Air handling unit with heat recovery. Types and principle of operation of ventilation with recuperation. Recuperators with intermediate heat carrier

A comfortable indoor climate cannot be organized without a good ventilation system. Plastic windows, doors and finishing materials make the house so airtight that it can lead to a lack of natural ventilation, dampness and condensation. And if you take into account the general air pollution, then you simply cannot do without effective air filters. In such houses, an air recovery system for private houses must be present. This device is driven by a supply and exhaust unit, which contains a heat exchanger. Such a device will not only provide housing with fresh, purified air, but also help reduce heating costs.

Recuperator for a private house. Advantages

The term "recuperator" in translation from lat. means returning. The device itself is a heat exchanger that stores heat in the room and transfers it to the air entering from the street. Recuperation is a ventilation method with minimal heat consumption. Such a device helps to save up to 70% of heat and return it back to the room.

Main advantages:

• Low noise
• No need to open windows
• Possibility of installation in a false ceiling structure
• Savings on heating and air conditioning costs
• Convenience and additional features

Automatic adjustment of the intensity of air flow makes the use of devices not only safe, but also comfortable.

How to choose a ventilation recuperator?

All modern ventilation units use the same principle of operation - they provide air flow to the house, cleaning it from dust and impurities. Such systems may differ: in dimensions, cleaning class, performance, equipment and the presence of additional functions.

Units with an electric heat exchanger have a built-in rotary heat exchanger with an efficiency of 80% and a remote control. In devices with a water heater, it is possible to control the speed and temperature of the incoming air flow. Such ventilation units are more popular than those with electric heat exchangers.

Given the minimum energy consumption of a heat exchanger for a private house, the price of which is quite affordable, the cost of installing a ventilation system will pay off very quickly. And if we also take into account the undoubted benefits for health and general well-being, then the choice in favor of a PVU with a recuperator becomes obvious.

Supply and exhaust ventilation units with heat recovery appeared relatively recently, but quickly gained popularity and became a fairly popular system. The devices are able to fully ventilate the room during the cold period, while maintaining the optimal temperature regime of the incoming air.

What it is?

When using supply and exhaust ventilation in the autumn-winter period, the question of maintaining heat in the room often arises. The flow of cold air coming from the ventilation rushes to the floor and contributes to the creation of an unfavorable microclimate. The most common way to solve this problem is to install a heater that heats cold outdoor air flows before supplying them to the room. However, this method is quite energy-intensive and does not prevent heat losses in the room.

The best solution to the problem is to equip the ventilation system with a heat exchanger. The heat exchanger is a device in which the outflow and air supply channels are located in close proximity to each other. The heat recovery unit allows you to partially transfer heat from the air leaving the room to the incoming air. Thanks to the technology of heat exchange between multidirectional air flows, it is possible to save up to 90% of electricity, in addition, in the summer, the device can be used to cool the incoming air masses.

Specifications

The heat recuperator consists of a housing, which is covered with heat and noise insulating materials and is made of sheet steel. The case of the device is strong enough and able to withstand weight and vibration loads. There are inflow and outflow openings on the case, and air movement through the device is provided by two fans, usually of axial or centrifugal type. The need for their installation is due to a significant slowdown in the natural circulation of air, which is caused by the high aerodynamic resistance of the heat exchanger. In order to prevent the suction of fallen leaves, small birds or mechanical debris, an air intake grille is installed on the inlet located on the street side. The same hole, but from the side of the room, is also equipped with a grill or diffuser that evenly distributes air flows. When installing branched systems, air ducts are mounted to the holes.

In addition, the inlets of both streams are equipped with fine filters that protect the system from dust and grease drops. This prevents the heat exchanger channels from clogging and significantly extends the life of the equipment. However, the installation of filters is complicated by the need for constant monitoring of their condition, cleaning, and, if necessary, replacing them. Otherwise, the clogged filter will act as a natural barrier to air flow, as a result of which the resistance to it will increase and the fan will break.

According to the type of construction, heat exchanger filters can be dry, wet and electrostatic. The choice of the right model depends on the power of the device, the physical properties and chemical composition of the exhaust air, as well as on the personal preferences of the buyer.

In addition to fans and filters, recuperators include heating elements, which can be water or electric. Each heater is equipped with a temperature switch and is able to automatically turn on if the heat leaving the house cannot cope with the heating of the incoming air. The power of the heaters is selected in strict accordance with the volume of the room and the operating performance of the ventilation system. However, in some devices, the heating elements only protect the heat exchanger from freezing and do not affect the temperature of the incoming air.

Water heater elements are more economical. This is due to the fact that the coolant, which moves along the copper coil, enters it from the heating system of the house. From the coil, the plates are heated, which, in turn, give off heat to the air flow. The water heater regulation system is represented by a three-way valve that opens and closes the water supply, a throttle valve that reduces or increases its speed, and a mixing unit that regulates the temperature. Water heaters are installed in a system of air ducts with a rectangular or square section.

Electric heaters are often installed on air ducts with a circular cross section, and a spiral acts as a heating element. For the correct and efficient operation of the spiral heater, the air flow velocity must be greater than or equal to 2 m/s, the air temperature must be 0-30 degrees, and the humidity of the passing masses must not exceed 80%. All electric heaters are equipped with an operation timer and a thermal relay that turns off the device in case of overheating.

In addition to the standard set of elements, at the request of the consumer, air ionizers and humidifiers are installed in the recuperators, and the most modern samples are equipped with an electronic control unit and a function for programming the operating mode, depending on external and internal conditions. The instrument panels have an aesthetic appearance, allowing the heat exchangers to organically fit into the ventilation system and not disturb the harmony of the room.

Principle of operation

In order to better understand how the recuperative system works, one should refer to the translation of the word “recuperator”. Literally, it means "return of used", in this context - heat exchange. In ventilation systems, the heat exchanger takes heat from the air leaving the room and gives it to the incoming flows. The temperature difference of multidirectional air jets can reach 50 degrees. In the summer, the device works in reverse and cools the air coming from the street to the temperature of the outlet. On average, the efficiency of devices is 65%, which allows for the rational use of energy resources and significant savings on electricity.

In practice, the heat exchange in the heat exchanger is as follows: forced ventilation drives an excess volume of air into the room, as a result of which the polluted masses are forced to leave the room through the exhaust duct. The outgoing warm air passes through the heat exchanger, while heating the walls of the structure. At the same time, a stream of cold air moves towards it, which takes the heat received by the heat exchanger without mixing with the exhaust streams.

However, cooling the exhaust air from the room causes condensation to form. With the good operation of the fans, which give the air masses a high speed, the condensate does not have time to fall on the walls of the device and goes outside along with the air stream. But if the air speed was not high enough, then water begins to accumulate inside the device. For these purposes, a tray is included in the design of the heat exchanger, which is located at a slight inclination towards the drain hole.

Through the drain hole, water enters a closed tank, which is installed from the side of the room. This is dictated by the fact that the accumulated water can freeze the outflow channels and the condensate will have nowhere to drain. The use of collected water for humidifiers is not recommended: the liquid may contain a large number of pathogenic microorganisms, and therefore must be poured into the sewer system.

However, if frost from condensate still forms, it is recommended to install additional equipment - a bypass. This device is made in the form of a bypass channel through which the supply air will enter the room. As a result, the heat exchanger does not heat the incoming flows, but spends its heat exclusively on melting ice. The incoming air, in turn, is heated by a heater, which is switched on synchronously with the bypass. After all the ice is melted and water is discharged into the storage tank, the bypass is turned off and the heat exchanger starts to operate normally.

In addition to installing a bypass, hygroscopic cellulose is used to combat icing. The material is in special cassettes and absorbs moisture before it has time to condensate. Moisture vapor passes through the cellulose layer and returns to the room with the incoming flow. The advantages of such devices are simple installation, the optional installation of a condensate collector and a storage tank. In addition, the efficiency of the cassettes of cellulose recuperators does not depend on external conditions, and the efficiency is more than 80%. The disadvantages include the inability to use in rooms with excessive humidity and the high cost of some models.

Types of recuperators

The modern market of ventilation equipment presents a wide range of recuperators of different types, differing from each other both in design and in the method of heat exchange between streams.

• Plate Models are the simplest and most common type of recuperators, they are characterized by low cost and long service life. The heat exchanger of the models consists of thin aluminum plates, which have high thermal conductivity and significantly increase the efficiency of devices, which in plate models can reach 90%. High efficiency indicators are due to the peculiarity of the structure of the heat exchanger, the plates in which are located in such a way that both flows, alternating, pass between them at an angle of 90 degrees to each other. The sequence of passing warm and cold jets became possible due to the bending of the edges on the plates and the sealing of the joints with polyester resins. In addition to aluminum, alloys of copper and brass, as well as polymeric hydrophobic plastics, are used for the production of plates. However, in addition to advantages, plate heat exchangers also have their weaknesses. The downside of the models is considered to be a high risk of condensation and ice formation, which is due to the plates being too close to each other.

• Rotary models consist of a housing inside which a cylindrical type rotor, consisting of profiled plates, rotates. During the rotation of the rotor, heat is transferred from the outgoing flows to the incoming ones, as a result of which there is a slight mixing of the masses. And although the mixing ratio is not critical and usually does not exceed 7%, such models are not used in children's and medical institutions. The level of air mass recuperation entirely depends on the rotor speed, which is set in manual mode. The efficiency of rotary models is 75-90%, the risk of ice formation is minimal. The latter is due to the fact that most of the moisture is retained in the drum, after which it evaporates. The disadvantages include difficulty in maintenance, high noise load, which is due to the presence of moving mechanisms, as well as the overall dimensions of the device, the inability to install on the wall and the likelihood of the spread of odors and dust during operation.

• chamber models consist of two chambers, between which there is a common damper. After warming up, it begins to turn and run cold air into the warm chamber. Then the heated air goes into the room, the damper closes and the process repeats again. However, the chamber recuperator has not gained wide popularity. This is due to the fact that the damper is not able to ensure complete tightness of the chambers, so the air flows are mixed.

• Tubular models consist of a large number of tubes that contain freon. In the process of heating from the outgoing flows, the gas rises to the upper sections of the tubes and heats the incoming flows. After heat is released, freon takes on a liquid form and flows into the lower sections of the tubes. The advantages of tubular heat exchangers include a fairly high efficiency, reaching 70%, no moving parts, no hum during operation, small size and long service life. The disadvantages are the large weight of the models, which is due to the presence of metal pipes in the design.

• Models with intermediate heat carrier consist of two separate air ducts passing through a heat exchanger filled with a water-glycol solution. As a result of passing through the thermal unit, the exhaust air gives off heat to the coolant, which, in turn, heats the incoming flow. The pluses of the model include its wear resistance, due to the absence of moving parts, and among the minuses they note a low efficiency, reaching only 60%, and a predisposition to the formation of condensate.

How to choose?

Due to the wide variety of recuperators presented to consumers, it will not be difficult to choose the right model. Moreover, each type of device has its own narrow specialization and recommended installation location. So, when buying a device for an apartment or a private house, it is better to choose a classic plate model with aluminum plates. Such devices do not require maintenance, do not require regular maintenance and are distinguished by a long service life.

This model is perfect for use in an apartment building. This is due to the low noise level during its operation and compact size. Tubular standard models have also proven themselves well for private use: they are small in size and do not buzz. However, the cost of such recuperators somewhat exceeds the cost of plate products, so the choice of device depends on the financial capabilities and personal preferences of the owners.

When choosing a model for a production workshop, a non-food warehouse or an underground car park, you should choose rotary devices. Such devices have high power and high performance, which is one of the main criteria for working on large areas. Recuperators with an intermediate coolant have also proven themselves well, however, due to their low efficiency, they are not as in demand as drum units.

An important factor when choosing a device is its price. So, the most budget options for plate heat exchangers can be purchased for 27,000 rubles, while a powerful rotary heat recovery unit with additional fans and a built-in filtration system will cost about 250,000 rubles.

Design and Calculation Examples

In order not to make a mistake with the choice of a heat exchanger, it is necessary to calculate the efficiency and efficiency of the device. To calculate the efficiency, the following formula is used: K = (Tp - Tn) / (Tv - Tn), where Tp denotes the temperature of the incoming flow, Tn is the street temperature, and Tv is the temperature in the room. Next, you need to compare your value with the maximum possible efficiency indicator of the purchased device. Usually this value is indicated in the technical data sheet of the model or other accompanying documentation. However, when comparing the desired efficiency and that indicated in the passport, it should be remembered that in fact this coefficient will be slightly lower than specified in the document.

Knowing the efficiency of a particular model, you can calculate its effectiveness. This can be done using the following formula: E (W) \u003d 0.36xRxKx (Tv - Tn), where P will denote the air flow and is measured in m3 / h. After carrying out all the calculations, it is necessary to compare the costs of purchasing a heat exchanger with its efficiency converted into a monetary equivalent. If the purchase justifies itself, the device can be safely purchased. Otherwise, it is worth considering alternative methods for heating the incoming air or installing a number of simpler devices.

When designing the device yourself, it should be borne in mind that countercurrent devices have the maximum heat transfer efficiency. They are followed by cross-flow ducts, and in the last place are unidirectional ducts. In addition, how intense the heat transfer will be directly depends on the quality of the material, the thickness of the dividing partitions, and also on how long the air masses will be inside the device.

Installation subtleties

Assembly and installation of the recovery unit can be carried out independently. The simplest type of homemade device is a coaxial heat exchanger. For its manufacture, a two-meter plastic sewer pipe with a cross section of 16 cm and an air corrugation made of aluminum 4 m long are taken, the diameter of which should be 100 mm. Adapters-splitters are put on the ends of a large pipe, with the help of which the device will be connected to the air duct, and a corrugation is inserted inside, twisting it in a spiral. The heat exchanger is connected to the ventilation system in such a way that warm air is driven through the corrugation, and cold air goes through a plastic pipe.

As a result of this design, there is no mixing of flows, and the outside air has time to warm up, moving inside the pipe. To improve the performance of the device, you can combine it with a ground heat exchanger. In the process of testing, such a heat exchanger gives good results. So, at an outside temperature of -7 degrees and an internal temperature of 24 degrees, the productivity of the device was about 270 cubic meters per hour, and the temperature of the incoming air corresponded to 19 degrees. The average cost of a homemade model is 5 thousand rubles.

When manufacturing and installing a heat exchanger on your own, it should be remembered that the longer the heat exchanger is, the higher the efficiency of the installation will be. Therefore, experienced craftsmen recommend assembling a heat exchanger from four sections of 2 m each, after preliminary thermal insulation of all pipes. The problem of condensate drainage can be solved by installing a water drain fitting, and the device itself can be placed slightly at an angle.

Price: 25 500 RUB

Units with recuperation and plate heat exchanger, Mitsubishi LOSSNEY are designed for air exchange and maintenance of relative humidity in small rooms for various purposes. Made in Japan.

Price: 62 600 RUB

Series of air handling units with heat recovery, Daikin ( VAM-150F,VAM-250F, VAM-350FB, VAM-500FB, VAM-650FB, VAM-800FB), designed for air exchange, energy saving and maintaining relative humidity in rooms for various purposes. They are suitable for country houses, cottages, apartments and commercial premises. The main distinguishing feature of DAIKIN plants is high efficiency and low power consumption. These ventilation units can work both independently and as part of VRV air conditioning systems, as well as in conjunction with air humidifiers.

Price: 51 500 RUB

A series of air handling units with plate heat exchanger, Mitsubishi LOSSNEY ( LGH-15RX5ELGH-5E, LGH-25RX5ELGH-5E, LGH-35RX5ELGH-5E, LGH-50RX5ELGH-5E, LGH-65RX5ELGH-5E, LGH-80RX5ELGH-5E, LGH-100RX5ELGH-5E), designed for air exchange, energy saving and maintaining relative humidity in rooms for various purposes. They are perfect for country houses, cottages, apartments and commercial premises. The main distinguishing feature of LOSSNEY units is high efficiency and low power consumption. Made in Japan.

Price: 29 500 RUB

Series of installations inlet recuperative ventilation, Electrolux ( EPVS-200, EPVS-300, EPVS-450, EPVS-650, EPVS-1100, EPVS-1300), designed for air exchange, energy saving and maintaining relative humidity in rooms for various purposes. They are perfect for country houses, cottages, apartments and commercial premises. The main distinguishing feature of Electrolux STAR units is high efficiency up to 90% and low power consumption.

Price: 131 000 RUB

A series of air handling units with plate heat exchanger, TURKOV ZENIT ( 200 heco, 350 heco, 450 heco, 550 heco), designed for ventilation, energy saving and maintaining relative humidity in rooms for various purposes. They are perfect for country houses, cottages, apartments and commercial premises. TURKOV air handling units with heat recovery have the ability to connect an electric heater 1.5 kW, which allows you to control the temperature of the incoming air into the room.
Office for WIFI and MODBAS with smart home system.

Price: 29 400 RUB

Series of supply and exhaust ventilation units with plate heat exchanger, Dantex DV ( DV-200HRE DV-250HRE DV-350HRE DV-400HRE DV-500E DV-600HRE DV-800HRE DV-1000HRE DV-1200HRE), designed for ventilation, energy saving and maintaining relative humidity in rooms for various purposes. They are perfect for country houses, cottages, apartments and commercial premises. Dantex air handling units with heat recovery have the ability to control the temperature of the incoming air into the room and low power consumption.

Price: 36 500 RUB

A series of air handling units with heat recovery, Royal Clima ( RCS 350, RCS 500, RCS 650, RCS 950, RCS 1350, RCS 1500), designed for air exchange, energy saving and maintaining relative humidity in rooms for various purposes. High efficiency and low power consumption.

Price: 87 900 RUB

With rotary heat exchanger, UNI ( Norway) are designed for ventilation and energy saving in the premises of country houses, cottages, apartments. The main distinguishing feature of the installations is built-in electric air heater allowing to regulate the temperature of the outgoing air into the room, low power consumption and a wide range of operating temperatures. Supply and exhaust UNI units can be connected to the "Smart Home" system via the MODBUS protocol.

According to what parameters to choose a heat exchanger and where to install it, what rooms to connect to the heat exchanger - recommendations of experts.

As part of the project, we decided to answer the questions of portal users regarding the selection and installation of recuperators.

Of these installations, it will be put into operation at our construction site, which determined the subject of this article. Questions regarding the types of ventilation systems and the criteria by which recuperators should be selected, we will analyze with the help of manufacturers - engineers of the TURKOV company.

In this article:

• types of ventilation systems;
• what are the advantages of the recuperator;
• according to what parameters should a recuperator be chosen;
• basic and additional functions of the recuperator;
• sanitary standards for the installation and connection of the heat exchanger.

So, why is the supply and exhaust system chosen? To fully understand the issue, consider the varieties of modern supply and exhaust systems.

natural ventilation

Natural ventilation - a system that includes wall and window inlet valves (providing fresh air access to the room), as well as an exhaust duct system (removing exhaust air from toilets, bathrooms and kitchens). The possibility of air exchange in the presence of natural ventilation is provided by the difference in temperatures inside and outside the room.

The advantages of such a system are its simplicity and low cost, the disadvantages include low efficiency and insufficient quality of air exchange. Also, the disadvantages include a large load on the heating system and seasonal instability. For example, in summer, when the temperature of the indoor and outdoor air equalizes, the air exchange in the room practically stops. In winter, on the contrary, the system works more efficiently, but this requires additional costs for heating the air coming from the street.

Combined system

Combined ventilation - a system with forced exhaust and natural air supply. Its disadvantages:

1. The energy efficiency of a combined system is even lower than that of natural ventilation. The fact is that fans create a stable flow of exhaust air, and this significantly increases the load on the heating system.
2. Poor quality of air exchange in the house (the hood does not work constantly, but only in the process of using bathrooms and kitchens). Even with the constant operation of the exhaust fans, the air exchange in the room will not be able to reach the level that is necessary for a comfortable stay.

The advantages of the combined system are its relatively low cost and the absence of seasonal problems with draft in the exhaust duct. However, in terms of the level of air exchange and functionality, the combined system falls far short of a full-fledged supply and exhaust ventilation.

Classic forced system

Classical forced ventilation ensures the circulation of air flows in the given modes and volumes. This system is equipped with supply and exhaust air ducts, as well as specialized ventilation equipment capable of maintaining stable air exchange in the room all year round. Such systems have one big disadvantage: they are very energy-intensive when used in winter. This is explained by the fact that the cold air flow from the street must be constantly heated to a comfortable room temperature.

Forced system with recuperator

Forced ventilation with a heat exchanger is the most advanced system capable of circulating air flows in specified modes and volumes. Its operation is associated with minimal energy consumption. After all, the flow from the street is first heated by a heat exchanger (due to the heat contained in the exhaust air), and then the air is additionally heated to a temperature comfortable for a person. In many developed countries, such a technical solution has already become a building standard, enshrined at the legislative level.

Taking into account the growing requirements for the comfort of residential premises, it is advisable to equip any new house not just with standard ventilation ducts, but with a multifunctional and economical forced ventilation system. The system based on the heat exchanger provides the supply of clean air with a comfortable temperature and at the same time removes the exhaust air masses outside the premises. At the same time, heat (and sometimes moisture) is removed from the exhaust stream and transferred to the supply stream.

Why did you choose an enthalpy heat exchanger

Firstly, unlike classical ventilation, the heat exchanger allows you to significantly save on the operation of the equipment. Secondly, the cost of the heat exchanger is not much higher than the cost of classical ventilation equipment. Thirdly, during the operation of the heat exchanger, 80% of the heat of the exhaust air is returned back to the supply air, which significantly reduces the cost of heating it.

On hot summer days, heat transfer occurs in the opposite direction, which also saves on air conditioning. Simultaneously with the transfer of heat in the heat exchanger, moisture is transferred from the exhaust air to the supply air. In physics there is such a thing as "dew point". This is the moment when the relative humidity of the air reaches 100% and the moisture changes from gas to liquid (condensate). Condensate appears on the surface of the heat exchanger, and the lower the outside temperature, the more likely it is that condensate will form on the heat exchanger. Since the enthalpy heat exchanger allows moisture to be transferred from the exhaust air to the supply air, the “dew point” shifts to the zone of very low temperatures. The heat exchanger allows to maintain a higher relative humidity of the supply air (compared to classical ventilation), and also significantly increases frost resistance and eliminates the need for condensate removal.

The presence of the above functions fully explains the choice of such a supply and exhaust unit.

We present a functional diagram of the installation.

Where:
M1 and M2 - supply and exhaust fans;
D (1, 2, 3) – temperature sensors;
K (1, 2, 3) - heat exchangers;
F (1, 2) - air filters.

What are the parameters to choose a recuperator

The first thing you need to pay attention to when choosing a model of a supply and exhaust heat exchanger is the wording used by the equipment manufacturer or seller. Often we hear the following: “efficiency up to 99%”, “efficiency up to 100%”, “operation up to -50ºС” - all these phrases are nothing more than a manifestation of a marketing strategy with a simultaneous attempt to mislead the buyer. As the experience of operating recuperators in the Russian climate has shown, metal recuperators work stably when the temperature drops to -10ºС. Then the process of reducing the efficiency begins due to freezing of the heat exchanger. To prevent this from happening, many manufacturers use additional heating sources (electric preheating).

The second thing you need to pay attention to is the thickness of the equipment case, the material from which the frame of the case is made and the presence of cold bridges in the case. Again we return to the experience of use: consider the features of the case with a thickness of 30mm. This case does not withstand outdoor temperatures down to -5ºС and must be additionally insulated. If the case is made of an aluminum frame, then additional insulation will also become an integral part of it. After all, aluminum is one big bridge of cold, "spread out" around the entire perimeter of the case.

Thirdly, one of the common mistakes when choosing a heat exchanger is that the buyer does not take into account the free pressure of the fans. He sees only the magic figure - 500 m³ and the price - 50 thousand rubles, and that the fan has a pressure of 0 Pa at 500 m³, the buyer learns only after the repair of the house is completed, that is, during the operation of already installed equipment.

The fourth selection criterion is the availability of automation and the ability to connect optional components to it. Automation can significantly reduce operating costs and achieve maximum comfort when operating equipment.

With regard to performance: the main design parameter is the volume of air that must enter the room within one hour. In accordance with sanitary standards, this volume should be equal to 60 m³ per adult or one hour per hour of the total cubic capacity of the premises served (living room, kitchen, bedrooms). When choosing a heat exchanger, you need to look not only at the performance of the installation, but also at the pressure of the fans that pump your ventilation network around the house.

It is better to entrust the calculation of the required performance to specialists. Indeed, in the event of an error, the replacement of the heat exchanger will require tangible financial costs.

When calculating and choosing an installation, in order to obtain more accurate information, you will have to read specialized literature and forums, call equipment manufacturers and suppliers (the topic is very extensive). It is always better to turn to specialists. And for those people whom this advice does not stop, it is still recommended to confirm the correctness of the choice with the equipment manufacturer or distributor.

The choice of heat exchanger according to the type of construction

It cannot be said that some recuperator is worse or better, each type of recuperator has its own strengths and areas of application. The efficiency of a rotary and plate heat exchanger is absolutely the same, since the efficiency depends on two parameters: the area of ​​the heat exchange surface of the heat exchanger and the direction of the air flow in the heat exchanger.

The design of the rotary heat exchanger allows partial mixing of the supply and exhaust flows, since the brush is the insulator of the air flows in it. Fine bristle brush, in itself, is a poor insulator between air flows, and a slight imbalance in the system leads to an even greater overflow of exhaust air into the supply duct. Also, the weak link in the rotary heat exchanger is the engine and the belt that turns the rotor: additional moving parts reduce the overall reliability of the equipment, as well as increase energy costs for recuperation. The rotary heat exchanger can only be installed in one position, which also reduces the possibility of its use at home. The main objects for the use of rotary heat exchangers are shopping centers, hypermarkets and other public buildings with a large area, where air flow is only for the benefit of the building owners.

We present a diagram of the operation of a rotary heat exchanger.

Plate heat exchangers, unlike rotary devices, are not so massive, but at the same time they are easy to install and reliable in operation. Among plate heat exchangers, membrane-type equipment deserves special attention. A special polymer membrane built into the heat exchanger returns moisture from the exhaust air to the supply air. At the same time, it prevents the formation of condensate, as well as the formation of ice inside the device (during its operation at low temperatures).

On the basis of plate heat exchangers, it is possible to build a multi-stage recuperation, which avoids direct contact of the coldest air flow (coming from the street) with the warmest one (coming from the house). And in conjunction with an enthalpy heat exchanger, this technology allows you to avoid freezing of the heat exchanger. A smooth decrease in the temperature of the exhaust air and a gradual increase in the temperature of the supply air inside the heat exchanger make the device resistant even to the temperatures of the Far North. As practice shows, such equipment successfully operates in the most severe climatic conditions, for example, in Yakutsk.

PiterPro FORUMHOUSE user

Plate heat exchangers use different materials. Plastic and metal heat exchangers freeze up. Membrane heat exchangers use a thin film that only allows moisture to pass through. There are two or three heat exchangers in such an installation at once, depending on the model.

Efficiency is one of the main characteristics of the heat exchanger, and special attention should be paid to its value before purchasing the unit.

It is important to choose a heat exchanger for your home that has sensitive and reliable automation. After all, there is nothing worse than equipment that is constantly involved in work and requires attention with enviable regularity. Modern automation of recuperators opens up additional opportunities for users:

• separate adjustment of the supply and exhaust fan;
• air conditioning control;
• humidifier control;
• automation and dispatching.

And the design features allow you to equip the device with additional options and systems:

• automatic fan power control system - VAV-system (maintaining a constant air flow);
• system of automatic adjustment of air flow by CO2 sensor (regulates the pressure of the air flow depending on the content of carbon dioxide in the exhaust duct);
• timer with multiple events per day;
• water or electric air heaters;
• additional air dampers;

This also includes an improved filtration system.

When choosing equipment, it is necessary to consider the air handling unit as a climatic complex that will maintain air flow, as well as temperature and humidity (if necessary) in a given mode. Installing additional heaters, coolers, VAV valves, humidifiers or dehumidifiers is already becoming a vital necessity today.

Shuvalov Dmitry

If the heat exchanger itself cannot maintain the desired supply air temperature, then the device should be retrofitted with a heater of the appropriate power. On average, if the design temperature in the duct does not fall below +14...+15°C, then the heater may not be installed. My opinion is this: it is better not to turn on the heater if it is not needed, than when it is needed - there will be nothing to turn on.

The systems and devices listed above make it possible to minimize human participation in system management and improve the quality of the microclimate in the house. A modern climate system is able to constantly monitor the performance of all units of optional equipment and, if necessary, warn the user about problems in the operation of the system and changes in the microclimate in the room. When using a VAV system, the operating costs of the installation are significantly reduced by temporarily and / or partial disconnection of individual rooms from the ventilation system.

Currently, there are models of recuperators that are able to connect to individual "" systems using the ModBus or KNX protocols. Such devices are ideal for connoisseurs of advanced and modern functionality.

Additional selection criteria

When choosing a heat exchanger, it is important to pay attention to the noise level that it creates during operation. This indicator depends on the material from which the device case is made, on the thickness of the case, on the power of the fans, and on other parameters.

According to the type of installation, recuperators are suspended (mounted on the ceiling) and floor-mounted (installed on a flat horizontal surface or hung on a wall). Outlets for ventilation ducts can be either on two sides (“through” layout) or on one side (“vertical” layout). Which heat exchanger is right for you - it depends on the specific parameters of your ventilation system and on where exactly the supply and exhaust equipment will be installed.

Installation recommendations mainly refer to the rooms in which the heat exchanger should be installed. First of all, boiler rooms are used for installation (if we are talking about private households). Also, recuperators are mounted in basements, attics and other technical rooms.

If this does not differ from the requirements of the technical documentation, then the unit can be installed in any unheated room, while the wiring of ventilation ducts, if possible, should be installed in rooms with heating.

Ventilation ducts passing through unheated premises (as well as outdoors) should be made as insulated as possible. Air ducts running from the equipment to the street (supply and exhaust) are also necessarily insulated. It is also necessary to insulate the nodes of the passage of air ducts through the outer walls.

Considering the noise that the equipment can produce during operation, it is best to place it away from bedrooms and other living areas.

As for the placement of the heat exchanger in the apartment: the best place for it would be a balcony or some technical room.

In the absence of such an opportunity, free space in the dressing room can be allocated for the installation of the heat exchanger.

Be that as it may, the location of the installation largely depends on the layout of the apartment or house, on the layout and location of the ventilation network, and on the dimensions of the device.

Particular attention is recommended to be paid to such an element as a crossbar. Already existing crossbars can become a big problem when laying a ventilation network. You can get around this element only through a technical room or a built-in closet, which is far from always possible. Therefore, you should think about the ventilation project even when designing a house, having previously provided for the presence of walk-through windows in the crossbar. The same recommendation applies to the nodes of the passage through the roof.

Residential premises can be equipped with both exhaust and supply channels - at the same time, but in most cases, supply channels are sufficient. The hood in this case is made "central", as a rule, representing one or two exhaust points located in the corridors.

As for kitchens and bathrooms: these rooms should be equipped with separate exhaust hoods that dispose of the exhaust air into the general ventilation ducts (in apartments) or outside (in private houses).

However, there are situations in which the connection of bathrooms to a ventilation system with a heat exchanger is allowed (please note that we are talking about rooms, and not about exhaust hoods located in these rooms). But due to the cold Russian climate, with such a connection, it is necessary to observe a lot of nuances, which is far from always possible. In any case, with the question of the possibility of such a connection, you need to contact the relevant specialists. It is strongly not recommended to independently connect bathrooms to the heat exchanger.