JP3663046B2 - Refrigeration equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a refrigeration apparatus such as a condensing unit.
[0002]
[Prior art]
In general, a compressor, a condenser, and a receiver tank are provided, and a main circuit for sending refrigerant from the receiver tank to the evaporator, an oil cooling circuit for returning the refrigerant to the compressor through an oil cooler, and a supercooler for returning to the compressor A refrigeration apparatus such as a condensing unit provided with a supercooling circuit and an injection circuit for returning to the compressor as a cooling refrigerant is known.
[0003]
In this type, two outlets from the receiver tank are provided, the main circuit is connected to one place, and an oil cooling circuit, a supercooling circuit, and an injection circuit are connected to another place. Has been.
[0004]
On the other hand, in the case of an ultra-low temperature refrigeration apparatus using an air-cooled two-stage screw compressor, the evaporation temperature in the evaporator connected to the refrigeration apparatus is -50 ° C to -60 ° C, so the evaporation pressure becomes negative pressure, Air enters the refrigerant circuit from the pipe connection port, and this air circulates in the circuit. In order to release this air, conventionally, an air purge valve is generally provided in the refrigerant pipe of the condenser of the refrigeration apparatus.
[0005]
Further, in the refrigeration apparatus provided with the compressor, an analog pressure switch is provided to detect the pressure on the low pressure side of the compressor, and the operation of the compressor is stopped when the detected pressure of the analog pressure switch reaches a predetermined value. A refrigeration system has been proposed.
[0006]
[Problems to be solved by the invention]
However, in the conventional configuration, since two outlets from the receiver tank are provided, the possibility of refrigerant leakage from the connection port increases, and the receiver tank structure is complicated due to the complexity of the refrigerant piping and the like. There is a problem of becoming.
[0007]
Further, even if an air purge valve is provided in the refrigerant pipe of the condenser, there is a problem that the inside of the refrigerant pipe located above the connection pipe cannot be air purged because it is conventionally provided in the connection pipe of a plurality of headers in the condenser.
[0008]
Furthermore, in the case where the low pressure side pressure of the compressor is detected by an analog pressure switch, the low pressure side pressure becomes negative pressure due to the gauge pressure in the case of a two-stage screw compressor, so it cannot be detected directly. Conventionally, the intermediate pressure of the two-stage screw compressor is detected to stop the operation of the compressor. However, although there is a certain degree of correlation between the intermediate pressure and the low pressure, there is a problem that the low pressure of the compressor cannot be accurately detected.
[0009]
An object of the present invention is to provide a refrigeration apparatus that eliminates the problems of the prior art, simplifies the structure of the receiver tank, enables almost reliable air purging, and detects the low pressure of the compressor almost accurately. There is to do.
[0010]
[Means for Solving the Problems]
The invention according to claim 1 includes a main circuit that connects a compressor, an oil separator, a condenser, and a receiver tank with a refrigerant pipe, and supplies the liquid refrigerant derived from the receiver tank to the evaporator through a supercooler , The capacitors are arranged in a substantially V shape, and each of the capacitors arranged in a substantially V shape includes an inlet header and an outlet header, and each inlet disposed inside the inlet header and the outlet header. An air purge valve is provided at the top of the header .
[0015]
In these inventions, the air purge valve is positioned at the top of the refrigerant pipe, so that the air is almost completely purged. In addition, since the air purge valve is provided in each of the plurality of headers, air purge can be performed for each header individually.
[0016]
The invention according to claim 2 is the one according to claim 1, wherein the compressor is a two-stage screw compressor in which the suction pressure is a negative pressure and a gauge pressure , and the low-pressure side of the two-stage screw compressor is A digital pressure switch for detecting pressure is configured to be able to detect negative pressure, and the operation of the two-stage screw compressor is stopped when the detected pressure of the digital pressure switch reaches a predetermined value.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0018]
In FIG. 1, reference numeral 1 denotes an air-cooled two-stage screw compressor, and the compressor 1 includes a high pressure portion 1a, an intermediate pressure portion 1b, and a low pressure portion 1c. The refrigerant sucked into the low pressure part 1c through the suction pipe 2 is compressed by the compressor 1 and discharged from the high pressure part 1a. The discharged refrigerant flows into the oil separator 4 through the discharge pipe 3, and after the oil in the refrigerant is removed, the refrigerant flows into the condenser 6 through the pipe 5. The refrigerant condensed and liquefied by the condenser 6 flows into the receiver tank 8 through the pipe 7.
[0019]
There is only one outlet 9 for liquid refrigerant from the receiver tank 8. A main circuit 10 is connected to the outlet 9. The main circuit 10 is connected to the filter dryer 11, the moisture indicator 12, the cheese 13, the pipe 14, and the supercooler 15, and then communicates with an evaporator (not shown) through the pipe 16.
[0020]
A cheese 17 is provided downstream of the cheese 13 of the main circuit 10, and an oil cooling circuit 21 is connected to the cheese 17. The oil cooling circuit 21 branches off at the cheese 22 and communicates with the oil cooler 24 through the pipe 23 and then communicates with the intermediate pressure portion 1 b of the compressor 1 through the pipe 25, the cheese 26, and the pipe 27.
[0021]
Oil separated by the oil separator 4 flows into the oil cooler 24 through the pipe 28, and this oil is cooled by the refrigerant flowing through the pipes 23 and 25, and then passed through the oil filter 29 and pipe 30 to the compressor 1. Returned.
[0022]
An injection circuit 31 is connected to the cheese 22 of the oil cooling circuit 21. The injection circuit 31 is connected to the compressor 1 via a pipe 32 and an expansion valve 33. When the temperature detected by the temperature sensor 33a reaches a predetermined temperature or more, the expansion valve 33 is opened, and the compressor is connected via the injection circuit 31. 1 is supplied with a cooling refrigerant.
[0023]
A supercooling circuit 37 is connected to the cheese 17 of the main circuit 10 via a pipe 34, an expansion valve 35, a supercooler 15, and a pipe 36 to return the refrigerant to the intermediate pressure portion 1b of the compressor 1. In the subcooler 15, the refrigerant flowing through the pipes 14 and 16 (main circuit 10) is supercooled by the refrigerant flowing through the pipes 34 and 36 (supercooling circuit 37).
[0024]
In this embodiment, there is only one outlet for liquid refrigerant from the receiver tank 8, and the main circuit 10 is connected to the outlet 9, and the oil cooling circuit 21 is connected to the main circuit 10 via the cheese 13. And the supercooling circuit 37 is connected.
[0025]
Therefore, unlike the prior art, it is not necessary to provide a plurality of outlets in the receiver tank 8, so that refrigerant leakage from the connection port is suppressed, and the complexity of the refrigerant piping and the like is eliminated. The structure of is simplified.
[0026]
Various devices such as the compressor 1, the oil separator 4, the capacitor 6, and the receiver tank 8 that constitute the refrigerant circuit are housed in a unit case 40 as shown in FIG. 2. The inside of the unit case 40 is partitioned vertically, a machine room 41 is formed at the lower part, and a heat exchange chamber 42 is formed at the upper part. As shown in FIG. 3, capacitors 6 are arranged in a substantially V shape in the heat exchange chamber 42, and a capacitor fan motor 43 is accommodated between the capacitors 6. The condenser 6 includes a plurality of headers 45 and 46, and the refrigerant to the condenser 6 flows in through the inlet header 45 and flows out through the outlet header 46 as shown in FIG. 1.
[0027]
When the air-cooled two-stage compressor is used, the evaporation temperature in the evaporator connected to the refrigeration apparatus is −50 ° C. to −60 ° C. Therefore, since the evaporation pressure becomes a negative pressure, air enters the refrigerant circuit from a pipe connection port or the like, and there is a possibility that the air circulates in the refrigerant circuit.
[0028]
In this embodiment, air purge valves 47 and 48 are provided on the uppermost portions of the inlet side headers 45 in order to purge the air in the refrigerant circuit. The air purge valves 47 and 48 are appropriately opened, thereby releasing the air to the atmosphere. In this embodiment, since the air purge valves 47 and 48 are located at the uppermost part of each inlet side header 45, the air is almost completely purged. Further, since the air purge valves 47 and 48 are provided in each of the inlet side headers 45, the air purge can be performed individually for each of the inlet side headers 45.
[0029]
FIG. 4 shows another embodiment.
[0030]
In FIG. 4, reference numeral 100 denotes a two-stage screw compressor. The two-stage screw compressor 100 includes a high pressure part 100a, an intermediate pressure part 100b, and a low pressure part 100c. The refrigerant sucked into the low pressure part 100c through the suction pipe 102 is compressed by the compressor 100 and discharged from the high pressure part 100a. The discharged refrigerant flows into the condenser 104 through the discharge pipe 103, condenses and liquefies in this condenser 104, and then flows into the receiver tank 106 through the pipe 105. The liquid refrigerant from the receiver tank 106 flows into the evaporator 109 through the electromagnetic valve 107 and the expansion valve 108, and flows into the suction pipe 102 of the compressor 100.
[0031]
A digital pressure switch 111 capable of detecting a negative pressure with a gauge pressure is connected to the low pressure portion 100 c of the two-stage screw compressor 100 through a pipe 110. As shown in FIG. 5, the digital pressure switch 111 includes a pressure sensor 113 using a piezo element or the like, a control unit 114 that can be realized by an 8-bit microcomputer or the like, and a switch 115 including a semiconductor switching element. The switch 115 is connected to an electromagnetic relay 116 for driving the two-stage screw compressor 100. The control unit 114 opens and closes the switch 115 based on the pressure signal from the pressure sensor 113 and a preset pressure value. The microcomputer constituting the control unit 114 is usually provided with an EEPROM (nonvolatile memory), and the pressure value is stored in the memory. Reference numeral 117 denotes a power switch.
[0032]
In general, the evaporator 109 shown in FIG. 4 is built in a cooling coil or the like, and when the temperature inside the refrigerator is high, the temperature rise of the refrigerant in the evaporator 109 increases, so the refrigerant pressure on the outlet side of the evaporator 109 increases. The steam refrigerant is sucked into the low pressure part 100c of the compressor 100 through the suction pipe 102. Therefore, if the low-pressure side pressure of the compressor 100 is detected and control is performed to stop the operation of the two-stage screw compressor 100 when the low-pressure pressure reaches a predetermined value, the temperature in the refrigerator can be controlled.
[0033]
In short, the digital pressure switch 111 that detects the low-pressure side pressure of the two-stage screw compressor 100 controls the “low-pressure cut” of the compressor 100. When stopping the operation of the two-stage screw compressor 100, the solenoid valve 107 is closed, the operation of the compressor 100 is temporarily continued, and the refrigerant is collected in the receiver tank 106 (pump down operation), and then the low pressure After confirming that the side pressure has reached the predetermined value (confirmation of completion of refrigerant recovery), the operation of the compressor 100 is stopped.
[0034]
In this embodiment, the means for detecting the low-pressure side pressure of the compressor 100 is constituted by the digital pressure switch 111 capable of detecting a negative pressure as compared with the conventional one, so in the case of the two-stage screw compressor 100, Even if the pressure of the low-pressure part 100c becomes a negative pressure due to the gauge pressure, the low pressure can be directly detected.
[0035]
Therefore, unlike the prior art, there is no need to detect the pressure of the intermediate pressure portion 100b of the two-stage screw compressor 100 and stop the operation of the compressor 100.
[0036]
By the way, if the low pressure side pressure of the compressor 100 is too low, it will cause a shortage of lubricating oil in the compressor 100 and cause oil deterioration. If the low pressure side pressure of the compressor 100 is too high, the compressor 100 will Although this causes liquid compression, since the low pressure of the two-stage screw compressor 100 is detected almost accurately by adopting the digital pressure switch 111, these problems can be solved all at once.
[0037]
Further, by adopting the digital pressure switch 111, it becomes possible to set the cut-on and cut-off values of the compressor 1 every 0.005 MPa, and the pressure display on the display unit 111a of the digital pressure switch 111 is set every 0.005 MPa. In addition, the ON / OFF pressure difference of the compressor 1 can be set to a minimum of 0.01 MPa.
[0038]
As mentioned above, although this invention was demonstrated based on one Embodiment, it is clear that this invention is not limited to this. In the above embodiment, the condensing unit 1 has been described. However, the invention is not limited to this, and some inventions can be applied to, for example, an outdoor unit of an air conditioner.
[0040]
【The invention's effect】
In the first aspect of the invention, since the air purge valve is located at the uppermost part of the refrigerant pipe, the air is almost completely purged. Further, since the air purge valve is provided in each of the plurality of headers, air purge can be performed for each header individually.
[0041]
In the second aspect of the present invention, the means for detecting the low-pressure side pressure of the compressor is constituted by a digital pressure switch capable of detecting a negative pressure. Even if the pressure becomes negative, the low pressure can be detected almost directly.
[Brief description of the drawings]
FIG. 1 is a refrigerant circuit diagram showing an embodiment of the present invention.
FIG. 2 is a front view of a condensing unit.
FIG. 3 is a cross-sectional view of a heat exchange chamber of a condensing unit.
FIG. 4 is a refrigerant circuit diagram showing another embodiment.
FIG. 5 shows a digital pressure switch.
[Explanation of symbols]
1 Two-stage screw compressor 4 Oil separator 6 Capacitor 8 Receiver tank 9 Outlet 10 Main circuit 21 Oil cooling circuit 24 Oil cooler 31 Injection circuit 37 Supercooling circuit 40 Unit case 42 Heat exchange chamber 43 Capacitor fan motor 45, 46 Header 47 , 48 Air purge valve 100 Two-stage screw compressor 100c Low pressure part 111 Digital pressure switch 111

Claims (2)

  A compressor, an oil separator, a condenser, and a receiver tank are connected by a refrigerant pipe, and a main circuit for supplying liquid refrigerant derived from the receiver tank to an evaporator through a subcooler is provided. The condenser is arranged in a substantially V shape. In addition, each of the capacitors arranged in a substantially V shape is provided with an inlet header and an outlet header, and an air purge valve is provided at the top of each inlet header disposed inside the inlet header and the outlet header. A refrigeration apparatus characterized by that. The compressor is a two-stage screw compressor in which the suction pressure is negative with the gauge pressure, and the digital pressure switch for detecting the pressure on the low-pressure side of the two-stage screw compressor is configured to detect negative pressure. 2. The refrigeration apparatus according to claim 1 , wherein when the detected pressure of the digital pressure switch reaches a predetermined value, the operation of the two-stage screw compressor is stopped.

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