JP2018096621A - Refrigerant circuit system and process of control for refrigerant circuit system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerant circuit system also capable of promoting over-cooling while appropriately controlling a temperature of a compressor and provide a process of control.SOLUTION: A refrigerant circuit system 1 comprises a gas-liquid heat exchanger 20 for heat exchanging between high pressure refrigerant and low pressure refrigerant; a bypass passage 21 for bypassing the high pressure refrigerant to more upstream side than that of a pressure reducing part 151; a bypass valve 22 capable of adjusting a flow rate; and a control part 25 for applying an instruction that corresponds to the flow rate to the bypass valve 22. The control part 25 applies an instruction corresponding to a flow rate multiplied by the present (Δh'/Δh) to the bypass valve 22 under an assumption that a discharging enthalpy which is an enthalpy corresponding to a detected temperature of the discharged refrigerant is defined as h1, an enthalpy difference that is a difference of enthalpy corresponding to the detected refrigerant temperature at an inlet and an outlet of the gas-liquid heat exchanger 20 is defined as Δh, a target discharging enthalpy corresponding to a target temperature Tv allowed at a compressor 14 is defined as hv, an adapting enthalpy difference adapted to the target discharging enthalpy hv on the basis of both h1 and Δh is defined as Δh'.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a refrigerant circuit system including a gas-liquid heat exchanger and a control method for the refrigerant circuit system.

  In order to improve the performance of a refrigerant circuit system such as an air conditioner, it is important how the heat of the refrigerant can be dissipated and liquefied, and the condenser plays the role. The high-temperature and high-pressure refrigerant gas compressed by the compressor releases heat and lowers enthalpy by heat exchange with air in the condenser. Here, the performance can be improved as the enthalpy is reduced by promoting supercooling. However, in the current situation where the temperature of the refrigerant gas is dissipated to a temperature close to the air temperature due to technological advances, further promotion of supercooling is achieved. Has become difficult.

Therefore, if a gas-liquid heat exchanger (both internal heat exchanger and intercooler) that exchanges heat between the high-pressure refrigerant liquefied by the condenser and the low-pressure refrigerant gas after passing through the evaporator is used, Can be further liquefied to lower enthalpy.
However, since the temperature of the low-pressure refrigerant sucked into the compressor increases due to heat radiation from the high-pressure refrigerant to the low-pressure refrigerant in the gas-liquid heat exchanger, the temperature of the compressor rises. In order to suppress the temperature of the compressor to an allowable temperature, there is an example in which only a part of the low-pressure refrigerant that has passed through the evaporator is passed through the gas-liquid heat exchanger and the rest is bypassed (Patent Document 1). That is, the flow rate of the low-pressure refrigerant radiated from the high-pressure refrigerant is adjusted by bypass. In Patent Document 1, a bypass path and a bypass valve are provided on the outlet side of the evaporator, and low-pressure refrigerant is sucked into the compressor from the bypass path.

JP 2000-346466 A

  When attempting to adjust the flow rate of the low-pressure refrigerant that passes through the evaporator and flows through the gas-liquid heat exchanger as in Patent Document 1, it is difficult to adjust the flow rate because the refrigerant is a low-pressure gas. In addition, since the bypassed refrigerant is sucked into the compressor, if the flow rate of the bypassed refrigerant is changed, the effect directly acts on the compressor, and the compressor temperature becomes lower than the target temperature. Overshoot and hunting are likely to occur.

  In view of the above, an object of the present invention is to provide a refrigerant circuit system and a refrigerant circuit system control method capable of promoting supercooling while appropriately controlling the temperature of the compressor.

  The present invention is a refrigerant circuit system including a compressor, a condenser, a decompression unit, and an evaporator. The refrigerant circuit system further includes a high-pressure refrigerant that has passed through the condenser and a low-pressure refrigerant that has passed through the evaporator. A gas-liquid heat exchanger that exchanges heat, a bypass path that accepts at least a portion of the high-pressure refrigerant that goes from the condenser to the gas-liquid heat exchanger, and bypasses it upstream from the decompression section, and a high pressure that flows into the bypass path A flow rate adjustment unit capable of adjusting the flow rate of the refrigerant, and a control unit that gives a command according to the flow rate to the flow rate adjustment unit, the control unit corresponding to the detected temperature of the discharged refrigerant discharged from the compressor The discharge enthalpy, which is the enthalpy, is h1, the difference between the enthalpy corresponding to the detected temperature of the refrigerant at the inlet of the gas-liquid heat exchanger and the enthalpy corresponding to the detected temperature of the refrigerant at the outlet of the gas-liquid heat exchanger Enter Based on the target discharge enthalpy corresponding to the target discharge enthalpy hv based on hv, h1 and Δh, the enthalpy of the inlet and outlet of the gas-liquid heat exchanger corresponding to the target discharge enthalpy hv is Given that the compatible enthalpy difference, which is the difference, is Δh ′, give a command corresponding to the ratio of Δh ′ to Δh, that is, a command corresponding to the current (Δh ′ / Δh) times flow rate, to the flow rate adjustment unit. It is characterized by.

  In the refrigerant circuit system of the present invention, the target temperature range including the target temperature Tv and having the upper limit temperature and the lower limit temperature is set, and the control unit sets the upper limit discharge corresponding to the upper limit temperature from the lower limit discharge enthalpy corresponding to the lower limit temperature. It is preferable to obtain a suitable enthalpy difference Δh ′ that can accommodate the target discharge enthalpy hv by the enthalpy.

  The refrigerant circuit system of the present invention is an outdoor unit that functions as a condenser during cooling operation and functions as an evaporator during heating operation, by switching between cooling operation and heating operation by changing the direction of refrigerant flow. Positioned between the heat exchanger, the indoor heat exchanger that functions as an evaporator during cooling operation, and functions as a condenser during heating operation, and the gas-liquid heat exchanger and evaporator during cooling operation, and functions as a decompression unit Preferably, the air conditioner includes a cooling decompression unit, and a heating decompression unit that is located between the gas-liquid heat exchanger and the evaporator during heating operation and functions as a decompression unit.

  The present invention is also a control method for a refrigerant circuit system including a compressor, a condenser, a decompression unit, and an evaporator, wherein the refrigerant circuit system further passes through the high-pressure refrigerant that has passed through the condenser and the evaporator. A gas-liquid heat exchanger for exchanging heat with the low-pressure refrigerant, a bypass path for accepting at least a part of the high-pressure refrigerant from the condenser to the gas-liquid heat exchanger, and bypassing upstream of the decompression unit, and a bypass path A flow rate adjustment unit capable of adjusting the flow rate of the high-pressure refrigerant flowing into the compressor, and detecting the temperature of the refrigerant discharged from the compressor; and the temperature of the refrigerant at the inlet of the gas-liquid heat exchanger The step of detecting, the step of detecting the temperature of the refrigerant at the outlet of the gas-liquid heat exchanger, and the discharge enthalpy that is the enthalpy corresponding to the detected temperature of the discharged refrigerant is h1, the detected temperature of the refrigerant at the inlet Assuming that the enthalpy difference, which is the difference between the enthalpy and the enthalpy corresponding to the detected temperature of the refrigerant at the outlet, is Δh, and the target discharge enthalpy corresponding to the target temperature Tv allowed for the compressor is hv, h1 and Δh Based on the step of obtaining a compatible enthalpy difference Δh ′, which is a difference in enthalpy between the inlet and outlet of the gas-liquid heat exchanger that matches the target discharge enthalpy hv, and the flow rate adjustment unit, the current (Δh ′ / Δh) Providing a command corresponding to the double flow rate.

  In the control method of the refrigerant circuit system of the present invention, the target temperature range including the target temperature Tv and having the upper limit temperature and the lower limit temperature is set, and in the step of obtaining Δh ′, from the lower limit discharge enthalpy corresponding to the lower limit temperature It is preferable to obtain a suitable enthalpy difference Δh ′ that can accommodate the target discharge enthalpy hv by the upper limit discharge enthalpy corresponding to the upper limit temperature.

From the relationship between the enthalpy difference Δh corresponding to the effect of supercooling by the gas-liquid heat exchanger and the discharge enthalpy h1 corresponding to the temperature of the discharged refrigerant, the temperature of the discharged refrigerant is derived so as to be within the target temperature Tv (Δh ′ By controlling the flow rate to be bypassed by the flow rate adjustment unit by the amount of / Δh), it is possible to promote supercooling and improve performance while suppressing the temperature of the discharged refrigerant.
According to the present invention, the refrigerant flowing through the gas-liquid heat exchanger and the refrigerant flowing through the bypass path based on the present and future ratio (Δh ′ / Δh) of the magnitude of the effect of the heat exchange amount by the gas-liquid heat exchanger. By changing the flow rate ratio, an appropriate response of the compressor can be obtained, and the temperature of the discharged refrigerant can be quickly stabilized at the target temperature Tv.

It is a figure which shows the structure of the refrigerant circuit system which concerns on embodiment of this invention. It is a ph diagram which shows the effect | action of the supercooling by a gas-liquid heat exchanger. It is a figure which shows the flow of control for obtaining the flow control amount of the high-pressure refrigerant to bypass. It is a figure showing the image of control with respect to the temperature of a discharge refrigerant | coolant. It is a figure which shows the structure of the refrigerant circuit system which concerns on the modification of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[First Embodiment]
A refrigerant circuit system 1 shown in FIG. 1 includes a refrigerant circuit through which refrigerant circulates. The refrigerant circuit system 1 is an air conditioner that uses a refrigeration cycle, and exchanges heat between an outdoor unit (not shown) having an outdoor heat exchanger 11 that exchanges heat between outdoor air and refrigerant, and indoor air and refrigerant. And an indoor unit (not shown) having the indoor heat exchanger 12.

  The refrigerant circuit system 1 includes a four-way valve 13 that can switch the direction of the circulating refrigerant flow, and can be switched between a cooling operation and a heating operation by operating the four-way valve 13. In FIG. 1, the refrigerant flow during cooling is indicated by solid arrows. At the time of heating, instead of closing the path A shown in the four-way valve 13, the path B shown by a broken line is opened, so that the refrigerant flows in the direction opposite to that during cooling (broken arrow in FIG. 1).

The outdoor heat exchanger 11 functions as a condenser during the cooling operation, and functions as an evaporator during the heating operation. The indoor heat exchanger 12 functions as an evaporator during cooling operation, and functions as a condenser during heating operation. The refrigerant circuit system 1 includes a fan 11 </ b> F that blows air to the outdoor heat exchanger 11 and a fan 12 </ b> F that blows air toward the indoor heat exchanger 12.
The outdoor heat exchanger 11 and the indoor heat exchanger 12 shown in FIG. 1 are denoted as a condenser and an evaporator, respectively, as functions during cooling operation.
Hereinafter, the outdoor heat exchanger 11 is referred to as a condenser 11 and the indoor heat exchanger 12 is referred to as an evaporator 12 on the basis of cooling.

  The refrigerant circuit system 1 includes a compressor 14, a condenser 11, a decompression unit 15 (151, 152), and an evaporator 12 as basic elements. As the decompression unit 15, two decompression units 151 for cooling operation and decompression unit 152 for heating operation are prepared. The decompression unit 151 for cooling operation does not function during heating operation. Similarly, the decompression unit 152 for heating operation does not function during the cooling operation.

  In addition to the above basic elements, the refrigerant circuit system 1 includes a gas-liquid heat exchanger 20 that exchanges heat between the low-pressure refrigerant that has passed through the evaporator 12 and the high-pressure refrigerant that has passed through the condenser 11, and gas-liquid heat. A bypass path 21 that bypasses part of the high-pressure refrigerant that goes to the exchanger 20 to the upstream side of the decompression unit 151, a bypass valve 22 that can adjust the flow rate of the high-pressure refrigerant that flows into the bypass path 21, and the bypass valve 22 And a control unit 25 for giving an opening degree.

The gas-liquid heat exchanger 20 includes a high-pressure path 201 through which a high-pressure refrigerant flows and a low-pressure path 202 through which a low-pressure refrigerant flows. The high-pressure refrigerant flowing through the high-pressure path 201 and the low-pressure refrigerant flowing through the low-pressure path 202 can exchange heat. Has been.
The bypass path 21 receives a part of the high-pressure refrigerant from the upstream side of the high-pressure path 201 and makes a bypass downstream of the high-pressure path 201 and upstream of the decompression unit 151.

The high-pressure refrigerant that has flowed into the gas-liquid heat exchanger 20 through the condenser 11 is supercooled by radiating heat to the low-pressure refrigerant, as indicated by 100 in FIG. 2, and the enthalpy is lowered. Thereafter, the pressure is reduced by the pressure reducing unit 151 and flows to the evaporator 12.
While the high-pressure refrigerant is supercooled by the gas-liquid heat exchanger 20, the low-temperature and low-pressure refrigerant that has passed through the evaporator 12 absorbs heat from the high-pressure refrigerant and is overheated as indicated by 101 in FIG. If it does so, the temperature of the refrigerant | coolant suck | inhaled by the compressor 14 will rise.

The predetermined target temperature Tv allowed for the compressor 14 is determined in consideration of the performance of the lubricating oil used for the sliding portion of the compressor 14 and the performance of the motor when the motor is built in the compressor 14. be able to.
In the present embodiment, a target temperature Tv that is the temperature of the refrigerant flowing through the discharge pipe that discharges the refrigerant compressed by the compressor 14 to the outside of the compressor 14 is determined. A target temperature range including the target temperature Tv and including the upper limit temperature X and the lower limit temperature X-α is set.

In the present embodiment, the gas-liquid heat exchanger 20 obtains the effect of supercooling as much as possible, and the temperature of the compressor 14 is kept from the lower limit temperature X-α to the upper limit temperature X. 22 is used to adjust the flow rate of the high-pressure refrigerant flowing through the bypass path 21. When an opening degree command according to the flow rate is given from the control unit 25 to the bypass valve 22, the opening amount of the bypass valve 22 is changed according to the opening degree command, so that the flow rate of the refrigerant flowing through the bypass path 21 is adjusted. The
Since the high-pressure refrigerant that has passed through the condenser 11 has a superior liquid phase, the flow rate can be easily and reliably adjusted as compared with the case where the flow rate of the refrigerant gas is adjusted.

  In order to adjust the flow rate of the refrigerant flowing into the bypass path 21, the pressure and temperature of the high-pressure refrigerant, the refrigerant temperature at the inlet of the gas-liquid heat exchanger 20, and the refrigerant temperature at the outlet of the gas-liquid heat exchanger 20 are used. For each enthalpy derived, the control unit 25 performs a calculation.

  In order to guide enthalpy, the refrigerant circuit system 1 of the present embodiment includes a condenser temperature sensor 11A, a discharge temperature sensor 14A, an inlet temperature sensor 20A, and an outlet temperature sensor 20B.

The condenser temperature sensor 11 </ b> A detects the temperature of the gas-liquid two-phase refrigerant flowing through the condenser 11. The temperature detected by the condenser temperature sensor 11A is regarded as the temperature of the saturated vapor, and the pressure of the high-pressure refrigerant can be obtained as the corresponding saturated vapor pressure.
When the outdoor unit is provided with a pressure gauge indicating the pressure of the high-pressure refrigerant, the value measured by the pressure gauge can be used as the pressure of the high-pressure refrigerant.
The refrigerant circuit system 1 is also provided with a temperature sensor 12A for detecting the temperature of the gas-liquid two-phase refrigerant flowing through the indoor heat exchanger 12 that functions as a condenser during the heating operation for control during the heating operation. Yes. During the heating operation, the pressure of the high-pressure refrigerant can be obtained using the temperature detected by the temperature sensor 12A.

The discharge temperature sensor 14 </ b> A detects the temperature of refrigerant (hereinafter referred to as discharge refrigerant) flowing through the discharge pipe of the compressor 14.
The inlet temperature sensor 20 </ b> A detects the temperature of the high-pressure refrigerant that flows into the inlet of the gas-liquid heat exchanger 20.
The outlet temperature sensor 20 </ b> B detects the temperature of the high-pressure refrigerant that flows out from the outlet of the gas-liquid heat exchanger 20.

An example of processing by the control unit 25 will be described.
The control unit 25 uses the pressure of the high-pressure refrigerant based on the measurement value by the condenser temperature sensor 11A or obtained by the pressure gauge and the temperature Td of the discharge refrigerant detected by the discharge temperature sensor 14A to Get h1 which is enthalpy.
Further, the enthalpy h2 of the refrigerant at the inlet of the gas-liquid heat exchanger 20 is obtained using the temperature detected by the inlet temperature sensor 20A and the pressure of the high-pressure refrigerant, and further, the temperature and high pressure detected by the outlet temperature sensor 20B. The refrigerant enthalpy h3 at the outlet of the gas-liquid heat exchanger 20 is acquired using the refrigerant pressure.
Using the enthalpy h2 at the entrance and the enthalpy h3 at the exit obtained in this way, the enthalpy difference Δh is obtained from the calculation of h2−h3. This corresponds to the effect of supercooling of the high-pressure refrigerant by the gas-liquid heat exchanger 20, in other words, the effect of overheating of the low-pressure refrigerant.

  When the high-pressure refrigerant is diverted to the bypass path 21, the effect of supercooling and overheating by the gas-liquid heat exchanger 20 is reduced by the ratio of the diverted flow rate. An increase in the temperature of the low-pressure refrigerant accompanying heat dissipation is suppressed. Then, since the temperature of the low-pressure refrigerant sucked into the compressor 14 is lowered, it becomes possible to suppress the temperature inside the compressor 14.

The detected enthalpy difference Δh indicates the effect that the gas-liquid heat exchanger 20 is currently increasing the temperature of the low-pressure refrigerant. Then, when the discharge enthalpy corresponding to the temperature of the discharge refrigerant and the pressure of the high-pressure refrigerant that will be detected when the high-pressure refrigerant does not flow through the gas-liquid heat exchanger 20 is set as h1 ′, the current discharge enthalpy h1 is It can be expressed by the following formula (1).
h1 = h1 ′ + Δh (1)
The case where the high-pressure refrigerant does not flow through the gas-liquid heat exchanger 20 corresponds to the case where the opening degree of the bypass valve 22 is fully opened in the present embodiment.

When the pressure of the high-pressure refrigerant is stable, if the enthalpy difference Δh is changed to Δh ′, the discharge enthalpy h1 changes accordingly.
Therefore, the target discharge enthalpy hv corresponding to the target temperature Tv of the discharge refrigerant allowed for the compressor 14 can be expressed by the following equation (2), where the enthalpy difference due to gas-liquid heat exchange is set as Δh ′.
hv = h1 ′ + Δh ′ (2)

From the above equation (2), Δh ′ is a suitable enthalpy difference that matches the target discharge enthalpy hv. The control unit 25 can calculate hv−h1 ′ and determine Δh ′.
From the ratio between this Δh ′ and the current enthalpy difference Δh based on the detected temperature, the control unit 25 obtains a control amount of the refrigerant flow rate to be bypassed through the bypass path 21 and gives it to the bypass valve 22 as an opening degree.
That is, an opening degree command corresponding to the current flow rate (Δh ′ / Δh) times is given to the bypass valve 22 in order to realize a suitable enthalpy difference Δh ′ that matches the target discharge enthalpy hv.

  As will be described later, the target discharge enthalpy hv is widened so that the temperature of the discharged refrigerant falls within a predetermined temperature range including the target temperature Tv, and Δh ′ is calculated so as to fit from the upper limit to the lower limit of the enthalpy. It is preferable.

The operation by the control unit 25 has been described by taking the cooling operation as an example, but the same applies to the heating operation.
During the heating operation, the switching operation of the four-way valve 13 causes the refrigerant to flow in the order of the compressor 14, the indoor heat exchanger 12 as a condenser, the decompression unit 152, the gas-liquid heat exchanger 20, and the outdoor heat exchanger 11 as an evaporator. Circulate.
Since the inlet and outlet of the gas-liquid heat exchanger 20 are opposite to those during cooling operation, the enthalpy difference Δh due to heat exchange in the gas-liquid heat exchanger 20 is determined from the enthalpy h3 corresponding to the temperature detected by the temperature sensor 20B. This corresponds to h3-h2 obtained by subtracting enthalpy h2 corresponding to the temperature detected by sensor 20A.
Except that the enthalpy difference Δh corresponds to h3−h2, and the discharge enthalpy h1 is acquired using the pressure of the high-pressure refrigerant corresponding to the condenser temperature detected by the temperature sensor 12A of the indoor heat exchanger 12. The same processing as in the cooling operation can be performed.

  Hereinafter, an example of a control procedure performed by the control unit 25 will be described with reference to FIG. Hereinafter, (Δh ′ / Δh) is referred to as ΔGr. ΔGr corresponds to an increase / decrease magnification of the heat exchange amount by the gas-liquid heat exchanger 20.

While the cooling operation or the heating operation of the refrigerant circuit system 1 is performed, the control unit 25 calculates according to the procedure shown in FIG. 3 and changes the opening degree of the bypass valve 22 according to the calculated ΔGr.
Under the restriction of the temperature of the compressor 14, it is preferable to promote supercooling by flowing a high-pressure refrigerant through the gas-liquid heat exchanger 20 as much as possible. In the present embodiment, the operation is started with the bypass valve 22 fully closed.
First, as described above, the discharge enthalpy h1 is set using the pressure of the high-pressure refrigerant obtained by using the condenser temperature sensor 11A or the pressure gauge and the temperature Td of the discharge refrigerant detected by the discharge temperature sensor 14A. Obtain (step S1).

  Next, using the temperatures detected by the temperature sensors 20A and 20B, the enthalpy h2 of the refrigerant at the inlet of the gas-liquid heat exchanger 20 and the enthalpy h3 of the refrigerant at the outlet are acquired, and enthalpy by gas-liquid heat exchange is obtained. The difference Δh is calculated (step S2).

Next, an enthalpy difference Δh ′ corresponding to the heat exchange amount of the gas-liquid heat exchanger 20 necessary for keeping the temperature of the discharged refrigerant at the target temperature Tv is calculated (step S3).
Here, the target temperature range is set using a threshold value. This target temperature range includes the target temperature Tv, and has an upper limit temperature X and a lower limit temperature (X−α). The enthalpy range including the target discharge enthalpy hv is set by the upper limit discharge enthalpy corresponding to the upper limit temperature X and the lower limit discharge enthalpy corresponding to the lower limit temperature (X−α).

  In the case where the high-pressure refrigerant does not flow through the gas-liquid heat exchanger 20, the control unit 25 causes the target discharge enthalpy hv to fall within the upper limit enthalpy corresponding to the temperature (X−α) and lower than the upper limit enthalpy corresponding to the temperature X. Δh ′ allowed to be added to the discharge enthalpy h1 ′ is calculated.

When Δh ′ is calculated, the ratio (Δh ′ / Δh) between Δh ′ and Δh is calculated as the increase / decrease magnification ΔGr of the gas-liquid heat exchange amount (step S4).
If ΔGr is smaller than 1, it is necessary to reduce the flow rate of the high-pressure refrigerant flowing through the gas-liquid heat exchanger 20 in order to suppress the temperature of the discharged refrigerant. On the other hand, if ΔGr is greater than 1, the temperature of the discharged refrigerant is lower than the allowable temperature of the compressor 14, so the flow rate of the high-pressure refrigerant flowing through the gas-liquid heat exchanger 20 is increased from the current level. There is room to promote liquefaction of

Therefore, the opening degree of the bypass valve 22 can be changed according to the following procedure according to the calculated ΔGr.
For example, when ΔGr is smaller than 1 (Y in step S5), the flow rate of the high-pressure refrigerant flowing through the gas-liquid heat exchanger 20 is reduced unless the opening degree of the bypass valve 22 is fully open (N in step S6). Then, an opening degree command for increasing the opening degree is given to the bypass valve 22 (step S7). Then, on the basis of the opening degree command, the bypass valve 22 is driven to the opening amount that is the current ΔGr times. For example, the bypass valve 22 is driven by a driving pulse whose number of pulses per unit time is the current ΔGr times.
For example, the minimum pulse number is set to 0.01 or the like so that the bypass valve 22 can be opened even if the current pulse number is 0 because the bypass valve 22 is fully closed.

  When ΔGr is greater than 1 (Y in step S8), the flow rate of the high-pressure refrigerant flowing through the gas-liquid heat exchanger 20 is increased unless the opening degree of the bypass valve 22 is fully closed (N in step S9). Therefore, an opening degree command for reducing the opening degree is given to the bypass valve 22 (step S10).

  If ΔGr = 1 (step S11), the heat exchange amount by the gas-liquid heat exchanger 20 is adapted to the target temperature Tv, and therefore the opening degree of the bypass valve 22 is maintained as it is.

  According to the present embodiment described above, the temperature of the discharged refrigerant is determined from the relationship between the enthalpy difference Δh corresponding to the effect of supercooling by the gas-liquid heat exchanger 20 and the discharge enthalpy h1 corresponding to the temperature Td of the discharged refrigerant. Is controlled to change the opening degree of the bypass valve 22 by the amount of ΔGr led so as to be within the target temperature Tv, thereby suppressing the temperature of the discharged refrigerant and promoting supercooling to improve the performance of the air conditioner. Can be planned.

  In addition, since the high-pressure refrigerant that has bypassed the bypass path 21 is caused to flow upstream from the decompression unit 151, unlike the case where the bypassed high-pressure refrigerant is caused to flow before the compressor 14, the evaporator 12. The heat exchange performance of the evaporator 12 can be maintained without reducing the amount of refrigerant circulating to the evaporator.

  In the present embodiment, based on the current and future ratio (Δh ′ / Δh) of the magnitude of the effect of the heat exchange amount by the gas-liquid heat exchanger 20, the refrigerant flowing through the gas-liquid heat exchanger 20 and the bypass path 21 are changed. By changing the ratio of the flow rate to the flowing refrigerant, an appropriate response of the compressor 14 can be obtained, and the temperature of the discharged refrigerant can be stabilized at the target temperature Tv at an early stage.

The alternate long and short dash line in FIG. 4 shows a case where the bypass flow rate is reduced by the bypass valve 22 at a time because the temperature of the discharged refrigerant exceeds the temperature Tv allowed for the compressor. In this case, overshoot and hunting are likely to occur due to excessive response of the temperature of the discharged refrigerant.
The broken line shown in FIG. 4 shows the case where the bypass flow rate is gradually reduced by the bypass valve 22 when the temperature of the discharged refrigerant exceeds the temperature Tv allowed for the compressor 14. In this case, there is a possibility that the bypass flow rate is insufficient and the discharge temperature cannot be lowered to the allowable temperature Tv.
According to the control of the present embodiment, as shown by the thick solid line in FIG. 4, the temperature of the discharged refrigerant appropriately follows the change in the magnitude of the effect of gas-liquid heat exchange accompanying the change in ΔGr. The temperature of the refrigerant is quickly stabilized at the target temperature Tv. Since the bypassed refrigerant is allowed to flow upstream of the decompression unit 151 that is away from the compressor 14, it can be avoided that the temperature of the discharged refrigerant responds sensitively, which also contributes to the stability of the discharged temperature.

Instead of the bypass valve 22 of the present embodiment, as shown in FIG. 5, a flow rate adjusting unit 23 that can adjust the flow rate of the refrigerant flowing into the bypass path 21 can be used.
The flow rate adjustment unit 23 and the control unit 25 on the right side in FIG. 5 that function during the cooling operation and the left flow rate adjustment unit 23 and the control unit 25 in FIG. 5 that function during the heating operation are switched and used.
The flow rate adjusting unit 23 can cause the entire amount of the high-pressure refrigerant that passes through the condenser 11 and goes to the gas-liquid heat exchanger 20 to flow into the bypass path 21 as necessary. If the entire amount of the high-pressure refrigerant flows into the bypass path 21, the high-pressure refrigerant does not flow through the gas-liquid heat exchanger 20, so the heat of the compressor 14 into which the low-pressure refrigerant is sucked without radiating heat from the high-pressure refrigerant to the low-pressure refrigerant. Can be suppressed.
Even when the flow rate adjusting unit 23 is used, the control unit 25 calculates the enthalpy difference Δh ′ by the same method as in the above embodiment, and sends a command corresponding to the current Δh ′ / Δh times bypass flow rate to the flow rate adjusting unit. 23, the same effect as the above embodiment can be obtained.

  In addition to the above, as long as the gist of the present invention is not deviated, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

  The refrigerant circuit system of the present invention can also be configured as a system dedicated to cooling operation or dedicated to heating operation. In that case, the four-way valve 13 is not necessary and only one decompression unit 15 is sufficient. In addition, it is sufficient to prepare a condenser temperature sensor only for one of the two heat exchangers 11 and 12 that functions as a condenser.

  The refrigerant circuit system of the present invention can be applied to an appropriate device using a refrigeration cycle such as a freezer or a water heater in addition to an air conditioner.

1 Refrigerant circuit system 11 Outdoor heat exchanger (condenser / evaporator)
11A Condenser temperature sensor 12 Indoor heat exchanger (evaporator / condenser)
12A Temperature sensor 13 Four-way valve 14 Compressor 14A Discharge temperature sensor 15 Decompression unit 151 Decompression unit (cooling decompression unit)
152 Pressure reducing part (Heating pressure reducing part)
20 Gas-liquid heat exchangers 20A and 20B Temperature sensor 21 Bypass path 22 Bypass valve (flow rate adjusting unit)
23 Flow control unit 25 Control unit 201 High pressure path 202 Low pressure path Td Temperature ΔGr Increase / decrease magnification

Claims (5)

A refrigerant circuit system comprising a compressor, a condenser, a decompression unit, and an evaporator,
The refrigerant circuit system further includes:
A gas-liquid heat exchanger that exchanges heat between the high-pressure refrigerant that has passed through the condenser and the low-pressure refrigerant that has passed through the evaporator;
A bypass path that accepts at least a portion of the high-pressure refrigerant from the condenser toward the gas-liquid heat exchanger and bypasses the upstream of the decompression unit;
A flow rate adjustment unit capable of adjusting the flow rate of the high-pressure refrigerant flowing into the bypass path;
A control unit that gives a command according to the flow rate to the flow rate adjustment unit,
The controller is
A discharge enthalpy that is an enthalpy corresponding to the detected temperature of the refrigerant discharged from the compressor is h1,
An enthalpy difference that is a difference between an enthalpy corresponding to the detected temperature of the refrigerant at the inlet of the gas-liquid heat exchanger and an enthalpy corresponding to the detected temperature of the refrigerant at the outlet of the gas-liquid heat exchanger is Δh,
The target discharge enthalpy corresponding to the target temperature Tv allowed for the compressor is hv,
Based on h1 and Δh, a matching enthalpy difference that is a difference in enthalpy between the inlet and outlet of the gas-liquid heat exchanger that matches the target discharge enthalpy hv is Δh ′,
A command corresponding to the current flow rate (Δh ′ / Δh) times is given to the flow rate adjustment unit.
A refrigerant circuit system characterized by that. A target temperature range including the target temperature Tv and having an upper limit temperature and a lower limit temperature is set,
The control unit obtains the adaptive enthalpy difference Δh ′ that can accommodate the target discharge enthalpy hv from a lower limit discharge enthalpy corresponding to the lower limit temperature to an upper limit discharge enthalpy corresponding to the upper limit temperature.
The refrigerant circuit system according to claim 1. A switching unit capable of switching between cooling operation and heating operation by changing the direction of the flow of the refrigerant;
An outdoor heat exchanger that functions as the condenser during the cooling operation and functions as the evaporator during the heating operation;
An indoor heat exchanger that functions as the evaporator during the cooling operation and functions as the condenser during the heating operation;
A cooling decompression unit that is located between the gas-liquid heat exchanger and the evaporator during the cooling operation and functions as the decompression unit;
An air conditioner including a heating decompression unit located between the gas-liquid heat exchanger and the evaporator during the heating operation and functioning as the decompression unit,
The refrigerant circuit system according to claim 1 or 2. A method for controlling a refrigerant circuit system including a compressor, a condenser, a decompression unit, and an evaporator,
The refrigerant circuit system further includes:
A gas-liquid heat exchanger that exchanges heat between the high-pressure refrigerant that has passed through the condenser and the low-pressure refrigerant that has passed through the evaporator;
A bypass path that accepts at least a portion of the high-pressure refrigerant from the condenser toward the gas-liquid heat exchanger and bypasses the upstream of the decompression unit;
A flow rate adjustment unit capable of adjusting the flow rate of the high-pressure refrigerant flowing into the bypass path,
Detecting the temperature of the refrigerant discharged from the compressor;
Detecting the temperature of the refrigerant at the inlet of the gas-liquid heat exchanger; and detecting the temperature of the refrigerant at the outlet of the gas-liquid heat exchanger;
The discharge enthalpy that is the enthalpy corresponding to the detected temperature of the discharged refrigerant is h1, the difference between the enthalpy corresponding to the detected temperature of the refrigerant at the inlet and the enthalpy corresponding to the detected temperature of the refrigerant at the outlet Assuming that a certain enthalpy difference is Δh and a target discharge enthalpy corresponding to a target temperature Tv allowed for the compressor is hv, based on h1 and Δh, the gas-liquid heat exchanger that matches the target discharge enthalpy hv Obtaining a matching enthalpy difference Δh ′, which is the difference in enthalpy between the inlet and the outlet;
Providing the flow rate adjustment unit with a command corresponding to the current flow rate (Δh ′ / Δh) times,
A control method for a refrigerant circuit system. A target temperature range including the target temperature Tv and having an upper limit temperature and a lower limit temperature is set,
In the step of obtaining Δh ′,
Obtaining the adapted enthalpy difference Δh ′ capable of accommodating the target discharge enthalpy hv from the lower limit discharge enthalpy corresponding to the lower limit temperature to the upper limit discharge enthalpy corresponding to the upper limit temperature;
The control method of the refrigerant circuit system of Claim 4.

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