JP2010002173A - Refrigerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerator eliminating a leakage loss caused by a slide valve, improving operation efficiency, and improving an economizer effect. <P>SOLUTION: This refrigerator includes a screw compressor 1, a condenser 2, a main expansion valve 3, an evaporator 4, a supercooling expansion valve 5, and a supercooling heat exchanger 6. A first temperature sensor 21 is provided immediately before upstream of the main expansion valve 3, a second temperature sensor 22 is provided immediately after downstream of the screw compressor 1, and the screw compressor 1 is provided with a pressure sensor 23 detecting the pressure of a delivered refrigerant. A calculation section 24 calculates the supercooling degree of the refrigerant immediately before upstream of the main expansion valve 3 from the results detected by the first temperature sensor 21, the second temperature sensor 22 and the pressure sensor 23. A control section 7 reduces the opening of the supercooling expansion valve 5 as the capability of the refrigerator is a low load (required supercooling degree is small), and controls the capacity of the refrigerator. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus such as an air cooling heat pump chiller.

  Conventionally, as shown in FIG. 3, a refrigeration apparatus includes a screw compressor 101 having a slide valve 101a, a condenser 102, a main expansion valve 103, and an evaporator 104 (Patent No. 1510124). Gazette: see Patent Document 1).

  The screw compressor 101, the condenser 102, the main expansion valve 103, and the evaporator 104 are sequentially connected in an annular shape via the refrigerant flow path 110.

  An economizer channel 111 that connects the refrigerant channel 110 between the condenser 102 and the main expansion valve 103 and the intermediate port of the screw compressor 101 is provided.

  The economizer flow path 111 is provided with a supercooling expansion valve 105 and a supercooling heat exchanger 106. The supercooling heat exchanger 106 is an economizer heat exchanger, and heat between the refrigerant flowing through the refrigerant flow path 110 between the condenser 102 and the main expansion valve 103 and the refrigerant that has passed through the supercooling expansion valve 105. Exchange.

  The capacity control of the refrigeration apparatus is performed by the slide valve 101a of the screw compressor 101. That is, when the capacity of the refrigeration apparatus is set to the full load, as shown in FIG. 4A, the position of the slide valve 101a is set to the full load position, and the refrigerant gas sucked into the groove portion of the screw rotor 101b is taken into Compress without returning. At this time, the refrigerant from the economizer flow path 111 is sucked into the groove portion of the screw rotor 101b through the intermediate port 101c, and the economizer effect can be obtained by preventing overheating of the compressor.

  On the other hand, when the capacity of the refrigeration apparatus is low, as shown in FIG. 4B, the position of the slide valve 101a is set to the low load position, and a part of the refrigerant gas sucked into the groove of the screw rotor 101b is removed from the screw rotor. By returning to the suction side L, the discharge gas amount of the compressor is controlled, and the capacity control is performed. The slide valve 101a is driven by a hydraulic piston or a control motor, and can continuously change the capacity of the screw compressor 101 in accordance with its position.

Japanese Patent No. 1510124

  However, the above-described conventional refrigeration apparatus has a problem that the amount of bypass gas increases and loss increases as the amount of movement of the slide valve 101a from the full load position increases (lower load), resulting in a decrease in operating efficiency. It was.

  Further, when the position of the slide valve 101a moves to the low load side, the intermediate port 101c communicates with the suction side L of the screw rotor, and the refrigerant from the economizer channel 111 leaks to the suction side L of the screw rotor. Therefore, there is a problem that the economizer effect is reduced.

  Therefore, an object of the present invention is to provide a refrigeration apparatus that can eliminate the loss of leakage due to the slide valve, improve the operation efficiency, and improve the economizer effect.

In order to solve the above problems, the refrigeration apparatus of the present invention provides:
A screw compressor having a slide valve for controlling the capacity by returning the sucked refrigerant to the suction side;
A condenser,
A main expansion mechanism;
With an evaporator,
An economizer flow path connecting a refrigerant flow path between the condenser and the main expansion mechanism and an intermediate port of the screw compressor is provided;
The economizer flow path includes a supercooling expansion mechanism, a heat exchanger that performs heat exchange between the refrigerant flowing through the refrigerant flow path between the condenser and the main expansion mechanism, and the refrigerant that has passed through the supercooling expansion mechanism. A cooling heat exchanger,
A supercooling degree detection unit for detecting the degree of supercooling of the refrigerant in the refrigerant flow path between the main expansion mechanism and the supercooling heat exchanger;
And a controller that controls the opening degree of the supercooling expansion mechanism so that the degree of supercooling detected by the supercooling degree detector is a set value.

  According to the refrigeration apparatus of the present invention, the control unit controls the opening degree of the supercooling expansion mechanism so that the supercooling degree detected by the supercooling degree detection unit becomes the set value. The capacity of the refrigeration apparatus is controlled by reducing the degree of opening of the supercooling expansion mechanism as the capacity of the apparatus is low (the required degree of supercooling is small).

  In other words, capacity control is performed by controlling the degree of supercooling that can be obtained by a supercooling heat exchanger (economizer), and thereby the slide valve is positioned closer to the full load than the conventional slide. In the case of capacity control using only the valve, the amount of bypass increases as the load becomes lower, and the compressor performance and the economizer effect are suppressed from being reduced, so that the efficiency from the middle to the low load can be improved.

  Therefore, the loss of leakage due to the slide valve can be eliminated, the operation efficiency can be improved, and the economizer effect can be improved.

  In one embodiment, the economizer channel is connected to a bypass channel that bypasses the supercooling expansion mechanism and the supercooling heat exchanger, and the bypass channel is electrically connected to the bypass channel. A drive valve is provided.

  According to the refrigeration apparatus of this embodiment, the economizer flow path is connected to a bypass flow path that bypasses the supercooling expansion mechanism and the supercooling heat exchanger, and an electrically driven valve is connected to the bypass flow path. Therefore, as the capacity of the refrigeration system becomes low, the opening degree of the supercooling expansion mechanism becomes smaller, the amount of intermediate injection into the screw compressor is reduced, and the discharge temperature of the screw compressor is reduced. Even when the problem of rising occurs, it is possible to prevent the overheating of the screw compressor by opening the electric drive valve and bypassing the liquid refrigerant to the screw compressor.

  Moreover, in the refrigeration apparatus of one embodiment, the electric drive valve is controlled based on the temperature of the refrigerant discharged from the screw compressor.

  According to the refrigeration apparatus of this embodiment, since the electrically driven valve is controlled based on the temperature of the refrigerant discharged from the screw compressor, the electrically driven valve has a discharge temperature of the screw compressor of a predetermined value. When the value exceeds the upper limit, the screw compressor is opened to prevent overheating of the screw compressor.

  Further, in the refrigeration apparatus of one embodiment, when the required load is in the first region, the control unit at least the excess of the opening of the expansion mechanism for supercooling or the opening of the slide valve. While controlling the opening of the cooling expansion mechanism to control the capacity, when the required load is in the second area smaller than the first area, the opening of the slide valve is controlled to To control.

  According to the refrigeration apparatus of this embodiment, when the required load is in the first region, the control unit at least the excess of the opening of the supercooling expansion mechanism or the opening of the slide valve. While controlling the opening of the cooling expansion mechanism to control the capacity, when the required load is in the second area smaller than the first area, the opening of the slide valve is controlled to Therefore, when the required load is in the first region, the capacity can be controlled without relying on the slide valve, or the slide valve can be operated with a small opening, and the loss due to the slide valve bypass. Can be reduced.

  According to the refrigeration apparatus of the present invention, the control unit controls the opening degree of the supercooling expansion mechanism so that the supercooling degree detected by the supercooling degree detection unit becomes the set value. Loss can be eliminated, driving efficiency can be improved, and the economizer effect can be improved.

It is a simplified lineblock diagram showing one embodiment of the refrigerating device of the present invention. It is a conversion table of the saturation temperature from a high pressure when a refrigerant | coolant is R407C. It is a conversion table of the saturation temperature from the low pressure when the refrigerant is R407C. It is a simplified block diagram which shows the conventional freezing apparatus. It is effect | action explanatory drawing which shows the case where the capacity | capacitance of a freezing apparatus is made into full load. It is effect | action explanatory drawing which shows the case where the capacity | capacitance of a freezing apparatus is made into low load. It is explanatory drawing explaining control with respect to the load of a slide valve and the expansion valve for supercooling.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 shows a simplified configuration diagram as an embodiment of the refrigeration apparatus of the present invention. This refrigeration apparatus includes a screw compressor 1 having a slide valve 1a, a condenser 2, a main expansion valve 3 (as a main expansion mechanism), and an evaporator 4.

  The screw compressor 1, the condenser 2, the main expansion valve 3, and the evaporator 4 are sequentially connected in an annular shape via the refrigerant flow path 10. As shown by the arrows, the refrigerant flows through the screw compressor 1, the condenser 2, the main expansion valve 3, and the evaporator 4 in order.

  Since the screw compressor 1 and the slide valve 1a are the same as the screw compressor 101 and the slide valve 101a of FIGS. 4A and 4B described in the background art above, description thereof is omitted. That is, the slide valve 1a controls the capacity by returning the sucked refrigerant to the suction side.

  The condenser 2 is provided with a fan, and performs heat exchange between the air sent by the fan and the refrigerant in the refrigerant flow path 10.

  The evaporator 4 is provided with a water flow path, and performs heat exchange between the water flowing through the water flow path and the refrigerant in the refrigerant flow path 10. As the evaporator 4, for example, a plate heat exchanger is used, but a double tube heat exchanger, a shell and tube heat exchanger, or the like may be used.

  An economizer flow path 11 that connects the refrigerant flow path 10 between the condenser 2 and the main expansion valve 3 and the intermediate port of the screw compressor 1 (the intermediate port 101c in FIGS. 4A and 4B) is provided.

  The economizer flow path 11 is provided with a supercooling expansion valve 5 (as a supercooling expansion mechanism) and a supercooling heat exchanger 6. For example, an electronic expansion valve is used as the subcooling expansion valve 5.

  The supercooling heat exchanger 6 is disposed closer to the screw compressor 1 than the supercooling expansion valve 5 is. The supercooling heat exchanger 6 is an economizer heat exchanger, and exchanges heat between the refrigerant flowing through the refrigerant flow path 10 between the condenser 2 and the main expansion valve 3 and the refrigerant that has passed through the supercooling expansion valve 5. I do.

  The supercooling heat exchanger 6 cools the refrigerant in the refrigerant flow path 10 between the condenser 2 and the main expansion valve 3. Further, as shown in FIGS. 4A and 4B described in the background art above, the refrigerant in the economizer channel 11 is sucked into the groove portion of the screw rotor 101b through the intermediate port 101c to prevent overheating of the compressor. The economizer effect can be obtained.

  In the refrigerant flow path 10 between the supercooling heat exchanger 6 and the main expansion valve 3, a first temperature sensor 21 is provided immediately upstream of the main expansion valve 3, and the first temperature sensor 21 is connected to the refrigerant flow. The temperature of the refrigerant in the passage 10 is detected.

  A second temperature sensor 22 is provided in the refrigerant flow path 10 between the screw compressor 1 and the condenser 2 immediately after the downstream side of the screw compressor 1, and the second temperature sensor 22 is provided in the refrigerant flow path 10. The refrigerant temperature is detected.

  The screw compressor 1 is provided with a pressure sensor 23 that detects the pressure of the discharged refrigerant. The pressure sensor 23 detects the pressure of the refrigerant discharged from the screw compressor 1.

  From the detection results of the first temperature sensor 21, the second temperature sensor 22, and the pressure sensor 23, the degree of supercooling of the refrigerant in the refrigerant flow path 10 between the supercooling heat exchanger 6 and the main expansion valve 3 is calculated by the calculation unit 24. Is calculated. That is, the arithmetic unit 24 detects the degree of supercooling of the refrigerant immediately before the upstream side of the main expansion valve 3.

  In short, the 1st temperature sensor 21, the 2nd temperature sensor 22, the pressure sensor 23, and the calculating part 24 comprise a supercooling degree detection part, and this supercooling degree detection part is the heat exchanger 6 for supercooling, and main expansion. The degree of supercooling of the refrigerant in the refrigerant flow path 10 between the valves 3 is detected.

  The controller 7 controls the opening degree of the supercooling expansion valve 5 so that the supercooling degree detected by the supercooling degree detection unit becomes a set value. The control unit 7 includes a calculation unit 24.

  A bypass flow path 12 that bypasses the supercooling expansion valve 5 and the supercooling heat exchanger 6 is connected to the economizer flow path 11. The bypass flow path 12 connects the upstream side of the supercooling expansion valve 5 and the downstream side of the supercooling heat exchanger 6.

  The bypass passage 12 is provided with an electromagnetic valve 8 (as an electrically driven valve). The electromagnetic valve 8 is controlled based on the temperature of the refrigerant discharged from the screw compressor 1. That is, the control unit 7 controls the electromagnetic valve 8 based on the detection result of the second temperature sensor 22.

  Next, capacity control of the refrigeration apparatus having the above-described configuration will be described. The lower the load of the refrigeration apparatus (the smaller the required degree of supercooling), the smaller the opening degree of the supercooling expansion valve 5 is made by the control unit 7. Then, the capacity control of the refrigeration apparatus is performed. At this time, the position of the slide valve 1a is at the full load position as shown in FIG. 4A, and the refrigerant gas sucked into the groove portion of the screw rotor 101b is compressed without returning to the suction side L of the compressor.

  Here, the capacity of the refrigeration system depends on the degree of supercooling immediately before the main expansion valve 3 that can be obtained by the condenser 2 and the supercooling heat exchanger 6. In other words, the capacity is determined by the degree of supercooling that can be obtained by the heat exchanger 6 for supercooling.

  Thus, by controlling the degree of supercooling immediately before the main expansion valve 3 by controlling the opening degree of the supercooling expansion valve 5, the capacity control is performed without depending on the slide valve 1a. Even if the main expansion valve 3 is fully closed, if load reduction is required, capacity control is performed by the conventional slide valve shown in FIG. 4B.

  Next, a method for detecting the degree of supercooling of the refrigerant immediately before the main expansion valve 3 by the calculation unit 24 will be described.

  First, the temperature of the refrigerant is detected by the first temperature sensor 21 and the second temperature sensor 22, and the pressure of the refrigerant is detected by the pressure sensor 23.

  Then, the equivalent saturation temperature for the pressure detected by the pressure sensor 23 is obtained using the conversion tables shown in FIGS. 2A and 2B. 2A shows a conversion table for saturation temperature from high pressure when the refrigerant is R407C, and FIG. 2B shows a conversion table for saturation temperature from low pressure when the refrigerant is R407C.

  Thereafter, the subcooling degree of the refrigerant immediately before the main expansion valve 3 is obtained by subtracting the temperature immediately before the main expansion valve 3 detected by the first temperature sensor 21 from the equivalent saturation temperature.

  In addition, by subtracting the corresponding saturation temperature from the temperature immediately after the screw compressor 1 detected by the second temperature sensor 22, the degree of superheat of the refrigerant gas discharged from the screw compressor 1 is obtained, and the screw compressor 1 Detect state.

  According to the refrigeration apparatus having the above configuration, the control unit 7 controls the opening degree of the supercooling expansion valve 5 so that the supercooling degree detected by the supercooling degree detection unit becomes the set value. The capacity of the refrigerating apparatus is controlled by decreasing the opening degree of the supercooling expansion valve 5 as the capacity of the refrigerating apparatus is lower (the required degree of supercooling is smaller).

  As a result, the position of the slide valve 1a is positioned closer to the full load than the conventional one, and in the case of capacity control using only the conventional slide valve 1a, the amount of bypass increases as the load becomes lower, reducing the compressor performance and the economizer effect. It is possible to improve the efficiency from middle to low load.

  Therefore, the loss of leakage due to the slide valve 1a can be eliminated, the operating efficiency can be improved, and the economizer effect can be improved.

  The economizer flow path 11 is provided with a bypass flow path 12 that communicates the refrigerant flow path 10 between the condenser 2 and the main expansion valve 3 and the screw compressor 1. Since the valve 8 is provided, the opening degree of the supercooling expansion valve 5 is reduced as the capacity of the refrigeration system is reduced, and the amount of intermediate injection into the screw compressor 1 is reduced. Even when the discharge temperature of the machine 1 rises, the solenoid valve 8 can be opened and the liquid refrigerant can be bypassed to the screw compressor 1 to prevent overheating of the screw compressor 1.

  Further, since the solenoid valve 8 is controlled based on the temperature of the refrigerant discharged from the screw compressor 1, the solenoid valve 8 is opened when the discharge temperature of the screw compressor 1 exceeds a predetermined value. Thus, overheating of the screw compressor 1 can be prevented.

  Next, the control of the slide valve 1a and the supercooling expansion valve 5 by the control unit 7 will be described with reference to FIG. In FIG. 5, the abscissa indicates the required load, and the ordinate indicates the COP change rate, the compressor load, the control value of the supercooling degree, and the opening / closing of the electromagnetic valve 8 in the bypass flow path 12.

  Here, the load ranges from 100% to the first set value as the high load region Z0, and the load ranges from the first set value to the second set value smaller than the first set value. The area is Z1, and the range where the load is from the second set value to 0% is the second area Z2. A range obtained by adding the first region Z1 and the second region Z2 is a third region Z3 with a low load.

  The compressor load indicates the opening degree of the slide valve 1a, and decreasing the compressor load means increasing the opening degree of the slide valve 1a. The compressor load of 100% indicates a fully closed state (full load state) of the slide valve 1a.

  The control value of the degree of supercooling indicates the opening degree of the supercooling expansion valve 5, and reducing the control value of the degree of supercooling means that the opening degree of the supercooling expansion valve 5 is reduced. To do. The supercooling degree control value 0 indicates the fully closed state of the supercooling expansion valve 5.

  As shown in FIG. 5, the control unit 7 performs normal control when the required load is within the high load region Z0, and controls the supercooling degree control value (opening degree of the supercooling expansion valve 5). ) Is constant, the compressor load (the opening degree of the slide valve 1a) is changed, and the electromagnetic valve 8 is closed.

  Further, when the required load is in the first region Z1, the control unit 7 changes the control value of the degree of supercooling (the degree of opening of the supercooling expansion valve 5) as indicated by the solid line, and compresses The machine load (opening degree of the slide valve 1a) is set to a change (opening degree) smaller than the change (opening degree) in the high load region Z0 as indicated by a solid line, and the electromagnetic valve 8 is closed. That is, in the first region Z1, the opening degree of the supercooling expansion valve 5 and the opening degree of the slide valve 1a are controlled, and the slide valve 1a is opened more than in the case where the supercooling degree is constant in the high load region Z0. Control the degree in a smaller state.

  Further, when the required load is in the second region Z2, the control unit 7 sets the control value of the degree of supercooling (the degree of opening of the supercooling expansion valve 5) to 0 as indicated by a solid line (that is, , The economizer flow path 11 is closed), the compressor load (the opening degree of the slide valve 1a) is changed as indicated by the solid line, and the electromagnetic valve 8 is opened. That is, in the second region Z2, the opening degree of the slide valve 1a is controlled to control the capacity.

  Here, in the third region Z3, when normal control similar to the control in the high load region Z0 is performed, the control value of the degree of supercooling becomes constant as shown by the phantom line, and the compressor load is As shown by the line, the COP change rate is low as shown by the phantom line.

  However, in the third region Z3, by controlling the supercooling degree control value and the compressor load as shown by the solid line as described above, the COP change rate can be improved as shown by the solid line. That is, when the load falls within the first region Z1 with respect to the required load reduction, the opening degree of the slide valve 1a is reduced by controlling the opening degree of the supercooling expansion valve 5. Thus, the capacity can be controlled, and the loss due to the bypass of the slide valve 1a can be reduced.

  In the first region Z1, the compressor load (the opening degree of the slide valve 1a) may be constant. That is, in the first region Z1, the capacity may be controlled by controlling only the opening degree of the supercooling expansion valve 5 without depending on the slide valve 1a. Therefore, the loss due to the bypass of the slide valve 1a can be further reduced.

  In addition, this invention is not limited to the above-mentioned embodiment. For example, the bypass flow path 12 and the electromagnetic valve 8 may not be provided. The main expansion mechanism may be a capillary tube in addition to the main expansion valve 3. In addition to the electromagnetic valve 8, an electrically driven valve may be used as the electrically driven valve.

1 Screw compressor 1a Slide valve 2 Condenser 3 Main expansion valve (main expansion mechanism)
4 Evaporator 5 Supercooling expansion valve (Supercooling expansion mechanism)
6 Heat exchanger for supercooling 7 Control unit 8 Solenoid valve (electrically driven valve)
DESCRIPTION OF SYMBOLS 10 Refrigerant flow path 11 Economizer flow path 12 Bypass flow path 21 1st temperature sensor (supercooling degree detection part)
22 2nd temperature sensor (supercooling degree detection part)
23 Pressure sensor (supercooling degree detector)
24 Calculation unit (supercooling degree detection unit)
Z1 first region Z2 second region

Claims (4)

A screw compressor (1) having a slide valve (1a) for controlling the capacity by returning the sucked refrigerant to the suction side;
A condenser (2),
A main expansion mechanism (3);
An evaporator (4),
An economizer channel (11) connecting the refrigerant channel (10) between the condenser (2) and the main expansion mechanism (3) and the intermediate port of the screw compressor (1) is provided;
The economizer flow path (11) includes a supercooling expansion mechanism (5), a refrigerant flowing through the refrigerant flow path (10) between the condenser (2) and the main expansion mechanism (3), and the excessive flow. A supercooling heat exchanger (6) that performs heat exchange with the refrigerant that has passed through the cooling expansion mechanism (5),
Supercooling degree detection units (21, 22, 23, 24) for detecting the degree of supercooling of the refrigerant in the refrigerant flow path (10) between the main expansion mechanism (3) and the supercooling heat exchanger (6). When,
A control unit (7) for controlling the opening degree of the supercooling expansion mechanism (5) so that the supercooling degree detected by the supercooling degree detection unit (21, 22, 23, 24) becomes a set value; A refrigeration apparatus comprising: The refrigeration apparatus according to claim 1,
The economizer channel (11) is connected to a bypass channel (12) that bypasses the supercooling expansion mechanism (5) and the supercooling heat exchanger (6),
An electrical drive valve (8) is provided in the bypass channel (12). The refrigeration apparatus according to claim 2,
The electric drive valve (8) is controlled based on the temperature of the refrigerant discharged from the screw compressor (1). The refrigeration apparatus according to any one of claims 1 to 3,
When the required load is in the first region (Z1), the control unit (7) has at least one of the opening degree of the supercooling expansion mechanism (5) and the opening degree of the slide valve (1a). When the required load is in the second region (Z2) smaller than the first region (Z1) while controlling the capacity by controlling the opening degree of the expansion mechanism (5) for supercooling, the above A refrigerating apparatus for controlling the capacity by controlling the opening of the slide valve (1a).

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