JPH07127934A - Cascade freezing device - Google Patents

Abstract

PURPOSE:To reduce the size of a first main compressor, which forms an energy saving type by a method wherein after a refrigerant delivered from a high stage compressor is liquefied by a condenser, a refrigerant pressure is reduced to the suction pressure of the high stage compressor by an expansion valve and introduced to the coil of a delivery gas cooler and heat-exchanged with delivery gas on the low origin side. CONSTITUTION:A first unit compressor 1 comprises a recipro or a screw type two-stage compressor and the delivery pipe of a compressor la at a low stage (a front stage) is connected to the suction pipe of a compressor 1b at a high stage (a rear stage). The delivery pipe of the compressor 1b at the high stage is connected to the inlet of a condenser 2 through which cooling water flows to a coil 2a. A refrigerant liquefied by the condenser 2 is reduced in a pressure by an expansion valve 6 and fed to a coil 7a of a desuperheater (a delivery gas cooler) 7 for heat-exchange. A refrigerant vaporized by the desuperheater 7 is sucked to the compressor 1b at the high stage. This constitution reduces the quantity of heat of a cascade condenser 9 cooled at the low stage of the first main compressor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-source refrigerating apparatus used for connecting a plurality of refrigerators in multiple stages to cool them to an ultralow temperature.

[0002]

2. Description of the Related Art Recently, the freezing storage temperature of fresh fish such as tuna is becoming as low as -60.degree. C. to -70.degree. C., and a multi-source freezing device is required to cool the fresh fish storage to such a low temperature. Is used.

In this multi-source refrigeration system, the condenser of the high-side refrigerator is cooled by cooling water, and the cooling coil on the high-side is condensed with the refrigerant gas discharged from the compressor of the low-side refrigerator. By connecting to a cascade condenser of a condenser and connecting multiple refrigerators with a heat exchanger (cascade condenser), the heat load of the freezer etc. is cooled to a very low temperature by the cooler on the low side. Is. When the refrigerators are connected in two stages, the high-source side refrigerator is the first source refrigerator and the low-source side refrigerator is the second source refrigerator.

In such a multi-source refrigerating apparatus, conventionally, Freon R13 or R503 has been used as the refrigerant of the second source refrigerator. Therefore, the discharge gas compressed by the second source compressor is
The temperature is not so high, air cooling in a small device,
Large equipment either cooled it with water or sent it to the cascade condenser without cooling anything.

[0005]

Conventionally, Freon R13 or R503 was used as the refrigerant of the second source refrigerator,
Due to CFC regulations, these refrigerants can no longer be used.
Therefore, it became necessary to use HFC23 as an alternative refrigerant. However, the discharge gas temperature of the HFC 23 compressed by the compressor rises by about 20 to 30 ° C. as compared with the conventional refrigerant. Therefore, in order to keep the discharge gas temperature on the second source side low, the compressor on the first source side should be a two-stage compressor, and
It is necessary to lower the compression ratio or condensing pressure of the former compressor.

It is an object of the present invention to effectively operate the above-mentioned two-stage compressor, and thereby to downsize the device and save energy.

[0007]

To achieve this object, a multi-source refrigeration system of the present invention is a multi-source refrigeration system in which a plurality of refrigerators are connected in multiple stages by a cascade condenser forming a condenser. A discharge gas cooler that pre-cools the discharge gas from the low side compressor is installed between the discharge side of the machine and the inlet of the cascade condenser, and the high side compressor is connected to the low stage compressor and the high stage compressor. It consists of a two-stage compressor, and the refrigerant discharged from this high-stage compressor is liquefied by a condenser, and then it is decompressed to the suction pressure of the high-stage compressor by an expansion valve and led to the coil of the discharge gas cooler. The heat is exchanged with the low-side discharge gas.

[0008]

According to the above structure, the heat quantity of the cascade condenser cooled by the low-stage compressor of the high-pressure side compressor is reduced, and the high-pressure side compressor can be downsized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the multi-source refrigerating apparatus according to the present invention will be described below in detail with reference to the drawings. An example of this multiple refrigeration system is shown in the system diagram of FIG. In this figure, a first source compressor 1 is composed of a reciprocating or screw type two-stage compressor, and a discharge pipe of a low-stage (pre-stage) compressor 1a is a suction pipe of a high-stage (post-stage) compressor 1b. Connected to. The discharge pipe of the high-stage compressor 1b is connected to the inlet of the condenser 2 through which the cooling water is passed through the coil 2a. The refrigerant liquefied in the condenser 2 is decompressed by the expansion valve 6 and sent to the coil 7a of the de-super heater (discharge gas cooler) 7 for heat exchange. The refrigerant evaporated by the de-super heater 7 is sucked into the high-stage compressor 1b.

The outlet of the condenser 2 is connected to the inlet of the coil 4a of the intercooler 4 via the expansion valve 3. The outlet of the coil 4a of the intercooler 4 is connected to the suction pipe of the high-stage compressor 1b. The outlet of the condenser 2 is connected to the inlet of the intercooler 4, and the outlet of the intercooler 4 is connected to the inlet of the coil 9a of the cascade condenser 9 via the solenoid valve and the expansion valve 8. This cascade capacitor 9
The outlet of the coil 9a is connected to the suction pipe of the low-stage compressor 1a.

On the other hand, a second stage consisting of a single-stage or two-stage compressor
The discharge gas compressed by the former compressor 10 is cooled by the conventional method (water or air) in the cooler 11,
De-super heater 7 is sent. The outlet of the de-superheater 7 is connected to the inlet of the cascade condenser 9, and the outlet of the cascade condenser 9 is connected to the expansion valve 12
Is connected to the inlet of the cooling coil 13a of the cooler 13 for cooling the load. The outlet of the cooling coil 13a is connected to the suction pipe of the compressor 10. The inlet of the de-super heater 7 is connected to the second source compressor 10 via the protective container 14.
Connected to the suction pipe.

In the multi-source refrigeration system constructed as described above,
After cooling the refrigerant gas discharged from the second source compressor 10 by a conventional method, it is sent to the de-super heater 7,
It cools by exchanging heat with the liquefied refrigerant in the condenser 2 on the original side.
The liquid refrigerant on the first source side is gasified by exchanging heat with the discharge gas on the second source side in the de-super heater 7, and is guided to the high-stage suction pipe of the first source compressor 1.

As a result, the amount of heat of the cascade condenser 9 cooled in the low stage of the first source compressor 1 can be reduced, and the size of the first source compressor 1 (reduction of piston displacement) and energy saving can be achieved. Can be planned.

Next, another embodiment shown in FIG. 2 will be described. In this embodiment as well, the discharge gas compressed by the second source compressor 10 is guided to the de-super heater 7 after being cooled by the conventional method. The refrigerant liquefied in the condenser 2 on the first source side is decompressed by the expansion valve 3, guided to the coil 4a of the intercooler 4, and gasified to supercool the low-stage refrigerant (including part of the liquid). The refrigerant is sent to the de-super heater 7 to exchange heat with the discharge gas on the second source side. The evaporated first-side refrigerant is
Guide to the high-stage suction pipe of the first source compressor 1.

Next, another embodiment shown in FIG. 3 will be described. The discharge gas compressed by the second source compressor 10 is guided to the de-super heater 7 after being cooled by a conventional method. The expansion valve 6 decompresses the refrigerant liquefied in the condenser 2 on the first source side,
It is sent to the de-super heater 7 to exchange heat with the discharge gas on the second source side. The evaporated refrigerant (including part of the liquid) is introduced into the coil 4a of the intercooler 4 to exchange heat. First evaporated
The refrigerant on the former side is guided to the high-stage suction pipe of the first former compressor 1.

Next, the heat radiation amount from the second element is set to 10,000
Assuming that 0 Kcal / h, the refrigerant circulation amount of the first source compressor 1 is compared between the conventional method and the method according to the present invention. FIG. 4 shows a Mollier diagram of the first-side refrigerator. In this figure, A indicates a case where a reciprocating type is used for the first source compressor 1,
B shows the case where a screw type is used. In FIG.
The Mollier diagram of the refrigerator of the former side is shown.

First, in the conventional system in which the total amount of heat is cooled by the cascade condenser 9, the low-stage refrigerant circulation amount = 10,000 Kcal / h / 46.53 Kca.
l / Kg = 214.9 Kg / h Supercooling heat amount = 214.9 Kg / h × (112.77-9
8.59) Kcal / Kg = 3,047 Kcal / h Amount of refrigerant evaporated for supercooling = 3047 Kcal / h /
35.68 Kcal / Kg = 85.4 Kg / h Therefore, low stage compression amount = 214.9 Kg / h middle stage compression amount = 214.9 + 85.4 = 300.3 Kg / h On the other hand, in the method according to the present invention, the enthalpy difference of the condensation process Of the 60.095 Kcal / Kg, the cooling amount of the de-super heater 7 is 6 Kcal / Kg, which is 10%, so the heat amount is 10,000.
The breakdown of 0 Kcal / h is: Cascade condenser calorific value = 9000 Kcal / h De-superheater calorific value = 1,000 Kcal / h. Low-stage refrigerant circulation rate = 9000Kcal / h / 46.53Kcal
/Kg=193.4Kg/h Supercooling heat amount = 193.4Kg / h × (112.77-9
8.59) Kcal / Kg = 2742 Kcal / h Amount of refrigerant evaporated for supercooling = 2,742 Kcal / h
/35.68Kcal/Kg = 76.9Kg / h Degassing amount of refrigerant by super heater = 1,000Kcal / h / 35.68Kcal / Kg = 28.0Kg / h Therefore, low stage compression amount = 193.4Kg / h Middle compression amount = 193.4 + 76.9 + 28.0 = 28
8.3 Kg / h As described above, according to the method of the present invention, the power of the first source compressor 1 and the piston displacement can be reduced by about 7% as shown in Table 1.

[0018]

[Table 1]

[0019]

As described above, the multi-source refrigeration system of the present invention uses the expansion valve to expand the liquefied refrigerant in the condenser on the first source side when using the HFC23 as a substitute refrigerant for R13 or R503 in the second source refrigerator. Since the pressure is reduced to the suction pressure of the high-stage compressor and heat is exchanged between the discharge gas on the second source side and the discharge gas cooler, the heat quantity of the cascade condenser can be reduced, and the heat of the first source compressor can be reduced. It is possible to reduce the size and save energy.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a multi-source refrigeration system according to the present invention.

FIG. 2 is a system diagram showing a main part of a multi-source refrigeration system of another embodiment.

FIG. 3 is a system diagram showing a main part of a multi-source refrigeration system of yet another embodiment.

FIG. 4 is a Mollier diagram of the first original refrigerator.

FIG. 5 is a Mollier diagram of the second original refrigerator.

[Explanation of symbols]

 1 1st original compressor 1a Low stage compressor 1b High stage compressor 2 Condenser 3 Expansion valve 4 Intercooler 6 Expansion valve 7 De-super heater 7a Heat exchange coil 8 Expansion valve 9 Cascade condenser 10 2nd element Compressor 12 Expansion valve 13 Cooler 13a Cooling coil 14 Protective container

Claims (1)

[Claims] 1. A multi-source refrigeration system in which a plurality of refrigerators are connected in multiple stages by a cascade condenser forming a condenser, wherein a low-source side compressor is provided between a discharge side of the low-source side compressor and an inlet of the cascade condenser. A discharge gas cooler that pre-cools the discharge gas from the compressor is installed, the high-side compressor is composed of a two-stage compressor consisting of a low-stage compressor and a high-stage compressor, and the refrigerant discharged from this high-stage compressor Is liquefied by a condenser, then decompressed by an expansion valve to the suction pressure of the high-stage compressor, and led to the coil of the discharge gas cooler to exchange heat with the low-side discharge gas.