Subcritical carbon dioxide refrigeration and heating wide temperature range system and control method thereof

Abstract

The present application relates to the technical field of refrigerant system temperature control, and discloses a subcritical carbon dioxide refrigeration and heating wide temperature range system and a control method thereof, wherein the subcritical carbon dioxide refrigeration and heating wide temperature range system comprises: a circulating loop filled with heat-conducting liquid; a circulating pump is arranged on the circulating loop to circulate and deliver the heat-conducting liquid with controllable temperature to a load to provide heating or cooling; a heating loop is in heat exchange connection with the circulating loop to provide adjustable heating capacity for the heat-conducting liquid in the circulating loop; and a refrigeration loop adopts carbon dioxide as refrigerant and is in heat exchange connection with the circulating loop to provide adjustable refrigeration capacity for the heat-conducting liquid in the circulating loop. The subcritical carbon dioxide refrigeration and heating wide temperature range system and the control method thereof can realize control of any temperature point within-40 DEG C to 250 DEG C and continuous temperature change between-40 DEG C to 250 DEG C.

Description

Technical Field

[0001] This invention relates to the technical field of temperature control in refrigerant systems, and in particular to a subcritical carbon dioxide refrigeration and heating wide-temperature-range system and its control method. Background Technology

[0002] With increasing global environmental awareness, countries are imposing increasingly stringent environmental standards on refrigerants. Traditional fluorinated refrigerants (such as R22 and R410A) have been restricted from use by international conventions such as the Montreal Protocol due to their ozone-depleting potential (ODP) and high global warming potential (GWP). Against this backdrop, carbon dioxide (CO2), a natural refrigerant, has become an important alternative to traditional refrigerants due to its zero ODP and a GWP of only 1.

[0003] In existing carbon dioxide refrigeration systems, low temperature control accuracy and slow response speed are prominent issues, especially making it difficult to maintain stable operation under frequent load changes. Current technologies primarily utilize carbon dioxide only for low-temperature refrigeration; in high-temperature environments, external cooling equipment is required for pre-cooling before intervention. This prevents the direct utilization of carbon dioxide's own thermodynamic properties for rapid cooling from high to low temperatures, resulting in discontinuous temperature range coverage and low cooling efficiency. Furthermore, difficulties in oil return and reduced circulation efficiency in low-temperature environments, along with the limited adjustment capabilities of conventional expansion valves and their inability to accurately match the demands of multiple temperature zones, further limit the system's practicality. Summary of the Invention

[0004] Therefore, the purpose of this invention is to overcome the problems in the prior art where carbon dioxide refrigerant is only used in low-temperature refrigeration scenarios, and in high-temperature environments, it requires external cooling equipment for pre-cooling before intervention, and cannot directly utilize the thermodynamic properties of carbon dioxide itself to achieve rapid cooling from high to low temperatures, resulting in discontinuous temperature range coverage and low cooling efficiency. This invention provides a subcritical carbon dioxide refrigeration and heating wide-temperature-range system and its control method. By integrating a heating circuit with a heater and a refrigeration circuit using carbon dioxide as the refrigerant, it provides adjustable heating and cooling capacity for the circulation loop. This allows for control of any temperature point within -40℃ to 250℃, meeting the needs of extreme high and low temperature conditions; and also enables continuous temperature variation within the -40℃ to 250℃ range, avoiding discontinuous temperature range coverage.

[0005] To address the aforementioned technical problems, this invention provides a subcritical carbon dioxide refrigeration and heating wide-temperature-range system, comprising: a circulation loop filled with a heat-conducting liquid; a circulation pump on the circulation loop for circulating and delivering temperature-controllable heat-conducting liquid to a load for heating or cooling; a heating loop connected to the circulation loop for heat exchange; the heating loop including a heater for providing adjustable heating to the heat-conducting liquid in the circulation loop; and a refrigeration loop using carbon dioxide as a refrigerant and connected to the circulation loop for providing adjustable cooling to the heat-conducting liquid in the circulation loop; the refrigeration loop including a compressor, a cooler, a refrigeration expansion valve, and an evaporator connected in sequence, with a first-side heat exchange channel of the evaporator connected to the circulation loop.

[0006] Preferably, the refrigeration circuit further includes, in sequence, the following components forming the circuit: a first refrigeration branch, which is connected to the second-side heat exchange channel of the evaporator for heat exchange with the circulation loop; a second refrigeration branch, the input end of which is connected to the output end of the first refrigeration branch, and the output end of the second refrigeration branch is connected to the compressor; a third refrigeration branch, the input end of which is connected to the compressor, and the output end of which is connected to a dryer filter; the third refrigeration branch is connected to the first-side heat exchange channel of the cooler, and the second-side heat exchange channel of the cooler is connected to a cooling loop, which is used to cool the carbon dioxide in the third refrigeration branch; a fourth refrigeration branch, the input end of which is connected to the dryer filter, and the output end of which is connected to the refrigeration expansion valve; and a fifth refrigeration branch, the input end of which is connected to the refrigeration expansion valve, and the output end of which is connected to the input end of the first refrigeration branch.

[0007] Preferably, the refrigeration circuit further includes: a sixth refrigeration branch, wherein a hot gas bypass expansion valve is provided on the sixth refrigeration branch; the input end of the sixth refrigeration branch is connected to the input end of the third refrigeration branch, and the output end of the sixth refrigeration branch is connected to the input end of the first refrigeration branch; a seventh refrigeration branch, wherein a vapor injection enthalpy-increasing expansion valve is provided on the seventh refrigeration branch; the input end of the seventh refrigeration branch is connected to the output end of the fourth refrigeration branch, and the output end of the seventh refrigeration branch is connected to the gas injection port of the compressor; an economizer, wherein the first heat exchange channel of the economizer is connected to the seventh refrigeration branch, and the second heat exchange channel of the economizer is connected to the fourth refrigeration branch; and a regenerator, wherein the first heat exchange channel of the regenerator is connected to the second refrigeration branch, and the second heat exchange channel of the regenerator is connected to the fifth refrigeration branch.

[0008] Preferably, the circulation loop includes: a first circulation branch, the input end of which is connected to a liquid storage unit containing a heat-conducting liquid; the upstream of the first circulation branch is connected to the circulation pump, and the downstream of the first circulation branch is connected to the heater; a second circulation branch, the input end of which is connected to the output end of the first circulation branch; the second circulation branch is connected to the load for providing cooling or heating to the load; a third circulation branch, the input end of which is connected to the output end of the second circulation branch, and the output end of the third circulation branch is connected to the liquid storage unit; the third circulation branch is connected to the first side heat exchange channel of the evaporator for heat exchange with the first refrigeration branch.

[0009] Preferably, the liquid storage unit includes: a gas-liquid separator, the bottom of which has a liquid outlet connected to the input end of the first circulation branch; a first side of which has a liquid inlet connected to the output end of the third circulation branch; a top of which has an exhaust port; a second side of which has a compensation port; and an expansion tank, the top of which has a filling port for adding heat-conducting liquid; an upper part of which has an air inlet connected to the exhaust port; and a bottom of which has a replenishment port connected to the compensation port.

[0010] On the other hand, the present invention provides a control method for a subcritical carbon dioxide refrigeration and heating wide-temperature-range system, comprising: adjusting the duty cycle of a solid-state relay, the flow rate of a circulating pump, the speed of a compressor, and / or the opening of an expansion valve according to the relationship between the temperature difference between the outlet temperature and the target temperature and a preset temperature, and the target temperature, so that the outlet temperature approaches the target temperature; wherein, the target temperature is within (-40, 250); the expansion valve includes: a refrigeration expansion valve, a hot gas bypass expansion valve, and / or a vapor injection enthalpy-increasing expansion valve; the outlet temperature is the temperature of the heat transfer fluid before it flows through the load.

[0011] Preferably, the step of bringing the outlet temperature close to the target temperature includes: when ΔT ≥ a third threshold: setting the compressor speed, refrigeration expansion valve opening, and hot gas bypass expansion valve opening according to the target temperature; when the target temperature belongs to the (180, 250] temperature range or the (80, 180] temperature range, setting the heating circuit to a low-power state; when the target temperature belongs to the (5, 80] temperature range or the (-20, 5] temperature range or the (-40, -20] temperature range, turning off the heater; when the target temperature belongs to the (-40, -20] temperature range, setting the vapor injection enthalpy expansion valve opening according to the target temperature; when -3 When threshold < ΔT < third threshold: When the target temperature belongs to the (180, 250] temperature range or the (80, 180] temperature range: shut down the compressor; set the solid-state relay duty cycle and / or circulation pump flow rate according to the target temperature; When the target temperature belongs to the (5, 80] temperature range or the (-20, 5] temperature range: set the heating circuit to low power mode; set the compressor speed, refrigeration expansion valve opening, and hot gas bypass expansion valve opening according to the target temperature; When the target temperature belongs to the (-40, -20] temperature range: shut down the heater; set the compressor speed, refrigeration expansion valve opening, and hot gas bypass expansion valve opening according to the target temperature. Adjust the opening degree of the expansion valve and the opening degree of the jet enthalpy expansion valve; when ΔT ≤ - third threshold: when the target temperature belongs to the (180, 250] temperature zone, (80, 180] temperature zone, or (5, 80] temperature zone: shut down the compressor; set the solid-state relay duty cycle and / or circulation pump flow rate according to the target temperature; when the target temperature belongs to the (-20, 5] temperature zone: set the refrigeration circuit to low power state; set the solid-state relay duty cycle and / or circulation pump flow rate according to the target temperature; when the target temperature belongs to the (-40, -20] temperature zone: set the heating circuit to low power state, and set the compressor speed... Set to low speed; set the opening of the refrigeration expansion valve, the hot gas bypass expansion valve, and the vapor injection enthalpy expansion valve according to the target temperature; where △T = outlet temperature - target temperature; the third threshold belongs to [1,5]; the low power state of the heating circuit includes: solid-state relay duty cycle of 0% to 40%; the low power state of the refrigeration circuit includes: compressor speed of 0 rpm to 2400 rpm, refrigeration expansion valve opening of 0% to 30%, vapor injection enthalpy expansion valve opening of 0%, hot gas bypass expansion valve opening of 40% to 100%; low speed of 2000 rpm to 2800 rpm.

[0012] Preferably, when the outlet temperature approaches the target temperature and a constant temperature environment is required for the load: when the target temperature is in the (80, 250) temperature range: adjust the duty cycle of the solid-state relay in the heater and / or the flow rate of the circulating pump according to the real-time temperature difference between the real-time outlet temperature and the target temperature to make the real-time outlet temperature approach the target temperature; when the target temperature is in the (5, 80) temperature range: adjust the duty cycle of the solid-state relay in the heater, the flow rate of the circulating pump, the compressor speed, and / or the opening degree of the expansion valve according to the real-time temperature difference between the real-time outlet temperature and the target temperature. The real-time outlet temperature is brought close to the target temperature. When the target temperature is in the (-40, 5) temperature range: the circulation pump flow rate, compressor speed, and / or expansion valve opening are adjusted according to the real-time temperature difference between the real-time outlet temperature and the target temperature to bring the real-time outlet temperature close to the target temperature. Wherein, when the target temperature is in the (-20, 80) temperature range, the expansion valve includes a refrigeration expansion valve and / or a hot gas bypass expansion valve; when the target temperature is in the (-40, -20) temperature range, the expansion valve includes a refrigeration expansion valve, a hot gas bypass expansion valve, and / or a vapor injection enthalpy-increasing expansion valve.

[0013] Preferably, when the outlet temperature and the target temperature are in the same temperature range, and the load needs to be heated uniformly at a preset heating rate: the compressor speed is set to 0, the expansion valve opening is set to 0, and the duty cycle of the solid-state relay and / or the circulation pump flow rate is adjusted so that the real-time outlet temperature approaches the target temperature at the preset heating rate: when the solid-state relay duty cycle is <100% and the actual heating rate is <the preset heating rate, the solid-state relay duty cycle is increased; when the solid-state relay duty cycle is =100% and the actual heating rate is <the preset heating rate, the circulation pump flow rate is decreased; when the solid-state relay duty cycle is >0% and the actual heating rate is >the preset heating rate, the solid-state relay duty cycle is decreased; when the solid-state relay duty cycle is =0% and the actual heating rate is >the preset heating rate, the circulation pump flow rate is increased.

[0014] Preferably, when the outlet temperature and the target temperature belong to the same temperature range, and the load needs to be cooled uniformly at a preset cooling rate: the solid-state relay duty cycle is set to 0, and the circulating pump flow rate, compressor speed, and / or expansion valve opening are adjusted so that the real-time outlet temperature approaches the target temperature at a preset cooling rate; when both the outlet temperature and the target temperature belong to the (80, 250) temperature range: when 0 ≤ circulating pump flow rate < rated flow rate, and the real-time cooling rate < preset cooling rate, the circulating pump flow rate is increased; when the circulating pump flow rate = rated flow rate, and the real-time cooling rate < preset cooling rate, the circulating pump flow rate is increased. When the real-time cooling rate is within the preset cooling rate range, increase the compressor speed, decrease the opening of the hot gas bypass expansion valve, and / or increase the opening of the refrigeration expansion valve; when 0 < circulating pump flow rate ≤ rated flow rate, and the real-time cooling rate > preset cooling rate, decrease the circulating pump flow rate; when the circulating pump flow rate = 0, and the real-time cooling rate > preset cooling rate, decrease the compressor speed, increase the opening of the hot gas bypass expansion valve, and / or decrease the opening of the refrigeration expansion valve; when the target temperature is within the (-20, 80] temperature range: when the real-time cooling rate < preset cooling rate, increase the compressor speed and / or increase the opening of the refrigeration expansion valve. Opening degree; When both the compressor speed and the opening degree of the refrigeration expansion valve are at the upper limit of the current temperature zone configuration, and the real-time cooling rate is less than the preset cooling rate, decrease the opening degree of the hot gas bypass expansion valve; when the real-time cooling rate is greater than the preset cooling rate, decrease the compressor speed and / or decrease the opening degree of the refrigeration expansion valve; when both the compressor speed and the opening degree of the refrigeration expansion valve are at the lower limit of the current temperature zone configuration, and the real-time cooling rate is greater than the preset cooling rate, increase the opening degree of the hot gas bypass expansion valve; when the target temperature is within the (-40, -20] temperature zone: when the real-time cooling rate is less than the preset cooling rate When the refrigeration expansion valve opening is increased and / or the vapor injection enthalpy-increasing expansion valve opening is increased; when both the refrigeration expansion valve opening and the vapor injection enthalpy-increasing expansion valve opening are the upper limits configured for the current temperature zone, and the real-time cooling rate is less than the preset cooling rate, the hot gas bypass expansion valve opening is decreased; when the real-time cooling rate is greater than the preset cooling rate, the refrigeration expansion valve opening and / or the vapor injection enthalpy-increasing expansion valve opening is decreased; when both the refrigeration expansion valve opening and the vapor injection enthalpy-increasing expansion valve opening are the lower limits configured for the current temperature zone, and the real-time cooling rate is greater than the preset cooling rate, the hot gas bypass expansion valve opening is increased.

[0015] The advantages of the above-mentioned technical solution of the present invention compared with the prior art are as follows: The subcritical carbon dioxide refrigeration and heating wide-temperature-range system of the present invention, by integrating a heating circuit and a refrigeration circuit with carbon dioxide as the refrigerant, achieves a wide temperature range coverage from -40℃ to 250℃, meeting the requirements of extreme high and low temperature conditions and improving the practicality of the system. Furthermore, by providing adjustable heating through the heater and adjustable cooling through the carbon dioxide refrigeration circuit, control of any temperature point within the range of -40℃ to 250℃ can be achieved without the need for additional external cooling equipment. In addition, the circulation circuit uses a heat-conducting liquid as an intermediate heat transfer medium, avoiding direct contact between the refrigerant carbon dioxide and the load, enabling long-distance transportation and multi-point temperature control, while reducing the risk of system leakage.

[0016] The control method of the subcritical carbon dioxide refrigeration and heating wide-temperature-range system described in this invention combines and adjusts various actuators, such as the duty cycle of a solid-state relay, the flow rate of a circulating pump, the speed of a compressor, and / or the opening degree of an expansion valve, based on the relationship between the temperature difference between the outlet temperature and the target temperature and the preset temperature, as well as the target temperature. This method can achieve continuous temperature variation between -40℃ and 250℃, avoid energy waste caused by overheating or overcooling, and improve the temperature variation rate. Attached Figure Description

[0017] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0018] Figure 1 This is a schematic diagram of a subcritical carbon dioxide refrigeration and heating wide-temperature-range system in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of a liquid storage unit in an embodiment of the present invention.

[0020] Figure 3 This is a schematic flowchart of a control method for a subcritical carbon dioxide refrigeration and heating wide-temperature-range system in an embodiment of the present invention.

[0021] Explanation of reference numerals in the accompanying drawings: 11. First circulation branch; 12. Second circulation branch; 13. Third circulation branch; 14. Liquid storage unit; 15. Gas-liquid separator; 151. Liquid outlet; 152. Liquid inlet; 153. Exhaust port; 154. Compensation port; 16. Expansion tank; 161. Liquid filling port; 162. Air inlet; 163. Liquid replenishment port; 164. Liquid level sensor; 171. Fourth temperature sensor; 172. Fifth temperature sensor; 18. Circulation pump; 21. Heater; 22. Sixth temperature sensor; 31. First refrigeration branch; 32. Second refrigeration branch; 33. Third Refrigeration branch; 34, fourth refrigeration branch; 35, fifth refrigeration branch; 36, sixth refrigeration branch; 37, seventh refrigeration branch; 381, economizer; 382, ​​regenerator; 383, compressor; 384, cooler; 385, evaporator; 386, dryer filter; 387, refrigeration expansion valve; 388, hot gas bypass expansion valve; 389, vapor injection enthalpy-increasing expansion valve; 391, first temperature sensor; 392, first pressure sensor; 393, second temperature sensor; 394, second pressure sensor; 395, third pressure sensor; 396, third temperature sensor; 4, load. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0023] Example 1: This example discloses a subcritical carbon dioxide refrigeration and heating wide temperature range system.

[0024] Traditional temperature control systems often employ independent refrigeration and heating control methods, which not only suffer from energy waste, system complexity, and control lag, but also fail to meet the dual requirements of cold and heat sources for continuous chemical reaction loads over a wide temperature range, such as covering a wide temperature range of -40℃ to 250℃. Furthermore, traditional temperature control systems typically adjust a single parameter for a single temperature zone, lacking differentiated control strategies tailored to the thermodynamic characteristics of different temperature zones, resulting in uneven control accuracy and insufficient stability across the entire temperature range. Especially in processes involving multi-step chemical reactions, different reaction stages may require separate high-temperature heating (e.g., catalytic activation) and low-temperature cooling (e.g., product crystallization). Traditional temperature control systems require independent heating and cooling equipment, leading to complex system structures, large footprints, and response delays during heating and cooling transitions, affecting reaction continuity and product quality. Therefore, this embodiment introduces a subcritical carbon dioxide refrigeration and heating system with a wide temperature range.

[0025] The subcritical carbon dioxide refrigeration and heating wide-temperature-range system of this embodiment includes: a circulation loop, a heating loop, and a refrigeration loop.

[0026] In application, the heating circuit is connected to the circulation circuit for heat exchange, providing an adjustable heating amount for the heat transfer fluid within the circulation circuit. The refrigeration circuit uses carbon dioxide as the refrigerant and is also connected to the circulation circuit for heat exchange, providing an adjustable cooling amount for the heat transfer fluid within the circulation circuit.

[0027] A circulation pump 18 is installed in the circulation loop, and the circulation loop is filled with heat transfer fluid to circulate and deliver temperature-controlled heat transfer fluid to the load 4 for heating or cooling. The heat transfer fluid can be silicone oil, such as polydimethylsiloxane.

[0028] The heating circuit in this embodiment includes a heater 21 and a solid-state relay.

[0029] In application, heater 21 can be a resistance heater, whose heating power can be continuously adjusted within the range of 0% to 100% to provide adjustable heating for the heat transfer fluid in the circulation loop; solid-state relay is electrically connected to the power supply circuit of heater 21 to control the on / off duty cycle of heater 21.

[0030] In practical applications, the heating circuit may also include a sixth temperature sensor 22, which is used to detect the temperature of the heater 21.

[0031] In actual implementation, the heating circuit may also include a power feedback sensor, which is used to detect the actual output power of the heater 21 in real time. The circulation circuit in this embodiment includes, in sequence, a first circulation branch 11, a second circulation branch 12, and a third circulation branch 13, forming the circuit. (Refer to...) Figure 1 .

[0032] The upstream of the first circulation branch 11 is connected to the circulation pump 18, which provides power for the circulation of the heat transfer fluid; the downstream of the first circulation branch 11 is connected to the heater 21 of the heating circuit, which provides heating for the heat transfer fluid. Furthermore, the input end of the first circulation branch 11 is connected to the liquid storage unit 14, which stores the heat transfer fluid. Even further, the output end of the first circulation branch 11 is equipped with a fourth temperature sensor 171. The fourth temperature sensor 171 is used to detect the outlet temperature of the heat transfer fluid at the output end of the first circulation branch 11, that is, the temperature of the heat transfer fluid before it flows through the load 4.

[0033] The input terminal of the second circulation branch 12 is connected to the output terminal of the first circulation branch 11, and the output terminal of the second circulation branch 12 is connected to the input terminal of the third circulation branch 13. Furthermore, the second circulation branch 12 is connected to the load 4 for providing cooling or heating to the load 4.

[0034] The input of the third circulation branch 13 is connected to the output of the second circulation branch 12, and the output of the third circulation branch 13 is connected to the liquid storage unit 14. Furthermore, the third circulation branch 13 is connected to the first heat exchange channel of the evaporator 385, and the second heat exchange channel of the evaporator 385 is connected to the refrigeration circuit to provide cooling capacity for the heat transfer fluid. Even further, the input of the third circulation branch 13 is equipped with a fifth temperature sensor 172, which is used to detect the return temperature of the heat transfer fluid at the input of the third circulation branch 13, i.e., the temperature of the heat transfer fluid after flowing through the load 4. When the temperature difference between the return temperature and the outlet temperature deviates from the expected temperature difference of the current chemical reaction by more than a threshold, an alarm signal is issued to initiate equipment maintenance.

[0035] The liquid storage unit 14 in this embodiment includes a gas-liquid separator 15 and an expansion tank 16.

[0036] refer to Figure 2 The gas-liquid separator 15 has a liquid outlet 151 at its bottom, which is connected to the input end of the first circulation branch 11. It can replenish the heat transfer fluid to the circulation loop through gravity. The gas-liquid separator 15 has a liquid inlet 152 on its first side, which is connected to the output end of the third circulation branch 13 and is used to recover the heat transfer fluid that has flowed through the load 4 in the circulation loop. The gas-liquid separator 15 has an exhaust port 153 at its top to discharge any rising gas. The gas-liquid separator 15 has a compensation port 154 on its second side, which is horizontally offset from the liquid inlet 152 to prevent the heat transfer fluid pumped from the third circulation branch 13 from flowing too fast and splashing into the compensation port 154 when pumped into the gas-liquid separator 15 through the liquid inlet 152.

[0037] refer to Figure 2 The expansion tank 16 has an air inlet 162 at its upper part, which is connected to an exhaust port 153 for collecting the gas discharged from the gas-liquid separator 15. The bottom of the expansion tank 16 has a replenishment port 163, which is connected to a compensation port 154, allowing the gas-liquid separator 15 to be replenished with heat transfer fluid by gravity. The top of the expansion tank 16 has a filling port 161 for adding heat transfer fluid. Furthermore, the expansion tank 16 is equipped with a level sensor 164 to detect the level of the heat transfer fluid inside, facilitating timely replenishment.

[0038] The refrigeration circuit in this embodiment also includes the following components connected sequentially to form the circuit: a first refrigeration branch 31, a second refrigeration branch 32, a third refrigeration branch 33, a fourth refrigeration branch 34, and a fifth refrigeration branch 35. (See reference...) Figure 1Furthermore, the refrigeration circuit also includes a sixth refrigeration branch 36 and a seventh refrigeration branch 37. In addition, the refrigeration circuit of this embodiment includes a compressor 383, a cooler 384, a refrigeration expansion valve 387, and an evaporator 385 connected in sequence. The compressor 383 is a carbon dioxide inverter compressor, capable of withstanding an exhaust temperature of 115°C and a maximum operating pressure of 13 MPa; furthermore, the expansion valves in this application are all electronic expansion valves. Furthermore, the refrigeration circuit also includes an economizer 381 and a regenerator 382.

[0039] The first refrigeration branch 31 is connected to the second side heat exchange channel of the evaporator 385, and the first side heat exchange channel of the evaporator 385 is connected to the circulation loop, so that the third circulation branch 13 exchanges heat with the first refrigeration branch 31, thereby realizing heat exchange between the refrigeration loop and the circulation loop.

[0040] The input end of the second refrigeration branch 32 is connected to the output end of the first refrigeration branch 31, and the output end of the second refrigeration branch 32 is connected to the compressor 383. Furthermore, the second refrigeration branch 32 is connected to the first side heat exchange channel of the regenerator 382. Even further, the second refrigeration branch 32 is equipped with a first temperature sensor 391 and a first pressure sensor 392. The first temperature sensor 391 is used to detect the suction temperature at the input end of the second refrigeration branch 32; the first pressure sensor 392 is used to detect the suction pressure at the output end of the second refrigeration branch 32.

[0041] The input end of the third refrigeration branch 33 is connected to the compressor 383, and the output end of the third refrigeration branch 33 is connected to the dryer filter 386. Further, the third refrigeration branch 33 is connected to the first side heat exchange channel of the cooler 384, and the second side heat exchange channel of the cooler 384 is connected to the cooling circuit, which is used to cool the carbon dioxide in the third refrigeration branch 33. Even further, the third refrigeration branch 33 is equipped with a second temperature sensor 393 and a second pressure sensor 394. The second temperature sensor 393 is used to detect the exhaust temperature at the outlet of the compressor 383; the second pressure sensor 394 is used to detect the exhaust pressure at the outlet of the compressor 383.

[0042] The input end of the fourth refrigeration branch 34 is connected to the dryer filter 386, and the output end of the fourth refrigeration branch 34 is connected to the refrigeration expansion valve 387. Furthermore, the fourth refrigeration branch 34 is connected to the second side heat exchange channel of the economizer 381 for heat exchange between the fourth refrigeration branch 34 and the second refrigeration branch 32. Even further, the fourth refrigeration branch 34 is equipped with a third temperature sensor 396, which is used to detect the condensation temperature of carbon dioxide in the fourth refrigeration branch 34 after passing through the economizer 381.

[0043] The input end of the fifth refrigeration branch 35 is connected to the refrigeration expansion valve 387, and the output end of the fifth refrigeration branch 35 is connected to the input end of the first refrigeration branch 31. Furthermore, the fifth refrigeration branch 35 is connected to the second side heat exchange channel of the regenerator 382 for heat exchange between the second refrigeration branch 32 and the fifth refrigeration branch 35.

[0044] The input terminal of the sixth refrigeration branch 36 is connected to the input terminal of the third refrigeration branch 33, and the output terminal of the sixth refrigeration branch 36 is connected to the input terminal of the first refrigeration branch 31. Furthermore, the sixth refrigeration branch 36 is equipped with a hot gas bypass expansion valve 388.

[0045] The input end of the seventh refrigeration branch 37 is connected to the output end of the fourth refrigeration branch 34, and the output end of the seventh refrigeration branch 37 is connected to the gas injection port of the compressor 383. Furthermore, the seventh refrigeration branch 37 is connected to the first-side heat exchange channel of the economizer 381, and is equipped with a vapor injection enthalpy-increasing expansion valve 389 and a third pressure sensor 395. Specifically, the upstream of the seventh refrigeration branch 37 is equipped with the vapor injection enthalpy-increasing expansion valve 389; the midstream of the seventh refrigeration branch 37 is connected to the first-side heat exchange channel of the economizer 381 for heat exchange between the seventh refrigeration branch 37 and the fourth refrigeration branch 34; and the downstream of the seventh refrigeration branch 37 is equipped with the third pressure sensor 395, which is used to detect the intermediate pressure at the output end of the seventh refrigeration branch 37.

[0046] In summary, this embodiment integrates a circulation loop, a heating loop, and a cooling loop to achieve continuous heating and cooling of load 4, meeting the multi-mode temperature control requirements of continuous chemical reactions over a wide temperature range. A circulation pump 18 is installed in the circulation loop to deliver temperature-controlled heat transfer fluid to load 4, ensuring temperature stability during the reaction process. The heating loop provides adjustable heating through heater 21, suitable for the activation stage of endothermic reactions. The cooling loop uses carbon dioxide as a refrigerant, exchanging heat with the circulation loop through evaporator 385 to provide adjustable cooling for exothermic reactions or product cooling, expanding the system's application capability across the entire temperature range from high to low. Furthermore, a gas-liquid separator 15 and an expansion tank 16 are installed in the liquid storage unit 14. The gravity-fed liquid replenishment structure of the exhaust port 153 and the replenishment port 163 effectively buffers the volume changes caused by thermal expansion and contraction of the heat transfer fluid, maintaining stable system pressure, preventing liquid leakage or cavitation, and improving the system's reliability during operation over a wide temperature range.

[0047] Example 2: This example discloses a control method for a subcritical carbon dioxide refrigeration and heating wide-temperature-range system. The subcritical carbon dioxide refrigeration and heating wide-temperature-range system can be the subcritical carbon dioxide refrigeration and heating wide-temperature-range system described in Example 1.

[0048] Continuous chemical reaction processes demand high precision in temperature control. For example, in drug synthesis or polymer polymerization, temperature fluctuations exceeding ±1℃ can lead to increased side reactions or decreased product purity. Existing refrigeration systems often employ single-mode control, such as adjusting only the compressor frequency, which is insufficient to adapt to the dynamic changes in cooling and heating demands at different reaction stages. Especially when the target temperature spans multiple temperature zones, such as a jump from -40℃ to 180℃, traditional control strategies cannot differentiate based on the temperature difference between the outlet and target temperatures, or the characteristics of the target temperature zone. This results in delayed temperature control response, large overshoot, and even system oscillations, failing to meet the temperature stability requirements of continuous production.

[0049] refer to Figure 3 The control method of the subcritical carbon dioxide refrigeration and heating wide temperature range system in this embodiment includes steps SS1-SS3.

[0050] Step SS1: When the outlet temperature of the heat transfer fluid is not equal to the target temperature of load 4, calculate the temperature difference between the outlet temperature and the target temperature.

[0051] Step SS2: Compare the temperature difference between the outlet temperature and the target temperature with the preset temperature.

[0052] Step SS3: Based on the relationship between the temperature difference between the outlet temperature and the target temperature and the preset temperature, and the target temperature, adjust the duty cycle of the solid-state relay, the flow rate of the circulating pump 18, the compressor speed, and / or the opening of the expansion valve to make the outlet temperature approach the target temperature.

[0053] In application, when the outlet temperature is higher than the target temperature, prioritize adjusting the duty cycle of the solid-state relay and / or the flow rate of the circulating pump 18, and then adjust the compressor speed and / or the expansion valve opening. When the outlet temperature is lower than the target temperature, prioritize adjusting the compressor speed and / or the expansion valve opening, and then adjust the duty cycle of the solid-state relay and / or the flow rate of the circulating pump 18. The expansion valve includes: a refrigeration expansion valve 387, a hot gas bypass expansion valve 388, and / or a vapor injection enthalpy-increasing expansion valve 389.

[0054] In practical applications, the target temperature is within the range of (-40, 250). Furthermore, to improve the flexibility and accuracy of temperature control, the target temperature is divided into multiple temperature zones, such as the first temperature zone (180, 250], the second temperature zone (80, 180], the third temperature zone (5, 80], the fourth temperature zone (-20, 5], and the fifth temperature zone (-40, -20).

[0055] In some embodiments, when the outlet temperature is brought close to the target temperature, the relationship between the temperature difference ΔT between the outlet temperature and the target temperature and the preset temperature is first determined. Then, based on the temperature range to which the target temperature belongs and the relationship between ΔT and the preset temperature, the component parameters are adjusted to bring the outlet temperature close to the target temperature. Wherein, ΔT = outlet temperature - target temperature.

[0056] When applying the application, the preset temperature includes at least a third threshold, which is in the range [1,5].

[0057] When △T≥Third threshold: Set compressor speed, refrigeration expansion valve opening, and hot gas bypass expansion valve opening according to target temperature.

[0058] Furthermore, when the target temperature falls within the (180, 250] temperature range or the (80, 180] temperature range: the heating circuit is set to a low-power state; the compressor speed, refrigeration expansion valve opening, and hot gas bypass expansion valve opening are set according to the target temperature; when the target temperature falls within the (5, 80] temperature range or the (-20, 5] temperature range, heater 21 is turned off; the compressor speed, refrigeration expansion valve opening, and hot gas bypass expansion valve opening are set according to the target temperature; when the target temperature falls within the (-40, -20] temperature range: heater 21 is turned off; the compressor speed, refrigeration expansion valve opening, hot gas bypass expansion valve opening, and vapor injection enthalpy expansion valve opening are set according to the target temperature.

[0059] When -third threshold < ΔT < third threshold.

[0060] When the target temperature is in the (180, 250] temperature range or the (80, 180] temperature range: shut down compressor 383; set the solid-state relay duty cycle and / or circulation pump flow rate according to the target temperature; when the target temperature is in the (5, 80] temperature range or the (-20, 5] temperature range: set the heating circuit to low power mode; set the compressor speed, refrigeration expansion valve opening, and hot gas bypass expansion valve opening according to the target temperature; when the target temperature is in the (-40, -20] temperature range: shut down heater 21; set the compressor speed, refrigeration expansion valve opening, hot gas bypass expansion valve opening, and jet enthalpy expansion valve opening according to the target temperature.

[0061] When △T≤-third threshold.

[0062] When the target temperature is in the (180, 250] temperature range, or the (80, 180] temperature range, or the (5, 80] temperature range: shut down compressor 383; set the solid-state relay duty cycle and / or circulation pump flow rate according to the target temperature; when the target temperature is in the (-20, 5] temperature range: set the refrigeration circuit to low power mode; set the solid-state relay duty cycle and / or circulation pump flow rate according to the target temperature; when the target temperature is in the (-40, -20] temperature range: set the heating circuit to low power mode and set the compressor speed to low speed; set the opening of the refrigeration expansion valve, the hot gas bypass expansion valve, and the vapor injection enthalpy expansion valve according to the target temperature.

[0063] The low-power states of the heating circuit include: solid-state relay duty cycle of 0% to 40% and low speed of 2000 rpm to 2800 rpm. The low-power states of the refrigeration circuit include: compressor speed of 0 rpm to 2400 rpm, refrigeration expansion valve opening of 0% to 30%, vapor injection enthalpy-increasing expansion valve opening of 0%, and hot gas bypass expansion valve opening of 40% to 100%.

[0064] In practical applications, when the target temperature is within the (180, 250) temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 100%, circulating pump flow rate is 80% to 100% of rated flow rate, compressor speed is 2500 rpm to 4500 rpm, refrigeration expansion valve opening is 30% to 100%, hot gas bypass expansion valve opening is 0% to 30%, and vapor injection enthalpy-increasing expansion valve opening is 0%.

[0065] When the target temperature is within the (80, 180) temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 90%, circulating pump flow rate is 60% to 80% of rated flow rate, compressor speed is 2500 rpm to 4500 rpm, refrigeration expansion valve opening is 30% to 100%, hot gas bypass expansion valve opening is 0% to 30%, and vapor injection enthalpy-increasing expansion valve opening is 0%.

[0066] When the target temperature is within the (5,80] temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 90%, circulating pump flow rate is 50% to 70% of rated flow rate, compressor speed is 2000 rpm to 4000 rpm, refrigeration expansion valve opening is 0% to 100%, hot gas bypass expansion valve opening is 0% to 40%, and vapor injection enthalpy-increasing expansion valve opening is 0%.

[0067] When the target temperature is within the range of (-20, 5), the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 80%, circulating pump flow rate is 40% to 60% of rated flow rate, compressor speed is 2400 rpm to 4000 rpm, refrigeration expansion valve opening is 5% to 80%, hot gas bypass expansion valve opening is 10% to 100%, and vapor injection enthalpy-increasing expansion valve opening is 0%.

[0068] When the target temperature is within the range of (-40, -20), the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 30%, circulating pump flow rate is 30% to 50% of rated flow rate, compressor speed is 2800 rpm to 5000 rpm, refrigeration expansion valve opening is 5% to 90%, hot gas bypass expansion valve opening is 5% to 100%, and vapor injection enthalpy-increasing expansion valve opening is 15% to 40%.

[0069] In actual implementation, when △T≤-third threshold.

[0070] When the target temperature is within the (180, 250) temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 40% to 100%, circulating pump flow rate is 80% to 100% of rated flow rate, compressor speed is 0 rpm, refrigeration expansion valve opening is 0%, hot gas bypass expansion valve opening is 0%, and jet enthalpy expansion valve opening is 0%.

[0071] When the target temperature is within the (80, 180) temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 50% to 90%, circulating pump flow rate is 60% to 80% of rated flow rate, compressor speed is 0 rpm, refrigeration expansion valve opening is 0%, hot gas bypass expansion valve opening is 0%, and jet enthalpy expansion valve opening is 0%.

[0072] When the target temperature is in the (5,80) temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 20% to 90%, circulating pump flow rate is 50% to 70% of rated flow rate, compressor speed is 0 rpm, refrigeration expansion valve opening is 0%, hot gas bypass expansion valve opening is 0%, and jet enthalpy expansion valve opening is 0%.

[0073] When the target temperature is within the (-20, 5] temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 80%, circulating pump flow rate is 40% to 60% of rated flow rate, compressor speed is 2400 rpm, refrigeration expansion valve opening is 5% to 30%, hot gas bypass expansion valve opening is 45% to 100%, and jet enthalpy expansion valve opening is 0%.

[0074] When the target temperature is within the range of (-40, -20), the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 30%, circulating pump flow rate is 30% to 50% of rated flow rate, compressor speed is 2800 rpm, refrigeration expansion valve opening is 5% to 40%, hot gas bypass expansion valve opening is 35% to 100%, and vapor injection enthalpy-increasing expansion valve opening is 15% to 20%.

[0075] In actual implementation, when △T ≥ the third threshold.

[0076] When the target temperature is within the (180, 250) temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 15%, circulating pump flow rate is 80% to 100% of rated flow rate, compressor speed is 2500 rpm to 4500 rpm, refrigeration expansion valve opening is 30% to 100%, hot gas bypass expansion valve opening is 0% to 30%, and jet enthalpy expansion valve opening is 0%.

[0077] When the target temperature is within the (80, 180) temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 15%, circulating pump flow rate is 60% to 80% of rated flow rate, compressor speed is 2500 rpm to 4500 rpm, refrigeration expansion valve opening is 30% to 100%, hot gas bypass expansion valve opening is 0% to 30%, and jet enthalpy expansion valve opening is 0%.

[0078] When the target temperature is within the (5,80] temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0%, circulating pump flow rate is 50% to 70% of rated flow rate, compressor speed is 2500 rpm to 4000 rpm, refrigeration expansion valve opening is 30% to 100%, hot gas bypass expansion valve opening is 0% to 20%, and jet enthalpy expansion valve opening is 0%.

[0079] When the target temperature is within the (-20, 5] temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0%, circulating pump flow rate is 40% to 60% of rated flow rate, compressor speed is 2700 rpm to 4000 rpm, refrigeration expansion valve opening is 40% to 80%, hot gas bypass expansion valve opening is 10% to 40%, and vapor injection enthalpy expansion valve opening is 0%.

[0080] When the target temperature is within the range of (-40, -20), the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0%, circulating pump flow rate is 30% to 50% of rated flow rate, compressor speed is 3000 rpm to 5000 rpm, refrigeration expansion valve opening is 50% to 90%, hot gas bypass expansion valve opening is 5% to 30%, and vapor injection enthalpy-increasing expansion valve opening is 25% to 40%.

[0081] In actual implementation, when -third threshold < ΔT < third threshold.

[0082] When the target temperature is within the (180, 250) temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 20% to 40%, circulating pump flow rate is 80% to 100% of rated flow rate, compressor speed is 0 rpm, refrigeration expansion valve opening is 0%, hot gas bypass expansion valve opening is 0%, and jet enthalpy expansion valve opening is 0%.

[0083] When the target temperature is within the (80, 180) temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 50% to 70%, circulating pump flow rate is 60% of rated flow rate, compressor speed is 0 rpm, refrigeration expansion valve opening is 0%, hot gas bypass expansion valve opening is 0%, and jet enthalpy expansion valve opening is 0%.

[0084] When the target temperature is within the (5,80] temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 30%, circulating pump flow rate is 60% of rated flow rate, compressor speed is 2000 rpm to 2500 rpm, refrigeration expansion valve opening is 0% to 30%, hot gas bypass expansion valve opening is 20% to 40%, and jet enthalpy expansion valve opening is 0%.

[0085] When the target temperature is within the (-20, 5] temperature range, the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0% to 15%, circulating pump flow rate is 50% of rated flow rate, compressor speed is 2400 rpm to 2700 rpm, refrigeration expansion valve opening is 20% to 40%, hot gas bypass expansion valve opening is 40% to 50%, and jet enthalpy expansion valve opening is 0%.

[0086] When the target temperature is within the range of (-40, -20), the adjustment range of the component parameters is as follows: solid-state relay duty cycle is 0%, circulating pump flow rate is 40% of rated flow rate, compressor speed is 2800rpm to 3000rpm, refrigeration expansion valve opening is 30% to 50%, hot gas bypass expansion valve opening is 30% to 40%, and vapor injection enthalpy-increasing expansion valve opening is 15% to 25%.

[0087] In summary, this embodiment improves the temperature control accuracy and response speed over a wide temperature range. When there is a temperature difference between the heat transfer fluid outlet temperature and the target temperature, the system adjusts the duty cycle of the solid-state relay of heater 21, the flow rate of the circulating pump, the compressor speed, and the opening of various expansion valves according to the relationship between ΔT and the preset temperature and the temperature zone to which the target temperature belongs. This achieves coordinated control of multiple actuators, avoiding response lag or energy waste caused by a single adjustment method. In addition, this embodiment uses a hierarchical and zoned control strategy, which allows the system to quickly approach the target temperature in different temperature zones, effectively suppressing overshoot and oscillation, meeting the temperature accuracy requirements of continuous chemical reactions, and improving energy efficiency ratio and operational stability. Specifically, when the outlet temperature and the target temperature are in different temperature zones, the temperature control error is [-1, 1]; when the outlet temperature and the target temperature are in the same temperature zone, the temperature control error is [-0.1, 0.1].

[0088] Example 3: Based on Example 1 or Example 2, this example discloses a control method for a subcritical carbon dioxide refrigeration and heating wide temperature range system.

[0089] In continuous chemical reactions, the temperature of load 4 often changes abruptly due to exothermic or endothermic reactions. For example, the temperature rises sharply when a strongly exothermic reaction starts, requiring rapid cooling to prevent the reaction from getting out of control. Therefore, the preset temperature in this embodiment includes a first threshold, a second threshold, and a third threshold. The first threshold is in the range [15, 30], the second threshold is in the range (5, 15), and the third threshold is in the range [1, 5].

[0090] In some embodiments, when the target temperature falls within the (180, 250) temperature range.

[0091] When ΔT < - first threshold, compressor 383 is turned off, the solid-state relay duty cycle is set to 100%, and the circulation pump flow rate is set to 100% of the rated flow rate.

[0092] When -first threshold < ΔT ≤ -second threshold, shut down compressor 383, set the solid-state relay duty cycle to 80% to 90%, and set the circulation pump flow rate to 90% of the rated flow rate.

[0093] When -second threshold < ΔT ≤ -third threshold, shut down compressor 383, set the solid-state relay duty cycle to 40% to 60%, and set the circulation pump flow rate to 80% of the rated flow rate.

[0094] When -third threshold < ΔT ≤ third threshold, shut down compressor 383, set the solid-state relay duty cycle to 20% to 40%, and the circulation pump flow rate to 80% to 90% of the rated flow rate.

[0095] When the third threshold < ΔT ≤ the second threshold, set the solid-state relay duty cycle to 10% to 15%, the circulating pump flow rate to 80% of the rated flow rate, the compressor speed to 2500 rpm to 3500 rpm, the refrigeration expansion valve opening to 30% to 40%, the hot gas bypass expansion valve opening to 0% to 30%, and the vapor injection enthalpy-increasing expansion valve opening to 0%.

[0096] When the second threshold < ΔT ≤ the first threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 80% of the rated flow rate, the compressor speed to 3500 rpm to 4000 rpm, the refrigeration expansion valve opening to 40% to 60%, the hot gas bypass expansion valve opening to 0%, and the vapor injection enthalpy-increasing expansion valve opening to 0%.

[0097] When △T > the first threshold, the solid-state relay duty cycle is set to 0%, the circulating pump flow rate is 80% of the rated flow rate, the compressor speed is 4000rpm to 4500rpm, the refrigeration expansion valve opening is 80% to 100%, the hot gas bypass expansion valve opening is 0%, and the vapor injection enthalpy expansion valve opening is 0%.

[0098] In some embodiments, when the target temperature falls within the (80, 180) temperature range.

[0099] When ΔT < - first threshold, shut down compressor 383, set the solid-state relay duty cycle to 80% to 90%, and set the circulation pump flow rate to 80% of the rated flow rate.

[0100] When -first threshold < ΔT ≤ -second threshold, shut down compressor 383, set the solid-state relay duty cycle to 60% to 80%, and set the circulation pump flow rate to 70% of the rated flow rate.

[0101] When -second threshold < ΔT ≤ -third threshold, shut down compressor 383, set the solid-state relay duty cycle to 50% to 70%, and set the circulation pump flow rate to 60% of the rated flow rate.

[0102] When - the third threshold < ΔT ≤ the third threshold, shut down compressor 383, set the solid-state relay duty cycle to 20% to 40%, and set the circulation pump flow rate to 70% of the rated flow rate.

[0103] When the third threshold < ΔT ≤ the second threshold, set the solid-state relay duty cycle to 10% to 15%, the circulating pump flow rate to 70% of the rated flow rate, the compressor speed to 2500 rpm to 3500 rpm, the refrigeration expansion valve opening to 30% to 60%, the hot gas bypass expansion valve opening to 15% to 30%, and the vapor injection enthalpy expansion valve opening to 0%.

[0104] When the second threshold < ΔT ≤ the first threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 70% of the rated flow rate, the compressor speed to 3500 rpm to 4000 rpm, the refrigeration expansion valve opening to 60% to 80%, the hot gas bypass expansion valve opening to 5% to 15%, and the vapor injection enthalpy expansion valve opening to 0%.

[0105] When △T > the first threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 70% of the rated flow rate, the compressor speed to 4000 rpm to 4500 rpm, the refrigeration expansion valve opening to 80% to 100%, the hot gas bypass expansion valve opening to 0% to 5%, and the vapor injection enthalpy-increasing expansion valve opening to 0%.

[0106] In some embodiments, when the target temperature falls within the (5,80) temperature range.

[0107] When ΔT < - first threshold, shut down compressor 383, set the solid-state relay duty cycle to 80% to 90%, and set the circulation pump flow rate to 70% of the rated flow rate.

[0108] When -first threshold < ΔT ≤ -second threshold, shut down compressor 383, set the solid-state relay duty cycle to 30% to 60%, and set the circulation pump flow rate to 60% of the rated flow rate.

[0109] When -second threshold < ΔT ≤ -third threshold, shut down compressor 383, set the solid-state relay duty cycle to 20% to 40%, and set the circulation pump flow rate to 50% of the rated flow rate.

[0110] When - the third threshold < ΔT ≤ the third threshold, set the solid-state relay duty cycle to 0% to 30%, the circulating pump flow rate to 60% of the rated flow rate, the compressor speed to 2000 rpm to 2500 rpm, the refrigeration expansion valve opening to 0% to 30%, and the hot gas bypass expansion valve opening to 20% to 40%.

[0111] When the third threshold < ΔT ≤ the second threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 60% of the rated flow rate, the compressor speed to 2500 rpm to 3000 rpm, the refrigeration expansion valve opening to 30% to 60%, the hot gas bypass expansion valve opening to 0% to 20%, and the vapor injection enthalpy expansion valve opening to 0%.

[0112] When the second threshold < ΔT ≤ the first threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 60% of the rated flow rate, the compressor speed to 3000 rpm to 3500 rpm, the refrigeration expansion valve opening to 60% to 80%, the hot gas bypass expansion valve opening to 0% to 15%, and the vapor injection enthalpy-increasing expansion valve opening to 0%.

[0113] When △T > the first threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 60% of the rated flow rate, the compressor speed to 3500rpm to 4000rpm, the refrigeration expansion valve opening to 80% to 100%, the hot gas bypass expansion valve opening to 0% to 5%, and the vapor injection enthalpy-increasing expansion valve opening to 0%.

[0114] In some embodiments, when the target temperature falls within the (-20, 5) temperature range.

[0115] When △T < - first threshold, set the solid-state relay duty cycle to 60% to 80%, the circulating pump flow rate to 60% of the rated flow rate, the compressor speed to 2400 rpm, the refrigeration expansion valve opening to 5% to 10%, and the hot gas bypass expansion valve opening to 80% to 100%.

[0116] When -first threshold < ΔT ≤ -second threshold, set the solid-state relay duty cycle to 30% to 60%, the circulating pump flow rate to 50% of the rated flow rate, the compressor speed to 2400 rpm, the refrigeration expansion valve opening to 10% to 20%, and the hot gas bypass expansion valve opening to 60% to 80%.

[0117] When -second threshold < ΔT ≤ -third threshold, set the solid-state relay duty cycle to 0% to 30%, the circulating pump flow rate to 40% of the rated flow rate, the compressor speed to 2400 rpm, the refrigeration expansion valve opening to 20% to 30%, and the hot gas bypass expansion valve opening to 45% to 50%.

[0118] When - the third threshold < ΔT ≤ the third threshold, set the solid-state relay duty cycle to 0% to 15%, the circulating pump flow rate to 50% of the rated flow rate, the compressor speed to 2400 rpm to 2700 rpm, the refrigeration expansion valve opening to 20% to 40%, and the hot gas bypass expansion valve opening to 40% to 50%.

[0119] When the third threshold < ΔT ≤ the second threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 50% of the rated flow rate, the compressor speed to 2700 rpm to 3000 rpm, the refrigeration expansion valve opening to 40% to 60%, the hot gas bypass expansion valve opening to 30% to 40%, and the vapor injection enthalpy expansion valve opening to 0%.

[0120] When the second threshold < ΔT ≤ the first threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 50% of the rated flow rate, the compressor speed to 3000 rpm to 3500 rpm, the refrigeration expansion valve opening to 60% to 70%, the hot gas bypass expansion valve opening to 20% to 30%, and the vapor injection enthalpy expansion valve opening to 0%.

[0121] When △T > the first threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 50% of the rated flow rate, the compressor speed to 3500rpm to 4000rpm, the refrigeration expansion valve opening to 70% to 80%, the hot gas bypass expansion valve opening to 10% to 15%, and the vapor injection enthalpy expansion valve opening to 0%.

[0122] In some embodiments, when the target temperature falls within the temperature range of (-40, -20).

[0123] When ΔT < - first threshold, set the solid-state relay duty cycle to 0% to 30%, the circulating pump flow rate to 50% of the rated flow rate, the compressor speed to 2800 rpm, the refrigeration expansion valve opening to 5% to 10%, and the hot gas bypass expansion valve opening to 80% to 100%.

[0124] When -first threshold < ΔT ≤ -second threshold, set the solid-state relay duty cycle to 0% to 30%, the circulating pump flow rate to 40% of the rated flow rate, the compressor speed to 2800 rpm, the refrigeration expansion valve opening to 10% to 20%, and the hot gas bypass expansion valve opening to 60% to 80%.

[0125] When -second threshold < ΔT ≤ -third threshold, set the solid-state relay duty cycle to 0% to 30%, the circulating pump flow rate to 30% of the rated flow rate, the compressor speed to 2800 rpm, the refrigeration expansion valve opening to 30% to 40%, the hot gas bypass expansion valve opening to 35% to 40%, and the vapor injection enthalpy-increasing expansion valve opening to 15% to 20%.

[0126] When - the third threshold < ΔT ≤ the third threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 40% of the rated flow rate, the compressor speed to 2800 rpm to 3000 rpm, the refrigeration expansion valve opening to 30% to 50%, the hot gas bypass expansion valve opening to 30% to 40%, and the vapor injection enthalpy expansion valve opening to 15% to 25%.

[0127] When the third threshold < ΔT ≤ the second threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 30% of the rated flow rate, the compressor speed to 3000 rpm to 3500 rpm, the refrigeration expansion valve opening to 50% to 70%, the hot gas bypass expansion valve opening to 20% to 30%, and the vapor injection enthalpy expansion valve opening to 25% to 35%.

[0128] When the second threshold < ΔT ≤ the first threshold, set the solid-state relay duty cycle to 0%, the circulating pump flow rate to 40% of the rated flow rate, the compressor speed to 3500 rpm to 4000 rpm, the refrigeration expansion valve opening to 70% to 80%, the hot gas bypass expansion valve opening to 10% to 20%, and the vapor injection enthalpy expansion valve opening to 30% to 40%.

[0129] When △T > the first threshold, the solid-state relay duty cycle is set to 0%, the circulating pump flow rate is 50% of the rated flow rate, the compressor speed is 4000 rpm to 5000 rpm, the refrigeration expansion valve opening is 80% to 90%, the hot gas bypass expansion valve opening is 5% to 10%, and the vapor injection enthalpy expansion valve opening is 30% to 40%.

[0130] In summary, this embodiment introduces a first threshold, a second threshold, and a third threshold as multi-level adjustment thresholds. It sets parameter combinations for the actuators for different temperature zones and temperature difference ranges, enabling multi-level adjustment. This avoids frequent and large fluctuations in the actuators, improving the smoothness and rapid response of the temperature control process. It is particularly suitable for multi-stage, multi-rate temperature control requirements in continuous chemical reactions, ensuring the stability of the reaction process and the consistency of the products. For example, when the temperature difference exceeds the first threshold, the system will rapidly cool or heat up at maximum capacity; when the temperature difference falls back to within the third threshold, it achieves stable control, thereby making the average temperature control error across the entire temperature range [-0.3, 0.3].

[0131] Example 4: Based on any one of Examples 1 to 3, this example introduces a control method for a subcritical carbon dioxide refrigeration and heating wide temperature range system.

[0132] In continuous chemical reactions, many processes such as esterification, hydrolysis, and crystallization require prolonged exposure to constant temperatures. Temperature fluctuations directly impact reaction rates and equilibrium, consequently affecting product yield and purity. Existing isothermal control methods largely rely on single feedback regulation. When the load (heat load) changes, such as fluctuations in the intensity of exothermic reactions, the regulatory response lags, making it difficult to maintain high-precision isothermal control over extended periods. Especially in low-temperature isothermal scenarios, such as below -20°C, carbon dioxide refrigeration systems suffer from even worse isothermal stability due to factors like difficulties in oil return and fluctuations in evaporation pressure, limiting their application in fine chemicals, biopharmaceuticals, and other fields.

[0133] When the outlet temperature approaches the target temperature, and it is necessary to keep the load 4 in a constant temperature environment, the control method of this embodiment includes (A) to (C).

[0134] (A) When the target temperature is within the (80, 250) temperature range: Based on the real-time temperature difference between the real-time outlet temperature and the target temperature, adjust the duty cycle of the solid-state relay in heater 21 and / or the flow rate of the circulating pump to make the real-time outlet temperature approach the target temperature. For example, when the real-time outlet temperature is greater than the target temperature, decrease the duty cycle of the solid-state relay in heater 21; when the real-time outlet temperature is less than the target temperature, increase the duty cycle of the solid-state relay in heater 21.

[0135] (B) When the target temperature is in the (5,80] temperature range: Based on the real-time temperature difference between the real-time outlet temperature and the target temperature, adjust the duty cycle of the solid-state relay in heater 21, the flow rate of the circulating pump, the compressor speed, and / or the opening of the expansion valve to make the real-time outlet temperature approach the target temperature. For example, when the real-time outlet temperature is greater than the target temperature, increase the compressor speed; when the real-time outlet temperature is less than the target temperature, decrease the compressor speed.

[0136] (C) When the target temperature is in the (-40, 5] temperature range: Adjust the circulation pump flow rate, compressor speed and / or expansion valve opening according to the real-time temperature difference between the real-time outlet temperature and the target temperature to make the real-time outlet temperature approach the target temperature. For example, when the real-time outlet temperature is greater than the target temperature, increase the opening of the refrigeration expansion valve; when the real-time outlet temperature is less than the target temperature, decrease the opening of the refrigeration expansion valve.

[0137] In some embodiments, when the target temperature is in the range of (-20, 80) degrees Celsius, the expansion valve includes a refrigeration expansion valve 387 and / or a hot gas bypass expansion valve 388. When the target temperature is in the range of (-40, -20) degrees Celsius, the expansion valve includes a refrigeration expansion valve 387, a hot gas bypass expansion valve 388, and / or a vapor injection enthalpy-increasing expansion valve 389.

[0138] In summary, this embodiment addresses the control requirements after load 4 enters the isothermal stage. Based on the target temperature zone, a differentiated adjustment strategy is adopted: in the (80, 250] temperature zone, the duty cycle of heater 21 and the flow rate of the circulating pump are mainly adjusted to avoid frequent start-stop cycles of the refrigeration circuit; in the (5, 80] temperature zone, heater 21, compressor 383, and expansion valve are jointly adjusted to balance heat and cold; in the (-40, 5] temperature zone, the compressor 383 and expansion valve are the primary focus of adjustment. Furthermore, the introduction of a vapor injection enthalpy-increasing expansion valve 389 improves low-temperature oil return and circulation efficiency. Through zoned mode isothermal control, the system can control temperature fluctuations within ±0.1℃ during long-term operation, meeting the precision requirements of continuous chemical reactions for an isothermal environment and improving product stability and process repeatability.

[0139] Example 5: Based on any one of Examples 1 to 4, this example introduces a control method for a subcritical carbon dioxide refrigeration and heating wide-temperature-range system.

[0140] Some continuous chemical reactions require uniform heating or cooling at a specific rate. For example, in temperature-programmed desorption (TPD) analysis or temperature-controlled crystallization, excessively rapid heating may lead to product structural defects, while excessively slow cooling will affect production efficiency. Existing temperature control systems often employ simple timed adjustment or PID tracking to achieve uniform temperature changes, which struggles to consider the thermodynamic characteristics of different temperature zones and the nonlinear response of the actuators. This results in the actual temperature change rate deviating from the preset value, affecting product quality. Especially when uniform cooling is required in the (180, 250] temperature zone, precise rate control cannot be achieved by relying solely on natural cooling or single refrigeration adjustment; and when uniform heating is required in the (-40, -20] temperature zone, rate fluctuations may occur due to thermal inertia when relying solely on heater 21 for adjustment.

[0141] In some embodiments, when the outlet temperature and the target temperature are in the same temperature range, and the load 4 needs to be heated at a preset heating rate, the control method of the subcritical carbon dioxide refrigeration and heating wide temperature range system includes: setting the compressor speed to 0, the expansion valve opening to 0, and adjusting the duty cycle of the solid-state relay and / or the circulation pump flow rate so that the real-time outlet temperature approaches the target temperature at a preset heating rate.

[0142] Specifically, first adjust the duty cycle of the solid-state relay, then adjust the flow rate of the circulating pump.

[0143] When the solid-state relay duty cycle is less than 100% and the actual heating rate is less than the preset heating rate, increase the solid-state relay duty cycle; when the solid-state relay duty cycle is 100% and the actual heating rate is less than the preset heating rate, decrease the circulation pump flow rate; when the solid-state relay duty cycle is greater than 0% and the actual heating rate is greater than the preset heating rate, decrease the solid-state relay duty cycle; when the solid-state relay duty cycle is 0% and the actual heating rate is greater than the preset heating rate, increase the circulation pump flow rate. The preset heating rate is between 5℃ / min and 15℃ / min.

[0144] In some embodiments, when the outlet temperature and the target temperature are in the same temperature range, and the load 4 needs to be cooled at a preset cooling rate, the control method of the subcritical carbon dioxide refrigeration and heating wide temperature range system includes: setting the duty cycle of the solid-state relay to 0, and adjusting the circulation pump flow rate, compressor speed and / or expansion valve opening, so that the real-time outlet temperature approaches the target temperature at a preset cooling rate.

[0145] (1) When both the outlet temperature and the target temperature are in the (80, 250) temperature range, the circulation pump flow rate should be adjusted first, and then the refrigeration circuit should be adjusted.

[0146] In application, when 30% of the rated flow rate ≤ circulating pump flow rate < 100% of the rated flow rate, and the real-time cooling rate < the preset cooling rate, increase the circulating pump flow rate; when the circulating pump flow rate = 100% of the rated flow rate, and the real-time cooling rate < the preset cooling rate, increase the compressor speed, decrease the opening of the hot gas bypass expansion valve, and / or increase the opening of the refrigeration expansion valve; when 30% of the rated flow rate < circulating pump flow rate ≤ 100% of the rated flow rate, and the real-time cooling rate > the preset cooling rate, decrease the circulating pump flow rate; when the circulating pump flow rate = 30% of the rated flow rate, and the real-time cooling rate > the preset cooling rate, decrease the compressor speed, increase the opening of the hot gas bypass expansion valve, and / or decrease the opening of the refrigeration expansion valve. The preset cooling rate is 5℃ / min to 15℃ / min.

[0147] In practical applications, when 30% of the rated flow rate ≤ the circulating pump flow rate < 100% of the rated flow rate, and the real-time cooling rate < the preset cooling rate, the circulating pump flow rate is increased according to |△V|; when the circulating pump flow rate = 100% of the rated flow rate, and the real-time cooling rate < the preset cooling rate, the compressor speed is increased, the hot gas bypass expansion valve opening is decreased, and / or the refrigeration expansion valve opening is increased according to |△V|; when 30% of the rated flow rate < the circulating pump flow rate ≤ 100% of the rated flow rate, and the real-time cooling rate > the preset cooling rate, the circulating pump flow rate is decreased according to |△V|; when the circulating pump flow rate = 30% of the rated flow rate, and the real-time cooling rate > the preset cooling rate, the compressor speed is decreased, the hot gas bypass expansion valve opening is increased, and / or the refrigeration expansion valve opening is decreased according to |△V|.

[0148] Where |△V| is the absolute value of the difference between the real-time cooling rate and the preset cooling rate.

[0149] (2) When the target temperature is in the (-20, 80) temperature range, the compressor speed and the opening of the refrigeration expansion valve should be adjusted first, and then the opening of the hot gas bypass expansion valve should be adjusted.

[0150] In application, when the real-time cooling rate is less than the preset cooling rate, increase the compressor speed and / or increase the opening of the refrigeration expansion valve; when both the compressor speed and the refrigeration expansion valve opening are at the upper limit of the current temperature zone configuration, and the real-time cooling rate is less than the preset cooling rate, decrease the opening of the hot gas bypass expansion valve; when the real-time cooling rate is greater than the preset cooling rate, decrease the compressor speed and / or decrease the opening of the refrigeration expansion valve; when both the compressor speed and the refrigeration expansion valve opening are at the lower limit of the current temperature zone configuration, and the real-time cooling rate is greater than the preset cooling rate, increase the opening of the hot gas bypass expansion valve.

[0151] In practical applications, when the real-time cooling rate is less than the preset cooling rate, the compressor speed and / or the opening of the refrigeration expansion valve are increased according to |△V|; when both the compressor speed and the opening of the refrigeration expansion valve are at the upper limit of the current temperature zone configuration, and the real-time cooling rate is less than the preset cooling rate, the opening of the hot gas bypass expansion valve is decreased according to |△V|; when the real-time cooling rate is greater than the preset cooling rate, the compressor speed and / or the opening of the refrigeration expansion valve are decreased according to |△V|; when both the compressor speed and the opening of the refrigeration expansion valve are at the lower limit of the current temperature zone configuration, and the real-time cooling rate is greater than the preset cooling rate, the opening of the hot gas bypass expansion valve is increased according to |△V|.

[0152] In actual implementation, the lower limit of the compressor speed configured in the (-20,5] temperature zone is 2400 rpm, and the upper limit of the compressor speed configured in the (-20,5] temperature zone is 4000 rpm; the lower limit of the opening degree of the refrigeration expansion valve configured in the (-20,5] temperature zone is 5%, and the upper limit of the opening degree of the refrigeration expansion valve configured in the (-20,5] temperature zone is 80%.

[0153] (5,80) The lower limit of the compressor speed configured in the temperature zone is 2000 rpm, and the upper limit of the compressor speed configured in the temperature zone is 4000 rpm; (5,80) The lower limit of the opening of the refrigeration expansion valve configured in the temperature zone is 0%, and the upper limit of the opening of the refrigeration expansion valve configured in the temperature zone is 100%.

[0154] (3) When the target temperature is in the (-40, -20) temperature range, the opening of the refrigeration expansion valve and the opening of the jet enthalpy expansion valve should be adjusted first, and then the opening of the hot gas bypass expansion valve should be adjusted.

[0155] In application, when the real-time cooling rate is less than the preset cooling rate, increase the opening of the refrigeration expansion valve and / or increase the opening of the vapor injection enthalpy-increasing expansion valve; when both the opening of the refrigeration expansion valve and the opening of the vapor injection enthalpy-increasing expansion valve are at the upper limit of the current temperature zone configuration, and the real-time cooling rate is less than the preset cooling rate, decrease the opening of the hot gas bypass expansion valve; when the real-time cooling rate is greater than the preset cooling rate, decrease the opening of the refrigeration expansion valve and / or decrease the opening of the vapor injection enthalpy-increasing expansion valve; when both the opening of the refrigeration expansion valve and the opening of the vapor injection enthalpy-increasing expansion valve are at the lower limit of the current temperature zone configuration, and the real-time cooling rate is greater than the preset cooling rate, increase the opening of the hot gas bypass expansion valve.

[0156] In practical applications, when the real-time cooling rate is less than the preset cooling rate, the opening of the refrigeration expansion valve and / or the opening of the vapor injection enthalpy-increasing expansion valve are increased according to |△V|; when both the opening of the refrigeration expansion valve and the opening of the vapor injection enthalpy-increasing expansion valve are the upper limits configured for the current temperature zone, and the real-time cooling rate is less than the preset cooling rate, the opening of the hot gas bypass expansion valve is decreased according to |△V|; when the real-time cooling rate is greater than the preset cooling rate, the opening of the refrigeration expansion valve and / or the opening of the vapor injection enthalpy-increasing expansion valve are decreased according to |△V|; when both the opening of the refrigeration expansion valve and the opening of the vapor injection enthalpy-increasing expansion valve are the lower limits configured for the current temperature zone, and the real-time cooling rate is greater than the preset cooling rate, the opening of the hot gas bypass expansion valve is increased according to |△V|.

[0157] In actual implementation, the lower limit of the opening degree of the refrigeration expansion valve configured in the (-40, -20] temperature zone is 5%, and the upper limit of the opening degree of the refrigeration expansion valve is 90%; the lower limit of the opening degree of the vapor injection enthalpy-increasing expansion valve configured in the (-40, -20] temperature zone is 0%, and the upper limit of the opening degree of the vapor injection enthalpy-increasing expansion valve configured in the (-40, -20] temperature zone is 40%.

[0158] In summary, this embodiment proposes a rate tracking control strategy based on temperature zones and priorities for both uniform heating and cooling scenarios. In uniform heating mode, the duty cycle of the solid-state relay in heater 21 is adjusted first. When the duty cycle reaches its upper limit and still cannot meet the heating rate, the circulation pump flow rate is reduced to decrease heat capacity and increase the heating rate. In uniform cooling mode, a differentiated adjustment sequence is established according to the temperature zone of the target temperature: the circulation pump flow rate is adjusted first in the (80, 250) temperature zone; the compressor speed and refrigeration expansion valve opening are adjusted first in the (-20, 80) temperature zone; and the refrigeration expansion valve opening and vapor injection enthalpy expansion valve opening are adjusted first in the (-40, -20) temperature zone. A hot gas bypass expansion valve 388 is introduced as an auxiliary measure when each adjustment method reaches its limit. Through zoned priority adjustment, the heating and cooling rates can be controlled across the entire temperature range with a rate deviation of ±5%, meeting the process requirements of continuous chemical reactions for programmed temperature control and improving the repeatability of the reaction and the consistency of the products.

[0159] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A subcritical carbon dioxide refrigeration and heating system with a wide temperature range, characterized in that, include: A circulation loop is provided, which is filled with heat-conducting fluid. A circulation pump is provided on the circulation loop to circulate and deliver the heat-conducting fluid with controllable temperature to the load for heating or cooling. A heating circuit is connected to the circulation circuit for heat exchange; the heating circuit includes a heater for providing an adjustable amount of heat to the heat-conducting fluid in the circulation circuit. A refrigeration circuit, which uses carbon dioxide as a refrigerant and is connected to the circulation circuit for heat exchange, is used to provide an adjustable cooling capacity for the heat transfer fluid in the circulation circuit. The refrigeration circuit includes a compressor, a cooler, a refrigeration expansion valve, and an evaporator connected in sequence, and the first side heat exchange channel of the evaporator is connected to the circulation circuit.

2. The subcritical carbon dioxide refrigeration and heating wide-temperature-range system according to claim 1, characterized in that, The refrigeration circuit also includes sequentially connected components to form the circuit: The first refrigeration branch is connected to the second side heat exchange channel of the evaporator to exchange heat with the circulation loop; The second refrigeration branch has its input end connected to the output end of the first refrigeration branch, and its output end connected to the compressor. The third refrigeration branch has its input end connected to the compressor and its output end connected to the dryer filter; the third refrigeration branch is connected to the first side heat exchange channel of the cooler, and the second side heat exchange channel of the cooler is connected to the cooling circuit, which is used to cool the carbon dioxide in the third refrigeration branch. The fourth refrigeration branch has its input end connected to the dryer filter and its output end connected to the refrigeration expansion valve. The fifth refrigeration branch has its input end connected to the refrigeration expansion valve and its output end connected to the input end of the first refrigeration branch.

3. The subcritical carbon dioxide refrigeration and heating wide-temperature-range system according to claim 2, characterized in that, The refrigeration circuit also includes: The sixth refrigeration branch is equipped with a hot gas bypass expansion valve; the input end of the sixth refrigeration branch is connected to the input end of the third refrigeration branch, and the output end of the sixth refrigeration branch is connected to the input end of the first refrigeration branch. The seventh refrigeration branch is equipped with a jet enthalpy-increasing expansion valve; the input end of the seventh refrigeration branch is connected to the output end of the fourth refrigeration branch, and the output end of the seventh refrigeration branch is connected to the gas injection port of the compressor. An economizer, wherein the first heat exchange channel of the economizer is connected to the seventh refrigeration branch, and the second heat exchange channel of the economizer is connected to the fourth refrigeration branch; A regenerator, wherein the first heat exchange channel of the regenerator is connected to the second refrigeration branch, and the second heat exchange channel of the regenerator is connected to the fifth refrigeration branch.

4. The subcritical carbon dioxide refrigeration and heating wide-temperature-range system according to claim 2, characterized in that, The loop includes: The first circulation branch has its input end connected to a liquid storage unit containing heat-conducting liquid; the upstream end of the first circulation branch is connected to the circulation pump, and the downstream end of the first circulation branch is connected to the heater. The second circulation branch has its input end connected to the output end of the first circulation branch; the second circulation branch is connected to the load and is used to provide cooling or heating to the load. The third circulation branch has its input end connected to the output end of the second circulation branch, and its output end connected to the liquid storage unit; the third circulation branch is connected to the first side heat exchange channel of the evaporator to exchange heat with the first refrigeration branch.

5. The subcritical carbon dioxide refrigeration and heating wide-temperature-range system according to claim 4, characterized in that, The liquid storage unit includes: A gas-liquid separator has a liquid outlet at its bottom, which is connected to the input end of the first circulation branch; a liquid inlet on its first side, which is connected to the output end of the third circulation branch; an exhaust port at its top; and a compensation port on its second side. An expansion tank is provided, with a filling port at the top for adding heat-conducting fluid; an air inlet at the top of the expansion tank is connected to the exhaust port; and a replenishment port at the bottom of the expansion tank is connected to the compensation port.

6. A control method for a subcritical carbon dioxide refrigeration and heating wide-temperature-range system as described in any one of claims 1 to 5, characterized in that, include: Based on the relationship between the temperature difference between the outlet temperature and the target temperature and the preset temperature, as well as the target temperature, adjust the duty cycle of the solid-state relay, the flow rate of the circulating pump, the speed of the compressor, and / or the opening of the expansion valve to make the outlet temperature approach the target temperature. The target temperature is within the range of (-40, 250); the expansion valve includes a refrigeration expansion valve, a hot gas bypass expansion valve, and / or a jet enthalpy-increasing expansion valve; the outlet temperature is the temperature of the heat transfer fluid before it flows through the load.

7. The control method for a subcritical carbon dioxide refrigeration and heating wide-temperature-range system according to claim 6, characterized in that, The step of bringing the outlet temperature close to the target temperature includes: When △T ≥ the third threshold: Set the compressor speed, refrigeration expansion valve opening, and hot gas bypass expansion valve opening according to the target temperature; when the target temperature is in the (180, 250] temperature range or the (80, 180] temperature range, set the heating circuit to low power mode; when the target temperature is in the (5, 80] temperature range or the (-20, 5] temperature range or the (-40, -20] temperature range, turn off the heater; when the target temperature is in the (-40, -20] temperature range, set the vapor injection enthalpy expansion valve opening according to the target temperature. When -third threshold < ΔT < third threshold: When the target temperature is in the (180, 250] temperature range or the (80, 180] temperature range: turn off the compressor; set the solid-state relay duty cycle and / or circulation pump flow rate according to the target temperature; When the target temperature is in the (5,80] temperature range or the (-20,5] temperature range: set the heating circuit to low power mode; set the compressor speed, refrigeration expansion valve opening and hot gas bypass expansion valve opening according to the target temperature; When the target temperature is in the range of (-40, -20): turn off the heater; set the compressor speed, refrigeration expansion valve opening, hot gas bypass expansion valve opening, and jet enthalpy expansion valve opening according to the target temperature; When ΔT ≤ -third threshold: When the target temperature falls within the (180, 250] temperature range, or the (80, 180] temperature range, or the (5, 80] temperature range: shut down the compressor; set the solid-state relay duty cycle and / or the circulation pump flow rate according to the target temperature; When the target temperature is in the (-20, 5) temperature range: set the cooling circuit to low power mode; set the solid-state relay duty cycle and / or circulation pump flow rate according to the target temperature; When the target temperature is in the range of (-40, -20): set the heating circuit to low power and the compressor speed to low speed; set the opening of the refrigeration expansion valve, the hot gas bypass expansion valve, and the vapor injection enthalpy expansion valve according to the target temperature. Wherein, △T = outlet temperature - target temperature; the third threshold belongs to [1,5]; the low power state of the heating circuit includes: solid-state relay duty cycle of 0% to 40%; the low power state of the refrigeration circuit includes: compressor speed of 0 rpm to 2400 rpm, refrigeration expansion valve opening of 0% to 30%, vapor injection enthalpy expansion valve opening of 0%, hot gas bypass expansion valve opening of 40% to 100%; low speed of 2000 rpm to 2800 rpm.

8. The control method for a subcritical carbon dioxide refrigeration and heating wide-temperature-range system according to claim 6, characterized in that, When the outlet temperature approaches the target temperature, it is necessary to keep the load in a constant temperature environment: When the target temperature is within the (80, 250) temperature range: adjust the duty cycle of the solid-state relay in the heater and / or the flow rate of the circulating pump according to the real-time temperature difference between the real-time outlet temperature and the target temperature, so that the real-time outlet temperature approaches the target temperature. When the target temperature is in the (5,80) temperature range: adjust the duty cycle of the solid-state relay in the heater, the flow rate of the circulating pump, the speed of the compressor and / or the opening of the expansion valve according to the real-time temperature difference between the real-time outlet temperature and the target temperature, so that the real-time outlet temperature approaches the target temperature. When the target temperature is in the (-40, 5] temperature range: adjust the circulation pump flow rate, compressor speed and / or expansion valve opening according to the real-time temperature difference between the real-time outlet temperature and the target temperature, so that the real-time outlet temperature approaches the target temperature. Specifically, when the target temperature is in the range of (-20, 80), the expansion valve includes a refrigeration expansion valve and / or a hot gas bypass expansion valve; when the target temperature is in the range of (-40, -20), the expansion valve includes a refrigeration expansion valve, a hot gas bypass expansion valve, and / or a vapor injection enthalpy-increasing expansion valve.

9. The control method for a subcritical carbon dioxide refrigeration and heating wide-temperature-range system according to claim 6, characterized in that, When the outlet temperature and the target temperature are in the same temperature range, and the load needs to be heated uniformly at a preset heating rate: set the compressor speed to 0, the expansion valve opening to 0, and adjust the duty cycle of the solid-state relay and / or the circulation pump flow rate to make the real-time outlet temperature approach the target temperature at the preset heating rate. When the duty cycle of the solid-state relay is less than 100% and the actual heating rate is less than the preset heating rate, increase the duty cycle of the solid-state relay. When the solid-state relay duty cycle is 100% and the actual heating rate is less than the preset heating rate, reduce the circulation pump flow rate; When the duty cycle of the solid-state relay is greater than 0% and the actual heating rate is greater than the preset heating rate, reduce the duty cycle of the solid-state relay. When the solid-state relay duty cycle is 0% and the actual heating rate is greater than the preset heating rate, increase the circulation pump flow rate.

10. The control method for a subcritical carbon dioxide refrigeration and heating wide-temperature-range system according to claim 6, characterized in that, When the outlet temperature and the target temperature are in the same temperature range, and the load needs to be cooled uniformly at a preset cooling rate: Set the solid-state relay duty cycle to 0, and adjust the circulating pump flow rate, compressor speed, and / or expansion valve opening to make the real-time outlet temperature approach the target temperature at the preset cooling rate. When both the outlet temperature and the target temperature fall within the (80, 250) temperature range: When 0 ≤ circulating pump flow rate < rated flow rate and real-time cooling rate < preset cooling rate, increase the circulating pump flow rate; When the circulating pump flow rate equals the rated flow rate and the real-time cooling rate is less than the preset cooling rate, increase the compressor speed, reduce the opening of the hot gas bypass expansion valve, and / or increase the opening of the refrigeration expansion valve. When 0 < circulating pump flow rate ≤ rated flow rate, and real-time cooling rate > preset cooling rate, reduce the circulating pump flow rate; When the circulation pump flow rate is 0 and the real-time cooling rate is greater than the preset cooling rate, reduce the compressor speed, increase the opening of the hot gas bypass expansion valve and / or reduce the opening of the refrigeration expansion valve. When the target temperature falls within the temperature range of (-20, 80): When the real-time cooling rate is less than the preset cooling rate, increase the compressor speed and / or increase the opening of the refrigeration expansion valve; When the compressor speed and the opening of the refrigeration expansion valve are both at the upper limit of the current temperature zone configuration, and the real-time cooling rate is less than the preset cooling rate, reduce the opening of the hot gas bypass expansion valve. When the real-time cooling rate is greater than the preset cooling rate, reduce the compressor speed and / or reduce the opening of the refrigeration expansion valve; When the compressor speed and the opening of the refrigeration expansion valve are both at the lower limit of the current temperature zone configuration, and the real-time cooling rate is greater than the preset cooling rate, increase the opening of the hot gas bypass expansion valve. When the target temperature falls within the temperature range of (-40, -20): When the real-time cooling rate is less than the preset cooling rate, increase the opening of the refrigeration expansion valve and / or increase the opening of the vapor injection enthalpy expansion valve; When both the opening of the refrigeration expansion valve and the opening of the vapor injection enthalpy-increasing expansion valve are at the upper limit of the current temperature zone configuration, and the real-time cooling rate is less than the preset cooling rate, reduce the opening of the hot gas bypass expansion valve. When the real-time cooling rate is greater than the preset cooling rate, reduce the opening of the refrigeration expansion valve and / or reduce the opening of the vapor injection enthalpy expansion valve; When both the opening degree of the refrigeration expansion valve and the opening degree of the vapor injection enthalpy-increasing expansion valve are at the lower limit of the current temperature zone configuration, and the real-time cooling rate is greater than the preset cooling rate, the opening degree of the hot gas bypass expansion valve is increased.

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