already somewhat warmed up, which helps save some amount of energy that would have gone into the operation of the heat exchanger. The presence of such an air heating system will also save energy and the design of the heat exchanger. In this case, it means that condensate will not form inside the pipeline, since the temperature of the air that will pass through the pipes will be approximately the same all the time. A problem with condensate can arise only when the heat exchanger is switched on, but at the same time, initially frosty air will enter it.
Influence of climate on ventilation
The efficiency of a ground heat exchanger for ventilation depends quite strongly on the climate observed in the region. If we talk about the climate in the CIS countries, then installing a heat exchanger can help in heating or cooling the air in the region from 5 to 20 degrees Celsius. The efficiency of the system itself will directly depend on how large the temperature difference between the soil and air is. The greater the difference, the more efficient the system works. Due to this effect, the ground heat exchanger for ventilation of the room is effectiveremedy both in winter and summer. During the heat, the system can provide a decrease in temperature from 30 to 20 degrees. In frosty weather, the temperature can increase from -20 to 0 degrees.
When calculating the ground heat exchanger for ventilation, it is necessary to take into account the fact that in spring and autumn the influence of such ventilation on the temperature is practically absent. This is justified by the fact that the ambient air and ground temperatures are too close in value, due to which the air exchange slows down significantly. In some cases, such a system may even work in a negative mode. For example, the room temperature is 12 degrees Celsius, and the presence of a heat exchanger will reduce it to 8 degrees. Taking into account this fact, it is necessary to equip the soil heat exchanger with your own hands in such a way that it can be turned off or blocked for direct air passage.
Main system types
Currently, two main types of such a system are known - this is a pipe and channelless heat exchanger. When arranging a channelless type of system, an underground layer will be used through which air will pass. Pipe, or channel type implies the presence of pipes for mounting a ground heat exchanger through which air will pass. They should also be laid underground.
These two types are united by the fact that the main channel of the inlet type must be connected to ventilation. The main requirement forOne thing to remember is that the system must have a mechanism to switch between the two modes. The first mode will use the direct air supply from the street, the second mode will use the heat exchanger.
Duct heat exchanger
When choosing between air ground heat exchangers for a private house, it is better to choose this option. Of course, it requires more time and money, but it is also more effective. In order to make this type of ventilation, it is necessary to lay the pipe system in a prepared trench in the ground. On average, the length of the pipeline is from 15 to 50 meters. The choice depends only on the possibilities and area.
It is important to remember here that the pipes for the ground heat exchanger can be rotated, as this has little to no effect on air movement. In addition, the longer the system is, the more efficiently it will work, which is also very important to consider. Arranging a short exchanger makes little sense.
Selection of pipes for laying
As already mentioned, for effective use of the system, it must have a large length. If the area around the house allows, then you can lay only one pipe around the house. If space is limited, you can use parallel stacking. The diameter of the pipes for the normal functioning of the system should be from 200 to 250 millimeters.
Great choiceare polypropylene pipes. When calculating the soil heat exchanger, you also need to know that you can improve the process of heat exchange if you reduce the wall thickness and increase their area. Based on this, corrugated material can be used. In this case, the heat will not linger in the soil system at all. It is also very important to equip the system with a slope of about 2% in any direction. A slight slope in this case is necessary so that the condensate that will form in very hot weather can drain without problems.
Stock and other elements of the system
In order to effectively remove condensate from the system, it is necessary to equip the pipeline not only with a slope, but also create a small hole at the bottom of the pipe. To drain the liquid, it is necessary to equip a drainage well or draw a conclusion directly into the ground. If the site has a low level of groundwater, then it is necessary to make a sand cushion for the system. The end of the pipe, which is located on the site, must be equipped with a filter. In addition, it must be installed above the level of snow that falls during the winter.
When arranging a soil heat exchanger with your own hands, you need to know that if snow is a rare occurrence in the region, then the height of the pipe that protrudes above the ground must be at least 1.5 meters. This must be done as protection against radon, a radioactive soil gas.
An air intake must be installed at the end of the pipe. This element must also be equipped with a filter and a strong metal mesh. Pipe endmust be installed and protected in such a way that precipitation, leaves, and also no animals, birds, etc. can enter it. If possible, this element is installed as far as possible from any sources that may affect on air quality. The minimum distance required is 10 meters.
Channelless type
In order to equip this type of heat exchanger with your own hands, it is necessary to dig a recess, the length of which should be 3-4 meters and the depth - 80 cm. In addition, this pit must be filled with gravel and covered with foam concrete on top. This design is necessary so that the temperature inside the pit does not differ from the temperature of the soil in a depression of up to 5 meters. After this stage is completed, it is necessary to equip the outlet of the pipe through which air will pass.
As for the manufacture of this pipe, this process is no different from its manufacture in the previous version. Naturally, another pipe must connect the special heat exchange layer of the pit and the ventilation of a private house. After that, air circulation will begin according to the simplest scheme. In addition, the air will not only be humidified, but also cleaned. Based on this, it can be argued that the ductless type is better in terms of air filtration, and the pipe or duct type is more efficient for heating or cooling.
System Features
Channelless type, or gravel heat exchanger is characterized by the fact thathe needs to restore his functions. In addition, it is forbidden to mount it in those places where there is an effect of external loads, for example, in the place where motor transport passes. Another feature is that if the gravel that is intended for laying is not washed, then after the arrangement of the system and the start of air circulation in the room, an unpleasant "basement" smell may occur. The same problem can occur if the gravel layer gets wet due to precipitation or groundwater rise, for example.
Flaws
If the surface layer of such an exchanger is damaged, this will lead to a decrease in its efficiency, as well as to possible saturation with moisture. All of this will require refurbishment. When arranging a do-it-yourself exchanger of this type, you also need to know that the gravel layer is both a heat exchange point and an obstacle to the passage of air. Because of this, it will be necessary to install an additional source of air injection in the system - a fan with sufficient power (several hundred watts). Naturally, these are additional costs both for installation and purchase, and for the subsequent payment of electricity. Because of this, it is necessary to carefully carry out the calculations of the system. It can be added here that the calculations of a liquid soil heat exchanger are somewhat simpler than those of a gravel one, although its arrangement and design are more complex.
Membraneless type
Today, such types of ground heat exchangers (GTO) as membraneless have appeared. They areare a combination of the two previous types of systems. The main essence of the installation of such a device is that it is necessary to mount an even layer of polymer plates on top of an even layer of gravel.
Installation of the system
The slabs must be mounted on "legs" that will rest on the gravel layer. Thus, it turns out that the air will not move through the gravel layer, as with the channelless type, but between the slab layer and the gravel layer. The main advantage is that such a heat exchanger can be used for quite a long time without regeneration of the gravel layer.
A regular gravel bed can only work for 12 hours, after which 12 hours of "rest" is needed. During such a rest, a layer of gravel will take heat from the soil, in order to then transfer it to ventilation. When using plates, these frames are greatly simplified. Another difference between a membraneless TRP is that there will be no strong obstacle to air circulation. With a ductless type of exchanger, gravel will be a natural obstacle to airflow, which is why it is necessary to equip the system with additional fans most often.
The main problem with using such a ground heat exchanger for do-it-yourself ventilation is that the system is not continuous, and therefore it is completely prohibited to use it in those regions where there is an increased level of groundwater or there is a chance that the system will be flooded atmosphericprecipitation.
