JP2685299B2 - Multi-room air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a refrigerant cycle of a multi-room air conditioner.

2. Description of the Related Art A conventional multi-chamber cooling / heating apparatus separated into a heat source side refrigerant cycle and a use side refrigerant cycle is disclosed in JP-A-62-272040.

Hereinafter, the conventional multi-room air conditioner will be described with reference to the drawings.

In FIG. 2, 11 is a compressor, 12 is a four-way valve, 13 is a heat source side heat exchanger, 14 is a cooling decompression device, 15 is a heating decompression device, and 16 is a heating cooling decompression device 14. Check valve, 17
Is a check valve that closes the decompression device 15 for heating during cooling, and 18 is the first
It is an auxiliary heat exchanger, and these are connected in a ring to form a heat source side refrigerant cycle.

Reference numeral 19 denotes a second auxiliary heat exchanger, which is formed integrally with the first auxiliary heat exchanger 18 so as to exchange heat. Reference numeral 20 denotes a refrigerant amount adjusting tank for adjusting the amount of refrigerant during cooling and during heating. Reference numeral 21 denotes a refrigerant transfer device, which has a reversibility in which the refrigerant outflow directions are opposite during cooling and during heating, and these are stored in the outdoor unit f. 22a and 22b are use side heat exchangers housed in the indoor units g and h, and connected to the outdoor unit f by connection pipes i, i ', j and j'. Then, the second auxiliary heat exchanger 19, the refrigerant amount adjustment tank 20, the refrigerant transfer device 21, the use side heat exchangers 22a and 22b and the connection pipes i, i ′, j, j ′ are connected in an annular shape to the use side refrigerant. Forming a cycle.

The operation of the multi-room air conditioner configured as above will be described below.

During the cooling operation, the refrigerant cycle is indicated by the solid arrow in the figure.In the heat source side refrigerant cycle, the high temperature and high pressure gas refrigerant from the compressor 11 passes through the four-way valve 12 and radiates heat in the heat source side heat exchanger 13 to be condensed and liquefied. The pressure is reduced by the cooling expansion valve 14 through the stop valve 16, evaporated in the first auxiliary heat exchanger 18, passed through the four-way valve 12, and circulated to the compressor 11. At this time, the second auxiliary heat exchanger 19 and the first auxiliary heat exchanger 18 of the use side refrigerant cycle exchange heat, the gas refrigerant in the use side refrigerant cycle is cooled and liquefied, and passes through the refrigerant amount adjusting tank 20. It is sent to the refrigerant transfer device 21, and by this refrigerant transfer device 21 passes through the connection pipes i, j and the use side heat exchangers 22a, 2
It is sent to 2b where it is absorbed and vaporized, gasified, and connected pipes i ', j'
And circulates to the second auxiliary heat exchanger 19.

On the other hand, during the heating operation, the refrigerant cycle is indicated by the broken line arrow in the figure, and in the heat source side refrigerant cycle, the high-temperature and high-pressure gas refrigerant from the compressor 11 flows from the four-way valve 12 to the first auxiliary heat exchanger.
After being sent to 18, the heat is radiated to condense and liquefy, and the pressure is reduced from the check valve 17 by the heating expansion valve 15, absorbed and evaporated by the heat source side heat exchanger 13, and circulated to the compressor 11 through the four-way valve 12. At this time, the second auxiliary heat exchanger 19 and the first auxiliary heat exchanger 18 of the use side refrigerant cycle exchange heat, the liquid refrigerant in the use side refrigerant cycle is heated and gasified, and the connecting pipes i ′, j ′ are connected. Through heat exchanger 22
It is sent to a, 22b, heated and radiated to liquefy heat, sent to the refrigerant transfer device 21 through the connection pipes i, j, and circulated from the refrigerant amount adjusting tank 20 to the second auxiliary heat exchanger 19.

However, in the above-mentioned configuration, the maximum capacity is limited, and the apparatus capacity must correspond to the peak load. Therefore, the equipment capacity becomes large, the initial cost and the running cost increase, and there is a problem that energy saving is not achieved.

In view of the above problems, the present invention provides a multi-room cooling and heating apparatus that includes a device that copes with a short-time peak load and that saves energy as well as reduces the initial cost and running cost by reducing the facility capacity.

Means for Solving the Problems In order to solve the above problems, the present invention provides a heat source side formed by connecting a compressor, a four-way valve, a heat source side heat exchanger, a cooling / heating decompression device, and a first auxiliary heat exchanger in an annular shape. A refrigerant cycle,
A second auxiliary heat exchanger that is integrally formed with the first auxiliary heat exchanger to exchange heat, a refrigerant transfer device that changes the outflow direction of the refrigerant during cooling and heating, and a plurality of utilization-side heat exchangers that are connected in an annular shape. In the multi-chamber cooling and heating device using a refrigerant that changes its state into a liquid state and a gas state in the usage-side refrigerant cycle as a refrigerant of the usage-side refrigerant cycle, a three-way switching means is provided. Utilizing a heat storage heat exchanger connected in parallel with the first auxiliary heat exchanger via the three-way flow valve for adjusting the flow ratio in two directions to radiate the stored heat in parallel with the second auxiliary heat exchanger. Side heat radiating heat exchanger is connected, and a heat source side radiating heat exchanger is connected between the heat source side heat exchanger and the cooling / heating decompression device via a three-way switching means, and the heat storage heat exchanger is For the heat exchanger for heat radiation on the use side and for heat radiation on the heat source side Than is provided with a heat storage tank with exchanger.

Effect The present invention has the above-described configuration, and switches the three-way switching means from the flow path that passes through the first auxiliary heat exchanger to the flow path that passes through the heat storage heat exchanger at night to operate only the heat source side refrigerant cycle in the heat storage tank. The heat storage material is heated or cooled to store heat, and at the time of peak load, a part of the refrigerant in the use side refrigerant cycle is sent to the use side heat radiation heat exchanger to exchange heat with the heat storage material in the heat storage tank. The cooling and heating capacity of the usage-side refrigerant cycle can be increased by sending the remaining refrigerant in the usage-side refrigerant cycle to the second auxiliary heat exchanger for heat exchange with the first auxiliary heat exchanger.

At this time, if the three-way switching means is switched so that the refrigerant in the heat source side refrigerant cycle passes through the heat source side heat radiation heat exchanger, the heat exchange capacity of the first auxiliary heat exchanger increases, and the first auxiliary heat exchanger increases. The amount of heat exchange in the second auxiliary heat exchanger of the usage-side refrigerant cycle that exchanges heat with the exchanger is increased, and further the cooling / heating capacity of the usage-side refrigerant cycle can be increased.

Also, when cooling and heating of the usage-side refrigerant cycle can be performed only by exchanging heat with the heat storage material in the heat storage tank, the operation of the heat source-side refrigerant cycle is stopped, and all the refrigerant in the usage-side refrigerant cycle is released to the usage-side heat dissipation heat. By sending to the exchanger and exchanging heat with the heat storage material in the heat storage tank, there is no unnecessary heat dissipation or heat absorption in the second auxiliary heat exchanger, and there is no consumption of energy for operating the heat source side refrigerant cycle. Therefore, it is possible to save energy and efficiently perform heating and cooling. Further, it is possible to perform heating / cooling operation in a cycle that does not use the heat storage tank as in the conventional case.

As described above, the multi-room cooling and heating apparatus of the present invention can cope with a peak load for a short time, can reduce the capacity of the compressor to have a small installation capacity, and thus can reduce the initial cost and the running cost and save energy. Has an effect on.

Example Hereinafter, a multi-room air conditioner of one embodiment of the present invention will be described.
This will be described with reference to the drawings. FIG. 1 shows a refrigerant cycle diagram of the multi-room air conditioner of the present invention.

In the figure, 23 is a heat storage tank, which is filled with a heat storage material such as water inside, and a heat storage heat exchanger 24 for exchanging heat with the heat storage material, and also for exchanging heat with the heat storage material to radiate the stored heat. Side heat dissipation heat exchanger 25a provided in the side refrigerant cycle and heat source side heat dissipation heat exchanger 25b provided in the heat source side refrigerant cycle
It has.

Reference numerals 26a and 26b denote three-way switching valves for switching the refrigerant flow path to the first auxiliary heat exchanger 18 and the refrigerant flow path to the heat storage heat exchanger 24, and 27
a and 27b are the second auxiliary heat exchanger 19 and the user side heat radiation heat exchanger 2
Three-way flow valve to adjust the two-way refrigerant flow ratio to 5a, 28
a and 28b are refrigerant flow passages in which the heat source side heat radiating heat exchanger 25b is interposed between the heat source side heat exchanger 13 and the cooling decompression device 14 and the heating decompression device, or refrigerant passages which are not interposed. This is a three-way switching valve that switches between

The operation of the multi-room air conditioner configured as above will be described below.

When preparing for the peak load of cooling when there is no need for cooling at night or the like, heat storage operation is performed in which only the heat source side refrigerant cycle is operated in the cycle indicated by the solid line arrow in the figure. At this time, the refrigerant from the compressor 11 passes through the four-way valve 12 and the heat source side heat exchanger 13
It is cooled and condensed into a liquefied liquid, and passes through the check valve 16 to expand the cooling valve.
It is decompressed at 14, passes through the three-way switching valve 26a, and the heat storage heat exchanger 24
Flow through the three-way switching valve 26b and the four-way valve 12 through the three-way switching valve 26b.
To compressor 11. As a result, the heat storage material in the heat storage tank 23 is cooled to about 0 ° C. to store heat.

Then, at the peak load of cooling, in the heat source side refrigerant cycle, the three-way switching valves 26a, 26b are switched to perform the cooling operation of the cycle indicated by the solid arrow in the figure in which the first auxiliary heat exchanger 18 is used as the evaporator. The switching valves 28a and 28b are switched, the refrigerant from the heat source side heat exchanger 13 is caused to flow into the heat source side heat radiation heat exchanger 25b, and the heat storage is cooled to about 0 ° C. by the nighttime heat storage operation in the heat source side heat radiation heat exchanger 25b. The material is heat-exchanged for cooling, the degree of supercooling is increased, the enthalpy difference of the refrigerant is increased, and the cooling capacity of the first auxiliary heat exchanger 18 is improved.

On the other hand, in the use side refrigerant cycle, as shown by the solid line arrow in the figure, the refrigerant from the refrigerant transfer device 21 is sent to the use side heat exchangers 22a, 22b through the connection pipes i, j, and the use side heat is transferred. In the exchangers 22a and 22b, they are endothermicly evaporated, gasified, and sent to the three-way flow valve 27a through the connecting pipes i'and j '. A part of the refrigerant sent to the three-way flow valve 27a is part of the heat radiating heat exchanger 25a on the use side.
And the remaining refrigerant is sent to the second auxiliary heat exchanger 19. The flow rate ratio between the amount of refrigerant sent to the heat radiating side for heat utilization 25a and the amount of refrigerant sent to the second auxiliary heat exchanger 19 is adjusted by the three-way flow valves 27a, 27b according to the load. The refrigerant sent from the three-way flow valve 27a to the heat radiating heat exchanger 25a on the use side is cooled by exchanging heat with the heat storage material cooled to about 0 ° C. by the heat storage operation at night in the heat radiating heat exchanger 25a on the use side. The refrigerant that is condensed and liquefied and sent to the three-way flow valve 27b and sent from the three-way flow valve 27a to the second auxiliary heat exchanger 19 exchanges heat with the first auxiliary heat exchanger 18 in the second auxiliary heat exchanger 19. By cooling and condensing and liquefying, the three-way flow valve
Sent to 27b. Then, the refrigerant merged by the three-way flow valve 27b circulates from the refrigerant amount adjustment tank 20 to the refrigerant transfer device 21.

Therefore, at this time, the cooling capacity of the use-side refrigerant cycle is
The heat exchanger 25 for radiating the refrigerant from the heat source side heat exchanger 13 to the heat source side
The cooling capacity by the heat radiating heat exchanger 25a is added to the cooling capacity by the first auxiliary heat exchanger 18 of the heat source side refrigerant cycle whose capacity is improved by flowing it to b to increase the supercooling degree, It can handle peak load of cooling.

Further, when preparing for the peak load of heating when there is no need for heating, heat storage operation is performed in which only the heat source side refrigerant cycle is operated in the cycle indicated by the dashed arrow in the figure. At this time, the compressor
11, the refrigerant from the four-way valve 12 is sent from the three-way switching valve 26b to the heat storage heat exchanger 24, where it exchanges heat with the heat storage material to cool, condense and liquefy, and then the three-way switching valve 26a. The pressure is reduced by the heating expansion valve 15 through the check valve 17, absorbed and evaporated by the heat source side heat exchanger 13, and circulated from the four-way valve 12 to the compressor 11. As a result, the heat storage material in the heat storage tank 23 is heated to store heat.

Then, during the heating peak load, in the heat source side refrigerant cycle, the three-way switching valves 26a, 26b are switched to perform the heating operation in the cycle indicated by the broken line arrow in the drawing in which the first auxiliary heat exchanger 18 is the condenser, and The switching valves 28a, 28b are switched to flow the refrigerant from the heating expansion valve 15 into the heat source side heat radiation heat exchanger 25b,
In the heat exchanger 25b for radiating heat on the heat source side, heat is exchanged with the heat storage material that has been heated by the heat storage operation and is in a high temperature state for heating, and the evaporation capacity is improved and the heating capacity in the first auxiliary heat exchanger 18 is improved. .

On the other hand, in the usage-side refrigerant cycle, the refrigerant from the refrigerant transfer device 21 is sent from the refrigerant amount adjustment tank 20 to the three-way flow valve 27b, as indicated by the dashed arrow in the figure. A part of the refrigerant sent to the three-way flow valve 27b is sent to the utilization side heat radiation heat exchanger 25a, and the remaining refrigerant is sent to the second auxiliary heat exchanger 19. In addition, the amount of the refrigerant sent to the heat radiating heat exchanger 25a on the use side and the second
The flow rate ratio of the amount of refrigerant sent to the auxiliary heat exchanger 19 is adjusted by the three-way flow valves 27a and 27b according to the load. Three-way flow valve 27b
The refrigerant sent from the user-side heat radiation heat exchanger 25a to the user-side heat-radiation heat exchanger 25a is heated by heat exchange with the heat storage material that is in a high temperature state due to the heat storage operation in the user-side heat radiation heat exchanger 25a and is endothermic vaporized and gasified. The refrigerant sent to the three-way flow valve 27a and sent from the three-way flow valve 27b to the second auxiliary heat exchanger 19 is heated by exchanging heat with the first auxiliary heat exchanger 18 in the second auxiliary heat exchanger 19. It is endothermically evaporated and gasified, and sent to the three-way flow valve 27a. Then, the refrigerants joined by the three-way flow valve 27a pass through the connecting pipes i ', j', and the use side heat exchangers 22a, 22 '.
It is sent to b, is radiatively condensed and liquefied in the use side heat exchangers 22a and 22b, and circulates to the refrigerant transfer device 21 through the connection pipes i and j.

Therefore, at this time, the heating capacity of the use-side refrigerant cycle is
The heat exchanger 25b for radiating the refrigerant from the heating expansion valve 15 to the heat source side
The heating capacity by the first auxiliary heat exchanger 18 of the heat source side refrigerant cycle, which is improved by increasing the evaporation capacity by flowing the heat to the heating capacity by the heat dissipation heat exchanger 25a, adds the heating peak. Can handle loads.

Further, when the peak load of cooling and heating is not so large and it is not necessary to improve the cooling and heating capacity of the first auxiliary heat exchanger 18 in the heat source side refrigerant cycle more than usual, the refrigerant does not flow to the heat source side heat radiating heat exchanger 25b. So that the three-way switching valve 28a, 28b
Switch. In this case, since the heat storage by the heat source side heat radiating heat exchanger 25b is not consumed, the time when the heat radiating heat exchanger 25a can take out the heat storage can be lengthened.

In addition, the three-way switching valves 28a, 28b are switched so that the refrigerant flows through the heat-source-side heat-radiating heat exchanger 25b, and the three-way flow valve 27a so that all the refrigerant in the usage-side refrigerant cycle is sent to the second auxiliary heat exchanger 19. , 27b, heat cannot be directly taken out in the use-side refrigerant cycle, but the first auxiliary heat exchanger in the heat-source-side refrigerant cycle has improved capacity by heat exchange in the heat-source-side heat dissipation heat exchanger 25b. The heating / cooling capacity of 18 can be used for a long time for cooling / heating of the user side refrigerant cycle.

Further, when cooling and heating of the use side refrigerant cycle can be performed only by heat exchange with the heat storage material in the heat storage tank 23, the operation of the heat source side refrigerant cycle is stopped, and the refrigerant in the use side refrigerant cycle is controlled by the three-way flow valves 27a, 27b. The heat exchanger for heat radiation 25a
To heat exchange with the heat storage material in the heat storage tank 23. In this case, since the refrigerant does not flow to the second auxiliary heat exchanger 19,
Since there is no unnecessary heat dissipation or heat absorption in the second auxiliary heat exchanger 19 and no energy is consumed for operating the heat source side refrigerant cycle, it is possible to save energy and efficiently perform heating / cooling.

When heat is not stored or when all the heat is consumed, the flow of refrigerant becomes the same as in FIG. 2 by the three-way switching valves 26a, 26b, three-way flow valves 27a, 27b, and three-way switching valves 28a, 28b. You can

As described above, the heat storage stored in the heat storage material in the heat storage tank 23 in the heat storage operation has been described to be used according to the size of the cooling / heating load.However, if the heat storage is used at the time of startup, the startup characteristics can be improved. it can. Further, when frost is formed on the heat source side heat exchanger 13 of the heat source side refrigerant cycle in the heating operation,
By switching the three-way switching valves 28a, 28b so that the refrigerant flows through the heat source side heat radiating heat exchanger 25b, and flowing the refrigerant heated by the heat source side heat radiating heat exchanger 25b to the heat source side heat exchanger 13, the heat source The frost on the side heat exchanger 13 can be quickly thawed.

In this embodiment, the heat storage tank 23 is provided in the outdoor unit f, but the heat storage tank 23 may be provided outside the outdoor unit f. Further, a capacity control type compressor can be used for the compressor 11. Further, the refrigerant used in the heat source side refrigerant cycle and the refrigerant used in the utilization side refrigerant cycle can be different. Further, the first auxiliary heat exchanger 18 and the second auxiliary heat exchanger 19 can be configured as a laminated heat exchanger.

As described above, in the present embodiment, the heat storage heat exchanger 24 is connected in parallel with the first auxiliary heat exchanger 18 via the three-way switching means 26a, 26b, and the three-way flow valve 27a for adjusting the two-way flow rate ratio is used. , 27b
A heat exchanger 25a for radiating the stored heat is connected in parallel with the second auxiliary heat exchanger 19 through the three-way switching means 28a, 28b.
The heat source side heat exchanger 13 and the cooling and heating decompression devices 14, 15 are connected to the heat source side heat radiation heat exchanger 25b, and the heat storage heat exchanger 24 and the use side heat radiation heat exchanger 25a and the heat source. By providing the heat storage tank 23 having the side heat radiating heat exchanger 25b, the heat storage heat exchanger 24 heats or cools the heat storage material in the heat storage tank 23 to store heat when there is no need for heating and cooling in advance such as at night. Aside
When the peak load is relatively large, both the use side heat dissipation heat exchanger 25a and the heat source side heat dissipation heat exchanger 25b, and when the peak load is relatively small, the use side heat dissipation heat exchanger 25b
It is possible to increase the cooling / heating capacity of the usage-side refrigerant cycle by taking out heat from either a or the heat-source-side heat-dissipating heat exchanger 25b to cope with a short-time peak load. Therefore, the compressor 11 can be made to have a small capacity and the equipment capacity can be made small, so that the initial cost and the running cost can be reduced and the energy can be saved.

Further, when cooling and heating of the use side refrigerant cycle can be performed only by heat exchange with the heat storage material in the heat storage tank 23, the operation of the heat source side refrigerant cycle is stopped, and all the refrigerant in the use side refrigerant cycle is used for the use side heat radiation. By sending to the heat exchanger 25a, there is no unnecessary heat dissipation or heat absorption in the second auxiliary heat exchanger 19, and there is no energy consumption for operating the heat source side refrigerant cycle, so energy-saving and efficient cooling and heating Will be possible.

Further, by utilizing the heat storage at startup, it is possible to improve the rising characteristics, and by flowing the refrigerant heated by the heat source side heat radiation heat exchanger 25b during the heating operation to the heat source side heat exchanger 13, The frost on the heat source side heat exchanger 13 can be quickly thawed while maintaining the heating operation.

EFFECTS OF THE INVENTION As described above, according to the present invention, the heat storage heat exchanger is connected in parallel with the first auxiliary heat exchanger via the three-way switching means, and the three-way flow valve for adjusting the flow rate ratio in the two directions is used. 2 A heat exchanger for heat radiation on the use side for radiating heat storage is connected in parallel with the auxiliary heat exchanger, and a heat exchanger for heat radiation on the heat source side is provided between the heat exchanger on the heat source side and the decompressor for cooling and heating via the three-way switching means. By providing a heat storage tank having the heat storage heat exchanger, the use side heat radiation heat exchanger, and the heat source side heat radiation heat exchanger.
When there is no need for heating and cooling at night, etc., the heat storage heat exchanger heats or cools the heat storage material in the heat storage tank to store heat in advance.
When the peak load is relatively large, both the heat exchanger for heat radiation on the usage side and the heat exchanger for heat radiation on the heat source side, and when the peak load is relatively small, the heat exchanger for heat radiation on the usage side and heat radiation for heat source side. By extracting heat from either one of the exchangers, the cooling / heating capacity of the use-side refrigerant cycle can be increased to cope with peak load for a short time. Therefore, since the capacity of the compressor can be reduced to a small capacity, the initial cost and the running cost can be reduced, and energy can be saved.

Also, when cooling and heating of the usage-side refrigerant cycle can be performed only by exchanging heat with the heat storage material in the heat storage tank, the operation of the heat source-side refrigerant cycle is stopped, and all the refrigerant in the usage-side refrigerant cycle is released to the usage-side heat dissipation heat. By sending to the exchanger, there is no unnecessary heat dissipation or heat absorption in the second auxiliary heat exchanger, and there is no energy consumption for operating the heat source side refrigerant cycle, so energy-saving and efficient cooling and heating are possible. Become.

In addition, by using the heat storage at startup, it is possible to improve the rising characteristics, and by flowing the refrigerant heated by the heat source side heat radiation heat exchanger to the heat source side heat exchanger during heating operation, While maintaining the above, the frost on the heat source side heat exchanger can be quickly thawed.

[Brief description of the drawings]

FIG. 1 is a refrigerant cycle diagram of a multi-room air conditioner in one embodiment of the present invention, and FIG. 2 is a refrigerant cycle diagram of a conventional multi-room air conditioner. 13 ... heat source side heat exchanger, 18 ... first auxiliary heat exchanger, 19 ...
… Second auxiliary heat exchanger, 21 …… Refrigerant carrier, 22a, 22b…
… Use side heat exchanger, 23 …… Heat storage tank, 24 …… Heat storage heat exchanger, 25a …… Use side heat dissipation heat exchanger, 25b …… Heat source side heat dissipation heat exchanger.

Claims (4)

(57) [Claims] 1. A heat source side refrigerant cycle comprising a compressor, a four-way valve, a heat source side heat exchanger, a cooling / heating decompression device and a first auxiliary heat exchanger connected in an annular shape, and a first auxiliary heat exchanger. A second auxiliary heat exchanger that forms and heat-exchanges with each other, a refrigerant transfer device that changes the outflow direction of the refrigerant during cooling and heating, and a usage-side refrigerant cycle that is formed by connecting a plurality of usage-side heat exchangers in an annular shape, A heat storage heat exchanger connected in parallel with the first auxiliary heat exchanger via a three-way switching means, and a second auxiliary heat exchanger in parallel via a three-way flow valve for adjusting a flow ratio in two directions. A heat exchanger for heat radiation on the use side for radiating the stored heat, and a heat exchanger for heat radiation on the heat source side connected between the heat source side heat exchanger and the cooling / heating decompression device via a three-way switching means, The heat exchanger for heat storage, the heat exchanger for heat radiation on the use side, and the heat radiation on the heat source side And a thermal storage tank having a heat exchanger, a multi-chamber air conditioner using the refrigerant changes state to a liquid state and a gas state at the use-side in the refrigerant cycle as the refrigerant in the use-side refrigerant cycle. 2. The multi-room cooling and heating apparatus according to claim 1, wherein the compressor is equipped with a capacity control compressor. 3. The multi-room cooling and heating apparatus according to claim 1, wherein different refrigerants are used in the heat source side refrigerant cycle and the use side refrigerant cycle. 4. The multi-room cooling and heating apparatus according to claim 1, wherein a laminated heat exchanger is used for the first auxiliary heat exchanger and the second auxiliary heat exchanger.