US20210003327A1

US20210003327A1 - Heat exchange apparatus, heat exchange method, and air conditioning system

Info

Publication number: US20210003327A1
Application number: US16/982,790
Authority: US
Inventors: Koichi TODOROKI; Minoru Yoshikawa; Kunihiko Ishihara; Masaki Chiba; Yoshinori Miyamoto; Takafumi NATSUMEDA; Nirmal Singh RAJPUT
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2018-03-29
Filing date: 2019-03-20
Publication date: 2021-01-07
Also published as: JPWO2019188634A1; WO2019188634A1; JP7047899B2

Abstract

In order to efficiently distribute a heat medium at a low heat medium pressure, a heat exchange apparatus includes a heat exchange pipe 2 configured to accommodate a heat medium L to be evaporated by heat absorption from a gas to be cooled, the heat exchange pipe being disposed in an inclined state, a supply pipe 1 configured to supply the heat medium L in a liquid-phase state, the supply pipe being placed in a vicinity of a lower part of the heat exchange pipe 2, a discharge pipe 3 configured to receive a heat medium L to be evaporated in the heat exchange pipe 2 and discharged from an upper part of the heat exchange pipe, and a connecting pipe 4 placed, directing downward, between an upper part of the heat exchange pipe 2 and the discharge pipe 3.

Description

TECHNICAL FIELD

The present invention relates to a heat exchange apparatus, a heat exchange method, and an air conditioning system.

BACKGROUND ART

In an air conditioning system for a data center and the like, in order to receive heat depending on a heating value differing from one heat source to another, a method of arranging local heat receiving units for absorbing heat from the heat source in a row on a server rack may be adopted for each server rack to accommodate heat source such as a server.
PTL 1 describes a technique as a technique related to an air conditioner provided with such a local heat receiving unit.
In the air conditioner, a configuration is adopted in such a way that main-flow-liquid-refrigerant piping for supplying a liquid refrigerant and main-flow-vapor-refrigerant piping for returning a vapor refrigerant generated from absorbing discharged heat and being vaporized are installed in a server room, and a liquid pipe and a vapor pipe of a local heat receiving unit are connected to those main flow pipes.
In the above-described air conditioner, cooling of the server room is performed by circulating the refrigerant through the refrigerant piping, and thus by directly or indirectly discharging heat generated by the server to an outside of a building.
The refrigerant to be used herein is, for example, R134a or R410a, which are developed as substitutes for chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC). When these refrigerants are used, a saturated vapor pressure may rise to nearly 10 atm at a room temperature, similarly to a general air conditioner.

CITATION LIST

Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No. 2013-221634

SUMMARY OF INVENTION

Technical Problem

However, piping of an air conditioner using such a high-pressure refrigerant requires a high-pressure resistant member having high strength and high precision for a pipe, a joint, a valve, packing, and the like. Further, during installation work for the piping and replacement work for the local heat receiving unit, reliable construction including completion inspection under supervision of a qualified person may be required, based on the High Pressure Gas Safety Act, the Industrial Safety and Health Act, and the like.
In other words, there is a problem that time and cost required for facility work increase due to a use of the refrigerant having a high saturated vapor pressure. Further, it is extremely difficult and especially costly to install the local heat receiving unit in a server room where many racks are arranged in a row, while safety for a person and a server is taken into consideration.
Even after the completion, when urgent maintenance is required, it may be difficult to quickly perform construction under control of a qualified person, and there may be a lack of emergency responsiveness at a data center where it is necessary to protect a server and data entrusted by a customer.
The present invention has been made in view of the above-described circumstance, and an object thereof is to provide a heat exchange apparatus, an air conditioning system, and a heat exchange method that enable a heat medium to efficiently flow at a low pressure of the heat medium.

Solution to Problem

In order to solve the above-described problem, the present invention proposes the following means.
A heat exchange apparatus according to a first aspect of the present invention includes a heat exchange pipe configured to accommodate a heat medium to be evaporated by heat absorption from a gas to be cooled, the heat exchange pipe being disposed in an inclined state; a supply pipe configured to supply the heat medium in a liquid-phase state, the supply pipe being placed in a vicinity of a lower part of the heat exchange pipe; a discharge pipe configured to receive a heat medium to be evaporated in the heat exchange pipe and discharged from an upper part of the heat exchange pipe; and a connecting pipe placed, directing downward, between an upper part of the heat exchange pipe and the discharge pipe.
A heat exchange method according to a second aspect of the present invention includes a step of supplying a heat medium in a liquid-phase state at a flow rate higher than a flow rate required for absorbing a heating value of a heat source by a predetermined amount, depending on the heating value; a step of distributing the heat medium supplied in a liquid-phase state to a plurality of heat exchange units; and a step of changing the heat medium distributed in a liquid-phase state into a gas-phase state by heat from the heat source, and discharging, together with the heat medium in a liquid-phase state, the heat medium in a gas-phase state having absorbed heat.

Advantageous Effects of Invention

The present invention enables the heat medium generated in the heat exchange pipe in a mixed state of gas phase and liquid phase to flow, even when the heat medium has low pressure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a piping diagram of a heat exchange apparatus according to a minimum configuration of the present invention.

FIG. 2 is a flowchart of a heat exchange method according to the minimum configuration of the present invention.

FIG. 3 is a perspective view of a heat exchange apparatus according to a first example embodiment of the present invention.

FIG. 4(a) is a front view illustrating details of the heat exchange apparatus according to the first example embodiment of the present invention.

FIG. 4(b) is a side elevational view illustrating details of the heat exchange apparatus according to the first example embodiment of the present invention.

FIG. 5 is a perspective view of a heat exchange apparatus according to a second example embodiment of the present invention.

FIG. 6 is a perspective view of a heat exchange apparatus according to a third example embodiment of the present invention.

FIG. 7 is a perspective view of a heat exchange apparatus according to a fourth example embodiment of the present invention.

FIG. 8 is a detail view of an arrow VIII part in FIG. 7.

EXAMPLE EMBODIMENT

A minimum configuration example of a heat exchange apparatus according to the present invention will be described with reference to FIG. 1.
The heat exchange apparatus in the illustrated example includes a supply pipe 1, a heat exchange pipe 2, a discharge pipe 3, and a connecting pipe 4. The supply pipe 1 supplies a heat medium L in a liquid-phase state, which evaporates by receiving heat from a target of heat exchange. The heat exchange pipe 2 receives the supply of the heat medium L from the supply pipe 1 and absorbs heat of the target of heat exchange, for example, heat of a gas to be cooled being an indoor air of a server room. The discharge pipe 3 is provided in a vicinity of a lower part of the above-described heat exchange pipe 2 and receives the heat medium L evaporated in the heat exchange pipe 2. Then, the connecting pipe 4 directing downward connects between the upper part of the above-described heat exchange pipe 2 and the above-described discharge pipe 3.
In the heat exchange apparatus with the above-described configuration, the heat medium L supplied from the supply pipe 1 is heated to a boiling point by the gas to be cooled in the heat exchange pipe 2, is brought into a gas-phase state, and rises in the heat exchange pipe 2. At this time, upward air current of the heat medium L in the gas-phase state is in a mixed phase state of gas phase and liquid phase due to the heat medium L (droplets) in the liquid-phase state being involved or by returning the state of the heat medium L from the gas phase to the liquid phase during rising. In the heat medium L in the mixed phase state, the heat medium L in the gas-phase state is led downward by pressure and the heat medium L in the liquid-phase state is led downward by gravity through the connecting pipe 4, thereby being sent to the discharge pipe 3.
A minimum configuration example of a heat exchange method according to the present invention will be described with reference to FIG. 2.
As an assumption of FIG. 2, a flow rate (supply amount) q1 (kilogram/second) of a heat medium required for absorbing a predetermined amount of heat is calculated. When it is assumed that an amount of heat absorption per unit time in consideration of a heating value, heat transfer efficiency, and the like of a cooling target is W (joule/second) and an amount of heat (in general, an evaporated heating value per unit weight) that the heat medium per unit weight can absorb is w (joule/kilogram), the flow rate (supply amount) q1 is represented by the following equation (1).
q1=C×W/w (1)
Herein, since sensible heat given to a heat-conductive heat medium and heat conduction efficiency are ignored, the flow rate q1 actually required for absorbing the predetermined amount of heat is acquired by multiplying a predetermined coefficient C.
Further, when a surplus flow rate q2 depending on a pressure of a piping system through which the heat medium flows is added to the above-described q1, an actual flow rate Q (kilogram/second) is as follows.
Q=q1+q2 (2)
The surplus flow rate q2 described above is set larger as the pressure of the piping system through which the heat medium flows becomes smaller.
The heat medium L having the predetermined flow rate Q calculated based on the above-described equation (2) is supplied to the heat exchange pipe 2 in FIG. 1 (SP1). The heat medium L is distributed, for example, to a plurality of pipes constituting the heat exchange pipe 2 (SP2). The heat medium L is heat-exchanged with a gas to be cooled flowing on a surface of the heat exchange pipe 2 and evaporates, and also absorbs heat of the gas to be cooled (SP3). The heat medium that absorbs the heat returns to a supply source of the heat medium, for example, a compressor (not illustrated) via the discharge pipe 3, is compressed and radiates the heat therein, and is again supplied to the supply pipe 1 (SP4). Hereinafter, SP1 to SP4 are repeated.
Repeating the above-described steps enables the heat of the gas to be cooled to be absorbed in the heat medium L and discharged to an outside of a system. Herein, in step SP2, the heat medium having a flow rate Q with a margin larger than the required amount of heat absorption flows, and thus, for example, even when the heat exchange pipe 2 is branched into a plurality of pipes, the heat medium can be distributed to each branch pipe.
A first example embodiment of the present invention will be described with reference to FIGS. 3 and 4. A common configuration to each example embodiment is indicated with a same reference sign and a description thereof is simplified.
FIG. 3 illustrates a server room provided with an air conditioning facility including a heat exchange apparatus according to the first example embodiment. Herein, a reference sign 10 indicates a rack, and the racks 10 are arranged in two rows across a central passage. The racks 10 may be further arranged in a plurality of rows across the passage. Heat exchange apparatuses 11, 12, and 13 are arranged above a position associated with each rack 10 in the left row in FIG. 3, and heat exchange apparatuses 14, 15, and 16 are arranged above a position associated with each rack 10 in the right row. A detailed configuration of the heat exchange apparatuses 11 to 16 will be described later.
Above the heat exchange apparatuses 11 to 13, a main supply line 21 that supplies a heat medium to these heat exchange apparatuses and a main discharge line 31 that receives the heat medium discharged from these heat exchange apparatuses are provided.
The above-described main supply line 21 is configured in such a way as to be supplied with a liquid heat medium from a heat-medium supply source (not illustrated) such as a compressor, and the above-described main discharge line 31 is configured in such a way as to return the heat medium in a mixed phase state of gas phase and liquid phase to the above-described heat-medium supply source (not illustrated).
Above the heat exchange apparatuses 14 to 16, a main supply line 22 that supplies a heat medium to these heat exchange apparatuses and a main discharge line 32 that receives the heat medium discharged from these heat exchange apparatuses are provided.
The above-described main supply line 22 is configured in such a way as to be supplied with a liquid heat medium from a heat-medium supply source (not illustrated) such as a compressor, and the above-described main discharge line 32 is configured in such a way as to return the heat medium in a mixed phase state of gas phase and liquid phase to the above-described heat-medium supply source (not illustrated). Each of the main supply lines 21 and 22 may be either supplied with the heat medium from a common heat-medium supply source (not illustrated) or supplied with the heat medium from individual heat-medium supply sources (not illustrated).
The heat exchange apparatuses 11 to 16 will be described in detail with reference to FIGS. 4(a) and 4(b). The heat exchange apparatuses 11 to 16 have the same configuration, and thus the heat exchange apparatus 11 as a representative of the heat exchange apparatuses, and the main supply line 21 and the main discharge line 31 that are connected to the heat exchange apparatus 11 will be described.
The heat exchange apparatus 11 has a supply pipe 1 to which the heat medium L is supplied from the above-described main supply line 21 provided above. The supply pipe 1 supplies the heat medium L to one end of a distribution header pipe 5 as illustrated in FIG. 4(a).
The distribution header pipe 5 is arranged in an arrangement direction of the rack 10 (a horizontal direction in FIG. 4(a) is equivalent to a depth direction of the diagram in FIG. 3), and distributes the heat medium L to each lower part of a plurality of branch pipes 2 a that are arranged along a length direction of the distribution header pipe 5. The plurality of above-described branch pipes 2 a constitute a heat exchange pipe 2 as a whole. When warm air discharged from the rack 10, which is indicated by an arrow h in FIG. 3, comes into contact with a surface of the above-described branch pipe 2 a, the heat exchange pipe 2 absorbs heat of the warm air and supplies cold air to the server room, which is indicated by an arrow c in FIG. 3. Herein, the above-described warm air is a gas to be cooled being the air discharged by receiving heat from a heat-generating body such as electronic equipment inside the rack 10. The cold air and the warm air are circulated by natural ventilation owing to convection or artificial ventilation by a blower.
Actually, the plurality of above-described branch pipes 2 a have a configuration in which the branch pipes 2 a are arranged in parallel with a space between each other, and the surface of the branch pipes 2 a is provided with unevenness or is provided with a fin in such a way as to provide a large contact area with the gas to be cooled.
A set pipe 6 is provided at an upper part of the plurality of above-described branch pipes 2 a, and a connecting pipe 4 directing downward is connected to one end of the set pipe 6. The connecting pipe 4 is connected to the discharge pipe 3 as illustrated in the FIG. 4(b), and further, the above-described discharge pipe 3 is connected to the main discharge line 31.
In the heat exchange apparatus with the above-described configuration, the liquid-phase heat medium L supplied from the supply pipe 1 flows into the branch pipes 2 a from the distribution header pipe 5. Herein, the heat medium L flows only the surplus flow rate q2 out of a predetermined amount Q based on the above-described equation (2), and thus, even when pressure in the distribution header pipe 5 is low, the heat medium L can be evenly sent to each branch pipe 2 a. The flow rate Q of the heat medium is controlled to the predetermined amount, for example, by output adjustment of the heat-medium supply source (not illustrated) or by opening of a valve (not illustrated) provided in the main supply line 21, the supply pipe 1, and the like.
The plurality of above-described branch pipes 2 a described above are arranged side by side in a plane intersecting with air current of the room air indicated by the arrow c in FIG. 3. In these branch pipes 2 a, the heat medium L is heated to a temperature above the boiling point due to the warm air (the gas to be cooled) flowing on an outer surface of the branch pipes 2 a and becomes gas phase, and the heat medium L in a gas-phase state rises with a part of the heat medium in a liquid-phase state as a droplet. Then, the heat medium gathers in the set pipe 6 and flows into the discharge pipe 3 via the connecting pipe 4 by the flow of the gas phase illustrated by the arrow g and the flow of the liquid phase illustrated by the arrow 1, and further, returns to the heat-medium supply source (not illustrated) via the main discharge line 31. In addition, a part of the heat medium L in the liquid-phase state rising in the branch pipe 2 a falls in the branch pipe 2 a due to gravity and returns to the heat medium L accumulated in the lower part of the branch pipe 2 a. Further, the gas-phase heat medium in the discharge pipe 3 flows into the main discharge line 31 due to a pressure difference, and the liquid-phase heat medium L is pushed out, every time the liquid-phase heat medium is stored up to a predetermined level at which the discharge pipe 3 is liquid-sealed, to the main discharge line 31 due to a pressure difference caused by pressure applied from the heat exchange pipe 2.
As described above, by flowing the heat medium L in an amount larger than the amount of heat to be absorbed, the heat medium L can be evenly distributed to the plurality of branch pipes 2 a without high pressure. Further, the heat medium L in a mixed state of gas phase and liquid phase discharged from the branch pipe 2 a can be separated into gas and liquid in the connecting pipe 4 and sent to the discharge pipe 3.
Therefore, a relatively inexpensive product having low-pressure specification can be used as the supply pipe 1, the heat exchange pipe 2, the discharge pipe 3, a valve to be attached to these pipes, packing provided in a joint part, and the like, thereby reducing a cost for facility. Further, the heat medium L has low pressure, and thus it is possible to easily add a cooling facility in response to a request for increasing cooling capacity due to an addition of a server or the like.
FIG. 5 illustrates a heat exchange apparatus according to a second example embodiment.
According to the second example embodiment, valves 41 to 43 are provided at each of branches from a main supply line 21 to each heat exchange apparatus 11 to 13.
By adjusting openings of these valves 41 to 43, a flow rate of a heat medium L to be supplied to each heat exchange apparatus 11 to 13 can be controlled. In other words, a required flow rate Q based on the above-described equation (2) can be sent, by adjusting the openings of the valves 41 to 43 depending on an amount of heat absorption required for each heat exchange apparatus 11 to 13 (heating value of a rack 10 associated with each heat exchange apparatus).
Similarly, valves 44 to 46 are provided in pipes for supplying the heat medium L to each heat exchange apparatus 44 to 46 as well.
FIG. 6 illustrates a heat exchange apparatus according to a third example embodiment.
According to the third example embodiment, both a main supply line 21 and a main discharge line 31 are arranged under heat exchange apparatuses 11 to 13.
In this way, by arranging the main supply line 21 and the main discharge line 31 under the heat exchange apparatuses 11 to 13, maintenance inspection for the main supply line 21 and the heat medium discharge line 31 can be easily performed from a passage between rows of racks 10. Further, by arranging the main discharge line 31 under the heat exchange apparatuses 11 to 13, a liquid-phase heat medium L accumulated in a discharge pipe 3 can be easily discharged by gravity.
FIGS. 7 and 8 illustrate a heat exchange apparatus according to a fourth example embodiment.
According to the fourth example embodiment, it is configured that a main supply line 21 and a main discharge line 31 are provided through heat exchange apparatuses 11 to 13.
In detail, a connecting portion by flanges 23 and 24 is provided in the middle of the above-described main supply line 21, and similarly, a connecting portion by flanges 33 and 34 is provided in the middle of the above-described main discharge line 31. In other words, it is configured that both of the main supply line 21 and the main discharge line 31 are provided by connecting between the heat exchange apparatuses 12 and 13 and between the heat exchange apparatuses 11 and 12, and can be separated for each length associated with each heat exchange apparatus 11, 12, and 13.
More specifically, in the heat exchange apparatuses 11 to 16, the flanges 23 and 24 are provided at both ends of a predetermined section of the main supply line 21 illustrated in FIG. 8 and the flanges 33 and 34 are provided at both ends of a predetermined section of the main discharge line 31. The heat exchange apparatuses 11 and 12, and 12 and 13 are connected to each other by the flanges 23 and 24, or 33 and 34.
With such a configuration, the heat exchange apparatuses 11 to 16 can be independently separated from the main supply lines 21 and 22 and from the main discharge lines 31 and 32. Therefore, it is possible to easily reduce and add the heat exchange apparatuses 11 to 16 for performing maintenance inspection for each of the heat exchange apparatuses 11 to 16 or according to the reduction or addition of a server (rack 10).
According to the above-described example embodiment, the configuration is adopted in such a way that the main supply line is branched into each supply pipe and each discharge pipe is joined into the main discharge line, however, it may be configured in such a way that the main supply line 21 and the main discharge line 31 are not separately provided. Specifically, the supply pipes 1 of the heat exchange apparatuses 11 to 13 are connected in series by flanges and is used as a continuing main supply line 21, and the discharge pipes 3 of the heat exchange apparatuses 11 to 13 are connected in series by flanges and is used as a continuing main discharge line 31.
According to the above-described example embodiment, one heat exchange apparatus is provided for one rack, however it may be configured that one heat exchange apparatus cools a plurality of racks or a plurality of heat exchange apparatuses cool one rack.
A flow rate of a heat medium to be supplied to the heat exchange pipe of the heat exchange apparatus can be adjusted by controlling output of a compressor as a heat-medium supply source, inserting a throttle into piping, or the like, in addition to a valve.
While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims.
This application is based upon and claims the benefit of priority from Japanese patent application No. 2018-064288, filed on Mar. 29, 2018, the disclosure of which is incorporated herein in its entirety by reference.

INDUSTRIAL APPLICABILITY

The present invention can be used for an application such as a heat exchange apparatus, a heat exchange method, and an air conditioning system that are used for cooling a room with a rack in which a heat-generating body is accommodated.

REFERENCE SIGNS LIST

1 Supply pipe
2 Heat exchange pipe
2 a Branch pipe
3 Discharge pipe
4 Connecting pipe
5 Distribution header pipe
6 Set pipe
10 Rack
11 to 16 Heat exchange apparatus
21, 22 Main supply line
23, 24 Flange
31, 32 Main discharge line
33, 34 Flange
41 to 46 Valve
L Heat medium

Claims

What is claimed is:

1. A heat exchange apparatus comprising:

a heat exchange pipe configured to accommodate a heat medium to be evaporated by heat absorption from a gas to be cooled, the heat exchange pipe being disposed in an inclined state;

a supply pipe configured to supply the heat medium in a liquid-phase state, the supply pipe being placed in a vicinity of a lower part of the heat exchange pipe;

a discharge pipe configured to receive a heat medium to be evaporated in the heat exchange pipe and discharged from an upper part of the heat exchange pipe; and

a connecting pipe placed, directing downward, between an upper part of the heat exchange pipe and the discharge pipe.

2. The heat exchange apparatus according to claim 1, further comprising

a flow rate adjustment unit configured to adjust a flow rate of the heat medium of the supply pipe in such a way as to supply a larger amount of heat medium than a heat medium required for absorbing heat in the heat exchange pipe by a predetermined amount.

3. The heat exchange apparatus according to claim 1, wherein

the heat exchange pipe is placed in an inclined state, and is configured to be supplied with the heat medium from a lower part and discharge the heat medium from an upper part toward the connecting pipe.

4. The heat exchange apparatus according to claim 1, further comprising

a main supply line configured to supply the heat medium to the supply pipe, and a main discharge line configured to receive the heat medium discharged from the discharge pipe,

wherein the main supply line and the main discharge line are placed below the supply pipe and the discharge pipe.

5. A heat exchange method comprising:

supplying a heat medium in a liquid-phase state at a flow rate higher than a flow rate required for absorbing a heating value of a heat source by a predetermined amount, depending on the heating value;

distributing the heat medium supplied in a liquid-phase state to a plurality of heat exchange units; and

changing the heat medium distributed in a liquid-phase state into a gas-phase state by heat from the heat source, and discharging, together with the heat medium in a liquid-phase state, the heat medium in a gas-phase state having absorbed heat.

6. An air conditioning system comprising:

a plurality of heat exchange apparatuses, each of the plurality of heat exchange apparatuses comprising

a heat exchange pipe configured to accommodate a heat medium to be evaporated by heat absorption from a gas to be cooled, the heat exchange pipe being disposed in an inclined state,

a supply pipe configured to supply the heat medium in a liquid-phase state, the supply pipe being placed in a vicinity of a lower part of the heat exchange pipe,

a discharge pipe configured to receive a heat medium to be evaporated in the heat exchange pipe and discharged from an upper part of the heat exchange pipe, and

a connecting pipe placed, directing downward, between an upper part of the heat exchange pipe and the discharge pipe;

a main supply line configured to supply the heat medium to the supply pipe of the heat exchange apparatus; and

a main discharge line configured to receive the heat medium from the discharge pipe of the heat exchange apparatus,

wherein the heat exchange pipe is disposed in a direction in which the heat exchange pipe intersects air current.

7. The air conditioning system according to claim 6, further comprising

a flange placed in a middle of the main supply line in such a way as to connect the main supply line in a separable manner with respect to each predetermined length, and

a flange placed in a middle of the main discharge line in such a way as to connect the main discharge line in a separable manner with respect to each predetermined length.

8. The heat exchange apparatus according to claim 2, wherein

9. The heat exchange apparatus according to claim 2, further comprising

10. The heat exchange apparatus according to claim 3, further comprising

11. The air conditioning system according to claim 6, wherein

each of the plurality of heat exchange apparatuses further includes a flow rate adjustment unit configured to adjust a flow rate of the heat medium of the supply pipe in such a way as to supply a larger amount of heat medium than a heat medium required for absorbing heat in the heat exchange pipe by a predetermined amount.

12. The air conditioning system according to claim 6, wherein

13. The air conditioning system according to claim 6, wherein

each of the plurality of heat exchange apparatuses further includes a main supply line configured to supply the heat medium to the supply pipe, and a main discharge line configured to receive the heat medium discharged from the discharge pipe, and

the main supply line and the main discharge line are placed below the supply pipe and the discharge pipe.

14. The air conditioning system according to claim 7, wherein

15. The air conditioning system according to claim 7, wherein

16. The air conditioning system according to claim 7, wherein