JPH04369355A - Ammonia refrigerator - Google Patents

Abstract

PURPOSE:To prevent deterioration of the result factor of a vaporizer and to enable execution of unmanned operation by a method wherein a pressure in an oil return passage at a stage after the passage of a refrigerant through an expansion valve is set to a value higher than a pressure in a suction piping connected to the suction side of a refrigerator. CONSTITUTION:Lubricating oil gathering in an oil reservoir 6 of a vaporizer 4 can be returned to the liquid receiver 3 side in a way that a refrigerating cycle is periodically switched and a pressure on the vaporizer 4 side is increased to a value higher than that of the liquid receiver 3 side. When a refrigerator is under refrigerating operation, lubricating oil present in an oil reservoir part 23 of the liquid receiver 3 can be constantly returned to the suction piping 38 side of a freezer 1 through an expansion valve 25 togetherwith a refrigerant. However, since a pressure on the suction piping 38 side on the refrigerator side is set to a value lower than a pressure in an oil return passage 48 running back from the liquid receiver 3, lubricating oil can be returned to the refrigerator through suction pipings 38 and 39. Since a refrigerant containing lubricating oil is expanded and cooled by means of the expansion valve 25, temperature in the suction piping 39 is lowered, the temperature of a refrigerant on the a freezer delivery piping 31 side is also not increased and lubricating oil is prevented from deterioration.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ammonia refrigeration system, and more particularly to an ammonia refrigeration system that returns lubricating oil accumulated in an evaporator/receiver to a refrigerator.

0002

2. Description of the Related Art Conventionally, many refrigeration systems using ammonia refrigerant have been used in fields such as ice making and refrigeration. The main reason for this is that it has a better coefficient of performance than other refrigerants, and because liquid ammonia does not dissolve lubricating oil for refrigerators (compressors), its properties as a refrigerant are stable over a long period of time. Things are being raised. however,
Lubricating oil that does not dissolve in the refrigerant has a higher specific gravity than the refrigerant, and its viscosity increases especially in the low-temperature evaporator. At the same time, it gradually accumulated in the evaporator, deteriorating the performance of the evaporator. For this reason, an oil sump was provided in the evaporator, and the oil had to be periodically drained manually. It was also necessary to periodically replenish lubricating oil to the refrigerator in an amount that was not returned to the refrigerator from the evaporator. That is, it has been considered impossible to operate an ammonia refrigeration system unattended due to the above-mentioned periodic oil draining and replenishing operations.

On the other hand, since fluorocarbon-based refrigerants dissolve lubricating oil, the lubricating oil mixed in the evaporator does not accumulate in the evaporator and returns to the refrigerator, eliminating the need for the above-mentioned periodic work. The refrigerant used in this system has shifted from ammonia refrigerant to fluorocarbon refrigerant in line with the demands of the times for labor saving, and the latter is currently the mainstream.

0004

[Problems to be Solved by the Invention] However, even in a fluorocarbon-based refrigerant, the concentration of dissolved lubricating oil gradually increases, and its properties as a refrigerant deteriorate. Furthermore, efforts should be made to avoid the use of fluorocarbon-based refrigerants, which have become a problem of environmental destruction. In view of the drawbacks of the prior art, the present invention has been developed to enable unmanned operation by periodically and automatically returning lubricating oil accumulated in a liquid receiver functioning as an evaporator and a condenser to a refrigerator (compressor). The purpose is to provide ammonia refrigeration equipment.

[0005]

[Means for Solving the Problems] In order to achieve this technical problem, the present invention provides means for returning oil in the oil reservoir 6 on the evaporator 4 side to the liquid receiver 3 side by appropriately switching the refrigeration cycle. , means for returning the oil in the oil reservoir 23 of the liquid receiver 3 to the suction side 38 of the refrigerator 1 side via the expansion valve 25, and the oil in the oil return path 48 after passing through the expansion valve 25 An ammonia refrigeration system is proposed in which the pressure is set to be higher than the pressure in the suction pipe 38 connected to the refrigerator suction side 39.

[0006]

[Operation] According to this technical means, the lubricating oil accumulated in the oil reservoir 6 of the evaporator 4 is made by periodically switching the refrigeration cycle and making the evaporator 4 side have a higher pressure than the liquid receiver 3 side. can be returned to the liquid receiver 3 side. Next, while the refrigeration system is in refrigeration operation, the lubricating oil in the oil reservoir 23 of the liquid receiver 3 is constantly supplied to the suction pipe 3 of the refrigeration machine 1 through the expansion valve 25 together with the refrigerant.
It is possible to return to the 8th side. However, since the pressure on the suction pipe 38 side of the refrigerator 1 is set lower than the pressure in the oil return path 48 returning from the liquid receiver 3, the lubricating oil flows through the suction pipes 38 and 39. It becomes possible to return to refrigerator 1. Further, since the refrigerant containing lubricating oil is expanded and cooled by the expansion valve 25, the temperature inside the suction pipe 39 decreases, and therefore the temperature of the refrigerant on the refrigerator discharge pipe 31 side does not rise, and the lubricating oil It also prevents deterioration due to high temperatures.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below by way of example with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and relative positions of the components described in this example are not intended to limit the scope of this invention, but are merely illustrative. Just an example.

FIG. 1 is a system diagram of an ammonia refrigeration system according to an embodiment of the present invention. The refrigeration system uses ammonia as a refrigerant. It consists of a liquid container 3, an evaporator 4 piped with a flexible pipe, and a pump 9 that circulates cooling water between the liquid receiver 3 and the cooling tower 8. In addition, 6 is the oil sump of the evaporator 4, 2
3 is an oil reservoir of the liquid receiver 3.

[0009] The structure and operation of a refrigeration system, which has the above structure plus piping, valves, etc., will be explained along the refrigeration cycle.

Ammonia compressed in the refrigerator 1 reaches the oil separator 2 via a discharge side pipe 31. Most of the lubricating oil used in the refrigerator 1 is separated by the oil separator 2 and returned to the refrigerator 1 via the piping 32 and the check valve 10. The ammonia from which the lubricating oil has been separated is transferred to the solenoid valve 11 and the pipe 3.
3 and reaches the liquid receiver 3. In the liquid receiver 3, the circulating water cooled by the cooling tower 8 is circulated through the pipe 50, the liquid receiver 3, the pipe 51, and the cooling tower 8 by a pump 9, and the circulating water is introduced into the liquid receiver 3. The high temperature ammonia is cooled, condensed and liquefied, and accumulates in the liquid receiving part 3. The liquefied ammonia in the liquid receiver 3 is transferred to the pipe 34, the solenoid valve 12,
The liquid ammonia is introduced into the evaporator 4 via the expansion valve 13 and the inlet pipe 35 of the evaporator 4, and the liquid ammonia is vaporized to perform the desired freezing operation. The temperature inside the evaporator 4 is controlled by the control device C.
1, the expansion valve 13 is adjusted based on the temperature of the thermometers 14 and 15.
This is done by adjusting the opening degree. The ammonia evaporated and vaporized in the evaporator 4 is transferred to the outlet side piping 36 of the evaporator 4,
It returns to the refrigerator 1 through the oil reservoir 6 on the evaporator 4 side, the piping 37, the solenoid valve 16, the suction pressure regulator 17, the mixing tank 5, and the suction side piping 39 of the refrigerator 1. Thereafter, the refrigeration cycle is repeated to perform the refrigeration operation in the evaporator 4.

In the defrosting cycle for removing frost in the evaporator 4, high temperature ammonia in the discharge side pipe 31 of the refrigerator 1 is removed by closing the solenoid valve 11 and opening the solenoid valve 20. Oil separator 2, piping 40, solenoid valve 20, piping 41
, 42, the ammonia is directly introduced into the evaporator 4 through the evaporator inlet pipe 35 for defrosting, and the ammonia itself is liquefied. Liquid ammonia in the outlet side piping 36 flows through the oil sump 6, piping 43, check valve 21, and piping 34 on the evaporator 4 side by closing the solenoid valve 16 and opening the solenoid valve 22. Then, it reaches the liquid receiver 3. As described above, the liquid receiver 3 functions as a heat exchanger with the circulating water, so the liquid ammonia is heated and vaporized by the circulating water, and the liquid ammonia is heated and vaporized by the circulating water. Via the pressure regulator 17, piping 38, mixing tank 5, and suction side piping 39 of the refrigerator 1,
Return to refrigerator 1. Thereafter, the defrosting cycle described above is repeated, and the defrosting operation in the evaporator 4 is repeated.

The switching between the refrigeration cycle and the defrosting cycle is performed by switching the solenoid valves 11, 12, 16 as appropriate depending on the temperature difference between the thermometers 14 and 15 controlled by the control device C1 and/or the clock possessed by the control device C1. , 20, 22 and 24 are opened and closed.

Looking back at the defrosting cycle, the evaporator 4
The liquefied ammonia is introduced into the receiver 3 via the oil sump 6 on the evaporator 4 side on its way back from the evaporator 4 to the refrigerator 1. The lubricating oil accumulated in the liquid receiver 6 also reaches the liquid receiver 3, where the lubricating oil is separated from ammonia and accumulated in the oil reservoir 23 on the liquid receiver 3 side.

The lubricating oil accumulated in the oil reservoir 23 on the side of the liquid receiver 3 is transferred to the pipe 4 along with the ammonia in the liquid receiver 3.
7. Returns to the refrigerator 1 via the electromagnetic valve 24, the expansion valve 25, the pipe 48, the mixing tank 5, and the suction side pipe 39 on the refrigerator 1 side. Although the oil return flow is constantly flowing, its flow rate is controlled by the control device C2, and the flow rate is controlled by the control device C2.
The expansion valve 25 is controlled to be opened more when the temperature in the discharge side piping 31 becomes high, and conversely to close when the temperature is low, based on a temperature signal from a thermometer 26 installed in the discharge side piping 31. do. Therefore, the temperature of ammonia in the discharge side pipe 31 of the refrigerator 1 is within a predetermined range, and is set so that the lubricating oil does not decompose or change in quality due to the high temperature.

The oil return flow introduced into the mixing tank 5 via the pipe 48 is combined with ammonia returning from the evaporator 4 via the pipe 38 in the mixing tank 5. Here, in order to guarantee the flow of the oil return, the suction pressure regulator 17 is set such that the pressure inside the pipe 48 is always higher than the pressure inside the pipe 38.
may be arranged in the piping 38.

If the refrigeration cycle/defrosting cycle is organized including the oil return flow, during the refrigeration cycle, the solenoid valves 11, 12, 16, and 24 are open, and the solenoid valves 20, 22 are open. Since the setting is closed, the ammonia compressed by the refrigerator 1 is transferred to the oil separator 2, liquid receiver 3, and expansion valve 13.
, reaches the evaporator 4, returns to the refrigerator 1 via the oil sump 6 on the evaporator 4 side, the mixing tank 5, and the oil return flow also flows from the oil sump 23 on the receiver 3 side to the expansion valve 25, It returns to the refrigerator 1 via the mixing tank 5.

Furthermore, during the defrosting cycle, the solenoid valves 20, 22, and 24 are set to open, and the solenoid valves 11, 12, and 16 are set to close, so that the ammonia compressed by the refrigerator 1 is separated from the oil. The oil flow directly flows from the container 2 to the evaporator 4, passes through the oil reservoir 6 on the evaporator 4 side, the liquid receiver 3, and the mixing tank 5, and returns to the refrigerator 1, and the oil return flow is also carried out in the same way as in the above-mentioned refrigeration cycle. The oil returns from the oil reservoir 23 on the liquid container 3 side to the refrigerator 1 via the expansion valve 25 and the mixing tank 5.

Therefore, when the lubricating oil of the refrigerator 1 reaches the oil separator 2 through the discharge side piping 31 together with ammonia, most of it is separated and returns to the refrigerator through the piping 32 and the check valve 10. Furthermore, the lubricating oil not recovered by the oil separator 2 is
The lubricating oil is accumulated in the oil sump 23 on the liquid receiver 3 side and the oil sump 6 on the evaporator 4 side, and the lubricating oil in the former oil sump 23 is constantly stored, and the lubricating oil in the latter oil sump 6 is stored in the former oil sump 23 during the defrosting cycle. After that, it is returned to the refrigerator 1. Note that the lubricating oil returned to the piston surface in the refrigerator 1 is returned to a portion other than the refrigerator 1 that requires lubricating oil, such as a shaft seal, via an oil separator 2.

[0019]

[Effects of the Invention] As described above, according to the present invention, lubricating oil does not deposit or accumulate in the evaporator and deteriorate the coefficient of performance of the evaporator, and furthermore, the refrigeration cycle and defrosting cycle are automatically activated. By appropriately switching the lubricating oil to the refrigerating machine, unattended operation of the ammonia refrigerating equipment becomes possible. Further, according to the present invention, it is possible to control the temperature on the discharge side of the refrigerator so as not to rise above a predetermined temperature using the oil return function, so that decomposition and deterioration of the lubricating oil can be prevented. Furthermore, according to the present invention, since ammonia can be operated while retaining its original property of not dissolving lubricating oil, for example, as seen in fluorocarbon-based refrigerants, when the operation is continued for a long period of time, ammonia may remain in the refrigerant. It gradually dissolves lubricating oil and its concentration increases, without degrading its properties as a refrigerant. Furthermore, since no fluorocarbon refrigerant is used, it is possible to provide a refrigeration system that is friendly to the global environment. It has various effects such as

[Brief explanation of drawings]

[Fig. 1] System diagram of an ammonia refrigeration apparatus according to the present invention

[Explanation of symbols]

1 Refrigerator 3 Liquid receiver 4 Evaporator 6 Oil sump on the evaporator side 23 Oil reservoir part of liquid receiver 25 Expansion valve 38 Refrigerator suction piping 39 Refrigerator suction side 48 Oil return path

Claims (1)

[Claims] Claim 1: A refrigerator that compresses ammonia refrigerant;
In an ammonia refrigeration system comprising an evaporator and a liquid receiver functioning as a condenser, there is provided a means for returning oil in an oil sump on the evaporator side to the liquid receiver side by appropriately switching a refrigeration cycle; means for returning oil in the oil reservoir to the suction side of the refrigerator via an expansion valve, and the pressure in the oil return path after passing through the expansion valve is transferred to the suction pipe connected to the suction side of the refrigerator. An ammonia refrigeration device characterized in that the pressure is set to be greater than the pressure of