JP7224841B2 - Refrigerator and chiller equipment equipped with it - Google Patents

Description

TECHNICAL FIELD The present invention relates to a refrigerator and chiller equipment having the same.

In general, the inside of a compressor provided in a refrigerant circuit of a refrigerator is filled with lubricating oil in order to suppress wear of sliding parts. A part of the filled oil is discharged to the refrigerant circuit together with the refrigerant discharged from the compressor. At this time, it is necessary to control the amount of oil in the compressor in order to properly lubricate the sliding parts. Further, if the refrigerant discharged from the compressor contains a large amount of oil, the efficiency of heat exchange in the heat exchanger is lowered. As a countermeasure, an oil separator may be provided in the refrigerant circuit to collect the oil contained in the refrigerant and then return it to the compressor.

As an example of a configuration for returning oil to a compressor, Patent Document 1 describes one oil separator provided for the two compressors in a refrigerant circuit having two compressors. . The oil accumulated in the oil separator is returned to each compressor via two oil recovery pipes. Further, it is described that one of the two oil recovery pipes is provided with an on-off valve, and that the on-off valve is opened and closed in comparison with the operating frequency of each compressor.

Further, Patent Literature 2 describes one oil separator provided for the two compressors in a refrigerant circuit having two compressors. The oil accumulated in the oil separator is returned to each compressor via two oil recovery pipes. Further, it is described that the two oil recovery pipes are provided with motor-operated valves, and that the degree of opening of each motor-operated valve is adjusted according to the operating frequency of each compressor.

JP-A-64-58970 JP 2013-108649 A

For example, if the path length of the refrigerant circuit is short, such as in a chiller facility, the oil that is discharged from the compressor together with the refrigerant returns to the compressor relatively quickly, so it may be possible to omit the oil separator described above. .

However, if the oil separator is omitted, the refrigerant will contain oil. In particular, in an overloaded state where the compressor rotates at high speed, the amount of oil contained in the refrigerant discharged from the compressor tends to increase. When the amount of oil contained in the refrigerant becomes large, the efficiency of heat exchange in the heat exchanger is lowered. In addition, it becomes necessary to increase the amount of oil to be charged in order to compensate for the lack of oil in the compressor.

On the other hand, when an oil separator is provided, the oil may contain some refrigerant when returning the oil from the oil separator to the compressor. The refrigerant is returned to the compressor without doing any refrigeration work and thus is a loss to compressor work.

The present invention has been made in view of such circumstances, and as well as securing the amount of oil in the compressor without increasing the amount of oil to be charged, it suppresses the phenomenon that the refrigerant returns to the compressor from the oil separator. for the purpose.

In order to solve the above problems, the refrigerator of the present invention and the chiller facility equipped with the same employ the following means.
That is, a refrigerator according to an aspect of the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and a first refrigerant that connects the compressor and the condenser. a pipe, a second refrigerant pipe that branches from the first refrigerant pipe at a branching portion and joins the first refrigerant pipe again downstream of the branching portion; an oil separator that separates the oil, an oil return pipe that returns the oil separated by the oil separator to the compressor, an on-off valve provided in the oil return pipe, and the on-off valve according to the load state of the compressor The first refrigerant pipe and the second refrigerant pipe are not provided with a valve for switching the flow direction of the refrigerant at the branch portion.

According to the refrigerator according to this aspect, the refrigerant can be guided from the compressor to the condenser by the first refrigerant pipe, and part of the refrigerant can be guided to the oil separator by the second refrigerant pipe. Further, for example, when the compressor is in a load state during normal operation (hereinafter referred to as "normal load state") or in a lower load state than that, the on-off valve provided in the oil return pipe is closed, and the compressor is normally operated. The on-off valve can be opened when the overload state is higher than the load state. At this time, for example, by setting the diameter of the first refrigerant pipe to be equal to or larger than the diameter of the second refrigerant pipe, most of the refrigerant is guided from the compressor to the condenser by the first refrigerant pipe regardless of the load state. , the amount of refrigerant introduced to the oil separator by the second refrigerant pipe can be made smaller than that.
The oil separated by the oil separator may contain a small amount of refrigerant compressed by the compressor. That is, if the oil is returned to the compressor as it is, the compressed refrigerant will inevitably be returned from the oil separator to the compressor via the oil return pipe. This inevitably returned refrigerant does not exchange heat in the condenser, resulting in a loss of work for the compressor. However, when the oil return pipe is shut off by the on-off valve, the phenomenon in which part of the refrigerant returns from the oil separator to the compressor is suppressed, so the loss of work of the compressor can be suppressed. At this time, since the amount of oil discharged from the compressor (oil contained in the refrigerant and discharged) is small under normal or low load conditions, the oil return pipe is shut off by the on-off valve to allow the oil to flow to the compressor. Even if it is not returned, the effect on the compressor (for example, lack of oil) is negligible. On the other hand, the amount of oil discharged from the compressor is greater in the overloaded state than in the normal loaded state. Therefore, if the oil return pipe is blocked by the on-off valve, the compressor will run out of oil. However, for example, by opening the on-off valve provided in the oil return pipe when the load is overloaded rather than under normal load, the oil stored in the oil separator can be returned to the compressor. I can secure the amount of oil. Therefore, there is no need to increase the amount of oil to fill the compressor in order to make up for the lack of oil in the compressor that occurs when the compressor is overloaded.
Also, if all of the refrigerant passes through the oil separator, the oil will accumulate in the oil separator in a short period of time. In order to reduce the amount of oil, it is necessary to frequently return the oil from the oil separator to the compressor. On the other hand, by guiding most of the refrigerant from the compressor to the condenser through the first refrigerant pipe and reducing the amount of refrigerant that is guided to the oil separator, the oil is accumulated in the oil separator. can lengthen the time required for That is, in order to reduce the amount of oil accumulated in the oil separator, the frequency of returning oil from the oil separator to the compressor can be reduced. As a result, the frequency of the phenomenon in which the refrigerant returns from the oil separator to the compressor can be reduced, so the loss of work of the compressor can be suppressed.

Further, in the refrigerator according to one aspect of the present invention, the control unit closes the on-off valve when the compressor is in a load state during normal operation or in a load state lower than that during normal operation, and the compressor is is in an overload state compared to the load state during normal operation, the on-off valve is opened.

According to the refrigerator according to this aspect, when the oil discharged from the compressor is in a normal load state or a lower load state, the on-off valve provided in the oil return pipe can be closed. Therefore, the phenomenon that part of the refrigerant returns from the oil separator to the compressor is suppressed, and the loss of work of the compressor can be suppressed. On the other hand, when the oil discharged from the compressor is in a normal load state or in an overload state, the on-off valve can be opened, so that the oil stored in the oil separator can be returned to the compressor. It is possible to secure the amount of oil in the compressor.

Further, in the refrigerator according to the aspect of the present invention, the first refrigerant pipe has a pipe diameter equal to or larger than that of the second refrigerant pipe.

According to the refrigerator according to this aspect, the amount of refrigerant flowing through the first refrigerant pipe can be made equal to or greater than the amount of refrigerant flowing through the second refrigerant pipe. That is, the main flow of refrigerant can be directed to the first refrigerant pipe side.

Further, in the refrigerator according to the reference aspect of the present invention, a switching means capable of switching a flow direction at the branch portion of the first refrigerant pipe is provided, and the control portion switches the refrigerant when the on-off valve is closed. The switching means is controlled so as not to guide the refrigerant to the second refrigerant pipe side, and the switching means is controlled to guide the refrigerant to the second refrigerant pipe side when the on-off valve is in an open state.

According to the refrigerator according to this aspect, the control unit can switch whether the entire amount of refrigerant is directed to the oil separator or bypassed by the switching means, and when the on-off valve is open, the refrigerant is directed to the second refrigerant pipe side. so that the refrigerant is not guided to the second refrigerant pipe side when the on-off valve is closed. Thus, when the on-off valve is closed (that is, under normal load and no oil is returned from the oil separator to the compressor), the entire amount of refrigerant bypasses the oil separator. Therefore, since the oil does not accumulate in the oil separator, it is not necessary to periodically return the oil from the oil separator to the compressor, and the frequency of the phenomenon in which the refrigerant returns from the oil separator to the compressor can be further reduced.
On the other hand, when the on-off valve is open (that is, when the oil separator is in an overload state and the oil is returned to the compressor from the oil separator), the entire amount of refrigerant is led to the oil separator. As a result, the oil can be accumulated in the oil separator in a short period of time. Therefore, the required amount of oil in the compressor can be secured in a short time. In addition, even in an overload condition where a large amount of oil is discharged from the compressor, the oil contained in the refrigerant can be separated by the oil separator, so the heat in the heat exchanger (e.g. condenser) installed downstream can be reduced. Reduction in exchange efficiency can be suppressed.
As the switching means, for example, a three-way valve provided at the branching portion of the first refrigerant pipe, the first refrigerant pipe between the branching portion and the merging portion, and the second refrigerant pipe between the branching portion and the oil separator There are two on-off valves provided in the

Further, in the refrigerator according to one aspect of the present invention, the oil return pipe includes a bypass pipe that connects the upstream side and the downstream side of the on-off valve.

In the refrigerator according to this aspect, the oil return pipe includes a bypass pipe that connects the upstream side and the downstream side of the on-off valve. This forms a circuit that bypasses the on-off valve. By setting the diameter of the bypass pipe to such an extent that only the oil flows, for example, only the oil can be returned from the oil separator to the compressor. Therefore, the frequency of periodically returning oil from the oil separator to the compressor can be reduced.

Further, when the rotation speed of the compressor is equal to or lower than a predetermined rotation speed, the control unit determines that the compressor is in a load state during normal operation or in a lower load state, and the predetermined rotation speed is exceeded. It is determined that the compressor is overloaded more than the load condition during normal operation.

The control unit can acquire the load state of the compressor from the rotation speed of the compressor.

Further, when the pressure difference between the suction side and the discharge side of the compressor is equal to or less than a predetermined pressure, the control unit determines that the compressor is in a load state during normal operation or a load state lower than that, and When the pressure is exceeded, the compressor is determined to be overloaded relative to its normal operating load.

The control unit can acquire the load state of the compressor from the pressure difference between the suction side and the discharge side of the compressor.

Moreover, the chiller installation which concerns on one aspect|mode of this invention is equipped with the above-mentioned refrigerator.

ADVANTAGE OF THE INVENTION According to the refrigerator and the chiller equipment provided with the same according to the present invention, it is possible to secure the amount of oil in the compressor without increasing the amount of oil to be charged, and to suppress the phenomenon that the refrigerant returns to the compressor from the oil separator. .

It is a figure showing a refrigerant circuit of a freezer concerning a 1st embodiment of the present invention. It is the figure which showed the refrigerant circuit of the refrigerator which concerns on 2nd Embodiment of this invention. It is the figure which showed the modification of the refrigerant circuit of the refrigerator which concerns on 2nd Embodiment of this invention.

A refrigerator according to an embodiment of the present invention will be described below with reference to the drawings. In addition, the refrigerator of this embodiment is a refrigerator employ|adopted as chiller equipment, for example.

[First embodiment]
First, a refrigerator according to a first embodiment of the present invention will be described.

FIG. 1 shows a refrigerant circuit of a refrigerator according to this embodiment. The refrigerant circuit of the refrigerator includes a compressor 10 that compresses the refrigerant, a condenser 12 that condenses the refrigerant, an expansion valve 14 that expands the refrigerant, an evaporator 16 that evaporates the refrigerant, and the refrigerant discharged from the compressor 10. and an oil separator 18 for separating oil contained in the refrigerant. In this refrigerant circuit, these devices are connected by a refrigerant pipe P1, a refrigerant pipe P2, a refrigerant pipe P3, a refrigerant pipe P4, a refrigerant pipe P5, and an oil return pipe P6. In addition, the refrigerator includes a control unit 30 capable of communicating with each device and controlling each device.

The compressor 10 is a device that compresses the refrigerant guided from the evaporator 16 . The compressor 10 is filled with oil in advance to lubricate the sliding parts. A discharge port of the compressor 10 is connected to a refrigerant inlet of the condenser 12 via a first refrigerant pipe P1.

The condenser 12 is a heat exchanger that condenses the refrigerant compressed by the compressor 10 by heat exchange. A refrigerant outlet of the condenser 12 is connected to a refrigerant inlet of the expansion valve 14 via a refrigerant pipe P3.

The expansion valve 14 is a device that expands the refrigerant condensed in the condenser 12 . A refrigerant outlet of the expansion valve 14 is connected to a refrigerant inlet of the evaporator 16 via a refrigerant pipe P4.

The evaporator 16 is a heat exchanger that evaporates the refrigerant expanded by the expansion valve 14 by heat exchange. A refrigerant outlet of the evaporator 16 is connected to a suction port of the compressor 10 via a refrigerant pipe P5.

A second refrigerant pipe P2 is connected in the middle of the first refrigerant pipe P1. A connection portion between the first refrigerant pipe P<b>1 and the second refrigerant pipe P<b>2 is a branch portion 40 . The second refrigerant pipe P<b>2 branched from the first refrigerant pipe P<b>1 at the branching portion 40 is reconnected to the first refrigerant pipe P<b>1 at the junction 42 downstream of the branching portion 40 . In addition, it is preferable that the pipe diameter of the first refrigerant pipe P1 is equal to or larger than the pipe diameter of the second refrigerant pipe P2.

An oil separator 18 is provided in the middle of the second refrigerant pipe P2. The second refrigerant pipe P2 is divided into an upstream second refrigerant pipe P2A and a downstream second refrigerant pipe P2B on the upstream side and the downstream side of the oil separator 18 . In the following description, when it is necessary to distinguish the second refrigerant pipe P2 between the upstream side and the downstream side of the oil separator 18, the term "upstream side second refrigerant pipe P2A" or "downstream side second refrigerant pipe P2B" is used. to use. On the other hand, when no distinction is required, the term "second refrigerant line P2" will simply be used.

The oil separator 18 is a device that separates oil contained in the refrigerant discharged from the compressor 10 from the refrigerant. An outlet of the oil separator 18 is connected to the compressor 10 via an oil return pipe P6. An on-off valve 20 is provided in the oil return pipe P6.

The control unit 30 is a device that can communicate with each device described above and can execute control. storage medium, etc. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example, and the CPU reads out this program to a RAM or the like, and executes information processing and arithmetic processing. As a result, various functions are realized. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or delivered via wired or wireless communication means. etc. may be applied. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like.

Next, the flow of refrigerant in the refrigerant circuit will be described.
Refrigerant compressed by the compressor 10 is guided to the first refrigerant pipe P1. A portion of the refrigerant that has reached the branch portion 40 flows through the second upstream refrigerant pipe P2A and is guided to the oil separator 18 . On the other hand, the remaining refrigerant flows through the first refrigerant pipe P<b>1 as it is and is led to the condenser 12 .

At this time, as described above, by setting the pipe diameter of the first refrigerant pipe P1 to be equal to or larger than the pipe diameter of the second refrigerant pipe P2, the amount of refrigerant guided to the condenser 12 is reduced to the upstream second refrigerant pipe P2A (total That is, it can be larger than the amount of refrigerant introduced to the oil separator 18). That is, the main flow of refrigerant can be on the side of the first refrigerant pipe P1 instead of the side of the second refrigerant pipe P2.

The refrigerant guided to the condenser 12 is heat-exchanged by the condenser 12 and condensed. The refrigerant condensed in the condenser 12 flows through the third refrigerant pipe P3 and is led to the expansion valve 14 .

The refrigerant guided to the expansion valve 14 is expanded by the expansion valve 14 . The refrigerant expanded by the expansion valve 14 flows through the fourth refrigerant pipe P<b>4 and is led to the evaporator 16 .

The refrigerant guided to the evaporator 16 undergoes heat exchange by the evaporator 16 and evaporates. A heat medium (for example, water) that has exchanged heat with the refrigerant here is supplied as chiller water. The refrigerant evaporated in the evaporator 16 flows through the fifth refrigerant pipe P5 and is led to the compressor 10 again.

Oil contained in the refrigerant that flows through the second upstream refrigerant pipe P2A and is led to the oil separator 18 is separated by the oil separator 18 . The separated oil accumulates below the oil separator 18 . In general, when the load state of the compressor 10 is the load state during normal operation (hereinafter referred to as the “normal load state”) or a load state lower than the normal load state, the oil discharged from the compressor 10 (contained in the refrigerant) The amount of oil discharged from the On the other hand, the amount of oil discharged from the compressor 10 is larger in the overloaded state than in the normal loaded state. In other words, as the load on the compressor 10 increases, the amount of oil discharged from the compressor 10 increases.

The refrigerant from which the oil has been removed flows through the second upstream refrigerant pipe P2A and joins the first refrigerant pipe P1 at the junction 42 . The merged refrigerant is guided to the condenser 12 together with the refrigerant flowing through the first refrigerant pipe P<b>1 without passing through the oil separator 18 .

On the other hand, the oil stored in the lower part of the oil separator 18 can be returned to the compressor 10 via the oil return pipe P6. This oil may contain a small amount of refrigerant compressed by the compressor 10 without being separated.

Next, control of the on-off valve 20 provided in the oil return pipe P6 will be described.

The on-off valve 20 is controlled (for example, opened and closed) by the controller 30 according to the load state of the compressor 10 . The load state of the compressor 10 changes according to, for example, the water temperature and outside air temperature set in the chiller equipment.

Next, control of the on-off valve 20 will be described in detail.
The on-off valve 20 is closed when the load state of the compressor 10 is a normal load state or a lower load state than the normal load state. In other words, the oil return pipe P6 is cut off, and the oil is not returned to the compressor 10. Conversely, when the load state of the compressor 10 is in an overload state rather than the normal load state, the on-off valve 20 is opened. In other words, the oil return pipe P6 is not blocked, and the oil can be returned to the compressor 10.

Here, the load state of the compressor 10 is determined as follows.
The control unit 30 can obtain the rotation speed of the compressor 10. For example, the rotation speed of the compressor 10 is obtained from an inverter (not shown) that changes the rotation speed of the electric motor that drives the compressor 10. . At this time, when the rotation speed of the compressor 10 is equal to or less than the predetermined rotation speed, the control unit 30 determines that the compressor 10 is in the normal load state or the low load state. Also, when the rotation speed of the compressor 10 exceeds a predetermined rotation speed, the control unit 30 determines that the compressor 10 is in an overloaded state. The predetermined rotation speed is, for example, a rotation speed at which the amount of oil contained in the refrigerant discharged from the compressor 10 is about 5% of the total amount (refrigerant and oil), a rotation speed at about 50% of the upper limit rotation speed, or the like. be. However, these rotation speeds differ depending on the specifications of the compressor 10 .

Moreover, the load state of the compressor 10 may be determined as follows.
The control unit 30 can acquire the pressure on the discharge side and the pressure on the suction port side of the compressor 10. For example, the pressure on the discharge side and the pressure on the suction port side can be obtained from a pressure gauge (not shown) provided on the refrigerant pipe. obtained from At this time, when the differential pressure between the discharge port side and the suction port side is equal to or less than a predetermined pressure, the control unit 30 determines that the compressor 10 is in the normal load state or the low load state. Also, when the differential pressure exceeds a predetermined pressure, the control unit 30 determines that the compressor 10 is in an overloaded state. The predetermined pressure is, for example, the pressure based on the design pressure ratio of the compressor 10, the pressure based on the differential pressure (2.0 MPa to 2.2 MPa) under the heating rating condition with R410 refrigerant (as an example), or the like. However, these pressures differ depending on the specifications of the compressor 10 .

Note that the criterion for determining the load state of the compressor 10 is not limited to the aforementioned criterion, and may be determined based on the water temperature of the heat exchanger or the outside air temperature.

This embodiment has the following effects.
The oil separated by the oil separator 18 may contain a small amount of refrigerant compressed by the compressor 10 . That is, if the oil is returned to the compressor 10 as it is, the compressed refrigerant will inevitably be returned from the oil separator 18 to the compressor 10 via the oil return pipe P6. This inevitably returned refrigerant does not exchange heat in the condenser 12 and thus becomes a loss to the work of the compressor 10 . However, when the oil return pipe P6 is blocked by the on-off valve 20, the phenomenon in which part of the refrigerant returns from the oil separator 18 to the compressor 10 is suppressed, so the loss of work of the compressor 10 can be suppressed.

In addition, since the amount of oil discharged from the compressor 10 (oil contained in the refrigerant and discharged) is small in a normal load state or a low load state, the oil return pipe P6 is blocked by the on-off valve 20 to compress the oil. Even if the oil is not returned to the compressor 10, the effect on the compressor 10 (for example, lack of oil) is negligible. On the other hand, when the compressor is overloaded, a large amount of oil is discharged from the compressor 10 . Therefore, if the oil return pipe P6 is blocked by the on-off valve 20, there is a possibility that the compressor 10 will run out of oil. However, by opening the on-off valve 20 provided in the oil return pipe P6 when the overload state is higher than the normal load state, the oil stored in the oil separator 18 can be returned to the compressor 10. , the amount of oil in the compressor 10 can be ensured. Therefore, there is no need to increase the amount of oil to fill the compressor 10 in order to make up for the shortage of oil in the compressor 10 that occurs when the compressor is overloaded.

Also, if all of the refrigerant passes through the oil separator 18, the oil will accumulate in the oil separator 18 in a short period of time. On the other hand, most of the refrigerant is led from the compressor 10 to the condenser 12 through the first refrigerant pipe P1, and the amount of refrigerant led to the oil separator 18 is relatively small. It is possible to lengthen the time required for the oil to accumulate in the That is, in order to reduce the amount of oil accumulated in the oil separator 18, the frequency of returning the oil from the oil separator 18 to the compressor 10 can be reduced. As a result, the frequency of the phenomenon in which the compressed refrigerant returns from the oil separator 18 to the compressor 10 can be reduced, so the loss of work of the compressor 10 can be suppressed.

[Second embodiment]
Next, a refrigerator according to a second embodiment of the present invention will be described. This embodiment is different from the first embodiment in the form of the vicinity of the branching portion 40, and is the same in other respects. Therefore, only the points different from the first embodiment will be described, and the description of other points will be omitted by using the same reference numerals.

FIG. 2 shows a refrigerant circuit of a refrigerator according to a second embodiment of the invention.
Unlike the first embodiment, a three-way valve 22 is provided as switching means capable of switching the flow direction at the branch portion 40 .

The three-way valve 22 can switch the flow direction so as to guide the refrigerant introduced from the compressor 10 to either the first refrigerant pipe P1 or the upstream second refrigerant pipe P2A. In other words, the refrigerant guided from the compressor 10 can be switched to bypass or pass through the oil separator 18 (second refrigerant pipe P2).

In addition, when the switching means is provided, the pipe diameter of the 1st refrigerant|coolant piping P1 does not need to be more than the pipe diameter of the 2nd refrigerant|coolant piping P2.

The three-way valve 22 is controlled as follows.
The control unit 30 can acquire the open/closed state of the on-off valve 20 . When the on-off valve 20 is closed (that is, when the compressor 10 is in a normal load state or a low load state), the controller 30 controls the three-way valve 22 so as not to guide the refrigerant to the oil separator 18 . Conversely, when the on-off valve 20 is open (that is, when the compressor 10 is overloaded), the controller 30 controls the three-way valve 22 so as to guide the refrigerant to the oil separator 18 .

The switching means capable of switching the flow direction at the branching portion 40 is not limited to the three-way valve 22 described above, and may be, for example, two on-off valves 24 and 26 as shown in FIG. . In this case, one on-off valve 24 is provided in the first refrigerant pipe P1 between the branching portion 40 and the merging portion 42, and the multi-way on-off valve 26 is provided in the second upstream refrigerant pipe P2A.

This embodiment has the following effects.
When the on-off valve 20 is closed (ie, when the compressor 10 is under normal load and no oil is being returned to the compressor 10 from the oil separator 18 ), all of the refrigerant bypasses the oil separator 18 . Therefore, since oil does not accumulate in the oil separator 18, there is no need to periodically return the oil from the oil separator 18 to the compressor 10, thereby further reducing the frequency of the phenomenon in which the refrigerant returns from the oil separator 18 to the compressor 10. can.

On the other hand, when the on-off valve 20 is open (that is, when the compressor 10 is overloaded and oil is returned from the oil separator 18 to the compressor 10 ), the entire amount of refrigerant is led to the oil separator 18 . As a result, the oil can be stored in the oil separator 18 in a short period of time. Therefore, the necessary amount of oil in the compressor 10 can be secured in a short time. In addition, even in an overload state where a large amount of oil is discharged from the compressor 10, the oil contained in the refrigerant can be separated by the oil separator 18, so the efficiency of heat exchange in the condenser 12 installed downstream Decrease can be suppressed.

In addition, in the first embodiment and the second embodiment, as shown in FIG. 3, a bypass pipe P7 connecting the upstream side and the downstream side of the on-off valve 20 may be provided. The bypass pipe P7 has a pipe diameter that allows only oil to flow, and employs, for example, a capillary tube. In this case, only oil can be returned from the oil separator 18 to the compressor 10 . Therefore, the frequency of periodically returning oil from the oil separator 18 to the compressor 10 can be reduced.

10 Compressor 12 Condenser 14 Expansion valve 16 Evaporator 18 Oil separator 20 On-off valve 22 Three-way valve (switching means)
24, 26 Open/close valve (switching means)
30 control part 40 branch part 42 confluence part P1 first refrigerant pipe P2A (P2) second upstream refrigerant pipe (second refrigerant pipe)
P2B (P2) Downstream side second refrigerant pipe (second refrigerant pipe)
P3, P4, P5 Refrigerant pipe P6 Oil return pipe P7 Bypass pipe

Claims (7)

a compressor that compresses a refrigerant;
a condenser for condensing the refrigerant compressed by the compressor;
a first refrigerant pipe connecting the compressor and the condenser;
a second refrigerant pipe branching from the first refrigerant pipe at a branching portion and joining the first refrigerant pipe again downstream of the branching portion;
an oil separator provided in the second refrigerant pipe and separating oil in the refrigerant;
an oil return pipe returning the oil separated by the oil separator to the compressor;
an on-off valve provided in the oil return pipe;
a control unit that switches between opening and closing of the on-off valve according to the load state of the compressor;
with
A refrigerator in which the first refrigerant pipe and the second refrigerant pipe are not provided with a valve for switching the flow direction of the refrigerant at the branch portion. The control unit closes the on-off valve when the compressor is in a load state during normal operation or in a load state lower than that, and the compressor is in an overload state rather than in a load state during normal operation. 2. The refrigerator according to claim 1, wherein the on-off valve is opened at times. The refrigerator according to claim 1 or 2, wherein the first refrigerant pipe has a diameter equal to or larger than that of the second refrigerant pipe. 4. The refrigerator according to any one of claims 1 to 3 , wherein the oil return pipe includes a bypass pipe that connects upstream and downstream sides of the on-off valve. The control unit determines that the compressor is in a load state or a lower load state during normal operation when the rotational speed of the compressor is equal to or lower than a predetermined rotational speed, and determines that the compressor is in a load state lower than that during normal operation, 5. The refrigerator according to any one of claims 1 to 4 , wherein the compressor is determined to be in an overload state rather than a load state during normal operation. When the pressure difference between the suction side and the discharge side of the compressor is equal to or less than a predetermined pressure, the control unit determines that the compressor is in a load state during normal operation or a load state lower than that, and reduces the predetermined pressure. 5. The refrigerator according to any one of claims 1 to 4 , wherein the compressor is determined to be in an overload state higher than the load state during normal operation when the load exceeds the load state. Chiller equipment comprising the refrigerator according to any one of claims 1 to 6 .

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