JPH09264621A - Natural circulation type cooling apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the pressure loss and enable smoothly circulating refrigerant in a natural circulation loop by making a vaporizer provided with distribution pipes for distributing liquid refrigerant from a liquid delivery pipe to heating tubes and with collecting pipes for collecting refrigerant gas from the heating tubes to send it through a gas delivery pipe. SOLUTION: In a natural circulation loop which cools the ambient air with a liquid refrigerant a vaporizer has a heat-absorbing part 96 having an arrangement of a plurality of heating tubes 100 through which liquid refrigerant is passed and made to absorb heat from the outside air. The liquid refrigerant is injected into these heating tubes 100 through a header 102 and the refrigerant gas from the heating tubes 100 is sent through a header 104. The header 102 is composed of a main pipe 106 and branch pipes 108 with a liquid delivery pipe 58 connected to the lower end of the main pipe 106. The header 104 is composed of a main pipe 110 and branch pipes 112 with a gas delivery pipe connected to the upper end of the main pipe 110. This constitution lessens the pressure loss and enables effectively utilizing the small driving force of the refrigerant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a natural circulation type cooling device, and more particularly to an evaporator which secures a circulation driving force of a refrigerant and improves a cooling capacity.

[0002]

2. Description of the Related Art In recent years, air conditioners have been used not only for interpersonal air conditioning for humans, but also for electronic devices such as computer rooms and capsules containing relay electronic devices for mobile communication. The field of application for removing the generated heat is rapidly expanding.

In these applications, in addition to the heat load generated indoors, the heat load (skin,
There is a road). Therefore, the cooling capacity for this room is designed based on summer, etc., and the space to be cooled is surrounded by a heat insulating wall to reduce the skin load and the inside is cooled by a vapor compression refrigeration cycle with high cooling capacity. . On the other hand, since the room is surrounded by a heat insulating wall, the heat generated from the indoor equipment is unlikely to be dissipated to the outside even if the outside environment is cold, such as in winter and at night, and the room temperature rises. For this reason, it is necessary to cool the room even in cold weather.

However, it is uneconomical to purposely use a vapor compression refrigeration cycle in which the operating cost of the compressor is high even when natural heat dissipation is possible, and the useful life of the compressor, that is, its life is short. There was a problem of becoming. In such a case, it is preferable to use a heat pipe that uses the temperature difference between the inside and the outside to transfer heat from the inside to the outside with a refrigerant. The natural circulation type cooling cycle is an application of the principle of this heat pipe, and a refrigerant loop is formed by passing a refrigerant gas and a refrigerant liquid through separate pipes to achieve higher heat transfer efficiency.

As a conventional example in which this natural circulation type cooling cycle is used, there is a cooling device in which a natural circulation type cooling cycle is used in combination with a vapor compression refrigeration cycle (Japanese Patent Application No. 7-2).
22920). FIG. 3 is a configuration diagram of a refrigeration cycle in the cooling device. The vapor compression refrigeration cycle in this cooling device roughly includes a compressor 2, a condenser 4, and an evaporator 6. The compressor 2 is provided in the middle of the gas pipe 8 that guides the refrigerant gas generated in the evaporator 6, sucks the refrigerant gas, adiabatically compresses it, and sends it out. As a result, the refrigerant gas is brought into an overheated state, and the driving force for circulating the refrigerant is supplied to the refrigerant cycle. The condenser 4 radiates heat from the overheated refrigerant gas and liquefies it. Refrigerant liquid is liquid pipe 10
And is sent to the evaporator 6 side. The expansion valve 12 provided in front of the evaporator 6 has a function of reducing the pressure of the high-pressure refrigerant liquid to low-pressure wet vapor in a gas-liquid mixed state. The wet steam absorbs the heat of vaporization from the object to be cooled in the evaporator 6, becomes a refrigerant gas, and is sent out to the gas pipe 8 again. The suction accumulator 14 is a device that serves as a buffer in the event of a transient phenomenon of operation or an excessive amount of refrigerant filled.

The natural circulation type cooling cycle in this cooling device is realized by arranging the condenser 4 at a predetermined higher position than the evaporator 6 and by bypassing the compressor 2 with a bypass pipe 30. The bypass pipe 30 is provided with a refrigerant flow path switching valve 32, and when it is closed, this device is the vapor compression refrigeration cycle described above, but the compressor 2 is stopped and the refrigerant flow path switching valve 32 is provided. When opened, it becomes a natural circulation type cooling cycle. That is, this device
The natural circulation type cooling cycle and the vapor compression refrigeration cycle are not configured as separate refrigerant circulation systems, but only some of the refrigerant flow paths are switched to configure the refrigerant circulation system such as the condenser 4 and the evaporator 6. Many of the constituent elements are shared by both cycles.

In the natural circulation type cooling cycle, the bypass pipe 3
0 becomes the flow path of the refrigerant gas, and the refrigerant gas having a low specific gravity rises in the gas pipe 8 even when the compressor 2 is stopped, reaches the condenser 4, and becomes the refrigerant liquid in the condenser 4. This refrigerant liquid flows down in the liquid pipe 10 by gravity and reaches the evaporator 6 again. As described above, the driving force of the refrigerant in the natural circulation type cooling cycle is generated by the height difference between the condenser 4 and the evaporator 6. This driving force is much smaller than the driving force of the compressor 2 in the vapor compression refrigeration cycle.

On the other hand, FIG. 4 is a schematic diagram showing the structure of the evaporator 18 in the conventional cooling apparatus for the vapor compression refrigeration cycle alone. The main part of the evaporator 18 is a plurality of heat transfer tubes 20 that pass the refrigerant liquid. By thus uniformly distributing the refrigerant liquid to the plurality of tubes, the heat transfer area between the refrigerant and the cooled air is increased, and the heat absorption efficiency of the refrigerant is improved. A distributor (distributor) 22 is provided on the inlet side of these heat transfer tubes 20, that is, on the side connected to the liquid pipe. The distributor 22 has an orifice 24. One side of the orifice 24 is connected to the liquid pipe 25, and the other side and each heat transfer tube 20 are connected via a thin tube 26 having an inner diameter smaller than that of the heat transfer tube.

The thin tube 26 adds a uniform pressure loss to each heat transfer tube 20 to relatively reduce the variation in pressure loss among the heat transfer tubes 20. That is, for example, the heat transfer tube 20 constituting the main part of the evaporator 18 has a relatively large thickness and length, and the heat transfer tube 20 must be very carefully controlled to suppress the pressure loss difference between them. Processing of tubes etc. must be performed. Further, since the wall thickness of the heat transfer tube 20 is not so thick in order to improve heat transfer efficiency, even if the heat transfer tube 20 is once made uniform, it may be transported, or by some impact after the start of operation. There is a risk that somewhere in the heat transfer tube 20 will be distorted. Then, the pressure loss becomes uneven between the heat transfer tubes 20. If the pressure loss between the heat transfer tubes 20 is not uniform, the distribution of the refrigerant liquid will be non-uniform between the heat transfer tubes 20, and the heat transfer efficiency will decrease and the cooling capacity will also decrease.

On the other hand, if the thin tube 26 has a fine inner diameter, it does not need to be so long in order to obtain the necessary pressure loss. It is relatively easy to process a short pipe with high precision. Moreover, since it is not necessary to consider the heat transfer efficiency of this portion, it can be made to be durable. Therefore, it is easy to realize uniform pressure loss between the thin tubes 26 of the distributor 22. Here, the effect of the thin tube 26 will be specifically described by an example using numerical values. It is assumed that the pressure losses of the two heat transfer tubes A and B are 95 and 100 (unit is arbitrary), respectively. That is, tube A has a 5% less pressure loss than B. When a uniform pressure loss 100 due to the thin tube 26 is added to these tubes, the pressure loss in each path of the tubes A and B becomes 195 and 200 in total, respectively, and the relative pressure loss difference between them is reduced to 2.5%. . That is, the conventional distributor 22 is intended to cause a pressure difference of the refrigerant liquid and to make the pressure loss of each path uniform by the thin tube 26.

As described above, the inlet side of the evaporator of the conventional vapor compression refrigeration cycle is constructed, but on the other hand, no special consideration has been given to the outlet side in the past, and the header 28 is simply used. The refrigerant gas from the outlet of the heat transfer tube 20 is merged and sent to the gas pipe 29.

[0012]

As described above, the circulation driving force of the refrigerant of the natural circulation type cooling device is much smaller than the driving force of the compressor in the vapor compression refrigeration cycle. Therefore, it is desirable to reduce the pressure loss in the refrigerant circulation path as much as possible. However, in the evaporator used in the above-mentioned conventional vapor compression refrigeration cycle, there is a problem that the pressure loss is large, the refrigerant circulation amount is reduced, and the cooling capacity is reduced.

It is an object of the present invention to provide a natural circulation type cooling device having a high cooling capacity, which is provided with an evaporator which has a small pressure loss and can effectively utilize a small refrigerant driving force.

[0014]

In the natural circulation air conditioner of the present invention, the evaporator is connected to one end of each heat transfer tube along the first main pipe whose lower end is connected to the liquid pipe. A distribution pipe for distributing a flow rate from the first main pipe to inject a refrigerant liquid into each of the heat transfer tubes,
A branch pipe connected to the other end is provided for each heat transfer tube along the second main pipe whose upper end is connected to the gas pipe, and the refrigerant gas generated in each heat transfer tube from the branch pipe is transferred to the second main pipe. And a collecting pipe that joins into the main pipe.

According to the present invention, the distribution pipe provided in the evaporator is intended only to distribute the refrigerant liquid from the liquid pipe to the heat transfer tube, and the collecting pipe simply receives the refrigerant gas from the heat transfer tube. The purpose is to collect and deliver to the gas pipe, and neither is intended to generate pressure loss. Therefore, the refrigerant liquid is injected into this evaporator,
The pressure loss until it becomes a refrigerant gas and flows out is small, and the refrigerant smoothly circulates in the natural circulation loop, so heat is efficiently transferred from the evaporator side to the condenser side, and the cooling capacity is improved. Is planned. For example, the branch pipe has an inner diameter similar to that of the heat transfer tube, and has no bend in the middle to connect the main pipe and the heat transfer tube. Since the second main pipe constituting the collecting pipe is connected to the gas pipe at its upper end, the refrigerant gas is smoothly guided to the gas pipe without impairing its ascending force, that is, the refrigerant driving force. Further, in this structure of the collecting pipe, even if the refrigerant liquid (wet vapor) reaches the collecting pipe without being completely vaporized, the refrigerant liquid has a specific gravity difference with the refrigerant gas, and the lower end side in the second main pipe. Distributed in the gas pipe and is not led to the gas pipe. That is,
When the refrigerant liquid having a large specific gravity is carried upward along with the refrigerant gas through the gas pipe, the refrigerant driving force is lost, which is suppressed in the present invention. On the other hand, since the first main pipe constituting the distribution pipe is connected to the liquid pipe at the lower end thereof, first, in correspondence with the above-mentioned configuration of connecting the gas pipe at the upper end of the collecting pipe, Of the refrigerant flow rate of
The heat transfer area of the evaporator is effectively used. Further, in this configuration, as described in the collecting pipe, fine droplets having a small specific gravity in the wet vapor of the refrigerant are distributed on the upper end side of the first main pipe, and conversely, large droplets are distributed on the lower end side. Cheap. Therefore, the degree of vaporization of the refrigerant liquid becomes higher in the upper heat transfer tube whose outlet is closer to the gas pipe, and pressure loss due to the above-mentioned refrigerant droplets being sent to the gas pipe is less likely to occur.

[0016]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a refrigeration cycle in a cooling device according to an embodiment of the present invention. This cooling device uses the natural circulation cooling device of the present invention together with a vapor compression refrigeration cycle. The basic structure is the same as that of the cooling device shown in the related art, but the structure of the indoor unit 50, in particular, the evaporator 52 is different from the conventional structure. First, the configuration of the cooling device shown in FIG. 1 will be described in detail.

The apparatus is roughly composed of an indoor unit 50, an outdoor unit 54, and a gas pipe 56 and a liquid pipe 58 connecting these units. The indoor unit 50 includes an evaporator 52, an expansion valve 60, a bypass pipe 62 that bypasses the expansion valve 60, and switching valves 64 and 66 that switch the refrigerant flow path to either the expansion valve 60 or the bypass pipe 62. The unit 54 includes a compressor 80, a condenser 82, a suction accumulator 84, a bypass pipe 86 that bypasses the compressor 80, and switching valves 88 and 90 that switch a refrigerant flow path between the compressor 80 and the bypass pipe 86. To be done. The condenser 82 is an air-cooled condenser and includes a fan 94 that blows air to the refrigerant container 92. As will be explained later, the evaporator 52, i.e. the indoor unit 50, must be lower than the condenser 82, i.e. the outdoor unit 54.

First, the vapor compression refrigeration cycle will be described.
The compressor 80 is driven by an external power source, and has a function of adiabatically compressing the refrigerant gas into an overheated refrigerant gas. The compressor is roughly classified into types such as a reciprocating type, a rotary type, and a screw type. A suitable compressor is selected and used according to conditions such as the required refrigerating capacity for the compressor 80 used here. . The condenser 82 radiates heat from the refrigerant gas generated in the evaporator to the atmosphere and liquefies the refrigerant gas into a refrigerant liquid. In the condenser 82, the fan 94 is connected to the refrigerant container 9
Air is blown to the outer surface of 2 to promote heat dissipation from the refrigerant gas generated in the evaporator to the atmosphere, which is an external medium having a lower temperature than this. The refrigerant liquid generated in the condenser 82 goes down to the indoor unit 50 through the liquid pipe 58.

The expansion valve 60 is provided immediately before the inlet of the evaporator 52. The expansion valve 60 depressurizes the high-pressure refrigerant liquid by expansion to reduce it to a low-temperature low-pressure wet vapor in a gas-liquid mixed state. The expansion valve 60 may be, for example, a temperature automatic expansion valve, or a capillary tube is used instead. You can also The wet steam guided to the evaporator 52 absorbs heat of vaporization from the object to be cooled and becomes a refrigerant gas, while the object to be cooled is cooled. The gas pipe 5 is provided between the evaporator 52 and the intake side of the compressor 80.
6. Suction accumulator 8
Reference numeral 4 denotes a device which is provided at the inlet of the compressor 80 and temporarily stores the refrigerant gas discharged from the evaporator 52, and serves as a buffer in the case of a transient phenomenon of operation or an excessive amount of filled refrigerant.

Next, the natural circulation loop in which the present invention is implemented will be described. Most of them are common with the vapor compression refrigeration cycle described above. The natural circulation loop includes, in part, a bypass pipe 86 that connects the suction accumulator 84 and the compressor 80.
Is different from the vapor compression refrigeration cycle in that the expansion valve 60 is bypassed by the bypass pipe 62. Switching of these flow paths is performed by switching valves 88, 90, 6
4, 66. That is, when this refrigeration cycle is used as a vapor compression refrigeration cycle (referred to as a forced circulation mode), the switching valves 88 and 64 are opened and the switching valves 90 and 66 are closed. Conversely, when the refrigeration cycle is used as a natural circulation loop (called the natural circulation mode)
First, the switching valves 90 and 66 are opened, and the switching valves 88 and 64 are closed.

In the natural circulation loop, there is no driving force for the refrigerant circulation by the compressor 80. In this case, the refrigerant liquid generated in the condenser 82 descends in the liquid pipe 58 due to gravity and is accumulated therein. That is, the gravity acting on the refrigerant liquid accumulated in the liquid pipe 58 serves as the driving force for the refrigerant circulation. The refrigerant liquid is supplied by gravity to the evaporator 52, where it becomes a refrigerant gas. This refrigerant gas is guided to the gas pipe 56 side having a low pressure. The evaporator 52 side of the gas pipe 56 is a generation source of the refrigerant gas, while the condenser 82 side is an absorption source of the refrigerant gas, so that a pressure gradient is generated in the gas pipe 56. That is, the gas pressure on the condenser 82 side is equal to that of the evaporator 52.
Since it is lower than the side, the refrigerant gas having a smaller specific gravity than the refrigerant liquid rises in the gas pipe 56 and reaches the condenser 82.

The above is the mechanism of the natural circulation loop. Therefore, the refrigerant driving force of the natural circulation loop is the condenser 82.
Is higher than the evaporator 52. As for the size, the larger the height difference between the condenser 82 and the evaporator 52 is,
large. Further, the higher the height of the column made of the refrigerant liquid accumulated in the liquid pipe 58, the larger. Therefore, in principle, the required cooling capacity can be obtained by increasing these values, but in most cases there is a practical upper limit to these values. Therefore, in order to improve the cooling capacity with a given refrigerant driving force, it is necessary to reduce pressure loss when the refrigerant circulates in the natural circulation loop and to circulate the refrigerant as smoothly as possible. Therefore, conventionally, the inner diameter of the gas pipe 56 is made slightly thicker and the inner diameter of the liquid pipe 58 is made slightly thinner. One such ingenuity in this device is that in natural circulation mode,
Bypassing the expansion valve 60 that causes a pressure difference in the refrigerant pressure. The other is the improvement of the structure of the evaporator 52 described below.

FIG. 2 is a schematic diagram showing the structure of the evaporator 52 of this apparatus. This figure is a side view of the evaporator 52, and the vertical direction of the figure corresponds directly to the vertical direction. The heat absorbing portion 96 of the evaporator 52 has a plurality of heat transfer tubes 1
00 is provided, and these take the heat from the outside air through the refrigerant liquid. The header 102 injects the refrigerant liquid from the liquid pipe 58 to each heat transfer tube 100, and the header 1 sends the refrigerant gas from each heat transfer tube 100 to the gas pipe 56.
04. The header 102 includes a main pipe 106 and a branch pipe 108 connecting the main pipe 106 and each heat transfer tube 100.
, And the liquid pipe 58 is connected to the lower end of the main pipe (a low point in the gravity field). The header 104 is the main pipe 11
0, and a branch pipe 112 connecting this to each heat transfer tube 100, and the gas pipe 56 is connected to the upper end of the main pipe (high part in the gravity field). Branch pipe 108,
112 has an inner diameter similar to that of the heat transfer tube 100.
Therefore, structurally, the branch pipes 108 and 112 and the heat transfer tube 10 are
There may be no boundary between 0 and 0. Main pipe 106,
Since the branch pipes 108 and 112 are joined to the side surface of the 110, it generally has a larger inner diameter and outer diameter than the branch pipe. In particular, the main pipes 106 and 110 are configured such that the refrigerant liquid flows from the liquid pipe 58 to the heat transfer tubes 100, and the heat transfer tubes 10 respectively.
The conductance is made large so as not to hinder the flow of the refrigerant gas from 0 to the gas pipe 56. For example, the main pipe does not have a structure such as a complicated bend inside, but is a pipe having a straight or smooth internal shape.

Next, the behavior of the refrigerant in the evaporator 52 will be described. The refrigerant liquid (wet vapor) from the liquid pipe 58 flows into the main pipe 106 of the header 102, and is sent from the main pipe 106 to each heat transfer tube 100 via each branch pipe 108. That is, the header 102 functions as a distribution pipe that distributes the refrigerant liquid to each heat transfer tube. Each heat transfer tube 1
The refrigerant liquid sent to 00 absorbs heat from the outside world and is vaporized. The refrigerant gas generated in each heat transfer tube 100 is collected in the main pipe 110 via the branch pipe 112 of the header 104 and is sent from the main pipe 110 to the gas pipe 56. That is, the header 104 functions as a collecting pipe that collects the refrigerant gas from each heat transfer tube.

By connecting the gas pipe 56 to the upper end of the main pipe 110 and connecting the liquid pipe 58 to the lower end of the main pipe 106, the refrigerant flow rate between the heat transfer tubes 100 is made uniform. This is because the difference between the heat transfer tubes 100 in the distance between the inlet of each heat transfer tube 100 and the liquid pipe 58 is
This is because the difference between the heat transfer tubes 100 in the distance between the outlet of each heat transfer tube 100 and the gas pipe 56 is compensated for. That is, in the main evaporator 52, the main pipe 106,
Branch pipe 108, heat transfer tube 100, branch pipe 112, main pipe 1
The conductance of the refrigerant path that follows in the order of 10,
It is less affected by the position of the heat transfer tube 100 and has a substantially constant value. Also here, the liquid pipe 58 is connected to the main pipe 10.
If connected to the upper end of 6, heat transfer tube 100 below
The distance from the liquid pipe 58 and the gas pipe 56 increases.
Therefore, the flow rate of the refrigerant liquid will be greater in the upper heat transfer tube 100 near both pipes. Heat transfer tube 100
If the flow rate of the refrigerant between them is not uniform, the heat transfer area of the heat transfer section 96 is not effectively used, and the improvement of the cooling capacity cannot be expected. The evaporator 52 of this device solves this problem, and the heat transfer tube 1
A uniform cooling medium flow rate is used to realize the improvement of the cooling capacity.

If the liquid pipe 58 is connected to the upper portion of the main pipe 106, large refrigerant droplets will easily flow into the upper heat transfer tube 100. Large refrigerant droplets may not be completely vaporized in the heat transfer tube 100, but since the outlet of the upper heat transfer tube is close to the gas pipe, the remainder of this refrigerant droplet is sent to the gas pipe 56 (with liquid entrainment). ). Then, the specific gravity of the refrigerant gas in the gas pipe 56 increases and the downward force due to gravity increases, resulting in a loss of the refrigerant circulation driving force. On the other hand, in the evaporator 52, since the liquid pipe 58 is connected to the lower end of the main pipe 106, heavy and large refrigerant droplets stay on the lower end side, and light and fine refrigerant droplets are distributed to the upper end side. Cheap. Therefore, the refrigerant droplets flowing into the upper heat transfer tube 100 are fine and easily vaporized, so that the refrigerant droplets are unlikely to be delivered to the vicinity of the inlet of the gas pipe 56 in the header 104. Also,
Even if the refrigerant droplets that remain without being vaporized from the lower heat transfer tube 100 are sent to the header 104, these droplets are
Stay at the bottom of 0. Therefore, in the main evaporator 52, the refrigerant droplets are less likely to flow into the gas pipe 56, and the loss of the refrigerant circulation driving force as described above is prevented.

Further, the fact that the gas pipe 56 is connected to the upper portion of the main pipe 110 has an effect that liquid entrainment does not easily occur as described above, and an effect that the upward flow of the refrigerant gas is not hindered. Loss is suppressed.

As described above, according to the present invention, the pressure loss until the refrigerant liquid is injected into the evaporator 52 and becomes the refrigerant gas and flows out is small, and the refrigerant driving force loss in the gas pipe 56 is also small. Therefore, since the refrigerant smoothly circulates in the natural circulation loop, heat is efficiently transferred from the evaporator 52 side to the condenser 54 side, and the cooling capacity is improved.

This device, which is a cooling system combined with natural circulation, is used for indoor cooling of electronic equipment, and in addition to the heat load from the electronic equipment during the summer, external skin
When there is a load and cooling capacity is required, it is operated in forced circulation mode, while when the heat load from the electronic equipment is mainly and the cooling capacity is not so much required in winter, natural circulation is performed. Driven in mode. In the natural circulation mode, the compressor 80 does not need to be operated, which consumes less electric power and saves operating power costs. Also,
When the outside air temperature is low, the compressor 8 is set as the natural circulation mode.
Since 0 can be paused, the useful life of the compressor 80 is extended and the mean time between failures (MTBF) of the cooling system is increased.
Becomes longer. By increasing the reliability of the cooling system in this way, the possibility of damage to expensive electronic equipment in the room is reduced. Thus, the combined use of the natural circulation loop has great advantages.

In the present apparatus, the vapor compression refrigeration cycle is also used with the natural circulation loop, but it is not always necessary to use the combination type. In other words, it is sufficient to use the combined use type only in a place where the cooling capacity of the natural circulation loop may be insufficient, and in a cold region or the like, only the natural circulation loop may be used.

[0032]

According to the present invention, the pressure loss of the refrigerant in the evaporator is small. Also, liquid entrainment in the gas pipe is unlikely to occur. Therefore, there is an effect that the loss of the refrigerant driving force is suppressed and a natural circulation type cooling device having a high cooling capacity is obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a refrigeration cycle in a cooling device that is an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing the structure of an evaporator of the present apparatus.

FIG. 3 is a configuration diagram of a refrigeration cycle in a conventional cooling device.

FIG. 4 is a schematic configuration diagram showing the structure of a conventional evaporator.

[Explanation of symbols]

22 distributor, 24 orifice, 26
Thin tube, 50 indoor unit, 6,18,52 evaporator,
54 outdoor unit, 8, 29, 56 gas pipe, 1
0,25,58 liquid piping, 12,60 expansion valve, 30,
62,86 Bypass pipe, 2,80 Compressor, 4,82
Condenser, 20,100 Heat transfer tube, 102,10
4 Header, 106,110 Main pipe, 108,112
Branch pipe.

Claims (1)

[Claims] 1. An evaporator that absorbs heat of vaporization when a refrigerant liquid becomes a refrigerant gas from a cooled portion, a gas pipe that raises the refrigerant gas from the cooler, and the refrigerant guided by the gas pipe. It has a natural circulation loop provided with a condenser for liquefying a gas into the refrigerant liquid, and a liquid pipe for lowering the liquefied refrigerant liquid to guide it to the evaporator, the evaporator being the refrigerant liquid. In a natural circulation type cooling device including a plurality of heat transfer tubes in which is injected and vaporized, the evaporator has a lower end for each heat transfer tube along a first main pipe connected to the liquid pipe. A distribution pipe that is provided at one end and that distributes a flow rate from the first main pipe to inject the refrigerant liquid into each of the heat transfer tubes, and a second main pipe whose upper end is connected to the gas pipe Along with each heat transfer tube Is provided with a branch pipe connected to the other end, and a collecting pipe for joining the refrigerant gas generated in each of the heat transfer tubes from the branch pipe into the second main pipe is provided. Air conditioner.