JP6327986B2 - Compressor / pump switching type cooling device - Google Patents

Description

The present invention relates to a compressor / pump switching type cooling device,
Specifically, a compressor cycle operation in which the refrigerant is circulated by the compressor in the order of the compressor, the outside air heat exchanger, the expansion valve, and the load side heat exchanger in a state of bypassing the stopped refrigerant pump,
Refrigerant circulation capable of switching between pump cycle operation in which refrigerant is circulated by the refrigerant pump in the order of the refrigerant pump, the load-side heat exchanger, and the outside air heat exchanger in a state in which the stopped compressor is bypassed. Set up a road,
In the compressor cycle operation, heat is radiated to the outside air by condensing the refrigerant in the outside air heat exchanger, and in parallel with this, the load medium is cooled by evaporating the refrigerant in the load side heat exchanger,
In the pump cycle operation, the refrigerant exchanges heat with the low-temperature outside air in the outside heat exchanger to cool and condense the refrigerant and dissipate heat to the outside air. In parallel with this, the refrigerant in the load-side heat exchanger The present invention relates to a compressor / pump switching type cooling device that heats and evaporates refrigerant and cools the load medium by exchanging heat with the load medium.

  Conventionally, in this type of cooling device, as seen in Patent Document 1, the refrigerant pumped out from the outside heat exchanger in the pump cycle operation is directly sucked into the refrigerant pump.

  In general, the refrigerant delivered from the outside air heat exchanger is directly sucked into the refrigerant pump through the liquid receiver.

  Further, in the apparatus shown in Patent Document 1, when switching between the compressor cycle operation and the pump cycle operation, both the compressor and the refrigerant pump are stopped, and the bypass valve for the compressor and the bypass valve for the refrigerant pump are stopped. The state in which both are opened to allow the refrigerant to flow naturally is continued for a predetermined time, and then the compressor cycle operation or pump cycle operation of the switching destination is started.

  That is, by continuing the state in which the refrigerant naturally flows for a predetermined time in this manner, each part of the refrigerant circulation path (especially an outside air heat exchanger that functions as a refrigerant condenser) in switching between the compressor cycle operation and the pump cycle operation. In order to prevent a large pressure change from occurring.

JP 2000-274774 A

  However, in the conventional device in which the refrigerant sent from the outside air heat exchanger in the pump cycle operation is sucked into the refrigerant pump as it is, the refrigerant condensation due to heat exchange with the outside air in the outside air heat exchanger is insufficient due to changes in outside air conditions, etc. Therefore, it is necessary to prevent the refrigerant mixed with the gas phase from being sucked into the refrigerant pump and causing cavitation in the refrigerant pump.

  For this reason, the conventional apparatus measures the degree of supercooling of the refrigerant at the refrigerant outlet of the outside air heat exchanger in the pump cycle operation, and adjusts the refrigerant flow rate in the outside air heat exchanger based on the measurement result. Therefore, the supercooling degree control for adjusting the supercooling degree of the refrigerant at the refrigerant outlet of the cooler is always required in the pump cycle operation, which causes a problem that the control configuration of the apparatus becomes complicated.

  Further, when the refrigerant is allowed to naturally flow over a predetermined time when switching between the compressor cycle operation and the pump cycle operation, there arises a problem that the cooling of the load medium is interrupted during the predetermined time period.

  In view of this situation, the main problem of the present invention is to eliminate the above-mentioned problem by rational improvement.

A first characteristic configuration of the present invention relates to a compressor / pump switching type cooling apparatus,
Compressor cycle operation in which the refrigerant is circulated by the compressor in the order of the compressor, the outside air heat exchanger, the expansion valve, and the load side heat exchanger in a state of bypassing the stopped refrigerant pump,
Refrigerant circulation capable of switching between pump cycle operation in which refrigerant is circulated by the refrigerant pump in the order of the refrigerant pump, the load-side heat exchanger, and the outside air heat exchanger in a state in which the stopped compressor is bypassed. Set up a road,
In the compressor cycle operation, heat is radiated to the outside air by condensing the refrigerant in the outside air heat exchanger, and in parallel with this, the load medium is cooled by evaporating the refrigerant in the load side heat exchanger,
In the pump cycle operation, the refrigerant exchanges heat with the low-temperature outside air in the outside heat exchanger to cool and condense the refrigerant and dissipate heat to the outside air. In parallel with this, the refrigerant in the load-side heat exchanger The compressor / pump switching type cooling device that heats and evaporates the refrigerant and cools the load medium by exchanging heat with the load medium,
In the pump cycle operation, a refrigerant cooler that cools the refrigerant sucked by the refrigerant pump by exchanging heat with a cooling heat medium from the outside air heat exchanger in the refrigerant circulation path to the refrigerant pump in the refrigerant flow direction. Intervening in the middle of the part ,
A controller for performing switching between the compressor cycle operation and the pump cycle operation;
When the controller switches from the pump cycle operation to the compressor cycle operation, the controller reduces the output of the refrigerant pump, thereby increasing the superheat degree of the refrigerant at the refrigerant outlet of the load side heat exchanger. Performing the pump cycle operation,
In the pump cycle operation in this superheat degree securing mode, when the superheat degree of the refrigerant at the refrigerant outlet of the load side heat exchanger rises to a set allowable value or when a set time has elapsed, the pump cycle The configuration is such that the operation is switched from the operation to the compressor cycle operation .

  According to this configuration, even when the refrigerant mixed with the gas phase is sucked into the refrigerant pump in the pump cycle operation, the refrigerant mixed with the gas phase is used for cooling in the refrigerant cooler prior to being sucked into the refrigerant pump. Cooling by heat exchange with the heat medium can be surely condensed and a sufficient degree of supercooling can be obtained, thereby reliably preventing the refrigerant mixed with the gas phase from being sucked into the refrigerant pump. Occurrence of cavitation in the pump can be prevented.

Therefore, the supercooling degree control that measures the supercooling degree of the refrigerant at the refrigerant outlet of the outdoor air heat exchanger and adjusts the supercooling degree of the refrigerant at the refrigerant outlet of the outdoor air heat exchanger based on the measurement result is operated in the pump cycle. Therefore, it is possible to simplify the control configuration of the apparatus and to reduce the apparatus cost.

The cooling heat medium that exchanges heat with the refrigerant in the refrigerant cooler may be either a gas heat medium such as air or a liquid heat medium such as water.

In the first feature configuration,
A controller for performing switching between the compressor cycle operation and the pump cycle operation;
When the controller switches from the pump cycle operation to the compressor cycle operation, the controller reduces the output of the refrigerant pump, thereby increasing the superheat degree of the refrigerant at the refrigerant outlet of the load side heat exchanger. Performing the pump cycle operation,
In the pump cycle operation in this superheat degree securing mode, when the superheat degree of the refrigerant at the refrigerant outlet of the load side heat exchanger rises to a set allowable value or when a set time has elapsed, the pump cycle Since the operation is switched from the operation to the compressor cycle operation, the following effects can be obtained.

In other words, in the pump cycle operation in the superheat degree securing mode, switching to the compressor cycle operation is performed in a state where the refrigerant superheat degree at the refrigerant outlet of the load side heat exchanger is sufficiently increased. Even if the refrigerant mixed with the liquid phase is sent from the load-side heat exchanger in the pump cycle operation until the pump cycle operation is performed, the refrigerant mixed with the liquid phase is sucked into the compressor in the compressor cycle operation after switching. This so-called liquid back can be reliably prevented.

In addition, since the pump cycle operation in the superheat degree securing mode is performed only when switching from the pump cycle operation to the compressor cycle operation to increase the superheat degree of the refrigerant at the refrigerant outlet of the load side heat exchanger, Superheat degree control is performed in the pump cycle operation to measure the superheat degree of the refrigerant at the refrigerant outlet of the exchanger and adjust the superheat degree of the refrigerant at the refrigerant outlet of the load side heat exchanger based on the measurement result. As compared with the above, it is possible to simplify the control configuration of the apparatus, and it is also possible to avoid that the cooling function for the load medium in the pump cycle operation is limited by the normal superheat degree control.

When switching from the pump cycle operation to the compressor cycle operation when the set time has elapsed in the pump cycle operation in the superheat securing mode, an accumulator (gas-liquid separator) is installed on the refrigerant suction side of the compressor. It is desirable to equip it to further prevent liquid back.

The second feature configuration of the present invention is a configuration suitable for the implementation of the first feature configuration.
In the switching between the compressor cycle operation and the pump cycle operation, the controller starts and stops the compressor, starts and stops the refrigerant pump, and switches the refrigerant path in the refrigerant circuit. Alternatively, it is configured to perform at almost the same timing.

According to this configuration, when switching between the compressor cycle operation and the pump cycle operation as described above, both the compressor and the refrigerant pump are stopped, and both the bypass valve for the compressor and the bypass valve for the refrigerant pump are opened. Compared to starting the compressor cycle operation or the pump cycle operation of the switching destination after continuing the state of allowing the refrigerant to flow naturally through the valve for a predetermined time, and at the time of switching between the compressor cycle operation and the pump cycle operation. In this respect, the load medium can be continuously cooled, and in this respect, the apparatus can have a higher cooling function for the load medium.

In addition, switching from the compressor cycle operation to the pump cycle operation is performed by performing the start / stop of the compressor, the start / stop of the refrigerant pump, and the switching of the refrigerant path in the refrigerant circulation path at the same timing. In this case, the outside air heat exchanger that had been receiving the discharge action of the compressor suddenly receives the suction action of the refrigerant pump, and the pressure of the outside air heat exchanger suddenly drops. Even if the condensed refrigerant that has been sent from the vessel or the condensed refrigerant that has been sent from the outdoor air heat exchanger and accumulated in the liquid receiver partially evaporates, the refrigerant mixed with the gas phase is sucked into the refrigerant pump. As described above, the refrigerant mixed with the gas phase can be completely condensed by cooling with the refrigerant cooler and can be sucked into the refrigerant pump in a state where a sufficient degree of supercooling is obtained. Never interfere with the pump cycle operation.

In addition, the stop of a compressor said here means the time of the completion of the residual operation, when the residual operation of a compressor is implemented following provision of a compressor stop command.

The third characteristic configuration of the present invention is a configuration suitable for implementing the first or second characteristic configuration ,
The controller, after switching from the pump cycle operation to the compressor cycle operation, limits the output of the compressor and sets the opening of the expansion valve to a set limit opening until a set transient time elapses. The compressor cycle operation is performed in the holding stabilization mode,
The stabilization mode in the compressor cycle operation is canceled when the set transient time has elapsed.

  According to this configuration, the transient instability of the compressor cycle operation immediately after switching from the pump cycle operation in the above-described superheat degree securing mode to the compressor cycle operation is performed in the compressor cycle operation in the stabilization mode. Therefore, the cooling function for the load medium can be maintained well even immediately after switching from the pump cycle operation to the compressor cycle operation.

Refrigerant circuit diagram in compressor cycle operation Refrigerant circuit diagram in pump cycle operation state Mollier diagram showing compressor cycle operation and pump cycle operation Timing chart showing switching to pump cycle operation Timing chart showing the mode of switching to compressor cycle operation Mollier diagram explaining obstacles when there is no refrigerant cooler operation Mollier diagram explaining operation switching when operating a refrigerant cooler Graph showing changes in each value when switching to pump cycle operation Mollier diagram explaining failure when there is no execution of superheat degree securing mode Mollier diagram explaining operation switching when executing the superheat degree securing mode Graph showing changes in each value when switching to compressor cycle operation Flow chart for switching to compressor cycle operation Correlation diagram showing pump cycle operating range Flow chart for switching to pump cycle operation Graph showing correlation between outside air temperature, refrigerant condensing pressure and heat transfer surface state Graph showing change in condensing pressure when switching to compressor cycle operation A graph showing the correlation between outside air flow rate, cooling capacity and heat transfer surface condition Graph showing change in outside air flow rate when switching to pump cycle operation Graph showing the correlation between evaporating pressure and condensing pressure and cooling capacity Flow chart for switching to compressor cycle operation

  FIG. 1 shows a compressor / pump switching type cooling device C that uses outside air as a heat radiation source, and a load side heat exchanger 2 that functions as a refrigerant evaporator is provided in a circulation path 1 of the refrigerant R in the cooling device C. The evaporation pressure regulating valve 3, the compressor 4, the outside air heat exchanger 5 that functions as a refrigerant condenser, the liquid receiver 6, the refrigerant cooler 7, the refrigerant pump 8, the pressure reducing valve 9, and the expansion valve 10 Are arranged in that order.

  The refrigerant circulation path 1 is provided with a compressor bypass path 11 that bypasses the compressor 4 and a compressor bypass valve 11 a that opens and closes the compressor bypass path 11, and a refrigerant cooler 7 and a refrigerant pump 8 A pump bypass passage 12 that bypasses the series arrangement with the pressure reducing valve 9 and a pump bypass valve 12a that opens and closes the pump bypass passage 12 are provided.

  Further, on the side of the compressor 4 from the connection location of the compressor bypass passage 11, on-off valves 11 b and 11 c are provided on the refrigerant suction side and the refrigerant discharge side of the compressor 4, and further from the connection location of the pump bypass passage 12. On the refrigerant pump 8 side, an open / close valve 12b is provided on the refrigerant discharge side of the refrigerant pump 8.

  The outside air OA, which is a heat radiation source, is passed through the outside air heat exchanger 5 by the outside air fan 13, and heat is exchanged between the outside air OA and the refrigerant R in the outside air heat exchanger 5.

  The load-side heat exchanger 2 is passed through the load-side air IA as a load medium by the load-side blower 14, and heat is exchanged between the load-side air IA and the refrigerant R in the load-side heat exchanger 2.

  In the refrigerant circuit 1 in the cooling device C, the compressor cycle operation shown in FIG. 1 and the pump cycle operation shown in FIG. 2 are alternatively performed. In the compressor cycle operation, as shown in FIG. By closing the bypass valve 11a and the on-off valve 12b and opening the pump bypass valve 12a and the on-off valves 11b and 11c to operate the compressor 4, the refrigerant cooler 7, the stopped refrigerant pump 8 and the decompression pressure in the refrigerant circuit 1 are reduced. The refrigerant R is circulated through the pump bypass 12 in a state of bypassing the valve 9.

  That is, in the compressor cycle operation, basically, as in a general compression refrigeration circuit, the vapor-phase high-pressure refrigerant R compressed by the compressor 4 is condensed in the outside heat exchanger 5 as a refrigerant condenser, The refrigerant condensation heat is radiated to the outside air OA ventilated by the outside air fan 13.

  The liquid-phase high-pressure refrigerant R condensed in the outside air heat exchanger 5 is passed through the receiver 6 and the pump bypass passage 12 through the expansion valve 10 and opened to the low-pressure region. The load side heat exchanger 2 is evaporated, and the refrigerant evaporating heat at that time is taken away from the load side air IA ventilated by the load side blower 14, thereby cooling the load side air IA.

  The vapor-phase low-pressure refrigerant R evaporated in the load-side heat exchanger 5 is sucked into the compressor 4 through the evaporation pressure regulating valve 3 and compressed again.

  On the other hand, in the pump cycle operation, as shown in FIG. 2, the refrigerant bypass path 12a and the on-off valves 11b and 11c are closed and the compressor bypass valve 11a and the on-off valve 12b are opened to operate the refrigerant pump 8. 1, the refrigerant R is circulated through the compressor bypass 11 in a state where the stopped compressor 4 is bypassed.

  That is, in the pump cycle operation, basically, the liquid phase refrigerant R is sent from the refrigerant pump 8 to the load side heat exchanger 2 as a refrigerant evaporator through the pressure reducing valve 9 and the expansion valve 10 to load the liquid phase refrigerant R. In the side heat exchanger 2, heat is exchanged with the load side air IA ventilated by the load side blower 14, thereby heating and evaporating the liquid refrigerant R and cooling the load side air IA.

  The vapor-phase refrigerant R evaporated in the load-side heat exchanger 2 (in some cases, the gas-phase refrigerant mixed with a liquid phase) is sent to the outside air heat exchanger 5 as a refrigerant condenser through the evaporation pressure adjusting valve 3 and the compressor bypass passage 11. Thus, the gas-phase refrigerant R is heat-exchanged with the outside air OA ventilated by the outside-air fan 13 in the outside-air heat exchanger 5, thereby cooling and condensing the gas-phase refrigerant C, and the refrigerant R is subjected to the previous load side heat. In the exchanger 2, the heat acquired from the load side air IA is radiated to the wind outside air OA.

  The liquid-phase refrigerant R condensed in the outside air heat exchanger 5 is sucked into the refrigerant pump 8 through the liquid receiver 6 and the refrigerant cooler 7 and sent again to the load-side heat exchanger 2.

  In FIG. 3, the solid line shows the Mollier diagram in the compressor cycle operation, the broken line shows the Mollier diagram in the pump cycle operation, and the respective symbols in the diagram are as follows.

Compressor cycle operation (solid line)
pe: Evaporating pressure of refrigerant R in load side heat exchanger 2 (refrigerant evaporator) pc: Condensing pressure of refrigerant R in outside air heat exchanger 5 (refrigerant condenser) SH: Load side heat exchanger 2 (refrigerant evaporator) SC: The degree of supercooling of the refrigerant R at the refrigerant outlet of the outside air heat exchanger 5 (refrigerant condenser)

Pump cycle operation (broken line)
pe ′: Evaporation pressure of the refrigerant R in the load-side heat exchanger 2 (refrigerant evaporator) pc ′: Condensation pressure of the refrigerant R in the outside air heat exchanger 5 (refrigerant condenser) SC ′: At the refrigerant outlet of the refrigerant cooler 7 Supercooling degree of refrigerant R

  The controller 15 in the cooling device C executes the following controls a to d in the compressor cycle operation.

  a. Superheat degree control: The superheat degree SH is set by measuring the superheat degree SH of the refrigerant R at the refrigerant outlet of the load-side heat exchanger 2 and adjusting the opening degree of the expansion valve 10 based on the measurement result. Adjust to.

  b. Compressor suction pressure control: Measure the suction pressure ps, which is the pressure of the refrigerant R at the inlet of the compressor 4, and adjust the drive frequency of the compressor 4 based on the measurement result (inverter control). The suction pressure ps is adjusted to the set suction pressure pss.

  c. Cooling capacity control: measuring the balance state between the load calorie q of the load side air IA and the cooling capacity Q of the cooling device C, and adjusting the opening of the evaporating pressure adjusting valve 3 based on the measurement result, thereby rejecting device The cooling capacity Q of C (specifically, the cooling amount of the load-side air IA in the load-side heat exchanger 2) is a value (Q = q) corresponding to the load heat amount q (that is, the necessary cooling amount) of the load-side air IA. Adjust to.

  d. Outside air volume control: The condensation pressure pc of the refrigerant R in the outside air heat exchanger 5 is measured, and when the measured condensation pressure pc is larger than the set lower limit value pcmin, the outside air fan 13 is operated at 100% output. In a situation where the condensation pressure pc is less than the set lower limit value pcmin, the refrigerant in the outside air heat exchanger 5 is adjusted by adjusting the output of the outside air fan 13 (in other words, the ventilation amount fo of the outside air OA with respect to the outside air heat exchanger 5). The condensation pressure pc of R is adjusted to the set lower limit value pcmin.

  On the other hand, the controller 15 executes the following controls e and f in the pump cycle operation.

  e. Cooling capacity control: By measuring the balance state between the load heat quantity q of the load side air IA and the cooling capacity Q of the cooling device C, and adjusting the drive frequency of the refrigerant pump 8 based on the measurement result (inverter control), The cooling capacity Q of the cooling device C (specifically, the amount of cooling of the load-side air IA in the load-side heat exchanger 2) is a value commensurate with the load heat amount q (that is, the necessary cooling amount) of the load-side air IA (Q = q).

  f. Cooler operation: Cooling medium CW such as cooling air or cooling water is supplied to the refrigerant cooler 7 to cool the passing refrigerant R in the refrigerant cooler 7 by exchanging heat with the cooling medium CW. .

  In the pump cycle operation, the opening degree of the expansion valve 10 and the opening degree of the evaporation pressure adjusting valve 3 are fixed at a set opening degree (generally fully open), and the outside air fan 13 is operated at 100% output. .

  The pump cycle operation uses the low-temperature outside air OA, and the operation of the refrigerant pump 8 instead of the operation of the compressor 4 is advantageous in terms of energy saving as compared with the compressor cycle operation. However, the temperature of the outside air OA increases. During the warm season, the compressor cycle operation is required to obtain the cooling capacity Q corresponding to the load heat quantity q (necessary cooling quantity) of the load side air IA.

  From this, the controller 15 automatically determines whether or not switching from the compressor cycle operation to the pump cycle operation is appropriate, and whether or not the switching from the pump cycle operation to the compressor cycle operation is appropriate. The switching between the compressor cycle operation and the pump cycle operation is automatically executed according to the determination result.

  Specifically, when the controller 15 determines that the switching from the compressor cycle operation to the pump cycle operation is appropriate, as shown in FIG. 4, the controller 15 stops the compressor 4, the compressor bypass valve 11a, and the open / close state. Switching of the refrigerant path by opening the valve 12b and closing the pump bypass valve 12a and the on-off valves 11b and 11c and the activation of the refrigerant pump 8 and the refrigerant cooler 7 are performed at the same timing (or almost the same timing). Execute to switch from compressor cycle operation to pump cycle operation.

  If the controller 15 determines that the switching from the pump cycle operation to the compressor cycle operation is appropriate, the controller 15 first switches the current pump cycle operation from the normal mode to the superheat degree securing mode as shown in FIG.

  In the pump cycle operation in the superheat degree securing mode, the controller 15 reduces the flow rate of the refrigerant R by lowering the driving frequency of the refrigerant pump 8 to the set limiting frequency, so that the refrigerant of the load-side heat exchanger 2 is reduced. The superheat degree SH ′ of the refrigerant R at the outlet is increased.

  Then, when the measured superheat degree SH ′ increases to the set allowable value SHm (or the set time elapses) in the pump cycle operation in the superheat degree securing mode, as shown in FIG. The same timing is used for stopping the compressor 7, switching the refrigerant path by opening the pump bypass valve 12a and the on-off valves 11b and 11c, closing the compressor bypass valve 11a and the on-off valve 12b, and starting the compressor 4. (Or almost the same timing) to switch from pump cycle operation to compressor cycle operation.

  Thus, in the switching between the compressor cycle operation and the pump cycle operation, the refrigerant path by starting / stopping the compressor 4, starting / stopping the refrigerant pump 8, and opening / closing of the valves 11a, 11b, 11c, 12a, 12b. The load-side air IA is continued in the load-side heat exchanger 2 even when switching between the compressor cycle operation and the pump cycle operation by performing the above three operations at the same timing (or almost the same timing). Can be cooled.

  Here, in switching from the compressor cycle operation to the pump cycle operation, the compressor 4 is simply stopped, the refrigerant pump 8 is started, and the refrigerant path is switched at the same timing in a state where the refrigerant cooler 7 is not operated. 6, as schematically indicated by an arrow xx ′ in FIG. 6, the high-temperature refrigerant R sent from the outside air heat exchanger 5 in the compressor cycle operation and the high-temperature refrigerant R accumulated in the liquid receiver 6 are Due to the pressure drop accompanying the switching to the pump cycle operation, the refrigerant pump 8 enters the gas phase / liquid phase mixing region from the liquid phase region during the suction process to the refrigerant pump 8, and a part of the gas phase is vaporized. Cavitation occurs in the refrigerant pump 8 in a state where the mixed refrigerant is sucked.

  On the other hand, when the supply of the cooling heat medium CW to the refrigerant cooler 7 is started and the operation of the refrigerant cooler 7 is started at the time of switching to the pump cycle operation, the arrow xx in FIG. ′, The high-temperature refrigerant R sent from the outside air heat exchanger 5 or the high-temperature refrigerant R accumulated in the liquid receiver 6 in the compressor cycle operation is more suitable for cooling by the refrigerant cooler 7. The refrigerant pump 8 can be sucked in a state in which the degree of supercooling SC ′ is secured and kept in the liquid phase region, thereby preventing cavitation in the refrigerant pump 8.

  Further, in the pump cycle operation, the refrigerant cooler 7 is continuously operated to maintain an appropriate degree of supercooling SC ′, so that it is not necessary to measure the degree of supercooling SC ′ and to control the degree of supercooling based on the measurement result. In addition, the control configuration of the refrigeration circuit C can be simplified.

  In consideration of the time required for the cooling heat medium CW to start to sufficiently flow into the refrigerant cooler 7, the operation start of the refrigerant cooler 7 precedes the switching to the pump cycle operation as shown by the broken line in FIG. May be performed.

  FIG. 8 shows experimental results when the compressor cycle operation is switched to the pump cycle operation by stopping the compressor 4, starting the refrigerant pump 8 and the refrigerant cooler 7, and switching the refrigerant path at the same timing. Indicates.

  As can be seen from FIG. 8, in the cooling device C, when the compressor cycle operation is switched to the pump cycle operation, the outlet air temperature of the load side heat exchanger 2 (that is, the load side heat exchanger 2 is sent out). Although the temperature of the load-side air IA after cooling slightly rises, the temperature returns to the original temperature quickly within a few minutes, and the cooling of the load-side air IA in the load-side heat exchanger 2 is generally good continuity. Is secured.

  Further, when the compressor cycle operation is switched to the pump cycle operation, the refrigerant cooler 7 also prevents the condensing pressure pc of the refrigerant R in the outside air heat exchanger 5 from rapidly decreasing (pc → pc ′). The effective suction head (NPSH) in the refrigerant pump 8 is maintained at a required value (necessary NPSH) or more due to the cooling of the passing refrigerant R at, thereby preventing the occurrence of cavitation in the refrigerant pump 8.

  On the other hand, in switching from the pump cycle operation to the compressor cycle operation, the refrigerant pump 8 is simply stopped, the compressor 4 is started, and the refrigerant path is switched at the same timing in a state where the superheat degree securing mode is not performed. As shown schematically by arrows yy ′ in FIG. 9, when the refrigerant R mixed with the liquid phase is sent from the load-side heat exchanger 2 as the refrigerant evaporator in the pump cycle operation, The refrigerant R mixed with the liquid phase is sucked into the compressor 4 in accordance with the switching to the compressor cycle operation, so that a so-called liquid back is generated, which causes damage to the compressor 4.

  This problem is unavoidable particularly when the load-side heat exchanger 2 is caused to function as a wet refrigerant evaporator without performing superheat control in the pump cycle operation.

  On the other hand, when the pump cycle operation is changed from the normal mode to the superheat degree securing mode as described above prior to switching to the compressor cycle operation, as shown schematically by the arrow yy ′ in FIG. The superheat degree SH ′ of the refrigerant R delivered from the load-side heat exchanger 2 can be ensured prior to switching to the compressor cycle operation (that is, only the gas-phase refrigerant R is delivered). Thereby, what is called a liquid back can be prevented and damage to the compressor 4 can be prevented.

  FIG. 11 shows an experimental result when the pump cycle operation is switched to the compressor cycle operation by stopping the refrigerant pump 8, starting the compressor 4, and switching the refrigerant path at the same timing.

  As can be seen from FIG. 11, in this cooling device C, the load is also changed when the pump cycle operation is switched to the compressor cycle operation as in the case of switching from the compressor cycle operation to the pump cycle operation (see FIG. 8). Although the outlet air temperature of the side heat exchanger 2 (that is, the temperature of the load side air IA after cooling sent from the load side heat exchanger 2) slightly rises, it quickly returns to the original temperature within a few minutes. Therefore, generally good continuity is ensured for the cooling of the load-side air IA in the load-side heat exchanger 2.

  Further, the degree of superheat SH of the refrigerant R at the refrigerant outlet of the load-side heat exchanger 2 as the refrigerant evaporator is also secured (SH ≧ SHm), thereby preventing liquid back to the compressor 4.

  As shown in FIG. 5, when the controller 15 switches from the pump cycle operation to the compressor cycle operation under the execution of the superheat degree securing mode, thereafter, until the set transient time Tc of about several minutes elapses, A stabilization mode is executed in which the drive frequency of the compressor 4 is held at the set limit frequency, and the opening of the expansion valve 10 and the opening of the evaporation pressure adjusting valve 3 are held at the set limit opening.

  That is, when the superheat degree securing mode is performed and the flow rate of the refrigerant R is reduced to increase the superheat degree SH ′ at the refrigerant outlet of the load-side heat exchanger 2 and the compressor cycle operation is switched to the compressor cycle operation. A. Superheat control, b. Compressor suction pressure control, c. When the cooling capacity control is started immediately, the superheat degree SH suddenly changes toward the set superheat degree SHs, and the suction pressure ps of the compressor 4 also changes suddenly toward the set suction pressure pss. Due to these sudden changes, the superheat degree SH As the suction pressure ps fluctuates and the cooling capacity Q fluctuates, the compressor cycle operation becomes unstable even temporarily.

  On the other hand, by implementing the stabilization mode immediately after switching to compressor cycle operation, it is possible to prevent instability of the compressor cycle operation as described above, and to stabilize compressor cycle operation immediately after switching. Can be

  As described above, the controller 15 determines whether or not the switching from the compressor cycle operation to the pump cycle operation is appropriate, and whether or not the switching from the pump cycle operation to the compressor cycle operation is appropriate. Switching between the cycle operation and the pump cycle operation is performed. In the pump cycle operation, the controller 15 basically performs the compressor cycle based on the measured value of the condensation pressure pc ′ of the refrigerant R in the outside air heat exchanger 5. Switching to operation (that is, switching to compressor cycle operation after pump cycle operation in the superheat degree securing mode) is determined.

  Further, the controller 15 reduces the temperature of the outside air OA during the compressor cycle operation, and the d. In a situation where the condensation pressure pc is maintained at the set lower limit pcmin by the outside air flow control, the pump is basically based on the output of the outside air fan 13 (in other words, the amount of ventilation fo of the outside air OA to the outside air heat exchanger 5). Decide to switch to cycle operation.

  Specifically, in the pump cycle operation, as shown in FIG. 12, when the measured condensation pressure pc ′ of the refrigerant R in the outside air heat exchanger 5 becomes higher than the set upper limit value pcmax ′ (pc ′> pcmax ′), Alternatively, when the load heat quantity q (required cooling amount) of the load side air IA becomes larger than the preset maximum cooling capacity Qmax in the pump cycle operation (q> Qmax), the controller 15 starts from the pump cycle operation. It is determined that the switching to the compressor cycle operation is appropriate, and the switching to the compressor cycle operation through the pump cycle operation in the superheat degree securing mode is executed.

  On the other hand, regarding the switching from the compressor cycle operation to the pump cycle operation, as shown in FIG. 13, the condensing pressure pc of the refrigerant R in the outside air heat exchanger 5 is maintained at the set lower limit pcmin by the outside air volume control. In the three-way correlation of the output of the outside air fan 13 (in this case, the outside air flow rate fo), the cooling capacity Q, and the outside air temperature to, the pump cycle operation region D1 defined by the boundary line L1 (below the boundary line L1) Are set in advance based on experiments and trial runs.

  In the compressor cycle operation, as shown in FIG. 14, the state points (q, fo) having the measured load heat quantity q and the measured outside air flow rate fo at the respective time points as coordinate values enter the pump cycle operation region D1. When (q, fo ∈ D1), the controller 15 determines that switching from the compressor cycle operation to the pump cycle operation is appropriate, and executes the switch to the pump cycle operation.

  In FIG. 13, the □ line, the Δ line, and the ◯ line are correlation lines between the outside air flow rate fo and the cooling capacity Q when the outside air temperature to is 15 ° C., 10 ° C., and 5 ° C., respectively.

  In FIG. 13, a region D2 (region below the boundary line L2) defined by the boundary line L2 is a region where pump cycle operation is possible, and a region between the boundary line L1 and the boundary line L2 is a pump. The dead zone region prevents hunting switching between cycle operation and compressor cycle operation.

  That is, in the pump cycle operation in which the condensing pressure pc ′ of the refrigerant R in the outdoor air heat exchanger 5 is the result, as shown in FIG. 15, the refrigerant R in the outdoor air heat exchanger 5 is at a certain time outside air temperature to. The condensation pressure pc ′ varies depending on whether the heat transfer surface in the outside air heat exchanger 5 is normal, dirty with dust or the like, or wet with rain or the like.

  For this reason, when the switching determination between the compression cycle operation and the pump cycle operation is performed based on only the outside air temperature to as in the conventional case, when the heat transfer surface in the outside air heat exchanger 5 is dirty, the condensation pressure is higher than usual. There is a possibility that switching from the pump cycle operation to the compressor cycle operation may be performed in a situation where pc ′ is increased and the cooling capacity Q is already insufficient.

  On the other hand, when the heat transfer surface in the outside air heat exchanger 5 is wet, condensing pressure pc 'is not increased more than usual, and the cooling capacity Q still has a margin in the cooling cycle Q. There is a risk of switching to cycle operation.

  On the other hand, when the measured condensing pressure pc ′ of the refrigerant R in the outside air heat exchanger 5 becomes larger than the set upper limit value pcmax ′ (pc ′> pcmax ′) as described above, the pump cycle operation is changed to the compressor cycle operation. By determining that the switching is appropriate, the pump is always at an appropriate timing, regardless of the contamination or wetting of the heat transfer surface in the outside air heat exchanger 5, as compared with the conventional method using only the outside air temperature to as the switching reference. It is possible to switch from cycle operation to compressor cycle operation.

  FIG. 16 shows the experimental results when switching from the pump cycle operation to the compressor cycle operation based on the measured condensation pressure pc ′ of the refrigerant R in the outside air heat exchanger 5 as described above. As can be seen from FIG. 16, in the pump cycle operation, the measured condensation pressure pc ′ of the refrigerant R in the outside air heat exchanger 5 increases as the outside air temperature to rises. When the measured condensing pressure pc ′ exceeds the set upper limit value pcmax ′ due to the increase, switching to the compressor cycle operation through the pump cycle operation in the superheat degree securing mode is performed.

  In the cooling device C, as shown in FIG. 12 described above, even when the measured condensation pressure pc ′ of the refrigerant R in the outdoor air heat exchanger 5 is equal to or lower than the set upper limit value pcmax ′ (pc ′ ≦ pcmax ′) When the heat quantity q (necessary cooling amount) exceeds the preset maximum cooling capacity Qmax in the pump cycle operation (q> Qmax), switching to the compressor cycle operation through the pump cycle operation in the superheat degree securing mode However, depending on the use conditions of the cooling device C, such as when the load heat quantity q of the load side air IA is relatively stable and does not increase greatly during the pump cycle operation, the outside air heat exchanger 5 Based on only the measured condensing pressure pc ′ of the refrigerant R in the engine, the operation is switched to the compressor cycle operation after the pump cycle operation in the superheat degree securing mode. It may be.

  On the other hand, FIG. 17 shows that the above-mentioned d. The outside air flow rate fo and the cooling capacity Q by the outside air fan 13 and the heat transfer in the outside air heat exchanger 5 when the condensation pressure pc of the refrigerant R in the outside air heat exchanger 5 is maintained at the set lower limit value pcmin by the outside air volume control. The correlation with the surface state is shown.

  As can be seen from FIG. 17, in the situation where the condensation pressure pc of the refrigerant R in the outside air heat exchanger 5 is maintained at the set lower limit pcmin by adjusting the outside air flow rate fo in the compressor cycle operation, the outside temperature to is constant. However, the cooling capacity Q with respect to the outside air flow rate fo at a certain point of time varies depending on whether the heat transfer surface in the outside air heat exchanger 5 is normal, dirty with dust, or wet with rain or the like. .

  For this reason, if the switching between the compressor cycle operation and the pump cycle operation is performed based only on the outside air temperature to as in the past, if the heat transfer surface in the outside air heat exchanger 5 is dirty, the pump cycle operation is still not performed. There is a possibility that switching from the compressor cycle operation to the pump cycle operation may be performed in a situation where the load heat quantity q of the load side air IA cannot be processed yet.

  On the other hand, when the heat transfer surface in the outside air heat exchanger 5 is wet, the load heat quantity q of the load side air IA can be sufficiently processed even in the pump cycle operation. There is a risk that switching to cycle operation will not be performed.

  On the other hand, when the state point (q, fo) having the measured load heat quantity q and the measured outside air flow rate fo as coordinate values enters the preset pump cycle operation region D1 (q, fo ∈ D1) as described above. By switching from the compressor cycle operation to the pump cycle operation, compared to the conventional method using only the outside air temperature to as a reference for switching, the heat transfer surface in the outside air heat exchanger 5 is always maintained regardless of contamination or wetting. The compressor cycle operation can be switched to the pump cycle operation at an appropriate timing.

  In FIG. 18, as described above, switching from the compressor cycle operation to the pump cycle operation is performed based on the position of the state point (q, fo) having the measured load heat quantity q and the measured outside air flow rate fo as coordinate values. FIG. 18 shows the experimental results in the case where the external air fan 13 is used to keep the condensation pressure pc of the refrigerant R in the outdoor air heat exchanger 5 at the set lower limit value pcmin in the compressor cycle operation. In the situation where the ventilation rate fo is adjusted, the outside air ventilation fo decreases as the outside air temperature to decreases. The state point (q, fo) having the measured load heat quantity q and the measured outside air ventilation quantity fo as coordinate values enters the preset pump cycle operation region D1 due to the decrease in the outside air ventilation quantity fo (q, fo∈). D1) At the time, switching from the compressor cycle operation to the pump cycle operation is performed.

  In the above example, the controller 15 performs the pump operation in the superheat degree securing mode when the measured condensing pressure pc ′ of the refrigerant R in the outside air heat exchanger 5 becomes larger than the set upper limit value pcmax ′ (pc ′> pcmax ′). It is determined that switching to the compressor cycle operation through the cycle operation is appropriate, and the switch from the pump cycle operation to the compressor cycle operation is performed. Instead, the controller 15 performs the pump cycle operation. The switching determination from the compressor operation to the compressor operation may be performed as follows.

  As shown in FIG. 19, in the pump cycle operation, each of the condensation pressure pc ′ of the refrigerant R in the outdoor air heat exchanger 5 and the evaporation pressure pe ′ of the refrigerant R in the load-side heat exchanger 2 and the cooling of the cooling device C are performed. There is a correlation that can be expressed by a specific relational expression (for example, Expression 1 or Expression 2 in the figure) between the capacity Q (that is, the cooling amount of the load side air IA in the load side heat exchanger 2). is there.

  From this, the condensing pressure pc ′ of the refrigerant R in the outside air heat exchanger 5 or the evaporating pressure pe ′ of the refrigerant R in the load side heat exchanger 2 is measured, and the cooling capacity Q corresponding to the measured value (that is, its The controller 15 is made to calculate the cooling capacity in the pump cycle operation at the time point).

  Then, as shown in FIG. 20, the calculated cooling capacity Q is sequentially set as the determination cooling capacity Qs, while the load heat quantity q (that is, the required cooling amount) is determined from the determination cooling capacity Qs at that time. When it becomes large, it is determined that switching from the pump cycle operation to the compressor cycle operation is appropriate, and the switching to the compressor cycle operation through the pump cycle operation in the superheat degree securing mode is performed, After the switching, the controller 15 may be configured to perform the compressor cycle operation in the stabilization mode during the set transient time Tc.

  That is, even when the controller 15 is configured as described above, the timing is always appropriate regardless of the contamination or wetting of the heat transfer surface in the outdoor air heat exchanger 5 as compared with the conventional method in which only the outside air temperature to is used as a reference. Can switch from pump cycle operation to compressor cycle operation.

  In the above example, the cooling device C that cools the load side air IA as the load medium by the load side heat exchanger 2 is shown. However, the present invention is a load medium that cools various gases by the load side heat exchanger 2. The load medium for cooling various liquids such as water by the load-side heat exchanger 2 or the load medium for cooling various solids such as articles and raw materials by the load-side heat exchanger 2 is not limited thereto. It can also be applied to cases.

  The compressor / pump switching type cooling device according to the present invention can be used to cool various load media in various fields.

8 Refrigerant pump 4 Compressor 5 Outside air heat exchanger 10 Expansion valve 2 Load side heat exchanger R Refrigerant 1 Refrigerant circuit CW Cooling heat medium 7 Refrigerant cooler 15 Controller SH Superheat SHm Setting allowable value Tc Setting transient time

Claims (3)

Compressor cycle operation in which the refrigerant is circulated by the compressor in the order of the compressor, the outside air heat exchanger, the expansion valve, and the load side heat exchanger in a state of bypassing the stopped refrigerant pump,
Refrigerant circulation capable of switching between pump cycle operation in which refrigerant is circulated by the refrigerant pump in the order of the refrigerant pump, the load-side heat exchanger, and the outside air heat exchanger in a state in which the stopped compressor is bypassed. Set up a road,
In the compressor cycle operation, heat is radiated to the outside air by condensing the refrigerant in the outside air heat exchanger, and in parallel with this, the load medium is cooled by evaporating the refrigerant in the load side heat exchanger,
In the pump cycle operation, the refrigerant exchanges heat with the low-temperature outside air in the outside heat exchanger to cool and condense the refrigerant and dissipate heat to the outside air. In parallel with this, the refrigerant in the load-side heat exchanger The compressor / pump switching type cooling device that heats and evaporates the refrigerant and cools the load medium by exchanging heat with the load medium,
In the pump cycle operation, a refrigerant cooler that cools the refrigerant sucked by the refrigerant pump by exchanging heat with a cooling heat medium from the outside air heat exchanger in the refrigerant circulation path to the refrigerant pump in the refrigerant flow direction. Intervening in the middle of the part ,
A controller for performing switching between the compressor cycle operation and the pump cycle operation;
When the controller switches from the pump cycle operation to the compressor cycle operation, the controller reduces the output of the refrigerant pump, thereby increasing the superheat degree of the refrigerant at the refrigerant outlet of the load side heat exchanger. Performing the pump cycle operation,
In the pump cycle operation in this superheat degree securing mode, when the superheat degree of the refrigerant at the refrigerant outlet of the load side heat exchanger rises to a set allowable value or when a set time has elapsed, the pump cycle A compressor / pump switching type cooling device configured to perform switching from operation to the compressor cycle operation . In the switching between the compressor cycle operation and the pump cycle operation, the controller starts and stops the compressor, starts and stops the refrigerant pump, and switches the refrigerant path in the refrigerant circuit. The compressor / pump switching type cooling device according to claim 1, wherein the cooling device is configured to perform at substantially the same timing. The controller, after switching from the pump cycle operation to the compressor cycle operation, limits the output of the compressor and sets the opening of the expansion valve to a set limit opening until a set transient time elapses. The compressor cycle operation is performed in the holding stabilization mode,
The compressor / pump switching type cooling device according to claim 1 or 2, wherein the stabilization mode in the compressor cycle operation is canceled when the set transient time has elapsed .

Images