Creation of an energy efficient administrative building, which 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 inflow and exhaust are separated along the height of the building, for example, Supply unit- in the basement, and exhaust - in 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 goal - to bring the building of the FGAU "NII CEPP" closer to the passive, in the course of long discussions and calculations, it was decided to install supply and exhaust ventilation units with recuperator Russian manufacturer energy-saving climate systems - companies 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%).

Traditional study guides, based on the old school of engineering, criticize firms that claim the high efficiency of plate heat exchangers. Justifying this by the fact that it is possible to achieve this efficiency value only when using energy from absolutely dry air, and in real conditions with a relative humidity of the removed air = 20-40% (in winter), the level of use of dry air energy is limited.

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) air. 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 stages	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

Note: The setting of the heat exchanger drying is carried out only in agreement with the technical staff of the manufacturer and after providing the parameters of the internal air.

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.

The heat exchanger material undergoes mandatory antibacterial treatment, so it does not accumulate pollution.

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:

1. PES with recuperation Zenit Heco SW (recuperator efficiency 85%);
2. Direct-flow PES (i.e. without heat exchanger);
3. 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.

The average value of general exchange supply ventilation is 4.34 m 3 / m 2

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

The average value of ventilation to compensate for bathrooms, kitchens, etc. 0.36 m3/m2

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.

Average value of general exhaust ventilation respectively 3.98 m3/m2

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:

1. o With pre-heater heated up to -25 o C (Thermal energy is spent).
2. C -25 o C air is heated in the heat exchanger to -2.5 o C (at 50% efficiency).
3. 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:

1. Outdoor air with a temperature of -48 o C is heated in the recuperator up to 11.5 o C (efficiency 85%).
2. 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%.

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.

Air recirculation in ventilation systems is a mixture of a certain amount of exhaust (exhaust) air to the supply air. Thanks to this, a reduction in energy costs for heating fresh air in the winter period of the year is achieved.

Scheme of supply and exhaust ventilation with recovery and recirculation,
where L - air flow, T - temperature.

Heat recovery in ventilation- this is a method of transferring thermal energy from the exhaust air stream to the supply air stream. Recuperation is used when there is a temperature difference between the exhaust and supply air, to increase the temperature of the fresh air. This process does not involve mixing air flows, the process of heat transfer occurs through any material.

Temperature and air movement in the heat exchanger

Heat recovery devices are called heat recuperators. They are of two types:

Heat exchangers-recuperators- they transfer heat flow through the wall. They are most often found in installations of supply and exhaust ventilation systems.

In the first cycle, which are heated by the outgoing air, in the second they are cooled, giving off heat to the supply air.

The supply and exhaust ventilation system with heat recovery is the most common way to use heat recovery. The main element of this system is the supply and exhaust unit, which includes a heat exchanger. The device of the supply unit with a heat exchanger allows transferring up to 80-90% of heat to the heated air, which significantly reduces the power of the air heater, in which the supply air is heated, in case of a lack of heat flow from the heat exchanger.

Features of the use of recirculation and recovery

The main difference between recuperation and recirculation is the absence of air mixing from the room to the outside. Heat recovery is applicable for most cases, while recirculation has a number of limitations, which are specified in regulatory documents.

SNiP 41-01-2003 does not allow re-supply of air (recirculation) in the following situations:

• In rooms, the air flow in which is determined on the basis of emitted harmful substances;
• In rooms in which there are pathogenic bacteria and fungi in high concentrations;
• In rooms with the presence of harmful substances, sublimated upon contact with heated surfaces;
• In rooms of category B and A;
• In rooms where work is carried out with harmful or combustible gases, vapors;
• In rooms of category B1-B2, in which combustible dusts and aerosols can be released;
• From systems with the presence in them of local suction of harmful substances and explosive mixtures with air;
• From vestibules-sluices.

Recycling:
Recirculation in air handling units is actively used more often with high system productivity, when air exchange can be from 1000-1500 m 3 / h to 10000-15000 m 3 / h. The removed air carries a large supply of thermal energy, mixing it into the outside air flow allows you to increase the temperature of the supply air, thereby reducing the required power of the heating element. But in such cases, before being re-introduced into the room, the air must pass through the filtration system.

Recirculation ventilation improves energy efficiency, solves the problem of energy saving in the case when 70-80% of the exhaust air enters the ventilation system again.

Recovery:
Air handling units with recuperation can be installed at almost any air flow rate (from 200 m 3 /h to several thousand m 3 /h), both at low and at large. Recuperation also allows heat to be transferred from the extract air to the supply air, thereby reducing the energy demand on the heating element.

Relatively small installations are used in ventilation systems of apartments and cottages. In practice, air handling units are mounted under the ceiling (for example, between the ceiling and the suspended ceiling). This solution requires some specific requirements from the installation, namely: small overall dimensions, low noise level, easy maintenance.

The air handling unit with recuperation requires maintenance, which obliges to make a hatch in the ceiling for servicing the heat exchanger, filters, blowers (fans).

The main elements of air handling units

A supply and exhaust unit with recovery or recirculation, which has both the first and second processes in its arsenal, is always a complex organism that requires highly organized management. The air handling unit hides behind its protective box such main components as:

• Two fans of various types, which determine the performance of the installation by flow.
• Heat exchanger recuperator- heats the supply air by transferring heat from the exhaust air.
• Electric heater- heats the supply air to the required parameters, in case of a lack of heat flow from the exhaust air.
• Air filter- thanks to it, the control and purification of the outside air is carried out, as well as the processing of the exhaust air in front of the heat exchanger, to protect the heat exchanger.
• Air valves with electric drives - can be installed in front of the outlet air ducts for additional air flow control and channel blocking when the equipment is turned off.
• bypass- thanks to which the air flow can be directed past the heat exchanger during the warm season, thereby not heating the supply air, but supplying it directly to the room.
• Recirculation chamber- providing the admixture of the removed air into the supply air, thereby ensuring the recirculation of the air flow.
  
  

In addition to the main components of the air handling unit, it also includes a large number of small components, such as sensors, an automation system for control and protection, etc.

	Supply air temperature sensor		heat exchanger
	Extract air temperature sensor		Motorized Air Valve
	Outdoor temperature sensor		bypass
	Exhaust air temperature sensor		bypass valve
	air heater		Inlet filter
	Overheat protection thermostat		Extract filter
	Emergency thermostat		Supply air filter sensor
	Supply fan flow sensor		Extract air filter sensor
	Frost protection thermostat		Exhaust air damper
	Water valve actuator		Supply air damper
	water valve		Supply fan
	Exhaust fan

Control scheme

All components of the air handling unit must be properly integrated into the system of operation of the unit, and perform their functions in the proper amount. The task of controlling the operation of all components is solved by an automated process control system. The installation kit includes sensors, analyzing their data, the control system corrects the operation of the necessary elements. The control system allows you to smoothly and competently fulfill the goals and tasks of the air handling unit, solving complex problems of interaction between all elements of the unit.

Ventilation control panel

Despite the complexity of the process control system, the development of technology makes it possible to provide an ordinary person with a control panel from the plant in such a way that from the first touch it is clear and pleasant to use the plant throughout its service life.

Example. Heat recovery efficiency calculation:
Calculation of the efficiency of using a recuperative heat exchanger in comparison with using only an electric or only a water heater.

Consider a ventilation system with a flow rate of 500 m 3 /h. Calculations will be carried out for the heating season in Moscow. From SNiPa 23-01-99 "Construction climatology and geophysics" it is known that the duration of the period with an average daily air temperature below +8°C is 214 days, the average temperature of the period with an average daily temperature below +8°C is -3.1°C .

Calculate the required average heat output:
In order to heat the air from the street to a comfortable temperature of 20 ° C, you will need:

N = G * C p * p ( in-ha) * (t ext -t avg) = 500/3600 * 1.005 * 1.247 * = 4.021 kW

This amount of heat per unit of time can be transferred to the supply air in several ways:

1. Supply air heating by an electric heater;
2. Heating of the supply heat carrier removed through the heat exchanger, with additional heating by an electric heater;
3. Heating of outdoor air in a water heat exchanger, etc.

Calculation 1: Heat is transferred to the supply air by means of an electric heater. The cost of electricity in Moscow S=5.2 rubles/(kW*h). Ventilation works around the clock, for 214 days of the heating period, the amount of money, in this case, will be equal to:
C 1 \u003d S * 24 * N * n \u003d 5.2 * 24 * 4.021 * 214 \u003d 107,389.6 rubles / (heating period)

Calculation 2: Modern recuperators transfer heat with high efficiency. Let the recuperator heat the air by 60% of the required heat per unit time. Then the electric heater needs to spend the following amount of power:
N (electric load) \u003d Q - Q rec \u003d 4.021 - 0.6 * 4.021 \u003d 1.61 kW

Provided that the ventilation will work for the entire period of the heating period, we get the amount for electricity:
C 2 \u003d S * 24 * N (electric load) * n \u003d 5.2 * 24 * 1.61 * 214 \u003d 42,998.6 rubles / (heating period)

Calculation 3: A water heater is used to heat outdoor air. Estimated cost of heat from service hot water per 1 Gcal in Moscow:
S year \u003d 1500 rubles / gcal. Kcal=4.184 kJ

For heating, we need the following amount of heat:
Q (g.w.) \u003d N * 214 * 24 * 3600 / (4.184 * 106) \u003d 4.021 * 214 * 24 * 3600 / (4.184 * 106) \u003d 17.75 Gcal

In the operation of ventilation and heat exchanger throughout the cold period of the year, the amount of money for the heat of process water:
C 3 \u003d S (hot water) * Q (hot water) \u003d 1500 * 17.75 \u003d 26,625 rubles / (heating period)

The results of calculating the costs of supply air heating for heating
period of the year:

From the above calculations, it can be seen that the most economical option is to use the hot service water circuit. In addition, the amount of money required to heat the supply air is significantly reduced when using a recuperative heat exchanger in the supply and exhaust ventilation system compared to using an electric heater.

In conclusion, I would like to note that the use of installations with recuperation or recirculation in ventilation systems makes it possible to use the energy of the exhaust air, which makes it possible to reduce energy costs for heating the supply air, therefore, the monetary costs for the operation of the ventilation system are reduced. The use of the heat of the removed air is a modern energy-saving technology and allows you to get closer to the "smart home" model, in which any available type of energy is used to the fullest and most useful.

Comfortable suburban housing cannot be imagined without a good ventilation system, since it is they who are the key to a healthy microclimate. However, many are cautious and even wary about the implementation of such an installation, fearing huge electricity bills. If certain doubts have “settled” in your head, we recommend that you look at a recuperator for a private house.

We are talking about a small unit, combined with supply and exhaust ventilation and excluding excessive consumption of electrical energy in the winter, when the air needs additional heating. There are several ways to reduce unwanted expenses. The most effective and affordable is to make an air recuperator with your own hands.

What is this device and how does it work? This will be discussed in today's article.

Features and principle of operation

So what is heat recovery? - Recuperation is a heat exchange process in which cold air from the street is heated by the outflow from the apartment. Thanks to this organization scheme, a heat recovery installation saves heat in the house. A comfortable microclimate is formed in the apartment in a short period of time and with minimal electricity consumption.

The video below shows the air recovery system.

What is a recuperator. General concept for the layman.

The economic feasibility of a recuperative heat exchanger depends on other factors:

• energy prices;
• the cost of installing the unit;
• the costs associated with servicing the device;
• the lifetime of such a system.

note! An air recuperator for an apartment is an important, but not the only element necessary for effective ventilation in a living space. Ventilation with heat recovery is a complex system that functions exclusively under the condition of a professional "bundle".

Recuperator for home

With a decrease in ambient temperature, the efficiency of the unit decreases. Be that as it may, a heat exchanger for a house during this period is vital, since a significant temperature difference "loads" the heating system. If it is 0°C outside the window, then an air stream warmed up to +16°C is supplied to the living space. A household recuperator for an apartment copes with this task without any problems.

Formula for calculating efficiency

Modern air recuperators differ not only in efficiency, nuances of use, but also in design. Consider the most popular solutions and their features.

Main types of structures

Experts focus on the fact that there are several types of heat:

• lamellar;
• with separate heat carriers;
• rotary;
• tubular.

lamellar type of – includes a structure based on aluminum sheets. Such a heat exchanger installation is considered the most balanced in terms of the cost of materials and the value of thermal conductivity (the efficiency varies from 40 to 70%). The unit is distinguished by its simplicity of execution, affordability, and the absence of moving elements. Installation does not require specialized training. Installation without any difficulties is carried out at home, with your own hands.

plate type

Rotary are solutions that are quite popular among consumers. Their design provides for a rotation shaft powered by the mains, as well as 2 channels for air exchange with counterflows. How does such a mechanism work? - One of the sections of the rotor is heated by air, after which it turns and the heat is redirected to the cold masses concentrated in the adjacent channel.

rotary type

Despite the high efficiency, the installations have a number of significant drawbacks:

• impressive weight and size indicators;
• exactingness to regular maintenance, repair;
• it is problematic to reproduce the recuperator with your own hands, to restore its performance;
• mixing of air masses;
• dependence on electrical energy.

You can watch the video below about the types of recuperators (starting from 8-30 minutes)

Recuperator: why is it, their types and my choice

note! A ventilation unit with tubular devices, as well as separate heat carriers, is practically not reproduced at home, even if all the necessary drawings and diagrams are at hand.

DIY air exchange device

The simplest in terms of implementation and subsequent equipment is considered to be a plate-type heat recovery system. This model boasts both obvious "pluses" and annoying "minuses". If we talk about the merits of the solution, then even a home-made air recuperator for the home can provide:

• decent efficiency;
• lack of "binding" to the power grid;
• structural reliability and simplicity;
• availability of functional elements and materials;
• duration of operation.

But before you start creating a recuperator with your own hands, you should also clarify the disadvantages of this model. The main disadvantage is the formation of glaciers during severe frosts. The level of moisture in the street is less than in the air that is present in the room. If you do not act on it in any way, it turns into condensate. During frosts, high humidity levels contribute to the formation of frost.

The photo shows how air is exchanged.

There are several ways to protect the heat exchanger device from freezing. These are small solutions that differ in efficiency and implementation method:

• thermal effect on the structure due to which the ice does not linger inside the system (the efficiency drops by an average of 20%);
• mechanical removal of air masses from the plates, due to which the forced heating of the ice is carried out;
• addition of a ventilation system with a recuperator with cellulose cassettes that absorb excess moisture. They are redirected to housing, while not only condensate is eliminated, but also a humidifier effect is achieved.

We offer you to watch a video - Do-it-yourself air recuperator for home.

Recuperator - do it yourself

Recuperator - DIY 2

Experts agree that cellulose cassettes are the best solution today. They function regardless of the weather outside the window, while the installations do not consume electricity, they do not require a sewer outlet, a condensate collector.

Materials and components

What solutions and products should be prepared if it is necessary to assemble a plate-type home unit? Experts strongly recommend paying priority attention to the following materials:

1. 1. Aluminum sheets (textolite and cellular polycarbonate are quite suitable). Please note that the thinner this material is, the more efficient the heat transfer will be. Supply ventilation in this case works better.
2. 2. Wooden slats (about 10 mm wide and up to 2 mm thick). They are placed between adjacent plates.
3. 3. Mineral wool (up to 40 mm thick).
4. 4. Metal or plywood to prepare the body of the apparatus.
5. 5. Glue.
6. 6. Sealant.
7. 7. Hardware.
8. 8. Corner.
9. 9. 4 flanges (under the pipe section).
10. 10. Fan.

note! The diagonal of the body of the recuperative heat exchanger corresponds to its width. As for the height, it is adjusted for the number of plates and their thickness in conjunction with the rails.

Device drawings

Metal sheets are used to cut squares, the dimensions of each side can vary from 200 to 300 mm. In this case, it is necessary to select the optimal value, taking into account which ventilation system is installed in your home. There should be at least 70 sheets. To make them smoother, we recommend working with 2-3 pieces at the same time.

Diagram of a plastic device

In order for energy recovery in the system to be fully carried out, it is necessary to prepare wooden slats in accordance with the selected dimensions of the side of the square (from 200 to 300 mm). Then they must be carefully processed with drying oil. Each wooden element is glued to the 2nd side of the metal square. One of the squares must be left unpasted.

In order for the recovery, and with it the ventilation of the air, to be more efficient, each upper edge of the rails is carefully coated with adhesive. Individual elements are assembled into a square "sandwich". Very important! The 2nd, 3rd and all subsequent square products should be rotated 90 ° in relation to the previous one. In this way, the alternation of channels is implemented, their perpendicular position.

The upper square is fixed on the glue, on which there are no slats. Using the corners, the structure is carefully pulled together and fastened. In order for heat recovery in ventilation systems to be carried out without air loss, the gaps are filled with sealant. Flange mounts are formed.

Ventilation solutions (manufactured unit) are placed in the housing. Previously, on the walls of the device, it is necessary to prepare several corner guides. The heat exchanger is positioned in such a way that its corners rest against the side walls, while the whole structure visually resembles a rhombus.

In the photo, a homemade version of the device

Residual products in the form of condensate remain in its lower part. The main task is to obtain 2 exhaust channels isolated from each other. Inside the structure of the lamellar element, air masses are mixed, and only there. A small hole is made at the bottom to drain condensate through a hose. In the design, 4 holes are made for the flanges.

Formula for calculating power

Example! For heating the air in the room up to 21°C, which requires60 m3 of airin hour:Q \u003d 0.335x60x21 \u003d 422 W.

To determine the efficiency of the unit, it is enough to determine the temperatures at 3 key points of its entry into the system:

Calculation of recuperator payback

Now you know , what is a recuperator and how necessary it is for modern ventilation systems. These devices are increasingly being installed in country cottages, social infrastructure facilities. Recuperators for a private house are a fairly popular product in our time. At a certain level of desire, the recuperator can be assembled with your own hands from improvised means, as mentioned above in our article.

In connection with the growth of tariffs for primary energy resources, recovery becomes more relevant than ever. The following types of heat exchangers are commonly used in air handling units with heat recovery:

• plate or cross-flow heat exchanger;
• rotary heat exchanger;
• recuperators with an intermediate heat carrier;
• Heat pump;
• chamber type recuperator;
• recuperator with heat pipes.

Principle of operation

The principle of operation of any heat exchanger in air handling units is as follows. It provides heat exchange (in some models - and cold exchange, as well as moisture exchange) between the supply and exhaust air flows. The heat exchange process can take place continuously - through the walls of the heat exchanger, with the help of freon or an intermediate heat carrier. Heat exchange can also be periodic, as in a rotary and chamber heat exchanger. As a result, the extracted extract air is cooled, thereby heating the fresh supply air. The process of refrigeration in some models of recuperators takes place in the warm season and allows you to reduce energy costs for air conditioning systems due to some cooling of the supply air supplied to the room. Moisture exchange takes place between the exhaust and supply air flows, allowing you to maintain indoor humidity that is comfortable for a person all year round, without the use of any additional devices - humidifiers and others.

Plate or cross-flow heat exchanger.

The heat-conducting plates of the recuperative surface are made of thin metal (material - aluminum, copper, stainless steel) foil or ultra-thin cardboard, plastic, hygroscopic cellulose. The flow of supply and exhaust air moves through many small channels formed by these heat-conducting plates, in a counterflow pattern. Contact and mixing of streams, their pollution are practically excluded. There are no moving parts in the heat exchanger design. Efficiency ratio 50-80%. Moisture can condense on the surface of the plates in a heat exchanger made of metal foil due to the difference in temperature of the air flows. In the warm season, it must be diverted to the sewerage system of the building through a specially equipped drainage pipeline. In cold weather, there is a danger of this moisture freezing in the heat exchanger and its mechanical damage (defrosting). In addition, the formed ice greatly reduces the efficiency of the heat exchanger. Therefore, when operating in the cold season, heat exchangers with metal heat-conducting plates require periodic defrosting with a flow of warm exhaust air or the use of an additional water or electric air heater. In this case, supply air is either not supplied at all, or supplied to the room bypassing the heat exchanger through an additional valve (bypass). The defrost time is on average 5 to 25 minutes. The heat exchanger with heat-conducting plates made of ultra-thin cardboard and plastic is not subject to freezing, since moisture exchange also occurs through these materials, but it has another drawback - it cannot be used for ventilation of rooms with high humidity in order to dry them. The plate heat exchanger can be installed in the supply and exhaust system in both vertical and horizontal positions, depending on the requirements for the dimensions of the ventilation chamber. Plate heat exchangers are the most common because of their relative simplicity of design and low cost.

Rotary recuperator.

This type is the second most widespread after the lamellar. Heat from one air stream to another is transferred through a cylindrical hollow drum rotating between the exhaust and supply sections, called the rotor. The internal volume of the rotor is filled with tightly packed metal foil or wire, which plays the role of a rotating heat transfer surface. The material of the foil or wire is the same as that of the plate heat exchanger - copper, aluminum or stainless steel. The rotor has a horizontal axis of rotation of the drive shaft rotated by an electric motor with stepping or inverter regulation. The motor can be used to control the recovery process. Efficiency ratio 75-90%. The efficiency of the recuperator depends on the temperatures of the flows, their speed and the rotor speed. By changing the speed of the rotor, you can change the efficiency. Freezing of moisture in the rotor is excluded, but the mixing of flows, their mutual contamination and the transfer of odors cannot be completely excluded, since the flows are in direct contact with each other. Mixing up to 3% is possible. Rotary heat exchangers do not require large amounts of electricity, they allow you to dehumidify the air in rooms with high humidity. The design of rotary heat exchangers is more complex than plate heat exchangers, and their cost and operating costs are higher. However, air handling units with rotary heat exchangers are very popular due to their high efficiency.

Recuperators with intermediate heat carrier.

The coolant is most often water or aqueous solutions of glycols. Such a heat exchanger consists of two heat exchangers interconnected by pipelines with a circulation pump and fittings. One of the heat exchangers is placed in a channel with an exhaust air flow and receives heat from it. The heat is transferred through the heat carrier with the help of a pump and pipes to another heat exchanger located in the supply air duct. The supply air absorbs this heat and heats up. Mixing of flows in this case is completely excluded, but due to the presence of an intermediate heat carrier, the efficiency factor of this type of recuperators is relatively low and amounts to 45-55%. The efficiency can be influenced by the pump, affecting the speed of the coolant. The main advantage and difference between a heat exchanger with an intermediate heat carrier and a heat exchanger with a heat pipe is that the heat exchangers in the exhaust and supply units can be located at a distance from each other. The mounting position for heat exchangers, pump and piping can be either vertical or horizontal.

Heat pump.

Relatively recently, an interesting type of recuperator with an intermediate coolant has appeared - the so-called. thermodynamic heat exchanger, in which the role of liquid heat exchangers, pipes and a pump is played by a refrigeration machine operating in a heat pump mode. This is a kind of combination of a heat exchanger and a heat pump. It consists of two freon heat exchangers - an evaporator-air cooler and a condenser, pipelines, a thermostatic valve, a compressor and a 4-way valve. The heat exchangers are located in the supply and exhaust air ducts, the compressor is necessary to ensure the circulation of freon, and the valve switches the refrigerant flows depending on the season and allows you to transfer heat from the exhaust air to the supply air and vice versa. At the same time, the supply and exhaust system can consist of several supply and one exhaust units of higher capacity, united by one refrigeration circuit. At the same time, the capabilities of the system allow several air handling units to operate in different modes (heating / cooling) at the same time. The heat pump conversion factor COP can reach values ​​of 4.5-6.5.

Recuperator with heat pipes.

According to the principle of operation, a heat exchanger with heat pipes is similar to a heat exchanger with an intermediate heat carrier. The only difference is that not heat exchangers are placed in the air flows, but the so-called heat pipes or, more precisely, thermosyphons. Structurally, these are hermetically sealed sections of copper finned tube, filled inside with specially selected low-boiling freon. One end of the pipe in the exhaust flow heats up, the freon boils in this place and transfers the heat received from the air to the other end of the pipe, blown by the supply air flow. Here, the freon inside the pipe condenses and transfers heat to the air, which is heated. Mutual mixing of streams, their pollution and transfer of smells are completely excluded. There are no moving elements, the pipes are placed in the streams only vertically or at a slight slope, so that the freon moves inside the pipes from the cold end to the hot one due to gravity. Efficiency ratio 50-70%. An important condition for ensuring the operation of its operation: the air ducts in which the thermosyphons are installed must be located vertically one above the other.

Chamber type recuperator.

The internal volume (chamber) of such a heat exchanger is divided into two halves by a damper. The damper moves from time to time, thereby changing the direction of movement of the extract and supply air flows. The exhaust air heats one half of the chamber, then the damper directs the supply air flow here and it is heated from the heated walls of the chamber. This process is periodically repeated. The efficiency ratio reaches 70-80%. But there are moving parts in the design, and therefore there is a high probability of mutual mixing, contamination of flows and the transfer of odors.

Calculation of the efficiency of the recuperator.

In the technical characteristics of recuperative ventilation units of many manufacturers, as a rule, two values ​​​​of the recovery coefficient are given - by air temperature and its enthalpy. Calculation of the efficiency of the heat exchanger can be made by temperature or air enthalpy. The calculation by temperature takes into account the apparent heat content of the air, and by enthalpy, the moisture content of the air (its relative humidity) is also taken into account. The enthalpy calculation is considered more accurate. Initial data are required for the calculation. They are obtained by measuring the temperature and humidity of the air in three places: indoors (where the ventilation unit provides air exchange), outdoors and in the cross section of the supply air grille (from where the treated outdoor air enters the room). The formula for calculating heat recovery efficiency by temperature is as follows:

Kt = (T4 – T1) / (T2 – T1), where

• Kt– heat exchanger efficiency factor by temperature;
• T1– outdoor air temperature, oC;
• T2 is the temperature of the exhaust air (i.e. the air in the room), °C;
• T4– supply air temperature, oC.

The enthalpy of air is the heat content of air, i.e. the amount of heat contained in it, related to 1 kg of dry air. The enthalpy is determined using the i-d diagram of the state of moist air, putting on it points corresponding to the measured temperature and humidity in the room, outdoors and supply air. The formula for calculating the enthalpy recovery efficiency is as follows:

Kh = (H4 - H1) / (H2 - H1), where

• Kh– heat exchanger efficiency factor by enthalpy;
• H1– enthalpy of outside air, kJ/kg;
• H2–exhaust air enthalpy (i.e. room air), kJ/kg;
• H4– supply air enthalpy, kJ/kg.

Economic feasibility of using air handling units with recuperation.

As an example, let's take a feasibility study for the use of ventilation units with recuperation in supply and exhaust ventilation systems for car dealerships.

Initial data:

• object - a car dealership with a total area of ​​2000 m2;
• the average height of the premises is 3-6 m, it consists of two exhibition halls, an office area and a service station (SRT);
• for supply and exhaust ventilation of these premises, duct-type ventilation units were selected: 1 unit with an air flow rate of 650 m3/hour and a power consumption of 0.4 kW and 5 units with an air flow rate of 1500 m3/hour and a power consumption of 0.83 kW.
• the guaranteed range of outdoor air temperatures for duct installations is (-15…+40) °C.

To compare energy consumption, we will calculate the power of a duct electric air heater, which is necessary for heating outdoor air in the cold season in a traditional type supply unit (consisting of a check valve, a duct filter, a fan and an electric air heater) with an air flow rate of 650 and 1500 m3/h, respectively. At the same time, the cost of electricity is taken to be 5 rubles per 1 kWh.

Outside air must be heated from -15 to +20°C.

The calculation of the power of the electric air heater is made according to the heat balance equation:

Qn \u003d G * Cp * T, W, where:

• Qn– air heater power, W;
• G- mass air flow through the air heater, kg/s;
• Wed is the specific isobaric heat capacity of air. Cp = 1000kJ/kg*K;
• T- the difference between the air temperatures at the outlet of the air heater and the inlet.

T \u003d 20 - (-15) \u003d 35 ° C.

1. 650 / 3600 = 0.181 m3/s

p = 1.2 kg/m3 is the air density.

G = 0.181*1.2 = 0.217 kg/s

Qn \u003d 0, 217 * 1000 * 35 \u003d 7600 W.

2. 1500 / 3600 = 0.417 m3/s

G=0.417*1.2=0.5kg/s

Qn \u003d 0.5 * 1000 * 35 \u003d 17500 W.

Thus, the use of duct installations with heat recovery in the cold season instead of traditional ones using electric air heaters makes it possible to reduce energy costs with the same amount of air supplied by more than 20 times and thereby reduce costs and, accordingly, increase the profit of a car dealership. In addition, the use of plants with recuperation makes it possible to reduce the financial costs of the consumer for energy carriers for space heating in the cold season and for their air conditioning in the warm season by about 50%.

For greater clarity, we will make a comparative financial analysis of the energy consumption of the supply and exhaust ventilation systems of the car dealership premises, equipped with duct-type heat recovery units and traditional units with electric air heaters.

Initial data:

System 1.

Installations with heat recovery with a flow rate of 650 m3 / h - 1 unit. and 1500 m3/hour - 5 units.

The total electrical power consumption will be: 0.4 + 5 * 0.83 = 4.55 kW * h.

System 2.

Traditional duct supply and exhaust ventilation units - 1 unit. with a flow rate of 650m3/hour and 5 units. with a flow rate of 1500m3/hour.

The total electrical power of the installation at 650 m3/h will be:

• fans - 2 * 0.155 \u003d 0.31 kW * h;
• automation and valve drives - 0.1 kWh;
• electric air heater - 7.6 kWh;

Total: 8.01 kWh.

The total electric power of the installation at 1500 m3/hour will be:

• fans - 2 * 0.32 \u003d 0.64 kW * hour;
• automation and valve drives - 0.1 kWh;
• electric air heater - 17.5 kWh.

Total: (18.24 kW * h) * 5 \u003d 91.2 kW * h.

Total: 91.2 + 8.01 \u003d 99.21 kWh.

We accept the period of use of heating in ventilation systems 150 working days per year for 9 hours. We get 150 * 9 = 1350 hours.

Energy consumption of plants with recuperation will be: 4.55 * 1350 = 6142.5 kW

Operating costs will be: 5 rubles * 6142.5 kW = 30712.5 rubles. or in relative (to the total area of ​​the car dealership 2000 m2) expression 30172.5/2000 = 15.1 rubles/m2.

Energy consumption of traditional systems will be: 99.21 * 1350 = 133933.5 kW Operating costs will be: 5 rubles * 133933.5 kW = 669667.5 rubles. or in relative (to the total area of ​​the car dealership 2000 m2) expression 669667.5 / 2000 = 334.8 rubles/m2.