Refrigeration system and method of controlling the same

Abstract

The application provides a refrigeration system and a control method thereof. The refrigeration system comprises a compressor, a condenser, an evaporator, an economizer, a downstream throttling valve and a control device, wherein the compressor, the condenser and the evaporator are sequentially connected; the economizer is arranged between the condenser and the evaporator and is controllably connected with the compressor through a gas supplement channel; the downstream throttling valve is arranged between the economizer and the evaporator; and the control device is connected with the downstream throttling valve and is configured to control the flow of the downstream throttling valve according to a refrigeration system pressure parameter when the gas supplement channel of the economizer is closed, so as to control the liquid level height of the economizer. The control device in the application can accurately adjust the liquid level height of the economizer.

Description

Technical Field

[0001] This application relates to a refrigeration system, and more particularly to a refrigeration system including an economizer and a control method thereof. Background Technology

[0002] A typical refrigeration system includes a compressor, condenser, throttling device, and evaporator, which are connected in sequence to form a refrigerant circulation system for cooling or heating. In the refrigeration system, the refrigerant is compressed into a high-temperature, high-pressure refrigerant gas by the compressor. The high-temperature, high-pressure refrigerant gas discharged from the compressor releases heat in the condenser, where it is liquefied and condenses into a high-pressure refrigerant liquid. This high-pressure refrigerant liquid flows into the throttling device, which reduces its pressure to a low-pressure refrigerant liquid. The low-pressure refrigerant liquid absorbs heat in the evaporator and vaporizes to obtain a low-pressure refrigerant gas. Finally, the low-pressure refrigerant gas re-enters the compressor, completing the refrigerant cycle.

[0003] Some refrigeration systems also include an economizer, which separates the gas and liquid refrigerant after it passes through the upstream throttling device. The gaseous refrigerant returns to the compressor's gas supply port, while the liquid refrigerant passes through the downstream throttling device and enters the evaporator for evaporation. Both the upstream and downstream throttling devices are adjustable flow devices, and by adjusting them, the liquid level in the economizer can be controlled within a certain range. Summary of the Invention

[0004] This application provides a refrigeration system, including: a compressor, a condenser, an evaporator, an economizer, a downstream expansion valve, and a control device, wherein the compressor, condenser, and evaporator are connected in sequence; the economizer is disposed between the condenser and the evaporator, and is controllably connected to the compressor via a gas supply channel; the downstream expansion valve is disposed between the economizer and the evaporator; the control device is connected to the downstream expansion valve, and the control device is configured to control the flow rate of the downstream expansion valve based on refrigeration system pressure parameters when the gas supply channel of the economizer is closed, thereby controlling the liquid level height of the economizer.

[0005] In the refrigeration system described above, the pressure parameters include the pressure of the economizer and the target pressure.

[0006] In the refrigeration system described above, the control device is configured to: receive signals of the operating parameters of the refrigeration system and signals of the pressure of the economizer; calculate the target pressure based on the operating parameters; compare the difference between the target pressure and the economizer pressure; and adjust the flow rate of the downstream throttle valve according to the difference.

[0007] In the refrigeration system described above, the operating parameters include high-pressure side pressure and low-pressure side pressure.

[0008] In the refrigeration system described above, the operating parameters also include the liquid level height of the economizer.

[0009] The refrigeration system described above includes a high-pressure side pressure sensor, a low-pressure side pressure sensor, and an economizer pressure sensor. The high-pressure side pressure sensor is located in the compressor's discharge pipe or at the condenser. The low-pressure side pressure sensor is located in the compressor's suction pipe or at the evaporator. The economizer pressure sensor is located at the economizer. The high-pressure side pressure and the low-pressure side pressure are sensed by the high-pressure side pressure sensor and the low-pressure side pressure sensor, respectively. The economizer pressure is sensed by the economizer pressure sensor.

[0010] In the refrigeration system described above, the economizer further includes a liquid level sensor capable of sensing the liquid level height of the economizer, and the control device is configured to calculate the target pressure based on the high-pressure side pressure, the low-pressure side pressure, and the difference between the liquid level height of the economizer sensed by the liquid level sensor and the target liquid level height.

[0011] This application also provides a refrigeration system control method, the refrigeration system including a compressor, a condenser, an evaporator, an economizer, and a downstream throttle valve, characterized in that the method includes the following steps: receiving signals of operating parameters of the refrigeration system and signals of pressure P1 of the economizer; calculating a target pressure P2 based on the operating parameters; comparing the difference between the target pressure P2 and the economizer pressure P1; and adjusting the flow rate of the downstream throttle valve according to the difference.

[0012] In the refrigeration system control method described above, the operating parameters include the high-pressure side pressure P3 and the low-pressure side pressure P4 of the refrigeration system, and the target pressure P2 = , where C1 is the first control coefficient.

[0013] The refrigeration system control method described above includes the high-pressure side pressure P3, the low-pressure side pressure P4, and the liquid level height L1 of the economizer, with the target pressure P2 = Where L2 is the target liquid level height of the economizer, C1 is the first control coefficient, and C2 is the second control coefficient.

[0014] As described above, in the refrigeration system control method, when adjusting the flow rate of the downstream throttling valve, a proportional-integral control method is used to control the adjustment range of the downstream throttling valve.

[0015] The refrigeration system control method described above is executed when the economizer gas supply channel is closed.

[0016] In this application, when the gas supply channel of the economizer is closed, the downstream throttle valve is controlled according to the high-pressure side pressure and low-pressure side pressure of the refrigeration system, which can more accurately adjust the liquid level of the economizer and avoid large fluctuations in the liquid level of the economizer. Attached Figure Description

[0017] Figure 1A This is a schematic diagram of the component connections of the refrigeration system in this application;

[0018] Figure 1B yes Figure 1A Schematic diagram of the components and control devices of the central refrigeration system;

[0019] Figure 2 This is a flowchart of the refrigeration system control method in this application;

[0020] Figure 3 for Figure 1B The diagram shows a schematic block diagram of the control device. Detailed Implementation

[0021] Various specific embodiments of this application will now be described with reference to the accompanying drawings, which form part of this specification. It should be understood that although directional terms such as "front," "rear," "upper," "lower," "left," "right," "top," and "bottom" are used in this application to describe the orientation of various example structural parts and elements, their use herein is merely for illustrative purposes and is based on the example orientations shown in the accompanying drawings. Since the embodiments disclosed in this application can be arranged in different orientations, these directional terms are for illustrative purposes only and should not be considered limiting. Where possible, the same or similar reference numerals used in this application refer to the same parts.

[0022] Figure 1A This is a schematic diagram of the component connections of the refrigeration system in this application. Figure 1B yes Figure 1A A schematic diagram of the components and control devices of the central refrigeration system. (Example) Figure 1AAs shown, the refrigeration system 100 includes a compressor 110, a condenser 101, an upstream expansion valve 105, an economizer 103, a downstream expansion valve 104, and an evaporator 102, which are connected sequentially by pipes to form a refrigerant circulation loop. Specifically, the compressor 110 has a suction port 111, a discharge port 112, and a make-up port 113. The condenser 101 has an inlet 115 and an outlet 116. The upstream expansion valve 105 has an inlet 151 and an outlet 152. The downstream expansion valve 104 has an inlet 141 and an outlet 142. The evaporator 102 has an inlet 121 and an outlet 122. The economizer 103 has an inlet 131, a first outlet 132, and a second outlet 133.

[0023] The discharge port 112 of compressor 110 is connected to the inlet 115 of condenser 101. The outlet 116 of condenser 101 is connected to the inlet 131 of upstream throttle valve 105. The first outlet 132 of upstream throttle valve 105 is connected to the inlet 131 of economizer 103. The first outlet 132 of economizer 103 is connected to the compressor's air supply port 113, and the second outlet 133 of economizer 103 is connected to the inlet 141 of downstream throttle valve 104. The outlet 142 of downstream throttle valve 104 is connected to the inlet 121 of evaporator 102. The outlet 122 of evaporator 102 is connected to the suction port 111 of compressor 110.

[0024] The refrigeration system 100 is filled with refrigerant, which circulates within the system to achieve cooling or heating. In the compressor 110, the low-temperature, low-pressure gaseous refrigerant is compressed into a high-temperature, high-pressure gaseous refrigerant. This high-temperature, high-pressure gaseous refrigerant then flows into the condenser 101, where it releases heat and condenses into a high-pressure liquid refrigerant. The high-pressure liquid refrigerant, after its pressure is reduced by the upstream expansion valve 105, enters the economizer 103. In the economizer 103, the liquid refrigerant undergoes heat exchange; a portion of the refrigerant is further cooled into a subcooled liquid refrigerant, which then flows from the second outlet 133 to the downstream expansion valve 104. The remaining portion of the refrigerant is converted into a gaseous refrigerant and flows from the first outlet 132 through the gas supply channel 139 to the gas supply port 113 of the compressor 110. The refrigerant flowing from the second outlet 133 of the economizer 103 is throttled by the downstream expansion valve 104 and enters the evaporator 102, where it absorbs heat and evaporates into gaseous refrigerant, which then flows to the suction port 111 of the compressor 110. The compressor 110 compresses the gaseous refrigerant from the evaporator 102 and the economizer 103, converting it into a high-temperature, high-pressure gaseous refrigerant. This process is repeated continuously, completing a continuous refrigeration cycle.

[0025] like Figure 1A and Figure 1BAs shown, the refrigeration system 100 also includes a low-pressure side pressure sensor 127, a high-pressure side pressure sensor 128, an economizer pressure sensor 129, and a control device 150. The low-pressure side pressure sensor 127 and the high-pressure side pressure sensor 128 are used to detect the low-pressure side pressure and high-pressure side pressure of the refrigeration system 100, respectively. The economizer pressure sensor 129 is used to detect the internal pressure of the economizer. In one embodiment of this application, the low-pressure side pressure sensor 127 is installed on the compressor's suction line 181 to detect the suction pressure of the compressor 110, which is the low-pressure side pressure of the refrigeration system 100. The high-pressure side pressure sensor 128 is installed on the compressor's discharge line 182 to detect the discharge pressure of the compressor 110, which is the high-pressure side pressure of the refrigeration system 100. A gas supply valve 140 is provided on the gas supply channel 139 between the economizer 103 and the compressor 110. The gas supply valve 140 can be opened or closed to connect or disconnect the gas supply channel of the economizer 103. Upstream throttling valve 105 and downstream throttling valve 104 are flow-adjustable valves. During the operation of the refrigeration system, the gas supply valve 140 is closed or opened as needed. The low-pressure side pressure, high-pressure side pressure, and economizer pressure are all pressure parameters of the refrigeration system.

[0026] The control device 150 is connected to the low-pressure side pressure sensor 127, the high-pressure side pressure sensor 128, and the economizer pressure sensor 129, and can receive pressure signals from these sensors. The control device 150 is connected to the upstream throttle valve 105 and the downstream throttle valve 104, and can adjust the opening of the upstream and downstream throttle valves 105, thereby regulating their flow rates. The control device 150 is connected to the make-up air valve 140, and can open or close the make-up air valve 140. The upstream throttle valve 105 controls the liquid level in the condenser 101 and affects the liquid level in the economizer 103, while the downstream throttle valve 104 controls the liquid level in the economizer 103.

[0027] In the refrigeration system shown in this application, both the upstream throttle valve 105 and the downstream throttle valve 104 are adjustable throttle valves. When the gas supply valve 140 is open and the gas supply channel 139 is connected, the economizer 103 is connected to the compressor 110, and its internal pressure remains stable. By adjusting the downstream throttle valve 104 according to the liquid level of the economizer 103 or system parameters (subcooling, dryness, superheat), the liquid level of the economizer 103 can be controlled within a certain range. When the gas supply valve 140 is closed, cutting off the gas supply channel 139, the economizer 103 and the compressor 110 are disconnected. The pressure of the economizer 103 is no longer directly related to the gas supply pressure, but is affected by the opening degree of the upstream throttle valve 105 and the downstream throttle valve 104. In some existing applications of this application, if the downstream throttle valve 104 is opened to a specific degree when the gas supply channel 139 of the economizer 103 is disconnected, the fixed opening degree is difficult to meet the current state of the unit due to different operating conditions and unit loads. This can result in the evaporator pressure being too low due to an excessively small opening, or the compressor 110 drawing in liquid due to an excessively large opening. If the downstream throttle valve 104 is adjusted according to the liquid level of the economizer 103, the adjustment of the downstream throttle valve 104 is accompanied by changes in the internal pressure of the economizer 103, causing large fluctuations in the liquid level within the economizer 103. This can lead to the downstream throttle valve 104 being adjusted too frequently, or the target liquid level cannot be achieved by adjusting only the upstream throttle valve 105 and the downstream throttle valve 104. Furthermore, when the gas supply channel 139 of the economizer 103 is restored from closed to open, the internal pressure of the economizer 103 quickly reaches the gas supply pressure, and the pressure fluctuates greatly. This causes a large change and violent fluctuation in the liquid level of the economizer 103, which may lead to liquid carryover in the compressor 110 and large load fluctuations.

[0028] In this application, when the gas supply valve 140 is open, the downstream throttle valve 104 is adjusted according to the liquid level of the economizer 103 or other parameters. When the gas supply valve 140 is closed, the adjustment of the downstream throttle valve 104 refers to the high-pressure side pressure, the low-pressure side pressure, and the pressure of the economizer 103, enabling relatively stable adjustment and avoiding large pressure fluctuations within the economizer. In this application, the adjustment of the upstream throttle valve 105 also refers to the liquid level of the economizer 103 or other parameters.

[0029] Figure 2 This is a flowchart of the refrigeration system control method in this application. For example... Figure 2 As shown, the control method in this application includes the following steps: 201: receiving signals of the operating parameters of the refrigeration system and the pressure P1 signal of the economizer; 202: calculating the target pressure P2 based on the operating parameters; 203: comparing the difference between the target pressure P2 and the economizer pressure P1; 204: adjusting the flow rate of the downstream throttle valve 104 according to the difference.

[0030] In step 201, the operating parameters of the refrigeration system include high-pressure side pressure P3 and low-pressure side pressure P4, which are sensed by high-pressure side pressure sensor 128 and low-pressure side pressure sensor 127, respectively. High-pressure side pressure P3 and low-pressure side pressure P4 are the exhaust pressure and intake pressure, or the condensing pressure and evaporating pressure, respectively. Economizer pressure P1 is sensed by economizer pressure sensor 129. The signals of high-pressure side pressure P3, low-pressure side pressure P4, and economizer pressure P1 are all received by control device 150. In some embodiments, the operating parameters of the refrigeration system include high-pressure side pressure P3, low-pressure side pressure P4, and the liquid level L1 of economizer 103, which is sensed by economizer level sensor.

[0031] In step 202, according to the first embodiment of this application, the target pressure P2 = C1 is the first control coefficient. C1 is set within the range of 0.5 to 1.5, with a default value of 1. In the first embodiment, the target pressure P2 is only related to the high-pressure side pressure P3 and the low-pressure side pressure P4. According to the second embodiment of this application, P2 = Where L2 is the target liquid level height of the economizer, C1 is the first control coefficient, and C2 is the second control coefficient. The setting range of C1 is 0.5~1.5, and the default value is 1. The setting range of C2 is 0~10kPa, and the default value is 0.5kPa. In the second embodiment, the target pressure P2 is related not only to the high-pressure side pressure P3 and the low-pressure side pressure P4, but also to the current liquid level height and the target liquid level height of the economizer 103.

[0032] In step 203, the control device 150 compares the difference between the target pressure P2 and the economizer pressure P1 to obtain a comparison result. The economizer pressure P1 is greater than, equal to, or less than the target pressure P2.

[0033] In step 204, the opening of the downstream throttle valve 104 is adjusted based on the comparison result of step 203. When the target pressure P2 is greater than the economizer pressure P1, the opening of the downstream throttle valve 104 is reduced, causing the internal pressure of the economizer to increase. When the target pressure P2 is less than the economizer pressure P1, the opening of the downstream throttle valve 104 is increased, causing the internal pressure of the economizer to decrease. When the target pressure P2 is equal to the economizer pressure P1, the current opening of the downstream throttle valve 104 is maintained without adjustment. Furthermore, when adjusting the downstream throttle valve 104, the difference between P2 and P1 is taken into account. When the control device 150 adjusts the downstream throttle valve 104, a proportional-integral control (PI control) strategy is used for adjustment.

[0034] After step 204 is completed, return to the beginning of the method and continue execution. Figure 2The method shown. That is, during the operation of the refrigeration system, Figure 2 The method shown is executed cyclically to dynamically adjust the opening of the downstream throttle valve 104.

[0035] Figure 3 for Figure 1B The diagram shows a schematic block diagram of the control device. Figure 3 As shown in the illustration, as one embodiment, the control device 150 includes a bus 300, a processor 301, an input interface 302, an output interface 303, and a memory 304 containing a control program. The various components of the control device 150, including the processor 301, input interface 302, output interface 303, and memory 304, are communicatively connected to the bus 300, enabling the processor 301 to control the operation of the input interface 302, output interface 303, and memory 304. Specifically, the memory 304 stores programs (e.g., first control parameter C1, second control parameter C2), instructions, and data, while the processor 301 reads programs, instructions, and data from the memory 304 and writes data to the memory 304. By executing the program and instructions read from the memory 304, the processor 301 controls the operation of the memory 304, input interface 302, and output interface 303. The input interface 302 can convert signals received from external devices into signals that the processor 301 can recognize and process, while the output interface 303 can convert signals output by the processor 301 into signals suitable for external devices. Figure 3 As shown, the signal processing unit receives high-pressure signals from the high-pressure side pressure sensor 128 and low-pressure side pressure sensor 127 via input interface 302, and converts the received exhaust pressure signals and intake pressure signals into digital signals that can be recognized and processed by the processor 301. These digital signals are stored in memory 304 for later processing. By executing the programs and instructions in memory 304, the processor 301 executes the program to complete the regulation of the downstream throttle valve 104.

[0036] In this application, when the gas supply channel of the economizer is closed, the downstream throttle valve is controlled according to the high-pressure side pressure and low-pressure side pressure of the refrigeration system, which can more accurately adjust the liquid level of the economizer and avoid fluctuations in the liquid level of the economizer.

[0037] Although this disclosure has been described in conjunction with examples of the embodiments outlined above, various alternatives, modifications, variations, improvements, and / or substantially equivalents, whether known or currently or soon to be foreseen, will likely be apparent to those skilled in the art. Furthermore, the technical effects and / or technical problems described herein are exemplary and not limiting; therefore, the disclosures herein may be used to solve other technical problems and achieve other technical effects. Accordingly, the examples of embodiments of this disclosure as set forth above are intended to be illustrative and not restrictive. Various changes may be made without departing from the spirit or scope of this disclosure. Therefore, this disclosure is intended to include all known or previously developed alternatives, modifications, variations, improvements, and / or substantially equivalents.

Claims

1. A refrigeration system, characterized in that... include: A compressor (110), a condenser (101), and an evaporator (102) are connected in sequence; Economizer (103), which is disposed between the condenser (101) and the evaporator (102) and is controllably connected to the compressor (110) via a gas supply channel (139); A downstream throttle valve (104) is disposed between the economizer (103) and the evaporator (102); and A control device (150) connected to the downstream throttle valve (104) is configured to: When the gas supply channel (139) of the economizer (103) is closed, the system receives the signals of the high pressure side pressure P3 of the refrigeration system, the low pressure side pressure P4 of the refrigeration system, the pressure P1 of the economizer, and the liquid level L1 of the economizer. The target pressure P2 of the economizer is calculated based on the high-pressure side pressure P3, the low-pressure side pressure P4, and the difference between the liquid level height L1 and the target liquid level height L2 of the economizer; and The flow rate of the downstream throttle valve (104) is controlled according to the pressure P1 of the economizer and the target pressure P2 of the economizer.

2. The refrigeration system as described in claim 1, characterized in that: The target pressure P2 of the economizer = Where C1 is the first control coefficient and C2 is the second control coefficient.

3. The refrigeration system as described in claim 2, characterized in that: The control device (150) is configured to: Calculate the difference between the target pressure P2 and the pressure P1 of the economizer; and The flow rate of the downstream throttle valve (104) is adjusted according to the difference.

4. The refrigeration system as described in claim 3, characterized in that: When adjusting the flow rate of the downstream throttle valve (104), the adjustment range of the downstream throttle valve (104) is controlled by proportional-integral control.

5. The refrigeration system as described in claim 1, characterized in that: The refrigeration system includes a high-pressure side pressure sensor, a low-pressure side pressure sensor, and an economizer pressure sensor. The high-pressure side pressure sensor is located in the discharge pipe of the compressor (110) or at the condenser (101). The low-pressure side pressure sensor is located in the suction pipe of the compressor (110) or at the evaporator (102). The economizer pressure sensor is located at the economizer (103). The high-pressure side pressure P3 and the low-pressure side pressure P4 are sensed by the high-pressure side pressure sensor and the low-pressure side pressure sensor, respectively, and the pressure P1 of the economizer is sensed by the economizer pressure sensor.

6. The refrigeration system as described in claim 5, characterized in that: The economizer also includes a liquid level sensor configured to sense the liquid level height L1 of the economizer.

7. A control method for a refrigeration system, said refrigeration system comprising a compressor (110), a condenser (101), an evaporator (102), an economizer (103), and a downstream throttling valve (104), characterized in that... The method includes the following steps: Receive the signals of the high-pressure side pressure P3 of the refrigeration system, the low-pressure side pressure P4 of the refrigeration system, the pressure P1 of the economizer, and the liquid level L1 of the economizer; The calculated target pressure P2 of the economizer is calculated based on the high-pressure side pressure P3, the low-pressure side pressure P4, and the difference between the liquid level height L1 and the target liquid level height L2 of the economizer. Compare the difference between the target pressure P2 of the economizer and the pressure P1 of the economizer; and The flow rate of the downstream throttle valve (104) is adjusted according to the difference.

8. The control method as described in claim 7, characterized in that... : The target pressure P2 of the economizer = Where C1 is the first control coefficient and C2 is the second control coefficient.

9. The control method as described in claim 7, characterized in that... : When adjusting the flow rate of the downstream throttle valve (104), the adjustment range of the downstream throttle valve (104) is controlled by proportional-integral control.

10. The control method as described in claim 7, characterized in that... : The control method is executed when the gas supply channel (139) of the economizer (103) is closed.

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