The principle of recovery. Heat recovery ventilation

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 air. supply air. The process of cold exchange 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, heat exchangers with metal heat-conducting plates require, during operation in the cold season, 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 flow 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 step 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 usually water or aqueous solutions 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. 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 refrigerator operating in 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 expansion 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, combined 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.

AT technical specifications recuperative ventilation units of many manufacturers, as a rule, give two values of the recovery coefficient - 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. Enthalpy is determined with i-d diagrams of the state of humid 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, consists of two exhibition halls, an office area and a station Maintenance(ONE HUNDRED);
for the 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 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 consumer's financial costs 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 relative (to total area car dealership 2000 m2) in terms of 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.

In a house where the ventilation system works well, a person feels very comfortable and gets sick less.

However, to ensure traditional good ventilation, it is necessary to significantly increase the cost of heating and air conditioning (to maintain normal air temperature in the house).

What is an air recuperator?

Nowadays, an improved ventilation system is used with the use of special devices that can significantly reduce heat loss in winter when exhaust air is extracted and prevent heat from entering the house in summer when superheated air is supplied from the street. This device called air recuperator , photo 1.

Photo 1. Air recuperator in the ventilation system of the house

At correct installation and operation, the air recuperator is able to “return” 2/3 of the heat that leaves with the recycled air. All recuperators contain in their structure filters for cleaning the supply air and, depending on the modification, there may be a different quality of cleaning.

Advantages of using an air recuperator in a general ventilation system:

Reduces heating and ventilation costs (up to 30…50%).
Comfortable microclimate in the house, constantly fresh air.
Reduces the level of dust in the house.
Low operating costs.
Not a difficult installation.
The equipment is durable.

Air recuperator design

The air recuperator consists of two chambers that run close to each other, photo 2. Heat exchange takes place between the chambers, which allows winter time heat the supply air flow due to the heat of the exhaust flow, and vice versa in summer.

Photo 2. circuit diagram air recuperator operation

Types of recuperators

Air recuperators are of the following types.

lamellar;
rotary;
water;
roofing.

Plate heat exchanger

Plate heat exchanger represents the case in which pipes of rectangular section enter and leave. On one side, two pipes are in contact, which ensures heat exchange between them. Inside the pipes are galvanized plates that heat up, cool down and transfer heat, photo 3. In a plate heat exchanger, supply and exhaust air flows do not mix.

The plates are made of a material that has a high thermal conductivity, these include:

special plastic;
copper;
aluminum.

Photo 3. Plate air heat exchanger

Advantages of a plate air heat exchanger :

compact;
relatively inexpensive;
silent operation;
high performance of the device (efficiency is 45 ... 65%);
no electric drive and dependence on electricity;
high service life (practically do not break).

Disadvantage of plate air heat exchanger:

In winter, in frost, there is a high probability of freezing of the exhaust mechanism.
Moisture exchange is not performed.

photo 4) consists of the following main elements:

cylinder;
rotating drum (rotor);
frame.

Inside the cylinder there are many thin corrugated metal plates (heat exchangers).

Photo 4. Rotary heat exchanger

With the help of a rotating drum, the heat exchanger operates in two modes:

1 - passing the exhaust flow from the room;

2 - passing the supply air flow.

The operation of the rotary heat exchanger is controlled by its electronics, which, depending on the external and internal temperatures, determines the number of revolutions and the operating mode. Thus, the metal plates either heat up or give off heat.

The rotary heat exchanger may have one or two rotors.

Advantages of a rotary heat exchanger:

High efficiency device. The efficiency reaches up to 87%.
In winter, the device does not freeze.
Doesn't dry out the air. Partially returns moisture back to the room.

Disadvantages of a rotary heat exchanger:

Large equipment dimensions.
Dependence on electricity.

Application area:

private home;
Office rooms.
Garages.

Water recuperator

Water recuperator (recirculation) - this is a heat exchanger in which water or antifreeze serves as a heat exchanger, photo 5. This heat exchanger is similar in design to a traditional heating system. The heat exchanger fluid is heated by the outgoing air, and the supply air is heated by the heat exchanger.

Photo 5. Water recuperator

Advantages of a water recuperator:

The normal indicator of work efficiency, efficiency - 50 ... 65%.
The ability to install its individual parts in different places.

Disadvantages of a water recuperator:

Complicated design.
Moisture exchange is not possible.
Dependence on electricity.

is a recuperator industrial use. The efficiency of this type of heat exchanger is 55…68%.

This equipment is not used for private houses and apartments.

Photo 6. Roof air recuperator

Main advantages:

Low cost.
Trouble-free work.
Ease of installation.

Recuperator of own production

If you have a desire, then you can make your own air recuperator. To do this, you can carefully study the schemes of recuperators that are on the Internet and determine the main dimensions of the device.

Consider the sequence of work:

The choice of materials for the recuperator.
Production of individual elements.
Manufacturing of a heat exchanger.
Assembly of the body and its insulation.

The easiest way is to make a plate-type heat exchanger.

For the manufacture of the case, you can use the following materials:

sheet metal (steel);
plastic;
wood.

To insulate the body, you can use the following materials:

fiberglass;
mineral wool;
Styrofoam.

Konev Alexander Anatolievich

In the process of ventilation from the room, not only the exhaust air is utilized, but also part of the thermal energy. In winter, this leads to an increase in energy bills.

To reduce unjustified costs, not to the detriment of air exchange, will allow heat recovery in ventilation systems of centralized and local type. For the recovery of thermal energy are used different types heat exchangers - recuperators.

The article describes in detail the models of units, their design features principles of operation, advantages and disadvantages. The information provided will help you choose the best option for arrangement ventilation system.

Translated from Latin, recuperation means reimbursement or return receipt. With regard to heat exchange reactions, recovery is characterized as a partial return of energy expended on a technological action for the purpose of using it in the same process.

The local recuperators are provided with a fan and a plate heat exchanger. The "sleeve" of the inlet is insulated with noise-absorbing material. The control unit for compact air handling units is placed on the inner wall

Features of decentralized ventilation systems with recuperation:

efficiency – 60-96%;
low performance- devices are designed to provide air exchange in rooms up to 20-35 sq.m;
affordable price and a wide range of units, ranging from conventional wall valves to automated models with a multi-stage filtration system and the ability to adjust humidity;
ease of installation- for commissioning, no ductwork is required, you can do it yourself.
Important criteria for choosing a wall air inlet: allowable wall thickness, capacity, heat exchanger efficiency, air channel diameter and temperature of the pumped medium
Conclusions and useful video on the topic
Comparison of the operation of natural ventilation and a forced system with recuperation:

The principle of operation of a centralized heat exchanger, calculation of efficiency:

The device and operation of a decentralized heat exchanger using the Prana wall valve as an example:

About 25-35% of the heat leaves the room through the ventilation system. To reduce losses and efficient heat recovery, recuperators are used. Climatic equipment allows you to use the energy of the waste masses to heat the incoming air.
Do you have something to add, or do you have questions about the operation of various ventilation recuperators? Please leave comments on the publication, share your experience in operating such installations. The contact form is in the bottom block.

A special type of forced ventilation system is forced ventilation with heating and heat recirculation, which provides partial heating of the inlet air flow due to the warm air removed from the room using a special device - a heat exchanger. In this case, the main heating of the outside air is carried out by a conventional air heater.

Heat recovery in supply and exhaust ventilation- the phenomenon is not new, but it is still uncommon in our country. From a technical point of view, recuperation is the most common heat exchange process. The word “recovery” itself is of Latin origin and means “return of what has been spent”. Ventilation recuperators heat return part of it back to the room through heat exchange between the incoming and outgoing stream. The reverse process occurs in hot weather, when the outgoing cold conditioned air cools the oncoming warm air flow. In this case, it should be called cold recovery.

Why is recovery needed? Obviously, to save energy in the first place. The heat exchanger is a device in which the heat exchange of incoming and outgoing air masses. With normal ventilation, the temperature difference between the incoming and outgoing air in the cold and hot seasons is significant. If, for example, it is -20°C outside and +24°C indoors, then the difference is more than 40°C. This difference will need to be covered by the heating system. In summer, the difference is smaller, but it will also add a load on the air conditioner. The recuperator allows you to reduce this difference to a minimum. Properly selected equipment provides at 0°C outdoor air and +20°C indoors the difference between the incoming and outgoing flow is within 4°C, i.e. cut it five times. The recovery efficiency drops as the outside temperature drops, but the savings are still significant. Moreover, when there is a significant difference between indoor and outdoor temperatures, recovery is especially useful.

Many modern building technologies involve airtight and vapor-tight enclosing structures. For effective ventilation and removal of water vapor from rooms with sealed walls and double-glazed windows, forced supply and exhaust ventilation. Heat recovery in this case is the key to comfortable air exchange with minimal heat loss.

In the USA and Canada, long before the advent of heat recovery equipment, in order to get not too cold air into the room in winter, and too warm in summer, they came up with the idea of using a ground heat exchanger, which later became known as the “Canadian well”. his idea

It consists in the fact that, before entering the premises, the outside air passes through the supply air ducts buried in the ground, acquiring a temperature value close to + 10 ° C - a constant temperature of the soil at a depth of 2 m or more. The Canadian well, in fact, is not a recuperator, but it reduces energy costs for heating and air conditioning. Ventilation of rooms in traditional pattern with a Canadian well, natural, but may be forced.

Recuperators as an element of ventilation equipment are actively used in European countries. The reason for their popularity is the economic benefits provided by the return of heat. There are two types of recuperators: plate and rotary. Rotary ones are more efficient, but also more expensive. They are able to return 70-90% of heat. Lamellar ones are cheaper, but they save less, within 50-80%.

One of the factors affecting the efficiency of recovery is the type of room. If the temperature in it is maintained above 23°C, then the heat exchanger definitely pays for itself. And the more expensive the cost of energy, the shorter the payback period. The service life of recuperators is quite long, and with timely maintenance and replacement of inexpensive consumables, it is theoretically unlimited. Recuperators can be supplied as a monoblock or several separate modules.

The heat exchanger is a special type of heat exchanger, to which the inlets and outlets of the supply and exhaust channels of the ventilation system are connected. The polluted air removed from the room, passing through the heat exchanger, gives off its heat to the incoming outside air, without directly mixing with it. Such additional heating of supply ventilation can significantly reduce energy costs for heating the inlet air, especially in winter.

Plate heat exchangers

Plate heat exchangers are designed in such a way that the air flows in them do not mix, but contact each other through the walls of the heat exchange cassette. This cassette consists of many plates that separate cold air from warm air. Most often, the plates are made of aluminum foil, which has excellent heat-conducting properties. Plates can also be made of special plastic. These are more expensive than aluminum, but increase the efficiency of the equipment.

Plate heat exchangers have a significant drawback: as a result of the temperature difference, condensate forms on cold surfaces, which turns into ice. An ice-covered heat exchanger stops working efficiently. To defrost it, the incoming flow is automatically transferred to bypass the heat exchanger and is heated by a heater. The outgoing warm air, meanwhile, melts the frost on the plates. In this mode, of course, there is no energy saving, and the defrost period can take from 5 to 25 minutes per hour. To heat the incoming air during the defrosting phase, heaters with a power of 1-5 kW are used.

Some plate heat exchangers preheat the incoming air to a temperature that prevents ice formation. This reduces the efficiency of the heat exchanger by about 20%.

Another solution to the icing problem is hygroscopic cellulose cassettes. This material absorbs moisture from the exhaust air stream and transfers it to the incoming one, thereby returning moisture back. Such recuperators are justified only in buildings where there is no problem of waterlogging. The absolute advantage of hygrocellulose recuperators is that they do not need electric air heating, which means that they are more economical. For recuperators with a double plate heat exchanger, the efficiency reaches 90%. Ice does not form in them, due to the transfer of heat through the intermediate zone.

Well-known manufacturers of plate heat exchangers:

SCHRAG (Germany),
MITSUBISHI (Japan),
ELECTROLUX,
SYSTEMAIR (Sweden),
SHUFT (Denmark),
REMAK, 2W (Czech Republic),
MIDEA (China).

Rotary heat exchangers

Unlike lamellar ones, in them there is a partial mixing of incoming and outgoing air. Their main element is a rotor mounted in the body, which is a cylinder filled with layers profiled metal (aluminum, steel). Heat transfer occurs during the rotation of the rotor, the blades of which are heated by the outgoing flow and give off heat to the incoming flow, moving in a circle. The heat transfer efficiency depends on the rotor speed and is adjustable.

In a rotary heat exchanger, it is technically impossible to completely eliminate the mixing of incoming and outgoing air. In addition, this type of equipment, due to the presence of moving parts, needs more frequent and more serious maintenance. Nevertheless, rotary models are quite popular due to their high heat recovery rates (up to 90%).

Manufacturers of rotary heat exchangers:

DAIKIN (Japan),
KLINGENBURG (Germany),
SHUFT (Denmark),
SYSTEMAIR (Sweden),
REMAK (Czech Republic),
GENERAL CLIMATE (Russia-Great Britain).

From an economic point of view, heat recuperators will sooner or later justify themselves, but much depends on how efficiently the recovery itself will be organized. The equipment is highly reliable, and the consumer can count on a long period of operation. Many companies produce a wide range of supply heat exchangers designed specifically for apartments. So a supply unit with heat recovery for a 2-3-room apartment can cost about 17,000 rubles. The performance of the ventilation system in apartments is in the range of 100-800 m³ / h. For country cottages, this figure is about 1000-2000 m³ / h.

Recuperators with intermediate heat carrier

This heat exchanger consists of two parts. One part is located in the exhaust duct, the other in the supply duct. Water or a water-glycol solution circulates between them. The exhaust air heats the coolant, which, in turn, transfers heat to the supply air. In this heat exchanger, there is no risk of transferring contaminants from the exhaust air to the supply air. Changing the circulation rate of the coolant can control the heat transfer. These recuperators have no moving parts, but they have low efficiency (45-60%). Mainly used for industrial facilities.

Chamber recuperators

The shutter divides the chamber into two parts by a shutter. One part is heated by the exhaust air, then the damper changes the direction of the air flow. Due to this, the supply air is heated from the warm walls of the chamber. Pollution and odors can be transferred from the exhaust air to the supply air. The damper is the only moving part of this heat exchanger. Its efficiency is quite high (70-80%).

heat pipes

This heat exchanger consists of a sealed tube system. They are filled freon or other easily evaporating component. These substances evaporate from heating by the removed air. Vapors condense in another part of the tube and again turn into a liquid state. In this heat exchanger, the transfer of contaminants is excluded, there are no moving parts, the efficiency is quite low (50-70%).

Many people think that RECUPERATORS are expensive, bulky devices with a short service life that are difficult to integrate into technological processes, and their repair stops production for a long period, making the use of a heat exchanger ineffective. These shortcomings allow skeptics to put up with colossal losses of thermal energy and environmental issues. As a result, recuperators are far from being installed at all enterprises, where it is expedient.

The solution may be to install ribbed Plate Heat Exchangers(recuperators type OPT™)

Technical features of OPT type recuperators

reduce the cost of its purchase by up to 40% due to the return of thermal energy;
reduce fuel consumption by increasing the combustion temperature of exhaust gases (heating scheme for boiler houses, furnaces, etc.);
improve quality characteristics combustion of fuel through the use of previously heated air, to reduce the mechanical underburning of fuel in the furnace heating cycle in boiler houses and other facilities;
cool flue gases to comply with environmental requirements and sanitary standards;
use the heat of waste gases for space heating, heating the outdoor air;
for technological processes requiring low temperatures, cool down flue gases;
reduce temperature flue gases, thereby reducing the cost of gas cleaning;
replace recuperators that require complex repairs with more reliable ones;
successfully comply with the requirements of Law No. 261 FZ “On Energy Saving”;

Advantages of Finned Plate Heat Exchangers over traditional plate, rotary and shell-and-tube models

the possibility of using in aggressive and abrasive environments, in environments with strong gas contamination and dusting;
increased operating temperature limits - up to 1250 C, while the service life of analog recuperators is reduced already at 800 C;
optimized dimensions and weight - 4-8 times lighter than analog recuperators;
significantly lower cost;
shortened payback periods;
low indicators of resistance during the passage of air flows along the tracts;
improved design preventing accumulation of slags;
extended service life;
an extended working period before preventive measures;
improved weight and size characteristics, facilitating the installation and transportation of recuperators

Why this type of heat exchanger can be considered a competent choice?

increase in the heat transfer surface area per unit volume and mass;
high reliability of the heat exchanger used;
a significant reduction in the possibility of a heat exchanger failure due to abrasive wear and thermal deformations;
simplification of the processes of repair and maintenance of recuperators;
Possibility of modular design and assembly of recuperators
The most common cases of using a recuperator.

Gas-gas heat exchangers are used in many areas, which can be divided into the following categories:

Processes with a low coolant temperature:

Interval 20 to 60°C

with small volumes of gases, for example, as a flue gas utilizer when operating gas boilers in a small room, where the heat exchanger is used in the ventilation system.
with large volumes of gases, for example, in the ventilation system of workshops, concert halls, indoor stadiums and other large rooms.

Range 60 to 200°C

at small volumes of gases, for example, to remove the flue product of fuel combustion, which is released as a gas during a variety of technological processes.
with large volumes of gases, for example, the use of a gas heat exchanger is possible in the ventilation system of drying and painting shops.

Processes with an average level of coolant temperature.

The range is from 200 to 600°C, an example is the utilization of flue gas heat during the operation of boiler houses, and it is also possible to save coal by redirecting excess heat to warm the air supplied to the furnace.

Processes with a high level of coolant temperature.

The range is from 600 to 800°C, for example in the plastics industry, a heat exchanger can be useful for cooling gas or for recovering heat carried by flue gases.
The range is up to 1000°C and above, which are observed in the production of glass, in metallurgy, oil and gas processing and other areas of production, where the heat exchanger will become the basis for solving such a problem as saving coal, or act as a utilizer of the resulting flue gases.

It should be noted that the use of a gas-gas heat exchanger at a flue gas temperature of 45-50°C requires a separate efficiency calculation.

conclusions

Installations with heat recovery can reduce energy costs for space heating by half. Installing them often pays for itself on the first day. heating season. The installation of recuperators during construction and reconstruction makes it possible to partially reduce the load on the heating system of the entire building and to abandon a significant part of traditional heating equipment. The cost of installing recuperators is an investment not only in reducing heating costs, but also in ensuring optimal climatic conditions indoors and ultimately to human health.

Appliances capable of saving heat and other forms of energy are becoming more and more important as energy prices are constantly rising. Also, we have long had no doubt about the need to breathe fresh clean indoor air. A negative role in the construction was played by the installation of popular plastic windows and sealed doors. They disrupt air exchange and lead to undesirable consequences. Against the background of all these factors, ventilation systems with heat recovery come to our aid. They not only save us money, but also protect our health.

Everyone knows that there is a huge variety of systems for ventilation of the room. The simplest of them are open-type systems (natural), for example, using a window or a window.

But this method of ventilation is absolutely not economical. In addition, for effective ventilation, you need to have a constantly open window or the presence of a draft. Therefore, this type of ventilation will be extremely inefficient. Supply ventilation with heat recovery is increasingly used for ventilation of residential premises.

In simple words, recovery is identical to the word "preservation". Heat recovery is the process of storing thermal energy. This is due to the fact that the flow of air that leaves the room cools or heats the air entering inside. Schematically, the recovery process can be represented as follows:

The ventilation with heat recovery takes place according to the principle that the flows must be separated by the design features of the heat exchanger in order to avoid mixing. However, for example, rotary heat exchangers do not make it possible to completely isolate the supply air from the exhaust air.

The percentage of efficiency of the heat exchanger can vary from 30 to 90%. For special installations, this figure can be 96% energy savings.

What is an air recuperator

By its design, an air-to-air heat exchanger is a unit for heat recovery of the output air mass, which allows the most efficient use of heat or cold.

Why choose heat recovery ventilation

Ventilation, which is based on heat recovery, has a very high efficiency. This indicator is calculated by the ratio of the heat that the heat exchanger actually produces to the maximum amount of heat that can only be stored.

What are the types of air recuperators

To date, ventilation with heat recovery can be carried out by five types of recuperators:

Plate, which has metal structure and has high level moisture permeability;
Rotary;
chamber type;
Recuperator with an intermediate heat carrier;
Heat pipes.

Ventilation of a house with heat recovery using the first type of heat exchangers allows incoming air flows from all sides to flow around a lot of metal plates with increased thermal conductivity. The efficiency of recuperators of this type ranges from 50 to 75%.

Features of the device of plate heat exchangers

Air masses do not contact;
All details are fixed;
No moving structural elements;
Does not form condensate;
Cannot be used as a room dehumidifier.

Features of rotary heat exchangers

The rotary type of recuperators has design features, with the help of which heat transfer occurs between the supply and output channels of the rotor.

Rotary heat exchangers are covered with foil.

Efficiency up to 85%;
Saves electricity;
Let's apply to dehumidification of the room;
Mixing up to 3% of air from different streams, in connection with which odors can be transmitted;
Complex mechanical design.

Supply and exhaust ventilation with heat recovery, based on chamber recuperators, is used extremely rarely, as it has many disadvantages:

Efficiency up to 80%;
Mixing of oncoming flows, in connection with which the transmission of odors increases;
moving parts of the structure.

Recuperators based on an intermediate heat carrier have a water-glycol solution in their design. Sometimes ordinary water can act as such a coolant.

Features of recuperators with an intermediate heat carrier

Extremely low rate Efficiency up to 55%;
Mixing of air streams is completely excluded;
Scope of application - large-scale production.

Heat recovery ventilation based on heat pipes often consists of an extensive system of tubes that contain freon. Liquid evaporates when heated. In the opposite part of the heat exchanger, freon cools down, as a result of which condensate often forms.

Features of recuperators with heat pipes

No moving parts;
The possibility of air pollution by odors is completely excluded;
The average efficiency index is from 50 to 70%.

Currently issued compact units for air mass recovery. One of the main advantages of mobile heat exchangers is the absence of the need for air ducts.

Main objectives of heat recovery

Ventilation based on heat recovery is used to maintain the required level of humidity and temperature indoors.
For skin health. Surprisingly, heat recovery systems have a positive effect on human skin, which is constantly moisturized and the risk of drying out is minimized.
To avoid drying out furniture and creaking floors.
To increase the likelihood of static electricity. Not everyone knows these criteria, but with increased static voltage, mold and fungi develop much more slowly.

Properly selected supply and exhaust ventilation with heat recovery for your home will allow you to significantly save on heating in the winter and air conditioning in the summer. In addition, this type of ventilation has a positive effect on human body, from which you will be less sick, and the risk of fungus in the house will be minimized.