JP2013257121A - Refrigerating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerating device capable of preventing decrease of an oil return amount to an outdoor unit.SOLUTION: A refrigerating device includes: a gas-liquid separator connected to a refrigerant pipe between a first throttling device and an evaporator to separate a refrigerant flowing out from the first throttling device into a liquid refrigerant and a gas refrigerant; and a bypass circuit connected to the gas-liquid separator at one side and connected to a downstream side of the evaporator at the another side. The gas refrigerant separated by the gas-liquid separator is allowed to flow to the downstream side of the evaporator through the bypass circuit, and the liquid refrigerant separated by the gas-liquid separator is allowed to flow to the evaporator.

Description

  The present invention relates to a refrigeration apparatus.

  In a conventional air conditioner, a supercooling heat exchanger that supercools refrigerant flowing out from a radiator, a throttling device that depressurizes refrigerant flowing out from the supercooling heat exchanger, and a refrigerant flowing out from the throttling device are liquidated. One having an outdoor unit including a gas-liquid separator that separates into a refrigerant and a gas refrigerant has been proposed (see, for example, Patent Document 1).

The technique described in Patent Document 1 is such that the gas refrigerant separated by the gas-liquid separator is supplied to the supercooling heat exchanger side, and heat exchange is performed between the gas refrigerant and the refrigerant flowing out of the radiator. The refrigerant circuit is configured to flow to the suction side.
That is, in the technique described in Patent Document 1, in the outdoor unit, the gas-liquid separator side and the suction side of the compressor are connected via a supercooling heat exchanger to bypass the evaporator of the indoor unit. The refrigerant circuit is configured.

Japanese Patent Laid-Open No. 9-310925 (see, for example, paragraphs [0010] to [0012] and FIG. 1)

The technology described in Patent Document 1 separates liquid refrigerant and gas refrigerant by a gas-liquid separator provided in the outdoor unit and supplies only the liquid refrigerant to the indoor unit side. The amount of refrigerant supplied to the indoor unit side decreases. Here, when the amount of refrigerant supplied from the outdoor unit side to the indoor unit side decreases, the pressure in the refrigerant pipe connecting the indoor unit and the outdoor unit decreases accordingly.
As described above, when the pressure in the refrigerant pipe connecting the indoor unit and the outdoor unit decreases due to the decrease in the amount of refrigerant supplied from the outdoor unit side to the indoor unit side, the fluidity of the refrigerating machine oil is impaired. Therefore, the refrigeration oil does not return from the indoor unit side to the outdoor unit side, and for example, wear of the sliding member of the compressor cannot be suppressed.

  That is, the technique described in Patent Document 1 has low fluidity of the refrigeration oil in the refrigerant pipe connecting the outdoor unit and the indoor unit, reducing the amount of oil return from the indoor unit side to the outdoor unit side. There is a possibility that the sliding member of the compressor is worn.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a refrigeration apparatus that can prevent the amount of oil returned to the outdoor unit from being reduced.

  A refrigerating apparatus according to the present invention is a refrigerating apparatus having a refrigerating cycle in which a compressor, a condenser, a first throttling device, and an evaporator are connected by a refrigerant pipe, and a refrigerant pipe between the first throttling apparatus and the evaporator. A gas-liquid separator connected to separate the refrigerant flowing out from the first throttle device into a liquid refrigerant and a gas refrigerant; and a bypass circuit in which one is connected to the gas-liquid separator and the other is connected to the downstream side of the evaporator; The gas refrigerant separated by the gas-liquid separator is caused to flow downstream of the evaporator via a bypass circuit, and the liquid refrigerant separated by the gas-liquid separator is caused to flow to the evaporator.

  Since the refrigeration apparatus according to the present invention has the above-described configuration, the amount of oil return to the outdoor unit is suppressed from being reduced.

It is an example of the refrigerant circuit structure of the freezing apparatus which concerns on Embodiment 1 of this invention. It is an example of the refrigerant circuit structure of the freezing apparatus which concerns on Embodiment 2 of this invention. It is an example of the refrigerant circuit structure of the freezing apparatus which concerns on Embodiment 3 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is an example of a refrigerant circuit configuration of a refrigeration apparatus 300 according to Embodiment 1.
The refrigeration apparatus 300 is provided with an improvement for suppressing the amount of oil return from the indoor unit 200 side to the outdoor unit 100 side.

[Description of configuration]
The refrigeration apparatus 300 corresponds to, for example, a refrigerator. For example, the refrigeration apparatus 300 is installed indoors or the like. The refrigeration apparatus 300 is installed indoors or the like. 200 and an outdoor unit 100 connected via a liquid pipe 3 and a gas pipe 6.
In the first embodiment, the case where the refrigeration apparatus 300 is a refrigerator will be described as an example, but may be employed in a heat pump apparatus, for example. Further, the refrigeration apparatus 300 may be for business use having a capacity in the warehouse of, for example, about 1000 liters.

The refrigeration apparatus 300 includes a compressor 1 that compresses and discharges a refrigerant, a condenser 2 (heat radiator) that condenses the refrigerant, a first expansion device 4 and a second expansion device 12 that decompress the refrigerant, a liquid refrigerant, It has a gas-liquid separator 11 that separates into a gas refrigerant, an evaporator 5 that evaporates the refrigerant, and a bypass circuit 210 that bypasses the evaporator 5.
The refrigeration apparatus 300 is equipped with various sensors such as a temperature sensor and a pressure sensor (not shown) that detect the refrigerant temperature, and a control device that controls the number of revolutions of the compressor 1 based on the detection results of these sensors. 90.

(Outdoor unit 100)
The outdoor unit 100 is equipped with a compressor 1 and a condenser 2 connected to the compressor 1 via a discharge pipe 7. The outdoor unit 100 is connected to the indoor unit 200 via the liquid pipe 3 and the gas pipe 6. The outdoor unit 100 is also equipped with a blower (not shown) that supplies air to the condenser 2 and exchanges heat between the supplied air and the refrigerant flowing through the condenser 2.

(Liquid pipe 3, gas pipe 6 and discharge pipe 7)
The liquid pipe 3 is a pipe that connects from the refrigerant outflow side of the condenser 2 to the refrigerant inflow side of the evaporator 5 via the first expansion device 4 and the gas-liquid separator 11. A gas-liquid two-phase refrigerant flows through a portion of the liquid pipe 3 from the condenser 2 to the gas-liquid separator 11. Further, in the liquid pipe 3, the liquid refrigerant flows through the portion from the gas-liquid separator 11 to the evaporator 5.
The gas pipe 6 is a pipe connecting the refrigerant outflow side of the evaporator 5 to the refrigerant suction side of the compressor 1. The gas refrigerant evaporated in the evaporator 5 and the gas refrigerant that merges from the bypass circuit 210 into the gas pipe 6 flow through the gas pipe 6.
The discharge pipe 7 is a pipe that connects the discharge side of the compressor 1 and the refrigerant suction side of the condenser 2. A high-temperature and high-pressure gas refrigerant compressed by the compressor 1 flows through the discharge pipe 7.

(Compressor 1 and condenser 2)
The compressor 1 sucks a refrigerant, compresses the refrigerant, and discharges the refrigerant in a high temperature / high pressure state. The compressor 1 has a refrigerant discharge side connected to a condenser 2 via a discharge pipe 7 and a refrigerant suction side connected to a gas pipe 6. In addition, the compressor 1 is good to comprise, for example with an inverter compressor.
The condenser 2 performs heat exchange between the refrigerant discharged from the compressor 1 and air. One of the condensers 2 is connected to the liquid pipe 3, and the other is connected to the refrigerant discharge side of the compressor 1 via the discharge pipe 7. In addition, the condenser 2 is good to comprise, for example with the plate fin and tube type heat exchanger which can exchange heat between the refrigerant | coolant which flows through the condenser 2, and the air which passes a fin.

(Indoor unit 200)
The indoor unit 200 is equipped with the first expansion device 4, the second expansion device 12, the evaporator 5, and the gas-liquid separator 11. The indoor unit 200 is provided with a bypass circuit 210 that bypasses the evaporator 5 and connects the gas-liquid separator 11 and the gas pipe 6. The indoor unit 200 is also equipped with a blower (not shown) that supplies air to the evaporator 5 and heat-exchanges the supplied air and the refrigerant flowing through the evaporator 5 to supply the air to the interior.

(First diaphragm device 4 and second diaphragm device 12)
The first expansion device 4 is for expanding the refrigerant, and one is connected to the liquid pipe 3 and the other is connected to the gas-liquid separator 11 side.
The second expansion device 12 is provided in the bypass circuit 210 and adjusts the refrigerant amount of the gas refrigerant flowing through the bypass circuit 210. One of the second expansion devices 12 is connected to the gas pipe 6 via the bypass circuit 210, and the other is connected to the gas-liquid separator 11 via the bypass circuit 210. The first throttling device 4 and the second throttling device 12 may be composed of, for example, an electronic expansion valve having a variable opening, a capillary tube, or the like.

(Evaporator 5)
The evaporator 5 performs heat exchange between the liquid refrigerant separated by the gas-liquid separator 11 and the air. That is, the liquid refrigerant of the refrigerant separated into the liquid refrigerant and the gas refrigerant by the gas-liquid separator 11 is supplied to the evaporator 5. One of the evaporators 5 is connected to the gas-liquid separator 11 side, and the other is connected to the gas pipe 6. Note that, similarly to the condenser 2, the evaporator 5 may be configured by, for example, a plate fin-and-tube heat exchanger that can exchange heat between the refrigerant flowing through the evaporator 5 and the air passing through the fins. .

(Gas-liquid separator 11)
The gas-liquid separator 11 separates the refrigerant into a liquid refrigerant and a gas refrigerant, and is connected to the first expansion device 4 side, the evaporator 5 side, and the bypass circuit 210. More specifically, the gas-liquid separator 11 is supplied with the gas-liquid two-phase refrigerant flowing out from the first expansion device 4 and separates it into a liquid refrigerant and a gas refrigerant. The gas-liquid separator 11 supplies the liquid refrigerant from the gas-liquid separator 11 to the evaporator 5, and supplies the gas refrigerant from the gas-liquid separator 11 to the bypass circuit 210. It is connected to the.

(Bypass circuit 210)
One of the bypass circuits 210 is connected to the gas-liquid separator 11 and the other is connected to the gas pipe 6. The connection position between the bypass circuit 210 and the gas pipe 6 is within the indoor unit 200. Further, the bypass circuit 210 is provided with the second expansion device 12 so that the amount of gas refrigerant flowing out of the gas-liquid separator 11 can be adjusted.
The refrigeration apparatus 300 is provided with this bypass circuit 210, so that the gas refrigerant that does not contribute much to the cooling capacity of the refrigeration apparatus 300 is not supplied to the evaporator 5, so that the cooling capacity can be improved. ing.

(Control device 90)
Based on the detection results of a temperature sensor and a pressure sensor (not shown), the control device 90 rotates the rotational speed (including operation / stop) of the compressor 1 and the fan (not shown) attached to the condenser 2 and the evaporator 5. The number of rotations (including operation / stop), the opening degree of the first expansion device 4 and the second expansion device 12 are controlled.
The control device 90 calculates the dryness based on the refrigerant pressure on the high pressure side and the refrigerant pressure on the low pressure side and the refrigerant temperature on the refrigerant inflow side (upstream side) of the first expansion device 4.
It is as follows in detail about the calculation method of a dryness. The control device 90 calculates the saturated gas enthalpy (h _G ) and the saturated liquid enthalpy (h _L ) based on the refrigerant pressure on the low pressure side, and calculates the refrigerant pressure on the high pressure side and the temperature on the refrigerant inflow side of the first expansion device 4 ( The enthalpy (h ₁ ) on the refrigerant outflow side of the first expansion device 4 is calculated based on the inlet temperature. Further, the control device 90 calculates the saturated gas enthalpy (h _G ), the saturated liquid enthalpy (h _L ), the enthalpy (h ₁ ) on the refrigerant outflow side of the first expansion device 4, and the following equation (1): Based on the above, the dryness X is calculated.
Degree of dryness X = (h ₁ −h _L ) / (h _G −h _L ) (1)
Then, the control device 90 controls the opening degree of the second expansion device 12 so that the amount of liquid refrigerant in the gas-liquid separator 11 is maintained at a constant level based on the dryness value, and the gas-liquid separation is performed. The flow rate of the refrigerant flowing into the gas pipe 6 from the vessel 11 via the bypass circuit 210 is adjusted. The control device 90 is constituted by, for example, a microcomputer.

  In the refrigeration apparatus 300 according to the first embodiment, the refrigerant is supplied from the gas-liquid separator 11 to the gas pipe 6 side on the refrigerant outflow side of the evaporator 5, but is not limited thereto. For example, the pipes are exchanged so as to exchange heat between “the refrigerant flowing through the bypass circuit 210 on the refrigerant outflow side of the second expansion device 12” and “refrigerant flowing through the liquid pipe 3 on the refrigerant inflow side of the first expansion device 4”. Or a refrigerant-refrigerant heat exchanger (supercooling heat exchanger) may be provided. Thereby, the amount of supercooling in the refrigerant | coolant inflow side of the 1st expansion device 4 can be increased, and refrigerating capacity can be improved.

  In the refrigeration apparatus 300 according to the first embodiment, the first expansion device 4 is provided on the indoor unit 200 side, but is not limited thereto. For example, the first expansion device 4 may be provided on the outdoor unit 100 side. As a result, the amount of refrigerant required in the refrigeration cycle can be reduced by the increase in the portion of the liquid pipe 3 through which the gas-liquid two-phase refrigerant flows, which not only contributes to improving environmental performance but also compressing. It can also contribute to the reduction of the product cost of the refrigeration apparatus 300, such as the volume reduction of the pressure vessel of the machine 1.

[Refrigerant operation of refrigeration apparatus 300]
The operation of the refrigerant flowing through the refrigerant circuit shown in FIG. 1 will be described with reference to FIG.
The gaseous refrigerant compressed and discharged by the compressor 1 flows into the condenser 2. The gaseous refrigerant that has flowed into the condenser 2 is condensed by exchanging heat with air supplied from a blower attached to the condenser 2 and flows out of the condenser 2. The refrigerant flowing out of the condenser 2 flows into the first expansion device 4 and is expanded and depressurized by the first expansion device 4. The decompressed refrigerant flows into the gas-liquid separator 11 and is separated into liquid refrigerant and gas refrigerant.

The liquid refrigerant separated by the gas-liquid separator 11 flows into the evaporator 5. The liquid refrigerant flowing into the evaporator 5 evaporates by exchanging heat with air supplied from a blower attached to the evaporator 5 and flows out of the evaporator 5.
On the other hand, the gas refrigerant separated by the gas-liquid separator 11 flows into the bypass circuit 210. The flow rate of the gas refrigerant flowing into the bypass circuit 210 is adjusted by controlling the opening degree of the second expansion device 12 based on the dryness calculated by the control device 90. Thereby, the amount of liquid refrigerant in the gas-liquid separator 11 can be kept at a constant level.

  The refrigerant flowing out of the evaporator 5 and the refrigerant flowing out of the bypass circuit 210 merge and then flow out of the indoor unit 200. Then, the refrigerant that has flowed out of the indoor unit 200 flows through the gas pipe 6 and is sucked into the compressor 1.

[Effects of refrigeration apparatus 300 according to Embodiment 1]
The refrigeration apparatus 300 according to the first embodiment has a refrigerant circuit configuration that bypasses the gas refrigerant flowing into the gas-liquid separator 11 to the refrigerant outflow side of the evaporator 5. For this reason, the refrigeration apparatus 300 can raise the refrigerant | coolant pressure in the gas piping 6 compared with the refrigerant circuit structure which bypasses a gas refrigerant in the conventional outdoor unit. If the refrigerant pressure in the gas pipe 6 can be increased, the refrigerant flow rate in the gas pipe 6 is increased, and the shearing force to push the oil increases, so that the fluidity of the refrigerating machine oil is improved. .
That is, the refrigeration apparatus 300 according to the first embodiment can improve the fluidity of the refrigeration oil, and the refrigeration oil in the gas pipe 6 can easily return from the indoor unit 200 side to the outdoor unit 100 side. Wear of the sliding member of the compressor 1 can be suppressed.

Embodiment 2. FIG.
FIG. 2 is an example of a refrigerant circuit configuration of the refrigeration apparatus 301 according to the second embodiment. In the second embodiment, the difference from the first embodiment will be mainly described.
In the refrigeration apparatus 301 according to the second embodiment, the position of the first throttle device 4 of the first embodiment is changed from the indoor unit 200 side to the outdoor unit 100 side, and the third throttle device 13 is provided in the indoor unit 200. This is different from the configuration of the refrigeration apparatus 300 according to the first embodiment.

(Third diaphragm device 13)
One of the third expansion devices 13 is connected to the gas-liquid separator 11, and the other is provided in the evaporator 5. The third expansion device 13 may be configured with, for example, an electronic expansion valve having a variable opening degree or a capillary tube together with the first expansion device 4 and the second expansion device 12.

  Thus, by providing the 3rd expansion device 13, while being able to depressurize to the evaporation pressure required in order to obtain the target interior temperature, the part through which the fluid with reduced fluidity flows Is decreasing. More specifically, a portion of the refrigeration apparatus 301 in which the refrigerant having a low refrigerant pressure and a low fluidity flows, that is, a part in which the refrigerant having a reduced oil return capacity flows is transferred from the third expansion device 13 to the evaporator. That is, it was a part up to 5.

In the refrigeration apparatus 301 according to Embodiment 2, the refrigerant liquefied by the condenser 2 is depressurized by the first throttling device 4, and the depressurization amount (control target value) in the first throttling device 4 is, for example, the outdoor unit 100 The pressure is equivalent to the ambient temperature. However, even if a refrigerant having a pressure corresponding to the ambient temperature is supplied to the evaporator 5, the target internal temperature of the refrigeration apparatus 301 is set low so that the target internal temperature of the refrigeration apparatus 301 is not sufficient because the amount of decompression is insufficient. Can't get.
Therefore, the refrigeration apparatus 301 is provided with the third expansion device 13, and is necessary for the control device 90 to obtain the target internal temperature of the refrigeration device 301 by adjusting the opening of the third expansion device 13. The pressure is reduced to a proper evaporation pressure (target evaporation temperature of the evaporator 5).

  The control device 90 stores in advance pressure and temperature set values in the gas pipe 6 that can return the refrigeration oil with high efficiency from the indoor unit 200 side to the outdoor unit 100 side. That is, the control device 90 adjusts the opening degree of the second expansion device 12 based on the preset pressure and temperature set values in the gas pipe 6 to ensure sufficient oil return capability. ing.

[Effects of refrigeration apparatus 301 according to Embodiment 2]
The refrigeration apparatus 301 according to the second embodiment has the following effects in addition to the effects of the refrigeration apparatus 300 according to the first embodiment.

  The refrigeration apparatus 301 according to the second embodiment achieves “reduction of the portion through which the refrigerant whose oil return capacity is reduced flows”, improves the fluidity of the refrigeration oil, and supplies the refrigeration oil in the gas pipe 6 to the indoor unit. It is easy to return from the 200 side to the outdoor unit 100 side.

  The refrigeration apparatus 301 according to the second embodiment adjusts the opening degree of the third expansion device 13 based on the evaporation pressure necessary to obtain the target internal temperature. Since the opening degree is adjusted based on preset values of pressure and temperature in the gas pipe 6, it is possible to “ensure sufficient oil return capability”.

  In the refrigeration apparatus 301 according to the second embodiment, the part through which the refrigerant whose oil return capacity is reduced flows is the part from the third expansion device 13 to the evaporator 5, so that the refrigeration apparatus 301 is used for ultra-low temperature (for example, Even when the internal temperature is about −50 [° C.], the fluidity of the refrigerating machine oil is improved, and the refrigerating machine oil in the gas pipe 6 is easily returned from the indoor unit 200 side to the outdoor unit 100 side. Is possible.

In the refrigeration apparatus 301 according to the second embodiment, the first expansion device 4 is provided in the outdoor unit 100, and the refrigerant pressure that passes through the first expansion device 4 is adjusted to be a pressure corresponding to the ambient temperature of the outdoor unit 100. The refrigerant having the pressure corresponding to the ambient temperature is depressurized by the third expansion device 13 to the evaporation pressure necessary for obtaining the target internal temperature.
As described above, since the first expansion device 4 does not reduce the pressure to the evaporating pressure necessary to obtain the target internal temperature, for example, there is no heat insulation around the liquid pipe 3. However, it is possible to reduce the amount of the refrigerant sealed in the refrigeration cycle while suppressing the condensation of the liquid pipe 3.

  In the refrigeration apparatus 301 according to the second embodiment, as described above, the first expansion device 4 does not depressurize to the evaporation pressure necessary to obtain the target internal temperature, so that the refrigerant pressure in the liquid pipe 3 However, it becomes lower than the case where the 1st aperture device 4 is not provided. For this reason, even when replacing the outdoor unit 100 with a product having a different refrigerant, if the refrigerant pressure is controlled to be equal to or lower than the pressure resistance of the pipe, the existing liquid pipe 3 can be easily used.

Embodiment 3 FIG.
FIG. 3 is an example of a refrigerant circuit configuration of the refrigeration apparatus 302 according to the third embodiment. In the third embodiment, differences from the first and second embodiments will be mainly described.
The refrigeration apparatus 302 according to the third embodiment also includes the refrigeration apparatus 300 according to the first and second embodiments, even when the indoor unit 200 is downsized due to circumstances such as severe restrictions on the installation space of the indoor unit 200. Like 301, the fluidity | liquidity of refrigerating machine oil can be improved and the refrigerating machine oil in the gas piping 6 is comprised easily to return from the indoor unit 200 side to the outdoor unit 100 side.

  The refrigeration apparatus 302 is provided with an oil level detection means 30 that detects a decrease in the oil level inside the compressor 1. The refrigeration apparatus 302 has a valve diameter larger than the maximum valve diameters of the gas-liquid separator 31 and the first throttling device 4 instead of the gas-liquid separator 11 and the second throttling apparatus 12 of the first and second embodiments. On-off valve 14 is provided. Further, the refrigeration apparatus 302 is provided with a bypass circuit 220 to which the on-off valve 14 is connected instead of the bypass circuit 210.

(Oil level detecting means 30)
The oil level detection means 30 detects the amount of oil (refrigeration oil) in the compressor 1 by detecting the height position of the oil level in the bottom oil reservoir of the compressor 1. The oil level detection means 30 is connected to the control device 90. Thus, the control device 90 can adjust the opening degree of the on-off valve 14 based on the detection result of the oil level detection means 30. The control device 90 is set with a “predetermined time” for opening the on-off valve 14 as will be described later.
The oil level detection means 30 has, for example, an electrode provided in the bottom oil reservoir of the compressor 1, and a capacitance type that detects the oil level from a change in capacitance caused by contact of refrigerating machine oil with the electrode. It is good to adopt one.

(Gas-liquid separator 31)
The gas-liquid separator 31 stores liquid refrigerant and discharges gas refrigerant. That is, the gas-liquid separator 31 according to the third embodiment stores the liquid refrigerant and discharges the gas refrigerant, unlike the gas-liquid separator 11 according to the first and second embodiments. One of the gas-liquid separator 31 is connected to the evaporator 5 side and the bypass circuit 220 via the gas pipe 6, and the other is connected to the suction side of the compressor 1 via the gas pipe 6. The gas-liquid separator 31 is connected to an oil return pipe for returning the refrigeration oil stored in the gas-liquid separator 31 into the compressor 1 although not shown.

(Open / close valve 14)
The on-off valve 14 is provided in the bypass circuit 220 and adjusts the amount of refrigerant flowing through the bypass circuit 220. One of the on-off valves 14 is connected to the upstream side of the first throttling device 4 of the liquid pipe 3 via the bypass circuit 220, and the other is connected to the gas pipe 6 via the bypass circuit 220.

  When the flow path resistance of the bypass circuit 220 and the flow path resistance of the liquid pipe 3 connected to the expansion device 4 are equal, as described below, the valve diameter of the on-off valve 14 is set as follows. Good. That is, the valve diameter of the on-off valve 14 is set larger than the maximum valve diameter of the first throttle device 4 of the first and second embodiments. Thereby, the flow path resistance on the bypass circuit 220 side is smaller than the flow path resistance on the expansion device 4 side, and the amount of refrigerant supplied to the bypass circuit 220 side than the amount of refrigerant flowing to the first expansion device 4 side. Will be more. That is, the refrigerant flowing through the liquid pipe 3 is mainly decompressed by the on-off valve 14 and flows into the gas pipe 6 in a gas-liquid two-phase state.

  Further, when the flow path resistance of the bypass circuit 220 and the flow path resistance of the liquid pipe 3 connected to the expansion device 4 are not equal due to differences in the length and diameter of the bypass circuit 220 and the liquid pipe 3, What is necessary is just to set the valve diameter of the on-off valve 14 so that the channel resistance of the on-off valve 14 and the bypass circuit 220 may become smaller than the channel resistance of the liquid piping 3 and the 1st expansion device 4.

[Operation of Refrigeration Apparatus 302]
Next, the operation will be described.
When the control device 90 detects a decrease in the oil level of the refrigerating machine oil of the compressor 1 based on the detection result of the oil level detection means 30, the control device 90 performs control to open the on-off valve 14 temporarily. In addition, since the valve diameter of the on-off valve 14 is larger than the diameter of the first throttling device 4, the refrigerant flowing through the liquid pipe 3 mainly flows through the bypass circuit 220 and is decompressed by the on-off valve 14, and is in a gas-liquid two-phase state. And flows into the gas pipe 6. That is, the gas-liquid two-phase refrigerant is supplied to the gas pipe 6 through which the gas refrigerant mainly flows.

Thereby, the refrigerating machine oil staying in the gas pipe 6 flows from the indoor unit 200 side to the outdoor unit 100 side so as to be washed away while floating at the interface between the gas refrigerant and the liquid refrigerant. The refrigerating machine oil that has flowed into the outdoor unit 100 is returned to the compressor 1 through the gas-liquid separator 31 and an oil return pipe (not shown) that connects the gas-liquid separator 31 and the compressor 1.
Here, the “predetermined time” that is the time for opening the on-off valve 14 and set in the control device 90 may be a time that does not cause the gas-liquid separator 31 to become full. Thereby, it is possible to prevent the compressor 1 from being damaged by the liquid back.

Further, if the control device 90 determines that the oil level of the compressor 1 does not recover (does not rise) even if the valve of the on-off valve 14 is opened for “predetermined time”, the blower of the evaporator 5 is temporarily turned on. The refrigeration oil staying in the evaporator 5 is controlled to be returned to the gas-liquid separator 31 by being stopped (ON / OFF control).
In determining whether the oil level of the compressor 1 is restored, the control device 90, for example, after “a preset time has elapsed since the opening of the on-off valve 14”, If the oil level has risen to the height position, it may be determined that the oil level has recovered.

  As described above, in the third embodiment, the opening and closing of the bypass circuit 220 in the indoor unit 200 and the ON / OFF control of the blower attached to the evaporator 5 are performed on the gas pipe 6 through which the gas refrigerant flows. The gas-liquid two-phase refrigerant is temporarily allowed to flow to wash away the refrigerating machine oil. As a result, the fluidity of the refrigerating machine oil can be reduced even under severe installation conditions such as providing a large unit in which the gas-liquid separator 11 is mounted in the indoor unit 200 as in the first and second embodiments. Thus, the refrigerating machine oil in the gas pipe 6 can be easily returned from the indoor unit 200 side to the outdoor unit 100 side.

[Effects of refrigeration apparatus 302 according to Embodiment 3]
The refrigeration apparatus 302 according to the third embodiment has the following effects in addition to the effects of the refrigeration apparatus 300 according to the first embodiment.

  The refrigeration apparatus 302 according to the third embodiment can reduce the size of the indoor unit 200 because the gas-liquid separator 31 is mounted on the indoor unit 200.

  DESCRIPTION OF SYMBOLS 1 Compressor, 2 Condenser, 3 Liquid piping, 4 1st expansion device, 5 Evaporator, 6 Gas piping, 7 Discharge piping, 11 Gas-liquid separator, 12 2nd expansion device, 13 3rd expansion device, 14 Opening and closing Valve, 30 Oil level drop detecting means, 31 Gas-liquid separator, 90 Control device, 100 Outdoor unit, 200 Indoor unit, 210, 220 Bypass circuit, 300, 301, 302 Refrigeration device.

Claims (7)

In a refrigeration apparatus having a refrigeration cycle in which a compressor, a condenser, a first expansion device, and an evaporator are connected by a refrigerant pipe,
A gas-liquid separator connected to the refrigerant pipe between the first expansion device and the evaporator, and separating the refrigerant flowing out of the first expansion device into liquid refrigerant and gas refrigerant;
One having a bypass circuit connected to the gas-liquid separator and the other connected to the downstream side of the evaporator;
A gas refrigerant separated by the gas-liquid separator is caused to flow downstream of the evaporator via the bypass circuit, and a liquid refrigerant separated by the gas-liquid separator is caused to flow to the evaporator. apparatus. In the bypass circuit,
A second expansion device is provided for adjusting the flow rate of the refrigerant flowing through the bypass circuit;
The opening degree of the second throttle device is
It controls based on the quantity of the liquid refrigerant in the said gas-liquid separator. The refrigeration apparatus of Claim 1 characterized by the above-mentioned. A third throttle device connected to the refrigerant pipe between the gas-liquid separator and the evaporator and depressurizing the liquid refrigerant separated by the gas-liquid separator;
The liquid refrigerant separated by the gas-liquid separator is
The refrigeration apparatus according to claim 1 or 2, wherein the pressure is reduced to a pressure corresponding to a target evaporation temperature of the evaporator by the third expansion device. An outdoor unit provided with at least the compressor and the condenser;
The refrigeration apparatus according to any one of claims 1 to 3, further comprising an indoor unit provided with at least the evaporator. In the outdoor unit,
The refrigeration apparatus according to claim 4, wherein the first expansion device is provided. An outdoor unit provided with at least the compressor and the condenser, and at least the evaporator and the first, having a refrigeration cycle in which a compressor, a condenser, a first expansion device, and an evaporator are connected by refrigerant piping. In a refrigeration apparatus having an indoor unit provided with a throttle device,
The indoor unit is
The refrigerant that is connected to the refrigerant suction side of the compressor and that flows into the outdoor unit from the indoor unit side is separated into liquid refrigerant and gas refrigerant, the gas refrigerant is supplied to the compressor, and the liquid refrigerant is stored. A gas-liquid separator,
A bypass circuit in which one is connected to the upstream side of the first throttle device and the other is connected to the downstream side of the evaporator to bypass the first throttle device and the evaporator;
An on-off valve provided connected to the bypass circuit and having a valve diameter larger than the maximum valve diameter of the first throttle device;
A refrigeration apparatus comprising: Oil level detection means for detecting the oil level height of the refrigerating machine oil stored in the compressor,
A control device that controls opening and closing of the on-off valve based on a detection result of the oil level detection means,
The controller is
When it is determined from the detection result of the oil level detection means that the oil level of the refrigerating machine oil is a predetermined value or more, the on-off valve is closed,
When it is determined from the detection result of the oil level detection means that the oil level height of the refrigerating machine oil is less than a predetermined value, the on-off valve is opened, and the refrigerant on the upstream side of the first expansion device is the evaporator. The refrigeration apparatus according to claim 6, wherein the refrigeration apparatus flows to the downstream side of the refrigeration unit.

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