JP2015190733A - Evaporator of turbo refrigerator, and turbo refrigerator including evaporator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide an evaporator that can improve a heat transfer coefficient.SOLUTION: An evaporator comprises: heat transfer pipes 35 in which fluid to be cooled flows; and a gas-liquid separator 41 that is arranged in a can body 31 and separates refrigerant gas and refrigerant liquid. The gas-liquid separator 41 comprises: a flow passage block 42 in which a gas-liquid refrigerant flow passage 45 is formed; and refrigerant gas guide members 50 connected to the flow passage block 42. Refrigerant gas flow passages 51 that communicate with the gas-liquid refrigerant flow passage 45 are formed in the refrigerant gas guide members 50, and the refrigerant gas flow passages 51 extend upward along an inner surface of the can body 31.

Description

  The present invention relates to an evaporator of a turbo refrigerator, and more particularly to an evaporator that exhibits a refrigeration effect by evaporating refrigerant from heat to be cooled such as cold water. The present invention also relates to a turbo refrigerator equipped with such an evaporator.

  Conventionally, a turbo refrigerator used in a refrigeration air conditioner or the like is configured by a closed system in which a refrigerant is enclosed, an evaporator that takes heat from cold water (fluid to be cooled) and evaporates the refrigerant to exert a refrigeration effect; A compressor that compresses the refrigerant gas evaporated in the evaporator to form a high-pressure refrigerant gas; a condenser that cools and condenses the high-pressure refrigerant gas with cooling water (cooling fluid); and depressurizes the condensed refrigerant. An expansion valve (expansion mechanism) that is expanded by being connected by a refrigerant pipe. When a multistage compressor that compresses refrigerant gas in multiple stages with a multistage impeller is used as the compressor, the refrigerant gas generated in the economizer that is an intermediate cooler installed in the refrigerant pipe between the condenser and the evaporator Is introduced into an intermediate stage of the compressor (intermediate part of a multistage impeller).

  A turbo chiller employing such a multistage compression refrigeration cycle depressurizes the refrigerant liquid discharged from the economizer by an expansion mechanism. A part of the decompressed refrigerant liquid evaporates and becomes a gas-liquid two-phase refrigerant and is supplied into the evaporator from the lower part of the evaporator. FIG. 8 is a cross-sectional view showing the inside of the evaporator. A heat transfer tube 101 is disposed inside the evaporator, and cold water (cooled fluid) flows through the heat transfer tube 101. The refrigerant takes heat from the cold water in the heat transfer tube 101 and evaporates, and is transferred to the compressor as refrigerant gas.

  However, the refrigerant gas generated in the process of being depressurized by the expansion mechanism not only contributes to freezing in the evaporator, but as shown in FIG. 8, the refrigerant gas clings to the heat transfer tube 101 of the evaporator, thereby There is a problem that a dry surface is generated, and the efficiency of the centrifugal chiller is reduced as the evaporation pressure is reduced.

  There are several methods for reducing the amount of refrigerant gas that does not contribute to refrigeration and improving the performance of the evaporator, which have been practiced conventionally. The first method for reducing the refrigerant gas is to reduce the pressure difference between the economizer and the evaporator. The amount of refrigerant gas that evaporates when the pressure is reduced by the expansion mechanism depends on the pressure difference before and after the expansion mechanism. Therefore, by reducing the pressure difference between the economizer and the evaporator, the amount of refrigerant gas generated when the pressure is reduced can be reduced.

  FIG. 9A is a Mollier diagram showing a general economizer cycle, and FIG. 9B is a Mollier diagram showing an economizer cycle in which the pressure difference between the economizer and the evaporator is reduced. In FIG. 9 (a), the pressure difference between the economizer and the evaporator is almost the same as the pressure difference between the condenser and the economizer, whereas in FIG. 9 (b), the pressure between the economizer and the evaporator. The difference is smaller than the pressure difference between the condenser and the economizer. As a result, the amount of refrigerant gas generated when the pressure is reduced by the expansion mechanism can be reduced.

  A second method for reducing the refrigerant gas is to dispose a gas-liquid separator upstream of the evaporator. After the refrigerant liquid discharged from the economizer is decompressed by the expansion mechanism, the refrigerant that has become a gas-liquid two-phase is introduced into the gas-liquid separator. Then, only the refrigerant liquid is introduced into the evaporator, and the refrigerant gas is introduced in the vicinity of the suction pipe of the multistage compressor. As a result, the refrigerant gas clings to the heat transfer tube of the evaporator, thereby generating a dry surface on the heat transfer tube and avoiding a decrease in the efficiency of the turbo refrigerator due to a decrease in the evaporation pressure.

  A third way to reduce the refrigerant gas is to increase the heat transfer area of the evaporator. Specifically, the efficiency of the evaporator as a heat exchanger is improved by increasing the number of heat transfer tubes.

JP 2012-163243 A

However, the first to third methods described above also have the following drawbacks.
In the first method described above, when the economizer pressure, which is an intermediate pressure, is brought close to the evaporator pressure, the head ratio of the front and rear impellers in the multistage compressor is not 50:50. For this reason, in order to correct the head balance, it is necessary to optimize the impeller of the compressor (review of the shape).

  In the second method described above, since a gas-liquid separator is added, a refrigerant corresponding to the volume of the container of the gas-liquid separator and the additional piping is required. For this reason, when a refrigerant with a high unit price is used, cost increases.

  In the third method described above, increasing the number of heat transfer tubes using copper with a high unit price leads to high costs. Furthermore, increasing the number of heat transfer tubes also leads to a decrease in the heat transfer rate associated with a decrease in the flow rate of the cold water in the tube, and is not a fundamental solution.

  Then, an object of this invention is to provide the evaporator which can improve a heat transfer rate at low cost. Moreover, an object of this invention is to provide the turbo refrigerator provided with such an evaporator.

  In order to achieve the above object, one aspect of the present invention is an evaporator that evaporates a refrigerant by removing heat from a fluid to be cooled, the can body, a plate member that closes both ends of the can body, A heat transfer tube disposed in the can body and through which the fluid to be cooled flows; and a gas-liquid separator disposed in the can body and separating the refrigerant gas and the refrigerant liquid, the gas-liquid separator comprising: And a flow path block having a gas-liquid refrigerant flow path formed therein, and at least one refrigerant gas guide member connected to the flow path block, wherein the gas-liquid refrigerant is disposed inside the refrigerant gas guide member. A refrigerant gas channel communicating with the channel is formed, and the refrigerant gas channel extends upward along the inner surface of the can body.

In a preferred aspect of the present invention, a plurality of the refrigerant gas guide members are connected to both side surfaces of the flow path block.
In a preferred aspect of the present invention, the flow path block has a refrigerant liquid outlet communicating with the gas-liquid refrigerant flow path.
In a preferred aspect of the present invention, the refrigerant liquid outlet is disposed at a lower portion of the side surface of the flow path block, and the refrigerant gas guide member is connected to an upper portion of the side surface of the flow path block. And
In a preferred aspect of the present invention, the refrigerant gas guide member has a refrigerant liquid outlet communicating with the gas-liquid refrigerant flow path.

  Another aspect of the present invention is the above evaporator in which heat is taken from a fluid to be cooled and the refrigerant evaporates to exert a refrigeration effect, a multistage turbo compressor that compresses the refrigerant by a multistage impeller, and compressed refrigerant gas A condenser that cools and condenses the refrigerant with a cooling fluid, and an economizer that is an intermediate cooler that supplies a refrigerant gas generated by evaporating a part of the condensed refrigerant liquid to an intermediate portion of the multistage compression stage of the multistage turbo compressor It is a turbo refrigerator equipped with.

The present invention has the following effects.
(1) The gas-liquid two-phase refrigerant is gas-liquid separated in the evaporator, and the refrigerant gas is guided upward along the inner surface of the can body so as to avoid the heat transfer tube. Thus, since contact with refrigerant gas and a heat exchanger tube is avoided, the heat transfer rate of an evaporator improves. Therefore, the evaporation pressure increases and the efficiency of the refrigerator is improved.
(2) Since the gas-liquid separator is disposed inside the evaporator, an increase in the volume of the refrigerant cycle can be minimized. Therefore, the amount of additional necessary refrigerant is minimized, and the efficiency of the evaporator can be improved while preventing an increase in cost.
(3) Unlike conventional gas-liquid separators arranged outside the evaporator, the gas-liquid separator is arranged inside the evaporator, so no piping is required to connect the gas-liquid separator and the evaporator. It becomes.
(4) Since it is not necessary to increase the number of heat transfer tubes, an increase in cost is avoided even if heat transfer tubes made of an expensive material such as copper are used.

FIG. 1 is a schematic view showing an embodiment of a turbo refrigerator. FIG. 2 is a front sectional view showing the first embodiment of the evaporator. FIG. 3 is a side sectional view showing the first embodiment of the evaporator. FIG. 4 is a perspective view showing the inside of the can body. FIG. 5 is a front cross-sectional view showing a second embodiment of the evaporator. FIG. 6 is a side sectional view showing a second embodiment of the evaporator. FIG. 7 is a perspective view showing the inside of the can body. FIG. 8 is a cross-sectional view showing the inside of the evaporator. FIG. 9A is a Mollier diagram showing a general economizer cycle, and FIG. 9B is a Mollier diagram showing an economizer cycle in which the pressure difference between the economizer and the evaporator is reduced.

  Hereinafter, an embodiment of an evaporator according to the present invention and a turbo refrigerator including the evaporator will be described with reference to FIGS. 1 to 7. 1 to 7, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic view showing an embodiment of a turbo refrigerator. As shown in FIG. 1, a turbo refrigerator includes a turbo compressor 1 that compresses refrigerant, a condenser 2 that cools and compresses the compressed refrigerant gas with cooling water (cooling fluid), and cold water (cooled fluid). ), The evaporator 3 which evaporates the refrigerant and exhibits the refrigeration effect, and the economizer 4 which is an intermediate cooler disposed between the condenser 2 and the evaporator 3.

  The turbo compressor 1, the condenser 2, the economizer 4, and the evaporator 3 are connected by refrigerant pipes 5A, 5B, 5C, and 5D through which the refrigerant circulates. More specifically, the turbo compressor 1 and the condenser 2 are connected by a refrigerant pipe 5A, the condenser 2 and the economizer 4 are connected by a refrigerant pipe 5B, and the economizer 4 and the evaporator 3 are connected by a refrigerant pipe 5C. The evaporator 3 and the turbo compressor 1 are connected by a refrigerant pipe 5D. Expansion valves 20 and 21 are provided in the refrigerant pipe 5B and the refrigerant pipe 5C, respectively.

  In the embodiment shown in FIG. 1, the turbo compressor 1 is composed of a multistage turbo compressor. That is, the multi-stage turbo compressor is composed of a two-stage turbo compressor, and includes a first-stage impeller 11, a second-stage impeller 12, and a compressor motor 13 that rotates the impellers 11 and 12. . On the suction side of the first stage impeller 11, a suction vane 14 for adjusting the suction flow rate of the refrigerant gas to the impellers 11 and 12 is provided.

  The turbo compressor 1 includes a gear casing 15 that accommodates a bearing and a speed increaser, and an oil tank 16 for supplying oil to the bearing and the speed increaser is provided below the gear casing 15. The gear casing 15 is communicated with a suction portion of the turbo compressor 1 by a pressure equalizing pipe 17. The turbo compressor 1 is connected to the economizer 4 by a refrigerant pipe 8, and the refrigerant gas separated by the economizer 4 is an intermediate portion (in this example, two stages) of the multistage compression stage of the turbo compressor 1 (in this example). A portion between the first stage impeller 11 and the second stage impeller 12) is introduced.

  In the refrigeration cycle of the turbo chiller configured as shown in FIG. 1, the refrigerant circulates through the turbo compressor 1, the condenser 2, the economizer 4, and the evaporator 3, and chilled water is generated by the cold heat source obtained by the evaporator 3. The amount of heat from the evaporator 3 that is manufactured and corresponds to the load and taken into the refrigeration cycle and the amount of heat corresponding to the work of the turbo compressor 1 supplied from the motor 13 are released to the cooling water supplied to the condenser 2. Is done. On the other hand, the refrigerant gas separated by the economizer 4 is introduced into an intermediate portion of the multistage compression stage of the turbo compressor 1, merged with the refrigerant gas from the first stage impeller 11 and compressed by the second stage impeller 12. . According to the two-stage compression single stage economizer cycle, since the refrigeration effect by the economizer 4 is added, the refrigeration effect is increased by that amount, and the efficiency of the refrigeration effect can be improved compared to the case where the economizer 4 is not installed. it can.

  Next, the evaporator 3 will be described in more detail. FIG. 2 is a front cross-sectional view showing the first embodiment of the evaporator 3, and FIG. 3 is a side cross-sectional view showing the first embodiment of the evaporator 3. The evaporator 3 includes a cylindrical can body 31, a plate member 33 that closes both ends of the can body 31, a heat transfer pipe 35 that is disposed in the can body 31, and in which cold water (fluid to be cooled) flows, and refrigerant gas And a gas-liquid separator 41 for separating the refrigerant liquid. The heat transfer tube 35 is supported by a plurality of support plates 37 disposed in the can body 31. In FIG. 3, the heat transfer tube 35 is schematically drawn. A demister 38 is disposed above the heat transfer tube 35.

  The gas-liquid separator 41 is disposed in the can body 31. The gas-liquid separator 41 includes a channel block 42 in which a gas-liquid refrigerant channel 45 is formed, and a plurality of refrigerant gas guide members 50 connected to the channel block 42. The flow path block 42 is disposed below the heat transfer tube 35, and extends along the longitudinal direction of the can body 31. The channel block 42 is fixed to the bottom surface of the can body 31. An end of a refrigerant pipe 5 </ b> C extending from the economizer 4 is connected to the bottom center of the can body 31. The refrigerant pipe 5C communicates with the gas-liquid refrigerant flow path 45 of the flow path block 42, and the gas-liquid two-phase refrigerant is introduced into the gas-liquid refrigerant flow path 45 through the refrigerant pipe 5C.

  FIG. 4 is a perspective view showing the inside of the can body 31. In order to make the internal configuration easy to see, the heat transfer tube 35 is not shown in FIG. In the present embodiment, ten refrigerant gas guide members 50 are connected to both side surfaces of the flow path block 42. More specifically, five refrigerant gas guide members 50 are connected to one side surface of the flow path block 42, and the other five refrigerant gas guide members 50 are connected to the other side surface of the flow path block 42. These refrigerant gas guide members 50 are fixed to the inner surface of the can body 31.

  In each refrigerant gas guide member 50, a refrigerant gas channel 51 communicating with the gas-liquid refrigerant channel 45 is formed. The refrigerant gas channel 51 extends upward along the inner surface of the can body 31. A refrigerant gas outlet 53 is formed at the upper end of the refrigerant gas guide member 50. The refrigerant gas outlet 53 is located outside the heat transfer tube 35 so that the refrigerant gas emitted from the refrigerant gas outlet 53 does not contact the heat transfer tube 35. The lower end of the refrigerant gas guide member 50 is connected to the upper part of both side surfaces of the flow path block 42. A plurality of refrigerant liquid outlets 46 communicating with the gas-liquid refrigerant flow path 45 are formed at lower portions on both side surfaces of the flow path block 42, and these refrigerant liquid outlets 46 are equally spaced along the longitudinal direction of the can body 31. Is arranged. By forming the refrigerant liquid outlet 46 in the lower part, it is possible to avoid introduction of refrigerant gas having a small specific gravity into the can body 31. Further, by connecting the lower end of the refrigerant gas guide member 50 to the upper part of both side surfaces of the flow path block 42, it is possible to avoid the refrigerant liquid accompanying the refrigerant gas and introducing it into the refrigerant gas flow path 51.

  The gas-liquid two-phase refrigerant is introduced into the gas-liquid refrigerant channel 45 from the center of the bottom surface of the can body 31. The refrigerant liquid separated from the refrigerant gas is discharged from the plurality of refrigerant liquid outlets 46 into the can body 31 and comes into contact with the heat transfer tube 35. On the other hand, the refrigerant gas separated from the refrigerant liquid is guided to the refrigerant gas channel 51. Since there is no opening on the upper surface of the channel block 42, all the refrigerant gas in the gas-liquid refrigerant channel 45 is guided to the refrigerant gas channel 51.

  The refrigerant gas rises in the refrigerant gas flow path 51 along the inner surface of the can body 31 and is discharged from the refrigerant gas outlet 53 to the inside of the can body 31. Since the refrigerant gas outlet 53 is located outside the heat transfer tube 35, the refrigerant gas is introduced into a region where the heat transfer tube 35 is not present. With such a configuration, the refrigerant gas does not contact the heat transfer tube 35 and the refrigerant gas does not cling to the heat transfer tube 35, so that a dry surface is not generated on the heat transfer tube 35. Further, since the gas-liquid separator 41 is provided inside the can body 31, a refrigerant corresponding to the volume of the container of the gas-liquid separator and the volume of the additional pipe can be obtained as compared with the case where the gas-liquid separator is arranged outside. unnecessary. Therefore, without increasing the cost, the heat transfer coefficient of the evaporator 3 is improved, the evaporation pressure is increased, and the efficiency of the refrigerator is improved.

  The refrigerant gas rises in the can body 31 and passes through the demister 38 and flows into the refrigerant pipe 5D (see FIG. 1). The refrigerant liquid separated from the refrigerant gas is discharged from the plurality of refrigerant liquid outlets 46 into the can body 31 and comes into contact with the heat transfer tube 35. Since the plurality of refrigerant liquid outlets 46 are arranged at equal intervals on both side surfaces along the longitudinal direction of the evaporator 3, the refrigerant liquid uniformly contacts the heat transfer tube 35 through the plurality of refrigerant liquid outlets 46. The efficiency of the evaporator 3 is optimized.

  FIG. 5 is a front cross-sectional view showing a second embodiment of the evaporator 3, FIG. 6 is a side cross-sectional view showing the second embodiment of the evaporator 3, and FIG. It is a perspective view which shows an inside. In order to make the internal configuration easy to see, the heat transfer tube 35 is not shown in FIG. The configuration of the present embodiment that is not specifically described is the same as that of the above-described first embodiment, and thus redundant description thereof is omitted. In the present embodiment, a pair of horizontally long refrigerant gas guide members 50 are connected to both side surfaces of the flow path block 42. One refrigerant gas outlet 53 is formed at the upper end of each refrigerant gas guide member 50. The refrigerant gas guide member 50 has a plurality of refrigerant liquid outlets 46 communicating with the gas-liquid refrigerant flow path 45. These refrigerant liquid outlets 46 are formed on the inner wall of the refrigerant gas guide member 50.

  The gas-liquid two-phase refrigerant is introduced into the gas-liquid refrigerant channel 45 from the center of the bottom surface of the can body 31. The refrigerant liquid is introduced into the refrigerant gas flow path 51 together with the refrigerant gas, and only the refrigerant liquid is discharged from the plurality of refrigerant liquid outlets 46 to the inside of the can body 31. The refrigerant gas separated from the refrigerant liquid rises in the refrigerant gas flow path 51 along the inner surface of the can body 31, and is discharged from the refrigerant gas outlet 53 to the inside of the can body 31. Since the refrigerant gas outlet 53 is located outside the heat transfer tube 35, the refrigerant gas is introduced into a region where the heat transfer tube 35 is not present. With such a configuration, the refrigerant gas does not contact the heat transfer tube 35 and the refrigerant gas does not cling to the heat transfer tube 35, so that a dry surface is not generated on the heat transfer tube 35. Further, since the gas-liquid separator 41 is provided inside the can body 31, a refrigerant corresponding to the volume of the container of the gas-liquid separator and the volume of the additional pipe can be obtained as compared with the case where the gas-liquid separator is arranged outside. unnecessary. Furthermore, since the structure is simpler than that of the first embodiment, the can body can be easily assembled. Therefore, without increasing the cost, the heat transfer coefficient of the evaporator 3 is improved, the evaporation pressure is increased, and the efficiency of the refrigerator is improved.

  Although the embodiment of the present invention has been described so far, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention may be implemented in various different forms within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 1 Turbo compressor 2 Condenser 3 Evaporator 4 Economizer 5 Refrigerant piping 11 First stage impeller 12 Second stage impeller 13 Compressor motor 14 First stage suction vane 15 Gear casing 16 Oil tank 17 Pressure equalizing pipes 20, 21 Expansion valve 31 Can body 33 Plate member 35 Heat transfer tube 37 Support plate 38 Demister 41 Gas-liquid separator 42 Channel block 45 Gas-liquid refrigerant channel 46 Refrigerant liquid outlet 50 Refrigerant gas guide member 51 Refrigerant gas channel 53 Refrigerant gas outlet

Claims (6)

An evaporator that evaporates the refrigerant by removing heat from the fluid to be cooled,
A can body,
A plate material for closing both ends of the can body;
A heat transfer tube disposed in the can body and through which the fluid to be cooled flows;
A gas-liquid separator disposed in the can body and separating the refrigerant gas and the refrigerant liquid;
The gas-liquid separator is
A flow path block having a gas-liquid refrigerant flow path formed therein;
And at least one refrigerant gas guide member connected to the flow path block,
Inside the refrigerant gas guide member, a refrigerant gas flow path communicating with the gas-liquid refrigerant flow path is formed,
The evaporator, wherein the refrigerant gas flow path extends upward along the inner surface of the can body.   The evaporator according to claim 1, wherein a plurality of the refrigerant gas guide members are connected to both side surfaces of the flow path block.   The evaporator according to claim 1, wherein the flow path block has a refrigerant liquid outlet communicating with the gas-liquid refrigerant flow path. The refrigerant liquid outlet is disposed at the lower part of the side surface of the flow path block,
The evaporator according to claim 3, wherein the refrigerant gas guide member is connected to an upper portion of a side surface of the flow path block.   The evaporator according to claim 1, wherein the refrigerant gas guide member has a refrigerant liquid outlet communicating with the gas-liquid refrigerant flow path. An evaporator that draws heat from the fluid to be cooled and evaporates the refrigerant to exert a refrigeration effect;
A multi-stage turbo compressor that compresses the refrigerant with a multi-stage impeller; and
A condenser that cools and compresses the compressed refrigerant gas with a cooling fluid;
In a centrifugal chiller comprising an economizer that is an intermediate cooler that supplies refrigerant gas generated by evaporating a part of the condensed refrigerant liquid to an intermediate part of the multistage compression stage of the multistage turbo compressor,
The turbo chiller, wherein the evaporator is the evaporator according to any one of claims 1 to 5.

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