JP2024078026A - Vapor compression type refrigeration cycle device - Google Patents

Abstract

To provide a vapor compression type refrigeration cycle device capable of increasing a discharge temperature in a short time after operation start of a compressor to reduce an amount of refrigerant dissolved in compressor lubricating oil, when the amount of refrigerant dissolved in the oil.SOLUTION: A vapor compression type refrigeration cycle device of the present invention comprises a main refrigerant circuit 10, a bypass refrigerant circuit 20, and a control device 50. The control device 50 has a compressor activation mode. In the compressor activation mode, the control device controls a first expansion device 14 and a second expansion device 21 so that a refrigerant flows through both the main refrigerant circuit 10 and the bypass refrigerant circuit 20 for a predetermined period from the start of operation of the compressor 11.SELECTED DRAWING: Figure 1

Description

The present invention relates to a vapor compression refrigeration cycle device.

Patent Document 1 proposes a protection and control device for an air conditioner that controls the compressor operating frequency according to the discharge temperature, thereby reducing the foaming phenomenon caused by a sudden drop in low pressure. This reduces the discharge of compressor lubricating oil outside the compressor, ensuring the reliability of the compressor.

Japanese Patent Application Laid-Open No. 7-190509

However, when the outside air temperature is low and the system has been shut down for an extended period of time, the compressor is cold and the amount of refrigerant dissolved in the compressor lubricating oil increases.
In this way, when the amount of refrigerant dissolving in the compressor lubricating oil increases, the amount of refrigerant circulating in the refrigeration cycle decreases, the low pressure inside the compressor drops, and there is a risk of compromising the reliability of the compressor.

The present invention aims to provide a vapor compression refrigeration cycle device that can increase the discharge temperature in a short time after the compressor starts operating and reduce the amount of refrigerant that dissolves in the oil when the amount of refrigerant that dissolves in the compressor lubricating oil is increasing.

The vapor compression refrigeration cycle apparatus of the present invention described in claim 1 comprises: a main refrigerant circuit 10 formed by sequentially connecting a compressor 11, a utilization side heat exchanger 12, an intermediate heat exchanger 13, a first expansion device 14, and a heat source side heat exchanger 15 with a refrigerant piping 16; a bypass refrigerant circuit 20 branched from the refrigerant piping 16 between the utilization side heat exchanger 12 and the first expansion device 14 and sequentially connected to a second expansion device 21, the intermediate heat exchanger 13, and the compressor 11 during compression; and a control device 50 for controlling valve openings of the first expansion device 14 and the second expansion device 21, wherein the control device 50 has a compressor start-up mode, and in the compressor start-up mode, the control device 50 controls the first expansion device 14 and the second expansion device 21 so that refrigerant flows through both the main refrigerant circuit 10 and the bypass refrigerant circuit 20 for a predetermined period from the start of operation of the compressor 11.
The present invention described in claim 2 is characterized in that, in the vapor compression refrigeration cycle apparatus described in claim 1, in the compressor start-up mode, the second expansion device 21 is controlled so that the dryness of the refrigerant on the outlet side of the intermediate heat exchanger 13 in the bypass refrigerant circuit 20 becomes a predetermined value or higher.
The present invention as described in claim 3 is characterized in that, in the vapor compression refrigeration cycle apparatus as described in claim 1, in the compressor start-up mode, the flow rate of the use-side heat medium flowing through the use-side heat exchanger 12 is set to a predetermined value or less, or the use-side heat medium is not flowed through the use-side heat exchanger.
The present invention described in claim 4 is characterized in that, in the vapor compression refrigeration cycle apparatus described in any one of claims 1 to 3, the control device 50 performs the compressor start-up mode when the temperature of the compressor 11 is lower than a set temperature.
The present invention as set forth in claim 5 is characterized in that, in the vapor compression refrigeration cycle apparatus as set forth in any one of claims 1 to 3, the control device 50 terminates the compressor start-up mode when the discharge superheat of the compressor 11 becomes equal to or greater than a predetermined value, when the suction superheat of the compressor 11 becomes equal to or less than a predetermined value, or when the suction pressure of the compressor 11 becomes positive pressure.

According to the present invention, in the compressor start-up mode, the amount of refrigerant flowing into the compressor is increased, thereby increasing the workload of the compressor and raising the discharge temperature in a short period of time. Furthermore, by raising the discharge temperature, the amount of refrigerant dissolved in the oil can be reduced, so that the viscosity of the oil is not reduced, wear on the machinery inside the compressor can be suppressed, and the reliability of the compressor can be ensured. In addition, the amount of oil discharged from the compressor can be reduced to prevent a decrease in the heat exchange rate of the heat exchanger.

FIG. 1 is a block diagram of a vapor compression refrigeration cycle device according to an embodiment of the present invention. Control flow of the vapor compression refrigeration cycle device according to this embodiment Graph showing the relationship between injection ratio and injection temperature or discharge temperature Graph showing the relationship between oil temperature and pressure and refrigerant solubility Graph showing compressor condition after start-up when cold

In the vapor compression refrigeration cycle device according to the first embodiment of the present invention, the control device has a compressor start mode, and in the compressor start mode, the first expansion device and the second expansion device are controlled so that the refrigerant flows through both the main refrigerant circuit and the bypass refrigerant circuit for a predetermined period from the start of operation of the compressor. According to this embodiment, by opening the first expansion device, the suction density of the compressor increases and the amount of refrigerant flowing into the compressor increases. Also, by opening the second expansion device, the amount of refrigerant injected into the compressor increases. In this way, in the compressor start mode, the amount of refrigerant flowing into the compressor is increased, thereby increasing the workload of the compressor and raising the discharge temperature in a short time. And by raising the discharge temperature, the amount of refrigerant dissolved in the oil can be reduced, thereby improving the reliability of the compressor. Also, by reducing the amount of oil discharged from the compressor, a decrease in the heat exchange rate of the heat exchanger can be prevented.

The second embodiment of the present invention is a vapor compression refrigeration cycle device according to the first embodiment, in which in the compressor start-up mode, the second expansion device is controlled so that the dryness of the refrigerant on the outlet side of the intermediate heat exchanger in the bypass refrigerant circuit is equal to or higher than a predetermined value. According to this embodiment, the temperature of the refrigerant injected into the compressor can be increased, and the discharge temperature of the refrigerant discharged from the compressor can be increased in a short period of time.

In the third embodiment of the present invention, in the vapor compression refrigeration cycle device according to the first embodiment, in the compressor start-up mode, the flow rate of the use-side heat medium flowing through the use-side heat exchanger is set to a predetermined value or less, or the use-side heat medium is not flowed through the use-side heat exchanger. According to this embodiment, by not lowering the temperature of the refrigerant flowing out of the use-side heat exchanger, it is possible to increase the temperature of the refrigerant sucked into the compressor and also to increase the temperature of the refrigerant injected, and it is possible to increase the discharge temperature of the refrigerant discharged from the compressor in a short period of time.

The fourth embodiment of the present invention is a vapor compression refrigeration cycle device according to any one of the first to third embodiments, in which the control device performs the compressor start mode when the compressor temperature is lower than the set temperature. According to this embodiment, the compressor start mode can be performed when a large amount of refrigerant has dissolved in the oil.

In the fifth embodiment of the present invention, in the vapor compression refrigeration cycle device according to any one of the first to third embodiments, the control device ends the compressor start-up mode when the compressor discharge superheat is equal to or greater than a predetermined value, the compressor suction superheat is equal to or less than a predetermined value, or the compressor suction pressure becomes positive. According to this embodiment, the compressor start-up mode can be ended when the amount of refrigerant dissolved in the oil has decreased.

An embodiment of the present invention will now be described with reference to the drawings.
1 is a block diagram of a vapor compression refrigeration cycle apparatus according to the present embodiment. The vapor compression refrigeration cycle apparatus is composed of a main refrigerant circuit 10 and a bypass refrigerant circuit 20.
The main refrigerant circuit 10 is formed by sequentially connecting a compressor 11 that compresses the refrigerant, a utilization side heat exchanger 12 that functions as a radiator, an intermediate heat exchanger 13 that functions as an economizer, a first expansion device 14 that is a main expansion valve, and a heat source side heat exchanger 15 that functions as an evaporator with refrigerant piping 16.
As shown in the figure, the vapor compression refrigeration cycle apparatus may include a four-way valve 17 between the compressor 11 and the utilization side heat exchanger 12. The four-way valve 17 can change the direction of the refrigerant flowing through the main refrigerant circuit 10. That is, by switching the four-way valve 17, the refrigerant discharged from the compressor 11 flows through the heat source side heat exchanger 15, the first expansion device 14, the intermediate heat exchanger 13, and the utilization side heat exchanger 12 in this order, and is then drawn into the compressor 11. In this case, the heat source side heat exchanger 15 functions as a radiator, and the utilization side heat exchanger 12 functions as an evaporator.

The bypass refrigerant circuit 20 branches off from the refrigerant pipe 16 between the utilization side heat exchanger 12 and the first expansion device 14 , and is connected to a compression chamber located midway through compression in the compressor 11 .
The bypass refrigerant circuit 20 is provided with a second expansion device 21. A portion of the high-pressure refrigerant after passing through the user-side heat exchanger 12, or a portion of the high-pressure refrigerant after passing through the intermediate heat exchanger 13 is decompressed by the second expansion device 21 to become an intermediate-pressure refrigerant, and then exchanges heat with the high-pressure refrigerant flowing through the main refrigerant circuit 10 in the intermediate heat exchanger 13 and is injected into the compressor 11. The refrigerant injected into the compressor 11 merges with the refrigerant being compressed by the compressor 11.
In the compressor 11, the injected refrigerant and the refrigerant being compressed are joined together to perform recompression.

The use-side heat medium circuit 30 is formed by connecting the use-side heat exchanger 12, a conveying pump 31, a heating terminal (not shown), and a hot water tank (not shown) by heat medium piping 32. The use-side heat medium flowing through the use-side heat medium circuit 30 can be water or antifreeze liquid.
The utilization side heat exchanger 12 heats the utilization side heat medium with the refrigerant discharged from the compressor 11 .
The use-side heat medium heated in the use-side heat exchanger 12 is radiated at a heating terminal and used for heating, and the use-side heat medium radiated at the heating terminal and cooled is heated again in the use-side heat exchanger 12.
In addition, the use-side heat medium heated in the use-side heat exchanger 12 is introduced into the hot water storage tank from the top of the hot water storage tank, and low-temperature use-side heat medium is discharged from the bottom of the hot water storage tank and heated in the use-side heat exchanger 12.

The high-pressure refrigerant discharged from the compressor 11 dissipates heat in the user-side heat exchanger 12, then branches off from the main refrigerant circuit 10, and is reduced in pressure to an intermediate pressure by the second expansion device 21 to become an intermediate-pressure refrigerant, which then undergoes heat exchange in the intermediate heat exchanger 13.
The high-pressure refrigerant flowing through the main refrigerant circuit 10 after dissipating heat in the user-side heat exchanger 12 is cooled by the intermediate-pressure refrigerant flowing through the bypass refrigerant circuit 20, and is decompressed in the first expansion device 14 with its enthalpy reduced.
The refrigerant decompressed in the first expansion device 14 has a reduced refrigerant dryness (the weight ratio of the gas phase components to the total refrigerant) when it flows into the heat source side heat exchanger 15, and the liquid component of the refrigerant has increased, so the refrigerant evaporates in the heat source side heat exchanger 15 and returns to the suction side of the compressor 11.
On the other hand, the intermediate-pressure refrigerant whose pressure has been reduced to an intermediate pressure by the second expansion device 21 is heated by the high-pressure refrigerant flowing through the main refrigerant circuit 10 in the intermediate heat exchanger 13, and then joins the refrigerant being compressed in the compressor 11 with its refrigerant enthalpy increased.

The compressor 11 is provided with a compressor temperature sensor 41 that detects the temperature of the compressor 11 .
In addition, a refrigerant discharge temperature sensor 42 is provided on the refrigerant pipe 16 on the discharge side of the compressor 11. The refrigerant discharge temperature sensor 42 detects the refrigerant discharge temperature of the refrigerant discharged from the compressor 11.
The refrigerant pipe 16 on the suction side of the compressor 11 is provided with a refrigerant suction pressure detection means 43. The refrigerant suction pressure detection means 43 detects the suction pressure of the refrigerant sucked into the compressor 11.
An injection refrigerant temperature sensor 44 is provided in the bypass piping 22 on the outlet side of the intermediate heat exchanger 13 in the bypass refrigerant circuit 20. The injection refrigerant temperature sensor 44 detects the temperature of the refrigerant injected into the compressor 11.

The vapor compression refrigeration cycle apparatus according to this embodiment includes a control device 50 that controls the valve opening degree of the first expansion device 14 and the second expansion device 21. The control device 50 also controls the rotation speed of the conveying pump 31. By controlling the rotation speed of the conveying pump 31, the flow rate of the use-side heat medium flowing through the use-side heat exchanger 12 can be changed.
The control device 50 has a compressor start-up mode. In the compressor start-up mode, the control device 50 controls the first expansion device 14 and the second expansion device 21 so that refrigerant flows through both the main refrigerant circuit 10 and the bypass refrigerant circuit 20 for a predetermined period from the start of operation of the compressor 11.
The control device 50 performs the compressor start-up mode when the temperature of the compressor 11 detected by the compressor temperature sensor 41 is lower than the set temperature Ts. In this way, by performing the compressor start-up mode when the temperature of the compressor 11 is lower than the set temperature Ts, the compressor start-up mode can be performed in a state where a large amount of refrigerant has dissolved into the oil.
In addition, in the compressor start-up mode, the control device 50 estimates the dryness fraction of the refrigerant on the outlet side of the intermediate heat exchanger 13 in the bypass refrigerant circuit 20 from the refrigerant temperature Ti detected by the injection refrigerant temperature sensor 44, and controls the second expansion device 21 so that the dryness fraction becomes a predetermined value or more. Therefore, the temperature of the refrigerant injected into the compressor 11 can be increased, and the discharge temperature of the refrigerant discharged from the compressor 11 can be increased in a short time.
Furthermore, in the compressor start-up mode, the control device 50 controls the rotation speed of the conveying pump 31 to set the flow rate of the use-side heat medium flowing through the use-side heat exchanger 12 to a predetermined value or less, or does not allow the use-side heat medium to flow through the use-side heat exchanger. Therefore, since the temperature of the refrigerant flowing out of the use-side heat exchanger 12 is not lowered, the temperature of the refrigerant sucked into the compressor 11 can be increased, and the temperature of the refrigerant injected can also be increased, so that the discharge temperature of the refrigerant discharged from the compressor 11 can be increased in a short period of time.
The control device 50 also ends the compressor start-up mode when the discharge superheat of the compressor 11 becomes equal to or higher than a predetermined value based on the refrigerant discharge temperature detected by the refrigerant discharge temperature sensor 42, the suction superheat of the compressor 11 becomes equal to or lower than a predetermined value, or the suction pressure of the compressor 11 detected by the refrigerant suction pressure detection means 43 becomes positive. Therefore, the compressor start-up mode can be ended in a state where the amount of refrigerant dissolved in the oil has decreased.

FIG. 2 is a control flow of the vapor compression refrigeration cycle device according to this embodiment.
If the temperature of the compressor 11 detected by the compressor temperature sensor 41 is lower than the set temperature Ts (Yes in S1), the control device 50 executes the compressor start-up mode.
If the temperature of the compressor 11 is lower than the set temperature Ts (Yes in S1), the valve opening of the second expansion device 21 is increased (S2), causing refrigerant to circulate through both the main refrigerant circuit 10 and the bypass refrigerant circuit 20.
If the temperature of the compressor 11 detected by the compressor temperature sensor 41 is equal to or higher than the set temperature Ts (No in S1), the control device 50 does not execute the compressor start-up mode.

If the refrigerant temperature Ti detected by the injection refrigerant temperature sensor 44 is equal to or higher than a predetermined injection superheat (Yes in S3), the control device 50 further increases the valve opening of the second expansion device 21 (S4).
If the refrigerant temperature Ti detected by the injection refrigerant temperature sensor 44 falls below a predetermined injection superheat (No in S3), the control device 50 reduces the valve opening of the second expansion device 21 (S5).

When the suction pressure of the compressor 11 detected by the refrigerant suction pressure detection means 43 becomes positive (No in S6), the control device 50 sets the valve opening of the second expansion device 21 to zero, i.e., closes the second expansion device 21 (S7), and terminates the compressor start-up mode.
If the suction pressure of the compressor 11 detected by the refrigerant suction pressure detection means 43 is negative pressure (Yes in S6), the control device 50 controls the valve opening of the second expansion device 21 to ensure a specified injection superheat (S4, S5).
The compressor start mode may be terminated on the condition that the discharge superheat of the compressor 11 becomes equal to or greater than a predetermined value, instead of or in addition to the suction pressure of the compressor 11.
In addition, the compressor start mode may be terminated on the condition that the suction superheat of the compressor 11 becomes equal to or lower than a predetermined value instead of or in addition to the suction pressure of the compressor 11 .

Although not shown in FIG. 2, in the compressor start mode, the rotation speed of the conveying pump 31 is controlled to stop or set the flow rate of the utilization side heat medium flowing through the utilization side heat exchanger 12 to a predetermined value or less, thereby increasing the temperature of the refrigerant sucked into the compressor 11 and also increasing the temperature of the refrigerant injected.

FIG. 3(a) is a graph showing the relationship between the injection amount of refrigerant and the injection temperature, and FIG. 3(b) is a graph showing the relationship between the injection amount of refrigerant and the discharge temperature and the injection superheat.
As shown in FIG. 3A, when the injection amount of the refrigerant from the bypass refrigerant circuit 20 increases (the injection ratio increases), the injection wetness increases and the injection temperature decreases as the heat exchange amount in the intermediate heat exchanger 13 increases.
As shown in FIG. 3B, the refrigerant discharge temperature discharged from the compressor 11 increases when the injection amount is small, but decreases as the injection amount increases (injection ratio increases).
3B, the discharge superheat increases as the refrigerant discharge temperature discharged from the compressor 11 increases, and the discharge superheat decreases as the refrigerant discharge temperature discharged from the compressor 11 decreases. In this way, by increasing the injection amount, the degree of subcooling can be increased and the heating capacity can be improved, but if the injection superheat cannot be secured, the refrigerant discharge temperature decreases.

4 is a graph showing the relationship between the oil temperature and pressure and the solubility of the refrigerant when the solubility of the refrigerant is 10%, 20%, 30%, and 100%.
A solubility of 100% is when the refrigerant is saturated, and as shown in Figure 4, the amount of refrigerant dissolved in the oil increases as the oil temperature decreases. Therefore, the solubility of the refrigerant in the oil decreases by increasing the oil temperature. In other words, the amount of refrigerant dissolved in the oil can be reduced by increasing the discharge superheat.

FIG. 5 shows a state after startup when the outside air temperature is low and operation has been stopped for a long period of time, and the compressor is cold.
FIG. 5(a) shows the amount of refrigerant dissolved in the compressor lubricating oil, indicating that the solubility is high at the time of startup.
The compressor 11 is then started up with the refrigerant in the lubricating oil, and the refrigerant is then discharged from the compressor 11. The refrigerant is then discharged from the compressor 11. The refrigerant is then discharged from the compressor 11. The refrigerant is then discharged from the compressor 11.
Fig. 5(c) shows the discharge temperature and suction temperature when the compressor 11 is started in a state where the solubility is high. As shown in Fig. 5(c), the suction temperature does not rise easily, and it takes time for the discharge temperature to rise.
Fig. 5(d) shows the state of the suction superheat of the compressor 11 when the compressor 11 is started in a state where the solubility is high. As shown in Fig. 5(d), when the solubility is high, the suction superheat rises rapidly immediately after the start, but when the solubility decreases with the temperature rise of the compressor 11 and the refrigerant starts to dissolve, the suction superheat decreases.

In this embodiment, by opening the first expansion device 14, the suction density of the compressor 11 is increased to increase the amount of refrigerant flowing into the compressor 11, and by opening the second expansion device 21, the amount of refrigerant injected into the compressor 11 is increased. In this way, in the compressor start-up mode, by increasing the amount of refrigerant flowing into the compressor 11, the workload of the compressor 11 is increased and the discharge temperature can be increased in a short time. In addition, by increasing the discharge temperature, the amount of refrigerant dissolved in the oil can be reduced, thereby improving the reliability of the compressor 11. In addition, by reducing the amount of oil discharged from the compressor 11, a decrease in the heat exchange rate of the heat exchanger can be prevented.

As described above, the discharge temperature can be increased in a short time after the compressor starts operating.

REFERENCE SIGNS LIST 10 Main refrigerant circuit 11 Compressor 12 Use side heat exchanger 13 Intermediate heat exchanger 14 First expansion device 15 Heat source side heat exchanger 16 Refrigerant piping 17 Four-way valve 20 Bypass refrigerant circuit 21 Second expansion device 22 Bypass piping 30 Use side heat medium circuit 31 Conveyor pump 32 Heat medium piping 41 Compressor temperature sensor 42 Refrigerant discharge temperature sensor 43 Refrigerant suction pressure detection means 44 Injection refrigerant temperature sensor 50 Control device

Claims (5)

a main refrigerant circuit formed by sequentially connecting a compressor, a utilization side heat exchanger, an intermediate heat exchanger, a first expansion device, and a heat source side heat exchanger by refrigerant piping;
a bypass refrigerant circuit that is branched off from the refrigerant piping between the utilization side heat exchanger and the first expansion device, and is sequentially connected to a second expansion device, the intermediate heat exchanger, and a portion of the compressor that is in the middle of compression;
a control device for controlling valve opening degrees of the first expansion device and the second expansion device;
Equipped with
The control device has a compressor start mode,
a first expansion device that controls the second expansion device so that refrigerant flows through both the main refrigerant circuit and the bypass refrigerant circuit for a predetermined period of time from the start of operation of the compressor, the first expansion device and the second expansion device being controlled. 2. The vapor compression refrigeration cycle apparatus according to claim 1, wherein in the compressor start-up mode, the second expansion device is controlled so that the dryness of the refrigerant on an outlet side of the intermediate heat exchanger in the bypass refrigerant circuit becomes equal to or higher than a predetermined value. 2. The vapor compression refrigeration cycle apparatus according to claim 1, wherein, in the compressor start-up mode, a flow rate of the use-side heat medium flowing through the use-side heat exchanger is set to a predetermined value or less, or the use-side heat medium is not flowed through the use-side heat exchanger. 4. The vapor compression refrigeration cycle apparatus according to claim 1, wherein the control device performs the compressor start-up mode when a temperature of the compressor is lower than a set temperature. 4. The vapor compression refrigeration cycle apparatus according to claim 1, wherein the control device terminates the compressor start-up mode when a discharge superheat of the compressor becomes equal to or greater than a predetermined value, when a suction superheat of the compressor becomes equal to or less than a predetermined value, or when a suction pressure of the compressor becomes positive.