JP2002122363A - Refrigeration equipment - Google Patents

Abstract

(57) An object of the present invention is to provide a refrigeration apparatus in which the degree of supercooling of a refrigerant at a suction port of a liquid refrigerant transfer device is maintained at a predetermined value or more to prevent cavitation. A refrigeration apparatus for circulating a refrigerant in a refrigerant circuit in which a liquid refrigerant transport device, a refrigerant vaporizer, and a refrigerant liquefier are sequentially connected to a refrigerant circuit, wherein a liquid refrigerant state at a suction port of the liquid refrigerant transport device is the liquid refrigerant transport. A cavitation detection device that determines whether or not cavitation may occur inside the device, and when it is determined that cavitation may occur by the cavitation detection device,
A cavitation preventing device for changing the state of the liquid refrigerant at the suction port of the liquid refrigerant transport device to a state in which cavitation does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus using a liquid refrigerant transfer device.

[0002]

2. Description of the Related Art As a conventional example of a refrigerating apparatus using a liquid refrigerant conveying apparatus, there is one disclosed in Japanese Patent Application Laid-Open No. 7-35422. This refrigeration system includes a cooling operation for performing cooling by a normal refrigeration cycle, a cold storage operation for storing cold heat in a heat storage tank, a cold storage operation for performing cooling (cooling) using the stored cold heat (cooling operation using cooling), A refrigerating apparatus including each operation mode of a combined cooling / cooling operation in which a cycle during a cooling operation and a cycle using a cold storage operation are simultaneously formed. FIG. 18 shows a refrigerant circuit diagram in the cold storage use operation of the refrigeration apparatus. In this figure, the thick solid line indicates the portion where the refrigerant circulates during the cold storage operation, that is, the refrigerant circuit Rc during the cold storage operation, and the thin solid line indicates the portion where the refrigerant circulates during another operation mode.

As shown in FIG. 1, a conventional refrigeration system includes a compressor 101, a condenser 103, a subcooler
4, a main refrigerant circuit is configured by sequentially connecting the expansion valve 111, the on-off valve 112, the use side heat exchanger (refrigerant vaporizer) 2, and the accumulator 102. The cooling operation for performing cooling by the refrigeration cycle is performed.

[0004] Further, an on-off valve 11 is provided for the main refrigerant circuit.
The check valve 123, the refrigerant liquid pump 1 as a liquid refrigerant transport device, and the regenerator in the regenerator 103a are cooled and stored in parallel with the circuit connecting the heat exchanger 2 and the use-side heat exchanger (refrigerant vaporizer) 2. A heat exchanger for cold storage (during cold storage operation, this cold storage heat serves as a cold heat source for condensing the refrigerant and thus serves as a refrigerant liquefaction device) 3 is connected in series. Further, in this circuit, a check valve 124 is connected in parallel to the check valve 123 and the refrigerant liquid pump 1.

[0005] In the cold storage operation, the on-off valve 112 is closed and the expansion valve 1 is closed.
11 is set to the refrigerant control state, the operation of the refrigerant liquid pump 1 is stopped, and the compressor 101 is driven.
The refrigerant discharged from the condenser 103, the subcooler 104,
It is performed by flowing through the expansion valve 111, the check valve 124, the heat exchanger for cold storage 3, and the accumulator 102, and the cold storage tank 3a
Cold heat accumulates inside.

[0006] In the cold storage operation, the expansion valve 111 is closed, the on-off valve 112 is opened, the operation of the compressor 101 is stopped, and the refrigerant liquid pump 1 is driven. Valve 123, on-off valve 112, use side heat exchanger (refrigerant vaporizer) 2, cool storage heat exchanger (refrigerant liquefier)
3. The liquid refrigerant is circulated in the order of the refrigerant liquid pump 1 (in the order of the solid line arrows in the figure), and cooling is performed using the cold storage heat stored in the cold storage tank 3a. The refrigerant circuit at this time is the refrigerant circuit Rc during the cold storage operation.

[0007] In the combined cooling and storage operation, the on-off valve 112 is opened,
By setting the expansion valve 111 to the refrigerant control state and driving the compressor 101 and the refrigerant liquid pump 1, the flow of the refrigerant by the refrigerant circuit Rc at the time of the cold storage operation and the flow of the refrigerant at the time of the normal cooling operation are simultaneously performed. In addition, a combined cooling / cooling operation in which the cold storage heat stored in the cold storage tank 3a is additionally used as a heat source for cooling is performed.

A bypass circuit having an on-off valve 126 and a capillary tube 127 is provided between the outlet of the compressor 101 and the suction side of the accumulator 102. The pressure on the side can be increased. Also, 131 is a pressure sensor, 132 is a liquid level sensor, and 133 is a heat exchanger 3 for cold storage.
Is a temperature sensor for detecting the outlet refrigerant temperature, 107 is a control device, 108 is a compressor driving device, and 109 is a remote controller.

In this refrigeration system, the following control is performed in order to appropriately maintain the cooling capacity during the above-described cold storage operation. From the refrigerant pressure detected by the pressure sensor 131 and the refrigerant temperature at the outlet of the cool storage heat exchanger 3 detected by the temperature sensor 133, the heat storage heat exchanger 3
The supercooling degree at the outlet, that is, the supercooling degree of the liquid refrigerant on the suction side of the refrigerant liquid pump 1 is detected. When the degree of supercooling at the outlet of the heat exchanger for cold storage 3 exceeds a predetermined value, the control device 107 operates the compressor 101 to operate the accumulator 1.
When the actual degree of supercooling reaches a predetermined value, the compressor is stopped. When the actual degree of subcooling becomes smaller than the predetermined value, the expansion valve 111 is opened to open the condenser (heat source). When the actual degree of supercooling returns to a predetermined value, the expansion valve 111 is closed, and the supercooling degree at the outlet of the cool storage heat exchanger 3 is set to a predetermined value. Control is performed so as to maintain the refrigerant amount in the refrigerant circuit Rc properly, and the cooling capacity during the heat storage utilization operation is appropriately maintained.

[0010]

However, in the above-mentioned conventional refrigeration system, no consideration is given to ensuring the reliability of the refrigerant liquid pump 1 for preventing the occurrence of cavitation at the suction port of the refrigerant liquid pump 1. .

Generally, when a portion below the saturated vapor pressure locally occurs due to a change in flow velocity, generation of a vortex, a flow path obstacle, or the like inside a fluid device, a phenomenon in which the liquid in that portion is vaporized to generate hollow bubbles. That is, cavitation occurs. In the refrigerant circuit Rc at the time of the heat storage utilization operation for transporting the liquid refrigerant as described above, the pressure tends to be lowest at the suction port of the normal liquid refrigerant transport device (refrigerant liquid pump) 1 and cavitation is likely to occur. Then, when cavitation occurs and gas refrigerant flows into the refrigerant liquid pump 1 even a little, the amount of refrigerant conveyed is greatly reduced, and eventually a problem that almost no refrigerant is conveyed is caused. Further, vibration and noise are generated with the occurrence of cavitation. If this state continues for a long time, the material in the refrigerant liquid pump 1 will be eroded and the mechanical part will be damaged, causing the refrigerant liquid pump 1 to malfunction.

By the way, in the above-mentioned conventional refrigeration system,
The degree of supercooling on the suction side of the refrigerant liquid pump 1 (the heat exchanger 3 for cold storage)
The reason why the degree of supercooling at the outlet is controlled to be constant is that the amount of refrigerant in the refrigerant circuit Rc is appropriately maintained as described above to maintain the cooling capacity constant. Not to prevent cavitation. Further, the predetermined degree of supercooling set for this purpose is set for optimizing the cooling capacity, and does not mention prevention of cavitation.

For this reason, in the case of adjusting the amount of refrigerant in the refrigerant circuit Rc in the refrigerant circuit Rc at the time of cold storage operation as in the above-mentioned conventional refrigeration system, cavitation at the suction port of the refrigerant liquid pump 1 is performed. It is necessary to monitor and control the state of the refrigerant at the suction port of the liquid refrigerant transport device (refrigerant liquid pump) 1 so as not to cause the generation.

The present invention has been made by paying attention to such problems existing in the prior art. It is an object of the present invention to provide a refrigeration apparatus that prevents the occurrence of cavitation by maintaining the degree of supercooling of a refrigerant at a suction port of a liquid refrigerant transport device at a predetermined value or more.

[0015]

In order to achieve the above object, a refrigeration apparatus according to the present invention has a refrigeration system in which a refrigerant is circulated through a refrigerant circuit in which a liquid refrigerant conveying device, a refrigerant vaporizer, and a refrigerant liquefier are sequentially connected. A cavitation detection device that determines whether or not the liquid refrigerant state at a suction port of the liquid refrigerant conveyance device may cause cavitation inside the liquid refrigerant conveyance device, and performs cavitation by the cavitation detection device. And a cavitation preventing device that changes the state of the liquid refrigerant at the suction port of the liquid refrigerant transport device to a state in which cavitation does not occur when it is determined that the cavitation may occur.

The cavitation detection device may determine that cavitation may occur when the degree of supercooling detected for the refrigerant near the suction port of the liquid refrigerant transfer device is smaller than the degree of supercooling corresponding to the required NPSH. It may be determined.

Further, the cavitation detecting device may include:
When the detected input current value of the liquid refrigerant transport device is out of the predetermined range, it may be determined that cavitation may occur.

Further, the cavitation detecting device may include:
When the detected noise or vibration value of the liquid refrigerant transport device is out of the predetermined range, it may be determined that cavitation may occur.

Further, the cavitation detecting device includes:
When the difference between the heat exchange amount estimated from the refrigerant transfer amount of the liquid refrigerant transfer device and the heat exchange amount estimated from the medium temperature flowing into and out of the refrigerant vaporizer falls outside a predetermined range,
It may be determined that cavitation may occur.

Further, the cavitation preventing device comprises:
From a refrigerant tank arranged outside the system of the refrigerant circuit,
A liquid refrigerant may be supplied between the liquid refrigerant conveying device and the refrigerant liquefaction device.

[0021] The cavitation prevention device may increase the heat exchange amount of the refrigerant liquefaction device.

Further, the cavitation preventing device includes:
The amount of heat exchange of the refrigerant vaporizer may be reduced.

[0023] The cavitation preventing device may include:
The flow rate of the liquid refrigerant transport device may be reduced.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a refrigerating apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 is a schematic configuration diagram of a refrigeration system according to Embodiment 1, FIG. 2 is a specific configuration diagram of a refrigerant liquefaction device according to FIG. 1, and FIG. 3 is a refrigeration system according to FIG. FIG. 4 is a diagram illustrating the principle of a cavitation detecting device in the refrigeration apparatus according to FIG. 1, and FIG. 5 is a control flowchart of the cavitation detecting device in the refrigeration apparatus according to FIG. In these figures, the same or corresponding elements as those in the related art are denoted by the same reference numerals, so that the relation can be easily understood.

As shown in FIG. 1, in the refrigerating apparatus according to the first embodiment, a liquid refrigerant transport apparatus 1 for transporting a liquid refrigerant cools an object to be cooled (for example, indoor air to be cooled) by the cooled liquid refrigerant. The refrigerant vaporizer 2 is connected to the refrigerant vaporizer 2 and the refrigerant liquefier 3 is turned into a supercooled liquid refrigerant by cooling the gas refrigerant or the gas-liquid two-phase refrigerant vaporized by the refrigerant vaporizer 2. The circuit Rc is configured. 4
Is a refrigerant tank that is disposed outside the system of the refrigerant circuit Rc and stores a liquid refrigerant having a predetermined pressure or higher. The refrigerant tank 4 is connected to the liquid refrigerant transfer device 1 through the on-off valve 6 by the communication pipe 5. It is connected near the suction port. In addition, the total head of the refrigerant tank 4 is set to be larger than the total head of the suction port of the liquid refrigerant transport device 1 when the liquid refrigerant flows through the communication pipe 5.

FIG. 2 shows a specific configuration of the refrigerant liquefaction apparatus 3. As shown in FIG. 2, the refrigerant liquefaction apparatus 3 has a heat storage material 3b such as water inside a heat storage tank 3a, and further has a heat exchanger 3c for cooling a refrigerant so as to exchange heat with the heat storage material 3b. The heat storage material cooling heat exchanger 3d is provided. In this case, the heat storage material cooling heat exchanger 3d is
7 is an evaporator of a refrigerating apparatus of another system formed to cool b.

In FIG. 1, a temperature sensor 11 and a pressure sensor 12 for detecting the temperature and the pressure of the refrigerant flowing through the suction port of the liquid refrigerant transfer device 1 are provided. As will be described later, the cavitation detecting device includes a temperature sensor 11 and a pressure sensor 12.
Is transmitted to the control device 7, the degree of supercooling of the refrigerant near the suction port of the liquid refrigerant transport device 1 is calculated, and based on the calculated degree of supercooling, the liquid refrigerant transport device 1 It is determined whether or not the state of the refrigerant at the suction port may cause cavitation inside the liquid refrigerant transport device 1. Further, based on an operation command from the cavitation detecting device, the on-off valve 6 is controlled to open and close as an operation of the cavitation preventing device.

In the first embodiment, the cavitation detecting device detects that the refrigerant state of the suction port of the liquid refrigerant conveying device 1 is
This is for determining whether or not cavitation may be generated inside the liquid refrigerant transport device 1, and includes a control device 7, a temperature sensor 11, and a pressure sensor 12. When the cavitation detection device determines that cavitation may occur, the cavitation prevention device that changes the liquid refrigerant state at the suction port of the liquid refrigerant transport device 1 to a state in which cavitation does not occur is provided by a driving device. 8, refrigerant tank 4, communication pipe 5,
It is constituted by an on-off valve 6.

Next, the operation of the cooling operation by the refrigeration system will be described. Since the cycle of the dotted line in FIG. 3 conceptually represents a refrigeration cycle during the cooling operation with the above configuration, the cycle will be described with reference to this figure. The cooling operation using the cold storage heat is performed by closing the on-off valve 6 and driving the liquid refrigerant transport device 1. The high-pressure liquid refrigerant (point A) flowing out from the discharge port of the liquid refrigerant transport device 1
The refrigerant flows into the refrigerant vaporizer 2 while being decompressed by the pipe flow resistance. The refrigerant that has flowed into the refrigerant vaporizer 2 exchanges heat with a high-temperature surrounding medium (in the above-described example, indoor air) and evaporates while being depressurized by the refrigerant flow resistance in the heat exchanger, and evaporates. The refrigerant becomes a large two-phase refrigerant and flows out of the refrigerant vaporizer 2 (point B). The refrigerant flowing out of the refrigerant vaporizer 2 is decompressed by the pipe flow resistance and flows into the refrigerant liquefier 3 (point C). The refrigerant here is decompressed by the refrigerant flow resistance in the heat exchanger and is cooled by a surrounding medium having a low temperature (the heat storage material 3b in the above-described example, and the heat storage material 3b is cold water partially frozen). Exchange and condense, supercool and drain. The refrigerant that has flowed out is reduced in pressure by the refrigerant flow resistance in the pipe, and flows into the suction port of the liquid refrigerant transport device 1 (point D).

Next, before describing the operation of the cavitation detecting device and the cavitation preventing device,
A description will be given of what the state of the liquid refrigerant at the suction port of the liquid refrigerant transport device 1 means that may cause cavitation. In order to examine whether the state of the liquid refrigerant at the suction port of the liquid refrigerant transport device 1 may cause cavitation inside the liquid refrigerant transport device 1 and cause a failure of the liquid refrigerant transport device, According to the “Refrigeration and Air Conditioning Handbook Volume 2 Equipment Edition” issued by the Japan Refrigeration Association (issued June 25, 1993), NPSH (ne
The concept of "t positivesuction head" is generally used. The NPSH has an effective suction head (Hsv) and a required suction head (hsv).

The effective suction head (Hsv) is an NPSH that can be effectively used by the liquid refrigerant transfer device 1 in view of the installation conditions of the liquid refrigerant transfer device 1, and is determined regardless of the characteristics of the liquid refrigerant transfer device 1. This indicates how high the refrigerant pressure immediately before the suction port of the liquid refrigerant transport device 1 is higher than the saturated vapor pressure of the refrigerant immediately before the suction port of the liquid refrigerant transport device 1. Further, the required suction head (hsv) is a unique NPSH required by the liquid refrigerant transport device 1, and in order for the liquid refrigerant transport device 1 to operate safely without generating cavitation, the following formula 1 is always used. You need to maintain a relationship.

[0032]

Hsv> hsv + α Here, α is a margin in consideration of the degree of safety and is a value determined for each liquid refrigerant transfer device 1, but α = 0 in the following description.

Therefore, in the above case, the determination is made using the refrigerant pressure immediately before the suction port of the liquid refrigerant transport device 1, the saturated vapor pressure of the refrigerant immediately before the suction port of the liquid refrigerant transport device 1, and the required suction head (hsv). In other words, as a simple alternative, this can be determined using the degree of supercooling of the refrigerant. This will be further described below.

First, regarding the effective suction head (Hsv), the refrigerant pressure at the suction port of the liquid refrigerant transfer device 1
Instead of comparing the saturated vapor pressure of the refrigerant at the suction port of the liquid refrigerant transfer device 1, the degree of supercooling of the refrigerant at the suction port of the liquid refrigerant transfer device 1 and the saturated vapor temperature of the refrigerant at the suction port of the liquid refrigerant transfer device 1 Can be replaced by comparing

That is, in the Ph diagram of FIG. 4, the state of the refrigerant at the suction port of the liquid refrigerant transport device 1 is point A. Then, the saturated vapor point at the same temperature as the point A is referred to as a point B,
A saturated vapor point having the same pressure as that of the point A is represented by a point C. In this case, the effective suction head (Hsv) is, as described above, how much the refrigerant pressure immediately before the suction port of the liquid refrigerant conveyance device 1 is higher than the saturated vapor pressure of the refrigerant immediately before the suction port of the liquid refrigerant conveyance device 1. Therefore, the pressure difference ΔPab between the point A and the point B is obtained. The degree of supercooling Tca at the point A is represented by the temperature difference between the points A and C in FIG. Then, there is a certain correlation between the pressure difference and the degree of supercooling, such that when one increases, the other also increases. Therefore, the effective suction head (Hsv) can be represented by the degree of supercooling Tca at the point A.

Next, the required suction head (hsv) will be described. First, the required suction head (hsv) is set as a pressure difference ΔPn. Then, regarding the degree of supercooling of the refrigerant at the suction port of the liquid refrigerant transport device 1 corresponding to the pressure difference ΔPn, the degree of subcooling of the liquid refrigerant at the suction port of the liquid refrigerant transport device 1 under the assumed several operating conditions is calculated. Take
The average value Tcn is obtained. This Tcn becomes substantially equal to the degree of supercooling corresponding to the pressure difference ΔPn corresponding to the required suction head (hsv). Therefore, this Tcn is regarded as the degree of supercooling corresponding to the required suction head (hsv). By doing as described above, the above equation 1 can be replaced with the following equation 2.

[0037]

## EQU2 ## Subcooling degree Tca of refrigerant at the suction port of liquid refrigerant transport device 1> Supercooling degree Tcn corresponding to required suction head (hsv)

Next, the cavitation detecting device will be described. The cavitation detection device according to the first embodiment detects the degree of supercooling of the liquid refrigerant at the suction port of the liquid refrigerant transport device 1 at regular intervals during the cooling operation using cold storage heat, and satisfies Expression 2 described above. It is determined whether or not cavitation is likely to occur based on the result. This is shown in FIG.
This will be described with reference to the flowchart of FIG.

After the cooling operation is started, it is determined by a timer device mounted in the control device 7 whether or not a predetermined time set in advance has elapsed (step S).
1). If the predetermined time has elapsed, the liquid refrigerant transport device 1
The pressure and temperature of the liquid refrigerant at the inlet of the liquid refrigerant are detected (step S2), and the degree of supercooling Tca of the liquid refrigerant at the inlet of the liquid refrigerant transport device 1 is calculated by the controller 7 (step S3). Then, it is determined whether or not the degree of supercooling Tca is greater than the degree of supercooling Tcn corresponding to the required suction head (hsv) (step S4). The supercooling degree Tcn corresponding to the required suction head (hsv) is:
It is stored in a storage device in the control device in advance. And
If Tca is smaller than Tcn, it is determined that cavitation may occur, and the cavitation prevention device is activated (step S5). On the other hand, if Tca is greater than Tcn, it is determined that there is no possibility of cavitation, and the operation of the cavitation prevention device is stopped (step S6). Then, the timer device is reset (step S7).

Next, the operation of the cavitation prevention device will be described with reference to FIG. As described above, the cavitation prevention device includes the driving device 8, the refrigerant tank 4,
It is constituted by a communication pipe 5 and an on-off valve 6. And
When an operation command of the cavitation preventing device is transmitted from the cavitation detecting device to the driving device 8, an opening command is transmitted from the driving device 8 to the on-off valve 6, and the on-off valve 6 is opened.
open. Thereby, the liquid refrigerant is supplied from the refrigerant tank 4 to the suction port of the liquid refrigerant transport device 1 via the communication pipe 5, and the amount of the refrigerant in the refrigerant circuit Rc is increased. By taking this measure, the liquid refrigerant is directly supplied to the suction port of the liquid refrigerant transfer device 1, so that the state of the liquid refrigerant at the suction port of the liquid refrigerant transfer device 1 is immediately changed to a state in which there is no possibility of cavitation. Can be migrated. Also, if you keep this state,
The refrigerant amount in the entire refrigerant circuit Rc increases, and the cooling operation starts at the cycle indicated by the dotted line in FIG.
The cycle of a solid line in FIG. 3 circulating with a, point Ca, and point Da is shown. That is, the refrigeration cycle moves to the left on the ph diagram. As a result, the state of the refrigerant at the suction port of the liquid refrigerant transport device 1 becomes a state in which the degree of supercooling is large, and the state in which the possibility of cavitation is small is brought about.

When the state of the liquid refrigerant at the suction port of the liquid refrigerant transport device 1 returns to a state in which there is no possibility of cavitation, the cavitation detection device sends an operation stop command of the cavitation prevention device to the drive device 8. Then, a closing command is transmitted from the driving device 8 to the on-off valve 6 to close the on-off valve 6 and return to the cooling operation state.

In the above, when the on-off valve 6 is opened,
In order for the refrigerant to be supplied from the refrigerant tank 4 to the refrigerant circuit Rc via the communication pipe 5, the total head of the refrigerant tank 4 (the total head of the refrigerant at the point where the communication pipe 5 is connected to the refrigerant tank 4)
Must be larger than the total head of the refrigerant at the suction port of the liquid refrigerant transport device 1. In this case, when the pressure loss of the communication pipe 5 can be ignored, the static pressure of the refrigerant and the amount corresponding to the height can be set as the total head. From such a viewpoint, in the first embodiment, the position of the refrigerant tank 4 is
It is effective to make the total head higher on the refrigerant tank 4 side than at a position connected to the refrigerant circuit Rc.

Since the first embodiment is configured as described above, there is no fear that cavitation will occur inside the liquid refrigerant transport means 1 when the liquid refrigerant transport means 1 is operated to perform a cooling operation. There is no possibility that the liquid refrigerant transport unit 1 will break down.

The first embodiment can be modified as follows. (1) In the above description, the degree of supercooling of the refrigerant at the suction port of the liquid refrigerant transport device 1 is detected, but the degree of subcooling of the refrigerant at the discharge port of the liquid refrigerant transport device 1 is simultaneously detected. The degree of supercooling of the discharge port may be used as an auxiliary in determining whether the state of the refrigerant at the suction port of the liquid refrigerant transport device 1 may cause cavitation inside the liquid refrigerant transport device 1. It may be.

This will be further described. In the refrigerant liquefaction apparatus 3 in the first embodiment, it is normal that the water is stored in a frozen form in a frozen state. In such a case, the degree of supercooling of the refrigerant at the suction port of the liquid refrigerant transport apparatus 1 is described. Tca is as low as about 3 to 5 ° C., and the vicinity of the degree of supercooling is in a region where the refrigerant state is most difficult to be stabilized. For this reason, the supercooling degree T of the refrigerant at the suction port of the liquid refrigerant transport device 1
Judgment based on ca will require delicate judgment,
Misjudgments can also occur. In contrast, the liquid refrigerant transport device 1
As can be seen from the Ph diagram of FIG. 3, the degree of supercooling of the refrigerant at the discharge port is substantially smaller than the degree of supercooling Tca of the refrigerant at the inlet of the liquid refrigerant transport device 1. There is a certain relationship. For example, the degree of supercooling of the suction port is about 5 ° C. or more while being about 3 ° C. to 5 ° C., which is in a region where the stability of the refrigerant state is high.

Therefore, the degree of supercooling of the refrigerant in the vicinity of the discharge port of the liquid refrigerant transfer device 1 is detected, and based on the degree of subcooling of the refrigerant in the vicinity of the discharge port, the degree of supercooling in the vicinity of the suction port of the liquid refrigerant transfer device 1 is determined. By the same determination as that for the degree of supercooling Tca of the refrigerant, it is possible to roughly determine whether or not cavitation may occur. In making this determination, first, when the state of the refrigerant near the suction port of the liquid refrigerant transport device 1 does not cause cavitation, the degree of supercooling of the discharge port of the liquid refrigerant transport device 1 and the suction port are determined. , Which is ΔT here, and this ΔT is grasped in consideration of the pressure change between the suction side and the discharge side of the liquid refrigerant transport device 1. As a cavitation detecting device, a temperature sensor and a pressure sensor for detecting the temperature and the pressure of the refrigerant flowing through the portion near the discharge port of the liquid refrigerant conveying device 1 are provided. The supercooling degree of the refrigerant at the outlet of the refrigerant transport device 1 is calculated. The reference value for determining whether or not the degree of supercooling near the discharge port is equal to or more than a predetermined value is based on the above-mentioned ΔT value corresponding to the above-mentioned required suction head (hsv).
Is added.

As described above, if the degree of supercooling of the refrigerant in the vicinity of the suction port and the discharge port of the liquid refrigerant transfer device 1 is equal to or more than the predetermined value, the state of the refrigerant at the suction port of the liquid refrigerant transfer device 1 becomes liquid refrigerant. It may be determined that there is no possibility of generating cavitation inside the transport device 1.

(2) In the first embodiment,
The communication pipe 5 may be connected near the discharge port of the liquid refrigerant transport device 1. However, compared to the case where the communication pipe 5 is connected near the suction port of the liquid refrigerant transport device 1, the liquid refrigerant transport means 1
Since it takes a long time for the liquid refrigerant to circulate on the suction side, the result is inferior to that described above in terms of the responsiveness of the cavitation prevention effect.

Embodiment 2 Next, a second embodiment will be described with reference to FIG. FIG. 6 is a schematic configuration explanatory view of a refrigeration apparatus according to Embodiment 2. In FIG. 6, the same elements as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the second embodiment, similar to the conventional refrigerating apparatus, a cooling operation for performing cooling by a normal refrigerating cycle,
Cool storage operation for accumulating cold heat in a heat storage tank, cool storage use operation (cooling use cooling operation) for performing cooling (cooling) with the accumulated cold heat, cooling in which a cycle during the cooling operation and a cycle for the cool storage use operation are formed simultaneously. A refrigerating apparatus including a refrigerant circuit capable of performing each operation mode of the cold storage combined operation. Further, a high-pressure liquid refrigerant such as a receiver in the refrigerant circuit stores a refrigerant tank constituting the cavitation prevention measure in the first embodiment. The other points are the same as those of the first embodiment.

Referring to FIG. 6, a refrigerating apparatus according to the second embodiment includes a compressor 21, a condenser 22, a liquid receiver 23, an expansion valve 2,
4a, expansion valve 24b, refrigerant vaporizer (use-side heat exchanger)
2, the on-off valve 25 and the on-off valve 26 are sequentially connected to form a main refrigerant circuit. Then, by operating the compressor 21 to flow the refrigerant through the main refrigerant circuit, a cooling operation by a normal refrigeration cycle is performed.

In this refrigeration system, an on-off valve 29, a refrigerant liquefaction device 3, and a liquid refrigerant transfer device 1 are connected to the main refrigerant circuit in parallel with a series circuit of an expansion valve 24a, a refrigerant vaporizer 2, and an on-off valve 25. , A series circuit of the on-off valve 27 is connected. In this series circuit, an on-off valve 28 is connected in parallel with the liquid refrigerant transport device 1. In the refrigerant liquefaction apparatus 3 described above, the heat storage material 3b is accommodated in the heat storage tank 3a, and the refrigerant cooling heat exchanger 3c is further accommodated to exchange heat with the heat storage material 3b. Further, in this refrigeration apparatus, the refrigerant tank forming a part of the cavitation prevention device in the first embodiment is used as the liquid receiver 23, and the communication pipe 5 for supplying the liquid refrigerant to the suction port of the liquid refrigerant transport device 1. Has one end Xa connected to the vicinity of the suction port of the liquid refrigerant transport device 1 and the other end Xb connected to the liquid part of the liquid receiver 23.

In the cold storage operation, the on / off valves 6, 25 and the expansion valve 24b are closed, the on / off valves 27, 28, 29, 26 are opened, the expansion valve 24a is set in the refrigerant control state, and the liquid refrigerant transport device 1 is stopped. , By operating the compressor 21. The refrigerant discharged from the compressor 21 is condensed and liquefied in the condenser 22 and stored in the liquid receiver 23. This liquid refrigerant is
The pressure is reduced by the expansion valve 24a, and in this mode, the refrigerant liquefier 3 acting as an evaporator evaporates and evaporates to cool and freeze the heat storage material 3b (in this case, water), and returns to the compressor 21 as a low-pressure gas refrigerant. Thus, cold heat is accumulated in the cold storage tank 3a.

In the cold storage operation, the on-off valves 6, 26 and 28 and the expansion valve 24a are closed, and the on-off valves 25, 29 and 27 are opened.
The operation is performed by fully opening the expansion valve 24b, stopping the compressor 21, and driving the liquid refrigerant transport device 1. The liquid refrigerant discharged from the liquid refrigerant transport device 1 is slightly depressurized by the refrigerant flow resistance in the on-off valve 27, the expansion valve 24b, the piping, and the like, and is sent to the refrigerant vaporizer 2. The refrigerant sent to the refrigerant vaporizer 2 is vaporized by the refrigerant vaporizer 2 to become a gas refrigerant,
The refrigerant is sent to the refrigerant liquefaction apparatus 3 through 29. Here, the refrigerant is cooled and liquefied by the heat storage material 3b of the refrigerant liquefaction device 3, and returns to the liquid refrigerant transport device 1. In this manner, cooling using the cold storage heat stored in the cold storage tank 3a is performed.
The refrigerant circuit at this time is the refrigerant circuit Rc during the cold storage operation.

The combined operation of cooling and cold storage is performed by the on-off valve 25,
26, 29 and 27 are opened, on-off valves 6 and 28 are closed, and expansion valve 2 is opened.
By setting the refrigerant flow control states of 4a and 24b respectively and driving the compressor 21 and the refrigerant liquid pump 1, the flow of the refrigerant by the refrigerant circuit Rc at the time of the cold storage operation and the flow of the refrigerant at the time of the normal cooling operation are changed. Simultaneously, the regenerator 3
A combined cooling / cooling operation is performed in which the cold storage heat stored in a is used in an auxiliary manner.

In the cold storage use operation and the combined cooling / cooling operation, as in the first embodiment, the cavitation detecting device determines that the refrigerant at the suction port of the liquid refrigerant transport device 1 may generate cavitation. In this case, the on-off valve 6 constituting the cavitation prevention device is opened, and the liquid refrigerant in the liquid receiver 23 is supplied into the refrigerant circuit Rc via the communication pipe 5.

In the above-described cold storage operation, when the cold storage operation is performed from a state in which the refrigerating apparatus is stopped for a long time, or after the cold storage operation is continued, the pressure in the liquid receiver 23 is reduced to a predetermined value. Although the pressure may be lower than the pressure, in order to prevent this, both ends Xa,
When the pressure at the point Xb is detected and the pressure difference falls below a predetermined value, the expansion valve 24a is opened and the compressor 21 is operated (this operation is equivalent to the pump-down operation). Can always be maintained at or above a predetermined pressure.

The high-pressure liquid refrigerant in place of the refrigerant tank in the first embodiment stores the high-pressure liquid refrigerant.
It is not limited to only. For example, the condenser 22 may be used. Further, when the liquid receiver 23 is replaced with a refrigerant tank, the connection position of the one end Xb of the communication pipe 5 does not need to be limited to the liquid part of the liquid receiver 23. For example, the liquid receiver 23 and the expansion valve 24a It is also possible to use a pipe that connects In the case where the condenser 22 is replaced with a refrigerant tank, the connection position of the one end Xb of the communication pipe 5 is determined by the outlet of the condenser 22 or the pipe connecting the condenser 22 and the liquid receiver 23. do it. In addition, connecting pipe 5
The connection position of the other end Xa is not limited to the vicinity of the suction port of the liquid refrigerant transport device 1 described above, but may be, for example, between the on-off valve 29 and the refrigerant liquefaction device 3.

Embodiment 3 Next, a third embodiment will be described with reference to FIG. FIG. 7 is a schematic configuration explanatory view of a refrigeration apparatus according to Embodiment 3. In FIG. 7, the same elements as those in the second embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In the third embodiment, the refrigerant circuit in the second embodiment is configured such that the liquid receiver 23 is eliminated and the accumulator 31 is provided on the suction side of the compressor 21. The portion corresponding to the tank is not the portion storing the high-pressure liquid refrigerant as in the liquid receiver in the second embodiment, but an accumulator 31. Other configurations are the same as those of the second embodiment.

In the third embodiment, the connecting pipe 5
Is connected to the accumulator 31 which is on the low pressure side in the refrigeration cycle. In order to send the liquid refrigerant from the accumulator 31 to the suction port of the liquid refrigerant transport device 1 of the refrigerant circuit Rc, the accumulator 31 is arranged at a high place. The total head of the refrigerant at the end Xb of the connecting pipe is set higher by the position head H than at the other end Xa of the connecting pipe.

Embodiment 4 Next, a fourth embodiment will be described with reference to FIGS. FIG. 8 is an explanatory diagram of a main part configuration of a refrigeration apparatus according to Embodiment 4, and FIG. 9 is a Ph diagram for explaining an operation of the cavitation prevention device in the refrigeration apparatus. In FIG. 8, the same portions as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The cavitation preventing device according to the first embodiment supplies liquid refrigerant to the suction port of the liquid refrigerant transport device 1 when the cavitation detecting device determines that cavitation may occur. The cavitation prevention device according to the fourth embodiment is configured to increase the heat exchange capacity of the refrigerant liquefaction device 3.

That is, in the first embodiment, the communication pipe 5 provided with the refrigerant tank 4 and the on-off valve 6 is used as the cavitation preventing device. As shown in FIG. 8, a spray pipe 3e for blowing air bubbles is provided below the heat storage tank 3a of the refrigerant liquefaction apparatus 3, and this is connected to an air pump 3f. When the cavitation detecting device determines that cavitation may occur, the air pump 3f is driven to generate air bubbles from the lower spray pipe 3e in the liquid heat storage material 3b such as water in the heat storage tank 3a. By doing so, a flow or a vortex is generated in the liquid on the surface of the refrigerant cooling heat exchanger 3c to improve the heat transfer performance, and the amount of heat exchange of the refrigerant liquefaction apparatus 3 is increased.

As described above, when the heat exchange amount of the refrigerant liquefaction apparatus 3 is increased, the liquefaction action increases as shown in the Ph diagram of FIG. 9, and the refrigeration cycle moves to the lower left, and the refrigerant liquefaction apparatus 3 The degree of supercooling of the refrigerant at the third outlet increases. Therefore, by configuring the cavitation preventing device as described above and operating the device, the degree of subcooling of the liquid refrigerant at the suction port of the liquid refrigerant conveying device 1 can be increased. Further, since the liquid refrigerant having a large degree of supercooling directly flows into the suction port of the liquid refrigerant transfer device 1, the state of the refrigerant at the suction port of the liquid refrigerant transfer device 1 is not quickly changed, and there is no possibility of cavitation. Can be changed to state.

In the fourth embodiment, the heat exchange capacity of the refrigerant liquefaction apparatus 3 is increased by generating air bubbles from the spray pipe 3e even during steady operation, and the cavitation prevention apparatus is operated. As a mode of this, the amount of heat exchange of the refrigerant liquefaction apparatus 3 may be further increased by further increasing the bubble amount. Further, a liquid pump may be used instead of the air pump 3f to blow out pressurized liquid instead of blowing out bubbles, so that the heat exchange amount of the refrigerant liquefaction apparatus 3 may be increased. As a method of increasing the heat exchange amount of the refrigerant liquefaction apparatus 3, instead of generating bubbles or the like, the number of refrigerant cooling heat exchangers 3 c used in the refrigerant liquefaction apparatus 3 may be increased. Thus, the heat exchange area may be increased.

Embodiment 5 Next, a fifth embodiment will be described with reference to FIGS. FIG. 10 is an explanatory diagram of a main part configuration of a refrigeration apparatus according to Embodiment 5, and FIG.
FIG. 1 is a Ph diagram for explaining the operation of the cavitation preventing device in the refrigeration system. Note that FIG.
In the description of the first embodiment, the same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

The cavitation preventing device according to the first embodiment is configured to supply the liquid refrigerant to the suction port of the liquid refrigerant conveying device 1 when the cavitation detecting device determines that cavitation may occur. The cavitation preventing device according to the fifth embodiment is configured to reduce the heat exchange capacity of the refrigerant vaporizer 2.

That is, in the first embodiment, the communication pipe 5 provided with the refrigerant tank 4 and the opening / closing valve 6 is used as the cavitation preventing device. As shown in FIG. 10, a bypass circuit 36 having an opening control valve 35 interposed in parallel with the refrigerant vaporizer 2 is provided. The opening control valve 35 is closed during a normal cooling operation. Then, when it is determined by the cavitation detecting device that cavitation may occur, by opening the opening control valve 35 and adjusting the opening, the amount of refrigerant circulating to the refrigerant vaporizer 2 is reduced. , To reduce the amount of heat exchange.

As described above, when the amount of heat exchange of the refrigerant vaporizer 2 is reduced, as shown in a Ph diagram of FIG. 11, the vaporizing action is reduced, and the refrigeration cycle is further moved to the upper left.
The degree of supercooling of the refrigerant at the outlet of the refrigerant liquefaction device 3 increases. Therefore, by configuring the cavitation preventing device as described above and operating the device, the degree of subcooling of the liquid refrigerant at the suction port of the liquid refrigerant conveying device 1 can be increased. Further, the liquid refrigerant having a large degree of supercooling flows into the suction port of the liquid refrigerant transfer device 1 as it is, so that the state of the refrigerant at the suction port of the liquid refrigerant transfer device 1 can be quickly reduced without the possibility of cavitation. Can be changed to state.

In the fifth embodiment, when the amount of heat exchange of the refrigerant liquefaction apparatus 3 is increased at the same time, the degree of supercooling of the liquid refrigerant at the outlet of the refrigerant liquefaction apparatus 3 is further increased, and the suction port of the liquid refrigerant transport apparatus is increased. Can be more quickly and reliably changed to a state in which cavitation is not likely to occur.

Embodiment 6 FIG. Next, a sixth embodiment will be described with reference to FIGS. FIG. 12 is a Ph diagram for explaining the operation of the cavitation prevention device in the refrigeration apparatus according to Embodiment 6, and FIG.
FIG. 4 is an explanatory diagram of a main part configuration showing a modification of the refrigeration apparatus.

In the first embodiment, the cavitation preventing device is provided when the cavitation detecting device determines that cavitation may occur.
Although the liquid refrigerant is supplied to the suction port of the liquid refrigerant transport device 1, in the sixth embodiment, the liquid refrigerant transport amount of the liquid refrigerant transport device 1 is reduced. In addition, as a method of reducing the liquid refrigerant transport amount of the liquid refrigerant transport device 1, the rotation speed of the transport unit of the liquid refrigerant transport device 1 is reduced.

As described above, when the liquid refrigerant transfer amount of the liquid refrigerant transfer device 1 is reduced, as shown in a Ph diagram of FIG. Increases, the refrigeration cycle spreads left and right, and the degree of supercooling of the refrigerant at the outlet of the refrigerant liquefaction apparatus 3 increases. Therefore, by configuring the cavitation preventing device as described above and operating the device, the degree of subcooling of the liquid refrigerant at the suction port of the liquid refrigerant conveying device 1 can be increased. Further, since the liquid refrigerant having a large degree of supercooling directly flows into the suction port of the liquid refrigerant transfer device 1, the state of the refrigerant at the suction port of the liquid refrigerant transfer device 1 is not quickly changed, and there is no possibility of cavitation. Can be changed to state. When the state of the refrigerant at the suction port of the liquid refrigerant transport device 1 returns to a state in which cavitation is not likely to occur, the rotation speed of the transport unit of the liquid refrigerant transport device 1 is gradually increased to increase the refrigerant transport amount.

As a method of reducing the liquid refrigerant transport amount of the liquid refrigerant transport device 1, as described above,
Instead of reducing the rotation speed of the transfer unit, as shown in FIG. 13, a pressure reducing device 38 is provided between the liquid refrigerant transfer device 1 and the refrigerant vaporizer 2, and the pressure reducing device 38 is throttled as necessary. By increasing the difference between the suction pressure and the discharge pressure of the liquid refrigerant transport device 1, the amount of refrigerant transported by the liquid refrigerant transport device 1 can also be reduced.

Embodiment 7 Next, a seventh embodiment will be described with reference to FIGS. FIG. 14 is an explanatory diagram of a main part configuration of a refrigeration apparatus according to Embodiment 7, and FIG.
5 is a control flowchart of the cavitation detecting device in the refrigeration apparatus shown in FIG. In these drawings, the same elements as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The seventh embodiment differs from the first embodiment in that the cavitation detecting device has a different configuration, and the other configurations are the same. In the following description, it is assumed that the configuration other than the cavitation detection device is the same as that of the first embodiment, and the description will focus on the cavitation detection device of the present embodiment.

In FIG. 14, reference numeral 41 denotes the liquid refrigerant transport device 1
And a cavitation detecting device together with the control device 7. The cavitation detection device according to the present embodiment detects the input current of the liquid refrigerant transport device 1 by the input current sensor 41 every predetermined time,
The determination is made based on whether or not the input current value is within a set range.

This will be specifically described with reference to FIG. After the cooling operation is started, it is determined by a timer device mounted in the control device 7 whether a predetermined period of time has elapsed (step S11). If the predetermined time has elapsed, the input current of the liquid refrigerant transport device 1 is measured by the input current sensor 41 (step S1).
2) It is determined whether this current value is within a preset range (step S13). As a result, if the actual input current value of the liquid refrigerant transport device 1 is not within the preset range, it is determined that cavitation may occur, and the cavitation prevention device is activated (step S1).
4). On the other hand, if it is determined that the actual input current value of the liquid refrigerant transport device 1 is within the preset range, it is determined that there is no possibility of cavitation, and the operation of the cavitation prevention device is stopped (step S15). ). Then, the timer device is reset (step S1).
6).

Next, a method of determining a “predetermined range” for the input current of the liquid refrigerant transport device 1 will be described. The transfer work load of the liquid refrigerant transfer device 1 is represented by the product of the weight flow rate of the transfer refrigerant per unit time and the amount of energy change per unit time. In addition, the liquid refrigerant transport device 1
The liquid refrigerant density at the suction port of the liquid crystal hardly changes even if the temperature of the refrigerant largely changes. Therefore, the liquid refrigerant transport device 1
When only the liquid refrigerant is reliably supplied to the suction port of the liquid refrigerant transfer device, the transfer work load of the liquid refrigerant transfer device 1 hardly changes, and the input current of the liquid refrigerant transfer device 1 hardly changes. Therefore, the input current value in a stable state where there is no possibility of cavitation is measured in advance, and the liquid in this stable state is taken into account in consideration of changes in operating conditions, some variation between machines, and measurement errors. The width of the input current value of the refrigerant transport device 1 is determined, and is set as a set range.

On the other hand, when the state of the liquid refrigerant at the suction port of the liquid refrigerant transfer device 1 becomes a state in which cavitation occurs, and cavitation occurs in the liquid refrigerant transfer device 1, the mechanical portion in the liquid refrigerant transfer device 1 The load applied to the bearing due to an impact or the like increases, and as a result, the input current value increases. Further, when this state is continued and the ratio of the gas refrigerant flowing into the suction port of the liquid refrigerant transport device 1 further increases,
The liquid refrigerant transport device 1 sucks only the gas refrigerant and stops transporting the liquid refrigerant, and eventually falls into a state in which almost no refrigerant is transported, and the load for transporting the refrigerant is reduced. In this case, the input current value is reduced. .

Therefore, as a method for determining whether the state of the liquid refrigerant at the suction port of the liquid refrigerant transport device 1 may cause cavitation, the input of the liquid refrigerant transport device 1 is performed at predetermined time intervals as described above. A method of detecting the current value and comparing the current value with the above-mentioned set range can be adopted. When the input current value of the liquid refrigerant transport device 1 is within the set range, there is no possibility of cavitation, and when the input current value is out of the set range, there is a possibility of cavitation. It can be determined that there is.

Embodiment 8 FIG. Next, an eighth embodiment will be described. In the eighth embodiment, as an element for determining whether or not cavitation occurs, noise or vibration of the liquid refrigerant transport device 1 is employed instead of the input current of the liquid refrigerant transport device 1 in the seventh embodiment. . Therefore, in this configuration, the input current sensor 41 in the seventh embodiment is replaced with a noise sensor or a vibration sensor. That is, in the seventh embodiment, it is determined whether or not the input current value of the liquid refrigerant transport device 1 is within the set range. In the eighth embodiment, this is determined by the noise or vibration value of the liquid refrigerant transport device 1. Is replaced by whether or not it is within the set range (the description based on the drawings is omitted).

The reason why such replacement is possible will now be described. When the refrigerant state at the suction port of the liquid refrigerant transport device 1 is stable in the liquid phase alone, the noise or vibration value of the liquid refrigerant transport device 1 does not change significantly even if the operating conditions change. Therefore, the noise or vibration value of the liquid refrigerant transfer device 1 in a state where the refrigerant state of the suction port of the liquid refrigerant transfer device 1 is stable in the liquid phase alone is measured, and changes in the operating conditions and some The width of the noise or vibration value of the liquid refrigerant transport device 1 in a stable state is determined in consideration of the variation in the measurement, the measurement error, and the like, and this is set as a set range.

On the other hand, the state of the liquid refrigerant at the suction port of the liquid refrigerant transport device 1 becomes a state in which cavitation occurs. When cavitation occurs in the liquid refrigerant transport device 1, noise or noise is generated due to an impact applied to the mechanical part. Vibration increases. Further, when this state is continued and the ratio of the gas refrigerant flowing into the suction port of the liquid refrigerant transport device 1 further increases, the liquid refrigerant transport device 1 stops sucking only the gas refrigerant and no longer transporting the liquid refrigerant, and almost no longer. Since the refrigerant is not being conveyed and the refrigerant conveyance load is reduced, the noise or vibration value becomes extremely small in that case.

Therefore, as a method for judging whether or not the state of the liquid refrigerant at the suction port of the liquid refrigerant conveying device 1 is likely to cause cavitation, a method similar to that of the above-described seventh embodiment is used at predetermined time intervals. A method of detecting the noise or vibration value of the liquid refrigerant transfer device 1 as an element replacing the input current value of the liquid refrigerant transfer device 1 and comparing the noise or vibration value with the above-described set range can be adopted. Further, when the noise or vibration value of the liquid refrigerant transport device 1 is within the set range, there is no possibility of cavitation, and when the noise or vibration value is out of the set range,
It can be determined that there is a possibility that cavitation may occur.

Embodiment 9 Next, a ninth embodiment will be described with reference to FIGS. The ninth embodiment differs from the first embodiment in that the cavitation detecting device has a further different configuration (a configuration different from those of the seventh and eighth embodiments), and other configurations are the same. In the following description, it is assumed that the configuration other than the cavitation detection device is the same as that of the first embodiment, and the description will focus on the cavitation detection device of the present embodiment. In these drawings, the same elements as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 16 is an explanatory view of the configuration of a refrigeration apparatus according to the ninth embodiment. In this figure, reference numeral 43 denotes a temperature sensor for detecting the temperature of the medium to be cooled flowing into the refrigerant vaporizer 2;
Reference numeral 4 denotes a temperature sensor for detecting the temperature of the medium to be cooled flowing out of the refrigerant vaporizer 2, and reference numeral 45 denotes a rotation speed sensor for detecting the rotation speed of the transport unit of the liquid refrigerant transport device 1. In the following description, the temperature of the medium to be cooled detected by the temperature sensor 43 is Tai, and the temperature of the medium to be cooled detected by the temperature sensor 44 is Tao.

Then, in a state where the state of the refrigerant at the suction port of the liquid refrigerant transfer device 1 does not cause cavitation, the heat exchange in the refrigerant vaporization device 2 obtained from the cooled object side in the case of the temperature difference Tai-Tao. The amount of heat (hereinafter referred to as a refrigerant vaporization heat exchange amount Qa estimated from the temperature difference Tai-Tao) is calculated in advance. FIG. 17 shows the relationship between the temperature difference Tai-Tao and the heat exchange heat quantity in this case.

Further, in a state where the state of the refrigerant at the suction port of the liquid refrigerant transport device 1 does not cause cavitation, the refrigerant transport amount of the liquid refrigerant transport device 1 detected by the rotation speed sensor 45 is calculated. A heat exchange heat amount (hereinafter, referred to as a refrigerant vaporization heat exchange amount Qe estimated from the refrigerant transfer amount of the liquid refrigerant transfer device 1) calculated from an enthalpy change when the refrigerant transfer amount is vaporized by the refrigerant vaporizer 2 is calculated. Further, an actual temperature difference Tai-Tao is calculated from the temperatures Tai and Tao detected by the temperature sensors 43 and 44, and a refrigerant vaporization heat exchange amount estimated from the temperature difference Tai-Tao is calculated from the relationship in FIG. Then, the calculated refrigerant vaporization heat exchange amount Qa is compared with the above-described heat exchange amount Qe.

In this case, if the state of the refrigerant at the suction port of the liquid refrigerant transport device 1 is such that cavitation does not occur, there should be no significant difference between the two. On the other hand, when cavitation occurs, the amount of liquid refrigerant transported by the liquid refrigerant transport device 1 is greatly reduced, and the object to be cooled is hardly cooled, and the temperature difference Tai-Tao decreases. , Temperature difference Tai-T
The refrigerant vaporization heat exchange amount Qa estimated from ao decreases.

Therefore, the refrigerant vaporization heat exchange amount Qa estimated from the temperature difference Tai-Tao and the refrigerant vaporization heat exchange amount Qe estimated from the refrigerant conveyance amount of the liquid refrigerant conveyance device 1 are compared. , If the difference falls within the predetermined range,
The state of the liquid refrigerant at the inlet of the liquid refrigerant transport device 1 can be determined to be free of cavitation. If the difference does not fall within a predetermined range, the state of the liquid refrigerant at the inlet of the liquid refrigerant transport device 1 can be determined. Can be determined to have caused cavitation.

The cavitation detecting device according to the ninth embodiment is operated as described above, and is used for detecting the temperature Tai of the cooling medium flowing into the refrigerant vaporizer 2 and the temperature Tao of the cooling medium flowing out of the refrigerant vaporizer 2. Instead, the temperature Twi of the cooling medium flowing into the refrigerant liquefaction apparatus 3 and the temperature Two of the cooling medium flowing out of the refrigerant liquefaction apparatus 3 are detected, and the refrigerant liquefaction heat exchange amount and the liquid refrigerant estimated from the temperature difference Twi-Two are detected. Cavitation can also be detected by calculating the refrigerant liquefaction heat exchange amount estimated from the refrigerant conveyance amount of the conveyance device 1 and comparing the two refrigerant liquefaction heat exchange amounts in the same manner as described above.

As described above, according to the ninth embodiment, as a method for determining whether or not the state of the liquid refrigerant at the suction port of the liquid refrigerant transfer device may cause a failure of the liquid refrigerant transfer device, Every hour, the refrigerant vaporization or liquefaction heat exchange amount is compared with the refrigerant vaporization or liquefaction heat exchange amount estimated from the refrigerant conveyance amount of the liquid refrigerant conveyance device 1, and the difference is within a predetermined range. For example, it can be determined that there is no possibility of causing a failure of the liquid refrigerant transport device, and if it is outside the predetermined range, it can be determined that there is a possibility of causing a failure of the liquid refrigerant transport device.

In the above-described seventh to ninth embodiments, the cavitation detecting device described in each of the embodiments is described as an alternative to the cavitation detecting device in the first embodiment, but is not limited thereto. It is clear from the description of each of the embodiments that the cavitation detection device described in each of Embodiments 2 to 6 may be used instead of the cavitation detection device described above.

[0096]

As described above, according to the first to ninth aspects of the present invention, the state of the liquid refrigerant at the suction port of the liquid refrigerant transfer device may cause cavitation inside the liquid refrigerant transfer device. A cavitation detection device that determines whether there is a cavitation detection device, and a state in which cavitation does not occur when the cavitation detection device determines that cavitation may occur. Cavitation prevention device that changes to the state of the liquid refrigerant conveyance device, even if the cavitation may occur inside the liquid refrigerant conveyance device due to changes in operating conditions, etc. Can be returned to a state in which cavitation is not likely to occur inside the liquid refrigerant transport device.

Further, according to the second aspect of the present invention, the cavitation detecting device needs the supercooling degree detected for the refrigerant near the suction port of the liquid refrigerant conveying device.
If the degree of subcooling is smaller than the degree of supercooling corresponding to PSH, it is determined that cavitation may occur. Therefore, preventive measures can be taken before cavitation actually occurs in the liquid refrigerant transport device.

[0098] According to the third aspect of the present invention, the cavitation detecting device may generate cavitation when the detected input current value of the liquid refrigerant transport device falls outside a predetermined range. Since it is determined that cavitation has occurred, it is certain that cavitation has occurred, and in that case, the liquid refrigerant state at the suction port of the liquid refrigerant transport device must be returned to a state in which cavitation is not likely to occur. Can be.

Further, according to the fourth aspect of the present invention, the cavitation detecting device, when the detected noise or vibration value of the liquid refrigerant transport device is out of the predetermined range,
Since it is determined that cavitation may occur, the detection of cavitation is reliable, and in that case, the state of the liquid refrigerant at the inlet of the liquid refrigerant transport device may be changed to cause cavitation. It can be returned to a state without sex.

Further, according to the sixth aspect of the present invention, the cavitation prevention device is provided between the liquid refrigerant transfer device and the refrigerant liquefaction device from a refrigerant tank disposed outside the refrigerant circuit. The liquid refrigerant is supplied to the liquid refrigerant conveying device, so that when it is determined that cavitation may occur, the liquid refrigerant is immediately supplied to the suction port of the liquid refrigerant conveying device, thereby promptly avoiding the occurrence of cavitation. Can be.

According to the seventh aspect of the present invention, since the cavitation preventing device increases the heat exchange amount of the refrigerant liquefaction device, it is determined that cavitation may occur. In this case, the degree of supercooling of the refrigerant supplied from the refrigerant liquefier to the suction port of the liquid refrigerant transport device is immediately increased, and the occurrence of cavitation can be quickly avoided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration explanatory diagram of a refrigeration apparatus according to Embodiment 1 of the present invention.

FIG. 2 is an explanatory view of a specific configuration of the refrigerant liquefaction apparatus according to FIG.

FIG. 3 is an explanatory diagram of a refrigeration cycle of the refrigeration apparatus according to FIG.

FIG. 4 is a diagram illustrating the principle of a device for detecting cavitation in the refrigeration apparatus according to FIG. 1;

FIG. 5 is a control flowchart of the cavitation detection device in the refrigeration apparatus according to FIG. 1;

FIG. 6 is a schematic configuration explanatory view of a refrigeration apparatus according to Embodiment 2 of the present invention.

FIG. 7 is a schematic configuration explanatory view of a refrigeration apparatus according to Embodiment 3 of the present invention.

FIG. 8 is an explanatory diagram of a main part configuration of a refrigeration apparatus according to Embodiment 4 of the present invention.

FIG. 9 is a Ph diagram for explaining the operation of the cavitation prevention device in the refrigeration device of FIG. 8;

FIG. 10 is an explanatory diagram of a main configuration of a refrigeration apparatus according to Embodiment 5 of the present invention.

11 is a Ph diagram for explaining the operation of the cavitation preventing device in the refrigeration device of FIG.

FIG. 12 is a Ph diagram for explaining the operation of the cavitation prevention device in the refrigeration apparatus according to Embodiment 6 of the present invention.

FIG. 13 is an explanatory diagram of a main part configuration showing a modification of the refrigeration apparatus according to Embodiment 6 of the present invention.

FIG. 14 is a schematic configuration explanatory diagram of a refrigeration apparatus according to Embodiment 7 of the present invention.

FIG. 15 is a control flowchart of a cavitation detection device in the refrigeration apparatus according to FIG. 14;

FIG. 16 is a schematic configuration explanatory diagram of a refrigeration apparatus according to Embodiment 9 of the present invention.

17 is an explanatory diagram of an estimated heat exchange amount in the refrigeration apparatus of FIG.

FIG. 18 is a schematic diagram illustrating a configuration of a conventional refrigeration apparatus.

[Explanation of symbols]

Reference Signs List 1 liquid refrigerant transport device, 2 refrigerant vaporizer, 3 refrigerant liquefier, 3a heat storage tank, 3b heat storage material, 3c refrigerant cooling heat exchanger, 3d heat storage material cooling heat exchanger, 3e spray pipe, 3f air pump, Refrigerant tank, 5 communication piping, 6 on-off valve, 7 control device, 8 drive device, 11
Temperature sensor, 12 Pressure sensor, 21 Compressor, 22
Condensers, 24a, 24b expansion valves, 25, 26, 27,
28, 29 open / close valve, 31 accumulator, 35 opening control valve, 36 bypass pipe, 38 pressure reducing device, 41
Input current sensor, 31 Pressure sensor, 32 Temperature sensor, 41 Input current sensor, 43, 44 Temperature sensor,
45 A rotation speed sensor, a refrigerant circuit for circulating the Rc liquid refrigerant, a degree of supercooling of the refrigerant at the suction port of the Tca liquid refrigerant transfer device, and a pressure difference corresponding to Pab effective suction head.

Continuing from the front page (72) Inventor Yasufumi Hatamura 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Shin Saito 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Co., Ltd. In company

Claims (9)

[Claims] 1. A refrigeration system for circulating a refrigerant in a refrigerant circuit in which a liquid refrigerant transport device, a refrigerant vaporizer, and a refrigerant liquefier are sequentially connected to a refrigerant circuit, wherein a liquid refrigerant state at a suction port of the liquid refrigerant transport device is a liquid refrigerant. A cavitation detection device for determining whether or not cavitation may be generated inside the transfer device; and an inlet of the liquid refrigerant transfer device when the cavitation detection device determines that cavitation may be generated. A cavitation preventing device for changing the state of the liquid refrigerant to a state in which cavitation does not occur. 2. The method according to claim 1, wherein the cavitation detecting device is capable of generating cavitation when the degree of supercooling detected for the refrigerant near the suction port of the liquid refrigerant transfer device is smaller than the degree of supercooling corresponding to the required NPSH. The refrigeration apparatus according to claim 1, wherein the refrigeration apparatus is determined to be present. 3. The cavitation detection device is configured to determine that cavitation may occur when the detected input current value of the liquid refrigerant transport device is out of a predetermined range. The refrigeration apparatus according to claim 1, wherein 4. The cavitation detection device determines that cavitation may occur when the detected noise or vibration value of the liquid refrigerant transport device falls outside a predetermined range. The refrigeration apparatus according to claim 1, wherein 5. The cavitation detecting device according to claim 1, wherein a heat exchange amount estimated from a refrigerant transfer amount of the liquid refrigerant transfer device and a heat estimated from a medium temperature flowing into and out of the refrigerant vaporizer or the refrigerant liquefier. 2. The method according to claim 1, wherein when the difference from the exchange amount is out of a predetermined range, it is determined that cavitation may occur.
A refrigeration device as described. 6. The cavitation prevention device according to claim 1, wherein the cavitation prevention device supplies a liquid refrigerant between the liquid refrigerant transport device and the refrigerant liquefaction device from a refrigerant tank disposed outside a system of the refrigerant circuit. The refrigeration apparatus according to any one of claims 1 to 5, characterized in that: 7. The refrigeration apparatus according to claim 1, wherein the cavitation prevention device increases a heat exchange amount of the refrigerant liquefaction device. 8. The refrigeration apparatus according to claim 1, wherein the cavitation prevention device reduces a heat exchange amount of the refrigerant vaporizer. 9. The refrigeration apparatus according to claim 1, wherein the cavitation prevention device reduces a flow rate of the liquid refrigerant transport device.