JPH06265293A - Method and apparatus for heat exchanging by using intermediate refrigerant - Google Patents

Abstract

PURPOSE:To use various substances as substitute refrigerant only by adding a simple facility by recovering intermediate refrigerant sealed in a heat exchanging vessel into a pressure resistant vessel at the time of stopping a cooling operation, and introducing the refrigerant in the vessel into the exchanger at the time of starting the operation. CONSTITUTION:Ethane as intermediate refrigerant is mostly contained in a heat exchanging vessel 14 at the time of normal operation set to -55 deg.C, and ethane gas is fully fed in a pressure vessel 21. When an apparatus is stopped, a valve 22a is opened, a refrigerant pump 22b is operated, liquidlike ethane in the vessel 14 is sent and recovered to the vessel 21 through a liquid refrigerant recovery tube 22. In the case of starting the apparatus, cold fluid is fed to a cold fluid passage 15 to cool ethane in the vessel 14, a valve 23a is opened after the ethane is lowered to 3.65kg/cm<2>G of an operating temperature, and liquid ethane in the vessel 21 is returned to the vessel 14 through a liquid refrigerant introducing tube 23 while reducing the pressure by opening the valve 23a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanging method and apparatus using an intermediate refrigerant, and more particularly to a heat exchanging method and apparatus for cooling a warm fluid through an intermediate refrigerant enclosed in a sealed system.

[0002]

2. Description of the Related Art Conventionally, as one of heat exchange devices (refrigeration equipment) for cooling a fluid, a heat exchange device using an intermediate refrigerant has been known. In the heat exchange device using this intermediate refrigerant, for example, as shown in FIG. 2, the intermediate refrigerant is enclosed in a sealed container 3 having a cold fluid side heat exchanger 1 and a warm fluid side heat exchanger 2 at the top and bottom. The intermediate refrigerant is cooled by heat exchange with the cold fluid (refrigerant) flowing through the cold fluid flow path 4 in the upper cold fluid side heat exchanger 1, and is liquefied to become the lower warm fluid side heat exchanger. 2 and is heated by the warm fluid (cooled fluid) flowing through the warm fluid flow path 5 in the warm fluid side heat exchanger 2,
The process of vaporization, rising to the upper cold fluid side heat exchanger 1, and liquefying the cooling again is repeated.

In the heat exchange device using such an intermediate refrigerant, most of them use Freon (specific Freon) as the intermediate refrigerant. This CFC is widely used because it has suitable physical properties in the normal temperature range as an intermediate refrigerant. However, due to problems such as ozone layer destruction, the CFC was completely abolished at the end of 1995. It has been decided and will not be available for future use. For this reason, it is necessary to replace the intermediate refrigerant with an alternative substance (alternative refrigerant) in the CFC-using facility that is currently in operation.

[0004]

However, since the physical properties of the intermediate refrigerant are different, it is necessary to change the refrigerating equipment itself to the specifications that match the physical properties of the alternative refrigerant. That is, the design pressure of the device rises to the temperature at which heat does not enter from the outside, generally the outside air temperature, because the saturation pressure rises with the temperature of the intermediate refrigerant due to the heat entering from the outside when the device is not operating. It is set according to the maximum saturation pressure when. Therefore, when replacing the refrigerant with an alternative substance, it is necessary to consider the saturation pressure of the substance, and the saturation pressure at the operating temperature of the device and the maximum saturation pressure at the time of shutdown differ from those of the refrigerant currently in use. If too much is present, it cannot be used as an alternative refrigerant in terms of operating pressure and design pressure.

[0005] For example, current state of the device, chlorofluorocarbon intermediate refrigerant 13B1 (CBrF _3: hereinafter, simply referred to as CFC)
When the refrigerant temperature during operation is −55 ° C. and the maximum operating temperature is 30 ° C., the fluorocarbon saturation pressure at −55 ° C. is 0.14 kg / cm ² G, and 17.19 k at 30 ° C.
Since it is g / cm ² G, the design pressure of each component constituting the device, for example, the sealed container 3 is usually 23 kg / cm ²
It is manufactured as G. Here, for example, when ethane is examined as an alternative refrigerant, the saturation pressure of ethane at −55 ° C. is 3.65 kg / cm ² G and at 30 ° C. is 47 k.
Since it is g / cm ² G, the design pressure of the device exceeds 23 kg / cm ² G at the maximum operating temperature of 30 ° C.
Therefore, ethane cannot be used as an alternative refrigerant in the device having the above specifications.

On the contrary, in the case of an alternative refrigerant having a low saturation pressure at the operating temperature and a negative pressure, the sealed container or the like, which has been subjected to the internal pressure, receives the external pressure, so that the flange or the like is changed to a vacuum type. It is necessary to take measures such as doing.

Further, at present, the substances that can be used as the alternative refrigerant are limited, and as described above, it is difficult to replace only the refrigerant and continue the operation. The reality is that they have to be replaced.

Therefore, the present invention has an object to provide a heat exchange method and apparatus capable of using various substances as alternative refrigerants by simply adding simple equipment even in the present Freon refrigeration equipment having a low design pressure. I am trying.

[0009]

In order to achieve the above-mentioned object, a heat exchange method using an intermediate refrigerant according to the present invention liquefies an intermediate refrigerant enclosed in a heat exchange container by heat exchange with a cold fluid. , The warm fluid is cooled by heat exchange with the liquefied intermediate refrigerant, the intermediate refrigerant is vaporized, and the vaporized intermediate refrigerant is repeatedly liquefied by heat exchange with the cold fluid to repeat the operation. In a heat exchange method using an intermediate refrigerant for cooling, when the cooling operation is stopped, the intermediate refrigerant sealed in the heat exchange container is collected in a pressure resistant container having a higher pressure resistance than the heat exchange container, At the start of the cooling operation, the intermediate refrigerant in the pressure resistant container is introduced into the heat exchange container.

The heat exchange device using the intermediate refrigerant of the present invention is a heat exchange device using an intermediate refrigerant in which a cold fluid passage and a warm fluid passage are arranged in a heat exchange container in which the intermediate refrigerant is sealed. A pressure-resistant container having a higher pressure resistance than the heat-exchange container is connected to the heat-exchange container, and the pressure-resistant container and the heat-exchange container are recovered as an intermediate refrigerant in the heat-exchange container when the apparatus is stopped. And a flow path for introducing the intermediate refrigerant in the pressure resistant container into the heat exchange container when the apparatus is used.

[0011]

[Operation] According to the above configuration, since the intermediate refrigerant is collected in the pressure resistant container having a high design pressure when the apparatus is stopped, the pressure increase in the heat exchange container can be suppressed, and the heat exchange container having a low design pressure can be suppressed. Can be used.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail based on an embodiment shown in the drawings. FIG. 1 shows an embodiment of the heat exchange apparatus of the present invention, and the heat exchange section includes an upper cold fluid side heat exchanger 11 and a lower warm fluid side heat exchanger 12 as in the conventional case. It has a sealed container (heat exchange container) 14 configured to communicate with each other through a pipe 13. That is, this heat exchange section has the same configuration as that of the heat exchange device shown in FIG. 2, and the refrigerant sealed in the heat exchange container 14 is the same as the above-mentioned heat on the cold fluid side. Cold fluid flow path 15 in exchanger 11
Is cooled by heat exchange with a cold fluid flowing through, liquefies and flows down to the lower warm fluid side heat exchanger 12, and is heated by the warm fluid flowing through the warm fluid flow path 16 in the warm fluid side heat exchanger 12, The process of vaporization, rising to the upper cold fluid side heat exchanger 11, and liquefying the cooling again is repeated.

The heat exchange container 14 has a pressure resistant container 21 having a design pressure higher than that of the heat exchange container 14.
Is attached. The pressure-resistant container 21 has three pipes serving as a flow path of an intermediate refrigerant, that is, a liquid refrigerant recovery pipe 22 having a valve 22a and a refrigerant pump 22b, a liquid refrigerant introducing pipe 23 having a valve 23a, and a valve 24a. It is connected to the heat exchange container 14 via a gas refrigerant introduction pipe 24, and most of the intermediate refrigerant is collected in the pressure resistant container 21 when the apparatus is stopped, and most of the intermediate refrigerant is heated during normal operation of the apparatus. It is transferred to the exchange container 14.

Hereinafter, a case where ethane is used as an alternative refrigerant for the Freon 13B1 will be described as an example. As described above, the design pressure of the heat exchange container 14 when the Freon 13B1 is used as a refrigerant is usually set to 23 kg / cm ² G, and the saturation pressure at 30 ° C. is 47 k as it is.
It is not possible to use g / cm ² G ethane as a refrigerant.

First, during normal operation at −55 ° C., most of ethane as an intermediate refrigerant is in the heat exchange container 14 with the valves 22a, 23a, 24a closed. The pressure vessel 21 is filled with ethane gas at a pressure substantially the same as the operating pressure of the heat exchange vessel 14, that is, the saturated pressure of ethane at −55 ° C. of 3.65 kg / cm ² G. The ethane in the heat exchange container 14 is liquefied in the cold fluid side heat exchanger 11 and is liquefied from the pipe 13 to the warm fluid side heat exchanger 1.
The operation of flowing down to 2, vaporized in the warm fluid side heat exchanger 12 and rising from the pipe 13 to the cold fluid side heat exchanger 11 is repeated, and the cold heat of the cold fluid is transmitted to the warm fluid via ethane,
The warm fluid is indirectly cooled. Since the ethane saturation pressure at this time is 3.65 kg / cm ² G, there is no pressure problem.

Next, when the apparatus is stopped, the valve 22a is opened and the refrigerant pump 22b is operated,
Liquid ethane in the heat exchange container 14 is sent to and collected in the pressure resistant container 21 via the liquid refrigerant recovery pipe 22. The liquid ethane can be recovered by using the liquid head depending on the height difference between the heat exchange container 14 and the pressure resistant container 21 in consideration of the positional relationship between the heat exchange container 14 and the pressure resistant container 21. Further, by opening the valve 24a during liquid feeding, the pressure difference between the two can be adjusted. When most of the liquid ethane is collected in the pressure resistant container 21, the valve 22a is closed and the refrigerant pump 22b is stopped.

After the apparatus is stopped, the temperature inside the heat exchange container 14 and the pressure resistant container 21 rises due to the invasion of heat from the outside, and when the temperature of ethane rises to, for example, 30 ° C., the partial vaporization and the liquid temperature increase as the liquid temperature rises. The volume expands to a saturated state at 30 ° C., and the pressure inside the pressure vessel 21 in which the liquid ethane is recovered becomes about 47 kg / cm ² G. Therefore, there is no problem even if the temperature of ethane rises to 30 ° C. by setting the design pressure of the pressure vessel 21 to about 53 kg / cm ² G, for example.

On the other hand, almost no liquid ethane is present in the heat exchange container 14 and the ethane gas is full, and liquid ethane remains at the bottom of the heat exchange container 14, the valve 22a, pipes and the like. Even if the amount is small, the entire amount is vaporized with the rise in temperature. Therefore, the pressure rise in the heat exchange container 14 is proportional to the rise in temperature, and the pressure in the heat exchange container 14 at 30 ° C. is about 6. It becomes ² kg / cm ² G. Therefore, the design pressure of the heat exchange container 14 is 23 kg /
There is a sufficient margin up to cm ² G.

Next, when the apparatus is started up, first, a cold fluid is caused to flow through the cold fluid passage 15 to cool the ethane in the heat exchange container 14, and the ethane is at an operating temperature of 3.65 kg / cm ² G.
After that, the valve 23a is opened to reduce the pressure, and the liquid ethane in the pressure resistant container 21 is returned into the heat exchange container 14 through the liquid refrigerant introducing pipe 23. At this time, since the pressure inside the pressure vessel 21 is high, the liquid ethane is pushed out by the ethane gas inside the vessel and transferred into the heat exchange vessel 14. When the completion of the transfer of liquid ethane is detected by the detection mechanism (not shown), the valve 2
3a is closed, the valve 24a is opened, and high-pressure ethane gas in the pressure vessel 21 is depressurized and introduced into the heat exchange vessel 14 through the gas refrigerant introduction pipe 24. When the pressure in the pressure vessel 21 and the pressure in the heat exchange vessel 14 become equal, the valve 24a is closed, the ethane return operation is completed, and normal operation is started. Start cooling the fluid. After that, when the pressure in the pressure vessel 21 rises,
The valve 24a is opened to send the ethane gas in the pressure resistant container 21 into the heat exchange container 14 to equalize the pressure. Finally, the temperature of the ethane gas in the pressure vessel 21 is the outside air temperature and the pressure is the same as that in the heat exchange vessel 14.

As described above, the heat exchange container 14 used in the conventional Freon refrigeration equipment is continuously provided with the pressure resistant container 21 manufactured at a design pressure according to the alternative refrigerant, and the heat exchange container 14 is stopped when the apparatus is stopped. By collecting the liquid refrigerant inside the pressure resistant container 21, the pressure rise in the heat exchange container 14 can be suppressed, and the refrigerant can be transferred from the Freon to another refrigerant by directly using the heat exchange container 14 and the piping attached to the heat exchange container 14. It becomes possible to change to a substance.

The present invention is not limited to the above-mentioned embodiment. For example, a substance other than ethane can be used as an intermediate refrigerant depending on the operating temperature and the like, and the structure of the heat exchange section is Although the shell and tube heat exchanger is illustrated in the above embodiment, other types such as a plate fin heat exchanger can be used, and the cold fluid side heat exchanger and the warm fluid side heat exchanger are combined into one. It is also possible to form it with a container, connect it to each other with a plurality of pipes, or arrange a plurality of heat exchangers. Further, the pipe connecting the pressure resistant container and the heat exchange container can be arbitrarily set.

Further, in addition to the solution of the alternative CFC problem, it suffices that the design pressure of the pressure vessel be adapted to the intermediate refrigerant to be used. Therefore, even when different operating temperatures and operating pressures are used and different intermediate refrigerants are used, heat It is possible to design the exchange part in common.

[0023]

As described above, according to the present invention,
Various substances can be used as alternative refrigerants only by connecting a pressure vessel for recovering the intermediate refrigerant to a conventional heat exchange device using the intermediate refrigerant and connecting them with appropriate pipes.
Therefore, even in the conventional CFC refrigeration equipment in which the heat exchange container enclosing the intermediate refrigerant has a low design pressure, it is possible to deal with various alternative refrigerants simply by adding piping including a pressure container and valve and making a simple modification. Therefore, it is not necessary to replace the entire refrigeration equipment.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram showing an example of a conventional device.

[Explanation of symbols]

11 ... Cold fluid side heat exchanger, 12 ... Warm fluid side heat exchanger, 1
4 ... Heat exchange container, 15 ... Cold fluid channel, 16 ... Warm fluid channel, 21 ... Pressure vessel, 22 ... Liquid refrigerant recovery pipe, 23 ... Liquid refrigerant introduction pipe, 24 ... Gas refrigerant introduction pipe

Claims (2)

[Claims] 1. An intermediate refrigerant enclosed in a heat exchange container is liquefied by heat exchange with a cold fluid, and a warm fluid is cooled by heat exchange with the liquefied intermediate refrigerant, and the intermediate refrigerant is vaporized. A heat exchange method using an intermediate refrigerant that cools the warm fluid by repeating an operation of liquefying the vaporized intermediate refrigerant by heat exchange with the cold fluid, in the heat exchange container when the cooling operation is stopped. Is characterized in that the intermediate refrigerant sealed in is collected in a pressure resistant container having a higher pressure resistance than the heat exchange container, and at the start of the cooling operation, the intermediate refrigerant in the pressure resistant container is introduced into the heat exchange container. And a heat exchange method using an intermediate refrigerant. 2. A heat exchange device using an intermediate refrigerant in which a cold fluid passage and a warm fluid passage are arranged in a heat exchange container containing an intermediate refrigerant, wherein the heat exchange container has a pressure resistance higher than that of the heat exchange container. A pressure-resistant container having high strength is provided in series, and the pressure-resistant container and the heat exchange container are connected to each other by a flow path for collecting the intermediate refrigerant in the heat-exchange container when the device is stopped into the pressure-resistant container and an intermediate part in the pressure container when the device is used. A heat exchange device using an intermediate refrigerant, characterized in that it is connected to a flow path for introducing the refrigerant into a heat exchange container.