Air recuperation theory and types of recuperators. Recovery in ventilation systems

Rename the theme. It does not pull at the educational program at all. Pulls only for PR.
Now I will correct it a little.
Advantages of a rotary recuperator:
1. High efficiency of heat transfer
Yes, I agree. The highest efficiency among household ventilation systems.
2. Dries the air in the room, as it is not hygroscopic.
No one specifically uses a rotor for dehumidification. Why is this credited to the pros?
Minuses:
1. Large sizes.
I disagree.
2. The rotor is a complex moving mechanism that is subject to wear and tear, which will increase operating costs.
A small stepper motor that turns a rotor costs 3 kopecks and rarely fails. You call it a "complex moving mechanism" that increases operating costs?
3. Air flows are in contact, due to which the admixture is up to 20%, according to some reports, up to 30%.
Who Said 30? Where did you get it? Please show us the link. I can still believe 10 percent of the flow, but 30 is nonsense. Some plate recuperators are far from tight in this regard and a small overflow there is in the order of things.
4. Condensate drainage required
Dear educationalist, read at least one instruction manual for the rotary unit for apartments and cottages. It says in black and white: with standard air humidity, condensate drainage is not required.
5. Fastening the PVU in one position.
Why is this a minus?
6. Dries the air in the room, as it is not hygroscopic.
If you know the ventilation system market, you have already paid attention to the development of rotors made of hygroscopic material. The question of how much this is necessary and how much all this hygroscopy is needed, including in plate-type recuperators, is a rather controversial issue and often not in favor of hygroscopicity.
Thanks for the answer.
Nobody even claimed to have an educational program. A topic for discussion and possible help for the user, as well as for me as a user.
"Since I am a slightly interested person, I will compare with what I work with." - I wrote at the very beginning. I compare it with what I work with.
The rotor has larger dimensions than the lamellar. Since I compare it with what I work with.
The fact that it has the highest efficiency rates, in my opinion, is not true, for the triple plate they are higher and the frost resistance is Higher. Again, I compare it with what I work with.
It is a moving mechanism and is subject to wear and tear, so that it costs three pennies. It's good.
Fastening in one position is a minus. It is not always possible to deliver exactly as shown in the diagram.
Hygroscopy is needed to reduce the operating temperature at which the recuperator will not freeze up.

Heat recovery has recently become quite common in ventilation systems. If we consider in more detail the process itself, then first you need to decide and understand what the term recuperation itself means. Heat recovery in ventilation systems means that the transmitted air, which is removed by special units, is passed through the filter system and fed back.

It is worth paying special attention to the fact that in ventilation systems with a share of exhaust air, part of the heat is also extracted from the room. And it is this heat energy that is returned back.

These systems are effectively used in large factories and in large workshops, since in order to ensure the optimal temperature for such premises in winter, you need to expose yourself to great costs. These installations can significantly compensate for such losses and reduce costs.

Even in a private house, ventilation systems with heat recovery will be quite relevant today. Even in an individual house, ventilation is always carried out and when the air circulates, heat is also removed from any room in the same way. Agree that it is simply impossible to completely seal the building and thereby avoid any heat loss.

Today, these systems should be used even in a private house for the following reasons:

For quick removal of air with a large admixture of carbon dioxide;
For the flow of the required amount of fresh air into the living quarters;
To eliminate high humidity in rooms, as well as eliminate unpleasant odors;
To save heat;
And also to remove dust and harmful microorganisms that may be contained in it.

Supply type systems with recuperation

The air handling unit with heat recovery is becoming more and more popular among private homeowners. And its advantages, especially during the cold season, are very high.

As you know, there are many ways to provide a living space with the necessary ventilation. This is the natural circulation of air, which is mainly carried out by airing the rooms. But you must admit that it is simply impossible to use this method in winter, since all the heat will quickly leave the living quarters.

If in a house in which air circulation is carried out only in a natural way there is no more efficient system, then it turns out that in the cold the rooms do not receive the required volume of fresh air and oxygen, respectively, which further negatively affects the well-being of all family members.

Of course, lately, when almost all owners are installing plastic windows and doors, it turns out that it is simply ineffective to arrange ventilation in a natural way. Therefore, it becomes necessary to install additional equipment that can ensure good air circulation inside the premises. And, of course, every owner would agree that they would like any system to be energy efficient.

And here the best option would be heat recovery in ventilation systems. Ideally, it is desirable to purchase a unit that could provide moisture recovery as well.

What is moisture recovery?

In any room, a certain level of humidity should always be maintained at which each person feels most comfortable. This rate ranges from 45 to 65%. In winter, most people are faced with excessively dry indoor air. Especially in apartments, when the heating is turned on at full and the air becomes very dry with a humidity of about 25%.

In addition, it often turns out that not only a person suffers with such fluctuations in humidity. But also floors with furniture, as you know, wood has a high hygroscopicity. Very often furniture and floors dry out from too dry air, and in the future it turns out that the floors begin to creak and the furniture to fall apart. These installations will primarily maintain the required level of humidity in any room, regardless of the season.

Types of recuperators

In individual residential buildings, ventilation systems are most often installed with centralized heat exchangers. In addition, today you can choose from several types of recuperative ventilation designs, but the following are in higher demand:

Lamellar.
Rotary.
Chamber.
Having an intermediate heat carrier.

Plate heat exchangers

The simplest designs for ventilation systems. The heat exchanger is made in the form of a chamber, divided into separate channels located parallel to each other. Between them is a thin plate-like baffle, which has high heat-conducting properties.

The principle of operation is based on the exchange of heat of air flows, that is, the exhaust air that is removed from the room and gives up its heat to the supply air, which enters the house already warm, thanks to this exchange.

The advantages of this technology include:

simple device configuration;
complete absence of any moving parts;
high efficiency of action.

Well, one of the most significant drawbacks in the operation of such a recuperator is the formation of condensate on the plate itself. Typically, such heat exchangers need to be additionally installed with special droplet separators. This is a necessary parameter, because in winter the condensate can freeze and stop the device. That is why some devices of this type have built-in defrosting systems.

Rotary heat exchangers

Here the main part is taken over by the rotor, which is located between the air ducts and heats the air by means of constant rotation. Rotary type heat recovery ventilation has a very high working efficiency. Such a system allows you to return about 80% of the heat back to the room.

But a significant drawback is the inferiority of the system in relation to dirt, dust and odors. There are no densities in the design between the rotor and the housing. Because of them, air flows can mix and therefore all contaminants can return back. And naturally, the noise level here is an order of magnitude higher than that of a plate heat exchanger.

Chamber type heat exchangers

In this type of recuperator, the air flows are separated directly by the chamber itself. Heat exchange takes place thanks to the damper, which periodically changes the direction of the air flows. This system is highly efficient in operation. And the disadvantages include only the presence of moving parts inside the device.

Intermediate carrier heat exchangers

The principle of operation of this device is practically similar to that of a plate recuperator. Here the heat exchanger is a closed loop made of a tube. It is constantly circulating water or water-glycol solution. The efficiency of heat transfer processes directly depends on the circulation rate in a closed fluid circuit.

In such a device, mixing of air flows is completely excluded. The only disadvantage is insufficient efficiency. Such a device is capable of returning about 50% of the heat taken from the room.

Heat pipes

It is worth highlighting one more type of recuperators. Heat recovery in a home using heat pipes is quite effective. Such devices are sealed tubes made of a metal that has high heat-conducting properties. Inside such a tube there is a liquid that has a very low boiling point (freon is usually used here).

Such a heat exchanger is always installed in a vertical position, with one of its ends located in the exhaust duct and the other in the supply duct.

The principle of operation is simple. The extracted warm air, washing the pipe, transfers heat to freon, which, boiling, moves upward, with a large amount of heat. And the supply air that washes the top of the tube takes this heat with it.

The advantages include high efficiency, quiet operation and high efficiency. So today you can significantly save on heating your home, partially returning it back.

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

However, in order to provide 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, they use an improved ventilation system with the use of special devices that can significantly reduce heat loss in winter when exhausting exhaust air and prevent heat into the house in summer when overheated air is supplied from the street. This device is called air recuperator , photo 1.

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

If installed and operated correctly, the air recuperator is capable of “recovering” 2/3 of the heat that goes away with the processed air. All recuperators contain in their structure filters for cleaning the supply air and, depending on the modification, there can be different cleaning quality.

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.
Easy 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 heating the supply air flow in winter due to the heat of the exhaust flow, and vice versa in summer.

Photo 2. Schematic diagram of the air recuperator operation

Types of recuperators

Air recuperators are of the following types.

lamellar;
rotary;
aquatic;
roofing.

Plate recuperator

Plate recuperator is a body, into which pipes of rectangular cross-section enter and exit. On one side, two pipes are in contact, which ensures heat exchange between them. Inside the pipes there are galvanized plates that heat up, cool down and transfer heat, photo 3... In a plate heat exchanger, the supply and extract 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 recuperator

Advantages of the plate air recuperator :

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

Lack of plate air recuperator:

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

photo 4) consists of the following basic elements:

cylinder;
rotating drum (rotor);
frame.

A plurality of thin corrugated metal plates (heat exchangers) are installed inside the cylinder.

Photo 4. Rotary recuperator

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

1 - passing the exhaust flow from the room;

2 - passing the supply air flow.

The operation of the rotary recuperator 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 recuperator can have one or two rotors.

The advantages of a rotary recuperator:

High efficiency of the device. The efficiency reaches up to 87%.
The device does not freeze in winter.
Does not dry the air. Partially returns moisture back to the room.

Disadvantages of a rotary recuperator:

Large dimensions of the equipment.
Dependence on electricity.

Application area:

Private home;
Office rooms.
Garages.

Water recuperator

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

Photo 5. Water recuperator

Advantages of a water recuperator:

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

Disadvantages of a water recuperator:

Complex construction.
Moisture exchange is not possible.
Dependence on electricity.

Is a recuperator for industrial use. The efficiency of this type of recuperator 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.
Easy to install.

Self-made recuperator

If you have a desire, you can also make an air recuperator yourself. 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:

Selection of materials for the recuperator.
Manufacturing of individual elements.
Heat exchanger manufacturing.
Assembly of the case and its insulation.

The easiest way to make a plate-type recuperator.

The following materials can be used for the manufacture of the case:

sheet metal (steel);
plastic;
wood.

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

fiberglass;
mineral wool;
Styrofoam.

Alexander A. Konev

When operating ventilation systems in residential buildings or industrial premises, in order to save money spent, it is necessary at the design stages to provide for the installation of energy-saving equipment called supply and exhaust ventilation systems using heat recovery processes.

The device itself, called "recuperator", is a specific type of heat exchanger, consisting of double walls that allow both cold supply and exhaust warm air to pass through. The main characteristics of recuperators include its efficiency, which in most cases depends on some important parameters:

the metal composition of the heat exchanger structure;
the total area of contact with air currents;
the ratio of the volume of the passed air masses (supply to exhaust).

In general, the differences between ventilation heat exchangers are also determined by many other factors that go into specific types of recuperators.

Species classification of recuperators

Air recuperators are often equipped not only with a heat exchanger, but also with two fans for separate removal of clean and exhaust air. In addition, these devices can include various technical devices in order to improve the quality of the supplied air. Based on this, heat exchangers are classified according to the heat carrier used, design or flow pattern of heat carriers into the following types:

The plate recuperator (also called cross-point) is the most popular type of heat exchanger due to its compact design simplicity, relatively low cost and reliability. This type of equipment consists of a set of cassettes, separated by channels of supply and exhaust air flows, made of galvanized metal. The efficiency of these devices can reach an average of 70%. and do not need to use electrical energy. The main advantages of such ventilation units include:

increased efficiency (performance level);
lack of consumers of electrical energy;
convenient and simple installation;
noiselessness of work.

Their main disadvantage is the possible freezing of the heat exchanger as a result of the formation of excessive condensate on the plates. To eliminate this disadvantage as much as possible, the household recuperator is equipped with outlets for collecting condensate liquid (condensate collectors). The only exceptions are cellulose heat exchangers.

A plate recuperator, the principle of operation of which is quite convenient and simple, and is based on the intersection of two streams of air masses (supply and exhaust) in the heat exchanger without mixing, has sufficient efficiency due to the efficiency indicator, measured as a percentage, and can correspond to the following values:

45-78% - when using plastic or metal heat exchangers;
60-92% - when using plate heat exchangers with a cellulose hygroscopic heat exchanger.

The lamellar duct recuperator can be used in rooms where high requirements and standards are imposed on the purity of the incoming air. For the device of the ventilation system, you can purchase both a ready-made device and manufacture.

On the basis of plate air handling units, there is also a membrane recuperator, which allows simultaneous moisture and heat exchange in order to eliminate the need to create an additional drainage system to remove excess condensate. Membrane plates have selective permeability, in connection with which they allow water molecules to pass through and retain gas molecules.

A rotary recuperator, the principle of which is based on the rotation of a rotary heat exchanger at a certain and constant speed, is a cylindrical structure, inside which layers of corrugated metal are densely located. The built-in drum, making rotational movements, initially passes the heated air, after which the supply cold air. As a result, the corrugated layers are progressively cooled or heated and part of the heat is transferred to the cold air flow. Such ventilation units have a number of advantages, among which are:
- partial return of moisture (no need for);
- the ability to control the speed of rotation of the rotors;
- compact design and installation.
Along with the advantages, rotary heat exchangers have significant disadvantages - they require the use of electricity, the installation of additional filtering components and have moving elements.

The efficiency of a rotary recuperator can be 60-85%, therefore they are used in systems characterized by high air flow rates.
The glycol recuperator is one of the range of intermediate heat transfer systems that allows two separate ventilation systems to be connected. This equipment is ideal for modernizing existing ventilation systems operating separately from each other. The basic characteristics of such installations include:
- the ability to adjust the system using built-in automation and the rate of circulation of the coolant;
- operation of the unit at subzero temperatures without the need for defrosting;
- connection of several tributaries and one exhaust hood or vice versa;
- lack of moving parts;
- the gap between the air outlet and the inflow can be up to 800m.
The main disadvantage is low work efficiency - 45-60%.
Water recuperator is a type of air recuperators used in supply and exhaust systems. The mechanism of action of such a device is due to the transfer of heat through water. In this case, the heat exchangers can be located at a remote distance using thermally insulated pipelines. This circumstance is the main purpose of the application - the connection of ventilation lines. Water recuperators are used quite rarely due to low efficiency values and the need for frequent maintenance.

The main criteria for the selection of recuperators

When selecting a suitable and optimal recuperator in terms of efficiency, it is necessary to adhere to the following criteria:

the level of recuperation (energy saving) - depending on the manufacturer and model, this parameter should be in the range of 40-85%;
sanitary and hygienic indicators - the ability to control the degree of purification and quality of incoming air;
energy efficiency - the value of energy consumption;
performance characteristics - total service life, equipment suitability for repair work, the need for minimum service;
adequate cost.

Considering all these indicators, choosing the most high-quality and efficient types of recuperators will not be difficult for those wishing to both create and improve the existing ventilation system.