Heat recovery has become quite often used recently in ventilation systems. If we consider the process itself in more detail, then we first need to decide and understand what the term recovery itself means. Heat recovery in ventilation systems means that the passed air that is removed special installations, is passed through the filter system and fed back.
Worth paying Special attention to the fact that in ventilation systems with a share of the exhaust air, part of the heat from the room is also extracted. And this is exactly thermal energy and comes back.
These systems are effectively used in large industries and in large workshops, since, in order to ensure optimum temperature for such premises in winter it is necessary to expose yourself high costs. These installations can significantly compensate for such losses and reduce costs.
Even in a private house, ventilation units with heat recovery will be quite relevant today. Even in individual house ventilation is always performed and when air circulates, heat also leaves any room. Agree that it is simply impossible to seal the building completely and thereby avoid any heat loss.
Today, these systems should be used even in a private house for the following reasons:
- For the rapid removal of air with a large admixture of carbon dioxide;
- For inflow required amount fresh air and in residential premises;
- To eliminate high humidity in rooms, as well as eliminate unpleasant odors;
- To save heat;
- Also for removing dust and harmful microorganisms that it may contain.
Air supply systems with recuperation
The air handling unit with heat recovery is becoming increasingly popular among private homeowners. And its merits, especially in the cold season, are very high.
As you know, there are many ways to provide a living space with the necessary ventilation. This and natural circulation air, which is mainly carried out by ventilation of 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 naturally, there is no more effective system, it turns out that in cold weather 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, recently, when almost all owners install plastic windows and doors, it turns out that they need to arrange ventilation natural way just inefficient. Therefore, there is a need to install additional equipment that can provide good air circulation inside the premises. And, of course, every owner will agree that it would be desirable for any system to spend electricity economically.
And here the best option would be heat recovery in ventilation systems. Ideally, it is desirable to purchase a unit that could also provide moisture recovery.
What is moisture recovery?
In any room, a certain level of humidity should always be maintained, at which each person feels most comfortable. This norm has a value from 45 to 65%. In winter, most people experience excessively dry indoor air. Especially in apartments, when the heating is turned on to 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 changes 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 falls apart. These installations will primarily support and required level humidity in any room, regardless of the time of year.
Types of recuperators
In individual residential buildings most often install ventilation systems 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 coolant.
Plate type 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 there is a thin lamellar partition, 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 off its heat to the supply air, which enters the house already warm, thanks to such an exchange.
The advantages of this technology include:
- simple device setup;
- the complete absence of any moving parts;
- high efficiency.
Well, one of the most significant drawbacks in the operation of such a heat exchanger is the formation of condensate on the plate itself. Typically, such heat exchangers require additional installation with special drop eliminators. This is a necessary parameter, since in winter the condensate can freeze and stop the device. That is why some devices of this type have built-in defrost 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 with the help of constant rotation. Rotary type heat recovery ventilation has a very high efficiency. This system allows you to return back to the room about 80% of the heat.
But a significant drawback is the inferiority of the system with respect to dirt, dust and odors. There is no density in the design between the rotor and the housing. Because of them, air flows can mix and therefore all pollution can again get back. And of course, 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 heat exchanger, the air flows are separated directly by the chamber itself. The exchange of heat occurs due to the damper, which periodically changes the direction of air flow. This system has high efficiency at work. And the disadvantages include only the presence of moving parts inside the device.
Heat exchangers with intermediate carrier
The principle of operation of this device is almost similar to the operation of a plate heat exchanger. Here the heat exchanger is a closed circuit of the tube. In it there is a constant circulation of water or a 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 downside is the lack of efficiency. Such a device is able to return approximately 50% of the heat taken from the room.
heat pipes
It is worth highlighting another type of recuperators. Heat recovery in the house using heat pipes is quite effective. Such devices are sealed tubes made of metal, which has high heat-conducting properties. Inside such a tube is a liquid that has a very low boiling point (usually freon is 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. Pullable warm air, washing the pipe, transfers heat to the freon, which, when boiling, moves up, with large quantity heat. And the supply air washing the top of the tube takes this heat with it.
The advantages include high efficiency, quiet operation and a high coefficient useful action. So today you can significantly save on heating the house, partially returning it back.
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 without forced ventilation it is simply impossible to do without, most often they resort to its device in industrial premises with worse working conditions. Let us leave aside the industrialists and the production worker 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 housing, and only then they realize that due to lack of oxygen it is difficult to be indoors.
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 decision- forced-exhaust ventilation device with heat and moisture recovery.
Recovery means its preservation. The outgoing air flow changes the temperature (heats, cools) of the supplied air by the supply and exhaust unit.
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. Outgoing and incoming flows pass through different sides heat-conducting plates without contact with each other.
On average, the efficiency of such devices is 55-75%. positive characteristic assuming there are no moving parts. The disadvantages include the formation of condensate, which often leads to freezing of the recuperative device.
Exist plate heat exchangers with moisture-permeable plates, ensuring 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.
Rotary
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 high level 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 option 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 recuperators with small size, 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 for effective work sufficient distance is required between the retracted and supply air 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 substantial harm to your 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 a quality supply and exhaust ventilation while maintaining a comfortable level of humidity.
In the process of ventilation from the room, not only the exhaust air is utilized, but also part of the thermal energy. In winter, this leads to an increase in energy bills.
To reduce unjustified costs, not to the detriment of air exchange, will allow heat recovery in ventilation systems of centralized and local type. For the recovery of thermal energy are used different types heat exchangers - recuperators.
The article describes in detail the models of units, their design features principles of operation, advantages and disadvantages. The information provided will help you choose the best option for the arrangement of 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 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 wide selection 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 natural ventilation and compulsory system with recovery:
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 have questions about the work of different ventilation recuperators? Please leave comments on the publication, share your experience in operating such installations. The contact form is in the bottom block.
The heat exchanger 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.
An unusual name was given to the usual. 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 that comes from the supply system clean air. 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:
- AT summer time The system reduces 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.
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 passes through a cold closed environment, condensation occurs. If the temperature environment below zero, then the ribs 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 operating together with the recuperator are energy dependent. The ongoing economic calculation determines that only those models of recuperators 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.
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. plate type 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 opening the valve cold air enters two channels.
This class of device can be classified as 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 we can say 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 inputs: one for fresh air, the second for exhaust.
- From the filter coarse cleaning 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:
- Wick.
- Container.
- Cavity with steam.
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.
Rotary type can be called modern version execution. 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 airflow, increase System efficiency can be 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 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 channels 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.
comparison table
In order to determine whether a heat redirection system should be installed, efficiency studies are carried out. An example of such a calculation is given on a relatively small private house. The features of the calculation include:
- According to the calculations carried out, approximately 35% of the heat is lost through the ventilation system. Let's take 30% as an average value, since modern ventilation systems are more efficient in terms of energy savings.
- The average show power consumption is 500 watts. Note that this indicator was chosen taking into account the location of the house in Sevastopol. The average temperature in January is about 3.5 degrees Celsius. Energy consumption in colder climates will be much higher.
- If installed plate construction recuperator, then consumer power will be limited at around 30 watts.
- The system efficiency indicator is at around 40%.
According to the calculation carried out on the basis of the data entered, the payback period is approximately 114 years. Therefore, it does not make sense to purchase a plate heat exchanger for a private house.
Significantly reduce costs by self-manufacturing the structure. The principle of its work is quite simple. Therefore, when using improvised materials, you can create. Recommendations for creating the considered design are as follows:
- To begin with, aluminum pipes are cut into small pieces. When choosing a pipe, preference should be given to versions with a diameter of 10 millimeters. At the same time, we note that the greater the thickness of the metal, the more the pipe absorbs heat.
- The next step can be called cutting out two plates from sheet aluminum. When choosing plates, you should pay attention to versions with a thickness of 4 millimeters. In these plates, holes are created for previously cut pipes.
- A sealant is used as a connecting element, which is immune to high or low temperatures.
The principle of operation of the structure is as follows:
- The heat recuperator is installed as a common element in the supply and exhaust system.
- Two pipes are connected to the heat exchanger on one side, and two on the other.
- In order to increase the efficiency of the design, fans are installed.
- The whole system has a housing that protects the mechanisms from exposure to the environment.
- The pipes act as a steam heat distributor.
This is how it is created simplest design to exchange heat between two systems.
conclusions
In conclusion, we note that the above information allows you to calculate the profitability of installing a heat exchange system. Almost all designs are highly reliable and do not fail. Also, their efficiency is relatively small, the installation is advisable only in large ventilation systems.
