Recuperation working principle. How to make the right choice among different types of recuperators. Recuperator of own production

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.

Electric motors are designed to drive various mechanisms, but after the movement is completed, the mechanism must be stopped. To do this, you can also use an electric machine and a recuperation method. What is energy recovery is described in this article.

What is recovery

The name of this process comes from the Latin word “recuperatio”, which translates as “back receiving”. This is the return of part of the energy or materials used for reuse.

This process is widely used in electric vehicles, especially those powered by batteries. When driving downhill and during braking, the recovery system returns the kinetic energy of movement back to the battery, recharging them. This allows you to drive a longer distance without recharging.

Regenerative braking

One type of braking is regenerative. In this case, the rotation speed of the electric motor is greater than that specified by the network parameters: the voltage at the armature and the field winding in DC motors or the frequency of the supply voltage in synchronous or asynchronous motors. In this case, the electric motor switches to the generator mode, and the generated energy is returned to the network.

The main advantage of the recuperator is energy saving. This is especially noticeable when driving around the city with a constantly changing speed, suburban electric transport and the subway with a large number of stops and braking in front of them.

In addition to the advantages, recovery has disadvantages:

• the impossibility of a complete stop of transport;
• slow stop at low speeds;
• lack of braking force in the parking lot.

To compensate for these shortcomings, an additional system of mechanical brakes is installed on vehicles.

How the recovery system works

To operate, this system must provide mains power to the motor and return energy during braking. This is most easily done in urban electric vehicles, as well as in older electric vehicles equipped with lead batteries, DC motors and contactors - when downshifting at high speed, the energy recovery mode is activated automatically.

In modern transport, a PWM controller is used instead of contactors. This device allows you to return energy to both DC and AC networks. During operation, it works as a rectifier, and during braking, it determines the frequency and phase of the network, creating a reverse current.

Interesting. During dynamic braking of DC motors, they also switch to generator mode, but the generated energy does not return to the network, but is dissipated by additional resistance.

Power descent

In addition to braking, the recuperator is used to reduce the speed when lowering loads by hoisting mechanisms and while driving down an inclined road of electric vehicles. This eliminates the need for a wearable mechanical brake.

Application of recuperation in transport

This braking method has been used for many years. Depending on the type of transport, its application has its own characteristics.

In electric vehicles and electric bicycles

When driving on the road, and even more so, off-road, the electric drive works almost all the time in traction mode, and before stopping or at an intersection - “coasting”. The stop is made using mechanical brakes due to the fact that the recovery at low speeds is inefficient.

In addition, the efficiency of batteries in the charge-discharge cycle is far from 100%. Therefore, although such systems are installed on electric vehicles, they do not provide large savings in charge.

On the railway

Recuperation in electric locomotives is carried out by traction motors. At the same time, they turn on in the generator mode, which converts the kinetic energy of the train into electricity. This energy is fed back into the network, unlike rheostat braking, which causes the rheostats to heat up.

Recuperation is also used during long downhill runs to maintain a constant speed. This method saves electricity, which is returned to the grid and used by other trains.

Previously, only DC locomotives were equipped with this system. In devices operating on AC power, there is a difficulty in synchronizing the frequency of the output energy with the mains frequency. Now this problem is solved with the help of thyristor converters.

In the underground

In the subway, during the movement of trains, there is a constant acceleration and deceleration of cars. Therefore, energy recovery gives a great economic effect. It reaches its maximum if it occurs simultaneously in different trains at the same station. This is taken into account when scheduling.

In city public transport

In urban electric transport, this system is installed in almost all models. It is used as the main one up to a speed of 1-2 km / h, after which it becomes ineffective, and the parking brake is activated instead.

In Formula 1

Starting from 2009, a recovery system has been installed in some machines. This year, such devices have not yet given tangible superiority.

In 2010, such systems were not used. Their installation, with a limitation on power and the amount of recovered energy, resumed in 2011.

Braking of asynchronous motors

Speed ​​reduction of asynchronous electric motors is carried out in three ways:

• recovery;
• opposition;
• dynamic.

Regenerative braking of asynchronous motor

Regeneration of asynchronous motors is possible in three cases:

• Changing the frequency of the supply voltage. Possible when the motor is powered by a frequency converter. To switch to the braking mode, the frequency is reduced so that the rotor speed is greater than synchronous;
• Switching windings and changing the number of poles. It is possible only in two, - and multi-speed electric motors, in which several speeds are provided constructively;
• Power descent. It is applied in load-lifting mechanisms. In these devices, electric motors with a phase rotor are installed, the speed control of which is carried out by changing the value of the resistance connected to the rotor windings.

In any case, when braking, the rotor begins to overtake the stator field, the slip becomes greater than 1, and the electric machine begins to work as a generator, transferring energy to the network.

Anti-inclusion

The opposition mode is carried out by switching the two phases that feed the electric machine between themselves and turning on the rotation of the apparatus in the opposite direction.

It is possible to switch on when additional resistances are turned on in the stator circuit or phase rotor windings. This reduces current and braking torque.

Important! In practice, this method is rarely used due to the excess currents 8-10 times higher than the nominal ones (with the exception of motors with a phase rotor). In addition, the device must be turned off in time, otherwise it will begin to rotate in the opposite direction.

Dynamic braking of asynchronous motor

This method is carried out by applying a constant voltage to the stator winding. To ensure trouble-free operation of the electric machine, the braking current should not exceed 4-5 no-load currents. This is achieved by including additional resistance in the stator circuit or by using a step-down transformer.

The direct current flowing in the stator windings creates a magnetic field. When crossing it, an EMF is induced in the rotor windings, and a current flows. The released power creates a braking torque, the strength of which is greater, the higher the speed of rotation of the electric machine.

In fact, an asynchronous electric motor in dynamic braking mode turns into a DC generator, the output terminals of which are shorted (in a machine with a squirrel-cage rotor) or connected to additional resistance (an electric machine with a phase rotor).

Recuperation in electric machines is a type of braking that saves energy and avoids wear on mechanical brakes.

Video

The question of the quality of inhaled air has been and remains the most important for human life. Various parameters play a role. Temperature, cleanliness and freshness take the first place among them. Often there is not enough light ventilation with the help of a window. Too cold incoming air brings a certain discomfort. The appearance of a stuffy summer lazy breeze also does not bring pleasure.

What is it and how does it work

Ventilation-type heat-exchange structures (recuperators) help to change the situation. The name of the device comes from the English and Latin words for "return».

The principle of work fully corresponds to the etymological meaning. The air in the room sucked in by the ventilation system and forcibly thrown out into the street. At the same time, an external jet of freshness is sent into the room. Inside heat exchange takes place, thanks to which the air masses of the required temperature are returned to the room.

An important indicator of ventilation systems is the percentage of mixing of incoming and exhaust air. The operation of recuperators makes it possible to reduce this position to almost zero. This is achieved by the presence of a plastic, copper, aluminum or zinc separator. Heat exchange takes place by transferring the flow energy to the boundary. The jets themselves run either parallel or crosswise.

Grates of a special type at the inlet of the stream from the street allow you to trap dust, pollen, insects, and reduce the number of incoming bacteria. The air is purified and enters the room. At the same time, waste particles containing many harmful ingredients. In addition to the circulation of air flows, the supply jets are cleaned and warmed.

Most of the existing recuperators have gentle sound modes, which promote strong healthy sleep when installed in a nursery or bedroom.

Many designs of recent years are compact and easy to install, have a remote control, and have additional features.

The temperature standards in the apartment are studied in detail in this article:

Types of recuperators

Depending on the various parameters consider:

• Plate heat exchangers
• Rotary heat exchangers
• Chamber recuperators
• Recuperators with an additional built-in heat exchanger
• Composition of several heat pipes

Plate heat exchangers. The heat exchanger inside consists of one or more fixed plates made of copper, aluminum, plastic or extra strong, specially treated cellulose. Air passes through a series of cassettes. Due to the temperature difference between the incoming and outgoing streams, a slight condensate may occur. Possibly in cold weather some formation of ice. As a rule, to combat it, the device is equipped with additional elements, the functions of which are to remove the accumulation of condensate, to increase the heat supply to defrost the system.

If the recuperators are equipped with one air movement cassette, then when droplets form, the flow is redirected to bypass it, and the accumulated moisture is removed through a special drainage device. If the system involves several elements, then condensation is reduced to zero.

When ice appears, a special valve blocks the flow of incoming air, due to the heat on the plates, the internal components of the device are heated. Another way to solve the problem was creation of pulp cassettes. However, their use in rooms with a high degree of humidity increases the formation of condensate and makes the devices inapplicable.

Plate heat exchangers are designed in such a way that the mixing of incoming and outgoing jets is not possible, and the filtration system is additionally removes dust, pollen and bacteria. This makes it possible to use it in bedrooms, in a nursery, in hospitals. Creation of ribbed plates allows increase the efficiency of the structure, makes it more reliable and durable. Due to their compactness and low cost, such designs are more applicable both in hospitals, catering establishments, and at home.

Many craftsmen have learned to create designs on their own from some a set of copper or galvanized plates with the use of special sealant and material for additional gasket between the sheets.

Рhttp://site/eko/rekuperator-vozduha-svoimi-rukami.htmlmotor recuperators. Its features are the rotating blades of one or two rotors, due to which the air moves. Most often, these devices are cylindrical shape with densely installed plates inside and a drum, the rotation of which creates flows. First, an air jet leaving the room is passed, then the direction of rotation changes and street air enters.

The efficiency of rotary heat exchangers is higher than lamellar, but the devices themselves are more bulky. Their use is more suitable for industrial premises, trading floors. Since the probability of mixing air flows reaches, as a rule, 5-7 percent, the installation of rotary heat exchangers becomes impossible for hospitals, canteens, cafes and restaurants. More expensive equipment, bulkiness and complexity of installation made the use of such structures possible only in special industrial areas.

Chamber recuperators. The air from the room enters a special chamber, in which heat is transferred to the walls of its part, then it is thrown out into the street. Further, the outside air is sucked inward into another compartment, additionally warming up from the borders, and enters the room.

Recuperators with an additional built-in heat exchanger. It enhances the heat transfer edge. However, it is less efficient because it reduces efficiency and increases condensate.

Composition of several heat pipes. The air from the room is additionally heated, turning into steam, and then reverse condensation occurs. The advantages of such recuperators are in the complete anti-bacterial air protection in the design.

When choosing a device, the size of the room and the degree of its humidity, its purpose, the need for quiet operation, efficiency and the cost of the structure and its installation are taken into account.

You can read more about comfortable humidity in the apartment in this article:

The use of recuperators (video)

1. In rooms to create additional climatic comfort.
2. To save energy resources.
3. In hospitals, to increase the antibacterial zone, to create a comfortable environment, to maintain the thermal characteristics of the room.
4. In industrial premises, for ventilation of large spaces while maintaining a zone of constant temperatures, rotary heat exchangers are more often used that can withstand temperatures up to 650 degrees.
5. in automotive structures.

When building a house, it is necessary to select and install a system for heat recovery in ventilation systems. There are several modifications of ventilation equipment, which are chosen depending on its manufacturer. Natural impulse equipment includes wall and window vents to bring fresh air into the rooms. To remove odors from toilets and bathrooms, as well as from kitchens, exhaust ducts are installed.

Air exchange is obtained due to the temperature difference in the room and outside. During the summer, temperatures even out both inside and outside the rooms. That is, air exchange is suspended. In winter, the effect manifests itself more quickly, but it will require more energy to heat cold outdoor air.

Composite hood is a system with forced ventilation and natural air circulation. The disadvantages are:

The advantages include low price and the absence of external natural factors. But at the same time, in terms of quality and functionality, aeration cannot be considered a full-fledged ventilation.

To ensure comfortable conditions in new residential buildings, universal systems of forced aeration are installed. Systems with a heat exchanger ensure the supply of fresh air at a normal temperature with the simultaneous removal of exhaust air from the premises. Along with this, heat is removed from the discharge stream.

Saving heat energy using supply and exhaust ventilation with a heat exchanger // FORUMHOUSE

Depending on the types of recuperators and the size of the rooms in which ventilation is installed, the microclimate is improved more or less effectively. But even with installed recuperation with an efficiency of only 30%, energy savings will be significant, and the overall microclimate in the rooms will also improve. But heat exchangers also have disadvantages:

• increase in electricity consumption;
• condensate release, and icing occurs in winter, which can lead to damage to the heat exchanger;
• loud noise during operation, causing great inconvenience.

Heat exchangers or heat recovery units in ventilation systems with enhanced heat and noise insulation operate very quietly.

Recuperators of the directed movement of heat carriers assume ventilation and utilization of warm exhaust air. The device moves air in two directions at the same speed. With heat exchangers, the comfort of life in houses increases.

At the same time, heating and ventilation costs are significantly reduced, combining both serious processes into one. Such devices can be used both in residential and industrial premises. Thus, the savings in money will be approximately thirty to seventy percent. Heat exchangers can be divided into two groups: single-acting heat exchangers and heat pumps for increasing the reserve of utilized heat. Heat exchangers can only be used in cases where the resources of the sources are greater than the resources of the microclimate to which heat energy is transferred.

Apartment ventilation system with Ecoluxe EC-900H3 recuperator.

Devices that transfer heat from sources to consumers using intermediate working fluids, for example, liquids circulating in closed circuits, consisting of circulation pumps, pipelines and heat exchangers located in heated and cooled chambers, are called recuperators with intermediate heat carriers. Such equipment is widely used in various heat exchangers and circulation pumps at large distances between the heat source and consumer.

This principle is used in an extensive system of heat recovery and energy consumers with different characteristics. The operation of a heat exchanger with an intermediate heat carrier is that the process in it proceeds in the range of water vapor with a change in the state of aggregation at a constant temperature, pressure and volume. The operation of heat recovery units with heat pumps is different in that the movement of the working fluid in them is produced by a compressor.

Efficiency of the heat exchanger pipe in the pipe in the fall. +6g.C. on the street.

Mixed action devices

For disposal and for heating supply air use exchangers of recuperative or contact type. Mixed-action devices can also be installed, that is, one - recuperative action, and the second - contact. It is desirable to install intermediate coolants that are harmless, inexpensive, non-corrosive in pipelines and heat exchangers. Until recently, only water or aqueous glycols acted as intermediate heat carriers.

At the moment, their functions are successfully performed by the refrigeration unit, which works as a heat pump in combination with a heat exchanger. Heat exchangers are located in the supply and exhaust air ducts, and with the help of a compressor, freon is circulated, the flows of which transfer heat from the exhaust air stream to the supply air and vice versa. It all depends on the time of year. Such a system consists of two or more, which are united by one refrigeration circuit, which ensures synchronous operation of the units in different modes.

Features of plate and rotor designs

The simplest design of the plate heat exchanger. The basis of such a heat exchanger is hermetic chamber with parallel air ducts. Its channels are separated by steel or aluminum heat-conducting plates. The disadvantage of this model is the formation of condensate in the exhaust ducts and the appearance of an ice crust in winter. When the equipment is defrosted, the incoming air goes to the heat exchanger, and the warm outgoing air masses contribute to the melting of ice on the plates. To prevent such situations, it is preferable to use plates made of aluminum foil, plastic or cellulose.

Rotary heat exchangers are the most highly efficient devices and are cylinders with corrugated metal layers. As the drum set rotates, a warm or cold air stream enters each section. Since the efficiency is determined by the rate of rotation of the rotor, it is possible to control such an apparatus.

The advantages include the return of heat of approximately 90%, the economical use of electricity, humidification of the air, the shortest payback period. To calculate the efficiency of the heat exchanger, it is necessary to measure the air temperature and calculate the enthalpy of the entire system using the formula: H = U + PV (U - internal energy; P - system pressure; V - system volume).