JP3448793B2 - Refrigeration equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applicable to the simultaneous operation of a plurality of compressors connected in parallel to each other and the single operation of a single compressor. The present invention relates to a refrigeration system that keeps operation efficiency high. 2. Description of the Related Art Conventionally, as for parallel operation by a plurality of compressors, there is a refrigeration apparatus disclosed in Japanese Patent Application Laid-Open No. 63-189744. This conventional example apparatus has two reciprocating compressors (hereinafter referred to as reciprocating compressors) each having a suction pipe and a discharge pipe connected in parallel, and condenses and liquefies the refrigerant discharged from these compressors. This is a refrigerating apparatus in which a condenser, an evaporator for evaporating and evaporating a refrigerant delivered from the condenser, and the like are sequentially connected by piping. Next, the operation of the conventional apparatus will be described. In this refrigerating apparatus, when the refrigerating load is large, two reciprocating compressors are operated, and when the refrigerating load is reduced to a certain value, the operation of one of the reciprocating compressors is stopped, and only the remaining one is operated. . However, for example, in a state where the freezing load in the freezer is reduced, that is, in a state where the refrigerant evaporation temperature in the evaporator is low, the reciprocating compressor is compared with a scroll swinging compressor (hereinafter, referred to as a scroll compressor). There was a disadvantage that the refrigerating capacity was greatly reduced (see FIG. 5). On the other hand, when the refrigeration load is large, only one of the plurality of reciprocating compressors is subjected to inverter control to finely adjust the refrigeration capacity. However, the compressor efficiency of the scroll compressor is 9
While the maximum is near 0 Hz, the compressor efficiency of the reciprocating compressor is maximum near 75 Hz, and gradually decreases after 75 Hz (see FIG. 3). Therefore, in the conventional parallel operation of a plurality of reciprocating compressors, there is a disadvantage that the range that can accurately cope with an increase in the refrigeration load is small. [0004] On the other hand, as another conventional apparatus, two parallel-connected suction pipes and two discharge pipes are connected in parallel.
There are known refrigerating apparatuses in which a plurality of scroll compressors, a condenser for condensing and liquefying the refrigerant discharged from these scroll compressors, and an evaporator for evaporating and evaporating the refrigerant discharged from the condenser are sequentially connected by piping. Have been. The control of each scroll compressor of the other conventional apparatus is the same as that in the case of the parallel operation of the reciprocating compressor. In these scroll compressors, even when the refrigerant evaporation temperature in the evaporator is low, the decrease in the refrigerating capacity is smaller than that in the reciprocating compressor (see FIG. 5). However,
Generally, the scroll compressor has a motor chamber and a compression element chamber that are not separated from each other (see FIG. 4), and thus has a weaker resistance to the return of the liquid refrigerant from the evaporator than the reciprocating compressor. Therefore, when using a scroll compressor, it is necessary to provide a low-pressure receiver between the evaporator and the compressor so that the liquid refrigerant does not return directly to the scroll compressor. There was a drawback that protection measures were required. [0006] Each of the conventional refrigeration systems is configured as described above, so that when a plurality of compressors are operating, a range which can cope with an increase in the refrigeration load. When the compressor is in a state where one of the two compressors is in operation, the refrigerating capacity is greatly reduced, or it is necessary to separately install compressor protection means for the liquid refrigerant. was there. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the related art. When a plurality of compressors are operating, the range that can cope with an increase in the refrigeration load is increased. It is an object of the present invention to provide a refrigerating apparatus which can reduce the refrigerating capacity in a state where the refrigerating load is reduced and only one compressor is operating, as compared with the related art, and which does not require a low-pressure side liquid receiver. [0010] A refrigeration apparatus according to the present invention comprises a plurality of compressors each having a variable operating capacity and having a suction pipe and a discharge pipe connected in parallel. A condenser for condensing and liquefying the refrigerant discharged from the condenser, and a refrigerating circuit sequentially connected to form a closed circuit so that the evaporator for evaporating and evaporating the refrigerant delivered from the condenser includes In a refrigeration system in which a number of compressors are operated in parallel, or the compressor with the smallest operating capacity is operated alone, among a plurality of compressors, as the compressor with the smallest operating capacity,
A scroll compressor is provided, and at least a reciprocating compressor is provided as another compressor, and the gas refrigerant on the low pressure side of the refrigeration circuit is guided to the scroll compressor, and the liquid refrigerant is provided to the reciprocating compressor. It has a gas-liquid refrigerant separation mechanism for guiding. In the refrigerating apparatus according to the present invention, when the refrigerating load is larger than a predetermined value, the scroll compressor and the reciprocating compressor are simultaneously operated in parallel. That is, by using a scroll compressor capable of fine control, the range that can cope with an increase in the refrigerating load is wider than before. On the other hand, when the refrigerating load decreases and becomes smaller than a predetermined value, only the scroll compressor having the minimum operating capacity is operated alone. As described above, even in a low refrigeration load region, the use of only the scroll compressor having a small degree of refrigeration capacity reduction causes a relatively small reduction in refrigeration capacity. Further, a low pressure side refrigerant pressure correlated with the refrigerant evaporation temperature corresponding to the refrigeration load is detected by the low pressure pressure detecting section. Then, the compressor control unit compares the detected low-pressure side refrigerant pressure with a preset pressure set value relating to the low-pressure side refrigerant pressure. Then, when the detected low-pressure-side refrigerant pressure is lower than the pressure set value, the compressor control unit switches to the single operation of only the scroll compressor in which the degree of decrease in the refrigerating capacity is small even in a low refrigerating load region. Further, the gas-liquid refrigerant separation mechanism guides the liquid refrigerant among the refrigerants on the low pressure side of the refrigeration circuit to a reciprocating compressor which is unlikely to cause liquid compression even when sucked, and converts the gas refrigerant into the liquid refrigerant. To the scroll compressor which tends to cause liquid compression. Thereby, the liquid refrigerant is not sucked into the scroll compressor. Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a refrigeration circuit diagram showing a refrigeration apparatus according to one embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a change in refrigeration capacity with respect to a refrigeration load of the refrigeration apparatus according to the present invention. FIG.
, 2a is a reciprocating compressor having a variable operating capacity by an inverter or the like, 2b is a scroll compressor having a variable operating capacity by an inverter or the like and having a smaller operating capacity than the reciprocating compressor 2a, 2d is a reciprocating compressor 2a or a scroll compressor A condenser for condensing and liquefying the high-pressure gas refrigerant compressed and sent out by the compressor 2b, a throttle device 2f for lowering the pressure of the liquid refrigerant, 2h an evaporator for evaporating and vaporizing the liquid refrigerant, 5a a reciprocating compressor 2a The suction pipe 5b is a suction pipe on the scroll compressor 2b side, 5c is a discharge pipe on the reciprocating compressor 2a side, and 5d is a discharge pipe on the scroll compressor 2b side. A refrigeration circuit is configured by connecting these sequentially with a high-pressure discharge gas pipe 2c, a high-pressure liquid pipe 2e, a low-pressure liquid pipe 2g, and a low-pressure suction gas pipe 2i so as to form a closed circuit. In the reciprocating compressor 2a and the scroll compressor 2b, suction pipes 5a and 5b are respectively connected in parallel to each suction side, and a discharge pipe 5 is connected to each discharge side.
c and 5d are respectively connected in parallel. Next, the operation of the refrigeration circuit in the refrigeration apparatus of this embodiment will be described. First, the high-temperature and high-pressure gas refrigerant discharged from the scroll compressor 2b or the reciprocating compressor 2a enters the condenser 2d via the high-pressure discharge gas pipe 2c. Here, the gas refrigerant is condensed and liquefied to become a high-pressure liquid refrigerant. This liquid refrigerant passes through a high-pressure liquid pipe 2e and is then a throttle device 2f.
Flows to The refrigerant is decompressed by the expansion device 2f and becomes a gas-liquid two-phase refrigerant in which a low-temperature and low-pressure gas and liquid are mixed. The gas-liquid two-phase refrigerant flows into the evaporator 2h via the low-pressure liquid pipe 2g, and absorbs heat and evaporates in the evaporator 2h, thereby performing, for example, indoor cooling. The refrigerant becomes low-temperature and low-pressure gas refrigerant at the outlet side of the evaporator 2h. Further, this gas refrigerant returns to the suction side of the scroll compressor 2b or the reciprocating compressor 2a via the low-pressure suction gas pipe 2i. Thus, a refrigeration cycle is formed. In this refrigerating apparatus, two compressors 2a and 2b are operated at the same time or only the scroll compressor 2b having a small operating capacity is operated independently according to the refrigerating load. For example, when the refrigeration load is high as in the region from B to C in the graph shown in FIG. 2, both the scroll compressor 2b and the reciprocating compressor 2a are operating. In this case, as shown in FIG. 3, the compressor efficiency of the reciprocating compressor 2a is maximized at around 75 Hz, whereas the compressor efficiency of the scroll compressor 2b is maximized at around 90 Hz. Capacity control can be performed more efficiently in a wider range. Therefore, the refrigeration capacity can be more appropriately responded to the refrigeration load. Embodiment 2 FIG. Second Embodiment A second embodiment of the present invention will be described mainly with reference to FIGS. 1 and 2 described above. In FIG. 1, 2j is a low-pressure pressure detector that detects the low-pressure side refrigerant pressure,
Reference numeral 2k denotes a compressor control unit which compares a signal detected by the low pressure detection unit 2j with a preset pressure set value and controls the start and stop of the operation of the reciprocating compressor 2a based on the comparison result. is there. Other components and their operations are the same as those in the first embodiment, and thus detailed description is omitted. In the refrigeration apparatus of the second embodiment having the above configuration,
As shown in FIG. 2, when the low-pressure side refrigerant pressure of the refrigeration circuit is detected by the low-pressure pressure detection unit 2j in a state where the refrigeration load is low as in the region from A to B, this detection signal is transmitted to the compressor control unit. Sent to 2k. Therefore, the compressor control unit 2k
Compares the pressure set value and the detected pressure related to the low-pressure side refrigerant pressure that is set and input in advance, and when recognizing that the detected pressure is lower than the pressure set value, stops the operation of the reciprocating compressor 2a, The operation is switched to the single operation of only the scroll compressor 2b. In this case, as shown in FIG. 5, since the refrigerating capacity of the scroll compressor 2b in the low evaporation temperature region is smaller than that of the reciprocating compressor 2a, only the efficient scroll compressor 2b is operated in the region. Thus, the operation efficiency of the refrigeration system in the low evaporation temperature range can be improved. Further, as shown in FIG. 3, the scroll compressor 2b has a wider range of compressor efficiency in the low refrigeration load region than the reciprocating compressor 2a, so that the operation efficiency of the refrigeration system can be improved. Embodiment 3 FIG. FIG. 4 is a schematic structural view showing the inside of a scroll compressor and a reciprocating compressor which constitute the refrigerating device of the refrigerating device in FIG. In FIG. 4, 3
a is a shell of the reciprocating compressor 2a, 3c is a motor chamber in which a motor (reference numerals are omitted) of the reciprocating compressor 2a,
Reference numeral 3d denotes a compression element chamber containing a crankshaft, a piston, a connecting rod and the like (all symbols are omitted), and 3b denotes a partition partitioning a motor chamber 3c and a compression element chamber 3d.
Reference numeral 4a denotes a motor chamber in which a motor (not numbered) of the scroll compressor 2b is built, and 4b denotes a compression element chamber in which a scroll-shaped fixed-side compression element and a swing-side compression element (both are not numbered). It is. Here, as is clear from the figure, the reciprocating compressor 2a is disposed below the scroll compressor 2b. Next, the operation will be described. When the refrigeration load is reduced and excess liquid refrigerant is generated, both the gas refrigerant and the liquid refrigerant on the low pressure side of the refrigeration circuit pass through the low pressure suction gas pipe 2i from the evaporator 2h to the two compressors 2a and 2b. Moving. Here, due to the action of gravity, the gas refrigerant flows into the suction pipe 5.
b to the scroll compressor 2b and the motor chamber 4a
And flows into the compression element chamber 4b. On the other hand, the liquid refrigerant is guided to the reciprocating compressor 2a via the suction pipe 5a, and flows into the motor chamber 3c. At this time, the reciprocating compressor 2a
, The motor chamber 3c and the compression element chamber 3d
Therefore, even if the liquid refrigerant flows into the reciprocating compressor 2a, the liquid refrigerant that has flowed in is temporarily stored in the motor chamber 3c, so that there is little possibility that liquid compression will occur in the compression element chamber 3d. Thus, the liquid refrigerant is supplied to the scroll compressor 2b.
To prevent the liquid from flowing into the compression element chamber 4b. That is, the vertical arrangement of the scroll compressor 2b and the reciprocating compressor 2a and the parallel connection arrangement of the suction pipes 5a and 5b constitute the gas-liquid refrigerant separation mechanism 6 in this embodiment. In the above embodiment, the gas-liquid refrigerant separation mechanism 6 utilizing the action of gravity is used. However, the present invention is not limited to the above-described gas-liquid refrigerant separation mechanism 6, but has such a structure. Alternatively, for example, the suction pipe 5a on the reciprocating compressor 2a side
So that the pressure loss of the suction pipe 5a is larger than the pressure loss of the suction pipe 5b on the scroll compressor 2b side.
The gas-liquid refrigerant separation mechanism according to the present invention can also be realized by a configuration in which the inner diameter and length of the pipe b are set respectively. In each of the above embodiments, two compressors are used as the compressors arranged in parallel. However, the present invention is not limited to this. For example, three or more compressors may be used in parallel. Is also good. Also in that case, a scroll compressor is provided as a compressor having the smallest operation capacity among the plurality of compressors. However, as the other remaining compressors having a larger operating capacity than the scroll compressor, all of the other compressors may be reciprocating compressors, or a mixture of a reciprocating compressor and another scroll compressor. It may be. As described above, according to the refrigerating apparatus of the present invention, when the scroll compressor and the reciprocating compressor are operated in parallel at the same time, the range in which the increase in the refrigerating load can be accommodated. Can be made larger than before. On the other hand, when the refrigeration load is reduced and only the scroll compressor is operating,
The decrease in the refrigerating capacity can be made smaller than before. Therefore, it is possible to operate efficiently over a wide range of the operation range. Thereby, the correspondence of the refrigerating capacity to the refrigerating load can be performed more accurately. In addition, the liquid refrigerant is guided to a reciprocating compressor which is less likely to cause liquid compression even when the liquid refrigerant is sucked, and the gas refrigerant is supplied to a scroll compressor which is likely to generate liquid compression by sucking the liquid refrigerant. Is provided, a liquid return to the scroll compressor can be rationally prevented. Since the excess liquid refrigerant is stored in the reciprocating compressor, the low-pressure side liquid receiver for the scroll compressor can be eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a refrigeration circuit diagram showing a refrigeration apparatus according to one embodiment of the present invention. FIG. 2 is an explanatory diagram showing a change in refrigeration capacity with respect to a refrigeration load of the refrigeration apparatus according to the present invention. FIG. 3 is an explanatory diagram showing changes in the respective compressor efficiencies with respect to the power supply frequency of two compressors constituting the refrigeration apparatus according to the present invention. FIG. 4 is a schematic structural view showing the inside of a scroll compressor and a reciprocating compressor that constitute the refrigeration apparatus according to the present invention. FIG. 5 is an explanatory diagram showing changes in refrigerating capacity of two compressors constituting the refrigerating apparatus according to the present invention with respect to a refrigerant evaporation temperature. [Description of Signs] 2a reciprocating compressor, 2b scroll compressor, 2c
High pressure discharge gas pipe, 2d condenser, 2e high pressure liquid pipe, 2g low pressure liquid pipe, 2h evaporator, 2i low pressure suction gas pipe, 2j low pressure pressure detection section, 2k compressor control section, 5a suction pipe, 5b suction pipe, 5c Discharge pipe, 5d
Discharge pipe, 6 gas-liquid refrigerant separation mechanism.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshiaki Yamaguchi 6-66, Tehira, Wakayama City Mitsubishi Electric Corporation Wakayama Works (56) References JP-A 5-39961 (JP, A) JP-A Heisei 3-172587 (JP, A) JP-A-5-106931 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 1/00 361

Claims (1)

(57) [Claim 1] A plurality of compressors of variable operation capacity each having a suction pipe and a discharge pipe connected in parallel, and a condensate for condensing and liquefying a refrigerant discharged from the compressor. Device, and an evaporator that evaporates and vaporizes the refrigerant delivered from the condenser includes a refrigeration circuit sequentially connected to form a closed circuit, and an appropriate number of compressors are arranged in parallel according to the refrigeration load, or In a refrigeration system in which the compressor with the smallest operating capacity is operated independently, a scroll swing compressor is provided as the compressor with the smallest operating capacity among the plurality of compressors, As the compressor, at least a reciprocating compressor is provided, and the gas refrigerant on the low pressure side of the refrigeration circuit is guided to the scroll swing compressor, and
A refrigeration apparatus comprising a gas-liquid refrigerant separation mechanism for guiding liquid refrigerant to the reciprocating compressor.