The idea is not new, but quite often I return to it and think about implementing it in my home. Therefore, I stole a detailed article mainly for myself, but perhaps it will be useful to someone else.

I would like to note from myself that similar system It will not only cool the house in the summer, but also warm it up in the winter. You can't live without ventilation. And if in winter you draw air already heated by an earthen heat exchanger into the house, then heating costs will also decrease. This is especially true if you have stove heating or any boiler with an open flame. It is better to take the air for combustion from the street and preheat it. Efficiency will increase significantly. The only thing the authors did not notice was a solution to the condensate issue. And it may be in the heat exchanger pipes buried in the ground. And it is advisable to provide for the possibility of removing it by gravity with drainage into the soil. As an option, make part of the pipe at the lowest point from a drainage pipe with perforation. Well, lay the pipe above the water main so that it doesn’t get flooded.

Natural recuperator or free air conditioner for country house

Cooling the air in summer is one of the homeowner's top priorities. This article will tell you how to use the energy around us for this purpose and make air conditioning practically free.

The importance of ventilation cannot be overestimated. We will not repeat what has been described many times and will focus on our own task - to cool and refresh the air in the house. Traditional ventilation systems can be quite expensive to install due to the cost of components and assemblies, as well as the cost of qualified installation work.

During operation, they consume a significant amount of electricity, especially for cooling the air mass, emit a lot of heat and create noise. The system described in this article is easy to install, energy efficient, does not require special skills and is intuitive. It’s worth noting right away that due to its simplicity, it has limited functions, but it provides for modernization in any area at any convenient time.

In our case, the term “recovery” is a synonym for the word “heat exchange”, therefore the concepts “recuperator” and “heat exchanger” are interchangeable. At the physical level, the process consists of cooling/heating air, changing its temperature due to the consumption of thermal energy, and then mixing. How and why this happens, we will look further.

Stable Energy Source

Pursuing the goal of lowering the indoor temperature in the summer, it is reasonable to ask the question: “Where should the energy of the heated atmospheric air be given? How to cool it? Here the forces of nature come to our aid. The fact that at a certain depth the soil temperature is constant will be our main argument when justifying the energy efficiency of the system.
The soil is capable of endlessly exchanging energy - cooling and heating any medium (air, water), but only to its own temperature at a given depth, which remains constant due to the relative stability of the earth's core.

International practice

Of course, we are far from the first who decided to use the endless and free energy of the Earth. In European countries, which are usually called developed (Germany, Sweden, Belgium, etc.), they have been using this energy since the beginning of the last century. The successes achieved in this field are impressive.

Heat exchange systems for water below ground level are called “heat pumps.” These underground and underwater devices heat and cool the entire home. Standard projects have been developed for any building and it is possible to convert the house from a traditional (gas, electric) air conditioning system to heat pumps. In a similar, but more primitive way, this energy is used in our country by arranging underground food storage facilities (cellars).

What is good about a natural heat exchanger?

The operation of our recuperator is based on the same physical process as in heat pumps. Focusing on savings, we use this principle, adapting it to our own needs and local realities.

Problems that an adapted autonomous recuperator can solve:

Constant natural ventilation behind closed doors and windows.
Quickly replace indoor air with fresh air.
Cooling the air in the room.
Preparing the air mixture for subsequent actions.
Advantages:

Absolutely environmentally friendly. During installation and operation basic system no toxic materials are used and no heat is released into the atmosphere.
Safety. The recuperator does not use electric motors (with a power of more than 100 W), chemical agents, or high voltage.
Simplicity and cheapness. For forced ventilation Only low-power 100 W fans are used. Ventilation occurs naturally.
Oxygen is not burned during operation.
Low noise level.
Flaws:

the basic system does not provide for filtration, humidity control, heating or other processing of the air mixture (but allows for the possibility of installing appropriate equipment later).
Simple and clear system

An autonomous heat exchanger for a country house is a system of ventilation ducts, partially laid underground, included in the supply and exhaust ventilation circuit. In order to create such an “air conditioner”, it is not necessary to understand the intricacies physical phenomena. Just knowing that it works is enough. You can verify this by going down into any basement, well or subway in the heat.

The operating principle is as follows:

Atmospheric air passes through pipes laid in the ground at a constant temperature (usually from +4 to +10 ° C).
In the underground part, cool soil absorbs thermal energy heated air.
Cooled air is delivered through ventilation ducts to the premises of the house.
At the same time, the exhaust fan removes the saturated and heated air mixture (“old air”) from the room.
According to the principle of construction, such systems are divided into two main types: pipe and bunker.

Pipe - consists entirely of pipes. The design can be varied depending on the conditions of the site. Suitable for reconstruction of a house without a spacious basement, but a lot of excavation work will be required. Bunker or stone - the heat exchanger is a bunker filled with large stones. Occupies less area than a pipe one (you can arrange it in the basement of the house). Requires a basement or underground space. The best option during new construction.

We create internal system ventilation ducts Houses

In both cases, the ventilation ducts inside the house will be located approximately the same. Let's start with them.

A primitive supply and exhaust ventilation system consists of external and internal ventilation ducts connected into one network. Air outlets are located in the upper diagonally opposite corners of the rooms. In one there is an inflow, in the other there is an exhaust. In a one-story building, the main air ducts may be located in the attic. IN two-story building The supply and exhaust air ducts of the first floor will be held in boxes inscribed in interior decoration, second floor - in the attic. The location of the main air ducts should be determined for each house individually, taking into account the layout (location of walls and partitions). Tip. Rooms in which supply and exhaust ventilation is recommended: living room, bedroom, children's room, kitchen, dining room, offices, pantry, recreation rooms, gym. In bathrooms and toilets there is only an exhaust fan. Not needed at all in corridors, vestibules, halls and loggias.

Rules for calculating the internal ventilation duct system:

Pipe sewer diameter 250 mm for supply distribution and combined outlet channels. Approximate consumption - two lengths of the house + height of the upper ceiling + 20%.
Sewer pipe (gray) with a diameter of 150 mm. Approximate consumption is three times the length of the house + 20%. For a two-story house with equal floor area + 50%.
Pipe fasteners (based on the wall material) at the rate of 1 pc. by 70 cm.
Insulation (roll mineral wool) - 1 roll.
Foam, sealant, decorative grilles.
Elbows, revisions, couplings (1 piece per 70 cm).
Attention! Do not use 90° elbows, this will impede the passage of air and create noise. Combine 45° elbows (following the sewer example).

If you plan to install a pipe heat exchanger in a one-story building, supply channel will come out of the ground into a heat-insulated box outside the building and into the attic. In a two-story building, it is better to bring it into the building at the bottom of the first floor and install an internal vertical (distribution) channel, which will then be led into the attic space. When installing a bunker option in the basement of a building, the vertical distribution channel will exit the bunker directly into the room. It can also be mounted outside.

An example of calculating the consumption of materials for installing internal channels at home

Let's take as an example cottage with a calculated ventilated area of ​​60 m2, which will have approximately 100 m2 of total area and approximate dimensions of 8x12 m:

Pipe 250 mm: 2 x 12 + 3 + 20% = 32 m.
Pipe 150 mm: 3 x 12 + 20% = 43 m.
Fasteners: 32 + 43 / 0.7 = 107 pcs.
Elbows, revisions, couplings - take as 1 piece per 3 m: 32 + 43 / 3 = 55/3 = 20 pieces.
Grids: 8 pcs. (2 for each room).
Switches: 4 pcs.
Foam, sealant. Tube heat exchanger

In order not to complicate the calculations with mathematical calculations, we will provide data from tests already carried out in average form, or rather their results.

The basic principle that must be observed when creating a pipe system is that there must be at least one underground channel pipe per room. This will facilitate the operation of the fans due to atmospheric pressure. Now all that remains is to place required amount pipes in the underground part of the site. They can be laid separately or combined into a common channel (250 mm).

In this description, we propose to take into account not the maximum load, when all rooms are forcedly ventilated at the same time, but the average load, which will be supplied during regular periodic ventilation of different rooms (as happens in real life). This means that there is no need to output a separate channel for each room. It is enough to connect 150 mm air ducts from each room to one common 250 mm channel. The number of common channels is taken at the rate of one channel per 60 m2.

Creating a recuperation field

Recommended layout of the underground part of the pipe heat exchanger: First you need to select the location of the pipes (recovery field). The greater the length of the laid pipes, the more effective the air cooling will be. It should be noted that after the work is completed, this area can be used for planting, landscaping or a children's playground. Under no circumstances should you plant trees on the recuperation field:

We excavate the soil to a freezing depth of plus 0.4 m.
We lay 250 mm pipes with a pitch of at least 700 mm along the axis.
We bring the air intakes to a height of 1 m. It is advisable that they be located in a shaded but well-ventilated place.
Using elbows and adapters, we combine them into a common 250 mm channel, which connects to the house ventilation system (see above).
Attention! In the underground part, use special ground sewer pipes with a thick wall. They do not need to be thermally insulated, but simply covered with soil and spilled with water. Only concreting is allowed if necessary.

Calculation of the amount of work and material consumption:

For a recuperation field we take an area measuring 15x6 m with an area of ​​90 m2.
The volume of soil in the pit at a freezing depth of 0.8 m will be: Vcat = (0.8 + 0.4) x 60 = 72 m3.
Volume of a trench 40 cm wide (10 m from the house): Vtr = 1.2 x 0.4 x 10 = 4.8 m3.
Total volume of excavation work: Vtotal = Vcat + Vtr = 72 + 4.8 = 77 m3.
Sections of 15 m: Notr = a / 0.7 = 6 / 0.7 = 9 pcs., where a is the width of the field.
Total pipe length: L = Notr x 15 + 10 = 9 x 15 + 10 = 145 linear. m.
The consumption of elbows, couplings, adapters is accepted as 2 pcs. x 15 m = 30 pcs.
Advice. The deeper the heat exchanger is installed, the more efficient its operation will be. More than one tier is allowed.

At a certain place, a pit measuring approximately 2x3x3 m is dug. A trench is made from the exit point of the common channel of the house ventilation system to the pit of the future tank, and a 250 mm pipe is laid into it to a depth of 140 cm, through which cooled air will be discharged from the bunker. Along the wall to which the trench approached, a vertical groove is laid to the bottom for a pipe with a diameter of 250 mm. Then the bottom is laid out with bricks or concreted. The bottom of the air tank must be at least 1 meter deeper than the soil freezing level.

Attention! After installing the bottom of the bunker, a 250 mm outlet pipe should be laid.

The beginning of the outlet pipe protrudes from the wall 1/3 of the distance to the opposite wall and is lined with brick protection. A protective grill is installed on the inlet opening.

Filling the tank

It is better to lay the walls out of brick or cast them from concrete (without slag!), since these materials conduct temperature better than others. Cinder block is not suitable due to its thermal insulation properties. The walls and bottom must be carefully waterproofed (roofing felt) on the outside and plastered on the inside to prevent the penetration of organic matter or moisture. The height of the walls is up to ground level minus 20 cm. An inlet hole is made at the top of any wall and air intake pipes are installed. To facilitate the operation of fans, we recommend installing 3 pcs.

After the solution has hardened, the bunker must be filled with large pebbles. Sizes from 200 to 450 mm in diameter. The stone must be clean of organic matter and washed.

The tank is covered with a “lid” made of solid plank flooring on wooden beams, covered waterproofing materials. Turf is laid on top. Then the outlet pipe is connected to the house ventilation system (to the common ventilation duct) and backfilling is performed.

Calculation of the volume of work and consumption of materials:

With an air tank size of 2x3 m and a depth of 3 m, the volume of soil (excavation and stone for filling) will be: V = 2x3x3 = 18 m3 + Vtr = 22.8 m3.
Volume brickwork: Vclad = Swall + Sbottom x 0.125 = ((2x3) x 2 + (3x3) x 2 + 2x3) x 0.065 = 36 x 0.065 = 2.34 m3.
Total pipe length (10 m from the house): L = (10 + 3) + 10% = 15 m.
Number of elbows - 6 pcs. Bunker heat exchanger

If the house has unoccupied basements, they can also be used to create a bunker (air or heat exchange tank) for a stone heat exchanger. Its action is based on the energy intensity of the stone - it gradually increases the ambient temperature and balances the flow of passing air. If there is no free space in the basement, the bunker can be arranged in an area outside the house.

The cost of stone for filling a tank may vary depending on the region of construction.

As can be seen from the calculations, the final cost of air conditioning 1 m2 differs for both options. The main selection factor is the level of occurrence groundwater. If it is high, less than 3 m, then it will not be possible to build a bunker heat exchanger. The pipe one is suitable even with a groundwater level of 1.5 meters.

Installation of fans

The system presented here provides for the synchronous operation of two duct fans - supply and exhaust - installed in each air outlet of the room. This makes it possible to quickly deliver cool fresh air into the room and remove heated air. For effective ventilation, a fan power of 100 W each is sufficient. When choosing a fan, pay attention to the noise level when it operates.

Approximate cost of operation

If you ventilate each room three times during the day for 20 minutes, then we get 1 hour of operation of 8 0.1 kW fans. This is less than 1 kW/hour per day. Per month - 30 kW. At a price of 5 rubles/kW this will be 150 rubles/month.

The service life of recuperators and ventilation ducts at home is limited by the service life of the material. For underground elements - from 50 years, for internal ones - unlimited.

The system does not require maintenance (except for fans - once every 5 years).

Prospects

The described circuit can become the basis for a more complex air conditioning system. It is possible to gradually include additional elements - filters, heating and cooling elements, more powerful fans, automatic control units and others. The air mixture prepared underground has a stable temperature not only in summer, but also in winter, so it can also be used for heating.

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Optimal solution common task maintaining comfortable parameters of the internal environment of the room is ensured only when integrated approach to solving particular problems of heat supply, air conditioning, ventilation and air purification.

N unsatisfactory operation of the ventilation system leads to an increase in the concentration of carbon dioxide and other harmful substances indoors, creates favorable conditions for the development of pathogenic microorganisms and climatic discomfort. Despite a number of advantages that they have natural systems air exchange, very often they are not enough to maintain comfortable parameters. Mechanical systems use equipment to move, purify, and heat/cool air to ensure the creation of comfortable conditions. At the same time, from the point of view of energy efficiency, the need to utilize the heat of the exhaust air becomes obvious.

Air conditioning and recuperation

Supply ventilation is often combined with an air conditioning system, including wall-mounted or duct air conditioners and having air distributors common to the ventilation system (Fig. 1). At the same time, due to additional heating of the supply air by the exhaust air (recuperation), significant (up to 30%) energy savings are achieved. An air conditioner with a mixing function can also be used as an individual PU. fresh air.

Rice. 1. Apartment duct air conditioner

There are also PES with a heat recuperator. Heating of air coming from the street is often carried out with a water (with coolant) or electric heater. In PU apartments, the latter are usually used, since their installation requires less cost. In individual houses, water heaters are often used, which use coolant from autonomous system heating.

The ventilation system may also include a ducted air humidifier or humidification section, allowing you to maintain optimal humidity. For these purposes, steam or “cold” humidifiers with a tap water supply are usually used, for example, isothermal humidifiers Carel humiSteam and compactSteam (Fig. 2) or adiabatic evaporative humidification sections Breezart HumiLite.

Rice. 2. Carel humidifiers

Window and mobile monoblocks

Household monoblock air conditioners It is customary to divide them into those mounted in enclosing structures (the term “window” does not accurately reflect their features), mobile and roof-mounted.

Modern window air conditioners, equipped with systems electronic control, diagnostics and safety, can not only cool, but also heat the room, and also provide fresh air from outside, cleaning it. In fact, the consumer purchases an air conditioner and PU. The manufacturer also managed to significantly reduce the noise level and increase the efficiency of the devices. Today, this subclass also includes inverter models, for example, the RA-08AS air conditioner from Hitachi with a cooling/heating capacity of 2.1/5.6 kW and a maximum noise level of 49 dB. And the Samsung AW05NOBSER model has cooling/drying/ventilation modes and a noise level of up to 48 dB. The air conditioner is equipped with a remote control, an ionizer for mixed atmospheric air and two filters - antibacterial and deodorizing. The weight of the 1.5 kW model is 17 kg.

Mobile air conditioners from Electrolux (Sweden) of the Smart (EACM-E/R) and EACM-10 EZ/N3 series (Fig. 3) can also operate in cooling, ventilation and dehumidification modes, Fairline MAC 2200C air conditioner (EQUATION company, France) implements modes of ventilation, cooling and dehumidification and is designed to serve rooms up to 22 m2.

Rice. 3. Mobile air conditioner Electrolux EACM-10 EZ/N3

Rooftop air conditioners

Stationary devices (Roof-top) with a power of up to tens of kW are usually mounted on the roofs of residential buildings. The scope of application of such air conditioners is offices, apartment buildings, large cottages. On the domestic market they are represented, in particular, by models from McQuay (USA), Mitsubishi Electric (Japan), and Airwell (France). Roof monoblocks can have heating/cooling and ventilation functions.

Thus, the Airwell model HA 35 implements the functions of thermodynamic heating (an electric air heater can be installed in the air duct), cooling and ventilation. With a cooling power of 10.1 kW it consumes from electrical network(three-phase, 400 V) 3.7 kW.

Split systems

Traditional split air conditioners, which are efficient in heating/cooling modes, also require the installation of ventilation systems. Moreover, if automatic control is available, in this case it is necessary to coordinate the algorithms of operation with the air conditioning system.

Air conditioners with a mixture of fresh air, approaching mechanical supply and exhaust ventilation, are more complex and more expensive than traditional devices. Moreover, mechanical supply ventilation is usually considered as a comfortable addition, and if intensive air exchange is necessary, it is recommended to install PVU or duct air conditioners.

Inverter Air Exhanger models from Hitachi (Japan) are among the first in the world wall split systems were equipped with a supply ventilation system. For example, air conditioners RAS-10JH2 and RAS-10JH4 (Fig. 4) implement the function of supply and exhaust ventilation: used air is forcibly removed from the room, and fresh air is supplied instead with a volume of 8-16 m3 / h. In this case, the air can be cooled or heated. Using the remote control, you can select one of six operating modes, in particular, exhaust or air supply.

Rice. 4. Inverter air conditioner RAS-10JH4

Air conditioners are equipped with a sleep mode. If you turn on the fresh air supply in this mode in the summer, the sensor will monitor the room temperature, as well as the humidity and temperature of the outside air. If it is below room temperature, then fresh air will be supplied into the room even after the air conditioner itself is turned off.

The designer inverter air conditioner Aqua Super Match AS09QS2ERA from Haier has an air mixing function. Air conditioning provided supply system“O2-fresh” air exchange system, which maintains a given balance of oxygen and carbon dioxide concentrations in the room. Air mixing is carried out using additional block, mounted on the outdoor unit of the air conditioner, containing a pressure fan and connected to the indoor unit of the air conditioner with a flexible hose-air duct. It does not need to be led into the indoor unit, but rather supplies air directly to the room.

Air supply and exhaust can be carried out both in conjunction with cooling/heating modes, and independently of them. The ventilation system takes fresh air from the street, filters it, effectively trapping carbon monoxide II, formaldehyde, unpleasant odor molecules and bacteria, and delivers it into the room.
If the fresh air supply is turned on in sleep mode in the summer, then in accordance with the signals from sensors that monitor the temperature in the room, humidity and outside air temperature, even when the air conditioner is turned off, fresh air is supplied from the street if its temperature is lower than in the room.

The supply and exhaust mode can be used both with cooling/heating modes and for air exchange. Using the remote control, the consumer can select one of six modes, for example, hood (Hi-Me-Lo) or fresh air supply mode (Hi-Me-Lo). In automatic ventilation mode, the automation analyzes the concentration of oxygen and carbon dioxide in the room and selects the ventilation operating mode - supply or exhaust.

In heating mode, air conditioners can operate at outdoor temperatures down to -20 °C. The noise level of the indoor unit at the minimum compressor speed is 20 dB.

Haier split systems with a mixture of Fresh Air and a UV lamp are energy efficient, provide low noise levels, air dehumidification, and also start at reduced voltage in the electrical network. The HSU-09RG03 air conditioners with ventilation implement automatic control, heating/cooling, independent air dehumidification, and isolated ventilation. The models have a dual air damper and a three-stage filtration system. The presence of a built-in ionizer allows you to effectively maintain a favorable ion balance in the room (2000-3000 ions/cm3 at a distance of 1 m from the indoor unit). Low noise levels and smooth air flow are provided by a large diameter fan with “random” pitch and angled blades.

Daikin devices - FTXR28E, FTXR42E and 2MXU50G, operating in split system mode with two indoor units - have a wide range of functions. The first models supply up to 32 m3/h of fresh air, the latest - up to 22 m3/h per indoor unit.

Daikin's FTXZ25N/RXZ25N differs from its predecessor FTXR28E with a three-zone Intelligent eye occupancy sensor, automatic filter cleaning that reduces energy consumption by 25% and environmentally friendly R32 refrigerant. They, in the same way as in previous models, implement the functions of Ururu Sarara (Fig. 5) - air humidification during heating due to the moisture of street air and dehumidification without cooling remain. For the latter, the heat from the outdoor unit is used.

Rice. 5. Scheme for processing the supply air with its heating and dehumidification

The outside air supplied to the room passes multi-stage cleaning. In the external block - through a rotating manganese catalyst, where all unpleasant odors including exhaust gases. Then, upon entering the indoor unit, the filter separates particles of dust, small debris and pollen, after which the supplied outdoor air is mixed with the indoor air and passed through a photocatalytic filter. There, a high-voltage streamer discharge kills bacteria, viruses and mold spores. Purified air is supplied to the vitamin filter, where it is enriched with vitamins and hyaluronic acid, which prevents the evaporation of water molecules from the surface of the skin.

Several years ago, in some Gree split systems with mixed air, selective membranes began to be installed, which made it possible to increase the oxygen concentration in the air coming from outside by 2-3%. However, at present there are practically no such models on the market, which, however, does not mean that the idea itself is futile. The Oxylife oxygen system can be considered as a further development in this direction. To enrich the air with oxygen, a “molecular sieve” - zeolite - is used.

The system consists of one or more external units (oxygen concentrators) and internal devices (accessories). In the external unit, the air is separated into oxygen and impurities. Internal devices serve to regulate operation external unit and distribution of oxygen in the room, allowing oxygenation of up to four rooms.

VRF systems

Toshiba's SHRM heat recovery air conditioners are of the three-pipe type (a further development of VRF systems). So, if in a conventional air conditioner all internal units work for cooling or heating, then three-pipe units allow you to combine the processes of air conditioning and heating.

Each indoor unit operates in an individual mode - cooling or heating. The heat taken from the cooled areas is transferred to where heating is required. Thus, heating one room (or heating water for hot water supply) occurs at the expense of cooling another.

To implement such a scheme, FS flow distributors are added to the air conditioning system - compact modules with electronic valves that regulate the operation of the heat exchanger of the indoor unit. Three pipes are supplied to the modules, and two pipes come out of it, connected to the internal units. Each of them requires a separate thread distributor. Depending on the number of indoor units operating for cooling or heating, the system selects the priority operating mode of the external unit and distributes refrigerant flows.

Three-pipe air conditioning systems can operate in both cooling-only and heating-only modes, but in this case their energy efficiency will be slightly lower than that of standard ones due to a more complex network and additional elements. But such modes account for no more than 1/5 of the total operating time of the air conditioner. The rest of the time, the consumer can save up to 50% of electricity through heat recovery. The FS distributor weighs 5 kg and does not require drainage. It can be mounted from the indoor unit at a distance of up to 15 m.

Three years ago, Toshiba began producing an improved range of heat recovery systems. Built on a modular principle, they can include three external and up to 48 internal units. The total power of the external units is 84 kW, each of them is equipped with two identical independent double-rotor inverter compressors.

The Gree company (China) offered domestic consumers a multi-zone Home-GMV system with an inverter compressor and air conditioner-water heater functions. The greatest energy efficiency of its operation is ensured when simultaneous work in air cooling and hot water mode. This became possible thanks to a hydraulic module that includes a refrigerant/water heat exchanger and a pump. In the heat exchanger, the refrigerant releases energy, heating the water to 60 °C. According to the designers' calculations, the use of heat pumps for domestic hot water makes the system four times more economical than with an electric heater, and with simultaneous air cooling - six times more economical. The company has developed four modifications of outdoor units with a capacity of 10-16 kW. Indoor units can be wall-mounted, floor-ceiling, cassette and duct. Their cooling capacity is 2.2-14.0 kW. The system operates effectively at external temperatures from -15 to 48 °C. At lower temperatures, it is necessary to use an electric heater built into the storage tank.

PVU and air conditioner

Heat recovery from exhaust air is usually carried out in a heat recovery unit. They often work in conjunction with a ducted or central air conditioner, which is connected to the air duct of the ventilation system. Warm air removed from the premises is used to heat the supply air in the recuperator heat exchanger.

In the cold season, thanks to the use of a recuperator, the costs of using a heating element or water heater are reduced by almost half, and during the off-season periods the recycling efficiency reaches 70%.

Unlike public premises, where the exhaust air usually has an outlet temperature of up to 24 °C, in industrial premises its temperature reaches 50 °C. Therefore, the latter provide the greatest efficiency of operation of PES with recovery.

The problem of heating incoming air can be solved using mixing chambers in which warm (outgoing) air is mixed with cold (incoming) air. But such a solution is acceptable only for public buildings, and for industrial facilities it is often unacceptable, leading to violation of requirements regulatory documents. In this case, it is possible to use only recuperators: cross-flow, plate, rotating, systems with intermediate coolant and etc.

Plate heat exchangers are made of aluminum plates, which are installed in their own section with filters on each line and have an aluminum drain pan. A rotating recuperator, equipped with an electrically driven recovery drum, also makes it possible to utilize the energy of the phase transition of water.

Duct air conditioners effectively solve the problems of ventilation and air conditioning. Their indoor units are installed behind false ceiling, and the air is taken in and supplied by the air ducts of the PPV system.

Duct air conditioners with forced ventilation are equipped with electric or water heaters with a power range of 4.5-24 kW. Depending on the power of the indoor unit, the heaters are made either as a separate section or built into the dispenser unit. To recover heat, a cross-flow heat exchanger made of aluminum plates is used as a recuperator, creating a system of channels for the flow of structurally separated air flows with different temperatures. Air turbulization in the channels ensures effective heat recovery with relatively low aerodynamic resistance.

Due to the possibility of moisture condensation from the exhaust air, a separator with a drain pan and condensate drainage through a siphon is usually placed behind the cross-flow heat exchanger. To avoid icing in winter time year, a thermostat is installed on the heat exchanger to control the position of the bypass valve.

Central air conditioners with exhaust air heat recovery are assembled from standard sections hermetically connected to each other. Depending on the needs of the facility, it is equipped with sections for cooling, heating, humidification, filtration, and noise reduction. To be able to recover heat from air flows, the central air conditioner can be equipped with a cross-flow rotating heat exchanger or a heat recovery section with an intermediate coolant (glycol heat exchanger).

In a rotating heat exchanger, heat is accumulated by a rotating regenerative nozzle - corrugated steel sheet, folded so that channels are formed for horizontal air flow. The wheel-like attachment is rotated by an electric motor. Exhaust air having high temperature, passes through the nozzle and heats it. The nozzle finds itself in a flow of cold supply air, to which it gives off heat. Heat recovery is regulated by changing the engine speed. A separator with a drain pan and condensate drainage through a siphon is installed behind the rotating heat exchanger.

Such heat exchangers allow you to recover up to 80% of heat, cross-flow - up to 70%. Allowable speed of air movement through the heat exchanger is 4.5 m/s, maximum working temperature- 50 °C. A significant disadvantage of rotating heat exchangers is partial mixing of air flows. They are therefore unsuitable for hospitals, chemical and food industries where complete separation of supply and exhaust air is required.

Recuperators with intermediate coolant are used in systems where mixing of air flows is unacceptable, as well as in the case of a large distance between the supply and exhaust units. Glycol solutions are most often used as an intermediate coolant.

The recuperator section with intermediate coolant consists of two heat exchangers with aluminum tubes and aluminum fins. In this case, the heat exchanger located in the exhaust air flow is equipped with a drop eliminator, in the pan of which an overflow pipe is installed, which extends outside the section casing. The heat exchangers are connected by a system of pipelines filled with coolant, which is heated in a heat exchanger-heat receiver, blown with warm moist air, and transfers heat to a heat exchanger-heat sink located in the flow of supply air.

In a central air conditioner, the heat exchanger-heat transmitter, located on the supply side, most often plays the role of a first-stage heater. Recovery efficiency is up to 60%.

In Russia, equipment for exhaust air heat recovery is sold by many companies - Mitsubishi Electric (Lossnay systems, Japan), Clivet (Italy), Wolter, Wolf, Rosenberg, Trumpf (Germany), VTS Clima (Poland), Remak (Czech Republic), Veza "(Moscow region), "Moven" (Moscow Fan Plant), "Korf" (Moscow-St. Petersburg-Novosibirsk), etc., offering various systems with exhaust air heat recovery.

Solutions for energy efficient homes

For a passive house project implemented in Novgorod region, a Comfosystems ventilation system with heat and humidity recovery from the German company Zehnder was chosen (Fig. 6).

Rice. 6. Ventilation grates Comfosystems

This is a supply and exhaust ventilation unit with a cross-counterflow recuperator and a maximum air flow of up to 350 m3/h (ComfoAir 350) at an external static pressure of 250 Pa. The Zehnder Comfofresh air distribution system is a compact arrangement of plastic air ducts round section with special hypoallergenic internal coating Clinside, which does not accumulate dust and does not develop germs. The system also includes Zehnder Comfowell noise suppressors, which make the air flow into the rooms silent.

Before you remove from home exhaust air, the recuperator takes heat from it. At the same time, the air flows do not mix, ensuring the freshness of the supply air. The air coming from the street passes through a four-level filter, thus achieving an environmentally friendly atmosphere in the building.

Additional energy savings during ventilation are provided by preheating of street air, which is carried out using a geothermal heat exchanger (ComfoFond-L). It has a horizontal contour 196 m long, with two branches laid at a depth of 4 and 3 m. The coordinated operation of the ventilation system with the geothermal heat exchanger is ensured by the Zehnder automation system. The installation efficiency is 84%, electricity consumption per 1 m3/h of air is 0.29 W. The ventilation system also features moisture return and humidity control functions.

An important feature of the system is that it allows you to organize individual air supply: a separate air duct is installed in each room (room). Thanks to this, it is possible to accurately calculate the volume and speed of air supply and provide a comfortable microclimate while minimizing energy costs.

Having proper air exchange is a key factor in comfort in the home and the health of household members. And then the thought of creating proper ventilation. IN Lately There’s so much that’s missing on the air conditioning equipment market! It is difficult for an unprepared person to understand what he really necessary to create a comfortable microclimate in the apartment.
Let's figure out what, for example, supply ventilation valves, air handling units and recuperators are used for.

Used in natural and mechanical ventilation systems. The valve has protection against insects, noise, dust, wall freezing and condensation, as well as regulation of the amount of incoming air. You can regulate the flow of air passing through the valve using the handle on the head of the valve or a special cord if the valve is located high. On the valve head there is a scale indicating the degree of valve opening. The valve is continuously adjustable until completely closed. KIV-125 does not require any energy consumption.
How does he work? The existing exhaust hood (vent ducts located in the kitchen and bathrooms), removing exhaust air, creates a vacuum in the apartment, and due to this vacuum, fresh outside air enters the room through the KIV-125 valves.

Advantages:
* Double air purification.
* Built-in two-stage ceramic heater - for ventilation during the cold season.
* Highly efficient fan - for quiet operation (from 21 dB) with minimal power consumption.
* Productivity from 40 to 120 m 3 / h

The air recuperator ventilates your room by removal old air and influx new, cleaned with a filter, indoors. In the process of air exchange, recovery occurs, the transfer of energy from the outgoing air to the incoming air. In this way, the recuperator saves energy spent on heating in winter and air conditioning in summer.

* * * * *
For efficient operation of the supply valve or installation the hood must be active. An active exhaust hood is any stable exhaust system - mechanical (using fans) or natural (ventilation ducts located in the kitchen and bathrooms). To guarantee the operation of ventilation in the apartment in any season, regardless of the floor, it is recommended to install exhaust fans in kitchens and bathrooms.
Recuperators operate regardless of the presence of exhaust ducts. We remember that the tasks of recuperators, in addition to the supply of fresh air, include the removal of exhaust air.
BUT! There is a natural hood in every home. That is why, in our opinion, installing recuperators in residential premises is inappropriate . They are more likely to be suitable for rooms in which there is no hood at all (garage, barn, storage room, etc.). The promised energy savings are also a controversial issue, since the volume of incoming air will be clearly insufficient - no more than 40 m 3 /h. Is this what you wanted to achieve by taking care of the ventilation of your home? And you won’t feel the air warming up in cold weather either.

If you need a valid saving, then we recommend considering supply valves KIV-125. The performance of the valve depends on the vacuum created by the hood:
at a vacuum of 20 Pa (created by mechanical exhaust) - 50 m 3 / h;
at a vacuum of 10 Pa (creates natural exhaust) - 35 m 3 / h.

If you want greater influx of fresh , purified and, if necessary, noticeably heated air, it is worth thinking about the supply ventilation unit.

And one more important point:
for an external hole up to 150 mm (which is necessary for installation, for example, KIV-125 or iFresh) is not required (if the building is not a cultural heritage site):

4.3.7.* Installation of air conditioning and ventilation systems without an outdoor unit with air supply through a hole in the wall with a diameter of up to 0.15 m, hidden by a fence grate, is allowed everywhere (for cultural heritage sites - in agreement with KGIOP).

*Government of the city of St. Petersburg "On approval of the rules for the maintenance and repair of facades of buildings and structures in St. Petersburg" (No. 1135 of September 14, 2006)

An external hole is required for installation of heat exchangers more diameter - 180 mm.

Structurally, an air conditioner with active heat recovery is a monoblock duct unit, which is designed to process air supplied from the street to air-conditioned rooms. The Clivet company produces air conditioners with active heat recovery, which can operate both in cooling mode (in summer and transitional periods) and in heat pump mode (in winter and transitional periods). Figure No. 1 shows appearance the main functional elements of an air conditioner with active heat recovery.

The unit includes the following functional elements:
A full-featured refrigeration circuit designed to cool or heat air supplied from outside to air-conditioned spaces. The refrigeration circuit includes: a rotary compressor, an internal air heat exchanger, an external air heat exchanger, an expansion device - a capillary tube, a four-way capacity control valve.
The automated control system includes a controller, remote control remote control, protection and automation devices.
- A low or medium pressure centrifugal fan on the air supply side is designed to organize the supply of air to the conditioned room through the air duct system.
- Low or medium pressure centrifugal fan on the air exhaust side is designed to organize air exhaust from the conditioned room through the air duct system.
- Air valve with drive designed for mixing supply and recirculation air.
- A highly efficient air filter is designed to clean the air supplied from the street to the premises.
- Electric heater low power(0.5-1 kW) are intended for heating air supplied from the street to the premises during the winter and transition periods
- Drain pan for collecting condensate.
Optionally, the unit can be equipped with the following elements:
- Steam humidifier, which is designed to humidify air supplied indoors from the street.
- Electric heaters of increased power.
- Drainage pump to remove condensate.

Fresh air supply to cold period time leads to the need to heat it to ensure the correct indoor microclimate. To minimize energy costs, supply and exhaust ventilation with heat recovery can be used.

Understanding the principles of its operation will allow you to most effectively reduce heat loss while maintaining a sufficient volume of replaced air. Let's try to understand this issue.

In the autumn-spring period, when ventilating rooms, a serious problem is the large temperature difference between the incoming air and the air inside. The cold flow rushes down and creates an unfavorable microclimate in residential buildings, offices and factories or an unacceptable vertical temperature gradient in a warehouse.

A common solution to the problem is integration into supply ventilation, through which the flow is heated. Such a system requires energy consumption, while a significant volume of output warm air leads to significant heat loss.

The exit of air to the outside with intense steam serves as an indicator of significant heat loss, which can be used to heat the incoming flow

If the air inlet and outlet channels are located nearby, then it is possible to partially transfer the heat of the outgoing flow to the incoming one. This will reduce the energy consumption of the heater or eliminate it altogether. A device for ensuring heat exchange between gas flows of different temperatures is called a recuperator.

In the warm season, when the outside air temperature is significantly higher than room temperature, a recuperator can be used to cool the incoming flow.

Design of a unit with a recuperator

The internal structure of supply and exhaust ventilation systems is quite simple, so it is possible to independently purchase and install them element by element. If assembly or self-installation is difficult, you can purchase ready-made solutions in the form of standard monoblock or individual prefabricated structures to order.

An elementary device for collecting and discharging condensate is a tray located under the heat exchanger with a slope towards the drain hole

Moisture is removed into a closed container. It is placed only indoors to avoid freezing of the outflow channels at sub-zero temperatures. There is no algorithm for reliable calculation of the volume of water received when using systems with a recuperator, so it is determined experimentally.

Reusing condensate for air humidification is undesirable, since water absorbs many pollutants such as human sweat, odors, etc.

You can significantly reduce the volume of condensate and avoid problems associated with its occurrence by organizing a separate exhaust system from the bathroom and kitchen. It is in these rooms that the air has the highest humidity. If there are several exhaust systems air exchange between the technical and residential areas must be limited by installing check valves.

If the exhaust air flow is cooled to negative temperatures inside the recuperator, condensate turns into ice, which causes a reduction in the open cross-section of the flow and, as a consequence, a decrease in volume or a complete cessation of ventilation.

For periodic or one-time defrosting of the recuperator, a bypass is installed - a bypass channel for the movement of supply air. When a flow bypasses the device, heat transfer stops, the heat exchanger heats up and the ice passes into a liquid state. The water flows into the condensate collection tank or evaporates outside.

The principle of the bypass device is simple, therefore, if there is a risk of ice formation, it is advisable to provide such a solution, since heating the recuperator by other means is complex and time-consuming

When the flow passes through the bypass, there is no heating of the supply air through the recuperator. Therefore, when activating this mode, it is necessary automatic switching on heater.

Features of various types of recuperators

There are several structurally different options for implementing heat exchange between cold and heated air flows. Each of them has its own distinctive features, which determine the main purpose for each type of recuperator.

The design of the plate recuperator is based on thin-walled panels, connected alternately in such a way as to alternate the passage of flows of different temperatures between them at an angle of 90 degrees. One of the modifications of this model is a device with finned channels for air passage. It has a higher heat transfer coefficient.

Alternate passage of warm and cold air flow through the plates is realized by bending the edges of the plates and sealing the joints with polyester resin

Heat exchange panels can be made of various materials:

• copper, brass and aluminum-based alloys have good thermal conductivity and are not susceptible to rust;
• plastic made from a hydrophobic polymer material with a high thermal conductivity coefficient and low weight;
• hygroscopic cellulose allows condensation to penetrate through the plate and back into the room.

The disadvantage is the possibility of condensation forming when low temperatures. Due to the small distance between the plates, moisture or ice significantly increases aerodynamic drag. In case of freezing, it is necessary to block the incoming air flow to warm the plates.

The advantages of plate recuperators are as follows:

• low cost;
• long service life;
• long period between preventive maintenance and ease of its implementation;
• small dimensions and weight.

This type of recuperator is most common for residential and office premises. It is also used in some technological processes, for example, to optimize fuel combustion during the operation of furnaces.

Drum or rotary type

The operating principle of a rotary recuperator is based on the rotation of a heat exchanger, inside of which there are layers of corrugated metal with high heat capacity. As a result of interaction with the outgoing flow, the drum sector is heated, which subsequently gives off heat to the incoming air.

The fine-mesh heat exchanger of a rotary recuperator is susceptible to clogging, so you need to pay special attention to the quality operation of fine filters

The advantages of rotary recuperators are as follows:

• quite high efficiency compared to competing types;
• return of a large amount of moisture, which remains in the form of condensation on the drum and evaporates upon contact with incoming dry air.

This type of recuperator is less often used for residential buildings for apartment or cottage ventilation. It is often used in large boiler houses to return heat to furnaces or for large industrial or commercial premises.

However, this type of device has significant disadvantages:

• a relatively complex design with moving parts, including an electric motor, drum and belt drive, which requires constant maintenance;
• increased noise level.

Sometimes for devices of this type you can come across the term “regenerative heat exchanger”, which is more correct than “recuperator”. The fact is that a small part of the exhaust air gets back due to the loose fit of the drum to the body of the structure.

This imposes additional restrictions on the ability to use devices of this type. For example, polluted air from heating stoves cannot be used as a coolant.

Tube and casing system

A tubular type recuperator consists of a system of thin-walled tubes of small diameter located in an insulated casing, through which there is an influx of outside air. The casing removes warm air from the room, which heats the incoming flow.

Warm air must be discharged through the casing, and not through a system of tubes, since it is impossible to remove condensate from them

The main advantages of tubular recuperators are as follows:

• high efficiency due to the countercurrent principle of movement of the coolant and incoming air;
• simplicity of design and absence of moving parts ensures low noise levels and rarely requires maintenance;
• long service life;
• the smallest cross-section among all types of recovery devices.

Tubes for this type of device use either light-alloy metal or, less commonly, polymer. These materials are not hygroscopic, therefore, with a significant difference in flow temperatures, intense condensation may form in the casing, which requires a constructive solution for its removal. Another disadvantage is that the metal filling has significant weight, despite its small dimensions.

The simplicity of the tubular recuperator design makes this type of device popular for self-made. Typically used as an outer casing plastic pipes for air ducts, insulated with polyurethane foam shell.

Device with intermediate coolant

Sometimes the supply and exhaust air ducts are located at some distance from each other. This situation may arise due to technological features building or sanitary requirements for reliable separation of air flows.

In this case, an intermediate coolant is used, circulating between the air ducts along insulated pipeline. Water or a water-glycol solution is used as a medium for transferring thermal energy, the circulation of which is ensured by operation.

The recuperator with intermediate coolant is a volumetric and expensive device, whose use is economically justified for premises with large areas

If it is possible to use another type of recuperator, then it is better not to use a system with an intermediate coolant, since it has the following significant disadvantages:

• low efficiency compared to other types of devices, therefore for small rooms such devices are not used with low air flow;
• significant volume and weight of the entire system;
• the need for an additional electric pump to circulate the liquid;
• increased noise from the pump.

There is a modification of this system when, instead of forced circulation The heat exchange fluid uses a medium with a low boiling point, such as freon. In this case, movement along the contour is possible naturally, but only if the supply air duct is located above the exhaust air duct.

Such a system does not require additional energy costs, but only works for heating when there is a significant temperature difference. In addition, it is necessary to fine-tune the point of change in the state of aggregation of the heat exchange fluid, which can be realized by creating required pressure or a certain chemical composition.

Main technical parameters

Knowing the required performance of the ventilation system and the heat exchange efficiency of the recuperator, it is easy to calculate savings on air heating for a room under specific climatic conditions. By comparing the potential benefits with the costs of purchasing and maintaining the system, you can reasonably make a choice in favor of a recuperator or a standard air heater.

Equipment manufacturers often offer a model line in which ventilation units with similar functionality differ in the volume of air exchange. For residential premises, this parameter must be calculated according to Table 9.1. SP 54.13330.2016

Efficiency

The efficiency of a recuperator is understood as the efficiency of heat transfer, which is calculated using the following formula:

K = (T p – T n) / (T v – T n)

Wherein:

• T p – temperature of the air entering the room;
• Tn – outside air temperature;
• T in – room air temperature.

Maximum efficiency value at standard and certain temperature conditions indicated in the technical documentation of the device. Its actual figure will be slightly less.

In the case of self-manufacturing of a plate or tubular recuperator, in order to achieve maximum heat transfer efficiency, you must adhere to the following rules:

• The best heat transfer is provided by counter-flow devices, then cross-flow devices, and the least by unidirectional movement of both flows.
• The intensity of heat transfer depends on the material and thickness of the walls separating the flows, as well as on the duration of the air inside the device.

E (W) = 0.36 x P x K x (T in - T n)

where P (m 3 / hour) – air flow.

Calculation of the efficiency of the recuperator in monetary terms and comparison with the costs of its acquisition and installation for two-story cottage with a total area of ​​270 m2 shows the feasibility of installing such a system

The cost of recuperators with high efficiency is quite high; they have a complex design and significant dimensions. Sometimes you can get around these problems by installing several simpler devices so that the incoming air passes through them sequentially.

Ventilation system performance

The volume of air passed through is determined by static pressure, which depends on the power of the fan and the main components that create aerodynamic resistance. As a rule, its exact calculation is impossible due to the complexity of the mathematical model, therefore experimental studies are carried out for standard monoblock structures, and components are selected for individual devices.

The fan power must be selected taking into account the throughput of installed heat exchangers of any type, which is indicated in the technical documentation as the recommended flow rate or volume of air passed by the device per unit of time. As a rule, the permissible air speed inside the device does not exceed 2 m/s.

Otherwise, at high speeds, a sharp increase in aerodynamic resistance occurs in the narrow elements of the recuperator. It leads to unnecessary costs electricity, ineffective heating of outside air and reduced service life of fans.

The graph of pressure loss versus air flow rate for several models of high-performance recuperators shows a nonlinear increase in resistance, so it is necessary to adhere to the requirements for the recommended air exchange volume specified in the technical documentation of the device

Changing the direction of air flow creates additional aerodynamic drag. Therefore, when modeling the geometry of an indoor air duct, it is desirable to minimize the number of pipe turns by 90 degrees. Air diffusers also increase resistance, so it is advisable not to use elements with complex patterns.

Dirty filters and grilles create significant interference with flow, so they must be periodically cleaned or replaced. One effective way to assess clogging is to install sensors that monitor the pressure drop in areas before and after the filter.

Conclusions and useful video on the topic

Operating principle of rotary and plate recuperator:

Measuring the efficiency of a plate-type recuperator:

Household and industrial systems ventilation systems with an integrated recuperator have proven their energy efficiency in retaining heat indoors. Now there are many offers for the sale and installation of such devices, both in the form of ready-made and tested models, and on individual orders. You can calculate the necessary parameters and perform installation yourself.

If you have any questions while reading the information or find any inaccuracies in our material, please leave your comments in the block below.