JP2013113535A - Binary refrigerating device - Google Patents

Abstract

[PROBLEMS] To perform an operation in which the pressure ratio of a low-source side refrigeration cycle and the pressure ratio of a high-source side refrigeration cycle are maintained within an appropriate range with a simple configuration that does not require switching to unit operation even in the case of operating conditions that result in a low pressure ratio. Obtain a possible binary refrigeration system.
A binary refrigeration apparatus includes a low-source side compressor 2, a cascade heat exchanger 9, a low-side expansion valve 5, and a low-side heat exchanger 6, and a high-side compression. The high-end side heat exchanger 13, the high-end side expansion valve 14, and the high-end side refrigeration cycle having the cascade heat exchanger are thermally connected via the cascade heat exchanger. Yes. In addition, a target intermediate temperature in the cascade heat exchanger is set from a set value of an outlet temperature of a medium to be heat-exchanged in the high-source side heat exchanger, and the low-source side compressor is set so as to be the target intermediate temperature. Control means 50 for controlling is provided.
[Selection] Figure 1

Description

  The present invention relates to a binary refrigeration apparatus having a low refrigeration cycle and a high refrigeration cycle.

  As a conventional binary refrigeration apparatus, there is one described in JP 2000-274848 A (Patent Document 1).

  The thing of this patent document 1 connects a primary side refrigerant circuit (low original refrigeration cycle) and a secondary refrigerant circuit (high original refrigeration cycle) via a refrigerant heat exchanger (cascade heat exchanger). The binary refrigeration apparatus includes switching means for switching between a binary refrigeration cycle operation and a unit refrigeration cycle operation. And in the thing of this cited reference 1, in the case of the driving | running condition which becomes a low pressure ratio according to outside air, it switches to unit operation and it is trying to improve energy saving property.

JP 2000-274848 A

  However, in the thing of the said patent document 1, although it enables it to switch between unit operation and two-way operation, when switching from two-way operation to unit operation, one compressor must be stopped, When the compressor is stopped, there is a problem that the behavior of the refrigerant in the refrigeration cycle changes greatly and operation is disturbed.

  In addition, to switch between unit operation and unit operation, the secondary refrigerant circuit differs in the proper amount of refrigerant between the unit operation and unit operation, and refrigerant pipes and heat exchangers used only during unit operation It is necessary to adjust the amount of refrigerant accumulated in the tank. Furthermore, the secondary refrigerant circuit requires two refrigerant pipes and a heat exchanger for two-way operation and one-unit operation, and the required volume of the entire heat exchanger and the length of the refrigerant pipe increase. There is also a problem of increasing the size.

  The object of the present invention is to maintain the pressure ratio of the low-source side refrigeration cycle and the pressure ratio of the high-source side refrigeration cycle within an appropriate range with a simple configuration that does not require switching to unit operation even under operating conditions that result in a low pressure ratio. It is to obtain a binary refrigeration apparatus that can be operated.

  In order to achieve the above object, the present invention provides a low-side compressor, a cascade heat exchanger, a low-side expansion valve, a low-side refrigeration cycle having a low-side heat exchanger, a high-side compressor, In the binary refrigeration apparatus configured to be connected to the high-side refrigeration cycle having the main-side heat exchanger, the high-side expansion valve, and the cascade heat exchanger through the cascade heat exchanger. The target intermediate temperature in the cascade heat exchanger is set from the set value of the outlet temperature of the medium that is heat-exchanged in the high-end heat exchanger, and the low-end compressor is controlled to be the target intermediate temperature. It is characterized by including a control means.

  Other features of the present invention include a low-source side compressor, a cascade heat exchanger, a low-side expansion valve, a low-side refrigeration cycle having a low-side heat exchanger, a high-side compressor, and a high-side heat. In the binary refrigeration apparatus, wherein the high-side refrigeration cycle having the exchanger, the high-side expansion valve, and the cascade heat exchanger is thermally connected via the cascade heat exchanger, A medium inlet temperature detector that detects the inlet temperature of the medium to be heat exchanged by the original heat exchanger is provided, and the target intermediate temperature in the cascade heat exchanger is set from the medium inlet temperature detected by the medium inlet temperature detector. And providing a control means for controlling the low-source compressor so that the target intermediate temperature is reached.

  According to the present invention, the pressure ratio of the low-source side refrigeration cycle and the pressure ratio of the high-source side refrigeration cycle are maintained within an appropriate range with a simple configuration that does not require switching to unit operation even in the case of operating conditions that result in a low pressure ratio. It is possible to obtain a binary refrigeration apparatus that can be operated.

The refrigeration cycle block diagram which shows Example 1 of the binary refrigeration apparatus of this invention. 3 is a flowchart for explaining control of a high-end compressor in the first embodiment. 3 is a flowchart for explaining control of a low-source compressor according to the first embodiment. 3 is a flowchart for explaining control of a high-side expansion valve in the first embodiment. The diagram which shows the appropriate relationship between the setting value of the high-source side heat exchanger medium outlet temperature, and the target intermediate temperature setting value. The refrigeration cycle block diagram which shows Example 2 of the binary refrigeration apparatus of this invention. The diagram which shows the appropriate relationship between the high-source-side heat exchanger medium inlet temperature and the target intermediate temperature set value. 9 is a flowchart for explaining control of a low-source compressor in the second embodiment. 9 is a flowchart for explaining control of a high-end compressor in the second embodiment.

  Hereinafter, specific examples of the binary refrigeration apparatus of the present invention will be described with reference to the drawings. In each figure, the part which attached | subjected the same code | symbol has shown the part which is the same or it corresponds.

A first embodiment of the binary refrigeration apparatus of the present invention will be described with reference to FIGS.
FIG. 1 is a configuration diagram of a refrigeration cycle showing a first embodiment of the binary refrigeration apparatus of the present invention. The two-way refrigeration apparatus includes a low-side refrigeration cycle 1 and a high-side refrigeration cycle 10.

The low-source side refrigeration cycle 1 is a main component such as a low-source side compressor 2, a low-source side four-way switching valve 3, a cascade heat exchanger 9, a receiver 4, an expansion valve 5, and a low-source side heat exchanger 6. It is configured. The high-source side refrigeration cycle 10 includes a high-side compressor 11, a high-side four-way switching valve 12, a high-side heat exchanger 13, a high-side expansion valve 14, the cascade heat exchanger 9, and an accumulator 15. It consists of main components such as.
The low refrigeration cycle 1 and the high refrigeration cycle 10 are thermally connected via the cascade heat exchanger 9 to constitute the binary refrigeration apparatus. Note that the low-end compressor 2 and the high-end compressor 11 are configured to supply lubricating oil to a sliding portion such as a bearing by differential pressure.

  The binary refrigeration apparatus of the present embodiment is a refrigeration apparatus intended for heating operation. The low-source side refrigeration cycle 1 uses R410A, which is a high-pressure refrigerant, and the high-source side refrigeration cycle 10 uses a low-pressure refrigerant. An example using R134a will be described. In addition, a refrigerant | coolant is not restricted to these, A various appropriate refrigerant | coolant can be used according to a use.

  In the binary refrigeration apparatus for the heating operation of the present embodiment, the cascade heat exchanger 9 functions as an evaporator as the high-source side refrigeration cycle 10 and functions as a condenser as the low-source side refrigeration cycle 1. . That is, in this cascade heat exchanger 9, the high pressure side gas refrigerant from the low-source side refrigeration cycle 1 and the low-pressure gas-liquid two-phase refrigerant from the high-source side refrigeration cycle 10 exchange heat so that the high-source side The refrigerant of the refrigeration cycle 10 is gasified, and the refrigerant of the low-source side refrigeration cycle 1 is condensed and liquefied.

The operation of the low original refrigeration cycle 1 and the high original refrigeration cycle 10 will be described in more detail.
In the low-source side refrigeration cycle 1, the refrigerant compressed by the low-source side compressor 2 becomes high-pressure gas, passes through the low-source side four-way switching valve (four-way valve) 3, and then flows into the cascade heat exchanger 9. It liquefies by exchanging heat with the two-phase refrigerant of the side refrigeration cycle 10. After passing through the receiver 4, the liquid refrigerant is decompressed by the low-side expansion valve 5 to become a gas-liquid two-phase refrigerant, and exchanges heat with air taken in by the fan in the low-side heat exchanger (air heat exchanger) 6. It is evaporated and gasified. This gas refrigerant passes through the four-way valve 3 again, and then is sucked into the compressor 2 and compressed again into high-pressure gas, and the same cycle is repeated thereafter. An accumulator may be provided on the suction side of the compressor 2 in the low-source side refrigeration cycle.

  In the high-side refrigeration cycle 10, the refrigerant compressed by the high-side compressor 11 becomes high-pressure gas, passes through the high-side four-way switching valve (four-way valve) 12, and then enters the inlet piping in the high-side heat exchanger 13. Heat exchange with a medium such as warm water supplied from 35 liquefies. This liquid refrigerant is decompressed and expanded by the high-side expansion valve 14 to become a gas-liquid two-phase refrigerant, flows into the cascade heat exchanger 9, and exchanges heat with the gas refrigerant in the low-side refrigeration cycle for gasification. Is done. After passing through the four-way valve 12 again, this gas refrigerant passes through the accumulator 15 and is sucked into the compressor 11 and compressed again into high-pressure gas, and the same cycle is repeated thereafter. The medium such as hot water is circulated by a pump so as to flow into the high-side heat exchanger 13 from the inlet pipe 35 and is heated here, and then supplied from the outlet pipe 36 to the customer. Thus, the supply of hot water and the like is continued.

  As the cascade heat exchanger 9 and the high-end heat exchanger 13, a plate heat exchanger, a double tube heat exchanger, a shell and tube heat exchanger, or the like may be used. Moreover, when using these heat exchangers, it is preferable that the heat exchanged refrigerants or the refrigerant and the medium are counterflows, but they can also be parallel flows. As the low-source heat exchanger 6, an air-cooled heat exchanger or the like is used when outside air is used as a heat source, and a plate heat exchanger or two-type heat exchanger 6 is used when water or brine is used as a heat source. It is better to use a heavy tube heat exchanger.

  The low-source side refrigeration cycle 1 detects a temperature detector 21 for detecting the refrigerant temperature on the discharge side of the compressor 2 and a liquid refrigerant temperature (intermediate temperature) on the outlet side of the cascade heat exchanger 9. An intermediate temperature detector 22 is provided.

  The high-side refrigeration cycle 10 includes a pressure detector 41 for detecting the discharge pressure of the compressor 11, a temperature detector 31 for detecting the temperature of the suction gas refrigerant to the compressor 11, and the compression A pressure detector 42 for detecting the suction pressure of the machine 11, a temperature of hot water (medium) flowing out from the outlet pipe 36 connected to the high-source side heat exchanger 13, that is, a medium for detecting the hot water outlet temperature An outlet temperature detector 32 is provided.

  Reference numeral 50 denotes a control device for controlling the entire binary refrigeration apparatus. The control device 50 includes temperature information detected by the temperature detectors 21, 22, 31 and 32, and pressure detectors 41 and 42. The detected pressure information is taken in, and the compressors 2 and 11 and the expansion valves 5 and 14 are controlled based on the information.

Next, the control of the binary refrigeration apparatus by the control device 50 will be described with reference to FIGS.
The control of the high-end compressor 11 will be described with reference to the flowchart shown in FIG. First, the target temperature of a medium such as hot water flowing out from the high-end side heat exchanger (condenser) 13 of the high-end side refrigeration cycle 10, that is, the high-end side heat exchanger medium outlet temperature (heat exchanged with the high-pressure gas refrigerant). The target temperature of the generated medium is set (step S11). At this time, the target intermediate temperature of the low-source side refrigeration cycle 1 in the cascade heat exchanger 9 is set according to the set value of the high-source side heat exchanger medium outlet temperature (step S12). This target intermediate temperature set value is set so that the pressure ratio is appropriately secured in the low-source side refrigeration cycle 1. The target intermediate temperature is preferably set so that the pressure ratio of the low-source side refrigeration cycle and the pressure ratio of the high-source side refrigeration cycle can be balanced. For example, as shown in FIG. 5, an appropriate relationship between the set value of the high-end side heat exchanger medium outlet temperature and the target intermediate temperature set value is stored in the controller 50 as a diagram. Based on this diagram, the target intermediate temperature may be set.

  When the high-source-side heat exchanger medium outlet temperature is set in step S11 of FIG. 2, the medium outlet detected by the medium outlet temperature detector 32 provided in the outlet pipe 36 in step S13. The temperature is compared with a set value (set outlet temperature) of the high-side heat exchanger medium outlet temperature. As a result, if the detected medium outlet temperature is lower than the set outlet temperature, the frequency (rotational speed) of the high-end compressor 11 is increased (step 14). On the contrary, if the detected medium outlet temperature is higher than the set outlet temperature, the frequency of the high-end compressor 11 is lowered (step 15). Thereafter, the process returns to step S13 again, and the same control is repeated every 10 seconds, for example.

  As described above, the operation capacity of the high-end compressor 11 is controlled by the control device 50 so that the temperature detected by the medium outlet temperature detector 32 becomes the set outlet temperature (target set temperature). It is.

Next, the control of the low-source compressor 2 in the control device 50 will be described with reference to the flowchart shown in FIG. In the control of the low-side compressor 2, the set value of the target intermediate temperature set in step 12 in FIG. 2 is used. Further, the temperature (intermediate temperature) detected by the intermediate temperature detector 22 for detecting the liquid refrigerant temperature on the outlet side of the cascade heat exchanger 9 is used. That is, in step S16, the intermediate temperature detected by the intermediate temperature detector 22 is compared with the target intermediate temperature. As a result, if the detected intermediate temperature is lower than the target intermediate temperature, the frequency (rotational speed) of the low-source compressor 2 is increased (step 17). On the contrary, if the detected intermediate temperature is higher than the target intermediate temperature, the frequency of the low-source side compressor 2 is lowered (step 18). Thereafter, the process returns to step S16 again, and the same control is repeated, for example, every 3 minutes.
Thus, the control of the operating capacity of the low-side compressor 2 is performed by the control device 50 so that the temperature detected by the intermediate temperature detector 22 becomes the target intermediate temperature.

Next, the control of the high-side expansion valve 14 in the control device 50 will be described with reference to the flowchart shown in FIG.
First, in step S21, the temperature detector 31 detects the temperature of the suction gas (gas refrigerant) sucked into the high-end compressor 11. Further, in step S22, the discharge gas pressure of the high-end compressor 11 detected by the pressure detector 41 and the intake gas pressure of the high-end compressor 11 detected by the pressure detector 42 are detected. To do. Then, the pressure ratio before and after the high-side compressor 11 is obtained from the detected discharge gas pressure and intake gas pressure. Further, the control device 50 stores a lower limit value of the pressure ratio in the high-end compressor 11. The lower limit value of the pressure ratio is set so that, for example, in the high-side compressor 11 and the reduction-side compressor 2, a differential pressure that can supply lubricating oil to a sliding portion such as a bearing can be secured.

  Next, in step S23, it is determined whether or not the pressure ratio obtained in step S23 is approaching the pressure ratio lower limit value stored in the control device 50, and the obtained pressure ratio is the pressure ratio lower limit value. If it is determined that the pressure is below the vicinity, the opening of the high-side expansion valve 14 is reduced to control the pressure ratio to increase (step S24). When the pressure ratio is maintained appropriately (when it is sufficiently larger than the pressure ratio lower limit value), the high-side expansion valve 14 is normally controlled (step S25).

  The normal control of the high-side expansion valve 14 is performed by the control device 50 as follows. That is, the refrigerant saturation temperature is calculated from the pressure value obtained from the pressure detector 42, and the degree of superheat on the compressor suction side is calculated from the intake refrigerant temperature obtained from the temperature detector 31. When the calculated degree of superheat is large, control is performed to increase the opening degree of the high-side expansion valve 14, and when the degree of superheat is small, the liquid return operation is not performed for the compressor 11. Thus, the opening degree of the high-side expansion valve 14 is controlled to an appropriate opening degree. Preferably, the opening degree of the high-side expansion valve 14 is controlled so that the degree of superheat on the compressor suction side is constant.

  The control of the low-side expansion valve 5 of the low-side refrigeration cycle 1 is also performed from the control device 50. In this control, the refrigerant discharge gas temperature detected by the temperature detector 21 provided in the discharge pipe of the low-side compressor 2 is set to the set value of the target intermediate temperature in the cascade heat exchanger 9 (see FIG. 2). ), The opening degree of the expansion valve 5 is controlled so that the target discharge gas temperature is determined.

  A pressure detector is provided in the discharge pipe of the compressor 2, and the degree of superheat is obtained from the discharge pressure value detected by the pressure detector and the discharge temperature detected by the temperature detector 21. The opening degree of the expansion valve 5 may be controlled. Alternatively, a pressure detector and a temperature detector may be provided on the suction side of the compressor 2, and the degree of superheat from the detected values may be obtained to control the opening degree of the expansion valve 5.

  In the above-described binary refrigeration apparatus of the present embodiment, the intermediate temperature detected by the intermediate temperature detector 22 is also an index that means a balance between the low original refrigeration cycle and the high original refrigeration cycle. When the detected intermediate temperature becomes a predetermined temperature, for example −2 ° C. or less, with respect to the target intermediate temperature shown in step S16 of FIG. 3, the operating capacity (operating frequency) of the compressor 11 is temporarily fixed ( Maintenance). In addition, when the intermediate temperature is, for example, −5 ° C. or less with respect to the target intermediate temperature, the operating capacity (operating frequency) of the compressor 11 is decreased and the intermediate temperature is raised. good.

  Moreover, in the said Example, the low pressure of the said low side refrigeration cycle 1 is substantially determined by the temperature of the outdoor air supplied to the low side heat exchanger 6, and the high pressure of the said high side refrigeration cycle 10 is , Determined by the hot water (medium) outlet temperature of the high-end heat exchanger 13.

  Here, when it is desired to take out the high-temperature water, the target intermediate temperature described above is also set high, so that it is easy to ensure the pressure ratio between the low-side refrigeration cycle 1 and the high-side refrigeration cycle 10. When the outside air temperature is high, the number of heat exchanges can be reduced by reducing the rotational speed of the fan that supplies outdoor air to the reduction-side heat exchanger 6 accordingly, and the operation can be continued while keeping the low-pressure pressure appropriately. .

  However, when hot water having a hot water temperature of 30 ° C. or less is taken out, the most severe condition is set. In this case, the target intermediate temperature is set to a lower limit value that can secure a pressure ratio in the low-side refrigeration cycle 1. Is done. Regarding the high-source side refrigeration cycle 10, since the take-out temperature is low, the high-pressure pressure is low, and the difference from the low-pressure pressure of the high-source side refrigeration cycle 10 determined by the intermediate temperature in the cascade heat exchanger 9 is small. For this reason, in the high-source side refrigeration cycle 10, the pressure ratio becomes small, and an appropriate pressure ratio cannot be ensured. Therefore, when the pressure becomes close to the minimum pressure ratio at which oil can be supplied to the sliding portion such as the bearing of the high-end compressor 11, the high-side expansion valve 14 is controlled by the control device 50 as described with reference to FIG. Is controlled so as to reduce the low pressure. Thereby, the pressure ratio in the high-source side refrigeration cycle 10 can be secured, and stable operation can be continued.

  Thus, according to the present embodiment, even in the case of operating conditions where the load is small and the pressure ratio is low, it is not necessary to switch to unit operation, with a simple configuration, The operation | movement which maintained the appropriate pressure ratio which can supply oil to the sliding part of each compressor 2 and 11 is attained.

  In addition, since the target intermediate temperature is set according to the set temperature of the extracted hot water, a stable and efficient operation can be performed while maintaining a balance between the low-source side refrigeration cycle 1 and the high-source side refrigeration cycle 10. Furthermore, in the cascade heat exchanger 9, the high pressure of the low-source side refrigeration cycle 1 and the low pressure of the high-source side refrigeration cycle 10 are determined, so the pressure ratio of the low-source side refrigeration cycle and the pressure of the high-source side refrigeration cycle are determined. Operation is possible while maintaining the ratio at an appropriate value. In addition, since the low-source side refrigeration cycle 1 is controlled so as to reach the set target intermediate temperature, the high-source-side refrigeration cycle 10 is an operation that does not depend on the outside air, and a stable operation is possible.

  Furthermore, in this embodiment, since it is a simple configuration that does not need to be switched to unit operation, the length of the entire refrigerant pipe can be shortened, and the refrigerant flow path of the low-source side heat exchanger 6 is only one system. The heat exchanger can also be made smaller.

  A second embodiment of the binary refrigeration apparatus of the present invention will be described with reference to FIGS. In these drawings, the portions denoted by the same reference numerals as those in FIGS. 1 to 5 indicate the same or corresponding portions, and the description of the same portions is omitted.

  FIG. 6 is a refrigeration cycle configuration diagram showing Embodiment 2 of the binary refrigeration apparatus of the present invention. The difference between the binary refrigeration apparatus of the second embodiment and the binary refrigeration apparatus of the first embodiment will be described. In the first embodiment, the target intermediate temperature of the low-source side refrigeration cycle 1 in the cascade heat exchanger 9 is set to the medium outlet temperature in the high-source side heat exchanger 13 of the high-source side refrigeration cycle 10 (warm water extraction temperature). It is set according to. On the other hand, in the second embodiment, a medium outlet temperature detector 33 for detecting the inlet temperature of the medium (hot water) in the high-side heat exchanger 13 of the high-side refrigeration cycle 10 is provided. According to the inlet temperature of the medium detected by the detector 33, the target intermediate temperature of the low-source side refrigeration cycle 1 in the cascade heat exchanger 9 is set.

  For example, as shown in FIG. 7, an appropriate relationship between the high-end side heat exchanger medium inlet temperature and the target intermediate temperature set value is stored in the control device 50 in a diagram form. The target intermediate temperature may be set based on the figure.

  That is, when the medium inlet temperature to the high-source side heat exchanger 13 is high, the target intermediate temperature set value is also increased to prevent an increase in the pressure ratio in the high-source side refrigeration cycle 10. Conversely, when the medium inlet temperature to the high-source side heat exchanger 13 is low, the target intermediate temperature set value is also lowered to prevent the pressure ratio in the high-source side refrigeration cycle 10 from becoming too low. Thus, the diagram shown in FIG. 7 is created. Further, in the diagram shown in FIG. 7, the target intermediate temperature set value is determined by both the high-side refrigeration cycle 10 and the low-side refrigeration cycle 1 according to the medium inlet temperature to the high-side heat exchanger 13. In order to ensure an appropriate pressure ratio, the temperature is set to a temperature at which the pressure ratio of both cycles can be balanced.

Data as shown in FIG. 7 is stored in the control device 50, and detection data of the medium inlet temperature to the high-source side heat exchanger 13 detected by the temperature detector 33 is also taken in. Based on these data, the control device 50 determines the target intermediate temperature (cascade heat exchange) of the low-source side refrigeration cycle 1 in the cascade heat exchanger 9 according to the medium inlet temperature to the high-source side heat exchanger 13. The target value of the outlet temperature of the vessel 9) is set, for example, every certain time.
Setting of the outlet temperature of the medium (hot water) flowing out from the high-source side heat exchanger 13 is also performed by the control device 50.

Next, the control of the dual refrigeration apparatus by the control apparatus 50 in the present embodiment will be described with reference to FIGS.
The control of the low-side compressor 2 in the control device 50 will be described with reference to the flowchart shown in FIG. In the control of the low-source side compressor 2, first, in step S <b> 30, the medium inlet temperature detector 33 detects the medium inlet temperature to the high-source side heat exchanger 13. Next, the process proceeds to step S31, where the low temperature in the cascade heat exchanger 9 is determined based on the data shown in FIG. 7 stored in the controller 50 from the medium inlet temperature detected by the medium inlet temperature detector 33. A target intermediate temperature of the side refrigeration cycle 1 is set. In step S16, the intermediate temperature detected by the intermediate temperature detector 22 for detecting the liquid refrigerant temperature on the outlet side of the cascade heat exchanger 9 is compared with the target intermediate temperature. As a result, if the detected intermediate temperature is lower than the target intermediate temperature, the frequency of the low-source compressor 2 is increased (step 17). On the contrary, if the detected intermediate temperature is higher than the target intermediate temperature, the frequency of the low-source side compressor 2 is lowered (step 18). Thereafter, the process returns to step S16 again, and the same control is repeated, for example, every 3 minutes.

  Thus, in the present embodiment, the operation capacity of the low-side compressor 2 is controlled according to the temperature detected by the intermediate temperature detector 22 according to the medium inlet temperature to the high-side heat exchanger 13. To achieve the target intermediate temperature.

  Next, the control of the high-end compressor 11 will be described with reference to the flowchart shown in FIG. First, the target temperature of the medium flowing out from the high-source side heat exchanger 13 of the high-source side refrigeration cycle 10, that is, the high-source side heat exchanger medium outlet temperature is set (step S11). When the high-source side heat exchanger medium outlet temperature is set, the set value of the high-source side heat exchanger medium outlet temperature and the medium outlet temperature detected by the medium outlet temperature detector 32 are set in step S13. Are compared. As a result, if the detected medium outlet temperature is higher than the set outlet temperature, the process proceeds to step S15, and control is performed so as to lower the frequency of the high-side compressor 11. Conversely, when the detected medium outlet temperature is lower than the set outlet temperature, in this embodiment, the process proceeds to step S32, and the liquid refrigerant temperature on the outlet side of the cascade heat exchanger 9 is detected. The intermediate temperature detected by the intermediate temperature detector 22 is compared with the target intermediate temperature set in step S31 of FIG. In step S32, if the detected intermediate temperature is equal to or higher than “target intermediate temperature −2 ° C.”, the process proceeds to step S14, and the frequency of the high-end compressor 11 is increased. Conversely, if the detected intermediate temperature is less than “target intermediate temperature −2 ° C.”, the process proceeds to step S33, and control is performed to maintain the frequency of the high-end compressor 11. Further, when the intermediate temperature becomes, for example, “target intermediate temperature −5 ° C.” or less, the operating capacity (operating frequency) of the compressor 11 may be reduced to raise the intermediate temperature.

  Since the intermediate temperature detected by the intermediate temperature detector 22 is also an index indicating a balance between the low-source side refrigeration cycle and the high-source side refrigeration cycle, in this embodiment, the intermediate temperature is the target intermediate When the temperature is less than −2 ° C., the operating capacity of the high-end compressor 11 is temporarily fixed.

  Thereafter, the process returns to step S13 again, and the same control is repeated every 10 seconds, for example.

  Thus, in this embodiment, the operation capacity of the high-end compressor 11 is controlled so that the temperature detected by the medium outlet temperature detector 32 becomes the set outlet temperature (target set temperature). However, it is also controlled in consideration of the intermediate temperature of the low-side refrigeration cycle coming out of the cascade heat exchanger 9.

Note that the control of the high-side expansion valve 14 and the control of the low-side expansion valve 5 are the same as those in the first embodiment, and a description thereof will be omitted.
Further, in the two-way refrigeration apparatus, the four-way valve 12 of the high-side refrigeration cycle and the four-way valve 3 of the low-side refrigeration cycle are controlled so as not to become unmatched.
Other configurations are the same as those of the first embodiment. Also in the second embodiment, the same effect as in the first embodiment can be obtained, but this embodiment is particularly effective for the control at the time of starting the binary refrigeration apparatus. That is, at the time of starting the binary refrigeration apparatus, the outlet temperature of the medium flowing out from the high-side heat exchanger 13 is low and not stable, but the set value of the medium outlet temperature is the same as the steady state. The target intermediate temperature in the cascade heat exchanger 9 is not necessarily in a balanced state. On the other hand, in the second embodiment, the target intermediate temperature is set based on the temperature detected by the medium inlet temperature detector 33 even at the time of start-up, so that the balance between the high source side and the low source side is balanced. A stable operation is possible.

  Therefore, the first embodiment and the second embodiment are combined, and the control is performed by setting the target intermediate temperature according to the second embodiment at the time of start-up, and the control is performed by setting the target intermediate temperature according to the first embodiment when the steady state is reached. It is also effective to implement it.

  In addition, although the binary refrigeration apparatus of each said Example demonstrated the example of the refrigeration apparatus aiming at heating operation, it can implement similarly to the refrigeration apparatus aiming at cooling operation. In addition, the present invention is particularly effective by using a compressor of a type that supplies lubricating oil by differential pressure as the low-end compressor 2 and the high-end compressor 11, but the present invention is not limited to this. Absent.

1: Low source side refrigeration cycle 2: Low source side compressor 3: Low source side four-way switching valve (four-way valve),
4: Receiver,
5: Low original side expansion valve, 6: Low original side heat exchanger,
9: Cascade heat exchanger,
10: Higher-side refrigeration cycle,
11: High-source side compressor, 12: High-source side four-way switching valve (four-way valve),
13: High side heat exchanger, 14: High side expansion valve,
15: Accumulator,
21, 31: temperature detector, 22: intermediate temperature detector,
32: Medium outlet temperature detector, 33: Medium inlet temperature detector,
35: Inlet piping, 36: Outlet piping,
41, 42: pressure detector,
50: Control device (control means).

Claims (12)

Low original side compressor, cascade heat exchanger, low original side expansion valve, low original side refrigeration cycle with low original side heat exchanger, high original side compressor, high original side heat exchanger, high original side expansion valve In the binary refrigeration apparatus configured to be thermally connected to the high refrigeration cycle having the cascade heat exchanger via the cascade heat exchanger,
The target intermediate temperature in the cascade heat exchanger is set from the set value of the outlet temperature of the medium that is heat-exchanged in the high-source side heat exchanger, and the low-source side compressor is controlled so as to be the target intermediate temperature. A binary refrigeration apparatus comprising a control means. Low original side compressor, cascade heat exchanger, low original side expansion valve, low original side refrigeration cycle with low original side heat exchanger, high original side compressor, high original side heat exchanger, high original side expansion valve In the binary refrigeration apparatus configured to be thermally connected to the high refrigeration cycle having the cascade heat exchanger via the cascade heat exchanger,
A medium inlet temperature detector for detecting an inlet temperature of a medium to be heat exchanged by the high-source side heat exchanger is provided, and a target intermediate temperature in the cascade heat exchanger is determined from the medium inlet temperature detected by the medium inlet temperature detector. And a control unit that controls the low-side compressor so as to reach the target intermediate temperature.   3. The binary refrigeration apparatus according to claim 1, further comprising an intermediate temperature detector that detects an outlet side temperature of the low-side refrigerant of the cascade heat exchanger, wherein the control means is detected by the intermediate temperature detector. The binary refrigeration apparatus, wherein the frequency of the low-side compressor is controlled so that the obtained temperature becomes the target intermediate temperature.   The binary refrigeration apparatus according to any one of claims 1 to 3, wherein the target intermediate temperature is balanced between a pressure ratio of the low-side refrigeration cycle and a pressure ratio of the high-side refrigeration cycle, and the low A binary refrigeration apparatus, characterized in that the pressure ratio in the original refrigeration cycle is set appropriately.   The binary refrigeration apparatus according to claim 1, wherein the target intermediate temperature varies depending on a set value of the medium outlet temperature of the high-source side refrigeration cycle, and when the set value of the medium outlet temperature is high, the target intermediate temperature is changed. By setting the intermediate temperature also high, an increase in the pressure ratio of the high-source side refrigeration cycle is prevented, and when the set value of the medium outlet temperature is low, the target intermediate temperature is also set low so that the high-source side refrigeration cycle A two-stage refrigeration apparatus characterized in that the pressure ratio is prevented from becoming too small.   The binary refrigeration apparatus according to claim 2, wherein the target intermediate temperature varies depending on the detected medium inlet temperature of the high-source side refrigeration cycle, and the target medium temperature is high when the detected medium inlet temperature is high. By setting the intermediate temperature also high, an increase in the pressure ratio of the high-source side refrigeration cycle is prevented, and when the detected medium inlet temperature setting value is low, the target intermediate temperature is also set low, A binary refrigeration apparatus characterized in that the pressure ratio of the side refrigeration cycle is prevented from becoming excessively small.   The binary refrigeration apparatus according to any one of claims 1 to 6, wherein a medium outlet temperature detector that detects an outlet temperature of a medium that is heat-exchanged by the high-source side heat exchanger is provided, and the control means includes A binary refrigeration apparatus, wherein the frequency of the high-end compressor is controlled so that a value detected by a medium outlet temperature detector approaches a set value of the medium outlet temperature.   The binary refrigeration apparatus according to any one of claims 1 to 7, wherein a pressure detector that detects a pressure on a discharge side of the high-side compressor and a pressure on a suction side of the high-side compressor are detected. A pressure detector, and a pressure ratio before and after the high-side compressor is obtained from a discharge gas pressure and a suction gas pressure detected by the pressure detector, and the control means includes a pressure in the high-side compressor. The lower limit value of the ratio is stored, the stored pressure ratio lower limit value is compared with the determined pressure ratio, and the determined pressure ratio is equal to or lower than the vicinity of the pressure ratio lower limit value. In such a case, the two-stage refrigeration apparatus controls the opening degree of the high-side expansion valve to be small.   The binary refrigeration apparatus according to claim 8, further comprising a temperature detector that detects a temperature on the suction side of the high-side compressor, wherein the obtained pressure ratio is more than the vicinity of the pressure ratio lower limit value. If larger, the intake refrigerant temperature detected by the intake side temperature detector detected by the high side compressor and the intake gas detected by the pressure detector for detecting the suction side pressure of the high side compressor And calculating the degree of superheat on the suction side of the high-side compressor from the pressure, and controlling the opening degree of the high-side expansion valve so that the degree of superheat is substantially constant. Refrigeration equipment.   The binary refrigeration apparatus according to any one of claims 1 to 9, further comprising a temperature detector that detects a temperature on a discharge side of the low-side compressor, and a discharge gas temperature of the refrigerant that is detected by the temperature detector. , Wherein the opening degree of the low-side expansion valve is controlled so as to be a target discharge gas temperature determined from a set value of the target intermediate temperature in the cascade heat exchanger .   The binary refrigeration apparatus according to any one of claims 1 to 10, wherein at least one of the cascade heat exchanger and the high-side heat exchanger is a plate heat exchanger, and the low-side heat exchanger is A binary refrigeration system comprising an air-cooled heat exchanger.   The binary refrigeration apparatus according to any one of claims 1 to 11, wherein each of the low-side refrigeration cycle and the high-side refrigeration cycle includes a four-way switching valve, and is configured to be able to switch between a heating operation and a cooling operation. A two-stage refrigeration apparatus characterized by being made.

Images