Ventilation heat exchanger. Heat recovery in ventilation systems: principle of operation and options. Design features, purpose

Ventilation in rooms can be natural, the principle of operation of which is based on natural phenomena (spontaneous type) or on air exchange provided by specially made holes in a buiding (organized ventilation).However, in this case, despite the minimum material costs, the dependence on the season, climate, and the lack of the ability to purify the air do not fully meet the needs of people.

Supply and exhaust ventilation, air exchange

Artificial ventilation allows you to provide more comfortable conditions for those in the premises, but its installation requires certain X financial investments. She is also quite energy-consuming . To compensate for the pros and cons of both types of ventilation systems, their combination is most often used.

Any is Artificial ventilation system according to its purpose is divided into supply or exhaust. In the first case, the equipment must provide forcedair supply to the room. At the same time, the exhaust air masses are brought out in a natural way.

Video - Supply and exhaust ventilation with recuperation in the apartment

Recuperators

Supply and exhaust ventilation is an integrated approach to the problem of ventilation.

Supply and exhaust units provide an active inflow of fresh air into the room and removal of exhaust air masses from the room. Recuperators are becoming increasingly popular, the advantage of which is the supply of fresh air heated to room temperature, with minimal annual energy consumption.

Recuperators return up to 95% of heat back to the room, practically without creating additional energy costs. Thus, recuperators are the most economical type of ventilation unit with the supply of warm air into the room. This is achieved by storing heat from the exhaust room air on heat exchangers.

The latest models of recuperators combine the functions of supply and exhaust ventilation and fine air purification from allergens, are equipped with carbon dioxide sensors, heat exchangers of a special design to maintain optimal humidity conditions, and can be controlled from a smartphone.

Installing a heat exchanger effectively helps to cope with stuffiness, humidity control in rooms, mold and dampness in the house, and condensation on plastic windows.

We are the official dealer of leading manufacturers, and we can provide a guarantee of the best price. You can choose and buy any model of the recuperator from us with delivery in Moscow and Russia.

It is well known that there are several types of ventilation systems. The most widespread is natural ventilation, when the inflow and outflow of air is carried out through ventilation shafts, open vents and windows, as well as through cracks and leaks in structures.

Of course, natural ventilation is needed, but its operation is associated with a lot of inconvenience, and it is almost impossible to achieve cost savings with its device. Yes, and you can call ventilation the movement of air through ajar windows and doors with a big stretch - most likely, it will be ordinary ventilation. To achieve the required intensity of air mass circulation, the windows must be open around the clock, which is unattainable in the cold season.

That is why a device for forced or mechanical ventilation is considered a more correct and rational approach. Sometimes it is simply impossible to do without forced ventilation, most often they resort to its device in industrial premises with degraded working conditions. Let us leave industrialists and production workers aside and turn our attention to residential buildings and apartments.

Often, in pursuit of savings, the owners of cottages, country houses or apartments invest a lot of money in warming and sealing their homes and only then realize that it is difficult to be indoors due to a lack of oxygen.

The solution to the problem is obvious - you need to arrange ventilation. The subconscious mind suggests that the best option would be an energy-saving ventilation device. The lack of properly designed ventilation can cause housing to turn into a real gas chamber. You can prevent this by choosing the most rational solution - a forced-exhaust ventilation device with heat and moisture recovery.

What is heat recovery

Recovery means its preservation. The outgoing air flow changes the temperature (heats, cools) of the supplied air by the supply and exhaust unit.

Scheme of operation of ventilation with heat recovery

The design assumes the separation of air flows to prevent their mixing. However, when using a rotary heat exchanger, the possibility of ingress of the discharged air stream into the incoming one is not excluded.

By itself, the "Air Recuperator" is a device that ensures the utilization of heat from exhaust gases. Through the separating wall between the heat carriers, heat exchange is carried out, while the direction of movement of air masses remains unchanged.

The most important characteristic of a heat exchanger is determined by the recovery efficiency or efficiency. Its calculation is determined from the ratio of the maximum possible heat recovery and the actual heat received behind the heat exchanger.

The efficiency of recuperators can vary over a wide range - from 36 to 95%. This indicator is determined by the type of recuperator used, the speed of the air flow through the heat exchanger and the temperature difference between the exhaust and incoming air.

Types of recuperators and their advantages and disadvantages

There are 5 main types of air recuperators:

lamellar;
Rotary;
With intermediate coolant;
Chamber;
Heat pipes.

lamellar

The plate heat exchanger is characterized by the presence of plastic or metal plates. The discharged and incoming flows pass on opposite sides of the heat-conducting plates without contacting each other.

On average, the efficiency of such devices is 55-75%. A positive characteristic can be considered the absence of moving parts. The disadvantages include the formation of condensate, which often leads to freezing of the recuperative device.

There are plate heat exchangers with moisture-permeable plates that ensure the absence of condensate. The efficiency and principle of operation remain unchanged, the possibility of freezing of the heat exchanger is eliminated, but at the same time, the possibility of using the device to reduce the level of humidity in the room is also excluded.

In a rotary heat exchanger, heat transfer is carried out using a rotor that rotates between the supply and exhaust ducts. This device is characterized by a high level of efficiency (70-85%) and reduced power consumption.

The disadvantages include a slight mixing of flows and, as a result, the spread of odors, a large number of complex mechanics, which complicates the maintenance process. Rotary heat exchangers are effectively used for dehumidification of premises, therefore they are ideal for installation in swimming pools.

Recuperators with intermediate heat carrier

In recuperators with an intermediate heat carrier, water or a water-glycol solution is responsible for heat transfer.

The exhaust air provides heating of the coolant, which, in turn, transfers heat to the incoming air flow. The air flows do not mix, the device is characterized by a relatively low efficiency (40-55%), usually used in industrial premises with a large area.

Chamber recuperators

A distinctive feature of chamber recuperators is the presence of a damper that divides the chamber into two parts. High efficiency (70-80%) is achieved due to the possibility of changing the direction of the air flow by moving the damper.

Disadvantages include little mixing, odor transfer, and moving parts.

Heat pipes are a whole system of tubes filled with freon, which evaporates when the temperature rises. In another part of the tubes, freon is cooled with the formation of condensate.

The advantages include the exclusion of mixing flows and the absence of moving parts. The efficiency reaches 65-70%.

It should be noted that earlier recuperative units, due to their significant dimensions, were used exclusively in production, now small-sized recuperators are presented on the construction market, which can be successfully used even in small houses and apartments.

The main advantage of recuperators is the absence of the need for air ducts. However, this factor can also be considered as a disadvantage, since sufficient separation between exhaust and supply air is required for efficient operation, otherwise fresh air is immediately drawn out of the room. The minimum allowable distance between opposite air flows should be at least 1.5-1.7 m.

Why is moisture recovery needed?

Moisture recovery is necessary to achieve a comfortable ratio of humidity and room temperature. A person feels best at a humidity level of 50-65%.

During the heating period, the already dry winter air loses even more moisture due to contact with the hot coolant, often the humidity level drops to 25-30%. With this indicator, a person not only feels discomfort, but also causes significant harm to his health.

In addition to the fact that overdried air has a negative impact on the well-being and health of a person, it also causes irreparable damage to furniture and joinery made of natural wood, as well as paintings and musical instruments. Someone may say that dry air helps to get rid of dampness and mold, but this is far from the case. Such shortcomings can be dealt with by insulating the walls and arranging high-quality supply and exhaust ventilation while maintaining a comfortable level of humidity.

Ventilation with heat and moisture recovery: scheme, types, advantages and disadvantages

What is Heat Recovery Ventilation? How does this system work, what types are there and their pros and cons.

Heat recovery ventilation

During the period of the energy crisis and the rise in the price of energy resources, the use of energy-saving technologies in all areas of management becomes especially relevant. The role of heat recuperators in this matter cannot be underestimated. Engineering installations not only significantly save gas for space heating, but also, practically free of charge, return heat back for useful use, intended for release into the atmosphere.

Air exchange operation with air heating

Supply and exhaust ventilation with heat recovery solves three main tasks:

providing the premises with fresh air;
return of thermal energy leaving with air through the ventilation system;
preventing cold streams from entering the house.

Schematically, the process can be considered with an example. The organization of air exchange is necessary even on a frosty winter day with a temperature outside the window of -22 ° C. To do this, the included supply and exhaust system, with the fan running, pumps air from the street. It seeps through the filter elements and, already cleaned, enters the heat exchanger.

As the air passes through it, it has time to warm up to + 14- + 15 ° С. Such a temperature can be considered sufficient, but does not meet sanitary standards for living. To achieve the parameters of room temperature, it is necessary to bring the air to the required values using the reheating function up to +20°C in the heat exchanger itself using a heater (water, electric) of low power - 1 or 2 kW. With such temperature indicators, air enters the rooms.

The heater operates in automatic mode: when the outside air temperature drops, it turns on and works until it warms up to the required values. At the same time, the waste stream is already heated to a “comfortable” 18 or 20 degrees. It is removed using the built-in ventilation unit, having previously passed through the heat exchange cassette. In it, he gives off heat to the oncoming cold air from the street, and only then goes into the atmosphere from the heat exchanger with a temperature of no more than 14-15 ° C.

Attention! The installation of metal-plastic structures disrupts the natural supply of fresh air flows to an apartment or house. The forced system solves the problem, supplying unheated air from the street, but also nullifying the energy saving efficiency from plastic windows. Supply and exhaust ventilation with a heat exchanger is a complex solution to the problem of heating with simultaneously functioning air exchange, an active method of saving energy.

Advantages of the supply and exhaust system with heating function

Delivers fresh air, improves indoor air quality.
Prevents loss of moisture on the surface, the formation of condensate, mold and mildew.
Eliminates the conditions for the appearance of viruses, bacteria in the room.
Saves the cost of electricity and heat energy by recovering losses from outgoing flows of about 90% of heat.
Promotes regular air exchange.
The versatility of the execution of heat exchange systems expands the scope of their application at objects of various types.
Economical use and maintenance. Maintenance, including cleaning, replacing filters, checking all components and components of the system, is carried out annually only 1 time.

Attention! The operation of recuperators in old residential buildings will be ineffective, where natural air exchange is provided by wooden window structures, cracks in wooden floors and leaks in doors. The greatest effect of heat recovery is observed in modern buildings with high-quality insulation of rooms and good tightness.

Types of heat exchangers

The most common four categories of units are distinguished:

rotary type. Works from the mains. Economical, but technically complex. The working element is a rotating rotor with metal foil applied over the entire surface. The heat exchanger with outside air passing inside reacts to the difference in temperatures outside and inside the rooms. This adjusts the speed of its rotation. The intensity of heat supply changes, icing of the heat exchanger in winter is prevented, which allows not to overdry the air. The efficiency of the devices is quite high and can reach 87%. In this case, mixing of oncoming flows (up to 3% of the total amount) and the flow of odors and pollution are possible.
plate models. They are considered the most "running" because of the democratic price and efficiency. It reaches 40-65% thanks to the aluminum heat exchanger. Due to the absence of rotating and frictional components and parts, they are considered simple in execution and reliable in operation. Air streams separated by aluminum foil do not diffuse, they pass on both sides of the heat-conducting elements. Variety: plate model with plastic heat exchanger. Its efficiency is higher, but otherwise it has the same characteristics.

Attention! Plate devices lose before rotary ones in that they freeze and dry the air. Be sure to constantly moisturize it. The optimal scope of application is the humid environment of pools.

Recycling view. Its “chip” is in its complex design and the use of a liquid carrier (water, water-glycol solution or antifreeze) as an intermediate in heat transfer. A heat exchanger is installed on the exhaust arm, which takes the heat from the outgoing air flow and heats the liquid with it. Another heat exchanger, but already at the air intake from the street, gives off heat to the incoming air without mixing with it. The efficiency of such installations reaches 65%, they do not participate in moisture exchange. It needs electricity to work.
The roof type of devices is effective (58-68%), but not suitable for home use. It is used as an integral link in the ventilation of shops, workshops and other similar premises.

Calculation of the efficiency of the heat exchanger

It is possible to roughly calculate how efficient the installed supply ventilation with heat recovery will be, both in winter and summer, when the unit is working for cooling. The formula for calculating the temperature of the supply air flow for the installation, depending on the numerical characteristic of the energy efficiency (COP), the temperature of the air outside and in the room looks like this:

Tpr \u003d (tin - tul) * Efficiency + tul,

where temperature values:

Tp - expected at the outlet of the recuperator;

tvn - indoors;

For calculations, the passport value of the efficiency of the device is taken.

As an example: at frosts of -25°C and room temperature +19°C, as well as an installation efficiency of 80% (0.8), the calculation shows that the desired air parameters after passing through the heat exchanger will be:

Tpp \u003d (19 - (-25)) * 0.8 - 25 \u003d 10.2 ° С

The calculated temperature indicator of the air after the heat exchanger was obtained. In fact, given the inevitable losses, this value will be within +8°C.

In the heat at +30°C in the yard and 22°C in the apartment, the air in the heat exchanger of the same efficiency, before entering the room, is cooled to the design temperature:

Tpr \u003d tul + (tin - tul) * Efficiency

Substituting the data, we get:

Tpr \u003d 30 + (22-30) * 0.8 \u003d 23.6 ° С

Attention! The efficiency of the installation declared by the manufacturer and the actual one will differ. The value correction is affected by air humidity, the type of heat exchanger cassette, the value of the temperature difference between outside and inside. If the heat exchanger is not properly installed and operated, the efficiency of work is also reduced.

Modern energy-saving ventilation systems with the inclusion of recuperators in them are another step towards the economical use of heat carriers. Moreover, temperature exchange installations are relevant in winter, but no less in demand in summer.

Supply and exhaust ventilation with heat recovery

How does supply and exhaust ventilation with heat recovery work. What are the benefits of supply and exhaust ventilation with a heat exchanger.

Supply and exhaust ventilation systems with heat recovery and recirculation

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 is the air flow, T is the 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.

Regenerative recuperators- 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.

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.

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 false 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 actuators - 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 exhaust 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.

Ventilation with recovery, recirculation

Design, calculation, requirements for ventilation with recovery, recirculation. Free consultation.

Features of the ventilation system with heat recovery, its principle of operation

The heat recuperator often becomes part of the ventilation system. However, not many people know what kind of device it is and what features it has. Also, an important question is whether the purchase of a recuperator will pay off, how it will change the operation of the ventilation system, whether it is possible to create such an element with your own hands. These and many other questions will be answered in the information below.

How the system works

An unusual name was given to a conventional heat exchanger. The task of the device is to take part of the heat from the already exhausted exhaust air from the room. The extracted heat is transferred to the flow, which comes from the clean air supply system. The above information determines that the purpose of using such a system is to save on heating the house. In doing so, the following points should be noted:

In the summer, the system allows you to reduce the cost of air conditioning work.
The device in question can work in both directions, that is, it takes heat in the supply and exhaust systems.

How a heat recovery system works

The above information determines that the heat exchanger is installed in many ventilation systems. It is not active, many versions do not consume energy, do not emit noise, and have an average efficiency indicator. Heat exchangers have been installed for many years, but lately many have been wondering if there is any reason to complicate the ventilation system with this device, which has quite a few problems due to working in an environment with different temperatures.

Problems installing the system

There are practically no potential problems associated with the use of such equipment. Some are decided by the manufacturer, others become a headache for the buyer. The main problems include:

Condensation formation. The laws of physics determine that when air with a high temperature passes through a cold closed environment, condensation occurs. If the ambient temperature is below zero, then the fins will begin to freeze. All information given in this paragraph determines a significant reduction in the efficiency of the device.
Energy efficiency. All ventilation systems that work together with the heat exchanger are energy dependent. The ongoing economic calculation determines that only those recuperator models that will save more energy than they spend will be useful.
Payback period. As previously noted, the device is designed to save energy. An important determining factor is how many years it takes for the purchase and installation of recuperators to pay off. If the indicator under consideration exceeds the mark of 10 years, then there is no point in installing, since during this time other elements of the system will require replacement. If the calculations show that the payback period is 20 years, then the installation of the device should not be considered.

The occurrence of condensation on the vent. system

The above problems should be taken into account when choosing a heat exchanger, which there are several dozen types.

Device options

Sidebar: Important: There are several variants of the heat exchanger. Considering the principle of operation of the device, it should be borne in mind that it depends on the type of the device itself. The plate type of the device is a device in which the supply and exhaust channels pass through a common housing. The two channels are separated by partitions. The partition consists of numerous plates, which are often made of copper or aluminum. It is important to note that the copper composition has a higher thermal conductivity than aluminum. However, aluminum is cheaper.

The features of this device include the following:

Heat is transferred from one channel to another by means of heat-conducting plates.
The principle of heat transfer determines that the problem of the appearance of condensate arises immediately after the inclusion of a heat exchanger in the system.
In order to eliminate the possibility of condensation, a thermal-type icing sensor is installed. When a signal from the sensor appears, the relay opens a special valve - the bypass.
When the valve is opened, cold air enters into two channels.

This class of device can be attributed to the low price category. This is due to the fact that when creating the structure, a primitive method of heat transfer is used. The efficiency of such a method is lower. An important point can be called the fact that the cost of the device depends on its size and the size of the supply system itself. An example is the size of the channel 400 by 200 millimeters and 600 by 300 millimeters. The difference in price will be more than 10,000 rubles.

Ventilation scheme with recuperation

The design consists of the following elements:

Two inlet air ducts: one for fresh air, the second for exhaust air.
From the coarse filter of the supplied air from the street.
Directly to the heat exchanger itself, which is located in the central part.
Damper, which is necessary to supply air in case of icing.
Condensate drain valve.
A fan that is responsible for forcing air into the system.
Two channels on the reverse side of the structure.

The dimensions of the heat exchanger depend on the power of the ventilation system and the dimensions of the air ducts.

The next type of design can be called a device with heat pipes. Its device is almost identical to the previous one. The only difference is that the design does not have a huge number of plates that penetrate the partition between the channels. For this, a heat pipe is used - a special device that transfers heat. The advantage of the system is that freon evaporates at the warmer end of the sealed copper tube. Condensation accumulates at the colder end. The features of the considered design include:

The operation of the system has the following features:

The system has a working fluid that absorbs heat energy.
Steam spreads from a warmer point to a colder point.
The laws of physics dictate that the vapor condenses back into a liquid and releases the stored temperature.
Through the wick, the water again flows to a warm point, where it is again formed into steam.

The design is sealed and works with high efficiency. The advantage is that the design is smaller and easier to operate.

The rotary type can be called a modern version. On the border between the supply and exhaust ducts there is a device that has blades - they rotate slowly. The device is designed in such a way that the plates are heated on one side and transferred from the second side by rotation. This is because the blades are angled to redirect heat. The features of the rotary system include the following:

Fairly high efficiency. As a rule, plate and tubular systems have an efficiency of no more than 50%. This is due to the fact that they do not have active elements. When redirecting the air flow, it is possible to increase the efficiency of the system up to 70-75%.
The rotation of the blades also determines the solution to the problem of condensation on the surface. The problem is also solved with low humidity in the cold season.

However, there are also several disadvantages:

As a rule, the more complex the system, the less reliable it is. The rotor system has a rotating element that can fail.
If there is high humidity in the room, then it is not recommended to use the structure.

It is also important to understand that the recuperator chambers do not have a hermetic separation. This moment determines the transfer of odor from one chamber to another. In general, the rotor system resembles a kind of fan of rather large overall dimensions with bulky blades. To improve the efficiency of the system, the device must be connected to a power source.

The intermediate type heat carrier is a classic design, which consists of water heating with convectors and pumps. The system is used extremely rarely, due to low efficiency and design complexity. However, it is practically irreplaceable in the case when the supply and exhaust ducts are at a great distance from each other. Heat is transferred through water, which has been used for many years to create such systems. To ensure the circulation of water, regardless of the location of the devices in the system, a pump is installed. It is important to understand that the design features in this case determine the low reliability of the system and the need for periodic inspections.

Features of the ventilation system with heat recovery, its principle of operation

Ventilation with heat recovery provides a comfortable and healthy microclimate in the house and heat preservation. Definition of effectiveness and implementation options.

Supply and exhaust ventilation with heat recovery: principle of operation, overview of advantages and disadvantages

The intake of fresh air during the cold period of time leads to the need to heat it to ensure the correct microclimate of the premises. To minimize energy costs, supply and exhaust ventilation with heat recovery can be used.

Understanding the principles of its operation will allow you to reduce heat losses as efficiently as possible while maintaining a sufficient volume of replaced air.

Energy saving in ventilation systems

In the autumn-spring period, when ventilating rooms, a serious problem is the large temperature difference between the incoming and inside air. The cold stream rushes down and creates an unfavorable microclimate in residential buildings, offices and factories or an unacceptable vertical temperature gradient in a warehouse.

A common solution to the problem is the integration of a heater into the supply ventilation, with the help of which the flow is heated. Such a system requires electricity, while a significant amount of warm air coming out leads to significant heat losses.

If the air inlet and outlet channels are located nearby, then it is possible to partially transfer the heat of the outgoing stream to the incoming one. This will reduce the consumption of electricity by the heater or completely abandon it. A device for ensuring heat exchange between different-temperature gas flows is called a recuperator.

In the warm season, when the outdoor air temperature is much higher than the room temperature, a heat exchanger can be used to cool the incoming flow.

Block device with recuperator

The internal structure of supply and exhaust ventilation systems with an integrated heat exchanger is quite simple, so their independent element-by-element purchase and installation is possible. In the event that assembly or self-assembly is difficult, you can purchase ready-made solutions in the form of standard monoblock or individual prefabricated structures on order.

Basic elements and their parameters

The body with heat and sound insulation is usually made of sheet steel. In the case of wall mounting, it must withstand the pressure that occurs when foaming the slots around the unit, and also prevent vibration from the operation of the fans.

In the case of a distributed intake and air flow in various rooms, an air duct system is attached to the building. It is equipped with valves and dampers for flow distribution.

In the absence of air ducts, a grill or diffuser is installed on the inlet from the side of the room to distribute the air flow. An external type air intake grille is mounted on the inlet from the side of the street to prevent birds, large insects and litter from entering the ventilation system.

Air movement is provided by two fans of axial or centrifugal types of action. In the presence of a heat exchanger, natural air circulation in sufficient volume is impossible due to the aerodynamic resistance created by this unit.

The presence of a recuperator implies the installation of fine filters at the inlet of both streams. This is necessary to reduce the intensity of dust and grease clogging of the thin channels of the heat exchanger. Otherwise, for the full functioning of the system, it will be necessary to increase the frequency of preventive maintenance.

One or several recuperators occupy the main volume of the air handling unit. They are mounted in the center of the structure.

In case of severe frosts typical for the territory and insufficient efficiency of the heat exchanger, an additional air heater can be installed to heat the outside air. Also, if necessary, install a humidifier, ionizer and other devices to create a favorable microclimate in the room.

Modern models provide for the presence of an electronic control unit. Complex modifications have the functions of programming operating modes depending on the physical parameters of the air environment. External panels have an attractive appearance, thanks to which they can fit well into any interior of the room.

Solving the problem of condensation

The cooling of the air coming from the room creates the preconditions for the unloading of moisture and the formation of condensate. In the case of a high flow rate, most of it does not have time to accumulate in the heat exchanger and goes outside. With slow air movement, a significant part of the water remains inside the device. Therefore, it is necessary to ensure the collection of moisture and its removal outside the body of the supply and exhaust system.

The output of moisture is carried out in a closed container. It is placed only indoors in order to avoid freezing of the outflow channels at sub-zero temperatures. There is no algorithm for reliable calculation of the volume of water received when using systems with a recuperator, so it is determined experimentally.

The reuse of condensate for air humidification is undesirable, since the water absorbs many pollutants such as human sweat, odors, etc.

Significantly reduce the volume of condensate and avoid the problems associated with its appearance by organizing a separate exhaust system from the bathroom and kitchen. It is in these rooms that the air has the highest humidity. If there are several exhaust systems, the air exchange between the technical and residential area must be limited by installing non-return valves.

In the case of cooling of the outgoing air flow to negative temperatures inside the heat exchanger, the condensate passes into ice, which causes a reduction in the effective cross section of the flow and, as a result, a decrease in the volume or complete cessation of ventilation.

For periodic or one-time defrosting of the heat exchanger, a bypass is installed - a bypass channel for the movement of supply air. When the flow bypasses the device, the heat transfer stops, the heat exchanger heats up and the ice passes into a liquid state. Water flows into the condensate collection tank or it evaporates to the outside.

When the flow passes through the bypass, there is no heating of the supply air through the heat exchanger. Therefore, when this mode is activated, it is necessary to automatically turn on the heater.

Features of various types of recuperators

There are several structurally different options for implementing heat transfer between cold and heated air flows. Each of them has its own distinctive features, which determine the main purpose for each type of recuperator.

Plate cross-flow heat exchanger

The design of a plate heat exchanger is based on thin-walled panels connected in turn in such a way as to alternate the passage of different temperature flows between them at an angle of 90 degrees. One of the modifications of this model is a device with finned channels for air passage. It has a higher heat transfer coefficient.

Heat exchange panels can be made of various materials:

copper, brass and aluminum-based alloys have good thermal conductivity and are not susceptible to rust;
plastics made of polymeric hydrophobic material with a high coefficient of thermal conductivity are lightweight;
hygroscopic cellulose allows condensate to penetrate through the plate and back into the room.

The disadvantage is the possibility of condensation at low temperatures. Due to the small distance between the plates, moisture or frost significantly increases the aerodynamic drag. In case of freezing, it is necessary to shut off the incoming air flow to warm up the plates.

The advantages of plate heat exchangers are as follows:

low cost;
long service life;
long period between preventive maintenance and ease of its implementation;
small dimensions and weight.

This type of heat exchanger is most common for residential and office premises. It is also used in some technological processes, for example, to optimize fuel combustion during the operation of furnaces.

Drum or rotary type

The principle of operation of a rotary heat exchanger is based on the rotation of the heat exchanger, inside which there are layers of corrugated metal with a high heat capacity. As a result of interaction with the outgoing flow, the drum sector is heated, which subsequently gives off heat to the incoming air.

The advantages of rotary recuperators are as follows:

sufficiently high efficiency compared to competing types;
the return of a large amount of moisture, which remains in the form of condensate on the drum and evaporates upon contact with the incoming dry air.

This type of heat exchanger is less commonly used for residential buildings with apartment or cottage ventilation. It is often used in large boiler houses to return heat to furnaces or for large industrial or commercial and entertainment premises.

However, this type of device has significant disadvantages:

a relatively complex design with moving parts, including an electric motor, a drum and a belt drive, which requires constant maintenance;
increased noise level.

Sometimes for devices of this type you can find the term "regenerative heat exchanger", which is more correct than "recuperator". The fact is that a small part of the outgoing air gets back due to the loose fit of the drum to the body of the structure.

This imposes additional restrictions on the possibility of using devices of this type. For example, polluted air from heating furnaces cannot be used as a heat carrier.

Tube and shell system

The tubular type heat exchanger consists of a system of thin-walled tubes of small diameter located in an insulated casing, through which outside air is supplied. A warm air mass is removed from the room through the casing, which heats the incoming flow.

The main advantages of tubular heat exchangers are as follows:

high efficiency, due to the countercurrent principle of movement of the coolant and incoming air;
simplicity of design and the absence of moving parts ensures low noise levels and a rarely occurring need for maintenance;
long service life;
the smallest section among all types of recuperation devices.

Tubes for this type of device use either light-alloy metal or, less commonly, polymer. These materials are not hygroscopic, therefore, with a significant difference in flow temperatures, intense condensate may form in the casing, which requires a constructive solution for its removal. Another disadvantage is that the metal filling has a significant weight, despite the small size.

The simplicity of the design of the tubular heat exchanger makes this type of device popular for self-manufacturing. As an external casing, plastic pipes for air ducts, insulated with polyurethane foam shells, are usually used.

Device with intermediate heat carrier

Sometimes the supply and exhaust air ducts are located at some distance from each other. This situation may arise due to the technological features of the building or sanitary requirements for reliable separation of air flows.

In this case, an intermediate heat carrier is used, which circulates between the air ducts through an insulated pipeline. As a medium for transferring thermal energy, water or a water-glycol solution is used, the circulation of which is provided by the pump.

In the event that it is possible to use another type of heat exchanger, it is better not to use a system with an intermediate heat carrier, since it has the following significant disadvantages:

low efficiency compared to other types of devices, therefore, such devices are not used for small rooms with low air flow;
significant volume and weight of the entire system;
the need for an additional electric pump for fluid circulation;
increased noise from the pump.

There is a modification of this system, when instead of forced circulation of the heat exchange fluid, a medium with a low boiling point, such as freon, is used. In this case, movement along the contour is possible in a natural way, but only if the supply air duct is located above the exhaust duct.

Such a system does not require additional energy costs, but works for heating only with a significant temperature difference. In addition, it is necessary to fine-tune the point of change in the state of aggregation of the heat exchange fluid, which can be implemented by creating the desired pressure or a certain chemical composition.

Main technical parameters

Knowing the required performance of the ventilation system and the heat exchange efficiency of the heat exchanger, it is easy to calculate the savings on air heating for a room under specific climatic conditions. By comparing the potential benefits with the costs of purchasing and maintaining the system, you can reasonably make a choice in favor of a heat exchanger or a standard heater.

Efficiency

The efficiency of a heat exchanger is understood as the efficiency of heat transfer, which is calculated using the following formula:

T p - the temperature of the incoming air inside the room;
T n - outdoor air temperature;
T in - the air temperature in the room.

The maximum value of efficiency at a nominal air flow rate and a certain temperature regime is indicated in the technical documentation of the device. His real figure will be slightly less. In the case of self-manufacturing of a plate or tube heat exchanger, in order to achieve maximum heat transfer efficiency, it is necessary to adhere to the following rules:

The best heat transfer is provided by countercurrent devices, then by cross-flow devices, and the smallest - with unidirectional movement of both flows.
The intensity of heat transfer depends on the material and thickness of the walls separating the flows, as well as on the duration of the presence of air inside the device.

where P (m 3 / hour) - air consumption.

The cost of recuperators with high efficiency is quite high, they have a complex design and large dimensions. It is sometimes possible to circumvent these problems by installing several simpler devices in such a way that the incoming air passes through them in series.

Ventilation system performance

The volume of air passed through is determined by the static pressure, which depends on the power of the fan and the main components that create aerodynamic resistance. As a rule, its exact calculation is impossible due to the complexity of the mathematical model, therefore, experimental studies are carried out for typical monoblock structures, and components are selected for individual devices.

The fan power must be selected taking into account the throughput of any type of heat exchangers installed, which is indicated in the technical documentation as the recommended flow rate or the amount of air passed by the device per unit of time. As a rule, the permissible air velocity inside the device does not exceed 2 m/s.

Otherwise, at high speeds, a sharp increase in aerodynamic resistance occurs in the narrow elements of the recuperator. This leads to unnecessary energy costs, inefficient heating of the outside air and a shortened life of the fans.

Changing the direction of the air flow creates additional aerodynamic drag. Therefore, when modeling the geometry of an indoor duct, it is desirable to minimize the number of pipe turns by 90 degrees. Diffusers to disperse air also increase resistance, so it is advisable not to use elements with a complex pattern.

Dirty filters and gratings create significant flow problems and must be cleaned or replaced periodically. One of the effective ways to assess clogging is to install sensors that monitor the pressure drop in the areas before and after the filter.

The principle of operation of a rotary and plate heat exchanger:

Measurement of the efficiency of a plate-type heat exchanger:

Domestic and industrial ventilation systems with an integrated heat exchanger have proven their energy efficiency in keeping indoor heat. Now there are many offers for the sale and installation of such devices, both in the form of ready-made and tested models, and on an individual order. You can calculate the necessary parameters and perform the installation yourself.

Supply and exhaust ventilation with heat recovery: device and operation

Supply and exhaust ventilation device with heat recovery. Types of recuperators, their advantages and disadvantages. Calculation of efficiency and nuances of ensuring the required performance.

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

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

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

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

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

Features of decentralized ventilation systems with recuperation:

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

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

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

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