Recovery is the process of returning the maximum amount of energy. In ventilation, recovery is the process of transferring thermal energy from exhaust air to supply air. There are many different types of recuperators, and in this article we will talk about each of them. Each type of recuperator is good in its own way and has unique advantages, but any of them will allow you to save at least 50%, and more often up to 95%, on heating the supply air in winter.
The process of heat transfer from exhaust air to supply air is very interesting. Next, we will begin to disassemble each type of air recuperator so that you can more easily understand what it is and which recuperator you need.
The most popular type of recuperators, or more precisely, air handling units with a plate recuperator. It gained its popularity due to the simplicity and reliability of the design of the recuperator heat exchanger itself.
The principle of operation is simple - two air flows (exhaust and supply) intersect in the heat exchanger of the recuperator, but in such a way that they are separated by walls. As a result, these flows do not mix. Warm air heats the walls of the heat exchanger, and the walls heat the supply air. The efficiency of plate recuperators (plate recuperator efficiency) is measured as a percentage and corresponds to:
45-78% for metal and plastic heat exchangers of recuperators.
60-92% for plate recuperators with cellulose hygroscopic heat exchangers.
This jump in efficiency towards cellulose recuperators is due, firstly, to the return of moisture through the walls of the recuperator from the exhaust air to the supply air, and secondly, to the transfer of latent heat in the same moisture. Indeed, in recuperators, the role is played not by the heat of the air itself, but by the heat of the moisture contained in it. Air without moisture has a very low heat capacity, and moisture is water... with a known high heat capacity.
For all recuperators, except cellulose ones, a drainage outlet is required. Those. When planning the installation of a recuperator, you need to remember that a sewerage supply is also required.
So, the pros:
1. Simplicity of design and reliability.
2. High efficiency.
3. No additional electricity consumers.
And, of course, the downsides:
1. For such a recuperator to function, both supply and exhaust must be supplied to it. If the system is designed from scratch, then this is not a minus at all. But if the system already exists and the supply and exhaust are located at a distance, it is better to use.
2. At sub-zero temperatures, the heat exchanger of the recuperator may freeze. To defrost it, it is necessary either to stop or reduce the air supply from the street, or to use a bypass valve that allows supply air to bypass the heat exchanger while it is defrosted by exhaust air. With this defrosting mode, all the cold air enters the system bypassing the recuperator and a lot of electricity is required to heat it. The exception is cellulose plate recuperators.
3. Basically, these recuperators do not return moisture and the air supplied to the premises is too dry. The exception is cellulose plate recuperators.
The second most popular type of recuperator. Of course... High efficiency, does not freeze, more compact than a plate type, and even returns moisture. Some advantages.
The rotary heat exchanger is made of aluminum, wound in layers on the rotor, with one sheet being flat and the other zigzag. To allow air to pass through. Driven by an electric drive via a belt. This “drum” rotates and each part of it heats up as it passes through the exhaust zone, and then moves to the supply zone and cools, thereby transferring heat to the supply air.
A purge sector is used to protect against air flows.
A new and not very well-known type of air recuperator. Rooftop heat exchangers actually use plate heat exchangers and sometimes rotary heat exchangers, but we decided to make them a separate type of heat exchangers, because... A roof-mounted recuperator is a specific, separate type of air handling unit with a recuperator.
Roof-mounted heat exchangers are suitable for large single-volume premises and are the pinnacle of ease of design, installation and operation. To install it, it is enough to make the required window in the roof of the building, install a special “glass” that distributes the load, and install a roof heat exchanger in it. It's simple. Air is taken from under the ceiling in the room, and supplied, according to the customer’s wishes, either from under the ceiling or into the breathing zone of workers or visitors to shopping centers.
Recuperator with intermediate coolant:
And this type of recuperator is suitable for existing ventilation systems “separate supply - separate exhaust”.
Well, or if it is impossible to build a new ventilation system with any type of recuperator, which involves supplying supply and exhaust to one room. But it is worth remembering that both plate and rotary heat exchangers have higher efficiency than glycol ones.
Until recently, supply and exhaust ventilation with an air recuperator was used quite rarely in Russia, until experts came to the conclusion that such a system was a necessity. The operation of ventilation is based on the principle of recovery. This is the name of the process in which part of the heat is returned from exhaust air. Leaving the room, warm air partially heats the oncoming cold flow in the heat exchanger. Thus, completely “exhausted” air goes outside, and not only fresh, but also already heated air enters the room.
Why is it high time to abandon the old type of exhaust ventilation?
Why is traditional natural exhaust ventilation, which has been installed in private houses, apartments and buildings for many years, no longer effective? The fact is that in this case, through frames, doorways and cracks, there should be a continuous penetration of air into the room, but if sealed plastic double-glazed windows are installed, the air flow is greatly reduced and, as a result, the natural exhaust ventilation system ceases to function normally.
In order for the air temperature in the premises to be comfortable, in winter the air needs to be heated, for which in our country, homeowners spend huge amounts of money, because... cold weather in our country lasts 5-6 months. And although the heating season is shorter, huge resources are still spent on heating the supply air. However, the disadvantages of natural exhaust ventilation do not end there. Not only cold but also dirty air enters the room from the street, and drafts also occur periodically. There is no way to control the volume of these air flows. It turns out that due to unbalanced ventilation, a lot of money is literally thrown into the wind, because people are forced to pay for heating the air, which flies down the chimney in a couple of minutes. Since energy prices are rising year after year, it is not surprising that the question of reducing heating costs sooner or later arises in every thrifty person who does not want to “heat the street” at his own expense.
How to save heat in your home
To save heat in the ventilation system - heating the cold supply air due to the warm air removed from the room, special recuperator units are designed. A cassette is built into supply and exhaust ventilation units to ensure air heat exchange. Coming out through it, the exhaust air transfers heat to the walls of the heat exchanger, while the cold air flowing into the room is heated by the walls. This principle is the basis for the operation of plate and rotary heat exchangers, which have currently gained popularity in the market of ventilation units.
Are there any disadvantages to plate recuperators?
In devices of this type, air flows are, as it were, cut by plates. These supply and exhaust systems, in addition to many advantages, which will be discussed later, also have one drawback: on the side where the exhaust air exits, ice forms on the plates. The problem is explained simply: as a result of the fact that the heat exchange plate and the exhaust air have different temperatures, condensation forms, which, in fact, turns into ice. Air begins to pass through frozen plates with enormous resistance, and ventilation performance drops sharply, and the recovery process practically stops until the plates are completely thawed.
The process can be compared to taking a bottle of lemonade out of the freezer. The glass would instantly be covered first with a white film, and then with drops of water. Is it possible to combat the problem of recuperator freezing? Experts found a way out by installing a special bypass valve in ventilation systems with recovery. As soon as the plates are covered with a layer of ice, the bypass opens, and the supply air for some time bypasses the recuperator cassette, entering the room with virtually no heating. At the same time, the recuperator plates are defrosted quite quickly due to the removed exhaust air, and the resulting water is collected in the drainage bath. The bath is connected to a drainage system that goes into the sewer system, and all condensate is drained there. The recuperator begins to work effectively again, and air exchange is restored.
When the cassette defrosts, the valve closes again, however, there is one “but” here. When air does not enter the heat exchanger and bypasses it, energy savings are minimized. This is due to the fact that the supply air, as a rule, in addition to the heat exchanger plates, heats up the built-in air heater - exactly the same as that found in simple air supply units, but with significantly less power. How to deal with this? Is it possible to deal with ice without losing money?
Supply and exhaust ventilation units with heat recovery
Manufacturers of recuperators have found a solution to this serious problem. Thanks to the invention of new technology, the moisture that settles on the walls of the heat exchanger on the outgoing air side begins to be absorbed into them and moves to the supply air side - moistening it. Thus, almost all the moisture in the removed air gets back into the room. What makes this process possible? Engineers achieved this effect by creating cassettes made of hygroscopic cellulose. In addition, many hygroscopic celluloses do not have bypasses and do not connect to the drainage system with the bathtub and plumbing. All moisture is utilized by air currents, and it remains almost entirely in the room. So, using a cellulose heat exchanger in the recuperator, you no longer need to use a bypass and direct air bypassing the recuperator plates.
As a result, the efficiency of the recuperator was increased to 90%! This means that the supply air from the street will be 90% heated by the exhaust air. At the same time, recuperators can operate without problems even in cold weather, down to -30 degrees Celsius. Such installations are perfect for residential premises, apartments, country houses and cottages, preserving and maintaining the necessary humidity and air exchange in winter and summer, they create and maintain the necessary indoor microclimate all year round, while saving a lot of money. However, it should be remembered that recuperators with cellulose heat exchangers, like all others, are capable of freezing, which over time can lead to failure of the heat exchange cassette. In order to completely eliminate the possibility of freezing, it is necessary to install frost protection. Also, with all their positive qualities, recuperators with a paper heat exchanger cannot be used for rooms with a high moisture content, in particular for. For wet rooms, including swimming pools, it is necessary to use supply and exhaust ventilation units with an aluminum plate heat exchanger.
Diagram and operating principle of a supply and exhaust ventilation system with a recuperator
Let's assume that it is winter outside and the air temperature outside the window is -23 0 C. When the air handling unit is turned on, street air is sucked in by the unit using a built-in fan, passes through the filter and hits the heat exchange cassette. Passing through it, it heats up to +14 0 C. As we see, in winter cold, the installation is not able to completely warm the air to room temperature, although for many, such heating may be sufficient, so after the recuperator, the supply air can go directly to room, or if there is a so-called “air reheat” in the recuperator, passing through it, the air is heated to +20 0 C and only fully heated air enters the room. The reheater is a low-power electric or water heater with a power of 1-2 kW, which can, if necessary, turn on at low outside temperatures and heat the air to a comfortable room temperature. In the configurations of recuperators from various manufacturers, as a rule, it is possible to choose a water or electric reheater. On the contrary, room air with a temperature of +18 0 C (+20 0 C), sucked from the room by a fan built into the installation, passing through a heat exchange cassette, is cooled by the supply air and goes outside from the recuperator, having a temperature of -15 0 C.
What will the air temperature be after the recuperator in winter and summer?
There is a fairly simple way to calculate for yourself what temperature the air will enter the room after the recuperator. How effectively will the supply air be heated and will it be heated at all? What will happen to the air in the recuperator in the summer?
Winter
The picture shows that the street air is 0 0 C, the efficiency of the recuperator is 77%, while the temperature of the air entering the room is 15.4 0 C. How much will the air warm up if the temperature outside is, for example, -20 0 C? There is a formula for calculating the supply air for a recuperator depending on its efficiency, outdoor and indoor air temperature:
t (after the recuperator)=(t (indoors)-t (outdoors))xK (recuperator efficiency)+t (outdoors)
For our example, it turns out: 15.4 0 C = (20 0 C - 0 0 C) x 77% + 0 0 C If the temperature outside the window is -20 0 C, in the room +20 0 C, the efficiency of the recuperator is 77%, then the air temperature after the recuperator it will be: t=((20-(-20))x77%-20=10.8 0 C. But this is, of course, a theoretical calculation, in practice the temperature will be slightly lower, about +8 0 C.
Summer
The air temperature after the recuperator in summer is calculated similarly:
t (after the recuperator)=t (outdoors)+(t (indoors)-t (outdoors))xK (recuperator efficiency)
For our example it turns out: 24.2 0 С=35 0 С+(21 0 С-35 0 С)х77%
Diagram and operating principle of a supply and exhaust ventilation system with a rotary heat exchanger
The principle of operation of a rotary recuperator is based on the exchange of heat between the incoming and outgoing air flow in the ventilation system through a rotary aluminum heat exchanger, which, rotating at different speeds, allows this process to be carried out at different intensities.
Which recuperator is better?
Today, recuperators from different manufacturers are available for sale, differing in many respects: operating principle, efficiency, reliability, economy, etc. Let's look at the most popular types of recuperators and compare their advantages and disadvantages.
1. Plate recuperator with aluminum heat exchanger.
The price of such a recuperator is quite low compared to other types of recuperators, which is undoubtedly one of its advantages. The air flows in the device do not mix; they are separated by aluminum foil. One of the disadvantages is the low performance at low temperatures, because... The heat exchanger freezes periodically and must thaw frequently. It is logical that energy costs are rising. It is also not advisable to install them in residential premises, because in winter, during the operation of the recuperator, all moisture is removed from the air in the room and its constant humidification is required. The main advantage of aluminum plate heat exchangers is that they can be installed for ventilation of swimming pools.
2. Plate recuperator with a plastic heat exchanger. The advantages are the same as the previous option, but the efficiency is higher due to the properties of plastic. 
3. Plate recuperator with a cellulose heat exchanger and a single cassette. Despite the fact that the air flows are separated by paper partitions, moisture quietly permeates the walls of the heat exchanger. An important advantage is that the saved heat and moisture are returned to the room. Due to the fact that the heat exchanger is practically not subject to freezing, no time is wasted on defrosting it, and the efficiency of the device increases significantly. If we talk about the disadvantages, they are as follows: recuperators of this type cannot be installed in swimming pools, as well as in any other rooms where there is excess humidity. In addition, the recuperator cannot be used for drying. Very often, like this.
4. Rotary recuperator. It is characterized by high efficiency, but this figure still remains lower than if a plate installation with a double cassette was used. A distinctive feature is low energy consumption. As for the shortcomings, we note the following points, since the oncoming air flows of the rotary heat exchanger are not ideally separated; a small amount of air removed from the room (albeit insignificant) enters the supply air. The device itself is quite expensive, because... complex mechanics are used. Finally, a rotary heat exchanger must be serviced more often than other air handling units and its installation in wet rooms is not advisable.
Recuperators for apartments and country houses
| Mitsubishi Lossney | Electrolux EPVS |
DAIKIN |
Systemair | SHUFT |
What determines the price of a recuperator?
First of all, the price of a recuperator depends on the performance of the entire ventilation system. A professional designer will be able to develop a competent project that satisfies exactly your conditions and requirements, the quality of which will determine not only the efficiency of the entire system, but also your further costs for its maintenance. Of course, you can select the equipment yourself, including air ducts and grilles, but it is advisable that a specialist deal with the identified issues. Developing a project costs extra money, and at first glance, such expenses may seem quite substantial to some, but if you calculate how much money will remain in your budget as a result thanks to competent planning, you will be surprised.
When choosing a recuperator yourself, first of all pay attention to the price and the promised quality. Is the device worth the stated amount? Or will you simply overpay for a new product or brand? The equipment is not cheap and takes several years to pay for itself, so the choice of device should be approached very responsibly.
Be sure to check the availability of product certificates and find out how long the warranty period is valid. Usually the warranty is given not for the recuperator, but for its components. The better the quality of components, assemblies and other components, the more expensive the purchase will be. The reliability of the system is assessed based on the strengths and weaknesses of the product. Nobody offers a natural, ideal option, but finding the best solution for a specific room is quite possible.
How to choose an air handling unit with a recuperator
First of all, ask the seller the following questions:
1. Which company produces the product? What is known about her? How many years on the market? What are the reviews?
2. What is the system performance? These data can be calculated by specialists whom you contact for advice, including specialists from our company. To do this, you must indicate the exact parameters of the premises; it is advisable to provide the layout of an apartment, office, country house, cottage, etc.
3. What will be the resistance of the air duct system to air flow after installing a particular model? These data must also be calculated by designers for each individual case. The calculations take into account all diffusers, duct bends and much more. The model and power of the recuperator are selected taking into account the so-called “operating point” - the ratio of air flow and air duct resistance.
4. What energy consumption class does the recuperator belong to? How much will it cost to maintain the system? How much electricity can you save? You need to know this in order to calculate expenses for the heating season.
5. What is the declared Efficiency Factor of the installation and the real one? The efficiency of recuperators depends on the temperature difference between indoors and outdoors. This indicator is also influenced by such parameters as: type of heat exchange cassette, air humidity, layout of the system as a whole, correct placement of all components, etc.
Let's see how efficiency can be calculated for different types of recuperators.
- If the heat exchanger of a plate recuperator is made of paper, then the efficiency will be, on average, 60-70%. The installation does not freeze, or rather, this happens extremely rarely. If the heat exchanger needs to be defrosted, the system itself reduces the performance of the installation for some time.
- The aluminum plate heat exchanger demonstrates high efficiency - up to 63%. But the recuperator will be less productive. The efficiency here will be 42-45%. This is due to the fact that the heat exchanger must often thaw. If you want to eliminate freezing, you will have to use much more electricity.
- A rotary recuperator shows high efficiency if the rotor speed is regulated by “automation”, guided by the readings of temperature sensors that are installed both indoors and outdoors. Rotary heat exchangers are also susceptible to freezing, as a result of which the efficiency decreases in the same way as plate heat exchangers made of aluminum.
Ecology of consumption. Estate: Heat loss is a serious problem that construction science is struggling with. Effective insulation, sealed windows and doors only partially solve this problem. Heat leakage through walls, windows, roofs and floors can be significantly reduced. Despite this, energy still has one more wide path to “escape.” This is ventilation, which is impossible to do without in any building.
Heat loss is a serious problem that construction science is struggling with. Effective insulation, sealed windows and doors only partially solve this problem. Heat leakage through walls, windows, roofs and floors can be significantly reduced. Despite this, energy still has one more wide path to “escape.” This is ventilation, which is impossible to do without in any building.
It turns out that in winter we spend precious fuel on heating rooms and at the same time continuously throw heat out into the street, letting in cold air.
The problem of energy saving can be solved using a heat recuperator. In this device, warm indoor air heats outdoor air. This achieves considerable savings on heating costs (up to 25% of the total cost).
In the summer, when it is hot outside and the air conditioner is running in the house, the recuperator also brings benefits. It cools the hot incoming stream, reducing air conditioning costs.
Let's take a closer look at household heat recovery units to have an idea of their structure, advantages and features of choice.
Types, principle of operation and design of recuperators
The idea of using the heat from indoor air to heat outdoor air turned out to be very fruitful. It was the basis for the operation of all recuperators.
Today, three types of such devices are used:
- lamellar;
- rotary;
- recirculating water.
The most common and simplest in design are plate recuperators. They are non-volatile, compact, reliable in operation and have a fairly high efficiency (40-65%).
The main working part of such a device is a cassette, inside of which parallel plates are installed. The air leaving and entering the room is cut by them into narrow streams, each of which goes along its own channel. Heat exchange occurs through the plates. Street air is heated, and indoor air cools and is released into the atmosphere.
Operating principle of a plate recuperator
The main disadvantage of plate installations is freezing in severe frosts. Condensate settling in the recovery unit turns into ice and sharply reduces the performance of the device. Three ways have been found to combat this phenomenon.
The first is installing a bypass valve. Having received a signal from the sensor, it allows a cold flow to bypass the block. Only warm air passes through the plates, defrosting the ice. After defrosting and draining the condensate, the valve restores normal operation of the system.
The second option is to use plates made of hygroscopic cellulose. Water settling on the walls of the cassette is absorbed into them and penetrates into the channels through which the supply air moves. This solves two problems at once: eliminating condensation and humidification.
The third method is to preheat the cold stream to a temperature that prevents the water from freezing. To do this, a heating element is installed in the supply ventilation duct. The need for it arises when the outside air temperature is below -10C.
In recent years, plate reversible units have appeared on the market. Unlike direct-flow devices, they operate in two steps: the first is the release of warm air into the street, the second is the suction of cold air through a heated block.
Operating principle of reversible installation
Another type of installation is rotary recuperators. The efficiency of such devices is significantly higher than that of plate devices (74-87%).
The operating principle of the rotary unit is to rotate a cassette with cells in the flow of incoming and outgoing air. Moving in a circle, the channels alternately pass warm internal and cold external flows. In this case, the moisture does not freeze, but saturates the supply air.
It should be noted that the supply and exhaust unit with a rotary type recuperator allows you to smoothly regulate the heat transfer. This is done by changing the rotation speed of the cassette. The main disadvantage of rotary systems is the high cost of maintenance. In terms of reliability, they are also inferior to plate ones.
The next type is a recirculating water installation. It is the most complex in design. Heat transfer here is not carried out through the plates or rotor, but with the help of antifreeze or water.
The first liquid-air heat exchanger is installed on the exhaust duct, and the second on the suction duct. The work is carried out according to the principle of a heater: indoor air heats water, and it heats outdoor air.
The efficiency of such a system does not exceed that of plate recuperators (50-65%). The high price that one has to pay for the complexity of the design is justified by the only advantage: the units of such an installation can be placed not in one building, but in supply and exhaust ventilation areas remote from each other. For powerful industrial systems this is of great importance. Such devices are not installed in small buildings.
Features of choosing a recuperator
Having become familiar with the operating features of recuperation units, it’s time to move on to the practical part – the selection criteria for performing specific tasks.
The first thing you need to pay attention to is the installation method. Domestic supply and exhaust ventilation with heat recovery can be installed in its working position in several ways:
- Inside the wall. The housing is mounted in a pre-drilled hole. A cap is placed on the outside, and a grille and control unit on the inside.
- Indoors. The installation is hung on the wall. A grille or cap is placed outside.
- Outdoor placement. The advantages of this solution are obvious: minimum noise and space saving. The duct design of the device allows it to be placed on balconies and loggias, as well as simply on the facade of a building.
Another parameter that needs to be taken into account when purchasing is the number of fans. Budget air recuperators for the home are equipped with one ventilation unit that operates for both supply and exhaust.
More expensive devices have 2 fans. One of them pumps in and the other exhausts air. The performance of such devices is higher than that of single-fan devices.
When purchasing, you should also pay attention to the presence of an electric heater. With its help, freezing of the cassette is prevented and the lower temperature limit of the device’s operation is increased.
Climate control function. Allows you to accurately set the temperature to which the recuperator will heat the air.
Possibility of humidity control. This parameter significantly affects the comfort of the microclimate. A standard recuperator dries the air, removing moisture from it.
Presence or absence of a filter. An additional option that has a positive effect on the sanitary characteristics of the air mixture.
An important parameter that requires attention is the temperature of the pumped air. In different models, its value may differ significantly. The widest possible range of operating temperatures from -40 to +50C is rare for household devices.
Therefore, in addition to taking into account the optimal performance in m3/hour, when purchasing, choose a device that can fully operate in your climatic conditions.
Performance calculation
Detailed calculations of the operation of recuperators in the supply and exhaust ventilation system are quite complex. Here we have to take into account many factors: the frequency of air exchange in the premises, the cross-section of the channels, the speed of air movement, the need to install mufflers, etc. Only experienced engineers can competently perform such a task.
The average consumer can use a simplified method to correctly navigate when purchasing a device.
The performance of the recuperator directly depends on the sanitary standard of air flow per person. Its average value is 30 m3/hour. Therefore, if 4 people permanently live in an apartment or private house, then the installation productivity should be at least 4x30 = 120 m3/hour.
The own electrical power of household recuperators is small (25-80 W). It is determined by the level of energy consumption of duct fans. In installations with electric heating of the incoming flow, heating elements with a total power of 0.8 to 2.0 kW are installed.
Popular brands and approximate prices
When choosing a household recuperator, you should focus on manufacturers and models that have earned high customer ratings. As an example, we can cite the products of foreign companies Electrolux (Electrolux), Mitsubishi (Mitsubishi), Marley (Marley).
Recuperator for small premises Mitsubishi Electric VL-100EU5-E. Air consumption 105 m3/h. Price from 21,000 rub.
Popular model from Electrolux. Estimated retail price from 42,000 rubles.
The 2017 price tags for household installations of these brands start at 22,000 rubles and end at 60,000 rubles.
MARLEY MENV-180. Air consumption 90 m3/hour. Cost from 27,500 rub.
The equipment of Russian and Ukrainian companies Vents (Vents), Vakio (Vakio), Prana and Zilant has proven itself well. Not inferior to foreign analogues in performance and reliability, they are often more affordable.
Installation of Vakio. Capacity 60 m3/h in recovery mode, up to 120 m3/h in supply ventilation mode. Price from 17,000 rub.
The estimated cost of air recovery systems from these companies (capacity from 120 to 250 m3/hour) ranges from 17,000 to 55,000 rubles.
Prava 200G. Inflow - 135 m3/h, exhaust - 125 m3/h. The recommended area for servicing the system is up to 60 m2.
The nature of reviews about air recuperators is mostly positive. Many owners note that with their help, the problem of excess humidity, which caused the appearance of mold and mildew in the premises, was solved.
In calculations of the payback period for this equipment, figures from 3 to 7 years are given. We did not find any data from instrumental measurements regarding real energy savings on forums dedicated to this topic.
Briefly about self-assembly
Most photo and video instructions for making recuperators yourself discuss plate models. This is the simplest and most affordable option for the home craftsman.
The main part of the structure is the heat exchanger. It is made from galvanized steel, cut into plates measuring 30x30 cm. To create channels at the edges and in the middle of each section, plastic strips 4 mm thick and 2-3 cm wide are glued with silicone.
The heat exchanger is assembled by placing and alternately rotating the plates at an angle of 90 degrees relative to each other. This creates isolated channels for the oncoming movement of cold and warm air.
After this, a housing made of metal, chipboard or plastic is made to fit the dimensions of the heat exchanger. There are four holes in it for air supply. Two of them have fans. The heat exchanger is rotated at an angle of 45 degrees and secured in the housing.
The work is completed by thoroughly sealing all installation joints with silicone.
The issue of the quality of inhaled air has been and remains the most important for human life. Various parameters play a role. Temperature, cleanliness and freshness take first place among them. Light ventilation using a window is often not enough. Too cold incoming air brings some discomfort. The appearance of a stuffy summer lazy breeze will also not bring pleasure.
What is it and what is the principle of operation
Ventilation-type heat exchange structures (recuperators) help change the situation. The name of the device comes from the English and Latin words meaning "return».
The principle of operation fully corresponds to the etymological meaning. Air in the room sucked in by the ventilation system and is forcibly thrown out into the street. At the same time, an external stream of freshness is sent into the room. Inside heat exchange occurs, thanks to which air masses return to the room at the required temperature.
An important indicator of ventilation systems is the percentage of mixing of incoming and exhaust air. The operation of recuperators makes it possible to reduce this position to almost zero. This is achieved by the presence of a plastic, copper, aluminum or zinc separator. Heat exchange occurs due to the transfer of flow energy to the boundary. The jets themselves pass either parallel or crosswise.
Specially designed gratings at the inlet of the flow from the street allow you to retain dust, pollen, insects, and reduce the number of incoming bacteria. The air is purified and enters the room. At the same time, waste particles containing many harmful components. In addition to the circulation of air flows, the supply jets are cleaned and insulated.
Most existing recuperators have gentle sound modes, which promote strong healthy sleep when installed in a nursery or bedroom.
Many designs in recent years are compact and easy to install, have a remote control, and have additional capabilities.
Temperature standards in an apartment are studied in detail in this article:
Types of recuperators
Depending on various parameters, consider:
- Plate recuperators
- Rotary recuperators
- Chamber recuperators
- Recuperators with an additional built-in heat exchanger
- Composition of multiple heat pipes
Plate recuperators.
The heat exchanger inside consists of one or more fixed plates made of copper, aluminum, plastic or especially strong, specially treated cellulose. The air passes through a series of cassettes. Due to the temperature difference between the incoming and outgoing flows, slight condensation may occur. Possible in cold weather some frost formation. As a rule, to combat it, the device is equipped with additional elements whose functions are to remove the accumulation of condensation and increase the heat supply to defrost the system.
If recuperators are equipped with one air movement cassette, then when droplets form, the flow is redirected to bypass it, and the accumulated moisture is removed through a special drainage device. If the system involves several elements, then condensation formation is reduced to zero.
When ice appears, a special valve blocks the movement of incoming air, due to the heat on the plates, the internal components of the device are heated. Another way to solve the problem was creation of cellulose cassettes. However, their use in rooms with a high degree of humidity increases the creation of condensation and makes the devices unusable.
Plate recuperators are designed in such a way that mixing of incoming and outgoing streams is not possible, and the filtration system additionally removes dust, pollen and bacteria. This makes it possible to use it in bedrooms, children's rooms, and hospitals. Creating ribbed plates allows increase design efficiency, makes it more reliable and durable. Due to their compactness and low cost, such designs are more applicable both in hospitals, catering establishments, and at home.
Many craftsmen have learned to create designs on their own from some set of copper or galvanized plates using a special sealant and material for additional gasket between the sheets.
Рhttp://site/eko/rekuperator-vozduha-svoimi-rukami.htmlmotor recuperators.
Its features are the rotating blades of one or two rotors, due to which air moves. Most often, such devices have cylindrical shape with tightly installed plates inside and a drum, the rotation of which creates flows. First, an air stream leaving the room is passed through, then the direction of rotation changes and street air enters.
The efficiency of rotary recuperators is higher than plate ones, but the devices themselves are more bulky. Their use is more suitable for industrial premises, trading floors. Since the probability of mixing air flows usually reaches 5-7 percent, the installation of rotary heat exchangers becomes impossible for hospitals, canteens, cafes and restaurants. More expensive equipment, bulkiness and complexity of installation made the use of such structures possible only in special industrial zones.
Chamber recuperators. Air from the room enters a special chamber, in which heat is transferred to the walls of its part, and then discharged to the street. Next, the outside air is sucked inside into another compartment, additionally warming up from the boundaries, and enters the room.
Recuperators with an additional built-in heat exchanger. It enhances the heat transfer edge. However, it is less efficient because it reduces efficiency and increases condensation.
Composition of several heat pipes. The air from the room is additionally heated, turning into steam, and then reverse condensation occurs. The advantages of such recuperators are complete antibacterial protection of the air in the structure.
When choosing a device, take into account the size of the room and the degree of its humidity, its purpose, the need for quiet operation, efficiency and the cost of the structure and its installation.
You can read more about comfortable humidity in an apartment in this article:
Application of recuperators (video)
- In rooms to create additional climatic comfort.
- To save energy resources.
- In hospitals to increase the antibacterial zone, to create a comfortable environment, to maintain the thermal characteristics of the room.
- In industrial premises, to ventilate large spaces while maintaining a constant temperature zone, rotary heat exchangers are more often used, which can withstand temperatures up to 650 degrees.
- In automotive structures.
Recovery(from Latin recuperatio - “return receipt”) - the return of part of the materials or energy for reuse in the same technological process.
Recovery during processing of raw materials is called desorption. Desorption, like other mass transfer processes, is usually reversible, and the primary process is called adsorption. These processes are widely used in the chemical industry for purification and drying of gases, purification and clarification of solutions, separation of mixtures of gases or vapors, in particular when extracting volatile solvents from a mixture of gases (recovery of volatile solvents). Recovery of liquid solvents is used in the production of hydrocarbons, alcohols, ethers and esters, etc. Adsorption and desorption processes are carried out in specialized adsorption units.
Recovery– the process of partial energy recovery for reuse. In this topic we are talking about air recovery in ventilation systems.
The principle of operation of the recuperator
We have supply and exhaust ventilation. In winter, the supply air is cleaned by air filters and heated by air heaters. It enters the room, warms it and dilutes harmful gases, dust and other emissions. Then it enters the exhaust ventilation and is thrown out into the street... Hence the thought... Why don't we heat the cold supply air with the exhaust air. After all, we are essentially throwing money away. So, we have exhaust air with a temperature of 21 C and supply air, which before the heater has a temperature of -10 C. We install, for example, a recuperator with a plate heat exchanger. To understand the principle of operation of a recuperator with a plate heat exchanger, imagine a square in which the exhaust air passes from bottom to top, and the supply air from left to right. Moreover, these flows do not mix with each other due to the use of special heat-conducting plates that separate these two flows.
As a result, the exhaust air gives up to 70% of the heat to the supply air and at the outlet of the recuperator has a temperature of 2-6 C, and the supply air, in turn, has a temperature at the outlet of the recuperator of 12-16 C. Consequently, the heater will not heat the air -10 C , and +12 C and this will allow us to significantly save on electrical or thermal energy spent on heating the supply air.
Types of recuperators
Although a recuperator with a plate heat exchanger is most common in the Russian Federation, there are other types of recuperators, which in some cases are more efficient or, in general, only they can cope with the tasks. We invite you to consider the four most popular types of recuperators:
Recuperator with plate heat exchanger (Plate recuperator)
Recuperator with rotary heat exchanger (Rotary recuperator)
Water recirculation heat exchanger
Roof recuperator
Plate recuperator
The most common type is a plate or cross-flow air recuperator for apartments.
It is a small cassette. Two channels are created in it, which are separated from each other by sheets of steel. They carry separate supply and exhaust air flows. Steel acts as a heat “filter”. That is, a temperature exchange occurs, but air mixing is not allowed. The prevalence of this type of device is due to its simplicity, compactness and low cost. The plate air recuperator for apartments has some disadvantages, but they are not so significant when installed in small residential premises.
Advantages: - the device is easily built into any part of the air duct; - there are no moving parts (easier maintenance, no risk of air flow displacement, etc.); - relatively high efficiency – 50...90%; - can work with high-temperature gas and air mixtures (up to +200°C); - aerodynamic resistance to passing air flows increases slightly; - simple performance adjustment via a bypass valve.
Plate recuperators are designed in such a way that the air flows in them do not mix, but contact each other through the walls of the heat exchange cassette. This cassette consists of many plates that separate cold air flows from warm ones. Most often, the plates are made of aluminum foil, which has excellent thermal conductivity properties. The plates can also be made of special plastic. These are more expensive than aluminum ones, but increase the efficiency of the equipment. 
Plate heat exchangers have a significant drawback: as a result of the temperature difference, condensation forms on cold surfaces, which turns into ice. An ice-covered recuperator stops working effectively. To defrost it, the incoming flow is automatically bypassed by the heat exchanger and heated by a heater. Meanwhile, the escaping warm air melts the ice on the plates. In this mode, of course, there is no energy saving, and the defrosting period can take from 5 to 25 minutes per hour. To heat the incoming air during the defrosting phase, air heaters with a power of 1-5 kW are used.
Some plate heat exchangers use preheating of the incoming air to a temperature that prevents the formation of ice. This reduces the efficiency of the recuperator by approximately 20%.
Another solution to the icing problem is hygroscopic cellulose cassettes. This material absorbs moisture from the exhaust air flow and transfers it to the incoming air, thereby returning moisture back. Such recuperators are justified only in buildings where there is no problem of air humidification. The undoubted advantage of hygrocellulose recuperators is that they do not require electrical heating of the air, which means they are more economical. Recuperators with double plate heat exchangers have an efficiency of up to 90%. Ice does not form in them due to heat transfer through the intermediate zone.
Well-known manufacturers of plate heat exchangers: SCHRAG (Germany), MITSUBISHI (Japan), ELECTROLUX, SYSTEMAIR (Sweden), SHUFT (Denmark), REMAK, 2W (Czech Republic), MIDEA (China).