Control method of regenerative refrigeration system

Abstract

The invention relates to a control method of a regenerative refrigerating system, the refrigerating system comprises a compressor, a condenser, a gas-liquid separation device, an expansion valve and an evaporator, the gas-liquid separation device comprises a first heat exchange pipe with a gas inlet end and a gas outlet end, and a second heat exchange pipe capable of enabling a medium in the first heat exchange pipe to exchange heat with a medium in the first heat exchange pipe and provided with a liquid inlet end and a liquid outlet end; the air inlet end and the air outlet end are connected with the output end of the evaporator and the input end of the compressor respectively, and the liquid inlet end and the liquid outlet end are connected with the output end of the condenser and the input end of the expansion valve respectively. The refrigerating system further comprises a main control unit, a first sensor, a second sensor, a third sensor, a fourth sensor and a fifth sensor, wherein the first sensor and the second sensor are used for monitoring medium temperatures of a liquid inlet end and a liquid outlet end; the third sensor and the fourth sensor are used for monitoring medium temperatures of an air inlet end and an air outlet end; by controlling the superheat degree of the system, the heat exchange efficiency and the refrigeration effect of the system are ensured, overheating and supercooling of the system are stabilized, the situation that the compressor sucks air and carries liquid is avoided, and the reliability of the system is improved.

Description

Technical Field

[0001] The invention relates to a control method for a heat recovery refrigeration system, and is applicable to the technical field of refrigeration systems. Background Art

[0002] The refrigeration system is usually composed of four major parts: compressor, condenser, expansion valve, evaporator and refrigerant. The refrigerant is circulated in the system and changes state to achieve heat exchange with the outside world. The refrigerant in the refrigeration system will become a high-pressure liquid after passing through the condenser, and then the refrigerant will be adjusted through the expansion valve to form a low-temperature and low-pressure liquid and then input into the evaporator, so that the refrigerant absorbs heat and vaporizes in the evaporator, and then returns to the compressor after becoming high-temperature steam. However, in actual use of the refrigeration system, the compressor often has problems such as harmful overheating of the suction air or liquid in the suction air. In the prior art, the pressure and temperature of the refrigerant are usually adjusted to a suitable state by controlling the expansion valve so that the refrigerant can fully evaporate in the evaporator. A heat exchange device is also added to the refrigeration system to exchange heat between the low-temperature liquid output by the condenser and the high-temperature gas output by the evaporator, and the state of the steam output by the evaporator is controlled to solve the problem of liquid in the suction air or overheating. However, the above method will reduce the refrigeration effect and sacrifice the refrigeration capacity of the refrigeration system on the one hand; on the other hand, it is difficult to accurately control the expansion valve with the existing control method, and the error is large. It is difficult to accurately adjust the refrigerant to a suitable state, and it is impossible to effectively avoid the problem of liquid in the suction air or overheating. Summary of the invention

[0003] In order to solve the defects of the above-mentioned prior art, the present invention proposes a control method for a heat recovery refrigeration system. The technical solution adopted by the present invention is: a control method for a heat recovery refrigeration system, the refrigeration system includes a compressor, a condenser whose input end is connected to the output end of the compressor, a gas-liquid separation device connected to the output end of the condenser, an expansion valve whose input end is connected to the gas-liquid separation device, and an evaporator whose input end is connected to the output end of the expansion valve. The gas-liquid separation device includes a first heat exchange tube with an air inlet end and an air outlet end, and a second heat exchange tube capable of heat exchange between the medium therein and the medium in the first heat exchange tube and having a liquid inlet end and a liquid outlet end. The air inlet end and the air outlet end are respectively connected to the output end of the evaporator and the input end of the compressor, and the liquid inlet end and the liquid outlet end are respectively connected to the output end of the condenser and the input end of the expansion valve. The refrigeration system also includes a main control unit for controlling the operation of the system, a first sensor and a second sensor for monitoring the medium temperature at the liquid inlet end and the liquid outlet end, respectively, a third sensor and a fourth sensor for monitoring the medium temperature at the air inlet end and the air outlet end, respectively, and a fifth sensor for monitoring the SST saturation temperature inside the first heat exchange tube.

[0004] Control methods include: S1. Set control parameters in the main control unit, the main control unit starts the refrigeration system, and monitors the operating parameters of the refrigeration system in real time; the control parameters include the first superheat stability value M, the superheat stability time T, and the second superheat stability value M'; the operating parameters include the medium temperature T1 at the liquid inlet end collected by the first sensor, the medium temperature T2 at the liquid outlet end collected by the second sensor, the medium temperature T3 at the air inlet end collected by the third sensor, the medium temperature T4 at the air outlet end collected by the fourth sensor, and the SST saturation temperature T5 collected by the fifth sensor; S2, the main control unit controls the refrigeration system to enter the first operation mode; the first operation mode includes the main control unit calculating the first operation mode superheat actual value SH1=T3-T5 and the first operation mode superheat target value SH1'=10-(T1-T2+T3-T4) according to the operation parameters, and comparing SH1 with SH1'. If SH1>SH1', the main control unit opens the expansion valve; if SH1<SH1', the main control unit closes the expansion valve; the specific first operation mode is usually used to deal with the unstable stage when the refrigeration system is just started, which can quickly increase the return oil temperature, increase the superheat, make the refrigeration system quickly warm up, and improve the heat exchange efficiency; S3, the main control unit calculates the superheat difference m=|SH1- SH1'| of the first operation mode, and compares m with M. When m≤M, the main control unit records the actual stabilization time t, and compares t with T. If t<T, repeat the current step, otherwise execute step S4; when m>M, return to step S2; when the refrigeration system runs smoothly for a period of time, switch the operation mode to avoid excessive load on the refrigeration system and affect the normal operation of the system; S4, the main control unit controls the refrigeration system to enter the second operation mode; the second operation mode includes the main control unit calculating the second operation mode superheat actual value SH2=T4-T5 and the second operation mode superheat target value SH2'=3+(T1-T2+T3-T4)÷2 according to the operation parameters, and comparing SH2 with SH2'. If SH2>SH2', the main control unit opens the expansion valve; if SH1<SH1', the main control unit closes the expansion valve; specifically, the second operation mode is usually applied to the stage of stable operation of the refrigeration system, controls the system superheat, ensures the heat exchange performance of the evaporator, and ensures the smooth operation of the system; S5. The main control module calculates the superheat difference m'=|SH2- SH2'| of the second operation mode, and compares m' with M'. If m'≤M', the module returns to step S4; otherwise, the module returns to step S2.

[0005] By monitoring and calculating the temperature difference between the liquid inlet and outlet ends, the temperature difference between the gas inlet and outlet ends, and the SST saturation temperature in the separation device, the opening of the expansion valve can be controlled, and then the system superheat can be controlled, so that the refrigeration system can automatically adjust the state of the refrigerant according to actual usage, so as to ensure the system heat exchange efficiency and refrigeration effect while stabilizing the system overheating and overcooling, avoiding the problem of liquid inhalation by the compressor, and improving the system reliability.

[0006] Furthermore, the control parameter also includes a first superheat range threshold value N1-N2, and step S3 also includes: The main control unit compares the superheat difference m with the first superheat range threshold value. If N1≤m≤N2, the current step is continued. Otherwise, the main control unit controls the refrigeration system to shut down. The control parameters also include a second superheat range threshold value N1'-N2', and step S5 also includes: The main control unit compares the superheat difference m' with the second superheat range threshold. If N1'≤m'≤N2', the current step is continued, otherwise the main control unit controls the refrigeration system to shut down. By setting the superheat range thresholds in the first operation mode and the second operation mode, when the superheat of the refrigeration system is abnormally high or low due to factors such as equipment failure, the refrigeration system can be shut down in time to prevent system damage.

[0007] Furthermore, the refrigeration system further includes a sixth sensor disposed in the first heat exchange tube and used for monitoring the oil temperature; In step S1, the control parameters also include a low oil temperature threshold L1 and a high oil temperature threshold L2, and the operating parameters also include the oil temperature T6 collected by the sixth sensor; The method between step S2 and step S3 also includes: step S2.1, the main control unit calculates the first oil temperature difference l= T6- T5, and compares the first oil temperature difference with the oil temperature threshold value. If l≤L1, step S3 is executed; if l≥L2, step S4 is executed; Between step S4 and step S5, there is also the following: step S4.1, the main control unit calculates the second oil temperature difference l'= T6- T5, and compares the second oil temperature difference with the oil temperature threshold, if l'≤L1, then execute step S2; if l'≥L2, then execute step S5. By monitoring the returned oil temperature to switch the operation mode of the refrigeration system, the system oil temperature is ensured to be stable, and the problems of poor system operation, easy damage to equipment, and reduced refrigeration effect caused by excessively high or low oil temperature are avoided, thereby ensuring the operation stability and refrigeration effect of the refrigeration system.

[0008] Furthermore, the second heat exchange tube is spirally shaped and coiled inside the first heat exchange tube, and the liquid inlet and liquid outlet are respectively passed through the outside of the first heat exchange tube. The spirally coiled second heat exchange tube extends the flow time of the liquid refrigerant therein in the first heat exchange tube, thereby improving the heat exchange effect between the gaseous refrigerant in the first heat exchange tube and the liquid refrigerant in the second heat exchange tube, making it easier to fully vaporize the refrigerant output by the evaporator and avoid liquid inhalation by the compressor. It is also easier to adjust the system superheat, improve the system cooling capacity, and ensure the heat exchange effect.

[0009] Furthermore, a plurality of heat exchange fins are arranged on the outer wall of the second heat exchange tube, and there is a channel for gas to flow between each two adjacent heat exchange fins. The heat exchange fins are used to improve the effect and rate of heat transfer between the medium inside the second heat exchange tube and the medium inside the first heat exchange tube, thereby improving the heat exchange effect.

[0010] Furthermore, the gas-liquid separation device also includes a first cylinder disposed in the first heat exchange tube, a second cylinder sleeved on the periphery of the first cylinder, an airflow channel connected to the air inlet end is formed between the outer wall of the first cylinder and the inner wall of the second cylinder, and the second heat exchange tube is coiled in the airflow channel. The first cylinder and the second cylinder separate the internal space of the first heat exchange tube into a section of annular columnar airflow channel, and the second heat exchange tube is coiled in the spiral channel, so that the gaseous refrigerant discharged from the evaporator will be restricted in the airflow channel and flow along the airflow channel after passing into the first heat exchange tube from the air inlet end, and will fully contact with the second heat exchange tube during the flow process, thereby achieving the purpose of fully performing heat exchange and improving heat exchange efficiency.

[0011] Optionally, the gas-liquid separation device also includes a U-shaped vent pipe disposed in the first heat exchange tube, an oil suction hole opened at the bottom of the vent pipe, one end of the vent pipe is connected to the gas outlet end, the other end of the vent pipe extends into the inner cavity of the first heat exchange tube and is located outside the second heat exchange tube, and the bottom of the vent pipe extends to the bottom of the first heat exchange tube. On the one hand, the gas in the first heat exchange tube is discharged through the U-shaped vent pipe, and at the same time, the lubricating oil separated at the bottom of the first heat exchange tube is sucked into the vent pipe from the oil suction hole according to the Bernoulli principle, and the lubricating oil is returned to the compressor along with the gas refrigerant, so as to limit the amount of oil in the return gas by controlling the size of the oil suction hole, and avoid a large amount of oil in the return gas, which affects the normal operation of the refrigeration system; on the other hand, the U-shaped vent pipe is used to extend the time and distance of the refrigerant flowing in the first heat exchange tube, so as to facilitate the full vaporization of the refrigerant during the flow process, which not only improves the heat exchange efficiency, but also further reduces the phenomenon of liquid in the refrigerant flowing back to the compressor.

[0012] Optionally, an oil return port connected to the compressor is provided at the bottom of the first heat exchange tube. The lubricating oil separated from the refrigerant is recovered through the oil return port and then returned to the compressor, thereby avoiding the problem of liquid in the return air of the compressor and facilitating sewage discharge through the oil return port.

[0013] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The control method of the heat recovery refrigeration system of the present invention monitors and calculates the temperature difference between the liquid inlet and the liquid outlet in the gas-liquid separation device, the temperature difference between the gas inlet and the gas outlet, and the SST saturation temperature in the separation device, so as to control the opening of the expansion valve and then control the system superheat, so that the refrigeration system can automatically adjust the state of the refrigerant according to actual usage conditions, so as to ensure the system heat exchange efficiency and refrigeration effect while stabilizing the system overheating and overcooling, avoiding the problem of liquid inhalation by the compressor, and improving the system reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings: Figure 1 is a system architecture diagram of Example 1 of the present invention; Figure 2 yes Figure 1 A schematic structural diagram of a gas-liquid separation device in the illustrated embodiment; Figure 3 yes Figure 1 A schematic diagram of the internal structure of the first heat exchange tube in the gas-liquid separation device of the illustrated embodiment; Figure 4 is a schematic structural diagram of a gas-liquid separation device in Example 2 of the present invention; The reference numerals are described as follows: 1. Compressor; 2. Condenser; 3. Gas-liquid separation device; 31. First heat exchange tube; 311. Air inlet end; 312. Air outlet end; 32. Second heat exchange tube; 321. Liquid inlet end; 322. Liquid outlet end; 33. First cylinder; 34. Second cylinder; 35. Air flow channel; 36. Ventilation pipe; 361. Oil suction hole; 37. Oil return port; 4. Expansion valve; 5. Evaporator; 61. First sensor; 62. Second sensor; 63. Third sensor; 64. Fourth sensor; 65. Fifth sensor; 66. Sixth sensor. DETAILED DESCRIPTION

[0015] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Example 1

[0017] Reference Figure 1-3 The present embodiment provides a control method for a regenerative refrigeration system, wherein the refrigeration system comprises a compressor 1, a condenser 2 whose input end is connected to the output end of the compressor 1, a gas-liquid separation device 3 connected to the output end of the condenser 2, an expansion valve 4 whose input end is connected to the gas-liquid separation device 3, and an evaporator 5 whose input end is connected to the output end of the expansion valve 4, wherein the gas-liquid separation device 3 comprises a first heat exchange tube 31 having an air inlet end 311 and an air outlet end 312, and a second heat exchange tube 32 capable of heat exchange between the inner medium and the inner medium of the first heat exchange tube 31 and having a liquid inlet end 321 and a liquid outlet end 322, wherein the air inlet end 311 and the air outlet end 312 are respectively connected to the output end of the evaporator 5 and the input end of the compressor 1. The liquid inlet end 321 and the liquid outlet end 322 are respectively connected to the output end of the condenser 2 and the input end of the expansion valve 4, and the refrigeration system also includes a main control unit for controlling the operation of the system, a first sensor 61 and a second sensor 62 for monitoring the medium temperature of the liquid inlet end 321 and the liquid outlet end 322, respectively, a third sensor 63 and a fourth sensor 64 for monitoring the medium temperature of the air inlet end 311 and the air outlet end 312, respectively, and a fifth sensor 65 for monitoring the SST saturation temperature inside the first heat exchange tube 31; specifically, the expansion valve 4, the first sensor 61, the second sensor 62, the third sensor 63, the fourth sensor 64 and the fifth sensor 65 are all electrically connected to the main control unit.

[0018] Control methods include: S1. Set control parameters in the main control unit, the main control unit starts the refrigeration system, and monitors the operating parameters of the refrigeration system in real time; the control parameters include the first superheat stability value M, the superheat stability time T, and the second superheat stability value M'; the operating parameters include the medium temperature T1 of the liquid inlet end 321 collected by the first sensor 61, the medium temperature T2 of the liquid outlet end 322 collected by the second sensor 62, the medium temperature T3 of the air inlet end 311 collected by the third sensor 63, the medium temperature T4 of the air outlet end 312 collected by the fourth sensor 64, and the SST saturation temperature T5 collected by the fifth sensor 65; S2, the main control unit controls the refrigeration system to enter the first operation mode; the first operation mode includes the main control unit calculating the first operation mode superheat actual value SH1=T3-T5 and the first operation mode superheat target value SH1'=10-T1-T2+T3-T4 according to the operation parameters, and comparing SH1 with SH1'. If SH1>SH1', the main control unit opens the expansion valve 4; if SH1<SH1', the main control unit closes the expansion valve 4; the specific first operation mode is usually used to deal with the unstable stage when the refrigeration system is just started, which can quickly increase the return oil temperature, increase the superheat, make the refrigeration system quickly warm up, and improve the heat exchange efficiency; S3, the main control unit calculates the superheat difference m=|SH1- SH1'| of the first operation mode, and compares m with M. When m≤M, the main control unit records the actual stabilization time t, and compares t with T. If t<T, repeat the current step, otherwise execute step S4; when m>M, return to step S2; when the refrigeration system runs smoothly for a period of time, switch the operation mode to avoid excessive load on the refrigeration system and affect the normal operation of the system; S4, the main control unit controls the refrigeration system to enter the second operation mode; the second operation mode includes the main control unit calculating the second operation mode superheat actual value SH2=T4-T5 and the second operation mode superheat target value SH2'=3+T1-T2+T3-T4÷2 according to the operation parameters, and comparing SH2 with SH2'. If SH2>SH2', the main control unit opens the expansion valve 4; if SH1<SH1', the main control unit closes the expansion valve 4; specifically, the second operation mode is usually applied to the stage of stable operation of the refrigeration system, controls the system superheat, ensures the heat exchange performance of the evaporator, and ensures the smooth operation of the system; S5. The main control module calculates the superheat difference m'=|SH2- SH2'| of the second operation mode, and compares m' with M'. If m'≤M', the module returns to step S4; otherwise, the module returns to step S2.

[0019] By monitoring and calculating the temperature difference between the liquid inlet end 321 and the liquid outlet end 322 in the gas-liquid separation device 3, the temperature difference between the gas inlet end 311 and the gas outlet end 312, and the SST saturation temperature in the gas-liquid separation device 3, the opening of the expansion valve 4 is controlled, and then the system superheat is controlled, so that the refrigeration system can automatically adjust the state of the refrigerant according to actual usage, so as to ensure the system heat exchange efficiency and refrigeration effect while stabilizing the system overheating and overcooling, avoiding the problem of liquid inhalation by the compressor, and improving the system reliability.

[0020] In a more preferred embodiment, the control parameters further include a first superheat range threshold value N1~N2 and a second superheat range threshold value N1'~N2', and step S3 further includes: the main control unit compares the superheat difference m with the first superheat range threshold value, and if N1≤m≤N2, continues the current step, otherwise the main control unit controls the refrigeration system to shut down; Step S5 also includes: the main control unit compares the superheat difference m' with the second superheat range threshold, and if N1'≤m'≤N2', the current step is continued, otherwise the main control unit controls the refrigeration system to shut down. By setting the superheat range thresholds in the first operating mode and the second operating mode, when the superheat of the refrigeration system is abnormally high or low due to factors such as equipment failure, the refrigeration system can be shut down in time to prevent system damage.

[0021] In a more preferred embodiment, the refrigeration system further includes a sixth sensor 66 disposed in the first heat exchange tube 31 and used to monitor the oil temperature; In step S1, the control parameters also include a low oil temperature threshold L1 and a high oil temperature threshold L2, and the operating parameters also include the oil temperature T6 collected by the sixth sensor 66; The method between step S2 and step S3 also includes: step S2.1, the main control unit calculates the first oil temperature difference l= T6- T5, and compares the first oil temperature difference with the oil temperature threshold value. If l≤L1, step S3 is executed; if l≥L2, step S4 is executed; Between step S4 and step S5, there is also the following: step S4.1, the main control unit calculates the second oil temperature difference l'= T6- T5, and compares the second oil temperature difference with the oil temperature threshold, if l'≤L1, then execute step S2; if l'≥L2, then execute step S5. By monitoring the returned oil temperature to switch the operation mode of the refrigeration system, the system oil temperature is ensured to be stable, and the problems of poor system operation, easy damage to equipment, and reduced refrigeration effect caused by excessively high or low oil temperature are avoided, thereby ensuring the operation stability and refrigeration effect of the refrigeration system.

[0022] In a more preferred embodiment, the second heat exchange tube 32 is spirally shaped and coiled inside the first heat exchange tube 31, and the liquid inlet end 321 and the liquid outlet end 322 are respectively penetrated to the outside of the first heat exchange tube 31. The spirally coiled second heat exchange tube 32 prolongs the flow time of the liquid refrigerant therein in the first heat exchange tube 31, thereby improving the heat exchange effect between the gaseous refrigerant in the first heat exchange tube 31 and the liquid refrigerant in the second heat exchange tube 32, making it easier to fully vaporize the refrigerant output by the evaporator 5, avoiding liquid inhalation by the compressor 1, and also facilitating the adjustment of the system superheat, improving the system cooling capacity, and ensuring the heat exchange effect.

[0023] In a more preferred embodiment, a plurality of heat exchange fins (not shown in the drawings) are provided on the outer wall of the second heat exchange tube 32, and a channel for gas to flow through is provided between each two adjacent heat exchange fins. Specifically, the heat exchange fins are configured as copper sheets and are relatively perpendicular to the outer wall of the second heat exchange tube 32. The heat exchange fins are used to improve the effect and rate of heat transfer between the medium inside the second heat exchange tube 32 and the medium inside the first heat exchange tube 31, thereby improving the heat exchange effect.

[0024] In a more preferred embodiment, the gas-liquid separation device 3 further includes a first cylinder 33 disposed in the first heat exchange tube 31, and a second cylinder 34 sleeved on the outer periphery of the first cylinder 33. An airflow channel 35 connected to the air inlet end 311 is formed between the outer wall of the first cylinder 33 and the inner wall of the second cylinder 34, and the second heat exchange tube 32 is coiled in the airflow channel 35. The internal space of the first heat exchange tube 31 is separated into a section of annular columnar airflow channel 35 by the first cylinder 33 and the second cylinder 34, and the second heat exchange tube 32 is coiled in the spiral channel, so that the gaseous refrigerant discharged from the evaporator will be restricted in the airflow channel 35 and flow along the airflow channel after passing into the first heat exchange tube 31 from the air inlet end, and will fully contact with the second heat exchange tube 32 during the flow process, thereby achieving the purpose of fully performing heat exchange and improving the heat exchange efficiency.

[0025] In a more preferred embodiment, the gas-liquid separation device 3 also includes a U-shaped ventilation pipe 36 arranged in the first heat exchange tube 31, and an oil suction hole 361 opened at the bottom of the ventilation pipe 36, one end of the ventilation pipe is connected to the air outlet end 312, and the other end of the ventilation pipe 36 extends into the inner cavity of the first heat exchange tube 31 and is located on the outside of the second heat exchange tube 32, and the bottom of the ventilation pipe 36 extends to the bottom of the first heat exchange tube 31. On the one hand, the gas in the first heat exchange tube 31 is discharged through the U-shaped vent pipe 36, and at the same time, the lubricating oil separated from the bottom of the first heat exchange tube 31 is sucked into the vent pipe 36 from the oil suction hole 361 according to the Bernoulli principle, and the lubricating oil is returned to the compressor 1 along with the gas refrigerant, so that the amount of oil in the return gas can be limited by controlling the size of the oil suction hole 361, so as to avoid a large amount of oil in the return gas and affect the normal operation of the refrigeration system; on the other hand, the U-shaped vent pipe is used to extend the flow time and distance of the refrigerant in the first heat exchange tube 31, so that the refrigerant can be fully vaporized during the flow process, which not only improves the heat exchange efficiency, but also further reduces the phenomenon of liquid in the refrigerant returning to the compressor. Example 2

[0026] Reference Figure 4The difference between this embodiment and embodiment 1 is that an oil return port 37 connected to the compressor 1 is provided at the bottom of the first heat exchange tube 31. The lubricating oil separated from the refrigerant is recovered through the oil return port 37 and then returned to the compressor 1. There is no need to set a U-shaped vent pipe 36 and an oil suction hole 361 to recover the lubricating oil, which reduces the difficulty of setting, completely avoids the problem of liquid in the return air of the compressor 1, and is also convenient for sewage discharge through the oil return port 37.

[0027] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The control method of the heat recovery refrigeration system of the present invention monitors and calculates the temperature difference between the liquid inlet and the liquid outlet in the gas-liquid separation device, the temperature difference between the gas inlet and the gas outlet, and the SST saturation temperature in the separation device, so as to control the opening of the expansion valve and then control the system superheat, so that the refrigeration system can automatically adjust the state of the refrigerant according to actual usage conditions, so as to ensure the system heat exchange efficiency and refrigeration effect while stabilizing the system overheating and overcooling, avoiding the problem of liquid inhalation by the compressor, and improving the system reliability.

[0028] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for a regenerative refrigeration system, the refrigeration system comprising a compressor (1), a condenser (2) whose input end is connected to the output end of the compressor (1), a gas-liquid separation device (3) connected to the output end of the condenser (2), an expansion valve (4) whose input end is connected to the gas-liquid separation device (3), and an evaporator (5) whose input end is connected to the output end of the expansion valve (4), characterized in that: The gas-liquid separation device (3) comprises a first heat exchange tube (31) having an air inlet end (311) and an air outlet end (312), and a second heat exchange tube (32) capable of exchanging heat between a medium inside the first heat exchange tube (31) and a medium inside the first heat exchange tube (31) and having a liquid inlet end (321) and a liquid outlet end (322), wherein the air inlet end (311) and the air outlet end (312) are respectively connected to the output end of the evaporator (5) and the input end of the compressor (1), and the liquid inlet end (321) and the liquid outlet end (322) are respectively connected to the condenser ( The refrigeration system further comprises a main control unit for controlling the operation of the system, a first sensor (61) and a second sensor (62) for respectively monitoring the medium temperature at the liquid inlet end (321) and the liquid outlet end (322), a third sensor (63) and a fourth sensor (64) for respectively monitoring the medium temperature at the gas inlet end (311) and the gas outlet end (312), and a fifth sensor (65) for monitoring the SST saturation temperature inside the first heat exchange tube (31); The control method comprises: S1. Setting control parameters in a main control unit, the main control unit starts the refrigeration system, and monitors the operating parameters of the refrigeration system in real time; the control parameters include a first superheat stability value M, a superheat stability time T, and a second superheat stability value M'; the operating parameters include a medium temperature T1 at a liquid inlet end (321) collected by a first sensor (61), a medium temperature T2 at a liquid outlet end (322) collected by a second sensor (62), a medium temperature T3 at an air inlet end (311) collected by a third sensor (63), a medium temperature T4 at an air outlet end (312) collected by a fourth sensor (64), and an SST saturation temperature T5 collected by a fifth sensor (65); S2, the main control unit controls the refrigeration system to enter a first operating mode; the first operating mode includes the main control unit calculating the first operating mode superheat actual value SH1=T3-T5 and the first operating mode superheat target value SH1'=10-(T1-T2+T3-T4) according to the operating parameters, and comparing SH1 with SH1'; if SH1>SH1', the main control unit opens the expansion valve (4); if SH1<SH1', the main control unit closes the expansion valve (4); S3, the main control unit calculates the superheat difference m=|SH1- SH1'| of the first operation mode, and compares m with M. When m≤M, the main control unit records the actual stabilization time t, and compares t with T. If t<T, repeat the current step, otherwise execute step S4; when m>M, return to step S2; S4, the main control unit controls the refrigeration system to enter a second operation mode; the second operation mode includes the main control unit calculating the second operation mode superheat actual value SH2=T4-T5 and the second operation mode superheat target value SH2'=3+(T1-T2+T3-T4)÷2 according to the operation parameters, and comparing SH2 with SH2'; if SH2>SH2', the main control unit opens the expansion valve (4); if SH1<SH1', the main control unit closes the expansion valve (4); S5. The main control module calculates the superheat difference m'=|SH2- SH2'| of the second operation mode, and compares m' with M'. If m'≤M', the module returns to step S4; otherwise, the module returns to step S2.

2. The control method of the regenerative refrigeration system according to claim 1, characterized in that: The control parameters also include a first superheat range threshold value N1-N2, and step S3 also includes: The main control unit compares the superheat difference m with the first superheat range threshold value. If N1≤m≤N2, the current step is continued; otherwise, the main control unit controls the refrigeration system to shut down.

3. The control method of the regenerative refrigeration system according to claim 1, characterized in that: The control parameters also include a second superheat range threshold value N1'-N2', and step S5 also includes: The main control unit compares the superheat difference m' with the second superheat range threshold value. If N1'≤m'≤N2', the current step is continued; otherwise, the main control unit controls the refrigeration system to shut down.

4. The control method of the regenerative refrigeration system according to claim 1, characterized in that: The refrigeration system further comprises a sixth sensor (66) disposed in the first heat exchange tube (31) and used for monitoring oil temperature; In step S1, the control parameters further include a low oil temperature threshold L1 and a high oil temperature threshold L2, and the operating parameters further include an oil temperature T6 collected by a sixth sensor (66); The method between step S2 and step S3 also includes: step S2.1, the main control unit calculates the first oil temperature difference l= T6- T5, and compares the first oil temperature difference with the oil temperature threshold value. If l≤L1, step S3 is executed; if l≥L2, step S4 is executed; Between step S4 and step S5, the following further includes: step S4.1, the main control unit calculates the second oil temperature difference l'= T6-T5, and compares the second oil temperature difference with the oil temperature threshold value; if l'≤L1, execute step S2; if l'≥L2, execute step S5.

5. The control method of the regenerative refrigeration system according to claim 1, characterized in that: The second heat exchange tube (32) is spirally shaped and is arranged in a coiled manner inside the first heat exchange tube (31); the liquid inlet end (321) and the liquid outlet end (322) are respectively passed through the outside of the first heat exchange tube (31).

6. The control method of the regenerative refrigeration system according to claim 5, characterized in that: A plurality of heat exchange fins are arranged on the outer wall of the second heat exchange tube (32), and a channel for gas to flow is provided between each two adjacent heat exchange fins.

7. The control method of the regenerative refrigeration system according to claim 5, characterized in that: The gas-liquid separation device (3) further comprises a first cylinder (33) arranged inside the first heat exchange tube (31), and a second cylinder (34) sleeved around the first cylinder (33); an air flow channel (35) connected to the air inlet end (311) is formed between the outer wall of the first cylinder (33) and the inner wall of the second cylinder (34); and the second heat exchange tube (32) is coiled and arranged inside the air flow channel (35).

8. The control method of the regenerative refrigeration system according to claim 5, characterized in that: The gas-liquid separation device (3) further comprises a U-shaped ventilation pipe (36) arranged in the first heat exchange pipe (31), and an oil suction hole (361) opened at the bottom of the ventilation pipe (36); one end of the ventilation pipe is connected to the gas outlet end (312), the other end of the ventilation pipe (36) extends to the outside of the second heat exchange pipe (32), and the bottom of the ventilation pipe (36) extends to the bottom of the first heat exchange pipe (31).

9. The control method of the regenerative refrigeration system according to claim 5, characterized in that: An oil return port (37) communicating with the compressor (1) is provided at the bottom of the first heat exchange tube (31).

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