The ventilation systems in the latest versions are no longer limited to a standard set of functions, the main of which is to update the air environment. For example, through the use of technological filters, equipment minimizes the content of harmful particles in the room, and also prevents the ingress of odors. Ventilation systems are also improving in terms of microclimate regulation, which is especially beneficial from the point of view of energy conservation. For ensuring this possibility, forced-air and exhaust installations with air flow recovery are used. The action of such systems is based on the processing of heat flows that pass through the elements of the ventilation unit. As a result, the user receives not only fresh, but also naturally heated air.
What is the principle of recovery?
The recovery process takes place against the background of the interaction of air flows with different temperatures. That is, heated streams give their heat to cold, thus forming an optimal temperature balance. In ventilation systems, recovery is the transfer of heat to fresh air, which is carried out in a special heat exchanger. However, there are different levels of effectiveness of this process. For example, an open window shows zero efficiency. In this case, the supply flows do not heat up, but lower the air temperature in the room itself. We can say that this is a process that is the opposite of recovery.
The average level of effectiveness varies in the range of 30-90%. The optimal indicator reaches 60%, and systems that demonstrate an indicator above 80% are considered the most productive. The most effective recovery is the heat exchange process, in which the heating of the supply flows reaches a level corresponding to the removed air. But even modern technologies do not allow achieving 100% efficiency.
Recuperator in the ventilation system
The principle of recovery is implemented in the ventilation system in the form of a surface heat exchanger. The process of heat distribution itself is carried out using a wall that separates two oppositely directed flows. Regenerators have a similar device, but the recovery system is different in that the channels for working with air remain the same throughout the entire period of operation. It must be said that climate equipment can serve not only air environments. So recovery is also used in working with gas, liquids, etc. There are various schemes of structural design. The most common are ribbed, tubular and plate models. At the same time, different approaches to the design of flow channels are provided - for example, direct-flow, counter-current, and cross-over devices can be distinguished.
Cross plate heat exchanger
In such installations, membrane partitions are usually used, due to which efficient recovery is ensured. A feature of the system is that with the removal of air, excess moisture also goes out into the street. The supply and exhaust system with recovery is also characterized by frost resistance, which is achieved without special heaters. This advantage allows the use of equipment with a cross-membrane design in conditions of temperature conditions up to -35 ° C.
Such installations are used both in providing residential buildings and in storage rooms where large areas are expected to be serviced. They also became widespread in agriculture - for example, in the arrangement of poultry houses, vegetable stores and livestock farms. Since heat recovery in cross structures with membranes also allows for effective cooling in the summer, this system is also in demand in the manufacturing industry.
Finned Plate Systems
The device of such a recuperator provides for the presence of finned thin-walled plates made by high-frequency welding. Metal panels form a structure with an alternate arrangement of partitions rotated 90 degrees. Due to this scheme, a high temperature of the heating medium, a minimum level of resistance, and also the optimal ratio of the area of the tele-transmitting surface to the weight of the heat exchanger are achieved. In addition, air handling units with heat recovery with ribbed plates are distinguished by their durability and low price. The practice of use confirms that such systems can save about 40% of thermal energy. That is, heating costs are minimized, since fresh air is effectively warmed by the removed flows.
Rotary models
The features of such plants include low cost and fairly high productivity. Although, in terms of fresh air heating, this option is inferior to the plate design with a double cassette. Despite the simple configuration of the working elements, the rotary recovery unit sins with an imperfect distribution of air flows. There is a certain risk that clean air will mix with the exhaust air and as a result the quality of ventilation as a whole will suffer. The disadvantages of such systems include the need for frequent maintenance, which is especially disadvantageous when operating in residential premises. However, the heating process itself is quite effective.
Direct-flow counterflow systems
A feature of recuperators of this type is a tubular design, the elements of which are represented by thin-walled welded elements. During the operation of the installation of this type, a wall vortex is formed, which increases heat transfer, but is destroyed as the resistance in the air channel increases. Most often, such systems are used in industry where delicate heating of one of the working media is needed. Direct-flow counterflow equipment is also used in mechanical engineering to dissipate and utilize heat. A domestic air handling unit with recovery of this type is also in demand - it is recommended to install it in rooms with sealed metal-plastic windows, as well as in ecological houses.
Such recuperators, as a rule, integrate into a single air duct casing, which during operation ensures low power consumption, compact dimensions with the possibility of flush mounting, high performance and reliability of equipment.
Recuperators for energy efficient homes
The very concept of ventilation systems, in which passive heating of fresh air is provided, is aimed at reducing heating fees. But in terms of equipping energy-efficient houses, recovery is also an environmentally friendly way to normalize the microclimate. Manufacturers produce special lines that use materials that are safe and efficient in terms of recovery. In particular, the latest models receive three-stage heat exchangers made of non-porous ultrathin membranes. Such a device eliminates the need for electric air heaters.
In addition to uniform heat transfer, such devices also work effectively with humidity. They provide a full return of moisture to the room with the complete exception of condensers. As a result, ventilation with recovery also eliminates the need to install drainage drains.
Automation for recuperators
Supply and exhaust heat accumulators are also developing in the direction of electronic filling. In order to optimally distribute the flows, manufacturers provide installations with the ability to automatically adjust the position of inter-channel partitions. In more advanced models, it is also possible to set speed modes, display temperature indicators and control the degree of contamination of filters with an alarm. In addition, modern ventilation with recovery provides the ability to control an external duct heater without connecting third-party devices to the process. That is, in this case, additional heating of the air is ensured to the optimum value.
Filters in recuperators
Like all modern ventilation systems, recovery models require the inclusion of cleaning devices in the design. Since heat transfer involves the maximum reduction of the outgoing and injected air flows, filters in this case play a particularly important role. Most often, air ducts themselves use F7 filters, which exclude the passage of particles with a size of 0.5 microns. G3 coarse filters are less common, but this addition may be required depending on the design. For ease of maintenance, the recovery system is often equipped with filters made of plastics and special fibers - these elements are easy to wash and shake. As already noted, modern models are also equipped with indicators that determine the moment for the replacement of the filter.
Recuperator Benefits
The technologies that are used in the supply and exhaust recovery systems minimize energy consumption and increase the ergonomics of climate equipment. In practice, the user of such an installation can feel the improvement of microclimate indicators. Of course, heat recovery is not as effective, from the point of view of the heating function, as special heating units, but its operation does not require additional energy consumption. The inclusion of auxiliary heating means in the system allows balancing both an increase in the temperature regime and savings in energy consumption. In general, according to the calculations of specialists, the use of recovery allows 10-15% to reduce heating costs.
Disadvantages of recuperators
Such systems have two serious drawbacks. This is primarily the icing of heat exchangers in winter. For this reason, many users complain about the failure of the equipment in the first weeks of operation in cold weather. However, manufacturers are striving to improve the protective qualities of equipment by supplying plants with thermal batteries and durable fans. The second drawback that the supply and exhaust systems with recovery have is their noisy operation. This is especially evident in rotary models. At the same time, developers strive to provide new models with improved means of isolation, so low-noise options can also be found on the market.
What to consider when choosing a unit with a recuperator?
A consumer who has decided to install such a system in his home should be guided by the system's performance, structural design, and functionality. So, a performance indicator determines the possibility of ventilation in a room of a specific area. No less important is the design in which the equipment is made. For example, a heat recovery unit with tubular elements makes it convenient to carry out installation with minimal space requirements. As for functionality, it affects both the ability to regulate indoor climate indicators and the ergonomic characteristics of the system.
Conclusion
The operation of traditional ventilation systems does not give a hint of an energy-saving function. As a rule, these are voracious massive installations that make a significant contribution to increasing the cost of maintaining a house. Against this background, recovery is an almost revolutionary approach to the production of HVAC equipment, which involves the rational use of already used thermal energy. If a typical system implements air heating as it enters the room with the help of heating equipment, then the recovery allows you to initially increase the temperature of the incoming flows without connecting special heaters. Of course, such plants have their drawbacks, but manufacturers are struggling with them, improving the design of recuperators.