A refrigeration system and control method for reducing compressor suction and discharge temperatures

Abstract

The application discloses a refrigeration system for reducing the suction and exhaust temperature of a compressor, which comprises a compressor, an oil separator, a condenser, a liquid accumulator, a filter and an evaporator connected in sequence by pipelines to form a refrigeration cycle loop; a second temperature sensor is arranged at the inlet end of the compressor, a first temperature sensor is arranged at the outlet end of the evaporator, and a third temperature sensor is arranged in the space where the evaporator is located; the refrigerant flowing out of the outlet end of the filter is divided into four paths through pipelines a, b, c and d; a is communicated with the cooling pipeline on the shell of the compressor; b is communicated with the inlet pipeline of the compressor; c and d are respectively connected with the inlet end of the evaporator, and the refrigerant flowing out of the outlet of the evaporator is connected with the inlet pipeline of the compressor through pipelines e or f. The application further discloses a control method of the refrigeration system for reducing the suction and exhaust temperature of the compressor, wherein the connection of the pipelines a, b, c, d, e and f is controlled by detecting the temperatures of the first, second and third temperature sensors, so as to reduce the suction and exhaust temperature of the compressor.

Description

Technical Field

[0001] This invention relates to the field of compressor suction and discharge temperature control, and specifically to a refrigeration system and control method for reducing compressor suction and discharge temperatures. Background Technology

[0002] In today's rapidly developing economy, air conditioning has gradually become an indispensable part of human life, greatly improving people's quality of life and work efficiency. Meanwhile, to further improve air conditioning performance, the air conditioning industry is constantly innovating technologically. As the core component of an air conditioner, the safe and efficient operation of the compressor is crucial. Excessively high compressor suction and discharge temperatures are a significant factor affecting the normal operation of an air conditioner; therefore, effective control of compressor suction and discharge temperatures is particularly critical.

[0003] For air conditioners and other small refrigeration equipment, the compressor's suction temperature is generally required to be between 5°C and 15°C, and the discharge temperature should typically not exceed 120°C. When the compressor's discharge temperature is too high, the compressor's power consumption increases, cooling efficiency decreases, and high temperatures may cause the lubricating oil to decompose, reducing its lubrication and cooling effects, accelerating compressor wear. Internal compressor materials, such as seals and insulation materials, will also age faster due to high temperatures, shortening the equipment's lifespan. Furthermore, sustained high temperatures may overload the compressor motor, increasing the risk of failure, and may even affect refrigerant circulation, leading to unstable refrigerant flow and impacting the unit's cooling performance.

[0004] There are many factors that can cause excessively high compressor suction and discharge temperatures, such as insufficient refrigerant in the evaporator, component blockage, excessively high ambient temperature, or inadequate insulation of the pipeline.

[0005] Currently, the main methods for controlling compressor suction and discharge temperatures are liquid injection cooling and hot gas bypass cooling. Liquid injection cooling involves spraying a portion of low-temperature, high-pressure liquid refrigerant into the compressor suction port. While this effectively reduces the compressor suction temperature, it's difficult to accurately control the amount of liquid refrigerant injected. Too much refrigerant can cause liquid slugging in the compressor; too little refrigerant will fail to lower the suction temperature, affecting system performance. Hot gas bypass cooling involves directly returning a portion of high-pressure hot gas to the evaporator through a bypass line to reduce the discharge temperature. While this reduces the refrigerant flow through the condenser and evaporator, it lowers the system's cooling efficiency, requiring more energy to maintain the same cooling effect and increasing the compressor load. Although these two methods can effectively reduce compressor suction and discharge temperatures and protect the compressor in certain situations, they present numerous problems, including high control difficulty and reduced cooling efficiency due to loss of system heat exchange area.

[0006] Therefore, there is an urgent need to propose a system and control strategy that can effectively and quickly reduce the intake and exhaust temperatures of the compressor. Summary of the Invention

[0007] In view of the problems and shortcomings of the existing technology, the present invention provides a refrigeration system and control method for reducing the suction and discharge temperature of the compressor.

[0008] The technical solution of this invention is as follows:

[0009] A refrigeration system for reducing the suction and discharge temperatures of a compressor includes a compressor, an oil separator, a condenser, a liquid receiver, a filter, and an evaporator, which are connected in sequence through pipelines to form a refrigeration cycle loop.

[0010] The compressor is equipped with a second temperature sensor at its inlet, the evaporator is equipped with a first temperature sensor at its outlet, and the space where the evaporator is located is equipped with a third temperature sensor for detecting the ambient temperature.

[0011] The refrigerant flowing out of the filter outlet is divided into four paths through pipes a, b, c, and d. Pipe a is connected to the cooling pipe on the compressor casing and is connected to a first capillary tube and a first solenoid valve. Pipe b is connected to the compressor inlet pipe and its outlet is located upstream of the second temperature sensor. Pipe b is connected to a second solenoid valve and a first expansion valve. Pipes c and d are respectively connected to the inlet of the evaporator. Pipe c is connected to a third solenoid valve and a second expansion valve, and pipe d is connected to a fourth solenoid valve and a second capillary tube.

[0012] The refrigerant flowing out of the evaporator outlet is connected to the compressor inlet pipe through pipe e or f. Pipe f is equipped with a fifth solenoid valve, and pipe e is equipped with an evaporation pressure regulating valve. The fifth solenoid valve and the evaporation pressure regulating valve are located upstream of the intersection of pipe b and the compressor inlet pipe.

[0013] Specifically, the first solenoid valve and the first capillary tube on pipeline a are arranged sequentially along the refrigerant flow direction. The second solenoid valve and the first expansion valve on pipeline b are arranged sequentially along the refrigerant flow direction. The third solenoid valve and the second expansion valve on pipeline c are arranged sequentially along the refrigerant flow direction. The fourth solenoid valve and the second capillary tube on pipeline d are arranged sequentially along the refrigerant flow direction.

[0014] A refrigeration control method for reducing compressor suction and discharge temperatures, applicable to the aforementioned refrigeration system for reducing compressor suction and discharge temperatures, includes the following steps:

[0015] The command temperature is compared with the design temperature. If the command temperature is equal to the design temperature, pipe d is connected, and it is determined whether the temperature of the first temperature sensor is lower than the compressor's maximum suction temperature. If it is lower, pipe f is connected. If it is not lower, pipes e and b are connected in sequence, and it is determined whether the temperature of the second temperature sensor is lower than the compressor's maximum suction temperature. If it is not lower, pipe a is connected.

[0016] If the commanded temperature is higher than the design temperature, then connect pipe c and determine whether the temperature of the first temperature sensor is lower than the compressor's maximum suction temperature: if it is lower, then connect pipe f; if it is not lower, then connect pipes e and b in sequence and determine whether the temperature of the second temperature sensor is lower than the compressor's maximum suction temperature: if it is not lower, then connect pipe a.

[0017] If the commanded temperature is lower than the design temperature, then pipe d is connected, and it is determined whether the temperature of the first temperature sensor is lower than the compressor's maximum suction temperature. If it is lower, then pipe f is connected, the refrigeration system operates, and pipe c is connected after the temperature of the third temperature sensor reaches the design temperature. If it is not lower, then pipes e and b are connected sequentially, and it is determined whether the temperature of the second temperature sensor is lower than the compressor's maximum suction temperature. If it is lower, then pipe c is connected after the temperature of the third temperature sensor reaches the design temperature. If it is not lower, then pipe a is connected, the refrigeration system operates, and pipe c is connected after the temperature of the third temperature sensor reaches the design temperature.

[0018] Specifically, the operation of connecting pipelines a, b, c, and d is achieved by closing the first solenoid valve, the second solenoid valve, the third solenoid valve, and the fourth solenoid valve, respectively.

[0019] The step of connecting pipeline f is achieved by closing the fifth solenoid valve, and the operation of connecting pipeline e is achieved by simultaneously opening the steam pressure regulating valve while disconnecting the fifth solenoid valve.

[0020] The beneficial effects of this invention are:

[0021] The refrigerant flowing from the filter outlet is divided into four paths via pipes a, b, c, and d. Pipe a connects to the cooling pipe on the compressor casing, pipe b connects to the compressor inlet pipe, and pipes c and d are connected in parallel and to the evaporator inlet. A first temperature sensor, a second temperature sensor, and a third temperature sensor are installed at the evaporator outlet, the compressor inlet, and the space containing the evaporator, respectively, to monitor the temperature of each sensor in real time. During system operation, different cooling control strategies are flexibly selected based on the readings of each temperature sensor, and the corresponding pipes are connected by controlling the opening and closing of the solenoid valves on the corresponding pipes.

[0022] The refrigerant, condensed in the condenser, is throttled and cooled by the first expansion valve via pipe b before being introduced into the compressor's inlet pipe. There, it mixes with the refrigerant exiting the evaporator to lower the compressor's suction temperature, thereby simultaneously reducing the compressor's discharge temperature. Conversely, the refrigerant, condensed in the condenser, is throttled and cooled by the first capillary tube via pipe a before being introduced into the compressor's cooling pipe to further cool the compressor, further reducing both the suction and discharge temperatures. This achieves rapid and effective control of the compressor's suction and discharge temperatures, ensuring the normal and stable operation of the refrigeration system.

[0023] In existing technologies, hot gas bypass to reduce the compressor's suction and discharge temperatures involves directly returning some of the high-temperature, high-pressure refrigerant vapor to the evaporator. This leads to an increase in refrigerant temperature and pressure within the evaporator, a decrease in the heat exchange temperature difference, and a reduction in heat exchange efficiency. To achieve the same cooling effect as this invention, it may be necessary to increase the heat exchanger area. However, in the system of this invention, the refrigerant temperature passing through the evaporator remains within the normal range under any operating condition. This ensures stable operation of the refrigeration system under both design and non-design conditions without sacrificing the heat exchanger area or maintaining cooling efficiency, thereby improving the reliability and service life of the compressor.

[0024] Furthermore, this invention does not require an additional refrigeration system when controlling the compressor's suction and discharge temperatures. Instead, it utilizes the temperature of the refrigerant itself within the system, controlling the opening and closing of valves via the evaporator outlet, compressor inlet, and the ambient temperature of the evaporator. This allows for switching between different refrigerant operating lines, thereby reducing the compressor's suction and discharge temperatures and ensuring reliable operation of the refrigeration system under various conditions. Moreover, this invention offers low system cost, simple and reliable control logic, and convenient maintenance, significantly reducing initial investment and operating costs. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the refrigeration system of the present invention;

[0026] Figure 2 for Figure 1 A flowchart of the control method for a refrigeration system;

[0027] 1. Compressor; 2. Oil separator; 3. Condenser; 4. Liquid receiver; 5. Filter; 6. Evaporator; 7. Evaporator pressure regulating valve; 81. First capillary tube; 82. Second capillary tube; 91. First solenoid valve; 92. Second solenoid valve; 93. Third solenoid valve; 94. Fourth solenoid valve; 95. Fifth solenoid valve; 101. First expansion valve; 102. Second expansion valve; 111. First temperature sensor; 112. Second temperature sensor; 113. Third temperature sensor. Detailed Implementation

[0028] Example 1

[0029] See Figure 1 As shown, a refrigeration system for reducing the suction and discharge temperatures of a compressor 1 includes a compressor 1, an oil separator 2, a condenser 3, a liquid receiver 4, a filter 5, and an evaporator 6, which are connected in sequence through pipelines to form a refrigeration cycle loop. A second temperature sensor 112 is provided at the inlet end of the compressor 1, a first temperature sensor 111 is provided at the outlet end of the evaporator 6, and a third temperature sensor 113 for detecting the ambient temperature is provided within the space where the evaporator 6 is located.

[0030] The refrigerant flowing out of the filter 5 outlet is divided into four paths through pipes a, b, c, and d. Pipe a connects to the cooling pipe on the compressor 1 casing, and is connected to a first capillary tube 81 and a first solenoid valve 91. Pipe b connects to the compressor 1 inlet pipe, and its outlet is located upstream of the second temperature sensor; pipe b is connected to a second solenoid valve 92 and a first expansion valve 101. Pipes c and d connect to the inlet of the evaporator 6, respectively; pipe c is connected to a third solenoid valve 93 and a second expansion valve 102, and pipe d is connected to a fourth solenoid valve 94 and a second capillary tube 82. Pipe b is used to throttle and cool the refrigerant after it has been condensed by the condenser 3 through the first expansion valve 101, and then introduce it into the compressor 1 inlet pipe. This mixture with the refrigerant exiting the evaporator 6 lowers the compressor 1's suction temperature, thereby simultaneously lowering the compressor 1's discharge temperature. Pipeline a is used to pass the refrigerant flowing out of the condenser 3 through the first capillary tube 81 to reduce its pressure and temperature before it is introduced into the cooling pipeline of the compressor 1, so as to cool the compressor 1 and further reduce the suction temperature and discharge temperature of the compressor 1.

[0031] The refrigerant flowing out of the outlet of the evaporator 6 is connected to the inlet pipe of the compressor 1 through pipe e or f. A fifth solenoid valve 95 is provided on pipe f, and an evaporation pressure regulating valve 7 is provided on pipe e. The fifth solenoid valve 95 and the evaporation pressure regulating valve 7 are located upstream of the intersection of pipe b and the inlet pipe of the compressor 1.

[0032] See Figure 1In this embodiment, the outlet of compressor 1 is connected to the inlet of oil separator 2, the outlet of oil separator 2 is connected to the inlet of condenser 3, the outlet of condenser 3 is connected to the inlet of liquid receiver 4, and the outlet of liquid receiver 4 is connected to the inlet of filter 5. The refrigerant flowing out of the outlet of filter 5 is divided into four paths. The first path is connected to the inlet of the first capillary tube 81 through the first solenoid valve 91, and the outlet of the first capillary tube 81 is directly connected to compressor 1. The second path is connected to the inlet of the first expansion valve 101 through the second solenoid valve 92, and the outlet of the first expansion valve 101 is connected to the inlet of compressor 1. The piping is connected as follows: the third path connects to the inlet of the second expansion valve 102 via the third solenoid valve 93, and the outlet of the second expansion valve 102 connects to the inlet pipe of the evaporator 6; the fourth path connects to the inlet of the second capillary tube 82 via the fourth solenoid valve 94, and the outlet of the second capillary tube 82 connects to the inlet of the evaporator 6. The refrigerant flowing out of the outlet of the evaporator 6 is divided into two paths: the first path connects to the inlet pipe of the compressor 1 via the fifth solenoid valve 95, and the second path connects to the inlet of the evaporator pressure regulating valve 7, and the outlet of the evaporator pressure regulating valve 7 connects to the inlet pipe of the compressor 1. The first temperature sensor 111 is installed at the outlet of the evaporator 6, the second temperature sensor 112 is installed at the inlet of the compressor 1, and the third temperature sensor 113 is installed in the storage room where the evaporator 6 is located to detect the ambient temperature.

[0033] Further, see Figure 1 The first solenoid valve 91 and the first capillary tube 81 on pipe a are arranged sequentially along the refrigerant flow direction. The second solenoid valve 92 and the first expansion valve 101 on pipe b are arranged sequentially along the refrigerant flow direction. The third solenoid valve 93 and the second expansion valve 102 on pipe c are arranged sequentially along the refrigerant flow direction. The fourth solenoid valve 94 and the second capillary tube 82 on pipe d are arranged sequentially along the refrigerant flow direction. The first expansion valve and the second expansion valve are either electromagnetic expansion valves or thermostatic expansion valves.

[0034] Example 2

[0035] See Figure 2 A refrigeration system control method for reducing the suction and discharge temperatures of compressor 1, used to control the aforementioned refrigeration system for reducing the suction and discharge temperatures of compressor 1.

[0036] The technical concept of this invention is:

[0037] (i): When the outlet temperature of the evaporator is greater than the maximum suction temperature of the compressor, the second solenoid valve 92 is closed, the pipeline b is connected, and the refrigerant flowing out of the filter 5 is throttled and depressurized by the first expansion valve 101 and then flows into the inlet pipeline of the compressor 1, where it merges with the refrigerant from the evaporator 6 to reduce the suction temperature of the compressor 1.

[0038] (ii): If the compressor's suction temperature is still very high after connecting pipe b, and the suction temperature cannot be controlled between 5℃ and 15℃, and the discharge temperature usually cannot be controlled below 120℃, then by closing the first solenoid valve, pipe a is connected, and the refrigerant liquid flowing out of filter 5 is throttled and depressurized through the first capillary tube 81 and cooled, and then directly enters the cooling pipe inside the compressor 1 casing at a fixed design flow rate to further cool the compressor and achieve the final protection against overheating of the compressor 1's suction and discharge.

[0039] (III) An evaporator pressure regulating valve and a solenoid valve are connected in parallel on the pipeline connecting the evaporator outlet and the compressor inlet. When the evaporator outlet temperature is higher than the compressor's maximum suction temperature, the fifth solenoid valve 95 is disconnected, and the evaporator pressure regulating valve 7 is opened. At this time, the pressure inside the evaporator is reduced by the evaporator pressure regulating valve 7, thereby reducing the temperature of the refrigerant entering the compressor 1. Combined with the connection status of pipelines b and a, this reduces the compressor's suction and discharge temperatures to meet the compressor's rated operating temperature requirements.

[0040] The control method of the present invention includes the following steps:

[0041] The commanded temperature is compared with the design temperature. If the commanded temperature equals the design temperature, pipe d is connected to allow refrigerant to flow into the evaporator. It is then determined whether the temperature of the first temperature sensor 111 is lower than the highest suction temperature of compressor 1.

[0042] If the temperature of the first temperature sensor 111 is lower than the highest suction temperature of the compressor 1, then the pipe f is connected to execute the refrigeration cycle;

[0043] If the temperature of the first temperature sensor 111 is not lower than the highest suction temperature of the compressor 1, then pipes e and b are sequentially connected to execute the refrigeration cycle. At the same time, the refrigerant flowing from the evaporator into the compressor inlet pipe is cooled through pipe b, and it is determined whether the temperature of the second temperature sensor 112 is lower than the highest suction temperature of the compressor 1.

[0044] If the temperature of the second temperature sensor 112 is not lower than the maximum suction temperature of the compressor 1, then pipe a is connected to cool the compressor through pipe a, thereby reducing the suction and discharge temperatures of the compressor and ensuring its normal operation; if the temperature of the second temperature sensor 112 is lower than the maximum suction temperature of the compressor 1, then pipe a is disconnected.

[0045] The command temperature refers to the temperature that the system needs to reach, as specified by the user, while the design temperature refers to the design temperature of the refrigeration system.

[0046] Specifically, connecting pipelines a, b, c, and d is achieved by closing the first solenoid valve 91, the second solenoid valve 92, the third solenoid valve 93, and the fourth solenoid valve 94, respectively. Connecting pipeline f is achieved by closing the fifth solenoid valve 95, and connecting pipeline e is achieved by simultaneously opening the steam pressure regulating valve while disconnecting the fifth solenoid valve 95.

[0047] In this embodiment, the following three operating conditions are included when the commanded temperature equals the design temperature:

[0048] In operating condition 1, when the commanded temperature is the system design temperature, pipe d is opened, and pipes a, b, and c are closed. High-temperature and high-pressure refrigerant flows out from compressor 1, passes through oil separator 2, and the refrigerant with separated lubricating oil is introduced into condenser 3 for exothermic condensation. The condensed refrigerant enters receiver 4, and then enters filter 5 to remove impurities. The refrigerant flowing out from filter 5 passes through fourth solenoid valve 94 and second capillary tube 82, and is introduced into evaporator 6 at a fixed design flow rate so that evaporator 6 reaches the system design temperature.

[0049] When the temperature indicated by the first temperature sensor 111 at the outlet of the evaporator 6 is lower than the highest suction temperature of the compressor 1, the fifth solenoid valve 95 is opened, the evaporation pressure regulating valve 7 is closed, and the pipeline f is connected. The refrigerant that meets the suction and discharge temperature requirements of the compressor 1 is introduced into the compressor 1 and continues to complete the refrigeration cycle, so that the system can work at the commanded temperature.

[0050] In operating condition 2, when the commanded temperature is the system design temperature, pipe d is opened, and pipes a, b, and c are closed. High-temperature and high-pressure refrigerant flows out from compressor 1, passes through oil separator 2, and the refrigerant with separated lubricating oil is introduced into condenser 3 for exothermic condensation. The condensed refrigerant enters receiver 4, and then enters filter 5 to remove impurities. The refrigerant flowing out from filter 5 passes through fourth solenoid valve 94, through second capillary tube 82, and is introduced into evaporator 6 at a fixed design flow rate so that evaporator 6 reaches the system design temperature.

[0051] When the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 is not lower than the highest suction temperature of compressor 1, the evaporation pressure regulating valve 7 is opened, the fifth solenoid valve 95 is closed, and pipeline e is connected. The pressure inside evaporator 6 is reduced through the evaporation pressure regulating valve 7, thereby reducing the temperature of the refrigerant entering compressor 1. Subsequently, pipeline b is opened, and the refrigerant flowing from filter 5 passes through the second solenoid valve 92, and then through the first expansion valve 101 for throttling, pressure reduction, and temperature reduction. The opening degree of the first expansion valve 101 is adjusted by the difference between the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 and the highest suction temperature of compressor 1. Subsequently, the refrigerant in the inlet pipeline of compressor 1 merges with the refrigerant from evaporator 6 to reduce the suction temperature of compressor 1, while preventing liquid from entering the compressor and causing liquid slugging.

[0052] When the temperature indicated by the second temperature sensor 112 located at the inlet of compressor 1 is lower than the highest suction temperature of compressor 1, refrigerant that meets the suction and discharge temperature requirements of compressor 1 is introduced into compressor 1 and continues to complete the refrigeration cycle, so that the system can operate at the commanded temperature.

[0053] In operating condition 3, when the commanded temperature is the system design temperature, pipe d is opened, and pipes a, b, and c are closed. High-temperature and high-pressure refrigerant flows out from compressor 1, passes through oil separator 2, and the refrigerant with separated lubricating oil is introduced into condenser 3 for heat release and condensation. The condensed refrigerant enters receiver 4, and then enters filter 5 to remove impurities. The refrigerant flowing out from filter 5 passes through fourth solenoid valve 94 and second capillary tube 82, and is introduced into evaporator 6 at a fixed design flow rate so that evaporator 6 reaches the system design temperature.

[0054] When the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 is not lower than the highest suction temperature of compressor 1, the evaporation pressure regulating valve 7 is opened, the fifth solenoid valve 95 is closed, and pipeline e is connected. The pressure inside evaporator 6 is reduced by the evaporation pressure regulating valve 7, thereby reducing the temperature of the refrigerant entering compressor 1. Subsequently, pipeline b is opened, and the refrigerant flowing from filter 5 passes through the second solenoid valve 92 and is throttled and depressurized by the first expansion valve 101. The opening degree of the first expansion valve 101 is adjusted by the difference between the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 and the highest suction temperature of compressor 1. Subsequently, the refrigerant in the inlet pipeline of compressor 1 merges with the refrigerant from evaporator 6 to reduce the suction temperature of compressor 1, while preventing liquid from entering the compressor and causing liquid slugging.

[0055] If the temperature indicated by the second temperature sensor 112 at the inlet of compressor 1 is not lower than the highest suction temperature of compressor 1, pipeline a is opened. The refrigerant flowing out from filter 5 passes through the first solenoid valve 91 and the first capillary tube 81, which throttles and reduces pressure and temperature. It is then directly introduced into the cooling pipeline inside the casing of compressor 1 at a fixed design flow rate, thus achieving the final protection against overheating of compressor 1's suction and discharge, and enabling the system to operate at the commanded temperature or shut down.

[0056] If the commanded temperature is higher than the design temperature, then pipe c is connected to allow refrigerant to enter the evaporator. Simultaneously, the flow rate of refrigerant entering the evaporator is controlled by the second expansion valve 102, and it is determined whether the temperature of the first temperature sensor 111 is lower than the maximum suction temperature of the compressor 1.

[0057] If the temperature of the first temperature sensor 111 is lower than the highest suction temperature of the compressor 1, then the pipe f is connected to execute the refrigeration cycle;

[0058] If the temperature of the first temperature sensor 111 is not lower than the highest suction temperature of the compressor 1, then pipe e and pipe b are sequentially connected to execute the refrigeration cycle. At the same time, the refrigerant flowing from the evaporator into the compressor inlet pipe is cooled through pipe b, and it is determined whether the temperature of the second temperature sensor 112 is lower than the highest suction temperature of the compressor 1.

[0059] If the temperature of the second temperature sensor 112 is not lower than the maximum suction temperature of the compressor 1, then pipe a is connected to cool the compressor through pipe a, thereby reducing the suction and discharge temperatures of the compressor and ensuring its normal operation; if the temperature of the second temperature sensor 112 is lower than the maximum suction temperature of the compressor 1, then pipe a is disconnected.

[0060] In this embodiment, when the commanded temperature is higher than the design temperature, the following three operating conditions are included:

[0061] In operating condition four, when the commanded temperature is higher than the system design temperature, passage c is opened and passages a, b, and d are closed. The refrigerant flowing out of filter 5 passes through the third solenoid valve 93 and then through the second expansion valve 102 for throttling, pressure reduction, and temperature reduction. The opening of the second expansion valve 102 is adjusted according to the refrigerant superheat at the outlet of evaporator 6 to meet the refrigeration requirements of evaporator 6.

[0062] When the temperature indicated by the first temperature sensor 111 at the outlet of the evaporator 6 is lower than the highest suction temperature of the compressor 1, the fifth solenoid valve 95 is opened, the evaporation pressure regulating valve 7 is closed, and the pipeline f is connected. The refrigerant that meets the suction and discharge temperature requirements of the compressor 1 is introduced into the compressor 1 and continues to complete the cycle, so that the system can work at the commanded temperature.

[0063] In operating condition 5, when the commanded temperature is higher than the system design temperature, passage c is opened and passages a, b, and d are closed. The refrigerant flowing out of filter 5 passes through the third solenoid valve 93 and then through the second expansion valve 102 for throttling, pressure reduction, and temperature reduction. The opening of the second expansion valve 102 is adjusted according to the refrigerant superheat at the outlet of evaporator 6 to meet the refrigeration requirements of evaporator 6.

[0064] When the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 is not lower than the highest suction temperature of compressor 1, the evaporation pressure regulating valve 7 is opened, the fifth solenoid valve 95 is closed, and pipeline e is connected. The pressure inside the evaporator is reduced by the evaporation pressure regulating valve 7, thereby reducing the temperature of the refrigerant entering compressor 1. Subsequently, passage b is opened, and the refrigerant flowing out of filter 5 passes through the second solenoid valve 92, and is throttled and depressurized by the first expansion valve 101. The opening degree of the first expansion valve 101 is adjusted by the difference between the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 and the highest suction temperature of compressor 1. Subsequently, the refrigerant in the inlet pipeline of compressor 1 merges with the refrigerant from evaporator 6 to reduce the suction temperature of compressor 1, while preventing liquid from entering the compressor and causing liquid slugging.

[0065] When the temperature indicated by the second temperature sensor 112 located at the inlet of compressor 1 is lower than the highest suction temperature of compressor 1, refrigerant that meets the suction and discharge temperature requirements of compressor 1 is introduced into compressor 1 and continues to complete the cycle, so that the system can operate at the commanded temperature.

[0066] In operating condition six, when the commanded temperature is higher than the system design temperature, passage c opens, while passages a, b, and d close. The refrigerant flowing from filter 5 passes through the third solenoid valve 93, and then through the second expansion valve 102 for throttling, pressure reduction, and temperature reduction. The opening of the second expansion valve 102 is adjusted according to the refrigerant superheat at the outlet of evaporator 6 to meet the refrigeration requirements of evaporator 6.

[0067] When the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 is not lower than the highest suction temperature of compressor 1, the evaporation pressure regulating valve 7 is opened, the fifth solenoid valve 95 is closed, and pipeline e is connected. The pressure inside the evaporator is reduced by the evaporation pressure regulating valve 7, thereby reducing the temperature of the refrigerant entering compressor 1. Subsequently, passage b is opened, and the refrigerant flowing out of filter 5 passes through the second solenoid valve 92, and is throttled and depressurized by the first expansion valve 101. The opening degree of the first expansion valve 101 is adjusted by the difference between the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 and the highest suction temperature of compressor 1. Subsequently, the refrigerant in the inlet pipeline of compressor 1 merges with the refrigerant from evaporator 6 to reduce the suction temperature of compressor 1, while preventing liquid from entering the compressor and causing liquid slugging.

[0068] If the temperature shown by the second temperature sensor 112 at the inlet of compressor 1 is not lower than the highest suction temperature of compressor 1, passage a is opened. The refrigerant flowing out from filter 5 passes through the first solenoid valve 91 and the first capillary tube 81, which throttles and reduces pressure and temperature. It is then directly introduced into the casing of compressor 1 at a fixed design flow rate, thus achieving the final protection against overheating of compressor 1's suction and discharge, and enabling the system to operate at the commanded temperature or shut down.

[0069] If the commanded temperature is lower than the design temperature, then pipe d is connected, and it is determined whether the temperature of the first temperature sensor 111 is lower than the maximum suction temperature of compressor 1:

[0070] If the temperature of the first temperature sensor 111 is lower than the maximum suction temperature of the compressor 1, then the pipe f is connected to allow the refrigeration system to run for a period of time to reach the design temperature. At the same time, the ambient temperature is detected by the third temperature sensor. Then, after the temperature of the third temperature sensor 113 reaches the design temperature, the pipe c is connected and the refrigerant entering the evaporator is controlled by the second expansion valve 102 in the pipe c to make the ambient temperature reach the command temperature.

[0071] If the temperature of the first temperature sensor 111 is not lower than the highest suction temperature of the compressor 1, then pipes e and b are connected sequentially. The function of connecting pipe b is to reduce the pressure and temperature of the refrigerant through the first expansion valve 101 before it flows into the compressor inlet pipe, thereby lowering the compressor suction temperature, and to determine whether the temperature of the second sensor is lower than the highest suction temperature of the compressor 1.

[0072] If the temperature of the second sensor is lower than the maximum suction temperature of the compressor 1, the temperature of the third temperature sensor is detected, and after the temperature of the third temperature sensor 113 reaches the design temperature, the pipe c is connected, and the refrigerant flow is controlled through the pipe c to cool the system until the cooling temperature of the system reaches the command temperature.

[0073] If the temperature of the second sensor is not lower than the maximum suction temperature of compressor 1, then pipe a is connected to cool the compressor to further reduce the suction and discharge temperatures of the compressor. The ambient temperature is detected by the third temperature sensor. Then, after the temperature of the third temperature sensor 113 reaches the design temperature, pipe c is connected. The ambient temperature is brought to the command temperature by connecting pipe c and controlling the flow.

[0074] In this embodiment, the following three operating conditions apply when the commanded temperature is lower than the design temperature:

[0075] Condition 7: When the commanded temperature is lower than the system design temperature, passage d is opened and passages a, b, and c are closed. The refrigerant flowing out of filter 5 passes through the fourth solenoid valve 94 and the second capillary tube 82, and is introduced into evaporator 6 at a fixed design flow rate so that evaporator 6 reaches the system design temperature.

[0076] When the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 is lower than the highest suction temperature of compressor 1, the fifth solenoid valve 95 is opened, the evaporator pressure regulating valve 7 is closed, and pipeline f is connected to allow the refrigeration system to operate normally. The ambient temperature is detected by the third temperature sensor 113. When the ambient temperature equals the design temperature, passage c is opened. The refrigerant flowing from filter 5 passes through the third solenoid valve 93, then through the second expansion valve 102 for throttling, pressure reduction, and temperature reduction before entering evaporator 6. Simultaneously, the opening of the second expansion valve 102 is adjusted according to the refrigerant superheat at the outlet of evaporator 6 to meet the refrigeration requirements of evaporator 6. Afterwards, the refrigerant from the evaporator that meets the suction and discharge temperature requirements of compressor 1 flows into compressor 1 to complete the refrigeration cycle. The system's refrigeration temperature reaches the commanded temperature through the connection of pipeline c and flow control.

[0077] In operating condition 8, when the commanded temperature is lower than the system design temperature, the d-passage is opened and the a, b, and c-passages are closed. The refrigerant flowing out of the filter 5 passes through the fourth solenoid valve 94 and the second capillary tube 82, and is introduced into the evaporator 6 at a fixed design flow rate so that the evaporator 6 reaches the system design temperature.

[0078] When the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 is not lower than the highest suction temperature of compressor 1, the evaporation pressure regulating valve 7 is opened, the fifth solenoid valve 95 is closed, and pipeline e is connected. The pressure inside the evaporator is reduced by the evaporation pressure regulating valve 7, thereby reducing the temperature of the refrigerant entering compressor 1. Subsequently, passage b is opened, and the refrigerant flowing out of filter 5 passes through the second solenoid valve 92, and then through the first expansion valve 101 for throttling, pressure reduction, and temperature reduction. The opening degree of the first expansion valve 101 is adjusted by the difference between the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 and the highest suction temperature of compressor 1. Subsequently, the refrigerant in the inlet pipeline of compressor 1 merges with the refrigerant from evaporator 6 to reduce the suction temperature of compressor 1, while preventing liquid from entering the compressor and causing liquid slugging.

[0079] When the temperature indicated by the second temperature sensor 112 at the inlet of compressor 1 is lower than the maximum suction temperature of compressor 1, the compressor is at its normal suction and discharge operating temperature. At this time, the ambient temperature is detected by the third temperature sensor 113 according to the command temperature control system. When the ambient temperature equals the design temperature, the c-pass opens. The refrigerant flowing from filter 5 passes through the third solenoid valve 93, then through the second expansion valve 102 for throttling, pressure reduction, and temperature reduction before flowing into evaporator 6. Simultaneously, the opening of the second expansion valve 102 is adjusted according to the refrigerant superheat at the outlet of evaporator 6 to meet the refrigeration requirements of evaporator 6. Afterward, the refrigerant flowing from evaporator 6 that meets the suction and discharge temperature requirements of compressor 1 is introduced into compressor 1 to continue the refrigeration cycle, allowing the ambient temperature to reach the command temperature for operation.

[0080] In operating condition nine, when the commanded temperature is lower than the system design temperature, the d-passage is opened and the a, b, and c-passages are closed. The refrigerant flowing out of the filter 5 passes through the fourth solenoid valve 94 and the second capillary tube 82, and is introduced into the evaporator 6 at a fixed design flow rate so that the evaporator 6 reaches the system design temperature.

[0081] When the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 is not lower than the highest suction temperature of compressor 1, the evaporation pressure regulating valve 7 is opened, the fifth solenoid valve 95 is closed, and pipeline e is connected. The pressure inside the evaporator is reduced by the evaporation pressure regulating valve 7, thereby reducing the temperature of the refrigerant entering compressor 1. Subsequently, passage b is opened. The refrigerant flowing out of filter 5 passes through the second solenoid valve 92 and then is throttled and depressurized by the first expansion valve 101. The opening of the first expansion valve 101 is adjusted by the difference between the temperature indicated by the first temperature sensor 111 at the outlet of evaporator 6 and the highest suction temperature of compressor 1. Afterward, the refrigerant in the inlet pipeline of compressor 1 merges with the refrigerant from evaporator 6 to reduce the suction temperature of compressor 1. At the same time, it can prevent liquid from entering the compressor, which could cause liquid slugging.

[0082] When the temperature indicated by the second temperature sensor 112 at the inlet of compressor 1 is not lower than the highest suction temperature of compressor 1, passage a opens. The refrigerant flowing from filter 5 passes through the first solenoid valve 91, then through the first capillary tube 81 for throttling, pressure reduction, and temperature reduction. It is then directly introduced into the cooling pipes inside the compressor 1 casing at a fixed design flow rate to lower the compressor's suction and discharge temperatures, achieving final protection against overheating of compressor 1. If the suction temperature of compressor 1 is lower than its maximum suction temperature, the system continues to operate for a period of time, and the ambient temperature is detected by the third temperature sensor 113. When the ambient temperature equals the design temperature, passage c opens. The refrigerant flowing from filter 5 passes through the third solenoid valve 93, then through the second expansion valve 102 for throttling, pressure reduction, and temperature reduction before flowing into evaporator 6. The opening of the second expansion valve 102 is adjusted according to the refrigerant superheat at the outlet of evaporator 6 to meet the refrigeration requirements of evaporator 6. Afterwards, the refrigerant flowing from the evaporator, meeting the suction and discharge temperature requirements of compressor 1, is introduced into compressor 1 to continue the refrigeration cycle, bringing the ambient temperature to the commanded temperature.

Claims

1. A refrigeration control method for reducing the suction and discharge temperatures of a refrigeration system, the refrigeration system comprising a compressor (1), an oil separator (2), a condenser (3), a liquid receiver (4), a filter (5), and an evaporator (6) connected sequentially by pipelines to form a refrigeration cycle loop, characterized in that, The compressor (1) is provided with a second temperature sensor (112) at the inlet end, the evaporator (6) is provided with a first temperature sensor (111) at the outlet end, and a third temperature sensor (113) for detecting ambient temperature is provided in the space where the evaporator (6) is located. The refrigerant flowing out of the filter (5) outlet is divided into four paths through pipes a, b, c, and d; among them, a is connected to the cooling pipe on the compressor (1) casing, and is connected to the first capillary tube (81) and the first solenoid valve (91); b is connected to the compressor (1) inlet pipe, and its outlet is located upstream of the second temperature sensor, and is connected to the second solenoid valve (92) and the first expansion valve (101); c and d are respectively connected to the inlet of the evaporator (6), and are connected to the third solenoid valve (93) and the second expansion valve (102) on c, and are connected to the fourth solenoid valve (94) and the second capillary tube (82) on d. The refrigerant flowing out of the evaporator (6) outlet is connected to the inlet pipe of the compressor (1) through pipe e or f. A fifth solenoid valve (95) is provided on pipe f, and an evaporation pressure regulating valve (7) is provided on pipe e. The fifth solenoid valve (95) and the evaporation pressure regulating valve (7) are located upstream of the intersection of pipe b and the inlet pipe of the compressor (1). Includes the following steps: Determine whether the command temperature is equal to the design temperature. If the command temperature is equal to the design temperature, then connect pipe d and determine whether the temperature of the first temperature sensor (111) is lower than the maximum suction temperature of the compressor (1). If it is lower, then connect pipe f. If it is not lower, then connect pipes e and b in sequence and determine whether the temperature of the second temperature sensor (112) is lower than the maximum suction temperature of the compressor (1). If it is not lower, then connect pipe a. If the command temperature is higher than the design temperature, then pipe c is connected, and it is determined whether the temperature of the first temperature sensor (111) is lower than the maximum suction temperature of the compressor (1): if it is lower, then pipe f is connected; if it is not lower, then pipes e and b are connected in sequence, and it is determined whether the temperature of the second temperature sensor (112) is lower than the maximum suction temperature of the compressor (1): if it is not lower, then pipe a is connected. If the command temperature is lower than the design temperature, then pipe d is connected, and it is determined whether the temperature of the first temperature sensor (111) is lower than the maximum suction temperature of the compressor (1): if it is lower, then pipe f is connected, and then pipe c is connected after the temperature of the third temperature sensor (113) reaches the design temperature; if it is not lower, then pipes e and b are connected in sequence, and it is determined whether the temperature of the second temperature sensor (112) is lower than the maximum suction temperature of the compressor (1): if it is lower, then pipe c is connected after the temperature of the third temperature sensor (113) reaches the design temperature; if it is not lower, then pipe a is connected, and then pipe c is connected after the temperature of the third temperature sensor (113) reaches the design temperature.

2. The refrigeration control method according to claim 1, characterized in that, The first solenoid valve (91) and the first capillary tube (81) on the a pipeline are arranged sequentially along the refrigerant flow direction.

3. The refrigeration control method according to claim 1, characterized in that, The second solenoid valve (92) and the first expansion valve (101) on the b pipeline are arranged sequentially along the refrigerant flow direction.

4. The refrigeration control method according to claim 1, characterized in that, The third solenoid valve (93) and the second expansion valve (102) on the c-pipe are arranged sequentially along the refrigerant flow direction.

5. The refrigeration control method according to claim 1, characterized in that, The fourth solenoid valve (94) and the second capillary tube (82) on the d pipeline are arranged sequentially along the refrigerant flow direction.

6. The refrigeration control method according to claim 1, characterized in that, The operation of connecting pipelines a, b, c, and d is achieved by opening the first solenoid valve (91), the second solenoid valve (92), the third solenoid valve (93), and the fourth solenoid valve (94) respectively.

7. The refrigeration control method according to claim 1 or 6, characterized in that, The step of connecting pipeline f is achieved by opening the fifth solenoid valve (95), and the step of connecting pipeline e is achieved by closing the fifth solenoid valve (95) while opening the evaporation pressure regulating valve.

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