Air handling units with heat recovery- ventilation equipment designed to supply fresh air from the street into the premises and at the same time remove old, exhaust air with a low oxygen content. Supply air is blown into the outer chamber by means of a fan, and then distributed throughout the rooms through diffusers. The exhaust fan removes the exhaust air through special valves.
The main problem of intensive air exchange with the help of supply and exhaust ventilation is high heat loss. To minimize them, supply and exhaust units with heat recovery were developed, which made it possible to reduce heat losses by several times and reduce the cost of space heating by 70-80%. The principle of operation of such installations is to utilize the heat of the outgoing air flow by transferring it to the supply air.
When equipping an object air handling unit with recuperation of heat, warm exhaust air is taken through air intakes located in the most humid and polluted rooms (kitchens, bathrooms, sanitary facilities, utility rooms, etc.). Before leaving the building, the air passes through the heat exchanger heat exchanger, transferring heat to the incoming (supply) air. Heated and purified supply air enters the premises through air ducts through bedrooms, living rooms, offices, etc. This ensures constant air circulation, while the incoming air is heated by the heat given off by the exhaust air.
Types of recuperators
Air handling units can be equipped with several types of recuperators:
- plate heat exchangers are one of the most common designs of heat exchangers. Heat exchange is carried out by passing supply and exhaust air through a series of plates. Condensation may form in the heat exchanger during operation, therefore plate heat exchangers are additionally equipped with a condensate drain. Heat exchange efficiency reaches 50-75%;
- rotary recuperators - heat exchange is carried out by means of a rotating rotor, and its intensity is regulated by the speed of rotation of the rotor. The rotary heat exchanger has a high heat exchange efficiency - from 75 to 85%;
- less common types are recuperators with an intermediate heat carrier (water or a water-glycol solution acts as its role) with an efficiency of up to 40-60%, chamber recuperators divided into two parts by a damper (efficiency up to 90%) and heat pipes filled with freon (efficiency 50-70%).
Order air handling units with recuperation heat in the MirCli online store on a turnkey basis - with delivery and professional installation.
The creation of an energy-efficient administrative building that will be as close as possible to the PASSIVE HOUSE standard is impossible without a modern air handling unit (PSU) with heat recovery.
Under recovery means the process of utilizing the heat of the internal exhaust air with a temperature of t in, emitted during the cold period with a high temperature to the street, to heat the supply outdoor air. The heat recovery process takes place in special heat recovery units: plate heat exchangers, rotating regenerators, as well as in heat exchangers installed separately in air flows with different temperatures (in exhaust and supply units) and connected by an intermediate heat carrier (glycol, ethylene glycol).
The latter option is most relevant in the case when the supply and exhaust are separated along the height of the building, for example, the supply unit is in the basement, and the exhaust unit is in the attic, however, the recovery efficiency of such systems will be significantly lower (from 30 to 50% compared to PES in one building
Plate heat exchangers are a cassette in which the supply and exhaust air channels are separated by aluminum sheets. Heat exchange takes place between the supply and exhaust air through aluminum sheets. The internal extract air heats the external supply air through the heat exchanger plates. In this case, the process of mixing air does not occur.
AT rotary heat exchangers heat transfer from exhaust air to supply air is carried out through a rotating cylindrical rotor, consisting of a package of thin metal plates. During the operation of the rotary heat exchanger, the exhaust air heats the plates, and then these plates move into the cold outside air and heat it. However, in the flow separation units, due to their leakage, the exhaust air flows into the supply air. The percentage of overflow can be from 5 to 20% depending on the quality of the equipment.
In order to achieve the set goal - to bring the FGAU "NII CEPP" building closer to the passive one, in the course of long discussions and calculations, it was decided to install supply and exhaust ventilation units with a heat exchanger from the Russian manufacturer of energy-saving climate systems - the company TURKOV.
Company TURKOV produces PES for the following regions:
- For the Central region (equipment with two-stage heat recovery ZENIT series, which works stably up to -25 about C, and is excellent for the climate of the Central region of Russia, efficiency 65-75%);
- For Siberia (equipment with three-stage heat recovery Zenit HECO series works stably up to -35 about C, and is excellent for the climate of Siberia, but is often used in the central region, efficiency 80-85%);
- For the Far North (equipment with four-stage recuperation CrioVent Series works stably up to -45 about C, excellent for extremely cold climates and used in the most severe regions of Russia, efficiency up to 90%).
However, the TURKOV PES uses enthalpy plate heat exchanger, in which, along with the transfer of implicit heat from the exhaust air, moisture is also transferred to the supply air.
The working area of the enthalpy heat exchanger is made of a polymer membrane, which allows water vapor molecules to pass from the exhaust (humidified) air and transfer it to the supply (dry) one. There is no mixing of exhaust and supply flows in the heat exchanger, since moisture is passed through the membrane by diffusion due to the difference in vapor concentration on both sides of the membrane.
The dimensions of the membrane cells are such that only water vapor can pass through it, for dust, pollutants, water droplets, bacteria, viruses and odors, the membrane is an insurmountable barrier (due to the ratio of the sizes of the "cells" of the membrane and other substances).
Enthalpy heat exchanger in fact - a plate heat exchanger, where a polymer membrane is used instead of aluminum. Since the thermal conductivity of the membrane plate is less than that of aluminum, the required area of the enthalpy heat exchanger is much larger than the area of a similar aluminum heat exchanger. On the one hand, this increases the dimensions of the equipment, on the other hand, it allows you to transfer a large amount of moisture, and it is thanks to this that it is possible to achieve high frost resistance of the heat exchanger and stable operation of the equipment at ultra-low temperatures.
In winter (outdoor temperature below -5C), if the humidity of the exhaust air exceeds 30% (at an exhaust air temperature of 22…24 °C), in the heat exchanger, together with the process of transferring moisture to the supply air, the process of moisture accumulation on the heat exchanger plate takes place. Therefore, it is necessary to periodically turn off the supply fan and dry the hygroscopic layer of the heat exchanger with exhaust air. The duration, frequency and temperature below which the drying process is required depends on the heat exchanger gradation, temperature and humidity inside the room. The most commonly used heat exchanger drying settings are shown in Table 1.
Table 1. Most commonly used heat exchanger drying settings
| Heat exchanger steps | Temperature/Humidity | ||||
|
|
<20% | 20%-30% | 30%-35% | 35%-45% | |
| 2 steps | not required | 3/45 min | 3/30 min | 4/30 min | |
| 3 steps | not required | 3/50 min | 3/40 min | 3/30 min | |
| 4 steps | not required | 3/50 min | 3/40 min | ||
Drying the heat exchanger is required only when installing air humidification systems, or when operating equipment with large, systematic moisture inflows.
- With standard indoor air parameters, the dry mode is not required.
In this article, as an example of an administrative building, a typical five-story building of the FGAU "NII CEPP" after the planned reconstruction is considered.
For this building, the flow rate of supply and exhaust air was determined in accordance with the norms of air exchange in the administrative premises for each building room.
The total values of supply and exhaust air flow rates by floors of the building are shown in Table 2.
Table 2. Estimated supply/exhaust air flow rates by building floors
| Floor | Supply air consumption, m 3 /h | Exhaust air consumption, m 3 /h | PVU TURKOV |
| Basement | 1987 | 1987 | Zenit 2400 HECO SW |
| 1st floor | 6517 | 6517 |
Zenit 1600 HECO SW Zenit 2400 HECO SW Zenit 3400 HECO SW |
| 2nd floor | 5010 | 5010 | Zenit 5000 HECO SW |
| 3rd floor | 6208 | 6208 |
Zenit 6000 HECO SW Zenit 350 HECO MW - 2 pcs. |
| 4th floor | 6957 | 6957 | Zenit 6000 HECO SW Zenit 350 HECO MW |
| 5th floor | 4274 | 4274 |
Zenit 6000 HECO SW Zenit 350 HECO MW |
In laboratories, PVUs work according to a special algorithm with compensation for exhaust from fume hoods, i.e. when any fume hood is turned on, the PVU hood automatically decreases by the value of the cabinet hood. Based on the estimated costs, the Turkov air handling units were selected. Each floor will be served by its Zenit HECO SW and Zenit HECO MW PES with three-stage heat recovery up to 85%.
The ventilation of the first floor is carried out by PES, which are installed in the basement and on the second floor. The ventilation of the remaining floors (except for the laboratories on the fourth and third floors) is provided by PES installed on the technical floor.
The appearance of the PES of the Zenit Heco SW installation is shown in Figure 6. Table 3 shows the technical data for each PES of the installation.
Installation Zenit Heco SW includes: - Housing with heat and sound insulation;
- Supply fan;
- Exhaust fan;
- supply filter;
- Exhaust filter;
- 3-stage heat exchanger;
- Water heater;
- Mixing unit;
- Automation with a set of sensors;
- Wired control panel.
An important advantage is the possibility of mounting the equipment both vertically and horizontally under the ceiling, which is used in the building in question. As well as the ability to locate equipment in cold areas (attics, garages, technical rooms, etc.) and on the street, which is very important in the restoration and reconstruction of buildings.
PES Zenit HECO MW are small PES with heat and moisture recovery with a water heater and a mixing unit in a lightweight and versatile housing made of expanded polypropylene, designed to maintain the climate in small rooms, apartments, houses.
Company TURKOVindependently developed and manufactures in Russia the Monocontroller automation for ventilation equipment. This automation is used in PVU Zenit Heco SW
- The controller controls EC fans via MODBUS, which allows you to monitor the operation of each fan.
- Controls water heaters and coolers to accurately maintain the temperature of the supply air in both winter and summer periods.
- For CO control 2 in the conference room and meeting rooms, automation is equipped with special CO sensors 2 . The equipment will monitor the concentration of CO 2 and automatically change the air flow according to the number of people in the room to maintain the required air quality, thereby reducing the heat consumption of the equipment.
- A complete dispatching system allows you to organize the control center as simply as possible. A remote monitoring system will allow you to monitor the equipment from anywhere in the world.
Control panel features:
- Hours, date;
- Three fan speeds;
- Filter status display in real time;
- Weekly timer;
- Supply air temperature setting;
- Display of faults on the display.
Efficiency mark
To assess the effectiveness of installing Zenit Heco SW air handling units with heat recovery in the building under consideration, we determine the calculated, average and annual loads on the ventilation system, as well as the costs in rubles for the cold period, the warm period and for the whole year for three PES options:
- PES with recuperation Zenit Heco SW (recuperator efficiency 85%);
- Direct-flow PES (i.e. without heat exchanger);
- PES with 50% heat recovery efficiency.
The load on the ventilation system is the load on the air heater, which heats up (during the cold period) or cools (during the warm period) the supply air after the heat exchanger. In a direct-flow PES, the air is heated in the heater from the initial parameters corresponding to the parameters of the outside air during the cold period, and cools during the warm period. The calculation results of the design load on the ventilation system in the cold period for the floors of the building are shown in Table 3. The results of the calculation of the design load on the ventilation system in the warm season for the entire building are shown in Table 4.
Table 3. Estimated load on the ventilation system during the cold period by floors, kW
| Floor | PES Zenit HECO SW/MW | Direct flow PES | PES with 50% recovery |
| Basement | 3,5 | 28,9 | 14,0 |
| 1st floor | 11,5 | 94,8 | 45,8 |
| 2nd floor | 8,8 | 72,9 | 35,2 |
| 3rd floor | 10,9 | 90,4 | 43,6 |
| 4th floor | 12,2 | 101,3 | 48,9 |
| 5th floor | 7,5 | 62,2 | 30,0 |
| 54,4 | 450,6 | 217,5 |
Table 4. Estimated load on the ventilation system during the warm period by floors, kW
| Floor | PES Zenit HECO SW/MW | Direct flow PES | PES with 50% recovery |
| 20,2 | 33,1 | 31,1 |
Since the calculated outdoor temperatures in the cold and warm periods are not constant during the heating period and the cooling period, it is necessary to determine the average ventilation load at an average outdoor temperature:
The results of calculating the annual load on the ventilation system during the warm period and the cold period for the entire building are shown in tables 5 and 6.
Table 5. Annual load on the ventilation system during the cold season by floors, kW
| Floor | PES Zenit HECO SW/MW | Direct flow PES | PES with 50% recovery |
| 66105 | 655733 | 264421 | |
| 66,1 | 655,7 | 264,4 |
Table 6. Annual load on the ventilation system during the warm season by floors, kW
| Floor | PES Zenit HECO SW/MW | Direct flow PES | PES with 50% recovery |
| 12362 | 20287 | 19019 | |
| 12,4 | 20,3 | 19,0 |
Let us determine the costs in rubles per year for heating, cooling and fan operation.
The consumption in rubles for reheating is obtained by multiplying the annual values of ventilation loads (in Gcal) during the cold period by the cost of 1 Gcal / hour of thermal energy from the network and by the time the PVU is in heating mode. The cost of 1 Gcal / h of thermal energy from the network is taken equal to 2169 rubles.
The costs in rubles for the operation of fans are obtained by multiplying their power, operating time and the cost of 1 kW of electricity. The cost of 1 kWh of electricity is taken equal to 5.57 rubles.
The results of calculating the costs in rubles for the operation of the WSP in the cold period are shown in Table 7, and in the warm period in Table 8. Table 9 compares all WSP options for the entire building of the FGAU "NII CEPP".
Table 7. Expenses in rubles per year for the operation of PES during the cold period
| Floor | PES Zenit HECO SW/MW | Direct flow PES | PES with 50% recovery | |||
| For reheating | For fans | For reheating | For fans | For reheating | For fans | |
| Total costs | 368 206 | 337 568 | 3 652 433 | 337 568 | 1 472 827 | 337 568 |
Table 8. Costs in rubles per year for the operation of WSPs during the warm period
| Floor | PES Zenit HECO SW/MW | Direct flow PES | PES with 50% recovery | |||
| For cooling | For fans | For cooling | For fans | For cooling | For fans | |
| Total costs | 68 858 | 141 968 | 112 998 | 141 968 | 105 936 | 141 968 |
Table 9. Comparison of all PES
| Value | PES Zenit HECO SW/MW | Direct flow PES | PES with 50% recovery |
| , kW | 54,4 | 450,6 | 217,5 |
| 20,2 | 33,1 | 31,1 | |
| 25,7 | 255,3 | 103,0 | |
| 11,4 | 18,8 | 17,6 | |
| 66 105 | 655 733 | 264 421 | |
| 12 362 | 20 287 | 19 019 | |
| 78 468 | 676 020 | 283 440 | |
| Reheating costs, rub | 122 539 | 1 223 178 | 493 240 |
| Cooling costs, rub | 68 858 | 112 998 | 105 936 |
| Costs for fans in winter, rub | 337 568 | ||
| Costs for fans in summer, rub | 141 968 | ||
| Total annual costs, rub | 670 933 | 1 815 712 | 1 078 712 |
An analysis of Table 9 allows us to draw an unambiguous conclusion - the supply and exhaust units Zenit HECO SW and Zenit HECO MW with heat and moisture recovery from Turkov are very energy efficient.
The total annual ventilation load of the TURKOV PVU is less than the load in the PVU with an efficiency of 50% by 72%, and in comparison with the direct-flow PVU by 88%. PVU Turkov will save 1 million 145 thousand rubles - in comparison with a direct-flow PVU or 408 thousand rubles - in comparison with a PVU, the efficiency of which is 50%.
Where are the savings...
The main reason for failures in the use of systems with recuperation is the relatively high initial investment, however, with a more complete look at the development costs, such systems not only pay off quickly, but also reduce the overall investment during development. use of residential, office buildings and shops.
Average value of heat losses of finished buildings: 50 W/m 2 .
- Inclusions: Heat loss through walls, windows, roofs, foundations, etc.
Included:
- Ventilation of apartments with the calculation of the purpose of the premises and the multiplicity.
- Ventilation of offices based on the number of people and CO2 compensation.
- Ventilation of shops, corridors, warehouses, etc.
- Area ratio selected based on several existing complexes
Included:
- Compensation for bathrooms, bathrooms, kitchens, etc. Since it is impossible to organize an intake into the recuperation system from these rooms, an inflow is organized into this room, and the exhaust goes by separate fans past the recuperator.
Difference between supply air quantity and compensation air quantity.
It is this volume of extract air that transfers heat to the supply air.
So, it is necessary to build up the area with standard buildings with a total area of 40,000 m 2 with the specified heat loss characteristics. Let's see what will save the use of ventilation systems with recuperation.
Operating costs
The main goal of choosing systems with recuperation is to reduce the cost of equipment operation, due to a significant reduction in the required heat output for heating the supply air.
With the use of supply and exhaust ventilation units without recuperation, we will get the heat consumption of the ventilation system of one building 2410 kWh.
- We take the cost of operating such a system as 100%. There is no savings at all - 0%.
With the use of combined supply and exhaust ventilation units with heat recovery and an average efficiency of 50%, we will get the heat consumption of the ventilation system of one building 1457 kWh.
- Operating cost 60%. Savings with typesetting equipment 40%
With the use of TURKOV single-block highly efficient supply and exhaust ventilation units with heat and moisture recovery and an average efficiency of 85%, we will get the heat consumption of the ventilation system of one building 790 kWh.
- Operating cost 33%. Savings with TURKOV equipment 67%
As can be seen, ventilation systems with highly efficient equipment have less heat consumption, which allows us to talk about the equipment payback period of 3-7 years when using water heaters and 1-2 years using electric heaters.
Construction costs
If building in the city, it is necessary to allocate a significant amount of thermal energy from the existing heating network, which always requires significant financial costs. The more heat is required, the more expensive the cost of summing up will be.
Building "in the field" often does not involve the supply of heat, gas is usually supplied and the construction of its own boiler house or thermal power plant is carried out. The cost of this structure is commensurate with the required thermal power: the more - the more expensive.
As an example, suppose that a boiler house with a capacity of 50 MW of thermal energy has been built.
In addition to ventilation, the cost of heating a typical building with an area of 40,000 m 2 and heat loss of 50 W/m 2 will be about 2000 kWh.
With the use of supply and exhaust ventilation units without recuperation, it will be possible to build 11 buildings.
With the use of combined supply and exhaust ventilation units with heat recovery and an average efficiency of 50%, it will be possible to construct 14 buildings.
With the use of TURKOV single-block highly efficient supply and exhaust ventilation units with heat and moisture recovery and an average efficiency of 85%, it will be possible to build 18 buildings.
The final estimate for supplying more heat energy or building a high-capacity boiler house is significantly more expensive than the cost of more energy-efficient ventilation equipment. With the use of additional means to reduce the heat loss of the building, it is possible to increase the development without increasing the required heat output. For example, by reducing heat loss by only 20%, to 40 W / m 2, it will be possible to build 21 buildings already.
Features of equipment operation in northern latitudes
As a rule, equipment with recuperation has restrictions on the minimum outdoor air temperature. This is due to the capabilities of the heat exchanger and the limitation is -25 ... -30 o C. If the temperature drops, the condensate from the exhaust air will freeze on the heat exchanger, therefore, at extremely low temperatures, an electric preheater or a water preheater with antifreeze liquid is used. For example, in Yakutia, the estimated outdoor air temperature is -48 o C. Then the classic systems with recuperation work as follows:
- o With pre-heater heated up to -25 o C (Thermal energy is spent).
- C -25 o C air is heated in the heat exchanger to -2.5 o C (at 50% efficiency).
- C -2.5 o The air is heated by the main heater to the required temperature (thermal energy is consumed).
When using a special series of equipment for the Far North with 4-stage heat recovery TURKOV CrioVent, preheating is not required, since 4 stages, a large recuperation area and moisture return make it possible to prevent the heat exchanger from freezing. The equipment works in a graying way:
- Outdoor air with a temperature of -48 o C is heated in the recuperator up to 11.5 o C (efficiency 85%).
- From 11.5 o The air is heated by the main heater to the required temperature. (Thermal energy is spent).
The absence of preheating and the high efficiency of the equipment will significantly reduce heat consumption and simplify the design of the equipment.
The use of highly efficient recuperation systems in the northern latitudes is most relevant, since due to low outdoor air temperatures, the use of classical recuperation systems is difficult, and equipment without recuperation requires too much heat energy. Turkov equipment successfully works in cities with the most difficult climatic conditions, such as: Ulan-Ude, Irkutsk, Yeniseysk, Yakutsk, Anadyr, Murmansk, as well as in many other cities with a milder climate compared to these cities.
Conclusion
- The use of ventilation systems with recuperation allows not only to reduce operating costs, but in the case of large-scale reconstruction or capital development of cases, to reduce the initial investment.
- Maximum savings can be achieved in the middle and northern latitudes, where the equipment operates in difficult conditions with prolonged negative outdoor air temperatures.
- Using the building of FGAU NII CEPP as an example, a ventilation system with a highly efficient heat exchanger will save 3 million 33 thousand rubles a year compared to a direct-flow PVU and 1 million 40 thousand rubles a year compared to a stacked PVU, the efficiency of which is 50%.
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 control 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 represents a wide range of recuperators of different types, differing from each other both in design and in the method of heat exchange between flows.
- 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 recuperators include a fairly high efficiency, reaching 70%, the absence of moving parts, the absence of 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 prescribed 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 depends directly 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.
general information
The service life of the equipment for the ventilation unit manufactured by our company is set subject to the observance of the operating rules and the timely replacement of filters and parts with a limited resource. The list of such parts and their resource is indicated in the User's Manual for each specific model.
To avoid misunderstandings, we kindly ask you to carefully study the User Manual, pay attention to the conditions for the emergence of warranty obligations, check that the warranty card is filled out correctly. The warranty card is valid only in the presence of correctly and clearly indicated: model, serial number of the product, date of sale, clear seals of the seller, installer, buyer's signature. The model and serial number of the product must match those specified in the warranty card.
Warranty Limitations
In case of violation of these conditions, as well as in the case when the data specified in the warranty card is changed, erased or rewritten, the warranty card is invalidated.
In this case, we recommend that you contact the seller to obtain a new warranty card that meets the above conditions. In the event that the date of sale cannot be determined, in accordance with consumer protection legislation, the warranty period is calculated from the date of manufacture of the product.
Guarantee for recuperators 7 years.
A 7-year warranty applies to equipment operated in accordance with all operating rules prescribed in the "ZENIT Equipment Operation Manual". The warranty does not apply to equipment operated in rooms with high humidity (pools, saunas, rooms with humidity over 50% in winter), but the warranty can be maintained if the equipment is equipped with a duct dehumidifier.
Delivery in Moscow and the Moscow region up to 10 km from the Moscow Ring Road
Delivery times are indicated in the card of each product. Shipping costs are charged separately. Delivery is carried out by a transport company.
Delivery to regions
Delivery to the regions is made after 100% payment for the services of the transport company. Shipping costs are not included in the order price.
general information
If you want to know about the terms of delivery and payment, but do not want to read about them, then contact the sales assistant in your city, who will definitely help you.
Prices on the site may differ from retail prices in different regions, this is due to logistics costs. The price of the ordered goods is valid for 24 hours from the moment of placing the Order.
Payment by credit card on the site
Payment by credit card on the site is made through the payment system. After placing and paying for the order, our sales assistant will contact you to confirm the Order and specify the delivery time.
Issues discussed in the material:
- What is heat recovery ventilation
- Ventilation scheme with recuperation
- What are the advantages of a ventilation system with heat recovery?
- Types of recuperators for ventilation
- How to choose air handling units with heat recovery
- Tips on how to install the supply and exhaust ventilation with recuperation
Each person, of course, in his own way imagines how comfortable housing should be equipped. For one, the appearance and interior of the premises will be of paramount importance, while the other considers various amenities to be the most important. But no matter what we prefer, in any case, most will agree that in order for housing to be called comfortable, it is necessary that it has an optimal temperature - warm in the cold season, and cool in hot weather.
Of course, no matter how we create such conditions, they are always associated with certain costs. We can use devices like air conditioners, fans, heaters. Someone will prefer to carry out repairs in such a way as to make the premises airtight. And such a move will really help to save the internal temperature, but we must not forget that in such cases one serious trouble cannot be avoided - the housing will no longer be ventilated, so there will be no talk of any comfort. The only way out is to make ventilation to ensure the movement of air. Some may be worried about whether this will result in additional energy costs. But they will even decrease if your choice is ventilation with heat recovery for a private house, apartment or industrial facility. What is it, how does it work? This article will tell about this and much more.
What is heat recovery ventilation
Heat recovery home ventilation is one of the forced ventilation systems. As a rule, it provides for heating the air. This function is partially performed by a recuperator - a device designed to heat the air, although the main heating is provided not by it, but by the air heater.
Of course, you might never have heard of supply or exhaust ventilation with heat recovery, but this does not mean that it is a new invention. Most likely, you are misled by the Latin word "recuperation", which can be translated into Russian as "the return of what you spent." This reveals the whole point: a recuperator is a special heat exchanger, that is, a device that is quite common in ventilation systems, although in Russia it is still not used as often as abroad. How is the ventilation of a private house or apartment recuperated? Let's look at it in more detail.
Heat recovery - is the return of heat from the room. The bottom line is that there is an incoming and outgoing air flow. At the same time, the air that leaves the room heats the counter air due to heat transfer. This happens in the cold season, and on hot days, for example, in summer, the outgoing air, on the contrary, cools the incoming flows. But in such situations it is more correct to speak about cold recovery.
Obviously, such a procedure is necessary in order for the user to save available funds, because when ventilation is not equipped with recovery, a lot of heat goes outside instead of being reused indoors. Accordingly, heating bills increase, since, in fact, we heat the street, spending an exorbitant amount of heat for nothing. It is in order to avoid such waste and huge bills that it is worth thinking about installing ventilation with heat recovery. After all, this is how you return the air that you heated, do not allow heat to leave the room, save money.
It is not surprising that ventilation with recuperation is becoming more and more popular and there is nothing to oppose to the classic versions of ventilation systems with a similar design. This is logical, because forced ventilation with recuperation is not much more expensive than conventional ventilation, and its maintenance is completely elementary. In this regard, many prefer to forget about climate control equipment, which was once positioned as the most efficient in combination with ventilation systems. Recuperation is much more profitable both in terms of rational use of electricity and in terms of saving heating costs. Its cheapness is compared with the cost of lighting with energy-saving light bulbs.
What else attracts consumers to the supply and exhaust ventilation system with air recovery?
Firstly, such devices are small in size.
Secondly, they do not spoil the interior.
Thirdly they have low noise level.
Fourth, at a minimum of expenses we receive a maximum of efficiency of work.
They are also in demand in public institutions, among which the following can be listed:
- Cinemas and theaters.
- Canteens, cafes, snack bars.
- Libraries.
- Hotels and inns.
- Stations.
- Offices and commercial premises.
It is possible to design a ventilation system with recuperation of a private house, multi-storey building, etc. A variety of such devices allows you to choose them for any occasion. The different power of such structures makes it possible to find an option even for buildings in which there is a residential basement.
It is important to understand that supply ventilation with heat recovery for an apartment or house is a forced system. It is distinguished from the natural one by the presence of fans that provide the movement of air flows at any convenient time and do not depend on external factors, such as draft, which appears due to the difference in temperatures.
Ventilation scheme with recuperation
What are the advantages of a ventilation system with heat recovery?
As we have noted more than once, the main advantage of such a system is the ability to control the interaction of air inflow and exhaust. Due to this, we significantly reduce ventilation heat losses, although we continue to saturate the room with fresh air.
Now let's talk in more detail about each of the advantages of ventilation systems with recuperation.
Efficiency. Natural removal of air is not always a convenient solution, because we become dependent on circumstances, environmental conditions, temperature differences. In this regard, it is much easier to use a ventilation system with recuperation, capable of forcibly driving air. A simple example of forced ventilation is a kitchen hood. More complex devices are capable, among other things, of getting rid of excess moisture. But this is simple exhaust equipment. In our case, we are talking about supply and exhaust systems that can organize the movement of air flows in both directions at once, mix them and form the necessary temperatures for a comfortable stay of a person in the room, that is, to carry out air recovery.
Profitability. It should be noted that systems with recuperation are able to recoup their cost by saving on heating and electricity. Costs are significantly reduced, sometimes by 5 times, that is, you are already paying 80% less than usual. Ask your friends how much it costs them to heat a country house if you don’t have one. The numbers will be impressive. Imagine how much money recovery ventilation can save. In case of wear of inexpensive elements, they can be replaced without negative consequences. In the warm season, you can save on climate control equipment, while reducing emissions of harmful substances into the atmosphere. Yes, even from the point of view of ecology, you already cause much less damage to nature, because, among other things, you reduce the load on the network. And do not let it seem to you that one person is not enough. Firstly, these are quite serious amounts of energy. Secondly, there are more and more people who switch to ventilation with recuperation over the years.
Practicality. Ventilation systems with recuperation, as a rule, are small in size, which means they are easy to install. You can place such equipment in the bathroom, and in the closet, and build it into the ceiling. Today there are a huge number of models, for all tastes. So you don't have to worry about the interior.
Types of recuperators for ventilation
Recuperator - it is a heat exchanger, albeit a special one. It is connected to ventilation ducts that produce exhaust and air supply. Dirty air from the room gives off heat to the incoming flows, that is, a recovery procedure is performed.
Plate heat exchangers differ from the usual in that they prevent the mixing of air. In them, the recovery is carried out in a slightly different way. A number of plates are close to each other, due to which the air can transfer heat without touching. The material in such ventilation systems is typically aluminum foil, known for its thermal conductivity. There are plastic items. They are more expensive but more efficient.
Ventilation with heat recovery by means of plate heat exchangers often suffers from frost. The fact is that the surfaces of the heat exchanger are covered with ice due to condensate. This is not the most favorable effect on the quality of the device. And then the owner of ventilation with recuperation has to excel in order to make the ice melt. Accordingly, time, effort, and energy are wasted.
However, some developers have foreseen how to ensure the protection of ventilation with recovery from frost. To do this, a technology was invented that heats the incoming air flow to a temperature at which the condensate simply cannot freeze.
By the way, this is not the only way. Other developers have proposed equipping ventilation systems with recuperation with hygroscopic cellulose cassettes. We save on air heating, as such cellulose itself absorbs moisture, and then returns it at the exit. But they can only be used in cases where there is no waterlogging of the air.
Rotary recuperators. In heat recovery ventilation systems using these devices, the air is mixed. The principle of operation is as follows: the metal rotor rotates, providing the movement of air out and in. The rotation speed is usually adjustable.
As is clear, recovery in this case has a number of disadvantages, for example, it is much more expensive due to the presence of elements that fail over time. But high efficiency rates, reaching 90%, contribute to the popularity of such products.
In essence, the expediency of acquiring such a device largely depends on the efficiency of the organization of air recovery. A quality product usually pays for itself.
Recuperators with intermediate heat carrier. This device has two compartments separated by a reservoir of liquid capable of transferring heat from the outgoing incoming air.
Of course, the recovery in this case is very safe, because pollution is not transferred between flows. Speed adjustment is provided. Wear is unlikely. But the disadvantage is low efficiency, ranging from 45 to 60%.
Chamber recuperators. The shutter divides the compartment into two halves. As it rotates, it reverses the air currents. The change in temperature comes from the walls of the chamber.
Although air recovery in this case has a high efficiency rate of 70 to 80%, and wear is unlikely, it is characterized by the transmission of dirt and unpleasant odors.
heat pipes. This recovery device is made of hermetically connected tubes. They contain a substance that contributes to a change in air temperature. Most often it is one of the freons.
Closure prevents leakage of the substance. It just flows in different directions of the tube. The efficiency of such equipment is in the region of 50 - 70%.
How to choose air handling units with heat recovery
What should be kept in mind when choosing ventilation with heat recovery? You need to buy such equipment so as not to regret it, so ask the seller about the following nuances:
First, ask the seller the following questions:
- Who is the manufacturer of this ventilation with air recovery? How long has this company been operating, what reputation does it have, what else does it produce?
- How efficient is this ventilation with air recovery?
- What will be the resistance of the system to air flow after installation of this equipment?
- How expensive will it be to maintain ventilation with this heat exchanger? What is its energy class? What are the savings with this device?
- What are the Efficiencies of this heat exchanger for ventilation?
Here you need a specialist who can make a detailed calculation, based on the characteristics of your premises. It is clear that buying supply and exhaust ventilation with heat recovery for an apartment and a three-story building is not the same thing.
Here you again need expert advice. It is important not only to limit yourself to some general characteristics indicated in the table from the Internet, but to make a detailed calculation, for example, taking into account the number of bends in the duct and many other nuances. The ratio of air flow and system resistance is one of the most important selection factors.
Note that we say "ratios", not "ratio". Why? Isn't he alone? Not really. There is a declared one - this is some average value. And there is a real efficiency, which is an objective indicator. What does it depend on. Many factors. Here and humidity and air, and how the system is organized, and the temperature inside and outside.
- With a paper heat exchanger, the Efficiency will be between 60 and 70 percent. What does this mean for us? Is it good or bad? This means that air recovery ventilation is frost-resistant, although not one hundred percent.
- In the presence of an aluminum heat exchanger, the efficiency will be no more than 63%, while the efficiency of the air recuperator will be from 42 to 45% percent. Thus, you will have to use a significant amount of electricity to get rid of frost.
- The rotary air recuperator has excellent efficiency indicators, but on the condition that it is controlled automatically, based on the readings of special sensors. However, these heat exchangers can freeze in the same way as aluminum ones, which reduces efficiency.
What else should be considered when choosing a heat exchanger for ventilation?
Tips on how to install the supply and exhaust ventilation with recuperation
Now let's talk about how to install the supply and exhaust ventilation with recuperation. Let's start with how to choose the most suitable place for installation.
- If you have a private house, it is best to choose non-residential premises for installation. This is a basement, attic, utility room. And the boiler room is generally the most ideal option for supply and exhaust ventilation.
- Pay attention to the fact that the installation of ventilation with recuperation does not contradict the requirements specified in the technical documentation.
- It is best that the wiring of the ventilation system with air recovery falls on the premises where there is heating.
- Ventilation with air recovery is likely to pass through those rooms where there is no heating. These segments must be thoroughly insulated.
- It is necessary to insulate outdoor ventilation ducts with air recovery, as well as those located in the outer walls.
- It is advisable to locate ventilation equipment with air recovery in such a way that it is as far away from living quarters as possible so that the noise of work, which is never excluded, does not interfere.
Actually, these tips for installing ventilation with air recovery cannot be applied in all cases without exception. It is possible that you have other conditions and places where you can equip a similar system. Much depends on the layout of the building and the dimensions of the equipment.
Air intake for ventilation with recuperation, it is better to equip it on the side where the wind is less frequent. This will avoid dust and debris, or at least reduce their amount. When doing this, it is important to make sure that there are no chimneys, pipes or any other places where unwanted air can escape from.
Installation. It is strongly not recommended to install ventilation with air recovery on your own. This is a risky venture that can lead to unpleasant consequences. If you are reading this article, you are unlikely to be an expert in the field of installation of ventilation with recovery, so we recommend that you seek help from professionals.
That's all. We hope that the material was useful to you!
P.S. You can always call the company Climate Formula”, and our specialists will advise you on all the issues that have arisen.
