KR101719788B1 - Heat recovery system - Google Patents

Abstract

The present invention relates to a waste heat recovery system varied in accordance with load fluctuation of industrial waste heat, comprising a heat storage tank, first and second pumps, a heat exchange unit for waste heat recovery, a heat exchange unit in a greenhouse, first to fourth temperature sensors, and a control unit. The heat storage tank is connected to first and second thermal medium outlet pipes, and first and second thermal medium inlet pipes, and stores thermal medium. The first pipe is installed in the first thermal medium outlet pipe. The second pipe is installed in the second thermal medium outlet pipe. Each of the heat exchange units for waste heat recovery includes multiple heat exchangers for waste heat collection connected to the first thermal medium outlet or inlet pipe through a valve, so heat exchange can be variously realized from the industrial waste heat depending on opening/closing of the valve. Each of the heat exchange units in a greenhouse includes multiple heat exchangers connected to the second thermal medium outlet and inlet pipes to supply heat to the inside of the greenhouse. The first temperature sensor is installed in a place where the heat exchange unit for waste heat collection and the second temperature sensor is installed inside the heat storage tank, the third temperature sensor is installed outside the group, and the fourth temperature sensor is installed inside the greenhouse. The control unit controls the first and second pumps, and the valves in accordance with temperatures detected in the first to fourth temperature sensors.

Description

{HEAT RECOVERY SYSTEM}

The present invention relates to a waste heat recovery system, and more particularly to a variable waste heat recovery system.

Generally, crops require specific growth conditions, among which temperature is a very important factor. To this end, we have built agricultural facilities such as greenhouses and installed heating systems to keep the temperature in agricultural facilities properly. Fossil fuels such as gas and petroleum are used to operate these heaters. The percentage of the horticultural farmers' operating expenses to heating costs varies by crops, but it is about 3040%, which is about 50% Which is a direct economic burden of the present.

Industrial waste heat is the heat that is not recycled and discarded in the course of industrial use or treatment of combustion heat of fuels such as fossil energy. A typical example of this is a thermal power plant where the turbine is cooled and discarded in the sea. However, the amount and temperature of industrial waste heat changes depending on the internal and external influences such as the production amount of the product. In addition, when an attempt is made to heat and cool an agricultural facility such as a greenhouse using industrial waste heat, the heating / cooling load of the agricultural facility changes depending on the outside temperature. For example, the discharge temperature of hot water discharged from a thermal power plant, which is a typical industrial waste heat, changes depending on the temperature of seawater, and the amount of waste heat discharged according to incineration heat of a waste incinerator changes according to the amount of waste.

At this time, the conventional waste heat recovery system circulates the heat medium regardless of the temperature difference between the heat storage tank including the heating medium and the hot water for absorbing external waste heat. However, when the difference between the heat storage tank and the warm water is small, the heat medium is exhausted while the pipe connecting the heat storage tank and the hot water water is circulated, and energy for the heat medium circulation is consumed, Furthermore, when the temperature of the air is extremely low in the ground exposed to the pipe, the temperature of the heating medium is lower than that of the heat storage tank, and it may be advantageous to not drive it.

Accordingly, a problem to be solved by the present invention is to provide a method and apparatus for controlling the heat transfer area of a heat exchanger capable of recovering waste heat by variably controlling the load variation (temperature or heat amount fluctuation) of industrial waste heat, And to provide a waste heat recovery system capable of producing high quality agricultural products and reducing cooling and heating costs by optimally recovering industrial waste heat and optimizing the temperature environment of agricultural facilities such as greenhouses for growth of crops in response to fluctuations in heating and cooling load of the facility.

In order to solve these problems, a waste heat recovery system according to an exemplary embodiment of the present invention includes a heat storage tank, a first pump, a second pump, a waste heat recovery heat exchange unit, a warm indoor heat exchange unit, A temperature sensor, a third temperature sensor, a fourth temperature sensor, and a control unit. The heat storage tank is connected to the first heating medium discharge pipe, the first heating medium inlet pipe, the second heating medium discharge pipe and the second heating medium inlet pipe, and the heating medium is stored. The first pump is installed in the first heating medium discharge pipe or the first heating medium inlet pipe. And the second pump is installed in the second heating medium discharge pipe or the second heating medium inlet pipe. The waste heat recovery heat exchanging unit includes a plurality of waste heat recovery heat exchangers connected to any one of the first heat medium discharge pipe and the first heat medium discharge pipe through a valve, Therefore, heat exchange can be performed variably. The hot indoor heat exchanger includes a plurality of hot indoor heat exchangers connected to the second heat medium discharge pipe and the second heat medium inlet pipe, respectively, to supply heat to the greenhouse. The first temperature sensor is installed at a location where the waste heat recovering heat exchange unit is installed. The second temperature sensor is installed in the heat storage tank. The third temperature sensor is installed outside the greenhouse. The fourth temperature sensor is installed inside the greenhouse. The controller controls the first pump, the second pump, and the valves according to the temperatures sensed by the first through fourth temperature sensors.

Meanwhile, the control unit may control to open a predetermined number of valves so that a larger number of valves are opened as the temperature difference is larger, in accordance with the temperature difference between the first temperature sensor and the second temperature sensor.

At this time, the controller may control the first pump so that the heating medium is driven at a predetermined speed so that the heating medium is circulated as the temperature difference increases, according to the temperature difference of the first temperature sensor.

The control unit may control the second pump such that the temperature of the third temperature sensor is driven at a predetermined speed so that the heating medium is circulated as the temperature difference increases as the temperature difference of the fourth temperature sensor increases.

At this time, the controller may drive all of the plurality of the indoor heat exchangers regardless of the temperature difference of the third temperature sensor.

A waste heat recovery system according to another exemplary embodiment of the present invention includes a heat pump, a heat storage tank, a first pump, a second pump, a third pump, a waste heat recovery heat exchange unit, a hot indoor heat exchange unit, 2 temperature sensor, a third temperature sensor, and a control unit. The heat pump is connected to the first heating medium discharge pipe and the first heating medium inlet pipe. The heat storage tank is connected to the second heat medium discharge pipe and the second heat medium inlet pipe, and is connected to the heat pump, the first connection pipe and the second connection pipe, and the heat medium is stored. The first pump is installed in the first heating medium discharge pipe or the first heating medium inlet pipe. And the second pump is installed in the second heating medium discharge pipe or the second heating medium inlet pipe. The third pump is installed in the first connection pipe or the second connection pipe. Wherein the waste heat recovery heat exchanger includes a plurality of waste heat recovery heat exchangers each connected to one of the first heat medium discharge pipe and the first heat medium discharge pipe through a valve, , It is possible to perform heat exchange in a variable manner. The hot indoor heat exchanger includes a plurality of hot indoor heat exchangers connected to the second heat medium discharge pipe and the second heat medium inlet pipe, respectively, to supply heat to the greenhouse. The first temperature sensor is installed at a location where the waste heat recovering heat exchange unit is installed. The second temperature sensor is installed outside the greenhouse. The third temperature sensor is installed inside the greenhouse. The control unit controls the first pump, the second pump, and the valves in accordance with the temperatures sensed by the first through third temperature sensors.

At this time, the controller may open a predetermined number of valves to open a smaller number of valves according to the temperature of the first temperature sensor.

As described above, according to the waste heat recovery system of the present invention, by appropriately recovering the industrial waste heat and responding to fluctuations in the cooling and heating load of agricultural facilities such as a greenhouse for heating and cooling using industrial waste heat (industrial temperature) By optimizing the temperature environment of agricultural facilities for crop growth, it is possible to produce high quality agricultural products and to reduce heating and cooling costs.

That is, when the temperature difference between the hot water for absorbing the heat storage tank and the external waste heat is large, the heating medium in contact with the hot water is increased, and when the temperature difference is small, the heat medium in contact with the hot water is reduced, .

Further, when the temperature difference is high and the heat medium is driven by a large number of waste heat recovering heat exchangers, the heat medium is dispersed and the pressure is lowered, so that the driving of the first pump is strengthened, have.

In addition, the temperature of the third temperature sensor drives all of the plurality of temperature indoor heat exchangers irrespective of the temperature difference of the fourth temperature sensor, thereby preventing the stress of the crop due to a rapid temperature change of the greenhouse.

On the other hand, in contrast to the first embodiment, in the second embodiment including the heat pump, the control unit sets the predetermined number of valves so as to open a smaller number of the valves as the temperature rises in accordance with the temperature of the first temperature sensor So that it is possible to prevent the heat pump from being overloaded.

1 is a schematic diagram showing a waste heat recovery system according to an exemplary embodiment of the present invention.
2 is a schematic diagram showing a waste heat recovery system according to another exemplary embodiment of the present invention.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures may be exaggerated to illustrate the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprising" or "having ", and the like, are intended to specify the presence of stated features, integers, steps, operations, elements, parts, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof. In addition, A and B are 'connected' and 'coupled', meaning that A and B are directly connected or combined, and other component C is included between A and B, and A and B are connected or combined .

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not. Also, in the claims of a method invention, each step may be reversed in order, unless the steps are clearly constrained in order.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

1 is a schematic diagram showing a waste heat recovery system according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a waste heat recovery system 100 according to an exemplary embodiment of the present invention includes a heat storage tank 110, a first pump 120, a second pump 130, a waste heat recovery heat exchange unit A second temperature sensor 170, a third temperature sensor 180, a fourth temperature sensor 190, and a control unit 1000. The control unit 1000 controls the operation of the indoor heat exchanging unit 150, the indoor heat exchanging unit 150, the first temperature sensor 160, .

The heat storage tank 110 is a storage tank for storing a heating medium and includes a first heating medium discharge pipe 111, a first heating medium inlet pipe 112, a second heating medium discharge pipe 113 and a second heating medium inlet pipe 114, . The heating medium may be water, but is not limited thereto, and other media may be used.

The first pump 120 is installed in the first heating medium discharge pipe 111. Alternatively, the first pump 120 may be installed in the first heating medium inlet pipe 112.

The second pump 130 is installed in the second heating medium discharge pipe 113. Alternatively, the second pump 130 may be installed in the second heating medium inlet pipe 114.

The waste heat recovery heat exchanging unit 140 includes a plurality of waste heat recovery heat exchangers 141, 142, and 143, and is capable of performing heat exchange from the industrial waste heat in accordance with the opening and closing of the valve. In FIG. 1, the waste heat recovering heat exchangers 141, 142 and 143 are illustratively shown as three, but the numbers are illustrative and the number may be more than two or three. The waste heat recovery heat exchangers 141, 142, and 143 are respectively connected to one of the first heating medium discharge pipe 111 and the first heating medium inlet pipe 112 and the valves 1411, 1421, and 1431 . 1, the waste heat recovering heat exchangers 141, 142, and 143 are connected to the first heating medium discharge pipe 111 through the valves 1411, 1421, and 1431, May be connected to the pipe 112.

The plurality of waste heat recovery heat exchangers 141, 142, and 143 may be installed in a hot water boiler that cools the turbine in a thermal power plant and is discarded in the sea, or may be installed in a chimney of a waste incinerator.

The indoor heat exchanger (150) includes a plurality of indoor heat exchangers (151, 152, 153) to supply heat to the greenhouse. In FIG. 1, three of the indoor heat exchangers 150 are illustrated by way of example, but the number may be more than two or three. The indoor heat exchangers 151, 152 and 153 are connected to the second heating medium discharge pipe 113 and the second heating medium inlet pipe 114, respectively.

The first temperature sensor 160 is installed at a location where the waste heat recovery heat exchange unit is installed. That is, the first temperature sensor 160 may be installed in a hot water discharged from the thermal power plant by cooling the turbine and discarded in the sea, or installed in a chimney of the incinerator.

The second temperature sensor 170 is installed in the thermal storage tank 110. The third temperature sensor 180 is installed outside the greenhouse. The fourth temperature sensor 190 is installed inside the greenhouse.

The controller 1000 controls the first pump, the second pump, and the valves according to the temperatures sensed by the first through fourth temperature sensors 160, 170, 180, and 190.

The control unit 1000 controls the number of the valves 1411, 1421, and 1431 to be opened as the temperature difference between the first temperature sensor 160 and the second temperature sensor 170 increases, It is possible to control to open a predetermined number of valves. That is, the controller 1000 stores a table in which the temperature of the first temperature sensor 160 is set in accordance with the range of the temperature difference of the second temperature sensor 170, Therefore, the valves can be controlled. That is, when the temperature difference is large, a large number of valves are opened to absorb heat, and if the temperature difference is not large, the valve is opened at the minimum number, and if the temperature difference is not greater than the set value, all the valves are closed to block the flow of heat medium.

At this time, the temperature of the first temperature sensor 160 is lower than the temperature difference of the second temperature sensor 170 and the number of open valves, and the position of the first heat medium discharge pipe 111 and the first heat medium inlet pipe < The length of the first heat medium discharge pipe 112 and the temperature at which the first heat medium discharge pipe 111 and the first heat medium discharge pipe 112 are installed. That is, the length of the first heating medium discharge pipe 111 and the first heating medium inlet pipe 112 is long and the temperature of the place where the first heating medium discharge pipe 111 and the first heating medium inlet pipe 112 are installed is A small number of valves are opened even when the temperature of the first temperature sensor 160 is low and the temperature difference of the second temperature sensor 170 is large. On the contrary, when the temperature of the first heating medium discharge pipe 111 When the length of the first heating medium inlet pipe 112 is short and the temperature at the place where the first heating medium discharge pipe 111 and the first heating medium inlet pipe 112 are installed is relatively high, A large number of valves can be opened.

At this time, the controller 1000 determines that the temperature difference between the first temperature sensor 160 and the second temperature sensor 170 is larger, that is, as the number of valves is increased, The first pump 120 may be controlled to be driven at a predetermined speed so that the heating medium is circulated. That is, when a large number of valves are opened, the flow rate of the heating medium is lowered, so that the first pump 120 is strongly driven to increase the flow rate again.

The control unit 1000 controls the first and second temperature sensors 180 and 190 so that the temperature of the third temperature sensor 180 is driven at a predetermined speed so that the heating medium is circulated as the temperature difference increases, The second pump 130 can be controlled.

At this time, the controller 1000 determines whether the temperature of the third temperature sensor 180 is higher than the temperature of the fourth temperature sensor 190, regardless of the temperature difference of the fourth temperature sensor 190, Can be driven.

It is judged that the heating load of the greenhouse is very large when the temperature difference is very large, by using the fourth temperature sensor 190 installed in the greenhouse and the third temperature sensor 180 installed outside the greenhouse, The speed of the second pump 130 for controlling the flow of the heating medium flowing to the greenhouse side in the state where all of the indoor indoor heat exchangers 151, 152, and 153 are operated is increased so that a large amount of the heating medium flows, . On the other hand, when the heating load of the greenhouse is decreased, the speed of the second pump (130) for controlling the flow of the heating medium flowing to the greenhouse side is reduced to allow a small amount of heating medium to flow to cope with a small heating load. The ON and OFF controls of the fan motors of the fans 151, 152 and 153 and the control of the flow rate of the heating medium by the valves (not provided in FIG. 1) The temperature of the greenhouse is suddenly changed when the flow rate of the heating medium is controlled by a valve (not provided in FIG. 1) by controlling the fan motor of the greenhouse The thermal environment changes cause the thermal stress of the crop and the fan motor is turned off so that the air flow inside the greenhouse which is maintained at the proper wind speed and proper temperature by the operation of the fan motor is broken, foot Therefore, when the greenhouse is heated, the indoor heat exchangers 151, 152, and 153 are all operated, and only the flow rate of the heating medium is changed to the greenhouse Is more advantageous in the formation of a greenhouse thermal environment which is more pleasant, and it is intended to improve the growth condition of the crop.

2 is a schematic diagram showing a waste heat recovery system according to another exemplary embodiment of the present invention. The embodiment shown in FIG. 2 is a waste heat recovery system in the case of cooling and heating using a device that absorbs waste heat such as a heat pump without using waste heat directly for heating.

2, a waste heat recovery system 200 according to another exemplary embodiment of the present invention includes a heat pump 290, a heat storage tank 210, a first pump 220, a second pump 230, A pump 310, a waste heat collecting heat exchanging unit 240, an indoor heat exchanging unit 250, a first temperature sensor 260, a second temperature sensor 270, a third temperature sensor 280, 1000).

The heat pump 290 is connected to the first heating medium discharge pipe 211 and the first heating medium inlet pipe 212.

The thermal storage tank 210 is a tank in which a thermal medium is stored. The heating medium may be water, but is not limited thereto, and other media may be used. The heat storage tank 210 is connected to the second heat medium discharge pipe 213 and the second heat medium inlet pipe 214 and is connected to the heat pump 290 and the first connection pipe 215 and the second connection pipe 216 .

The first pump 220 is installed in the first heat medium discharge pipe 211. Alternatively, the first pump 220 may be installed in the first heating medium inlet pipe 212.

The second pump 230 is installed in the second heating medium discharge pipe 213. Alternatively, the second pump 230 may be installed in the second heat medium inlet pipe 214.

The third pump 310 is installed in the second connection pipe 216. Alternatively, the third pump 310 is installed in the first connection pipe 215.

The waste heat recovery heat exchanger 240 includes a plurality of waste heat recovery heat exchangers 241, 242, and 243, and is capable of performing heat exchange from the industrial waste heat in accordance with the opening and closing of the valve. In FIG. 2, the waste heat recovering heat exchangers 241, 242 and 243 are exemplarily shown as three, but this is only an example, and the number may be more than two or three. The waste heat recovery heat exchangers 241, 242 and 243 are respectively connected to one of the first heating medium discharge pipe 111 and the first heating medium inlet pipe 112 and the valves 2411, 2421 and 2431 . 2, the waste heat recovery heat exchangers 241, 242 and 243 are connected to the first heat medium discharge pipe 211 through the valves 2411, 2421 and 2431, May be connected to the pipe 212.

The plurality of waste heat recovery heat exchangers 241, 242 and 243 may be contained in a hot water discharged from the thermal power plant by cooling the turbine and discarded in the sea, or installed in a chimney of a waste incineration facility.

The hot indoor heat exchanging unit 250 includes a plurality of hot indoor heat exchangers 251, 252, and 253 to supply heat to the greenhouse. In FIG. 2, the number of the indoor heat exchange units 250 is illustratively three, but the number of the indoor heat exchange units 250 may be more than two or three. The indoor heat exchangers 251, 252 and 253 are connected to the second heating medium discharge pipe 213 and the second heating medium inlet pipe 214, respectively.

The first temperature sensor 260 is installed at a location where the waste heat recovery heat exchanging part 240 is installed. That is, the first temperature sensor 260 may be installed in the hot water discharged from the thermal power plant by cooling the turbine and discarded in the sea, or installed in the chimney of the incinerator.

The second temperature sensor 270 is installed outside the greenhouse. The third temperature sensor 280 is installed inside the greenhouse.

The controller 1000 controls the first pump 220, the second pump 230, and the valves (not shown) according to the temperatures sensed by the first through third temperature sensors 260, 2411, 2421, and 2431, respectively.

At this time, the controller 1000 sets a predetermined number of valves 2411, 2421, and 2431 to open a smaller number of valves 2411, 2421, and 2431 as the temperature rises according to the temperature of the first temperature sensor 260 ) Can be opened. In the case where the waste heat can not be directly used for heating but the apparatus for absorbing the waste heat such as the heat pump 290 is used for heating and cooling, the temperature of the waste heat is sensed by sensing the temperature of the waste heat through the first temperature sensor 260, The valve 2411 is opened only among the valves 2411, 2421 and 2431 which can control the heating medium flowing to the waste heat recovery heat exchanger in order to realize the waste heat recovery heat exchanger area corresponding to the high capacity of the waste heat, And the other valves 2421 and 2431 are closed. When a device such as the heat pump 290 is used, the waste heat recovering heat exchanger is designed in a state where the heat capacity of waste heat is the smallest at the time of heating. Therefore, when the heat capacity of the waste heat is large, The heat pump 290 becomes unstable due to a state in which the pump 290 is supplied with more heat than required by the heat.

On the other hand, when cooling is performed using the heat pump 290, when the temperature of the waste heat is low and the heat capacity is considered to be small, all the valves 2411, 2421, and 2431 capable of controlling the heating medium are opened, To the waste heat. 2, the cooling / heating control of the greenhouse is controlled by controlling the speed of the second pump 230 that controls the flow of the heating medium, as shown in FIG. 1, thereby controlling the flow rate of the cold water or hot water flowing into the greenhouse, Prevent change.

As described above, according to the waste heat recovery system of the present invention, by appropriately recovering the industrial waste heat and responding to fluctuations in the cooling and heating load of agricultural facilities such as a greenhouse for heating and cooling using industrial waste heat (industrial temperature) By optimizing the temperature environment of agricultural facilities for crop growth, it is possible to produce high quality agricultural products and to reduce heating and cooling costs.

While the present invention has been described in connection with what is presently considered to be practical and exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100, 200: waste heat recovery system
110, 210:
111, 211: first heat medium discharge pipe
112, 212: first heat medium inlet pipe
113, 213: a second heating medium discharge pipe
114, 214: second heat medium inlet pipe
120, 220: first pump
130, 230: Second pump
140, 240: waste heat recovery heat exchanger
141, 142, 143, 241, 242, 243: waste heat recovery heat exchanger
150, 250: an indoor heat exchanger
151, 152, 153, 251, 252, 253: an indoor heat exchanger
160, 260: first temperature sensor
170, 270: a second temperature sensor
180, 280: third temperature sensor
190: fourth temperature sensor
290: Heat pump
310: Third pump
1000:

Claims (7)

A heat storage tank connected to the first heating medium discharge pipe, the first heating medium inlet pipe, the second heating medium discharge pipe and the second heating medium inlet pipe, and storing the heating medium;
A first pump installed in the first heating medium discharge pipe or the first heating medium inlet pipe;
A second pump installed in the second heating medium discharge pipe or the second heating medium inlet pipe;
And a plurality of waste heat recovery heat exchangers connected to either one of the first heat medium discharge pipe and the first heat medium discharge pipe through a valve so that the waste heat A recovery heat exchanger;
An on-room heat exchanger including a plurality of indoor heat exchangers connected to the second heat medium discharge pipe and the second heat medium inlet pipe, respectively, for supplying heat to the greenhouse;
A first temperature sensor installed at a location where the waste heat recovery heat exchange unit is installed;
A second temperature sensor provided in the thermal storage tank;
A third temperature sensor installed outside the greenhouse;
A fourth temperature sensor installed inside the greenhouse; And
A controller for controlling the first pump, the second pump, and the valves according to the temperatures sensed by the first through fourth temperature sensors;
, ≪ / RTI &
Wherein the control unit opens a predetermined number of valves so that the larger the temperature difference is, the larger the number of the valves is opened, in accordance with the temperature difference between the first temperature sensor and the second temperature sensor.
delete The method according to claim 1,
Wherein the control unit controls the first pump so that the heating medium is driven at a predetermined speed so that the heating medium is circulated as the temperature difference increases as the temperature of the first temperature sensor increases according to the temperature difference of the second temperature sensor. Recovery system.
The method according to claim 1,
Wherein the controller controls the second pump such that the temperature of the third temperature sensor is driven at a predetermined speed so that the heating medium is circulated as the temperature difference increases as the temperature difference of the fourth temperature sensor increases, Recovery system.
5. The method of claim 4,
Wherein the control unit drives all the plurality of on-air heat exchangers regardless of the temperature difference of the third temperature sensor.
delete delete

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