What is the recovery process. Air recuperator: what is it and how does it work. The principle of operation of the recuperator
Ecology of consumption. Manor: Heat loss is a serious problem that building science is struggling with. Effective insulation, sealed windows and doors solve it only partially. Heat leakage through walls, windows, roofs and floors can be significantly reduced. Despite this, the energy has one more wide way to "escape". This is ventilation, without which it is impossible to do in any building.
Heat loss is a serious problem that building science is struggling with. Effective insulation, sealed windows and doors solve it only partially. Heat leakage through walls, windows, roofs and floors can be significantly reduced. Despite this, the energy has one more wide way to "escape". This is ventilation, without which it is impossible to do in any building.
It turns out that in winter we spend precious fuel on heating the premises and at the same time continuously throw heat out into the street, letting in cold air.
The problem of energy saving can be solved with the help of a heat recuperator. In this device, warm room air heats the outdoor air. This achieves considerable savings in heating costs (up to 25% of the total cost).
In the summer, when it is hot outside, and the air conditioner is working in the house, the recuperator also benefits. It cools the hot inlet stream, reducing air conditioning costs.
Let's take a closer look at household recuperation units in order to have an idea about their design, advantages and features of choice.
Types, principle of operation and device of recuperators
The idea to use the heat of room air to heat the outside 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 simple in design are plate heat exchangers. 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 which parallel plates are installed. The air leaving the room and entering it is cut by them into narrow streams, each of which goes through its own channel. Heat transfer occurs through the plates. Outdoor air is heated, while indoor air cools and is released into the atmosphere.
The principle of operation of a plate heat exchanger
The main disadvantage of lamellar installations is freezing in severe frosts. The condensate that settles in the recovery unit turns into ice and drastically reduces the performance of the device. Three methods have been found to combat this phenomenon.
The first is to install a bypass valve. Having received a signal from the sensor, it starts up a cold stream bypassing the block. Only warm air passes through the plates, defrosting the frost. After defrosting and removal of condensate, the valve restores the normal operation of the system.
The second option is to use hygroscopic cellulose plates. 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: the elimination of condensate and humidification.
The third way is to preheat the cold stream to a temperature that prevents water from freezing. To do this, a heating element is placed in the supply ventilation duct. The need for it arises when the outdoor air temperature is below -10C.
In recent years, plate reversing units have appeared on the market. Unlike direct-flow devices, they operate in two cycles: the first is the release of warm air to the street, the second is the suction of cold air through the heated block.
The principle of operation of the 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 principle of operation of the rotary unit is the rotation of the 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. Moisture in this case does not freeze, but saturates the supply air.
It should be noted that the supply and exhaust unit with a rotary heat exchanger allows you to smoothly adjust the heat transfer. It is done by changing the speed of rotation of the cassette. The main disadvantage of rotary systems is the high cost of maintenance. In terms of reliability, they are also inferior to lamellar ones.
The next view is a recirculating water plant. It is the most complex in design. The heat transfer here is not carried out through the plates or the rotor, but with the help of antifreeze or water.
The first liquid-air heat exchanger is placed on the exhaust duct, and the second on the suction duct. The work goes on the principle of a heater: room air heats water, and it heats the street.
The efficiency of such a system does not exceed the performance of plate heat exchangers (50-65%). The high price that has to be paid for the complexity of the design is justified by the only advantage: the blocks of such an installation can be placed not in one building, but in areas of supply and exhaust ventilation that are remote from each other. For powerful industrial systems, this is of great importance. In small buildings, such devices are not installed.
Features of choosing a recuperator
Having got acquainted with the peculiarities of the work of recuperative 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. In the working position, domestic supply and exhaust ventilation with heat recovery can be installed in several ways:
- Inside the wall. The housing is mounted in a pre-drilled hole. A cap is placed on the outside, a grill and a control unit on the inside.
- Indoors. The unit 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 channel device of the device allows you to place it on balconies and loggias, as well as just on the facade of the building.
Another parameter to consider when buying is the number of fans. Budget air recuperators for the home are equipped with one ventilation unit that works both for supply and exhaust.
More expensive devices have 2 fans. One of them pumps in, and the other throws out air. The performance of such devices is higher than single-fan.
When buying, you should also pay attention to the presence of an electric heater. With its help, freezing of the cassette is excluded and the lower temperature limit of the device operation is increased.
Climate control function. Allows you to precisely set the temperature to which the heat exchanger will heat the air.
Possibility of regulation of humidity. This parameter significantly affects the comfort of the microclimate. A standard heat exchanger dries the air by removing moisture from it.
The presence or absence of a filter. An additional option that positively affects 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 can differ significantly. The widest operating temperature range from -40 to +50C is rare for household appliances.
Therefore, in addition to taking into account the optimal performance in m3 / h, when buying, choose a device that can fully work in your climatic conditions.
Performance calculation
Detailed calculations of the operation of recuperators in the supply and exhaust ventilation system are quite complex. Here you 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 silencers, etc. Only experienced engineers can competently perform such a task.
An ordinary consumer can use a simplified methodology in order to correctly navigate when buying a device.
The performance of the heat exchanger directly depends on the sanitary norm of air consumption per 1 person. Its average value is 30 m3/hour. Therefore, if 4 people permanently live in an apartment or a private house, then the productivity of the installation should be at least 4x30 = 120 m3 / h.
Own electric 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 capacity of 0.8 to 2.0 kW are installed.
Popular brands and estimated prices
When choosing a household heat exchanger, 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).
Heat exchanger for small rooms Mitsubishi Electric VL-100EU5-E. Air consumption 105 m3/h. Price from 21,000 rubles.
A 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 rubles.
The equipment of Russian and Ukrainian companies Vents (Vents), Vakio (Vakio), Prana and Zilant has proven itself well. Not inferior to foreign counterparts in performance and reliability, they often turn out to be more affordable.
Installing Vakio. Capacity 60 m3/h in recuperation mode, up to 120 m3/h in supply ventilation mode. Price from 17,000 rubles.
The estimated cost of air recovery systems of these companies (capacity from 120 to 250 m3/hour) is from 17,000 to 55,000 rubles.
Prava 200g. Inflow - 135 m3/h, extract - 125 m3/h. The recommended area for system maintenance 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 excessive humidity, which caused the appearance of mold and fungus in the premises, was solved.
In the calculations of the payback period for this equipment, figures from 3 to 7 years are given. We did not find data on instrumental measurements of real energy savings on forums dedicated to this topic.
Briefly about self-assembly
In most photo and video instructions for the independent manufacture of recuperators, plate models are considered. This is the easiest and most affordable option for a home master.
The main part of the design is the heat exchanger. It is made of galvanized steel, cut into plates 30x30 cm in size. 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 laying and alternately turning the plates at an angle of 90 degrees relative to each other. So get isolated channels for the oncoming movement of cold and warm air.
After that, a housing made of metal, chipboard or plastic is made to fit the dimensions of the heat exchanger. It has four holes for air supply. Fans are installed in two of them. The heat exchanger is turned at an angle of 45 degrees and fixed in the housing.
Thorough sealing of all assembly joints with silicone completes the work.
Any enclosed space needs daily ventilation, but sometimes this is not enough to create a comfortable and pleasant microclimate. In the cold season, when the windows are open in the ventilation mode, heat quickly leaves, and this leads to unnecessary heating costs. In the summer, many people use air conditioners, but along with the cooled air, hot air from the street also penetrates.
To balance the temperature and make the air fresher, a device such as an air recuperator has been invented. In winter, it allows you not to lose room heat, and in summer heat it does not allow hot air to enter the room.
What is a recuperator?
Translated from Latin, the word recuperator means - return receipt or return, with regard to air, it means the return of thermal energy, which is carried away with the air through the ventilation system. Such a device as an air recuperator copes with the task of ventilation, balancing two air flows.
The principle of operation of the device is very simple, due to the temperature difference, heat exchange occurs, due to this, the air temperature equalizes. The heat exchanger has a heat exchanger with two chambers, they pass exhaust and supply air flows through them. The accumulated condensate, which is formed due to the temperature difference, is automatically removed from the heat exchanger.
The recovery system allows not only to ventilate the air in the room, it significantly saves heating costs, as it effectively reduces heat loss. The recuperator is capable save more than 2/3 heat leaving the room, which means that the device reuses thermal energy in one technological cycle.
Device classification
Recuperators differ in the schemes of movement of heat carriers and in design, as well as in their purpose. Are there several types of recuperators?
- lamellar
- Rotary
- Aquatic
- Devices that can be placed on the roof.
Plate heat exchangers
They are considered the most common, because their price is low, but they are quite effective. The heat exchanger located inside the device consists of one or more copper or aluminum plates, plastic, very durable cellulose, they are in a stationary state. Air entering the device passes through a series of cassettes and does not mix; during operation, a simultaneous cooling and heating process takes place.
The device is very compact and reliable, it practically does not fail. Plate-type recuperators operate without power consumption, which is an important advantage. Among the disadvantages of the device - in frosty weather, the lamellar model cannot work, moisture exchange is impossible due to freezing of the exhaust device. Its exhaust channels collect condensate, which freezes at sub-zero temperatures.
Rotary heat exchangers
Such a device is powered by electricity, its blades from one or two rotors must rotate during operation followed by air movement. Usually they have a cylindrical shape with plates tightly installed and a drum inside. They are forced to rotate by air flows, first the room air comes out, and then, changing direction, the air comes back from the street.
It should be noted that rotary devices are larger, but They are much more efficient than the plate ones. They are great for large rooms - halls, shopping centers, hospitals, restaurants, so it is not practical to buy them for the home. Among the disadvantages, it is worth noting the expensive maintenance of such devices, since they consume a lot of electricity, they are not easy to install due to bulkiness, and they are expensive. For installation, a ventilation chamber is required due to the large size of the rotary heat exchanger.
Heat exchanger water and placed on the roof
Recirculation devices transfer thermal energy to the supply heat exchanger using several heat carriers - water, antifreeze, etc. This device is very similar in performance to plate heat exchangers, but differs in that it is very similar to a water heating system. The disadvantage is low efficiency and frequent maintenance.
The heat exchanger, which can be placed on the roof, saves space in the room. Its efficiency is a maximum of 68%, it does not need operating costs, all these qualities can be attributed to the advantages of this type. The downside is that such a heat exchanger is difficult to mount, it requires a special mounting system. Most often, this type is used for industrial facilities.
Natural ventilation must be designed and installed in any residential building, but it is always influenced by weather conditions, depending on the time of year, the strength of ventilation depends on this. If in winter the ventilation system works efficiently in frost, then in summer it practically does not function.
The tightness of a residential building can be reduced by improving natural ventilation, but it will give a tangible result only in the cold season. There is also a negative side, for example, heat will leave a residential building, and the incoming cold air will require additional heating.
In order for such a ventilation process not to be too costly for the owners of the house, it is necessary to use the heat of the air removed from the room. It is necessary to make forced air circulation. To do this, a network of supply and exhaust air ducts is laid out, then fans are installed. Air will be supplied through them to separate rooms and such a process will not be associated with weather conditions. Especially for this, a heat exchanger is installed at the intersection of fresh and polluted air masses.
What does an air recuperator provide?
The recuperation system allows to minimize the percentage of mixing of incoming and exhaust air. The separators that are in the device carry out this process. Due to the transfer of flow energy to the boundary, heat exchange occurs, the jets will pass in parallel or cross. The recovery system has many positive features.
- A special type of grille at the air inlet keeps dust, insects, pollen and even bacteria from the outside.
- Purified air enters the room.
- Polluted air leaves the room, which may contain harmful components.
- In addition to circulation, the supply jets are cleaned and warmed.
- Promotes better and healthier sleep.
The positive properties of the system make it possible to use it in various types of rooms to create more comfortable temperature conditions. Very often they are used in industrial premises where ventilation of a large space is necessary. In such places it is necessary to maintain a constant air temperature, this task is handled by rotary heat exchangers that can work at temperatures up to +650 ° C.
Conclusion
The necessary balance of fresh and clean air with normal humidity can be provided by the supply and exhaust ventilation system. By installing a recuperator, you can solve many problems associated with saving energy resources.
When choosing an air recuperator for your home, you must take into account the area of \u200b\u200bthe living space, the degree of humidity in it and the purpose of the device. You should definitely pay attention to the cost of the device and the possibility of installation, its efficiency, on which the quality of ventilation of the whole house will depend.
Everyone knows that there is a huge variety of systems for ventilation of the room. The simplest of them are open-type systems (natural), for example, using a window or a window.
But this method of ventilation is absolutely not economical. In addition, for effective ventilation, you need to have a constantly open window or the presence of a draft. Therefore, this type of ventilation will be extremely inefficient. Supply ventilation with heat recovery is increasingly used for ventilation of residential premises.
In simple words, recovery is identical to the word "preservation". Heat recovery is the process of storing thermal energy. This is due to the fact that the flow of air that leaves the room cools or heats the air entering inside. Schematically, the recovery process can be represented as follows:
The ventilation with heat recovery takes place according to the principle that the flows must be separated by the design features of the heat exchanger in order to avoid mixing. However, for example, rotary heat exchangers do not make it possible to completely isolate the supply air from the exhaust air.
The percentage of efficiency of the heat exchanger can vary from 30 to 90%. For special installations, this figure can be 96% energy savings.
What is an air recuperator
By its design, an air-to-air heat exchanger is a unit for heat recovery of the output air mass, which allows the most rational use of heat or cold.
Why choose heat recovery ventilation
Ventilation, which is based on heat recovery, has a very high efficiency. This indicator is calculated by the ratio of the heat that the heat exchanger actually produces to the maximum amount of heat that can only be stored.
What are the types of air recuperators
To date, ventilation with heat recovery can be carried out by five types of recuperators:
- Lamellar, which has a metal structure and has a high level of moisture permeability;
- Rotary;
- chamber type;
- Recuperator with an intermediate heat carrier;
- Heat pipes.
Ventilation of a house with heat recovery using the first type of heat exchangers allows incoming air flows from all sides to flow around a lot of metal plates with increased thermal conductivity. The efficiency of recuperators of this type ranges from 50 to 75%.
Features of the device of plate heat exchangers
- Air masses do not contact;
- All details are fixed;
- No moving structural elements;
- Does not form condensate;
- Cannot be used as a room dehumidifier.
Features of rotary heat exchangers
The rotary type of recuperators has design features, with the help of which heat transfer occurs between the supply and output channels of the rotor.
Rotary heat exchangers are covered with foil.
- Efficiency up to 85%;
- Saves electricity;
- Let's apply to dehumidification of the room;
- Mixing up to 3% of air from different streams, in connection with which odors can be transmitted;
- Complex mechanical design.
Supply and exhaust ventilation with heat recovery, which is based on chamber heat exchangers, is used extremely rarely, as it has many disadvantages:
- Efficiency up to 80%;
- Mixing of oncoming flows, in connection with which the transmission of odors increases;
- moving parts of the structure.
Recuperators based on an intermediate heat carrier have a water-glycol solution in their design. Sometimes ordinary water can act as such a coolant.
Features of recuperators with an intermediate heat carrier
- Extremely low efficiency up to 55%;
- Mixing of air streams is completely excluded;
- Scope of application - large-scale production.
Heat recovery ventilation based on heat pipes often consists of an extensive system of tubes that contain freon. Liquid evaporates when heated. In the opposite part of the heat exchanger, freon cools down, as a result of which condensate often forms.
Features of recuperators with heat pipes
- No moving parts;
- The possibility of air pollution by odors is completely excluded;
- The average efficiency index is from 50 to 70%.
To date, compact units for the recovery of air masses are being produced. One of the main advantages of mobile heat exchangers is the absence of the need for air ducts.
Main objectives of heat recovery
- Ventilation based on heat recovery is used to maintain the required level of humidity and temperature indoors.
- For skin health. Surprisingly, heat recovery systems have a positive effect on human skin, which is constantly moisturized and the risk of drying out is minimized.
- To avoid drying out furniture and creaking floors.
- To increase the likelihood of static electricity. Not everyone knows these criteria, but with increased static voltage, mold and fungi develop much more slowly.
Properly selected supply and exhaust ventilation with heat recovery for your home will allow you to significantly save on heating in the winter and air conditioning in the summer. In addition, this type of ventilation has a beneficial effect on the human body, which will make you less sick, and the risk of fungus in the house will be minimized.
In the process of ventilation from the room, not only the exhaust air is utilized, but also part of the thermal energy. In winter, this leads to an increase in energy bills.
To reduce unjustified costs, not to the detriment of air exchange, will allow heat recovery in ventilation systems of centralized and local type. For the regeneration of thermal energy, different types of heat exchangers are used - recuperators.
The article describes in detail the models of units, their design features, principles of operation, advantages and disadvantages. The above information will help in choosing the best option for arranging the ventilation system.
Translated from Latin, recuperation means reimbursement or return receipt. With regard to heat exchange reactions, recovery is characterized as a partial return of energy expended on a technological action for the purpose of using it in the same process.
The local recuperators are provided with a fan and a plate heat exchanger. The "sleeve" of the inlet is insulated with noise-absorbing material. The control unit for compact air handling units is placed on the inner wall
Features of decentralized ventilation systems with recuperation:
- efficiency – 60-96%;
- low performance- devices are designed to provide air exchange in rooms up to 20-35 sq.m;
- affordable price and a wide range of units, ranging from conventional wall valves to automated models with a multi-stage filtration system and the ability to adjust humidity;
- ease of installation- for commissioning, no ductwork is required, you can do it yourself.
Important criteria for choosing a wall air inlet: allowable wall thickness, capacity, heat exchanger efficiency, air channel diameter and temperature of the pumped medium
Conclusions and useful video on the topic
Comparison of the operation of natural ventilation and a forced system with recuperation:
The principle of operation of a centralized heat exchanger, calculation of efficiency:
The device and operation of a decentralized heat exchanger using the Prana wall valve as an example:
About 25-35% of the heat leaves the room through the ventilation system. To reduce losses and efficient heat recovery, recuperators are used. Climatic equipment allows you to use the energy of the waste masses to heat the incoming air.
Do you have something to add, or do you have questions about the operation of various ventilation recuperators? Please leave comments on the publication, share your experience in operating such installations. The contact form is in the bottom block.
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 is a necessity. Ventilation is based on the principle of recuperation. This is the name of the process in which part of the heat is returned from the exhaust air. Leaving the room, warm air partially heats the oncoming cold flow in the heat exchanger. Thus, completely “exhaust” air goes out into the street, and not only fresh, but also already heated air enters the room.
Why it is 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, continuous penetration of air into the room should occur through the frames, doorways and cracks, 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, the owner of the housing spends huge amounts of money, because. cold weather in our country lasts 5-6 months. And although the heating season is shorter, it still takes huge resources to heat the supply air. However, the disadvantages of natural exhaust ventilation do not end there. From the street, not only cold, but also dirty air enters the room, as well as drafts 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 into the chimney in a couple of minutes. Since energy prices are rising year by year, it is not surprising that the question of reducing heating costs sooner or later arises for every thrifty person who does not want to “heat the street” at his own expense.
How to keep warm in the house
To save heat in the ventilation system, - heating the supply cold air due to the warm air removed from the room, special recuperator units are designed. A cassette is built into the supply and exhaust ventilation units, which provides air heat exchange. Exiting through it, the exhaust air transfers heat to the walls of the heat exchanger, while the cold air going into the room is heated from the walls. This principle is the basis for the operation of plate and rotary heat exchangers, which have gained popularity in the market of ventilation units.
Are there any disadvantages of plate heat exchangers
In devices of this type, air flows are, as it were, cut by plates. These supply and exhaust systems, in addition to the many advantages that will be discussed later, have one drawback: on the side where the exhaust air comes out, frost 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, condensate forms, which, in fact, turns into frost. Air begins to pass through the frozen plates with great resistance, and the 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. Glass in a moment would be covered first with a white film, and then with drops of water. Is it possible to deal with the problem of freezing of the heat exchanger? Experts found a way out by installing a special bypass valve in ventilation systems with recuperation. As soon as the plates are covered with a layer of ice, the bypass opens, and the supply air for some time bypasses the heat exchanger cassette, entering the room with little or no heating. At the same time, the heat exchanger plates are quickly defrosted due to the removed exhaust air, and the resulting water is collected in a drainage bath. The bath is connected to a drainage system leading to the sewer, and all condensate is drained there. The heat exchanger starts working efficiently again, and air exchange is restored.
When the cassette is defrosted, the valve closes again, however, there is one “but” here. When air does not enter the heat exchanger, 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 heater - exactly the same as that found in simple supply units, but of much lower power. How to deal with it? Is it possible to deal with frost so as not to lose money?
Air handling units with heat recovery
Manufacturers of recuperators have found a solution to this serious problem. Thanks to the invention of a new technology, the moisture that settles on the walls of the heat exchanger from the side of the outgoing air begins to be absorbed into them and passes to the side of the supply air - moistening it. Thus, almost all the moisture in the exhaust air gets back into the room. What makes this process possible? Engineers achieved this effect by creating cassettes from hygroscopic cellulose. In addition, many hygroscopic celluloses do not have bypasses and do not connect to a drainage system with a bathtub and plumbing. All moisture is utilized by air currents, and it remains almost completely in the room. So, using a cellulose heat exchanger in the heat exchanger, it is no longer necessary to use a bypass and direct air around the heat exchanger plates.
As a result, the efficiency of the heat exchanger was raised to 90%! And this means that the supply air from the street will be heated by 90% due to the outgoing air. At the same time, recuperators can work without problems even in frost, up to -30 degrees Celsius. Such installations are great for residential premises, apartments, country houses and cottages, maintaining and maintaining the necessary humidity and air exchange in winter and summer, they create and maintain the necessary microclimate in the room 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, frost protection must be installed. Also, with all its positive qualities, heat exchangers 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.
Scheme and principle of operation of the supply and exhaust ventilation system with a heat exchanger
Suppose that it is winter outside and the air temperature outside the window is -23 0 C. When the air handling unit is turned on, the outdoor air is sucked in by the unit using the built-in fan, passes through the filter and enters the heat exchange cassette. Passing through it, it heats up to +14 0 C. As we can see, in winter cold, the unit is not able to completely warm the air to room temperature, although for many, such heating may be enough, so after the heat exchanger, the supply air can go immediately to the room, or if there is a so-called “air heating” in the heat exchanger, passing through it, the air is heated up to +20 0 C and only fully warmed up enters the room. A preheater 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 heater. On the contrary, room air with a temperature of +18 0 C (+20 0 C) is sucked in from the room by the fan built into the unit, passing through the heat exchange cassette, cooled by the supply air and exits the heat exchanger outside, having a temperature of -15 0 C.
What air temperature will be after the heat exchanger in winter and summer
There is a fairly simple way to calculate for yourself what temperature the air will enter the room after the heat exchanger. How efficient will the supply air be heated and will it be heated at all? What will happen to the air in the heat exchanger in summer?
Winter
The picture shows that the outdoor air is 0 0 С, the efficiency of the heat exchanger is 77%, while the temperature of the air entering the room is 15.4 0 С. There is a formula for calculating the supply air for a heat exchanger, depending on its efficiency, outdoor and indoor air temperature:
t (after heat exchanger)=(t (indoors)-t (outdoors))xK (heat exchanger efficiency)+t (outdoors)
For our example, it turns out: 15.4 0 C \u003d (20 0 C-0 0 C) x77% + 0 0 C If the temperature outside the window is -20 0 C, in the room +20 0 C, the efficiency of the heat exchanger is 77%, then the air temperature after the heat exchanger 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
Similarly, the air temperature after the heat exchanger is calculated in summer:
t (after heat exchanger)=t (outdoors)+(t (indoors)-t (outdoors))xK (heat exchanger efficiency)
For our example, it turns out: 24.2 0 С \u003d 35 0 С + (21 0 С-35 0 С) x77%
Scheme and principle of operation of the supply and exhaust ventilation system with a rotary heat exchanger
The principle of operation of a rotary heat exchanger 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 such a process to be carried out with different intensity.
Which recuperator is better
Today, recuperators from different manufacturers are on sale, differing in many points: the principle of operation, efficiency, reliability, economy, etc. Let's take a look at the most popular types of recuperators and compare their advantages and disadvantages.
1. Plate heat exchanger with aluminum heat exchanger.
The price of such a heat exchanger is quite low compared to other types of heat exchangers, which is undoubtedly one of its advantages. In the device, air flows do not mix, they are separated by aluminum foil. Of the minuses, one should name not high performance at low temperatures, tk. the heat exchanger periodically freezes up and must be thawed frequently. Logically, electricity costs are rising. It is also not advisable to install them in residential premises, because in winter, during the operation of the heat exchanger, all moisture is removed from the air of the room and its constant humidification is required. The main advantage of aluminum plate heat exchangers is that they can be installed to ventilate swimming pools.
2. Plate heat exchanger with plastic heat exchanger. The advantages are the same as the previous version, but the efficiency is higher due to the properties of the plastic. 
3. Plate heat exchanger with cellulose heat exchanger and single cassette. Despite the fact that air flows are separated by paper partitions, moisture calmly permeates the walls of the heat exchanger. An important advantage is that the saved heat and moisture also gets back into the room. Due to the fact that the heat exchanger is practically not subject to freezing, no time is spent on thawing it, the efficiency of the device is significantly increased. If we talk about the shortcomings, they are as follows: recuperators of this type cannot be installed in swimming pools, as well as in any other premises where excessive humidity is observed. In addition, the heat exchanger cannot be used for dehumidification. Very often, such.
4. Rotary heat exchanger. It has a high efficiency, but this figure is still lower than if a double cassette plate installation was used. A distinctive feature is the low energy consumption. As for the shortcomings, we note such moments, since the oncoming air flows at 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. Finally, the rotary heat exchanger must be serviced more often than other air handling units and its installation in damp rooms is not desirable.
Recuperators for apartments and country houses
| Mitsubishi Lossney | Electrolux EPVS |
Daikin |
Sistemair | SHUFT |
What determines the price of the recuperator
First of all, the price of a heat exchanger depends on the performance of the entire ventilation system. A professional designer will be able to develop a competent project that meets exactly your conditions and requests, 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 choose the equipment yourself, including air ducts and grilles, but it is desirable that a specialist deal with the identified issues. The development of the project costs extra money, and at first glance, such expenses will seem quite substantial to someone, but if you calculate how much money will remain in your budget as a result thanks to a competent one, then 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 declared amount? Or will you just overpay for a new product or brand? The equipment is not cheap and pays off for several years, 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. Usually the guarantee is given not for the heat exchanger, but for its components. The better the quality of components, assemblies and other components, the more expensive the purchase will cost. The reliability of the system is evaluated by the strengths and weaknesses of the product. No one offers a natural, ideal option, but it is quite possible to find the best solution for a particular room.
How to choose a supply and exhaust unit with a heat exchanger
First, ask the seller the following questions:
1. What company produces products? What is known about her? How many years on the market? What are the reviews?
2. What is the performance of the system? These data can be calculated by specialists to whom you turn for advice, including specialists from our company. To do this, you must specify the exact parameters of the premises, it is advisable to provide the layout of the apartment, office, country house, cottage, etc.
3. What will be the resistance of the duct system to airflow after installing a particular model? This 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 heat exchanger is selected taking into account the so-called "working point" - the ratio of air flow and air duct resistance.
4. Which energy class does the heat exchanger belong to? How much will the system cost? How much electricity can be saved? You need to know this in order to calculate the cost of the heating season.
5. What is the declared Efficiency of the installation and the real one? The efficiency of recuperators depends on the temperature difference between the room and outside. Also, this indicator is influenced by such parameters as: type of heat exchange cassette, air humidity, layout of the system as a whole, correct placement of all nodes, etc.
Let's see how the efficiency can be calculated for different types of recuperators.
- If the heat exchanger of a plate heat exchanger is made of paper, then the efficiency will be, on average, 60-70%. The installation does not freeze, more precisely - this happens extremely rarely. If the heat exchanger needs to be defrosted, then the system itself reduces the performance of the installation for some time.
- 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 frosting, you will have to use much more electricity.
- The rotary heat exchanger shows high efficiency in the event that the rotor speed is regulated by "automatic", guided by the temperature sensors, which are installed both indoors and outdoors. Rotary heat exchangers are also subject to freezing, as a result of which the efficiency decreases in the same way as for plate heat exchangers made of aluminum.
