JPH01262387A - Parallel compression type refrigerator - Google Patents

Abstract

PURPOSE:To improve the extent of capacity transfer performance by controlling each compressor of large and small capacities for starting and stopping according to refrigerant pressure at the low pressure side, while controlling the output frequency of an inverter connected to a medium capacity compressor, in a device parallelly connecting three compressors difference capacity each. CONSTITUTION:In a device which secures required refrigerating capacity to refrigeration load of a cooling system 2 with showcases 2a-2c by a refrigerator A inclusive of three compressors 1b-1d different in large, medium and small capacities selected at almost 1:1.5:2 in each rated capacity ratio, there is provided with a pressure detecting element 4 which detects the refrigerating capacity at the low pressure side. In addition, an inverter 1i continuously controllable up to 50-125% of the rated capacity is connected to the medium capacity compressor 1c. Then, output frequency of the inverter 1i is controlled by a control part 3 according to output of the pressure detector 4, while these large and small capacity compressors 1b, 1d are controlled for their on-off operation, and thereby refrigerant pressure at the low pressure is converged on the specified setting value.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a refrigeration system used in a group of multiple freezer/refrigerated showcases installed at the same place, such as a supermarket, that is, a refrigeration system with large load fluctuations. The present invention relates to a parallel compression refrigeration system that can always operate in an optimal state.

[Conventional technology]

Conventionally, there was a type of device shown in figure grI3. This l! In Figure 3, (A) is a parallel compression refrigeration system, (2) is a multiple showcase (2m), (
2b).

This is a cooling device configured with the combination of (2c). fil
is a condensing device, and a water-cooled condenser (1a) is a liquid receiver 4 connected downstream of an air-cooled condenser (not shown).
A large capacity compressor (1b), a medium capacity compressor (IC), and a small capacity compressor (1d) are placed on top of the container, with the rated capacity ratio of the compressors being selected as i1 to 1.5 to 2. ) are installed in parallel, and each compressor (1b), (IC) and (
The refrigerant discharge pipe (IC) and suction pipe (1f) of 1d) are connected in parallel.

In addition, (ig) is a pressure equalizing oil pipe that communicates the crank chambers of each compressor (1b) and (IC) with each other, and (1h) is a pipe that communicates the crank chambers of each compressor (1b) and (1d) with each other. This is a pressure equalizing oil pipe. (3) is the above compressor (lb), (
The compressor (lb) according to the output signal of the pressure detection unit (4) that detects the refrigerant pressure on the low pressure side of
, (lc) and (1d).

Also,! As shown in Figure 4, the normal pressure region is determined by three factors: capacity up pressure value, capacity down pressure value, and low pressure/low pressure value. above), the parallel compression refrigeration system (A) has a capacity down pressure value or higher where neither a capacity down signal nor a capacity up signal is output, and the capacity up pressure value has not yet been reached (c), and a parallel compression refrigeration system a capacity down pressure value unexplored area (b) that sends a capacity down signal to the device (A);
It can be divided into four areas (A) where the pressure is below the low pressure cut value that issues a stop signal to the parallel compression refrigeration system (A).

Next, the operation will be explained. For example, cooling device (2)
When the required power to obtain the required refrigerating capacity for the refrigerating load is 22.5 IP, the rated capacity of the compressor (1b) is 10 IP, and the rated capacity of the compressor (1 c) is 7.5 W.
The rated capacity of 1 compressor (1d) is selected as 5)P.

On the other hand, multiple showcases (2m) * (2b), (
In the cooling device (2) consisting of 2c), the refrigeration load varies greatly from 0 to 100% depending on the usage status of each showcase.

Here 1. When the refrigeration load decreases, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases, and the pressure detection part (4
) also decreases the level of the pressure detection signal output from the controller (3).

The control unit (3) has a comparison circuit that compares the pressure detection signal with a reference value (capacity up pressure value or capacity down pressure value), so if the pressure detection signal is lower than the capacity down pressure value, In other words, in the case of region (B), the control unit (31) controls the capacity of the parallel compression refrigeration system (A) to decrease, thereby lowering the cooling capacity. The refrigerant pressure on the low pressure side of the cycle increases and converges to the region f→, and the operation becomes stable.

Additionally, when the cooling load is high, the refrigerant pressure on the low pressure side of the refrigeration cycle increases, and the level of the pressure detection signal output from the pressure detection section (4) to the control section (3) increases accordingly. . As a result, if the pressure detection signal is higher than the capacity up pressure value, i.e. in the area), the control unit (
3) is controlled to increase the capacity of the parallel compression type refrigeration system (A), thereby increasing the cooling capacity. When the cooling capacity increases in this way, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases and converges to region (c), and the operation becomes stable.

Note that if the refrigerant pressure on the low pressure side of the refrigeration cycle is below the low pressure cut value, that is, in region (A), the compressor (lb
), (lc), and (ld) are designed to stop immediately.

Therefore, for the above refrigeration load fluctuation, the refrigeration load is 2
At partial loads below fl, a compressor with a rated capacity of 5H' (1
d) is operated independently. In addition, the refrigeration load is 22 to 3
In the range of 3 inches, only the crusher (1c) with a rated capacity of 7.5B' is operated independently. When the refrigerating load is in the range of 33 to 44 k, only the compressor (1b) with a rated capacity of 101F is operated independently.

Furthermore, if the refrigeration load is in the range of 44 to 55 inches, the compressor (1
c) and (1d) are operated in parallel at the same time. Refrigeration load is 5
In the range of 5 to 66%, compressors (1b) and (1d) are operated in parallel at the same time. When the refrigerating load is in the range of 66 to 77 inches, the compressors (1b) and (1c) are operated in parallel at the same time.

When the refrigeration load is in the range of 77 to 100 inches, the compressors (1b), (lc), and (1d) are operated in parallel at the same time. The transition of this capacity control operation is shown in Figure 5.

In other words, as shown in Figure 5, by selectively operating and stopping small, medium and large compressors, the rated capacity ratio of the compressors is selected to be 1:1:1:5:2. .2
Capacity control operation can be performed in eight stages: 2.33.44.55.66, 77, and 100%.

[Problem to be solved by the invention]

Since the conventional parallel compression type refrigeration system # is configured as described above, 0.22.33.44.55.66, 77°1
Capacity control operation can only be performed in 8 stages of 00%, and the refrigeration load is between 0 and 22%, between 22 and 3.3% (7), and between 33 and 4.
Between 4%, between 44 and 55 inches, between 55 and 66 inches, 66 inches
In the partial load range between 77 inches and 77 inches to 100 inches, the compressor is over-operated, resulting in a significant drop in operating efficiency.

This invention was made in order to eliminate the above-mentioned conventional drawbacks, and it is possible to perform optimal operation that follows the refrigeration load at a variable stage of 17 to 108% of the refrigeration load, and to improve the operating efficiency for partial loads. The purpose of this invention is to provide a type refrigeration system.

[Means to solve the problem]

In this invention, the rated capacity ratio is 1:1.5:2.
A condensing device having a large capacity, medium capacity and small capacity compressor selected as
There is also a pressure detection section that detects the refrigerant pressure on the low-pressure side of the refrigeration system, which is connected to the condensation device and includes a cooling device, and generates a pressure detection signal, and a pressure detection section that detects the refrigerant pressure on the low pressure side of the refrigeration system, which is connected to the condensation device and generates a pressure detection signal. An inverter that continuously controls up to 50 to 125% of the rated capacity, and controls the output frequency of the inverter according to the pressure detection signal, and turns on and off the operation of the large capacity and small capacity compressors.
and a control unit that converges the refrigerant pressure on the low pressure side to a predetermined set value by controlling the refrigerant pressure on the low pressure side, and when the refrigeration load of the cooling device is 17 to 39% based on the output of the control unit, the inverter controls the medium capacity. When only the compressor is driven and the refrigeration load is 39 to 61%, the small capacity compressor is driven by the commercial AC power supply, the medium capacity compressor is driven by the inverter and operated in parallel, and the refrigeration load is In units 61 to 83, the large-capacity compressor is driven by a commercial AC power source, and the medium-capacity compressor is driven by the inverter to operate in parallel. Further, when the refrigeration load is 83 to 108 inches, the above objective is achieved by driving the small capacity and large capacity compressors with the commercial alternating current source, and driving the medium capacity 1 compressor with the inverter to operate them in parallel. It is something.

[Effect]

The refrigeration system in this invention is based on the output of the control section,
Through the inverter, only the medium-capacity compressor is continuously controlled up to its rated capacity of 50 to 125 inches, and the large-capacity and small-capacity compressors are turned on and off.
1J, and the refrigeration load of the cooling device is 17
When the refrigeration load is between 39% and 39%, only the medium capacity compressor is driven by the inverter, and when the refrigeration load is between 39 and 61%, the small capacity compressor is driven by the commercial AC power supply and the medium capacity compressor is driven by the inverter. Drive and parallel operation, refrigeration load is 6
At 1% to 83%, the large capacity compressor is driven by the commercial AC x source, and the medium capacity compressor is driven by the inverter for parallel operation. Furthermore, when the refrigeration load is 83 to 108 inches, the small capacity and large capacity compressors are driven by the commercial AC power supply, and the medium capacity compressor is driven by the inverter and operated in parallel. It is possible to perform optimal operation that follows the refrigeration load in the range of fluctuations in temperature, making it extremely economical and advantageous for energy conservation.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a parallel compression type refrigeration system according to the present invention will be described with reference to the drawings. Figure I1 is a refrigerant circuit diagram of one embodiment, and this parallel compression type refrigeration system t(A) has a plurality of showcases (2l ) to (2C)
) are connected.

On the other hand, the parallel compression type refrigeration system (A) is different from the one shown in Fig. 83, and the medium capacity compressor (I C') has a
An inverter (10 is connected) that can continuously control up to 25 channels.The other components are the same as in Figure 3.

Next, the operation of the parallel compression type refrigeration system of the present invention configured as described above will be explained.

For example, if the required power to obtain the required refrigerating capacity for the refrigerating load of the cooling device (2) is 22.5P, the rated capacity of the compressor (1b) is 10P, and the compressor (lc)
The rated capacity of the compressor (1d) is 7-5Pl The rated capacity of the compressor (1d) is 5
) P is selected, and the capacity of the compressor (IC) is selected as the inverter (
II) can be continuously varied from 3.75 to 9.375) P. The control unit (3) stops all the compressors (lb), (lc), and (ld) depending on the load capacity, and operates only the compressor (IC) independently with the inverter (11).
Compressor (IC) with inverter (II)
is operated on commercial AC power.

The compressor (1c) is connected to the compressor (1b) by the inverter (II).
Is the compressor (LC) operated on commercial AC power? The inverter (11) controls the compressors Qb) and (ld) so that their capacities increase in the order of operation with commercial AC power. Cooling system(
Regarding the refrigeration load fluctuation in 2), when the refrigeration load is at partial load of 39% or less, only the compressor (IC) with a rated capacity of 7.5W is operated independently by the inverter (II), and the inverter (IC) is operated independently to follow the refrigeration load. 11) Compressor (IC)
The capacity varies from 3.75 to 8.751P-1.

Nine, if the refrigeration load reaches 39-61%, the compressor (Ic)
is operated by an inverter (10) and a compressor ((1d)
are simultaneously operated in parallel by a commercial AC power source.

At this time, the inverter (11) is installed to follow the refrigeration load.
The capacity of the compressor (1c) is 3.75 to 8.75)
The rated capacity of the compressor (1d) i 5 ) P
is added, so the capacity of the entire parallel compression type refrigeration system varies from 8.75 to 13.75W. Refrigeration load is 61
When it reaches ~83%, the compressor (1c) is replaced by an inverter (11)
The compressor (lb) is simultaneously operated in parallel by a commercial AC power source. At this time, the capacity of the compressor (IC) changes from 3.75 to 8.75 W by the inverter (11) to follow the refrigeration load, and the rated capacity 10) P of the compressor (1b) is added, so parallel compression The capacity of the entire type refrigeration system varies from 13.75 to 18.75)P. When the refrigeration load reaches 83-108%, the compressor (IC)
is operated by an inverter (11), and a compressor (lb)
, (ld) are simultaneously operated in parallel by a commercial AC power source.

At this time, the inverter (11
), the capacity of the compressor (1c) is 3.75 to 9.375
Since the rated capacity of the compressor (1b) (10H) and the rated capacity of the compressor (1d) of 5F are added, the parallel compression refrigeration system as a whole has a capacity of 18.75 to 24.37.
It fluctuates up to 5fF.

The transition of this capacity control operation is shown in Figure 2.

In other words, as shown in Figure 2, large, medium and small compressors (lb) + (lc), (ld) whose rated capacity ratios are selected to be 1:1:1:2: drive selectively,
A medium capacity compressor (
By continuously controlling the capacity of 1c) from 50 to 125%, continuous capacity control operation can be performed from 0 and 17 to 108 inches.

As a result, the parallel compression type refrigeration system is able to perform optimal operation by following the refrigeration load in a fluctuation range of 17 to 108% of the refrigeration load, and is more advantageous in energy saving than the conventional system shown in FIG. Moreover, among the three compressors, the medium capacity compressor (1c
) Capacity ft 50 to 125% can be controlled with a single inverter, making the above capacity control possible and very economical.

Note that if the compressor is operated at 17% or less of the capacity of the parallel compression refrigeration system (A), the amount of refrigerant circulating will decrease, and the amount of oil accumulated in the showcase will increase, causing damage to the sliding parts of the compressor. There is a risk of seizure due to insufficient supply of lubricating oil, etc., and 17%
It is dangerous to perform capacity control operation following the refrigeration load in the following conditions.

〔Effect of the invention〕

As described above, according to this parallel compression type refrigeration system, three compressors, small, medium, and small, with a rated capacity ratio of 1 to 1.5 to 2, are connected in parallel. The refrigeration system includes a pressure detection section that detects the refrigerant pressure on the low-pressure side of the refrigeration system, and a pressure detection signal from the pressure detection section that is input to control ON and OFF operation of the large capacity and small capacity compressors, as well as an inverter. By controlling the output frequency of It is possible to perform optimal operation according to the following conditions, is very economical, and is advantageous for energy saving.

[Brief explanation of the drawing]

Fig. 1 is a refrigerant circuit diagram of a parallel compression type refrigeration system according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of capacity control operation of the parallel pressure line type refrigeration system of Fig. 1, and Fig. 3 is a diagram of a conventional parallel compression type refrigeration system. The refrigerant circuit diagram of a compression refrigeration system, gS4 diagram, shows the refrigerant pressure area on the low pressure side [
FIG. 5 is an explanatory diagram of capacity control operation of the parallel compression type refrigeration system of FIG. 3. In these figures, (A) is a parallel compression refrigeration system, (
II is a condensing device, (1a) is a condenser, (lb), (l
c) and (ld) are large, medium, and small capacity compressors, respectively;
(11) is an inverter, (2) is a cooling device, (3) is a control unit, and (41 is a pressure detection unit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A condensing device having a large capacity, medium capacity and small capacity compressor with a rated capacity ratio of approximately 1:1.5:2, and a condenser connected to the compressor, and this condensing device A refrigeration system consisting of a cooling system connected to A variable frequency inverter that continuously controls from 50 to 125% of the rated capacity, and controls the output frequency of the inverter according to the pressure detection signal, and turns on and off the operation of the large capacity and small capacity compressors.
A control unit that converges the refrigerant pressure on the low pressure side to a predetermined set value by F control, and based on the output of the control unit, when the refrigeration load of the cooling device is 39% or less, the inverter controls the medium capacity. When only the compressor is driven and the refrigeration load is 39 to 61%, the small-capacity compressor is driven by the commercial AC power supply, and the medium-capacity compressor is driven by the inverter and operated in parallel, and the refrigeration load is 61%. At ~83%, the large-capacity compressor is driven by the commercial AC power supply, and the medium-capacity compressor is driven by the inverter for parallel operation, and when the refrigeration load is 83-108%, the small-capacity and large-capacity compressors are operated in parallel. A parallel compression type refrigeration system characterized in that a compressor is driven by a commercial AC power source, and a medium capacity compressor is driven by the above-mentioned inverter for parallel operation.