JPH02192556A - Parallel compression refrigerating plant - Google Patents

Abstract

PURPOSE:To properly maintain the oil levels of compressors in either case of parallel operation or individual operation of arbitrary compressors by making pressure drop of a suction branch pipe of a branch point of the suction pipe of a refrigerating cycle to an inlet port of each compressor (pressure drop of suction branch pipe of a first compressor) >= (pressure drop of suction branch pipe of a second compressor). CONSTITUTION:A check valve provided at a pressure and oil equalizer 3 communicating with compression element chambers 1d, 2d of both compressors 1, 2 and blocking a gas flow of the compression element chamber 1d of the first compressor 1 to the compression element chamber 2d of the second compressor 2 is provided. A suction branch pipe 6 of the first compressor 1 connecting the upper part of a suction pipe 5 of a refrigerating cycle connected to an evaporator and a motor chamber 1c of the first compressor 1 and a suction branch pipe 7 of the second compressor 2 connecting the lower part of the suction pipe 5 and a motor chamber 2c of the second compressor 2 are provided, the first suction branch pipe 6 has smaller diameter than the second suction branch pipe 7 and is made longer piping. A common discharge pipe 8 of both the compressors 1, 2 is connected to the evaporator through a condenser and an expansion valve. In addition, an orifice 9 is incorporated among the pressure and oil equalizer 3,the first compressor 1 and the second compressor 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to the oil level of the compressor, whether the compressors connected in parallel are operating in parallel or any compressor is operating independently. This invention relates to a parallel compression type refrigeration system that maintains a proper temperature.

[Conventional technology]

Figure 2 shows a conventional parallel compression refrigeration system.
Ill, 121 is the first and second semi-hermetic compressor (la
), (2a) is the crankcase of this compressor full, +21, which includes a motor chamber (lc), (2c) and a compression element chamber (td),
(2d) Sections are formed as follows. (Is)
, (2e), (If), and (2f) are motors 131 (lc), (2c), and compression element chamber (td), respectively.
), (2d) are the motor and compression element housed in. (Ig), (2g) are both elements (te), (2
e), (R), and (2f).
h) and (2h) are pressure equalizing differential pressure valves installed at the top of the bulkheads rib) and (2b).
lc), (2c) pressure is in the compression element chamber (ld),
It closes when the pressure becomes lower than the pressure in (2d). (li).

(21) is an oil equalizing check valve installed at the bottom of the partition walls (lb) and (2b), and is used to supply oil from the motor chamber (lc), (2c) and the oil sump (1) and (2j) at the bottom to the pressure chamber (a). ld), (2d)
This allows oil to flow only into the oil sump (tk) and (sA) at the bottom.

(3) is the compression element chamber (1d) of the same compressor 111.12)
, (2d) are pressure equalizing oil pipes communicating with each other, (51 is an evaporator (
(not shown) fζ connected refrigeration cycle suction pipe, (6
) is the suction branch pipe of the first compressor 111 that connects the upper part of this suction pipe +51 and the motor chamber (1c) of the first compressor IFI, and (7) is the suction branch pipe that connects the upper part of this suction pipe +51 and the motor chamber (1c) of the first compressor IFI. Compressor (
2], the second compressor i2 is connected to the motor room (2e) of
In the first suction branch pipe, the first suction branch pipe (6) has a smaller diameter than the second suction branch pipe (7), and has a longer piping length. (8) is the same compressor i11. +21 common discharge pipe connected to an evaporator (not shown) via a condenser and an expansion valve (not shown) [Problem to be solved by the invention] By two conventional compressors In the parallel compression type refrigeration system 2, pressure equalizing oil piping is provided between both compressors, and these pipings are operated in a state of communication during operation, regardless of parallel operation or individual operation. As a result, in a semi-chamber closed type refrigerator that is divided into a suction chamber element and a compression chamber element, during independent operation, the suction pipe of the stopped compressor, the motor chamber, the compression element chamber, and the pressure equalization pipe are passed through the Due to the pressure applied to the compression element chamber, the oil equalizing check valve of the operating compressor closes, and the oil that has returned to the suction chamber does not return to the compression element chamber, thus maintaining the oil level in the compression chamber at a normal level. Unfortunately, there was a risk of seizure due to insufficient supply of lubricating oil to the sliding parts of the compressor, a decrease in refrigeration capacity due to excessive oil in the compressor during operation, and damage to valve parts due to oil compression. . In addition, during independent operation, the oil that returns to the suction chamber and accumulates is scraped up by the motor and discharged.In order to prevent the oil from becoming excessively high, an oil separator is installed at the discharge end of the compressor, and the oil that accumulates in the suction chamber is removed from the discharge gas. There is also a method of separating the oil from the oil and sending it back to the compressor, but the high temperature oil returns to the crankcase and raises the oil temperature, and when restarting after a long stop, the oil is returned to the compressor at a low temperature. There was a risk that the condensed liquid refrigerant would be returned to the compressor, causing oil to bubble and causing poor lubrication. In addition, a small pressure difference occurs in the compression element chamber of the compressor, which tends to cause the oil level in the compressor to become unbalanced during operation, making it difficult to confirm the oil level position from the oil window during maintenance and maintenance work. It became difficult to do, and the second
If a compressor causes foaming, more oil than necessary is the first problem.
There were problems such as leakage into the second compressor and lowering the oil level in the second compressor.

This invention was made in order to solve the above-mentioned problems, and the present invention has been made to solve the above-mentioned problems. The objective is to obtain a parallel compression type refrigeration system that can maintain an appropriate oil level.

[Means to solve the problem]

The parallel compression type refrigeration system according to the present invention includes means for separating refrigerant gas and oil in the middle of the suction pipe, and a part of the refrigerant gas after one separation is sucked into the first compressor, and the remaining refrigerant and oil are removed. At the same time, the oil reservoirs of the same compressor are communicated with each other through a pressure equalizing oil pipe, and gas flows from the first compressor to the second compressor side through the pressure equalizing oil pipe. A check valve is provided to block the flow of the compressor, and an orifice is provided at the connection port of the pressure equalizing oil pipe of the first and second compressors, so that the compressed air flows from the branch point of the suction pipe of the refrigeration cycle to the respective compressor. The pressure loss in the suction branch pipe to the suction port of the compressor is set to (pressure loss in the suction branch pipe of the first compressor)≧(pressure loss in the suction branch pipe of the second compressor).

[Effect]

The pressure equalizing oil piping according to the second aspect of the present invention is connected via an orifice and a check valve to block gas backflow and provide resistance with an orifice to prevent oil from flowing in more than necessary.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In Figure 2, Ill, +21 are the first and second semi-hermetic compressors, (la), (2a) are the compressors Ill, 121 (D crankcase, which includes the partition wall (1b), (2b) causes motor iii (l
c), (2c), compression element chambers (1d), (2d). (le), (2e),
(tf).

(2f) are a motor chamber (lc), (2c) and a compression element chamber (ld), respectively.

(2d) The motor and compression element housed in (2d).

(Ig>, (2g) is both elements (Is), (2e),
(If), the crankshaft connecting (2f), (
lh), (2h) is the partition wall (1b), (21))
The pressure equalizing differential pressure valve installed at the top of the motor chamber (LC) and (2C) equalizes the pressure in the compression element chamber (LD) at the time of startup.
).

It closes when the pressure becomes significantly lower than the pressure in (2d).

(xi) and (2i) are oil equalizing check valves installed at the bottom of the partition walls (tb) and (2b);
c) Bottom oil sump (li).

(21) to compression element chamber (ld), (2d) bottom oil sump (1k).

This allows oil to flow only into (2k).

(3) is the compression element chamber (xd) of both positive compressors 111 and 121
, (2d) is installed in this pressure equalizing pipe (3), and the compression element i (Id) of the first compressor Ill is connected to the second compressor [2]. compression element chamber (
2d). (5) is a suction pipe of the refrigeration cycle connected to the evaporator (not shown), and (6) is the upper part of this suction pipe (5) and the first compressor fi.
The first compressor Il+ is connected to the + motor chamber (1c).
(7) is the suction branch pipe of the second compressor +2) that connects the lower part of the suction pipe +51 and the motor chamber (2c) of the second compressor 12); The pipe (6) has a smaller diameter than the second suction branch pipe (1) and has a longer piping length. (8) is a bidirectional reduction machine +1).

The common discharge pipe (2) is connected to an evaporator (not shown) via a condenser and an expansion valve (not shown).

Further, (9) is an orifice installed between the pressure equalizing oil pipe of (3) above and the first compressor and the second compressor (21).

Next, the operation will be explained. Both positive reduction machine Ill, 12)
When the is in operation, 1 Normally, 0.54 of the refrigerant circulation amount
The oil contained in the refrigerant cycle returns to the compressor I11 (2) side along with the evaporated refrigerant gas in the suction pipe (51). The suction branch pipe (υ) of the compressor (2) flows into the second compressor 1
2) through the motor chamber (2c) oil equalizing check valve (21) and the compression element! (2d). First suction branch pipe +
6) is thinner and longer than the second suction branch pipe (7), so the pressure loss of the refrigerant through the window in (7) is the first suction branch v! +6) 10,000 becomes larger. Therefore, each motor chamber (lc), (2c) and each compression element It
The relationship between the pressures in (ld) and (2d) is that the pressure in the motor chamber rlc) of the first lEa machine ≦ the compression element chamber of the first compressor (
ld) pressure in the compression element chamber (2d) of the second compressor ≦ the pressure in the motor chamber (2C) of the second E51 machine (21, and the oil is in the second 0] compressor 12) Element room (2d)
1 through the pressure equalizing oil pipe (3) S and the check valve (4).
is supplied to the compression element chamber (1d) of the compressor Ill and is properly lubricated +J! You can perform your abilities.

Next, when only the first compressor Ill is operated, the refrigerant gas flows from the suction pipe [51] into the motor chamber (+c) through the suction branch pipe (6) of the first compressor Ill. During this time, the pressure decreases by about 300 mmAq due to the pressure loss f in the piping.

In addition, the pressure in the compression element chamber (ld) is also controlled by the equalization differential pressure valve (1h).
It decreases due to the action of On the other hand, oil flows from the suction pipe [51] to the second
Suction branch pipe (7) of compressor 12), motor room (2c)
, the compression element via the oil equalizing check valve (21)? It flows into (2d).

@2 compressor (2) is not operating, so the suction branch pipe (
7) The pressure loss is extremely small. Therefore, the pressure p+d in the compression element chamber (1d) of the first pressure a machine 11) and the pressure pgd in the compression element chamber (2d) of @2 compressor +2) are P+d<
1) Id, the second compressor + 21 compression element chamber (2
Due to the pressure difference in part of the oil accumulated in d), the compressor @l (1
) is supplied to the compression element chamber (1d), allowing normal operation to continue.

Next, when only the second pressure a m 12) is operated, the refrigerant gas and oil flow into the motor room (2c) through the suction branch pipe (7) of the suction pipe (from 51 to the second compressor + 2). do. During this time, the pressure of motor i1 (2c) of brown 2 compressor 12) decreases by about 200 mmAQ due to pressure loss in the piping.

- If there is no check valve (4) in the pressure equalization pipe (3), the first
The motor ′@(+c) of the compressor 113, the oil equalizing check valve (l
i) Via the compression element chamber (ld) and the oil equalizing pipe (3),
Compression element chamber of the second compressor (2) in operation @ (2d)
Gas flows through the second compressor 12) and increases the pressure.
The oil equalizing check valve (21) is closed, and the motor room (2
The oil returned to c) is compressed into element 1! (2d), and there was a possibility that lubrication failure would occur due to lack of oil in a short period of time, but in this invention, toommA
Since a check valve (4) that operates at qa & is provided in the oil equalizing pipe (3), gas is prevented from flowing from the first compressor to the second compressor 121, and the compression element chamber (2d) The pressure of the motor N (2c) is maintained at approximately the same level as that of the motor N (2c) by the action of the equalizing pressure differential valve (2h).

Therefore, the oil returned to the motor chamber (2c) is compressed by the compression element i1 (
2d).

Also, both compressors I11. When +21 is in operation.

When the first compressor 11) causes foaming.

More oil than necessary had leaked into the second compressor (2), but the oil was put in resistance by the oriice (9) installed at the oil equalizing pipe installation port of both compressors (6) and (21).
This prevents more oil from flowing into the second compressor +2) than necessary.

Therefore, the oil level can always be maintained at a normal level and stable operation can be performed. According to this system, the first compressor Il
l, full operation of the second compressor +2) and any compressor/1
1. Even during partial operation at +21, the oil level can always be maintained at a normal position. Therefore, the first compressor Ill and the second
If the compressors 12+ are compressors with different capacities, for example, the first compressor 111 is 5.5 kW and the second compressor (2) is 10.81 cw, then only the first compressor Il+ 3
34 runs, 674 runs with second compressor (2), both compressors/13. +2) and 1004, making it possible to control the capacity in three stages in total, and when used as a refrigerator for cooling open showcases in food stores, etc., where the load fluctuates frequently, the capacity of the refrigerator can be adjusted in response to load fluctuations. control, it is possible to always operate at an evaporation temperature close to the design conditions, and energy usage efficiency is greatly improved.

〔Effect of the invention〕

As described above, according to the present invention, the oil in the refrigeration cycle is actively returned to the 10,000 compressors while full operation is performed by one compressor, and partial operation is performed by either compressor under all conditions. (3) It is possible to maintain an appropriate oil level in both compressors, and it is possible to prevent seizure of sliding parts, decrease in refrigeration capacity due to excessive oil flow, and damage to valve parts as in the past.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a parallel compression type refrigeration system showing one embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional parallel compression type refrigeration system. 8 in the figure, 111.121 are the first and second compressors. (lc), (2c) are motor chambers, (Ld), (2d
) is a compression element chamber, (lh), (2h) are pressure equalizing differential pressure valves, (li), (2i) are oil equalizing check valves, (3j is a pressure equalizing oil pipe, (4) is a check valve, (6), (7) is a suction branch pipe, and (9) is an orifice. (2) In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A pressure equalizing differential pressure valve and an oil equalizing check valve that allows oil to flow only from the motor chamber side to the compression element chamber side are installed at predetermined positions on the partition wall that divides the inside of the crankcase into the motor chamber side and the compression element chamber side. A first and a second compressor having a first and second compressors are connected in parallel with each other by piping, and a means for separating refrigerant gas and oil is provided in the middle of the suction piping, and a part of the separated refrigerant gas is sucked into the first compressor. At the same time, the remaining refrigerant and oil are sucked into the second compressor, and the oil reservoirs of the two compressors are communicated with each other through a pressure-equalizing oil pipe. A check valve is provided to block the flow of gas to the second compressor side, and an orifice is provided at the pressure equalization oil pipe connection port of the first compressor and the second compressor, respectively. The pressure loss in the suction branch pipe from the branch point of the suction pipe to the suction port of each of the compressors is calculated as follows: (Pressure drop in the suction branch pipe of the first compressor) ≧ (Pressure drop in the suction branch pipe of the second compressor) )
A parallel compression type refrigeration system characterized by: