JPH09273876A - Cooler with natural circulation loop - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a drop in the cooling capacity by restricting retention of a refrigerant increased up to a liquid phase under a low outside air temperature in a natural circulation loop. SOLUTION: A refrigerant liquid reservoir 30 is provided and an excessive refrigerant liquid is distributed by a condenser 22 and the refrigerant liquid reservoir 30. As the refrigerant liquid reservoir 30 is made up of a container with a larger bottom area, the most of the excessive refrigerant liquid is stored into the refrigerant liquid reservoir 30, so that the level of the refrigerant liquid in the condenser 22 can be restricted sufficiently as compared with the case where the refrigerant liquid reservoir 30 is not used. Thus, a decrease in effective heat transfer area of the condenser 22 is prevented to secure a cooling capacity. In addition, the refrigerant liquid reservoir 30 is connected to the topmost point of a liquid piping 28 secure the height of the liquid column of the refrigerant, thereby assuring a refrigerant circulation drive force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device having a natural circulation loop, and more particularly to a condenser for ensuring heat exchange efficiency and improving 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. A cooling cycle using a natural circulation loop 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. Is.

FIG. 5 is a schematic configuration diagram for explaining the principle of a cooling device using a natural circulation loop. In the natural circulation loop, the condenser 2 is arranged at a predetermined higher position than the evaporator 4. The condenser 2 is placed outside in a cold room, radiates heat from the refrigerant gas sent from the gas pipe 6 to the outside air, and changes the phase of the refrigerant gas into a refrigerant liquid. This refrigerant liquid descends in the liquid pipe 8 due to gravity and is accumulated therein. The gravity acting on the refrigerant liquid accumulated in the liquid pipe 8 serves as the driving force for circulating the refrigerant. The refrigerant liquid is gravity-supplied to the indoor evaporator 4 having a heat load, and becomes the refrigerant gas there. This refrigerant gas is guided to the gas pipe 6 side having a low pressure. Gas pipe 6
Since the evaporator 4 side is a refrigerant gas generation source and the condenser 2 side is a refrigerant gas absorption source, a pressure gradient is generated in the gas pipe 6. That is, since the gas pressure on the condenser 2 side is lower than that on the evaporator 4 side, the refrigerant gas having a smaller specific gravity than the refrigerant liquid rises in the gas pipe 6 and reaches the condenser 2.

As described above, the refrigerant circulation driving force of the natural circulation loop is generated by the height difference between the condenser 2 and the evaporator 4, and more accurately, the height of the refrigerant liquid column accumulated in the liquid pipe 8. Proportional to. The amount of the refrigerant liquid existing in the loop (or the ratio of the refrigerant liquid and the refrigerant gas) changes depending on the temperature difference between the room and the room and the temperature outside the room. In the case of the vapor compression refrigeration cycle, this change can be suppressed by adjusting the operations of the compressor and the expansion valve. However, in the natural circulation loop, since there is no such adjusting mechanism, the amount of the refrigerant liquid changes greatly.

Since the natural circulation loop does not require a compressor for circulating the refrigerant and has the advantages of the above-described economy, the vapor compression is used for the applications requiring indoor cooling throughout the four seasons as described above. A cooling device using a natural circulation loop in a refrigeration cycle has been proposed (Japanese Patent Application No. 7-222).
920). This device forms a vapor compression refrigeration cycle when the heat load is high in summer, etc. by switching some of the flow paths that make up the refrigerant circulation system, and natural circulation when the heat load is low in winter etc. A loop is constructed to perform cooling.

[0008]

As described above, the amount of the refrigerant liquid in the natural circulation loop fluctuates greatly under the influence of the outside temperature. Therefore, when the outside air temperature is low, the amount of the refrigerant liquid increases, and the refrigerant liquid that cannot be accommodated in the liquid pipe may stay in the condenser. Then, the effective heat transfer area where the refrigerant gas and the outside air are performed in the condenser is decreased, the amount of supercooling of the refrigerant liquid is decreased, and the cooling capacity of the cooling device using this natural circulation loop is reduced. was there.

Further, in the above cooling apparatus using both the vapor compression refrigeration cycle and the natural circulation loop, the amount or distribution of the refrigerant liquid is changed by switching the refrigerant circulation systems, and the cooling capacity is the same as the above. Degradation problems may occur.

The present invention suppresses the retention of the refrigerant liquid in the condenser when the outside temperature is low such as in winter or when the refrigerant circulation system is switched to the natural circulation loop, thereby preventing the cooling capacity from decreasing. An object of the present invention is to provide a cooling device having a natural circulation loop.

[0011]

A cooling device provided with a natural circulation loop of the present invention is a refrigerant liquid which is connected to a flow path of a refrigerant liquid and accumulates the refrigerant liquid to remove retention of the refrigerant liquid inside the condenser. It is characterized by having a reservoir. According to the present invention, the refrigerant liquid reservoir is arranged, for example, at a height position between the condenser and the evaporator in the middle of the liquid pipe, or is connected to a position in the middle of the liquid pipe by a separately provided pipe, This refrigerant liquid reservoir, which is connected to or attached to the lower part of the condenser, collects excess refrigerant liquid even if the amount of refrigerant liquid liquefied in the condenser and accumulated in the liquid pipe exceeds the capacity of the liquid pipe. Is removed from the condenser. For this reason, the refrigerant liquid is suppressed from accumulating in the condenser, so that the heat transfer area between the refrigerant gas and the outside air in the condenser is ensured and the cooling capacity is prevented from being lowered. The refrigerant liquid reservoir collects the refrigerant liquid only when the amount of the refrigerant liquid is large, and the accumulated refrigerant liquid is reduced before the amount of the refrigerant liquid in the liquid pipe when the excess of the refrigerant liquid is eliminated. To do.

In the cooling apparatus having the natural circulation loop of the present invention, the refrigerant liquid reservoir is provided at the height of the connection position of the liquid pipe to the condenser. According to the present invention, the height of the refrigerant liquid column accumulated in the liquid pipe is increased while the retention of the refrigerant liquid in the condenser is suppressed, and the driving force for refrigerant circulation in the natural circulation loop is secured. Therefore, by ensuring the heat transfer area and the driving force in the condenser, a higher cooling capacity is realized.

[0013]

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

[Embodiment 1] FIG. 1 is a schematic configuration diagram of a refrigeration cycle in a cooling device of the present invention using a natural circulation loop. This device does not have a compressor and uses only a natural circulation loop.

Since the principle of the natural circulation loop in this device is the same as that shown in FIG. 5 of the prior art, the components having the same functions are designated by the symbols of FIG. 5 plus 20. Description may be omitted. In order to obtain the necessary driving force for circulating the refrigerant, the condenser 22 is arranged at a higher position than the evaporator 24 by a liquid pipe 28 having a height difference of, for example, about 2 m. In this device, the refrigerant liquid reservoir 30 has a horizontal branch pipe 3
2 is connected to the liquid pipe 28. The height of the connecting position is the connecting position of the liquid pipe 28 to the condenser 22.

The refrigerant liquid generated in the condenser 22 descends in the liquid pipe 28 due to gravity and is first accumulated therein. But,
When the outside air temperature is particularly low, the amount of the refrigerant liquid in the loop (that is, the refrigerant in the liquid phase state instead of the gas phase state) increases, and the upper portion of the liquid pipe 28 is filled with the refrigerant liquid. May occur.

Conventionally, this excess refrigerant liquid has accumulated in the lower portion of the heat transfer tube in the condenser 22. On the other hand, in this device, excess refrigerant liquid is distributed between the condenser 22 and the refrigerant liquid reservoir 30. At this time, the inside of the condenser 22 and the refrigerant reservoir 3
The height of the liquid surface of the refrigerant in the inside of 0 is basically the same. Here, while the refrigerant liquid reservoir 30 is composed of a container having a large bottom area, the condenser 22 has pipes for guiding the refrigerant gas from top to bottom while the heat transfer tubes are bent in multiple layers therein. Has been done. By passing the refrigerant through the elongated tube in this way, a large heat transfer area with the outside air can be obtained, and a sufficiently cooled refrigerant liquid can be obtained. That is, the amount of supercooling of the refrigerant liquid can be earned. Due to this difference in structure, the refrigerant liquid reservoir 30 has a sufficiently large amount of liquid that can be accumulated at the same height as the condenser 22 and the refrigerant liquid reservoir 30. Therefore, most of the excess refrigerant liquid is accumulated in the refrigerant liquid reservoir 30, and the height of the refrigerant liquid surface in the condenser 22 in this device is sufficiently suppressed as compared with the case where the refrigerant liquid reservoir 30 is not used.

By suppressing the liquid level in the condenser 22, the length of the effective heat transfer tube or the effective heat transfer area for heat exchange between the refrigerant gas and the outside air is increased.
That is, the efficiency of heat exchange is improved and the supercooling amount of the refrigerant liquid is increased, so that the cooling capacity is improved.

The branch pipe 32 is connected to the lower portion of the container so that the coolant liquid accumulated in the coolant liquid reservoir 30 quickly flows out to the liquid pipe 28 when the coolant liquid level drops below the branch pipe 32. The container of the refrigerant liquid reservoir 30 of the present device is sufficiently large so that the upper part may have a closed structure. However, in the case of a small container, if the upper part of the container has a closed structure, the liquid surface 34 is formed on the upper part of the container as it rises. As a result, the pressure of the vapor phase portion 36 becomes high, and it becomes difficult for the refrigerant liquid to flow into the container. Therefore, in a small container, a thin tube for adjusting the atmospheric pressure of the gas phase portion 36 is connected from the upper portion of the container to, for example, a heat transfer tube of the gas phase portion of the condenser 22, or the upper portion of the container is exposed to the outside air to facilitate heat dissipation, thereby cooling The structure may be such that the atmospheric pressure of the vapor phase portion 36 is lowered.

The refrigerant sump 30 of the present apparatus is connected to the highest point of the liquid pipe 28 in order to secure the height of the refrigerant liquid column required to obtain the maximum refrigerant circulation driving force, for example, 2 m. . Incidentally, the coolant reservoir may be provided at another position. 2 and 3 are diagrams (FIG. 2 is a partial view) showing a schematic configuration of a refrigerating cycle showing another installation mode of a refrigerant liquid reservoir. In the form shown in FIG. 2A, the refrigerant liquid reservoir 40 is similar to the above device in that it is provided in the middle of the liquid pipe 28 and at the highest point thereof. The difference from the above apparatus is that the refrigerant reservoir 40 has a refrigerant inlet 42 in the upper portion of the container and a refrigerant outlet 44 in the lower portion of the container. As a result, the inflow of the refrigerant into the refrigerant liquid reservoir 40
The outflow will be smooth.

In the embodiment shown in FIG. 2 (b), the refrigerant liquid reservoir 50 is provided side by side with the condenser 22, that is, directly connected to the condenser 22 without a liquid pipe. In the configuration shown in FIG. 2C, the refrigerant liquid reservoir 60 is connected to the heat transfer tube 62 below the condenser 22.

In all of the above-mentioned embodiments, the refrigerant liquid reservoir is provided at a position as high as possible so as not to impair the height of the refrigerant liquid column that gives the refrigerant circulation driving force. Although this arrangement is desirable for obtaining high cooling capacity,
On the contrary, there are cases where the height of the refrigerant liquid column should be limited for other reasons. For example, when the portion to be cooled in which the evaporator 24 is arranged is separated from the outside world and the height of the condenser 22 becomes very high, the structure of the evaporator 24 is affected by the pressure of the refrigerant liquid column at that height. It can be unbearable. In such a case,
As shown in FIGS. 3A and 3B, the refrigerant liquid reservoir 7
0 and 80 are arranged between the condenser 22 and the evaporator 24, for example, at a height determined by the upper limit of the refrigerant driving force. As a result, the refrigerant liquid does not stay in the condenser 22, and the upper limit of the height of the refrigerant liquid column can be set to the height of the refrigerant liquid reservoir.

[Embodiment 2] FIG. 4 is another embodiment of the present invention, and is a schematic configuration diagram of a refrigeration cycle in a cooling apparatus in which a natural circulation loop is used in combination with a vapor compression refrigeration cycle. The vapor compression refrigeration cycle in this cooling device roughly includes a compressor 100, a condenser 102, an evaporator 104, and an expansion valve 106. The compressor 100 is provided in the middle of a gas pipe 108 that guides the refrigerant gas generated in the evaporator 104, 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 102 radiates heat from the overheated refrigerant gas,
This is liquefied. The refrigerant liquid is sent to the evaporator 104 side via the liquid pipe 110. The expansion valve 106 provided in front of the evaporator 104 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 104, becomes a refrigerant gas, and is sent out to the gas pipe 108 again. In addition,
The suction accumulator 112 is a device that acts as a buffer in the case of a transient phenomenon of operation or an excessive amount of refrigerant filled.

Next, the natural circulation loop will be described. Most of them are common with the vapor compression refrigeration cycle described above. The natural circulation loop includes a suction accumulator 1
12 is different from the vapor compression refrigeration cycle in that the compressor 12 and the compressor 100 are bypassed and the expansion valve 106 is bypassed. The natural circulation loop has bypass pipes 120 and 122 for these bypasses, respectively. Switching of these flow paths is performed by switching valves 124, 126, 128, 1
30. That is, when this refrigeration cycle is used as a vapor compression refrigeration cycle (referred to as a forced circulation mode), the switching valves 124 and 128 are opened and the switching valves 126 and 130 are closed. On the contrary, when the refrigeration cycle is used as a natural circulation loop (referred to as a natural circulation mode), the switching valves 126 and 130 are opened and the switching valve 12 is opened.
4, 128 is closed.

In the natural circulation loop of this apparatus, as in the above embodiment, the gravity acting on the refrigerant liquid accumulated in the liquid pipe 110 is used as the driving force for the refrigerant circulation. The refrigerant liquid is supplied to the evaporator 104 by gravity and becomes a refrigerant gas here. In the natural circulation loop, the bypass pipe 120 serves as a refrigerant gas flow path,
The refrigerant gas having a low specific gravity rises in the gas pipe 108 even when the compressor 100 is stopped, reaches the condenser 102, and becomes a refrigerant liquid in the condenser 102.

In this apparatus, a refrigerant liquid reservoir 132 having an outflow port and an inflow port is located in the middle of the liquid pipe 110 and is located in the liquid pipe 1.
10 is provided at a height connected to the condenser 102. First, this refrigerant liquid reservoir has a function of avoiding a phenomenon in which excessive refrigerant liquid accumulates in the condenser 102 at the time of low ambient temperature in the natural circulation mode similar to the first embodiment. In addition to this phenomenon in the present device, due to a change in the refrigerant liquid column height due to a change in the distribution and amount of the refrigerant liquid in the refrigerant circulation system when the forced circulation mode is switched to the natural circulation mode,
The phenomenon that the refrigerant liquid stays in the condenser 102 may occur. In order to avoid this phenomenon, the method of adjusting the amount of refrigerant in the device by taking in and out the refrigerant at the time of switching the operation mode is complicated and not realistic. The refrigerant liquid reservoir 132 has a function of avoiding this phenomenon without performing such a complicated operation. With this refrigerant liquid reservoir 132, the present device can prevent the effective heat transfer area of the condenser 102 from decreasing due to both of the above phenomena, regardless of the outside air temperature, and without performing a special operation at the time of switching the operation mode, and always condense. It is possible to provide the cooling capacity with which the performance of the container 102 is fully exhibited.

Incidentally, the suction accumulator 112
Also, although the refrigerant liquid can be accumulated, the position where it is provided is the gas pipe 108 side, and the purpose thereof is not to adjust the refrigerant liquid but to protect the compressor 100. That is, when the refrigerant liquid flows into the compressor 100 by, for example, a large amount of liquid that has not been vaporized in a transient state enters the gas pipe, the compressor 100 may be damaged. The refrigerant reservoir 132 does not have the above-described function.

[0028]

According to the present invention, excess refrigerant liquid that may be generated when the ambient temperature is low, such as in winter, or when the refrigerant circulation system is switched to the natural circulation loop, is accumulated in the refrigerant reservoir and is supplied to the condenser. As a result, the heat exchange efficiency of the condenser is always maintained at a good value and the cooling capacity is prevented from decreasing.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a refrigeration cycle in a cooling device according to the present invention using a natural circulation loop.

FIG. 2 is a partial view of a schematic configuration of a refrigeration cycle showing an installation form of a refrigerant liquid reservoir.

FIG. 3 is a schematic configuration diagram of a refrigeration cycle showing an installation form of a refrigerant liquid reservoir.

FIG. 4 is a schematic configuration diagram of a refrigeration cycle in a cooling device according to the present invention in which a natural circulation loop is used in combination with a vapor compression refrigeration cycle.

FIG. 5 is a schematic configuration diagram illustrating the principle of a conventional cooling device using a natural circulation loop.

[Explanation of symbols]

22,102 condenser, 24,104 evaporator, 26,
108 gas piping, 28,110 liquid piping, 30,13
2 Refrigerant reservoir, 100 compressor, 106 expansion valve, 1
20,122 Bypass pipe.

Claims (3)

[Claims] 1. An evaporator for absorbing heat of vaporization when a refrigerant liquid becomes a refrigerant gas from a cooled portion, a gas pipe connected to the evaporator for raising the refrigerant gas, and connected to the gas pipe, thereby A natural circulation loop including a condenser that liquefies the introduced refrigerant gas into a refrigerant liquid, and a liquid pipe that is connected to this condenser and causes the refrigerant liquid generated by this to descend by gravity and guide it to the evaporator. An air conditioner provided with a refrigerant liquid reservoir which is connected to the flow path of the refrigerant liquid and which collects the refrigerant liquid and removes the retention of the refrigerant liquid inside the condenser. 2. An evaporator which absorbs heat of vaporization when a refrigerant liquid becomes a refrigerant gas from a cooled portion, a gas pipe which is connected to the evaporator and raises the refrigerant gas, and which is connected to the gas pipe and thereby A condenser that liquefies the introduced refrigerant gas into a refrigerant liquid, a liquid pipe that is connected to this condenser and that guides the refrigerant liquid generated by this to the evaporator by descending by gravity, and the middle of the gas pipe A compressor for adiabatically compressing the refrigerant gas, a compressor bypass means for bypassing the compressor, a means for switching between the compressor and the compressor bypass means, and a refrigerant liquid inserted in the liquid pipe to reduce the pressure of the refrigerant liquid. Expansion valve and expansion valve bypass means for bypassing the expansion valve,
In a cooling device that includes a means for switching between an expansion valve and an expansion valve bypass means and is capable of switching the refrigerant circulation system between a vapor compression refrigeration cycle and a natural circulation loop, the refrigerant liquid being connected to the flow path of the refrigerant liquid, A cooling device having a refrigerant liquid reservoir for accumulating and removing retention of the liquid surface of the refrigerant inside the condenser. 3. The cooling device according to claim 1 or 2, wherein the refrigerant liquid reservoir is provided at a height of a connection position of the liquid pipe to the condenser.