Plate recuperator. Air conditioners with mixed air Recuperator and air conditioner in one apartment

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

Understanding the principles of its operation will allow you to most effectively reduce heat loss while maintaining a sufficient volume of replaced air. Let's try to understand this issue.

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

A common solution to the problem is integration into supply ventilation, with the help of which the flow is heated. Such a system requires energy consumption, while a significant volume of warm air escaping outside leads to significant heat losses.

The exit of air to the outside with intense steam serves as an indicator of significant heat loss, which can be used to heat the incoming flow

If the air inlet and outlet channels are located nearby, then it is possible to partially transfer the heat of the outgoing flow to the incoming one. This will reduce the energy consumption of the heater or eliminate it altogether. A device for ensuring heat exchange between gas flows of different temperatures is called a recuperator.

In the warm season, when the outside air temperature is significantly higher than room temperature, a recuperator can be used to cool the incoming flow.

Design of a unit with a recuperator

Internal structure of systems supply and exhaust ventilation s are quite simple, so it is possible to purchase and install them independently element by element. In the event that the assembly or self-installation causes difficulties can be purchased ready-made solutions in the form of standard monoblock or individual prefabricated structures to order.

An elementary device for collecting and discharging condensate is a tray located under the heat exchanger with a slope towards the drain hole

Moisture is removed into a closed container. It is placed only indoors to avoid freezing of the outflow channels when 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.

Reusing condensate for air humidification is undesirable, since water absorbs many pollutants such as human sweat, odors, etc.

You can significantly reduce the volume of condensate and avoid problems associated with its occurrence 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 areas must be limited by installing check valves.

If the exhaust air flow is cooled to negative temperatures Inside the recuperator, condensate turns into ice, which causes a reduction in the open cross-section of the flow and, as a consequence, a decrease in volume or a complete cessation of ventilation.

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

The principle of the bypass device is simple, therefore, if there is a risk of ice formation, it is advisable to provide such a solution, since heating the recuperator by other means is complex and time-consuming

When the flow passes through the bypass, there is no heating of the supply air through the recuperator. Therefore, when activating this mode, it is necessary automatic switching on heater.

Features of various types of recuperators

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

The design of the plate recuperator is based on thin-walled panels, connected alternately in such a way as to alternate the passage of flows of different temperatures 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.

Alternate passage of warm and cold air flow through the plates is realized by bending the edges of the plates and sealing the joints with polyester resin

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;
• plastic made from a hydrophobic polymer material with a high thermal conductivity coefficient and low weight;
• hygroscopic cellulose allows condensation to penetrate through the plate and back into the room.

The disadvantage is the possibility of condensation forming when low temperatures. Due to the small distance between the plates, moisture or ice significantly increases aerodynamic drag. In case of freezing, it is necessary to block the incoming air flow to warm the plates.

The advantages of plate recuperators 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 recuperator is most common for residential and office premises. It is also used in some technological processes, for example, to optimize fuel combustion during furnace operation.

Drum or rotary type

The operating principle of a rotary recuperator is based on the rotation of a heat exchanger, inside of which there are layers of corrugated metal with 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 fine-mesh heat exchanger of a rotary recuperator is susceptible to clogging, so you need to pay special attention to the quality operation of fine filters

The advantages of rotary recuperators are as follows:

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

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

However, this type of device has significant disadvantages:

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

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

This imposes additional restrictions on the ability to use devices of this type. For example, polluted air from heating stoves cannot be used as a coolant.

Tube and casing system

A tubular type recuperator consists of a system of thin-walled tubes of small diameter located in an insulated casing, through which there is an influx of outside air. The casing removes warm air from the room, which heats the incoming flow.

Warm air must be discharged through the casing, and not through a system of tubes, since it is impossible to remove condensate from them

The main advantages of tubular recuperators are as follows:

• high efficiency due to the countercurrent principle of movement of the coolant and incoming air;
• simplicity of design and absence of moving parts ensures low noise levels and rarely requires maintenance;
• long service life;
• the smallest cross-section among all types of recovery 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 condensation may form in the casing, which requires a constructive solution for its removal. Another disadvantage is that the metal filling has significant weight, despite its small dimensions.

The simplicity of the design of a tubular recuperator makes this type of device popular for self-made. Typically used as an outer casing plastic pipes for air ducts, insulated with polyurethane foam shell.

Device with intermediate coolant

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

In this case, an intermediate coolant is used, circulating between the air ducts through an insulated pipeline. Water or a water-glycol solution is used as a medium for transferring thermal energy, the circulation of which is ensured by operation.

Recuperator with intermediate coolant is a voluminous and expensive device, whose use is economically justified for premises with large areas

If it is possible to use another type of recuperator, then it is better not to use a system with an intermediate coolant, since it has the following significant disadvantages:

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

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

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

Main technical parameters

Knowing the required performance of the ventilation system and the heat exchange efficiency of the recuperator, it is easy to calculate savings on air heating for the room for 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 recuperator or a standard air heater.

Equipment manufacturers often offer a model line in which ventilation units with similar functionality differ in air exchange volume. For residential premises, this parameter must be calculated according to Table 9.1. SP 54.13330.2016

Efficiency

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

K = (T p – T n) / (T v – T n)

In which:

• T p – temperature of the air entering the room;
• Tn – outside air temperature;
• T in – air temperature in the room.

Maximum efficiency value at standard and certain temperature conditions indicate in technical documentation devices. Its actual figure will be slightly less.

In the case of self-manufacturing of a plate or tubular recuperator to achieve maximum efficiency heat transfer must adhere to the following rules:

• The best heat transfer is provided by counter-flow devices, then cross-flow devices, and the least by 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 air inside the device.

E (W) = 0.36 x P x K x (T in - T n)

where P (m 3 / hour) – air flow.

Calculation of the efficiency of the recuperator in monetary terms and comparison with the costs of its acquisition and installation for a two-story cottage with a total area of ​​270 m2 shows the feasibility of installing such a system

The cost of recuperators with high efficiency is quite high, they have complex design and significant size. Sometimes you can get around these problems by installing a few more simple devices so that the incoming air passes through them successively.

Ventilation system performance

The volume of air passed through is determined by 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 mathematical model Therefore, experimental studies are carried out for standard monoblock structures, and components are selected for individual devices.

The fan power must be selected taking into account bandwidth installed recuperators of any type, which is indicated in the technical documentation as the recommended flow rate or volume of air passed by the device per unit of time. As a rule, the permissible air speed 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 costs electricity, ineffective heating of outside air and reduced service life of fans.

The graph of pressure loss versus air flow rate for several models of high-performance recuperators shows a nonlinear increase in resistance, so it is necessary to adhere to the requirements for the recommended air exchange volume specified in the technical documentation of the device

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

Dirty filters and grilles create significant interference with flow, so they must be periodically cleaned or replaced. One of effective ways clogging assessment is the installation of sensors that monitor the pressure drop in areas before and after the filter.

Conclusions and useful video on the topic

Operating principle of rotary and plate recuperator:

Measuring the efficiency of a plate-type recuperator:

Household and industrial systems ventilation systems with an integrated recuperator have proven their energy efficiency in retaining heat indoors. Now there are many offers for the sale and installation of such devices, both in the form of ready-made and tested models, and individual order. You can calculate the required parameters and perform installation yourself.

If you have any questions while reading the information or find any inaccuracies in our material, please leave your comments in the block below.

Having proper air exchange is key factor comfort in the home and health of household members. And then the thought of creating proper ventilation. Lately, there has been so much on the air conditioning equipment market! It is difficult for an unprepared person to understand what he really necessary to create a comfortable microclimate in the apartment.
Let's figure out what, for example, air intakes are used for ventilation valves, air supply units and recuperators.

Used in natural and mechanical ventilation. The valve has protection against insects, noise, dust, wall freezing and condensation, as well as regulation of the amount of incoming air. You can regulate the flow of air passing through the valve using the handle on the head of the valve or a special cord if the valve is located high. On the valve head there is a scale indicating the degree of valve opening. The valve has smooth adjustment until complete closure. KIV-125 does not require any energy consumption.
How does it work? The existing exhaust hood (ventilation ducts located in the kitchen and bathrooms), removing exhaust air, creates a vacuum in the apartment, and due to this vacuum, fresh outside air enters the room through the KIV-125 valves.

Advantages:
* Double air purification.
* Built-in two-stage ceramic heater - for ventilation during the cold season.
* Highly efficient fan - for quiet operation (from 21 dB) with minimal power consumption.
* Productivity from 40 to 120 m 3 / h

The air recuperator ventilates your room by removal old air and influx new, cleaned with a filter, indoors. In the process of air exchange, recovery occurs, the transfer of energy from the outgoing air to the incoming air. In this way, the recuperator saves energy spent on heating in winter and air conditioning in summer.

* * * * *
For efficient work supply valve or installation the hood must be active. An active hood is any stable working exhaust system- mechanical (using fans) or natural (ventilation ducts located in the kitchen and bathrooms). To guarantee the operation of ventilation in the apartment in any season, regardless of the floor, it is recommended to install exhaust fans in kitchens and bathrooms.
Recuperators operate regardless of availability exhaust ducts. We remember that the tasks of recuperators, in addition to the supply of fresh air, include the removal of exhaust air.
BUT! There is a natural hood in every home. That is why, in our opinion, installing recuperators in residential premises is inappropriate . They are more likely to be suitable for rooms in which there is no hood at all (garage, barn, storage room, etc.). The promised energy savings are also a controversial issue, since the volume of incoming air will be clearly insufficient - no more than 40 m 3 /h. Is this what you wanted to achieve by taking care of the ventilation of your home? And you won’t feel the air warming up in cold weather either.

If you need a valid saving, then we recommend considering the KIV-125 supply valves. The performance of the valve depends on the vacuum created by the hood:
at a vacuum of 20 Pa (created by mechanical exhaust) - 50 m 3 / h;
at a vacuum of 10 Pa (creates natural exhaust) - 35 m 3 / h.

If you want greater influx of fresh , purified and, if necessary, noticeably heated air, it is worth thinking about the supply ventilation unit.

And one more important point:
for an external hole up to 150 mm (which is necessary for installation, for example, KIV-125 or iFresh) is not required (if the building is not a cultural heritage site):

4.3.7.* Installation of air conditioning and ventilation systems without an outdoor unit with air supply through a hole in the wall with a diameter of up to 0.15 m, hidden by a fence grate, is allowed everywhere (for cultural heritage sites - in agreement with KGIOP).

*Government of the city of St. Petersburg "On approval of the rules for the maintenance and repair of facades of buildings and structures in St. Petersburg" (No. 1135 of September 14, 2006)

An external hole is required for installation of heat exchangers more diameter - 180 mm.

An energy-efficient ventilation system in the cold season is a fairly pressing issue. Minimizing heat loss, which is constantly emitted from the room, will not only reduce the amount of utility bills, but also reduce the load on the room heating device.

Plate recuperators can help with this - devices that return part of the thermal energy from the exhaust air.

Heating the room in the cold season using a modern air conditioner allows you to maintain a comfortable microclimate in the room. The price you pay for comfort is electricity bills, the size of which can vary significantly depending on the outside air temperature.

With the help of comparatively low costs it is possible to create an energy efficient ventilation system, significantly reducing electricity costs.

A plate recuperator will allow you to implement this, and it does not matter whether it is purchased in a store or made by yourself. This device is built into the supply and exhaust ventilation ducts, helping to reduce “street heating” to a minimum.

Considering that on individual days the difference in indoor and outdoor temperatures can reach fifty degrees Celsius, the importance of eliminating the mentioned effect becomes clear. Moreover, a huge number of circuits and ready-made devices for this are offered.

Air recovery principle

To understand the advantages and benefits of using recuperative heat exchangers, you first need to understand the very essence of their work. Literally translated from Latin, recovery is called “return of used, spent.”

It is the energy return effect that is used in climate control devices of this design. Passing through the block air currents exchange thermal energy with each other, allowing the air conditioner to subsequently maintain a comfortable temperature, using less energy. On particularly cold days, this allows you to significantly save on heating the room.