TW201627620A - Refrigeration device - Google Patents

Abstract

This refrigeration device comprises: an oil cooler 7 which subjects the oil separated by an oil separator 2 to heat exchange with a heating medium and cools the oil; an oil cooler expansion valve 6 which serves as an oil temperature adjusting means for adjusting the flow rate of the heating medium flowing into the oil cooler 7, and thus adjusting the temperature of oil supplied to a screw compressor 1; and a control device 100. In the high superheat operation in which the degree of superheat of the refrigerant gas sucked into the screw compressor 1 exceeds a preset threshold value, the control device 100 controls the oil cooler expansion valve 6 to supply the screw compressor 1 with the oil at a temperature lower than that in the steady operation in which the degree of superheat is at the threshold value or less.

Description

Freezer

The present invention relates to a refrigeration apparatus including a screw compressor.

In the conventional refrigerating apparatus, when the oil separated from the refrigerant discharged from the compressor is returned to the compressor by the oil separator, the oil is cooled by the refrigerant (see, for example, Patent Document 1 and Patent Document 2). Further, in the refrigeration systems of Patent Documents 1 and 2, the flow rate of the refrigerant which is the cooling source is controlled so that the temperature of the oil becomes the preset temperature during the steady-state operation.

[Prior patent documents] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-31420

[Patent Document 2] Japanese Patent No. 5264874

The suction superheat of the refrigerant sucked by the compressor is generally controlled to 10 ° C ~ 20 ° C during steady-state operation. However, when the suction temperature is high, the suction superheat is 50 ° C ~ 70 due to the upper limit of the low pressure. °C case.

In the refrigeration systems of Patent Documents 1 and 2, since the degree of superheat of suction increases, the discharge temperature of the refrigerant discharged from the compression unit also increases. In this case, because Since the amount of cooling heat required for cooling the compression portion is increased, when the same oil is supplied to the compressor at the time of the steady state operation, the cooling in the compression portion is insufficient. Therefore, the screw rotor of the compression portion thermally expands, and the screw rotor is in contact with the outer casing in which the screw rotor is housed, and there is a problem that defects such as melting occur.

Therefore, the gap between the screw rotor and the outer casing is generally set to be a reference even when the suction superheat is high, and therefore becomes large as necessary during steady-state operation. If the gap is too large, since the once compressed refrigerant leaks from the gap, there is a problem that the performance is lowered. In particular, such a problem is likely to occur when a high-pressure refrigerant such as R410A which tends to increase in temperature during compression is used.

The present invention has been made in view of such a problem, and an object of the invention is to provide a refrigeration system capable of suppressing expansion of a screw rotor in a state in which suction superheat is high and improving performance.

The refrigerating apparatus of the present invention comprises: a refrigerating cycle in which a screw compressor, a condenser, a pressure reducing device, and an evaporator are connected by a pipe, and a refrigerant is circulated; and the oil separator is disposed in a screw compressor and a condenser of a refrigerating cycle. And separating the oil contained in the refrigerant gas discharged from the screw compressor; the oil cooler cools the oil separated from the oil separator by heat exchange with the heat medium; the oil supply circuit is tied to the oil After the separator is cooled, it is supplied to the screw compressor; the oil temperature adjusting means adjusts the temperature of the oil supplied from the oil supply circuit to the screw compressor; and the superheat detecting means detects the overheating of the refrigerant gas sucked by the screw compressor. And the control device controls the oil temperature adjustment according to the degree of superheat; The system controls the oil temperature adjusting means to supply the oil to the screw at a lower temperature than the steady state operation in which the superheat degree is below the threshold value when the superheat degree exceeds the preset high limit super high degree operation. compressor.

According to the present invention, it is possible to obtain a refrigerating apparatus which can suppress the expansion of the screw rotor in a state where the suction superheat degree is high, and can improve the performance.

1‧‧‧ screw compressor

2‧‧‧ oil separator

3‧‧‧Condenser

4‧‧‧Main expansion valve

5‧‧‧Evaporator

6‧‧‧Expansion valve for oil cooler

7‧‧‧Oil cooler

8‧‧‧Expansion valve for motor cooling

10‧‧‧Main circuit

11‧‧‧Low section compression

12‧‧‧Intermediate pressure chamber

13‧‧‧High section compression

14‧‧‧Motor

14a‧‧‧Motor room

61‧‧‧Expansion valve for oil cooler

62‧‧‧Expansion valve for oil cooler

63‧‧‧Cooling water volume adjustment valve

63a‧‧‧Water temperature adjustment means

65‧‧‧Cooling water volume adjustment valve

70‧‧‧ oil cooling circuit

71‧‧‧Oil cooler

72‧‧‧Oil cooler

73‧‧‧Oil cooler

74‧‧‧Oil cooler

80‧‧‧Motor cooling circuit

90‧‧‧ oil supply circuit

91‧‧‧Inhalation temperature detecting device

92‧‧‧Supply oil temperature detecting device

92a‧‧‧High-end side oil supply temperature detecting device

92b‧‧‧Low-stage side oil supply temperature detecting device

93‧‧‧Inhalation pressure detecting device

94‧‧‧Solenoid valve

95‧‧‧ solenoid valve

96a‧‧‧ oil inlet

96b‧‧‧Oil export (second oil export)

96c‧‧‧Oil export (1st oil outlet)

97a‧‧‧Oil piping

97b‧‧‧Oil piping

98‧‧‧Oil piping

100‧‧‧Control device

Fig. 1 is a view showing an example of a schematic configuration of a refrigeration system according to a first embodiment of the present invention.

Fig. 2 is a flow chart showing an example of control of the refrigeration system according to the first embodiment of the present invention.

Fig. 3 is a refrigerant circuit diagram of the refrigeration system according to the second embodiment of the present invention.

Fig. 4 is a refrigerant circuit diagram of the refrigeration system according to the third embodiment of the present invention.

Fig. 5 is a refrigerant circuit diagram of a refrigeration system according to a fourth embodiment of the present invention.

Fig. 6 is a control flow chart of the refrigeration system according to the fourth embodiment of the present invention.

Fig. 7 is a refrigerant circuit diagram for explaining another oil temperature adjusting means of the oil cooler in the refrigeration system according to the fourth embodiment of the present invention.

Fig. 8 is a refrigerant circuit diagram of the refrigeration system according to the fifth embodiment of the present invention.

Fig. 9 is a view showing the flow of the refrigerant, the oil, and the cooling water during the high superheat operation of the refrigeration system according to the fifth embodiment of the present invention.

First embodiment

Fig. 1 is a view showing an example of a schematic configuration of a refrigeration system according to a first embodiment of the present invention. Here, the first embodiment is included in the drawings, and the same reference numerals are used to refer to the same or equivalents, and the embodiments described below are common. Further, the form of the constituent elements indicated in the entire patent specification is merely an example and is not limited to the form described in the patent specification.

As shown in Fig. 1, the refrigerating apparatus includes a two-stage screw compressor (hereinafter simply referred to as a screw compressor) 1, an oil separator 2, a condenser 3, a main expansion valve 4, an evaporator 5, and a flow regulating valve. The oil cooler expansion valve 6, the oil cooler 7, and the motor cooling expansion valve 8 are connected to each other by a refrigerant pipe to constitute a refrigeration cycle in which the refrigerant circulates. In the refrigerant, for example, R410A, R32, or the like is used. Further, the screw compressor 1, the oil separator 2, the condenser 3, the main expansion valve 4, and the evaporator 5 constitute a main circuit 10 of the refrigeration cycle.

Further, the refrigeration system includes an oil cooling circuit 70 that is branched from the condenser 3 and the main expansion valve 4, and then connected to the screw compressor 1 via the oil cooler expansion valve 6 and the oil cooler 7. The refrigeration system further includes a motor cooling circuit 80 that is branched from the condenser 3 and the main expansion valve 4, and then connected to the motor chamber 14a of the screw compressor 1 via the motor cooling expansion valve 8. Further, the refrigeration system includes an oil supply circuit 90.

The screw compressor 1 is a low-stage compression portion 11 and a high-stage compression portion 13 The motor 14 that rotationally drives the compression units 11 and 13 is connected in series, and the refrigerant is compressed and discharged. The intermediate pressure chamber 12 is formed between the low stage compression portion 11 and the high stage compression portion 13. Each of the low stage compression unit 11 and the high stage compression unit 13 has a screw rotor (not shown) and a gate rotor (not shown) that meshes with a screw groove provided in the screw rotor, and is configured by a screw groove (not shown). The compression chamber is compressed by a compression chamber formed by a gate rotor and an outer casing in which the screw rotor is housed. Further, the motor 14 may be a fixed speed motor or a variable frequency motor.

The main expansion valve 4, the oil cooler expansion valve 6, and the motor cooling expansion valve 8 are pressure reducing devices that depressurize and expand the refrigerant, and are configured by, for example, an electronic expansion valve that variably controls the size of the opening. Further, the oil cooler expansion valve 6 constitutes the oil temperature adjusting means of the present invention.

The oil cooling circuit 70 branches off from the condenser 3 to a part of the refrigerant of the oil cooler expansion valve 6 and depressurizes the oil cooler expansion valve 6, and then flows into the refrigerant flow path side of the oil cooler 7, and leaves the oil cooler 7 The oil separator 2 flows into the oil passage on the oil passage side of the oil cooler 7 to exchange heat, and after cooling the oil, it is supplied to the circuit of the intermediate pressure chamber 12.

The oil supply circuit 90 causes the oil separated in the oil separator 2 to flow into the oil flow path side of the oil cooler 7, and is cooled by heat exchange with the refrigerant on the refrigerant flow path side of the oil cooler 7, and then supplies the cooled oil. The circuit to the low stage compression unit 11 and the high stage compression unit 13 of the screw compressor 1.

Further, the motor cooling circuit 80 is configured such that the motor cooling expansion valve 8 steps down a part of the refrigerant from the condenser 3 to the main expansion valve 4, and supplies the depressurized refrigerant to the motor chamber 14a, thereby cooling the motor 14 The loop.

The refrigeration device further includes a suction temperature detecting device 91 and a fuel supply temperature check Measuring device 92, suction pressure detecting device 93, control device 100, and the like. The suction temperature detecting device 91 detects the temperature of the refrigerant gas sucked by the screw compressor 1. The oil supply temperature detecting means 92 detects the temperature of the oil after the oil cooler 7 is cooled. The suction pressure detecting device 93 detects the pressure of the refrigerant gas sucked by the screw compressor 1. The detected values detected by these detecting means are output to the control device 100.

The control device 100 controls the motor 14, the main expansion valve 4, the oil cooler expansion valve 6, and the motor cooling based on the detected values detected by the suction temperature detecting device 91, the oil supply temperature detecting device 92, and the suction pressure detecting device 93. Expansion valve 8.

The control device 100 appropriately sets the target oil temperature of the oil supplied from the oil supply circuit 90 to the screw compressor 1 based on the degree of superheat of the refrigerant gas sucked by the screw compressor 1, and the opening size of the expansion valve 6 for the oil cooler. It is controlled to become the set target oil temperature. This degree of superheat is determined based on the saturation temperature converted from the suction temperature detected by the suction temperature detecting device 91 and the suction pressure detected by the suction pressure detecting device 93. In this manner, the suction temperature detecting means 91 and the suction pressure detecting means 93 constitute a superheat detecting means. Further, the degree of superheat detection means that the degree of superheat can be detected, and the temperature detected by the suction temperature detecting means 91 and the temperature detecting means for detecting the temperature of the refrigerant at the inlet of the evaporator 5 can be detected. The difference in temperature is used as the degree of superheat. The control of the expansion valve 6 for the oil cooler according to the target oil temperature will be described in detail.

The control device 100 may also be constituted by a hardware such as a circuit component that realizes its function, or may be operated by an arithmetic device such as a microcomputer or a CPU. The software composition of the execution.

The refrigerating apparatus according to the first embodiment is characterized in that it is characterized by a temperature different from the setting at the time of high-temperature operation described later in the steady-state operation of the screw compressor 1 as the target oil temperature, and is operated at a high superheat degree. The target oil temperature is set to be lower than the target oil temperature during steady state operation. Specifically, the target oil temperature at the time of steady-state operation is, for example, 40° C. to 50° C., and the target oil temperature at the time of high superheat operation is, for example, 20° C. to 30° C. The high superheat operation means that the screw compressor 1 is started immediately after the start of the screw compressor and when the suction superheat degree of the steady state operation exceeds the preset threshold value. In this manner, at the time of high superheat operation, by setting the target oil temperature to a lower temperature than in the steady state operation, the thermal expansion of the screw rotor is suppressed more than the conventional control.

Further, the screw compressor 1 according to the first embodiment is a two-stage compressor that suppresses an increase in the discharge temperature of the discharged refrigerant discharged from the low-stage compression unit 11 in the two compression units 11 and 13, As a result, thermal expansion of the screw rotors in both the low stage compression unit 11 and the high stage compression unit 13 is suppressed.

Hereinafter, the operation of the refrigeration system will be described in order using the drawings.

The refrigerant compressed by the low stage compression unit 11 of the screw compressor 1 is further compressed by the high stage compression unit 13 and then discharged from the high stage compression unit 13. The refrigerant discharged from the high stage compression unit 13 is separated into refrigerant gas and oil after the oil separator 2, and then the refrigerant gas flows into the condenser 3. The refrigerant gas system that has flowed into the condenser 3 is condensed to become a refrigerant liquid, and is depressurized by the main expansion valve 4, and then sent to the evaporator 5. The refrigerant sent to the evaporator 5 exchanges heat with the air to become a refrigerant gas, and then flows into the screw compressor 1.

Further, a part of the refrigerant liquid condensed in the condenser 3 flows into the oil cooling circuit 70, and is depressurized by the expansion valve 6 of the oil cooler, and then cooled in oil. The heater 7 exchanges heat with the oil to become a refrigerant gas, and then flows into the intermediate pressure chamber 12 of the screw compressor 1. Further, the other part of the refrigerant liquid condensed by the condenser 3 flows into the motor cooling circuit 80, is depressurized by the motor cooling expansion valve 8, and is supplied to the motor chamber 14a to cool the motor 14.

On the other hand, the high-temperature oil in which the oil separator 2 and the refrigerant are separated is heat-exchanged between the oil cooler 7 and the refrigerant of the oil cooling circuit 70, and is cooled, and then supplied to the low-stage compression portion of the screw compressor 1. 11. High section compression unit 13. In the oil cooling circuit 70, the opening size of the oil cooler expansion valve 6 is controlled by the control device 100, and the temperature of the oil supplied to the screw compressor 1 is controlled by adjusting the amount of refrigerant flowing into the oil cooler 7.

Next, the control flow of the control device 100 will be described using FIG.

Fig. 2 is a flow chart showing an example of control of the refrigeration system according to the first embodiment of the present invention. The processing shown in the flowchart of Fig. 2 is implemented every control time interval.

(Step S11)

The control device 100 calculates the suction superheat degree based on the suction temperature detected by the suction temperature detecting device 91 and the suction pressure detected by the suction pressure detecting device 93. When the calculated suction superheat degree is equal to or less than the preset threshold value (for example, 40 ° C) (S11), the control device 100 determines that it is in the steady state operation, and if it exceeds the threshold value, the determination is high. When the superheat is running. Hereinafter, a process of determining the state at the time of the steady-state operation will be described, and then a process of determining the state at the time of the high-heat degree operation will be described.

<At steady state operation>

(Step S12)

The control device 100 determines the state of the steady-state operation in step S11, and sets the target oil temperature of the oil temperature to the target range (for example, 40 ° C to 50 ° C) at the steady state of the initial value (S12).

(Step S13 to Step S17)

The control device 100 controls the opening size of the oil cooler expansion valve 6 based on the oil temperature detected by the oil supply temperature detecting device 92 (S13 to S17). Specifically, the control device 100 controls the opening size of the oil cooler expansion valve 6 so that the oil temperature detected by the oil supply temperature detecting device 92 is within the target range for the steady state.

In other words, the control device 100 determines whether or not the oil temperature is equal to or greater than the target oil temperature lower limit value (the lower limit value of the target range in the steady state) (S13). When the control device 100 determines that the oil temperature is less than the target oil temperature lower limit value, the oil temperature is too low, so that the opening size of the oil cooler expansion valve 6 is made small (S14). Therefore, since the flow rate of the refrigerant flowing to the oil cooler 7 is reduced, the cooling ability of the cooling oil is lowered, and the oil temperature is increased. On the other hand, when the oil temperature is equal to or greater than the target oil temperature lower limit value, the control device 100 determines whether or not the oil temperature is equal to or lower than the target oil temperature upper limit value (the upper limit value of the target range in the steady state) (S15). When it is determined that the oil temperature exceeds the target oil temperature upper limit value, the control device 100 increases the opening size of the oil cooler expansion valve 6 (S16) because the oil temperature is too high. Therefore, since the flow rate of the refrigerant flowing to the oil cooler 7 is increased, the cooling ability of the cooling oil is increased, and the oil temperature is lowered.

The control device 100 determines that the oil temperature is equal to or lower than the target oil temperature upper limit value in step S15. Since the oil temperature is within the target range in the steady state, the current opening size of the oil cooler expansion valve 6 is maintained (S17). In addition, this The target range in the steady state is previously set to the control device 100.

In the above, steps S11 to S17 are performed every control time interval. Thereby, during the steady state operation, that is, the suction superheat degree is below the threshold value, the oil temperature can be within the target range when the steady state is used.

<When high superheat operation>

(Step S21)

The control device 100 determines the target temperature during the high superheat operation in step S11, and changes the target oil temperature of the oil temperature to a target range higher than the target range (for example, 40° C. to 50° C.) in the steady state. (for example, 20 ° C ~ 30 ° C) (S21). The target range of the high superheat degree is also set in advance in the control device 100 in the same manner as the target range in the steady state.

(Step S22 to Step S26)

The control device 100 determines whether or not the oil temperature detected by the oil supply temperature detecting device 92 is equal to or lower than the upper limit value of the target range when the superheat degree is high (S22). The control device 100 determines that the oil temperature exceeds the target oil temperature upper limit value (the upper limit value of the target range when the superheat degree is high), and since the oil system is in a state of insufficient cooling, the opening of the oil cooler expansion valve 6 is made. The size becomes larger (S23). On the other hand, when it is determined that the oil temperature is equal to or lower than the target oil temperature upper limit value, the control device 100 determines whether or not the oil temperature is equal to or lower than the target oil temperature lower limit value (lower limit value of the target range for high superheat degree) ( S24).

When the control device 100 determines that the oil temperature is less than the target oil temperature lower limit value, the oil is excessively cooled, so that the opening size of the oil cooler expansion valve 6 is made small (S25). On the other hand, when it is judged that the oil temperature is equal to or higher than the target oil temperature lower limit value, since the oil temperature is within the target range when the high superheat degree is used, the maintenance is maintained. The current opening size of the expansion valve 6 for the oil cooler (S26).

As described above, the processing from step S21 to step S26 is performed every control time interval. Therefore, in the case of high superheat operation, that is, when the suction superheat exceeds the threshold value, the temperature of the oil supplied to the screw compressor 1 can be set to be higher than the target range in the steady state. Within the target range. Therefore, even if the suction superheat exceeds the threshold value, the screw rotor (hereinafter referred to as the low-stage screw rotor) of the low-stage compression portion 11 is easily expanded, and the low-stage screw rotor can be sufficiently cooled. Therefore, the degree of expansion of the low-stage screw rotor at the time of high superheat operation can be suppressed to be small. Therefore, at the time of high superheat operation, the gap between the low-stage screw rotor and the outer casing can be set narrower than the case where the oil of the same oil temperature as in the steady-state operation is supplied to the screw compressor 1.

- Effect of the first embodiment -

As described above, in the first embodiment, it is assumed that oil having a lower temperature than that during steady-state operation is supplied to the low-stage compression unit 11 during high-heat operation. Therefore, the temperature rise of the low-stage compression portion 11 at the time of high superheat operation is suppressed, and the thermal expansion of the screw rotor of the low-stage compression portion 11 caused by insufficient cooling can be suppressed. Thereby, even if the gap between the low-stage screw rotor and the outer casing is not ensured, the contact between the low-stage screw rotor and the outer casing at the time of high superheat operation can be suppressed. As a result, the gap between the low-stage screw rotor and the outer casing can be set to be narrower than the conventional technique of not changing the temperature of the oil supplied to the low-stage compression portion 11 during steady-state operation and high-heat operation, thereby improving performance. . Further, since the low-temperature oil is supplied to the high-stage compression portion 13 during the high superheat operation, the gap between the high-stage screw rotor and the outer casing can be set narrow as in the low stage, and the performance can be improved.

In addition, according to the threshold of suction superheat (40 ° C), it is judged to be stable Mode operation or high superheat operation, but it is also possible to have this threshold.

Further, although the screw compressor 1 is an example of a two-stage screw compressor in the first embodiment, the screw compressor 1 of the refrigeration system of the present invention is not limited to a two-stage screw compressor, and may be three or more stages. The screw compressor is also a single-stage screw compressor. In the case of using a multi-stage screw compressor of three or more stages, the temperature of the oil supplied to the compression unit at the lowermost stage of the suction side may be lower than that during the steady state operation at the time of high superheat operation.

Second embodiment

In the first embodiment, the oil supply circuit 90 is provided with one oil cooler 7 and the oil having the same temperature is supplied to each of the low stage compression unit 11 and the high stage compression unit 13. In the second embodiment, the oil supply circuit 90 is provided with two oil coolers, and the oil temperature is controlled in two stages, and oil having a different temperature can be supplied to each of the low stage compression unit 11 and the high stage compression unit 13. The configuration, operation, and the like of the refrigerant circuit other than the above are the same as in the first embodiment. Hereinafter, a portion different from the first embodiment in the second embodiment will be mainly described. Further, the modified example applied to the same components as those of the first embodiment is applied to the second embodiment as well. This point is also the same in the embodiment to be described later.

Fig. 3 is a refrigerant circuit diagram of the refrigeration system according to the second embodiment of the present invention.

The oil supply circuit 90 of the refrigeration system according to the second embodiment includes two oil coolers 71 and an oil cooler 72 instead of the oil cooler 7 of the first embodiment. Further, the oil cooler 71 and the oil cooler 72 are disposed in series with each other in the oil supply circuit 90. Further, the oil cooling circuit 70 of the first embodiment shown in Fig. 1 is branched from the condenser 3 and the main expansion valve 4 and the intermediate pressure chamber 12 The connected flow path is formed. In contrast, the oil cooling circuit 70 of the second embodiment includes a refrigerant flow path that is connected to the intermediate pressure chamber 12 after being branched between the condenser 3 and the main expansion valve 4, and has an expansion of the oil cooler. The valve 61 and the oil cooler 71 are provided in one refrigerant flow path, and the oil cooler expansion valve 62 and the oil cooler 72 are provided in the other refrigerant flow path. Further, the oil cooler expansion valve 61 and the oil cooler expansion valve 62 are flow rate adjustment valves, and constitute the oil temperature adjustment means of the present invention.

Further, in each of the refrigerant flow paths in the oil cooling circuit 70, the high-stage side oil supply temperature detecting device 92a that detects the temperature of the oil supplied to the high-stage compression portion 13 is detected and supplied to the low-stage compression portion 11 The low-stage side oil supply temperature detecting device 92b of the temperature of the oil. The detected values of the high-stage side oil supply temperature detecting device 92a and the low-stage side oil supply temperature detecting device 92b are output to the control device 100.

In the refrigeration system according to the second embodiment configured as described above, the refrigerant branched between the condenser 3 and the main expansion valve 4 flows to the two refrigerant flow paths of the oil cooling circuit 70, and each branch refrigerant is used for the oil cooler. After the expansion valves 61 and 62 are depressurized, the oil coolers 71 and 72 exchange heat with the oil, and after cooling the oil, they are merged and supplied to the intermediate pressure chamber 12.

On the other hand, the oil separated in the oil separator 2 is first cooled by the oil cooler 71 after the oil supply circuit 90 is cooled, and then partially supplied to the high-stage compression unit 13, and the other flows into the oil cooler 72, and further cooled. It is supplied to the low stage compression unit 11. In this way, the oil having a lower temperature than the oil supplied to the high-stage compression portion 13 is supplied to the low-stage compression portion 11.

Further, the control device 100 is supplied to the low stage pressure when the suction superheat degree exceeds the threshold value and the superheat degree operation is the same as in the first embodiment. The target oil temperature of the oil on the side of the constricted portion 11 is changed to a lower temperature than that in the steady state operation. Further, the control device 100 controls the oil cooler expansion valve 61 and the oil cooler expansion valve 62 so that the oil temperature supplied to the low-stage compression unit 11 side detected by the low-stage side oil supply temperature detecting device 92b is changed. The target oil temperature.

Further, the target oil temperature of the oil supplied to the high-stage compression unit 13 side is not particularly limited. Since the original freezing operation in the refrigeration system is performed in the main circuit 10, the amount of refrigerant flowing to the main circuit 10 is less likely to be reduced. Therefore, if the target oil temperature of the oil supplied to the high-stage compression unit 13 side is set to be low, it is necessary to secure a large amount of the refrigerant flowing into the oil cooler 71, and the amount of the refrigerant flowing to the main circuit 10 is reduced, resulting in a decrease in performance. . Therefore, the target oil temperature of the oil supplied to the high-stage compression unit 13 side can be determined based on this point.

- Effect of the second embodiment -

In the second embodiment, the same effects as those of the first embodiment can be obtained, and the following effects can be obtained. In other words, in the second embodiment, the two oil coolers 71 and 72 are used, and only the oil supplied to the low-stage compression unit 11 has a lower target oil temperature than in the steady-state operation. Therefore, the amount of refrigerant flowing into the oil coolers 71 and 72 can be made smaller than in the first embodiment in which the oil temperature is lowered to the target oil temperature by using one oil cooler 7. As a result, the configuration of the second embodiment can improve the performance of the refrigeration system more than the first embodiment.

Third embodiment

In the second embodiment, the oil coolers 71 and 72 are arranged in series in the oil supply circuit 90. However, in the third embodiment, the oil coolers 71 and 72 are arranged in parallel. The configuration, operation, and the like of the refrigerant circuit other than the above are the same as in the second embodiment. Hereinafter, the third embodiment and the second embodiment will be mainly described. Different parts.

Fig. 4 is a refrigerant circuit diagram of the refrigeration system according to the third embodiment of the present invention.

In the refrigeration system according to the third embodiment, the oil coolers 71 and 72 are arranged in parallel in the oil supply circuit 90. Further, in the oil supply circuit 90, after the oil separator 2 is separated, the oil branched into two flows into the oil coolers 71 and 72 and is cooled, and then supplied to the low stage compression unit 11 and the high stage compression unit 13. Therefore, the oil supplied to the high stage compression unit 13 is cooled in the oil cooler 71, and the oil supplied to the low stage compression unit 11 is cooled in the oil cooler 72. According to this configuration, the temperature of the oil supplied to the high-stage compression unit 13 and the temperature of the oil supplied to the low-stage compression unit 11 are completely independent and controlled separately. Further, the oil cooler expansion valve 62 constitutes the oil temperature adjusting means of the present invention.

In the same manner as in the second embodiment, the control device 100 changes the target oil temperature of the oil supplied to the low-stage compression unit 11 side to a steady-state operation when the suction superheat degree exceeds the threshold value. Lower temperature. Further, the control device 100 controls the oil cooler expansion valve 62 so that the oil temperature detected by the low-stage side oil supply temperature detecting device 92b becomes the target oil temperature after the change. In addition, the temperature of the oil supplied to the high-stage compression unit 13 side is not particularly limited as in the second embodiment.

- Effect of the third embodiment -

In the third embodiment, the same effects as those in the second embodiment can be obtained. Further, in the third embodiment, since the oil coolers 71 and 72 are arranged in parallel in the oil supply circuit 90, the temperature of the oil supplied to the side of the low-stage compression unit 11 can be controlled only by the oil cooler expansion valve 61. Therefore, in the control supply to the low pressure The temperature of the oil on the side of the constricted portion 11 can be simplified compared to the second embodiment in which the opening size control of both the oil cooler expansion valve 61 and the oil cooler expansion valve 62 is required.

Further, the temperature of the oil supplied to the side of the high-stage compression unit 13 is not particularly limited as described above, and a strict temperature control system is not required. Therefore, the oil coolers 71 of the second embodiment and the third embodiment are configured by, for example, an air-cooled oil cooler that exchanges heat with external air to cool the oil.

Fourth embodiment

In the above-described first to third embodiments, the oil cooler 7 is a method in which the oil is cooled by using a refrigerant. However, in the fourth embodiment, the water is cooled by using water (cooling water). The configuration, operation, and the like of the refrigerant circuit other than the above are the same as in the first embodiment. Hereinafter, a portion different from the first embodiment in the fourth embodiment will be mainly described.

Fig. 5 is a refrigerant circuit diagram of a refrigeration system according to a fourth embodiment of the present invention.

The refrigeration system according to the fourth embodiment includes an oil cooler 73 that exchanges heat between the oil separated in the oil separator 2 and the cooling water supplied from the outside, and a cooling water amount adjustment valve 63 that adjusts the supply to the oil. The flow rate of the cooling water in the cooler 73 is replaced by the oil cooler 7 of the first embodiment shown in Fig. 1 . Further, in the refrigeration system according to the fourth embodiment, the oil cooling circuit 70 is removed from the refrigeration system according to the first embodiment shown in Fig. 1 . Further, the cooling water amount adjusting valve 63 constitutes the oil temperature adjusting means of the present invention.

Fig. 6 is a control flow chart of the refrigeration system according to the fourth embodiment of the present invention.

The control flow chart of the fourth embodiment shown in Fig. 6 is replaced with the cooling water amount adjusting valve 65 by the oil cooler expansion valve 6 as compared with the control flowchart of the first embodiment shown in Fig. 2 . Different from this, it is the same as the control flow chart of Fig. 2. In other words, in the case of any of the target ranges in the case of the steady state operation and the high degree of superheat, the opening size of the cooling water amount adjusting valve 65 is increased when the temperature of the oil is lowered (S16a, S23a). The amount of water passing through the cooling water of the oil cooler 73 is increased to increase the cooling capacity.

On the other hand, when the temperature of the oil is to be increased, the opening size of the cooling water amount adjusting valve 65 is made small (S14a, S25a), and the amount of cooling water passing through the oil cooler 73 is reduced to lower the cooling capacity. Moreover, when it is desired to maintain the temperature of the oil, the opening size of the cooling water amount adjustment valve 65 is kept intact (S17a, S26a).

- Effect of the fourth embodiment -

According to the fourth embodiment, the same effects as those of the first embodiment can be obtained, and the following effects can be obtained. That is, as the cooling medium for the cooling oil, since the cooling water is used instead of the refrigerant, the refrigerant flowing through the main circuit 10 can be used without cooling the oil. Therefore, the original refrigeration capacity of the refrigeration system is not lowered, and the expansion of the low-stage screw rotor can be suppressed.

Further, in the fourth embodiment, the temperature of the oil supplied to the screw compressor 1 is controlled by controlling the flow rate of the cooling water flowing into the oil cooler 73, but it may be as follows.

Fig. 7 is a refrigerant circuit diagram for explaining another oil temperature adjusting means of the oil cooler in the refrigeration system according to the fourth embodiment of the present invention.

In Fig. 7, a water temperature adjusting means 63a for controlling the temperature of the cooling water is provided, Instead of the cooling water amount adjustment valve 63 of Fig. 5 . The water temperature adjusting means 63a may be constituted by, for example, a heat exchanger and a flow rate adjusting valve that adjusts the flow rate of the heat medium in which the heat exchanger can exchange heat with the cooling water, or may be constituted by a heater. In the fourth embodiment, the flow rate of the cooling water flowing into the oil cooler 73 is always fixed, and the temperature of the cooling water is controlled by the water temperature adjusting means 63a, and the cooling ability of the oil in the oil cooler 73 is adjusted to control the oil temperature. Further, the water temperature adjusting means 63a corresponds to the oil temperature adjusting means of the present invention.

Fifth embodiment

In the fifth embodiment, as in the fourth embodiment, cooling oil is used to cool the oil. In the fourth embodiment, the oil temperature supplied to the low-stage compression unit 11 is controlled by controlling the flow rate of the cooling water supplied to the oil cooler 7. In the fifth embodiment, the flow rate of the cooling water supplied to the oil cooler 7 is not controlled, and the oil passage length supplied to the low-stage compression portion 11 is controlled by switching the length of the oil passage in the oil cooler 7. Hereinafter, a portion different from the fourth embodiment will be mainly described.

Fig. 8 is a refrigerant circuit diagram of the refrigeration system according to the fifth embodiment of the present invention.

The refrigeration system according to the fifth embodiment includes an oil cooler 74 instead of the oil cooler 73 of the fourth embodiment. The oil cooler 74 has two oil outlets 96b and 96c provided at positions different in the length of the oil flow path from the oil inlet 96a and flowing out of oil having a different temperature. The oil outlet 96b is provided on the upstream side of the oil outlet 96b, and is connected to the high-stage compression portion 13 by the oil pipe 97a. Further, the oil outlet 96c is provided at the end of the flow of the oil passing through the oil cooler 74, and is connected to the low-stage compression portion 11 by the oil pipe 97b. Further, the solenoid valve 94 is provided in the oil pipe 97a. also, The solenoid valve 95 is provided downstream of the solenoid valve 94 that connects the oil pipe 97a with the oil pipe 98 of the oil pipe 97b. By switching the solenoid valves 94 and 95, the path of the oil is changed, and the percentage of heat exchange between the oil supplied to the high stage compression unit 13 and the oil supplied to the low stage compression unit 11 is changed.

In the refrigeration system according to the fourth embodiment configured as described above, the temperature of the oil supplied to the low-stage compression unit 11 can be switched by switching between the electromagnetic valve 94 and the electromagnetic valve 95. Further, the solenoid valve 94 and the solenoid valve 95 constitute the oil temperature adjusting means of the present invention.

In the eighth drawing, the flow of the refrigerant, the oil, and the cooling water during the steady-state operation is shown. Fig. 9 is a view showing the flow of the refrigerant, the oil, and the cooling water during the high superheat operation of the refrigeration system according to the fifth embodiment of the present invention. Hereinafter, the operation of the refrigeration system according to the fourth embodiment will be described using Figs. 8 and 9 and the following first table.

The first table shows a table in which the electromagnetic valves 94 and 95 are opened and closed.

In the steady-state operation, as shown in Fig. 8 and Table 1, the control device 100 sets the solenoid valve 94 to "closed" and the solenoid valve 95 to "on". Thereby, the oil separated in the oil separator 2 is cooled by heat exchange with the cooling water in the oil cooler 74, and then flows out from the oil outlet 96c, and then branched into two, and is supplied to the low-stage compression unit 11, respectively. And the high section compression unit 13. Here, it is supplied The oil temperatures to the low stage compression unit 11 and the high stage compression unit 13 are the same temperature.

On the other hand, in the case of high superheat operation, as shown in FIG. 9 and Table 1, the control device 100 sets the solenoid valve 94 to "ON" and the solenoid valve 95 to "OFF". Thereby, a part of the oil cooled by the oil cooler 74 flows out from the oil outlet 96b before the oil outlet 96c, and is supplied to the high-stage compression unit 13. On the other hand, the remaining oil is further advanced in the oil passage in the oil cooler 74, and after being cooled, the cooling water is discharged from the oil outlet 96b and supplied to the low-stage compression portion 11. In other words, during the high-heat operation, the oil cooled in the oil cooler 74 is taken out and supplied to the high-stage compression unit 13, while the remaining oil is cooled and supplied to the low-stage compression unit. 11.

Here, the temperature of the oil supplied to the low-stage compression unit 11 during the steady-state operation and the temperature of the oil supplied to the low-stage compression unit 11 during the high-heat operation are compared. At the time of high superheat operation, the oil remaining in the cooling of the oil cooler 74 is taken out and the remaining oil is further cooled in the oil flow path from the oil outlet 96b to the oil outlet 96c. Therefore, the temperature of the oil flowing out from the oil outlet 96c during the high superheat operation is lower than the temperature of the oil flowing out from the oil outlet 96c during the steady state operation. That is, oil having a lower temperature than that during steady-state operation can be supplied to the low-stage compression portion 11 during high superheat operation.

On the other hand, since the oil flowing out from the oil outlet 96b during the high superheat operation is the oil taken out during the cooling, the temperature is higher than the oil flowing out from the oil outlet 96b during the steady state operation.

- Effect of the fifth embodiment -

According to the fifth embodiment, the same effects as those of the fourth embodiment can be obtained, and the following effects can be obtained. That is, in the oil cooler 74, When the amount of cooling water and the temperature of the cooling water inlet are not changed, oil having a lower temperature than that during steady-state operation can be supplied to the low-stage compression portion 11 during high-heat operation.

Further, in the fourth and fifth embodiments described above, water is used as the heat medium for exchanging heat between the oil cooler 74 and the oil, but water may be used alone or in combination with water and an additive having high anti-corrosion effect. Mixture, etc.

1‧‧‧ screw compressor

2‧‧‧ oil separator

3‧‧‧Condenser

4‧‧‧Main expansion valve

5‧‧‧Evaporator

6‧‧‧Expansion valve for oil cooler

7‧‧‧Oil cooler

8‧‧‧Expansion valve for motor cooling

10‧‧‧Main circuit

11‧‧‧Low section compression

12‧‧‧Intermediate pressure chamber

13‧‧‧High section compression

14‧‧‧Motor

14a‧‧‧Motor room

70‧‧‧ oil cooling circuit

80‧‧‧Motor cooling circuit

90‧‧‧ oil supply circuit

91‧‧‧Inhalation temperature detecting device

92‧‧‧Supply oil temperature detecting device

93‧‧‧Inhalation pressure detecting device

100‧‧‧Control device

Claims (12)

A refrigerating device comprising: a refrigerating cycle connecting a screw compressor, a condenser, a pressure reducing device and an evaporator with a pipe, and a refrigerant circulating; an oil separator, the screw compressor and the condenser disposed in the refrigerating cycle And separating the oil contained in the refrigerant gas discharged from the screw compressor; the oil cooler cools the oil separated by the oil separator and the heat medium; the oil supply circuit, Cooling the oil separated by the oil separator by the oil separator, and supplying the oil to the screw compressor; the oil temperature adjusting means adjusts the temperature of the oil supplied to the screw compressor from the oil supply circuit; The degree detecting means detects the superheat degree of the refrigerant gas sucked by the screw compressor; and the control device controls the oil temperature adjusting means according to the superheat degree; the control means is that the superheat degree exceeds the preset When the threshold value is high in superheat operation, the oil temperature adjusting means is controlled to supply oil having a lower temperature than the steady state operation in which the superheat degree is below the threshold value to the screw compressor The refrigeration device of claim 1, wherein the oil temperature adjusting means adjusts a flow rate of the heat medium flowing into the oil cooler; and an oil cooling circuit is provided, the oil cooling circuit is from the condenser and the pressure reducing device After branching, connecting to the screw compressor via the flow regulating valve and the oil cooler; The heat medium in which the oil cooler exchanges heat with the oil is the refrigerant. The refrigerating device of claim 2, wherein the control device increases the opening size of the flow regulating valve to a flow rate of the heat medium flowing into the oil cooler when the high superheat operation is performed. The time is increasing. The refrigeration system according to any one of claims 1 to 3, wherein the screw compressor is a multi-stage screw compressor having a plurality of compression portions; the oil supply circuit supplies oil to the plurality of compression portions Each of the circuits; during the high superheat operation, the oil having a lower temperature than the steady state operation is supplied to the lowermost compression portion of the lowest of the plurality of compression portions. The refrigeration apparatus of claim 4, wherein the oil supply circuit comprises a plurality of the oil coolers arranged in series with each other, and the oil is located on a most downstream side of the plurality of oil coolers. The oil flowing out of the cooler is supplied to the low-stage compression portion. The refrigerating apparatus of claim 4, wherein the oil supply circuit comprises a plurality of the oil coolers arranged side by side in parallel with each other, and each of the oils branched into a plurality of oils after the oil separator is separated After the plurality of oil coolers are cooled, they are supplied to the plurality of compression sections. A refrigerating apparatus according to claim 1, wherein the heat medium is water; and the oil temperature adjusting means is a flow regulating valve that adjusts a flow rate of the water flowing into the oil cooler. The refrigerating device of claim 7, wherein the control device controls the flow regulating valve during the high superheat operation to increase the flow rate of water flowing into the oil cooler more than the steady state operation. The refrigerating apparatus of claim 1, wherein the thermal medium is water; and the oil temperature adjusting means is a water temperature adjusting means for adjusting the temperature of the water flowing into the oil cooler. A refrigerating device according to claim 9, wherein the control device controls the water temperature adjusting means to cause water having a lower temperature than the steady state operation to flow into the oil cooler during the high superheat operation. The refrigerating apparatus according to any one of claims 7 to 10, wherein the screw compressor is a multi-stage screw compressor having a plurality of compression portions; when the high superheat operation is performed, the temperature is operated more than the steady state The lower oil is supplied to the lowermost section of the plurality of compression sections. The refrigeration device of claim 11, wherein the thermal medium is water; and the screw compressor is a multi-stage screw compressor having a plurality of compression portions; the oil cooler has: a first oil outlet, a part of the oil in the middle of cooling is taken out; and the second oil outlet is taken out after the end of the remaining oil flow to the oil flow path in the oil cooler; the steady state operation is from the second oil The oil taken out from the outlet is supplied to the plurality of compression units, and the high degree of superheat operation is performed by taking a part of the oil flowing into the oil cooler from the first oil outlet during cooling, and supplying the oil to the plurality of compression units. On the other hand, the remaining oil is passed to the end of the oil passage, and the heat is exchanged with the heat medium, and then taken out from the second oil outlet. The configuration is supplied to the low-stage compression unit.