Vehicle-mounted liquid cooling source cascade refrigeration unit and control method thereof

Abstract

The application discloses a vehicle-mounted liquid cooling source cascade refrigeration unit, which comprises a compression refrigeration cycle, a fluorine pump cycle and a cooling liquid cycle, wherein the fluorine pump cycle comprises a four-way reversing valve, a first heat exchanger and a second heat exchanger; the condenser of the compression refrigeration cycle and the first heat exchanger of the fluorine pump adopt a cascade structure, and cooling liquid in the cooling liquid cycle is sequentially cooled by the second heat exchanger and the evaporator of the compression refrigeration cycle. The application further provides a control method of the vehicle-mounted liquid cooling source cascade refrigeration unit. The application is suitable for vehicle-mounted use, and the refrigeration capacity of the refrigeration unit can meet the rapid switching of the instantaneous variation of the heat generating equipment from zero load to maximum load.

Description

Technical Field

[0001] This invention relates to the field of refrigeration technology, and in particular to a full-temperature-range vehicle-mounted liquid-cooled cascade refrigeration unit and its control method. Background Technology

[0002] Various electronic devices require liquid cooling sources to provide coolant that meets the temperature, flow rate, and pressure requirements for the thermal load of electronic devices. Liquid cooling sources for high-power electronic devices such as computer rooms, base stations, and radars typically use a combination of compressor refrigeration and natural cooling fluid circulation to provide the required coolant. Ground-based liquid cooling sources are not limited by space and weight, while vehicle-mounted liquid cooling sources are limited by the vehicle's conditions in terms of space and weight. With the development of the electronics industry, the thermal load of electronic devices is getting higher and higher. Therefore, reducing the size and weight of vehicle-mounted liquid cooling units and increasing cooling capacity under the limited vehicle space and weight conditions is an important issue.

[0003] Vehicle-mounted liquid cooling sources provide sufficient coolant for high-power transmitting electronic devices such as radar and base stations. These loads experience significant instantaneous power fluctuations, switching rapidly from startup to full power operation. Correspondingly, the liquid cooling source must respond quickly to these changes and rapidly reach the target cooling capacity. At normal temperatures, compressor cooling can quickly establish a pressure difference for rapid startup. However, at low temperatures, the condensation temperature is low, and the pressure difference build-up is slow. A single coolant air-cooling cycle cannot support the heat dissipation requirements of the radar's thermal load. Furthermore, coolant air-cooling systems are bulky and heavy, occupying valuable space and weight within the limited space of the vehicle environment.

[0004] Chinese patent CN222053670U discloses a liquid cooling source module and liquid cooling source equipment, which uses compressor refrigeration and coolant air cooling for heat dissipation. It adds an independent second heat exchanger for coolant heat dissipation. The coolant is an ethylene glycol aqueous solution, which dissipates heat through circulation with the natural environment at low temperatures. This technical solution increases the weight of the coolant and the corresponding second heat exchanger in the vehicle environment, and cannot meet the requirements of vehicle use.

[0005] Chinese patent CN113883736B discloses a radiator control device and control method for a mobile liquid cooling source. It adopts compressor refrigeration and coolant air cooling. The second heat exchanger for air cooling is integrated with the first heat exchanger for compressor refrigeration. In the vehicle environment, although it enhances compactness, it still increases the circulating weight of the coolant. At the same time, because the heat exchanger is integrated, the coolant has a certain corrosiveness to the tube fin radiator, reducing its lifespan.

[0006] Chinese patent CN119408381A discloses a variable structure vehicle cooling module group, which also uses compressor refrigeration and conventional coolant air cooling. Through structural optimization, the heat exchanger area is increased to improve the heat exchange capacity under limited vehicle conditions. However, it is also inevitable that the coolant will corrode the tube fin radiator and increase the weight of the coolant.

[0007] Chinese patent CN221611616U discloses a refrigeration composite system of a fluorine pump and a compressor, which uses a compressor refrigeration system and a fluorine pump cooling system connected in series. The two systems share the same refrigerant. When only the fluorine pump cooling system or the compressor refrigeration system is running, the refrigerant flow resistance of the system increases, which reduces the refrigeration efficiency. Because of the reduced efficiency, the size and weight need to be increased to achieve the target cooling capacity, which cannot meet the size and weight requirements of the vehicle environment.

[0008] In summary, the existing technologies mentioned above all have shortcomings when used in vehicles, and there are no corresponding measures for load response speed. Therefore, designing a liquid-cooled refrigeration unit that is suitable for vehicle use, has a fast switching speed, and can meet the instantaneous load changes is a technical problem that urgently needs to be solved in the industry. Summary of the Invention

[0009] This invention provides a vehicle-mounted liquid-cooled cascade refrigeration unit and its control method to solve the technical problem in the prior art where the cooling capacity of the refrigeration unit cannot quickly switch between the maximum and minimum values ​​under limited vehicle space and weight conditions.

[0010] The technical solution adopted in this invention is to design an on-board liquid-cooled cascade refrigeration unit, including a compression refrigeration cycle, a refrigerant pump cycle, and a coolant cycle. The refrigerant pump cycle includes a four-way reversing valve, a first heat exchanger, and a second heat exchanger. The condenser of the compression refrigeration cycle and the first heat exchanger of the refrigerant pump adopt a cascade structure. The coolant in the coolant cycle is cooled by passing through the second heat exchanger and the evaporator of the compression refrigeration cycle in sequence.

[0011] Furthermore, the compression refrigeration cycle includes a compressor, a condenser, a first expansion valve, an evaporator, and a first gas-liquid separator connected in sequence by pipelines.

[0012] Furthermore, the fluorine pump cycle includes a fluorine pump, a four-way reversing valve, a first heat exchanger, a second throttle valve, a liquid storage tank, a third throttle valve, a second heat exchanger, and a second gas-liquid separator, which are connected in sequence through pipelines.

[0013] Furthermore, the refrigerant inlet and outlet of the second heat exchanger are connected in parallel with a bypass, and a bypass valve is provided on the bypass, with one-way valves provided on both sides of the bypass valve.

[0014] Preferably, temperature sensors are arranged on the condenser, the first heat exchanger, the liquid supply pipe and the liquid return pipe of the coolant circulation respectively.

[0015] The present invention further proposes a control method for the above vehicle-mounted liquid cold source cascade refrigeration unit, wherein the control method sets four ambient temperature parameters as control nodes, refers to three condensing temperature set values, and selects the operation mode of the vehicle-mounted liquid cold source cascade refrigeration unit according to the intervals where the ambient temperature and the condensing temperature lie, comprising: a compressor cooling mode, a fluorine pump cooling mode, a hybrid cooling mode, a reverse hedging mode, an operation mode with fluorine pump circulation as the main part and compressor refrigeration as the auxiliary part, and an operation mode with compressor refrigeration as the main part and fluorine pump circulation as the auxiliary part.

[0016] When the ambient temperature is greater than or equal to the second set value, T_ambient ≥ T2, the compressor circulation is turned on, and then the following steps are executed: When the ambient temperature is greater than or equal to the first set value and the condenser temperature is greater than or equal to the first threshold, T_ambient ≥ T1 and T_cond ≥ Ta, the fluorine pump circulation is started, meanwhile the four-way reversing valve is reversed to operate the reverse hedging mode to cool down the condenser; when the condenser temperature is less than or equal to the difference between the first threshold and the first temperature fluctuation difference, T_cond ≤ Ta-T_diff1, the fluorine pump circulation is turned off; When the ambient temperature is greater than or equal to the second set value and less than or equal to the first set value, T2 ≤ T_ambient ≤ T1, the compressor cooling mode is maintained.

[0017] When the ambient temperature is greater than the fourth set temperature and less than the second set temperature, T4<T_ambient<T2, the following steps are executed: The fluorine pump circulation is started first, and after operating for a preset time t, the ambient temperature is detected again. When the ambient temperature is greater than or equal to the third set value and less than the second set value, T3 ≤ T_ambient < T2, the operation mode with compressor refrigeration as the main part and fluorine pump circulation as the auxiliary part is entered; when the ambient temperature is greater than the fourth set value and less than or equal to the third set value, T4<T_ambient ≤ T3, the operation mode with fluorine pump circulation as the main part and compressor refrigeration as the auxiliary part is entered.

[0018] After entering the operation state with compressor refrigeration as the main part and fluorine pump circulation as the auxiliary part, the following steps are executed: The compressor circulation is turned on, the condenser temperature is detected. When the condenser temperature is greater than or equal to the second threshold, T_cond ≥ Tb, the fluorine pump circulation is turned off; when the condenser temperature is less than or equal to the difference between the second threshold and the second temperature fluctuation difference, T_cond ≤ Tb-T_diff2, the fluorine pump circulation is turned on, the four-way reversing valve is reversed, and the reverse hedging mode is entered.

[0019] After entering the operation state with the fluorine pump as the main part and compressor refrigeration as the auxiliary part, the following steps are executed: Start the refrigerant pump cycle and monitor the condenser temperature. When the condenser temperature is greater than or equal to the third threshold, and Tc ≥ Tcool, start the compressor refrigeration cycle. Then, continuously monitor the condenser temperature. When the condenser temperature is less than or equal to the difference between the third threshold and the third temperature fluctuation difference, and Tc ≤ Tc - Tdifference 3, shut down the compressor refrigeration cycle. If the condenser temperature Tc is again greater than or equal to the third threshold, and Tc ≥ Tc, start the compressor refrigeration cycle.

[0020] When the ambient temperature is less than or equal to the fourth set temperature, and Tring ≤ T4, perform the following steps: Start the refrigerant pump cooling mode, fully open the second throttle valve, control the third throttle valve, and control the refrigerant pump frequency and fan frequency to meet the cooling capacity requirements of the heat load.

[0021] The control method for the vehicle-mounted liquid-cooled cascade refrigeration unit proposed in this invention also includes monitoring changes in the return temperature of the coolant: When the rate of change of coolant return temperature is greater than the set value of temperature decrease rate, V≥K1, the following steps are executed: If the system is in refrigerant pump cooling mode, open the refrigerant pump system bypass valve to stabilize the return temperature of the coolant and prevent it from decreasing. If in mixed cooling mode, the four-way reversing valve is reversed, and the refrigerant pump is used to circulate and heat up in reverse to offset the cooling capacity generated by the compressor's refrigeration cycle, thus stabilizing the return temperature of the coolant so that it no longer decreases. If the system is in compressor cooling mode, the refrigerant pump will be activated to circulate the refrigerant, causing the four-way reversing valve to switch. The refrigerant pump will circulate the refrigerant in reverse to increase the temperature and offset the cooling capacity generated by the compressor refrigeration system, thus stabilizing the return temperature of the coolant and preventing it from decreasing further. When the rate of change of coolant return temperature is detected to be greater than the set value of temperature recovery rate, V≥K2, the liquid cooling source returns to normal cooling state, the refrigerant pump and compressor are online without stopping, the frequency is immediately increased, and the cooling capacity required by the heat load is restored.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: 1. When the radar starts up under low ambient temperature conditions, the refrigerant pump circulation system is controlled to remove the heat load of the radar system and quickly increase the condensing temperature. After the compressor refrigeration system starts up, it can quickly establish a pressure difference to start up and increase the cooling capacity. 2. After the radar is started under high ambient temperature conditions, the flow direction of the refrigerant pump circulation system is adjusted by controlling the refrigerant pump circulation system, thereby reducing the condensing temperature of the compressor refrigeration system and improving the refrigeration efficiency of the compressor refrigeration system. 3. The refrigerant pump circulation system and the compressor refrigeration system are independent of each other. Under extremely low ambient temperature conditions, the cooling capacity of the refrigerant pump circulation system can meet the heat dissipation requirements of the radar thermal load.

[0023] 4. In the refrigerant pump circulation, the existing technology uses ethylene glycol solution as the heat dissipation medium instead of refrigerant, which can avoid the corrosion of conventional tube-fin radiators by the coolant. 5. In a vehicle environment, a refrigerant pump system is used to replace the coolant circulation system. The phase change of the refrigerant in the refrigerant pump system improves heat exchange efficiency, reduces the weight of the second heat exchanger, and reduces the weight of the coolant. Attached Figure Description

[0024] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein: Figure 1 This is a system diagram of the vehicle-mounted liquid cooling source cascade refrigeration unit proposed in this invention; Figure 2 yes Figure 1 The diagram shows the refrigerant flow direction of the vehicle-mounted liquid cooling source cascade refrigeration unit when the four-way valve is not energized; Figure 3 yes Figure 1 The diagram shown illustrates the refrigerant flow direction of the vehicle-mounted liquid-cooled cascade refrigeration unit when the four-way valve is energized. Figure 4 This is the control flowchart of the vehicle-mounted liquid cooling source cascade refrigeration unit proposed in this invention; Figure 5 This is the control flowchart of the vehicle-mounted liquid cooling source cascade refrigeration unit when the ambient temperature is greater than the second set value; Figure 6 This is the control flowchart of the vehicle-mounted liquid cooling source cascade refrigeration unit when the ambient temperature is greater than the fourth set value and less than the second set value; Figure 7 This is the control flow diagram when compressor refrigeration is the main function and refrigerant pump circulation is the auxiliary function; Figure 8 This is the control flow diagram when the refrigerant pump cycle is the main function and the compressor refrigeration is the auxiliary function. Figure 9 This is the control flowchart when the ambient temperature is less than or equal to the fourth set temperature; Figure 10 This is a flowchart for controlling the rate of change of coolant temperature.

[0025] The markings in the image are as follows: 10 fans; 11 compressors; 12 condensers; 13. First throttle valve; 14. Evaporator; 15. First gas-liquid separator; 20F fluorine pump; 21. Four-way valve; 22 First heat exchanger; 23. Second throttle valve; 24 storage tanks; 25. Third throttle valve; 26. Second heat exchanger; 27. Second gas-liquid separator; 28. Bypass valve; 29. Check valve; 31. Liquid supply pipe; 32 return pipe.

[0026] T-ring - ambient temperature; T1 - First set temperature; T2 - Second set temperature; T3 - Third set temperature; T4 - Fourth set temperature; Ta - the first threshold of condensation temperature; Tb - the second threshold of condensation temperature; Tc - the third threshold of condensation temperature; T difference 1 - First temperature fluctuation difference; T difference 2 - second temperature fluctuation difference; T difference 3 - second temperature fluctuation difference; V - Rate of change of return temperature of coolant; K1 - Temperature decrease rate setting; K2 - Temperature recovery rate setting value; t - Preset time. Detailed Implementation

[0027] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and do not constitute any limitation on the invention.

[0028] The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of components and steps set forth in these embodiments do not limit the scope of protection of the invention.

[0029] While techniques, methods, and apparatus known to those skilled in the art are not discussed in detail herein, such techniques, methods, and apparatus should be considered part of this specification where appropriate. Any specific values ​​in this specification should be interpreted as merely exemplary and not as limiting the invention.

[0030] For ease of description, the terms used in the specification to describe position, such as "above", "to the left", "in front", etc., are only used to describe the spatial positional relationship between a component and other components in the embodiment shown in the figure. When the position of the component is different, the relative position will change. Therefore, the positional relationship of the embodiment in the figure should not be construed as limiting the present invention.

[0031] Furthermore, it should be noted that the use of terms such as "first" and "second" in the specification is merely for distinguishing similar components and does not imply any order of precedence. Therefore, it should not be construed as limiting the scope of protection of this invention.

[0032] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as constraints. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] As mentioned in the background section, vehicle-mounted liquid cooling sources provide sufficient coolant for various high-power transmitting electronic devices such as radar and base stations. These loads experience significant instantaneous power fluctuations and a rapid switching speed from startup to full-power transmission, requiring the liquid cooling source to respond quickly to these changes and rapidly reach the target cooling capacity. At normal temperatures, compressor cooling can quickly establish a pressure difference for rapid startup. However, at low temperatures, the condensation temperature is low, and the pressure difference builds up slowly. A single coolant air-cooling cycle cannot support the heat dissipation requirements of the radar's thermal load. Furthermore, coolant air-cooling systems are bulky and heavy, occupying valuable space and weight within the limited space of the vehicle environment.

[0034] Therefore, reducing the size and weight of on-board liquid cooling sources within the limited space and weight of the vehicle, and enabling the unit's cooling capacity to switch quickly from maximum to minimum, is a technical problem that the industry urgently needs to solve.

[0035] The concept of this invention is as follows: a refrigeration unit with a superimposed refrigeration cycle and a refrigerant pump cycle, and a vehicle-mountable liquid cooling source superimposed refrigeration unit is designed. A four-way reversing valve and a bypass connected in parallel with the heat exchanger used to cool the liquid cooling source are added to the refrigerant pump cycle. This allows the refrigeration unit to adjust its operating mode according to the ambient temperature range, the temperature range of the refrigeration cycle condenser, and the cooling rate of the coolant return temperature, so as to meet the needs of rapid cooling of the equipment.

[0036] The vehicle-mounted liquid cooling source cascade refrigeration unit proposed in this invention includes a refrigerant pump circulation system, a compressor refrigeration system, and a coolant circulation system. The three circulation systems are completely independent. The coolant circulation system and the compressor refrigeration system are both conventional circulation systems. The refrigerant pump circulation system and the compressor refrigeration system are cascaded and controlled according to the ambient temperature zone to meet the refrigeration requirements across the entire temperature range.

[0037] Figure 1 This is a system diagram of the vehicle-mounted liquid-cooled cascade refrigeration unit proposed in this invention. (See diagram below.) Figure 1 As shown, the vehicle-mounted liquid-cooled cascade refrigeration unit proposed in this invention includes a compression refrigeration cycle, a refrigerant pump cycle, and a coolant cycle, wherein: The compression refrigeration cycle includes a compressor 11, a condenser 12, a first throttling valve 13, an evaporator 14, and a first gas-liquid separator 15, which are connected in sequence by pipelines. During operation, the high-temperature and high-pressure refrigerant discharged from the compressor enters the condenser 12 for condensation, and then is throttled by the first throttling valve 13 to become a low-temperature and low-pressure liquid refrigerant. The liquid refrigerant enters the evaporator 14 for vaporization, and then returns to the compressor cycle after passing through the first gas-liquid separator 15. The refrigerant pump circulation system includes a refrigerant pump 20, a four-way reversing valve 21, a first heat exchanger 22, a second throttle valve 23, a liquid storage tank 24, a third throttle valve 25, a second heat exchanger 26, and a second gas-liquid separator 27, all connected sequentially via pipelines. The purpose of the liquid storage tank within the refrigerant pump circulation system is to store refrigerant and ensure that the refrigerant quantity can be adjusted during the operation of the refrigerant pump circulation system.

[0038] When the four-way reversing valve 21 is operating in the forward direction (not energized), the refrigerant discharged from the refrigerant pump 20 passes through the four-way reversing valve 21, the first heat exchanger 22, the second throttle valve 23, and the liquid storage tank 24, and then enters the third throttle valve 25 for throttling, becoming a low-temperature, low-pressure liquid refrigerant. After that, it evaporates through the second heat exchanger 26, and the vaporized refrigerant returns to the refrigerant pump cycle through the four-way reversing valve 21 and the second gas-liquid separator 27. When the four-way reversing valve is operating in the reverse direction (energized), the refrigerant discharged from the refrigerant pump 20 passes through the four-way reversing valve 21, the second heat exchanger 26, the third throttle valve 25, and the liquid storage tank 24, and then enters the second throttle valve 23 for throttling, becoming a low-temperature, low-pressure liquid refrigerant. After that, it evaporates through the first heat exchanger 22, and the vaporized refrigerant returns to the refrigerant pump cycle through the four-way reversing valve 21 and the second gas-liquid separator 27.

[0039] The refrigerant inlet and outlet of the second heat exchanger 26 are connected in parallel to a bypass. A bypass valve 28 is provided on the bypass valve, and a one-way valve 29 is provided on each of the left and right sides of the bypass valve to control the refrigerant flow direction. The purpose of providing a one-way valve on both sides of the bypass valve is to ensure unidirectional refrigerant flow when the unit is operating in reverse countercurrent mode, as the impact force is relatively large.

[0040] In the refrigerant pump circulation system, both the first heat exchanger 22 and the second heat exchanger 26 have throttling devices at their front ends to accommodate the forward and reverse operation of the four-way reversing valve. For example... Figure 2 As shown, when the four-way reversing valve is in the forward direction (not powered), the refrigerant discharged from the refrigerant pump flows through port CD to the first heat exchanger 22 (which acts as a condenser at this time) for condensation. Then, it passes through the second throttle valve 22 (fully open), the liquid receiver 24, and enters the third throttle valve 25 for throttling. It then enters the second heat exchanger 26 (which acts as an evaporator) for evaporation, and finally returns to the refrigerant pump cycle through the four-way reversing valve 21 (HS) and the second gas-liquid separator 27. Figure 3 As shown, when the four-way reversing valve is operated in reverse (energized), the refrigerant discharged from the refrigerant pump flows through port H to the second heat exchanger 26 (which acts as a condenser) for condensation, and then returns to the refrigerant pump cycle through the third throttle valve 25 (fully open), the liquid storage tank 24, the second throttle valve 23 (control), the first heat exchanger 22 (evaporation), the four-way reversing valve (DS), and the second gas-liquid separator 27.

[0041] The coolant in the coolant circulation enters the second heat exchanger 26 and evaporator 14 sequentially through the return pipe 31 for cooling, and then is sent to the cooling target through the supply pipe 32.

[0042] The condenser 12 of the compression refrigeration cycle and the first heat exchanger 22 in the refrigerant pump adopt a cascaded integrated structure with independent internal piping, and the heat dissipation is enhanced and controlled by the fan 10. As an example, the condenser and the first heat exchanger can adopt a finned coil structure, with the coils of the condenser and the coils of the first heat exchanger arranged alternately. When the four-way reversing valve reverses (goes in the opposite direction), the first heat exchanger 22 acts as an evaporator. This arrangement is beneficial for heat exchange between the condenser and the refrigerant in the first heat exchanger.

[0043] For ease of control, temperature sensors are installed on the condenser 12, the first heat exchanger 22, the supply pipe 31 and the return pipe 32 of the coolant circulation.

[0044] This invention also proposes a control method for the aforementioned vehicle-mounted liquid-cooled cascade refrigeration unit. The control method sets multiple ambient temperature parameters as control nodes and refers to three condensing temperature setpoints. Based on the range of ambient temperature and condensing temperature, it selects the operating mode of the vehicle-mounted liquid-cooled cascade refrigeration unit, including: compressor cooling mode, refrigerant pump cooling mode, mixed cooling mode, reverse counter-current mode, refrigerant pump circulation as the main mode with compressor cooling as the auxiliary mode, and compressor cooling as the main mode with refrigerant pump circulation as the auxiliary mode.

[0045] The control method proposed in this invention has the following characteristics: 1. By controlling the refrigerant pump circulation to raise the temperature of the condenser, the start-up preparation time of the compressor refrigeration system is reduced; 2. Cooling the condenser by controlling the fluorine pump cycle to improve the refrigeration effect of the compressor at high ambient temperatures; 3. By controlling the fluorine pump cycle to counteract the cooling capacity of the compressor refrigeration system in the reverse direction, the on-line operation of the liquid cooling source without refrigeration is realized.

[0046] In Figure 4 the illustrated embodiment, the control method proposed by the present invention sets four ambient temperature parameters as control nodes throughout the entire control process, and refers to three set condensing temperature values, and selects the operation mode of the vehicle-mounted liquid cooling source cascade refrigeration unit according to the intervals where the ambient temperature and the condensing temperature are located.

[0047] The four ambient temperature parameters are respectively defined as a first set temperature T1, a second set temperature T2, a third set temperature T3, and a fourth set temperature. The three condensing temperatures are respectively defined as a first threshold Ta, a second threshold Tb, and a third threshold Tc.

[0048] Figure 4 is the control flow chart of the vehicle-mounted liquid cooling source cascade refrigeration unit proposed by the present invention.

[0049] When the liquid cooling source cascade refrigeration unit is in operation, the ambient temperature T_amb is detected first; When the ambient temperature is greater than or equal to the second set temperature, T_amb ≥ T2, the compressor refrigeration cycle is started, and then the following steps are performed (refer to Figure 4 and Figure 5 ): After the compressor is turned on, the condensing temperature will rise. When it is detected that the ambient temperature is greater than or equal to the first set temperature, T_amb ≥ T1, the condenser temperature is detected to determine whether the fluorine pump meets the reverse operation condition. When the condenser temperature is greater than or equal to the first threshold, T_cond ≥ Ta, the fluorine pump circulation system is started, the four-way reversing valve 21 is energized for reversing switching (the fluorine pump operates in reverse direction), at this time the first heat exchanger 22 serves as an evaporator, and the two heat exchanger 26 serves as a condenser, the third throttle valve 25 is fully opened, the second throttle valve 23 is controlled, and the refrigerant in the fluorine pump cools the condenser in the compressor refrigeration cycle; when the condenser temperature is less than or equal to the difference between the first threshold and the first temperature fluctuation difference, T_cond ≤ Ta - T_diff1, the fluorine pump circulation system stops operating. T_diff1 is the temperature fluctuation difference that controls the fluorine pump cycle as an auxiliary switching operation.

[0050] The condenser temperature of the condenser 12 will drop after being cooled by the fluorine pump cycle, so when the condenser temperature value is in the interval between the first threshold Ta and the difference between the first threshold and the first temperature fluctuation difference, Ta - T_diff1 < T_cond < Ta, the current state is maintained.

[0051] When the ambient temperature is relatively high, the four-way reversing valve of the fluorine pump cycle starts reverse circulation, which reduces the condensing temperature of the condenser by consuming a small amount of cold energy of the coolant, improves the refrigeration efficiency of the entire compressor refrigeration system, and achieves an increase in the overall cooling capacity.

[0052] When the ambient temperature is greater than or equal to the second set temperature and less than the first set temperature, T2≤T_amb<T1, the compressor refrigeration system operates normally, the fluorine pump cycle stops running, and at this time the cooling capacity of the compressor refrigeration cycle system meets the demand of the radar thermal load.

[0053] When the ambient temperature is greater than the fourth set temperature and less than the second set temperature, T4<T_amb<T2, this is the temperature range for cascaded operation of the fluorine pump cycle and the compressor refrigeration cycle (mixed operation mode), with reference to Figure 4 and Figure 6 , the following steps are executed: The fluorine pump circulation system is started first. At this time, the fluorine pump circulation system and the transmission of the radar system are in a parallel state. The heat generated by the fluorine pump cycle heats up the condenser. For the compressor refrigeration system, the temperature of the condenser rises and the condensing pressure increases, which can quickly establish a high-low pressure difference when the compressor refrigeration system is running, reduce the time to reach the target cooling capacity, and reduce the pre-cooling preparation time before the radar transmission is turned on. After the fluorine pump runs for a preset time t, which has a range proportional relationship with the ambient temperature T_amb, the ambient temperature is detected again for a second judgment, that is, the main-auxiliary judgment for the operation of the cascaded system is entered.

[0054] With reference to Figure 4 and Figure 7 , when the ambient temperature is greater than or equal to the third set temperature and less than the second set temperature, T3≤T_amb<T2, the operation mode with the compressor refrigeration as the main part and the fluorine pump cycle as the auxiliary part is entered. At this time, the compressor refrigeration cycle is turned on, then the condenser temperature T_cold is detected. When the condenser temperature is greater than or equal to the second threshold, T_cold≥Tb, the fluorine pump cycle is turned off. Since the fluorine pump circulation system has been running before the second judgment to heat up the condenser, and the refrigeration oil of the compressor refrigeration system has also completed the temperature rise, the compressor refrigeration system can be started quickly and reach the target cooling capacity rapidly. After the compressor refrigeration system is started, the operation of the fluorine pump circulation system is stopped, and then the condenser temperature T_cold is continuously judged. When the condenser temperature is less than or equal to the difference between the second threshold and the second temperature fluctuation difference, T_cold≤Tb-T_diff2, the fluorine pump circulation system is started to heat up the condenser temperature. T_diff2 is the second temperature fluctuation difference for the switching operation when compressor refrigeration serves as an auxiliary part.

[0055] With reference to Figure 4 and Figure 8, when the ambient temperature is greater than the fourth set temperature and less than or equal to the third set temperature, T4<T_ambient≤T3, the unit enters an operation mode with the fluorine pump cycle as the main and the compressor refrigeration cycle as the auxiliary. The fluorine pump cycle continues to cool the radar thermal load normally, and at the same time uses the carried heat to heat up the condenser of the compressor refrigeration system, and heats up the condenser during the operation of the fluorine pump cycle. When the condenser temperature is greater than or equal to the third threshold, T_cold≥Tc, the cooling capacity of the fluorine pump circulation system cannot fully meet the heat dissipation requirement of the radar thermal load. At this time, by starting the compressor refrigeration circulation system, since the fluorine pump circulation system has heated up the condenser, the refrigeration oil of the compressor refrigeration system has also completed the temperature rise, so the compressor refrigeration system can be started quickly. After the radar thermal load changes, when the condenser temperature decreases and the condensation temperature is less than or equal to the difference between the third threshold and the third temperature fluctuation difference, T_cold≤Tc-T_diff3, the compressor refrigeration system stops, and the fluorine pump cycle still maintains the operating state at this time. If the condenser temperature continues to rise later and the condensation temperature reaches greater than or equal to the third threshold again, T_cold1≥Tc, the compressor refrigeration system starts.

[0056] For example, when T3 is set to -10°C, the fluorine pump circulation system has a certain pressure after the fluorine pump operates. At this time, the evaporated refrigerant is directly cooled into liquid at this ambient temperature and this pressure. Due to the relatively high ambient temperature, when the condenser temperature T_cold rises to a certain level, the cooling capacity of the fluorine pump cycle cannot meet the demand of the radar thermal load. At this time, it is necessary to turn on the compressor refrigeration for auxiliary cooling. Because after the radar thermal load changes and decreases, the condenser temperature T_cold also decreases. At this time, the demand can be met only by the fluorine pump cycle without the compressor refrigeration, and the compressor refrigeration is turned off according to the conditions.

[0057] Reference Figure 4 and Figure 9 , when T_ambient≤T4, the following steps are executed: The fluorine pump circulation system is directly operated, the second throttle valve 23 is fully opened, and the third throttle valve 25, the fluorine pump frequency and the fan frequency are controlled to meet the cooling capacity requirement of the radar thermal load.

[0058] Taking a single fluorine pump cycle using R134a refrigerant as an example for implementation, T4 can be set to -25°C. At this time, the evaporated refrigerant is directly cooled into liquid at this ambient temperature. Since the temperature in the second heat exchanger is at a working temperature of about 35°C after the radar is turned on for transmission, the refrigerant can circulate to the second heat exchanger through the fluorine pump to evaporate and absorb heat for cooling.

[0059] Please refer to Figure 10When the radar suddenly switches from operating to stopped, the heat load drops drastically, and the coolant return temperature Treturn decreases rapidly. When the rate of change of the coolant return temperature Treturn is greater than or equal to the set temperature decrease rate, V ≥ K1, and the liquid cooling source enters a non-cooling online state. At this time, the unit switches according to the conditions: If the unit is in single-fluorine pump circulation operation mode (fluorine pump circulation cooling mode), open the fluorine pump system bypass valve 28 to control the frequency of the fluorine pump and fan, control the flow rate, and stabilize the coolant return temperature so that it no longer decreases. If the unit is in a state where the refrigerant pump cycle and the compressor refrigeration cycle are running simultaneously (mixed cooling mode), then the refrigerant pump four-way reversing valve 21 is opened, the frequency of the refrigerant pump, fan and compressor is controlled, and the opening of the first throttle valve 13, the second throttle valve 23 and the third throttle valve 25 are adjusted. The refrigerant pump cycle is used to reverse the temperature to offset the cooling capacity generated by the compressor refrigeration system, so as to stabilize the coolant return temperature and ensure that both the refrigerant pump cycle and the compressor refrigeration cycle are online. If the unit is in single-compressor refrigeration system operation mode (compressor cooling mode), the refrigerant pump cycle is started, and the four-way reversing valve 21 is opened to control the frequency of the refrigerant pump, fan and compressor. The opening of the first throttle valve 13, the second throttle valve 23 and the third throttle valve 25 are adjusted. The refrigerant pump cycle is used to reverse the temperature to offset the cooling capacity generated by the compressor refrigeration system. This stabilizes the coolant return temperature and ensures that both the refrigerant pump cycle and the compressor refrigeration cycle are online. At this time, the liquid cooling source is in an online state without refrigeration.

[0060] When the rate of change of the coolant return temperature is detected to be rising rapidly, the radar has already started transmitting and the heat load is rising sharply. When the rate of change of the coolant return temperature T_return is greater than the set value of the temperature rise rate, V≥K2, the liquid cooling source returns to normal cooling state, the refrigerant pump, fan and compressor are all online without stopping, the frequency can be increased immediately, and the cooling capacity required for the radar heat load can be restored.

[0061] Radars switch between transmitting and silent states in a very short time. Therefore, the cooling unit needs to be able to adapt to temperature changes quickly. The radar's thermal load status is determined by detecting the rate of temperature change of the return liquid in the coolant circulation system. The flow direction of the refrigerant pump circulation is controlled to counteract the cooling capacity of the compressor circulation. At low temperatures, the refrigerant pump circulation is bypassed to achieve heat exchange without coolant circulation.

[0062] The vehicle-mounted liquid-cooled cascade refrigeration unit proposed in this invention has the following advantages: In low-temperature environments, the condenser of the compressor refrigeration system is heated by the refrigerant pump circulation, which increases the condensing pressure. After the compressor refrigeration cycle starts, the pressure difference between the high and low pressures of the refrigeration system is established more quickly, and the target cooling capacity can be reached rapidly. In extremely low temperature environments, the refrigerant boiling point of the fluorine pump circulation system is lower than the ambient temperature, so it is directly switched to fluorine pump circulation to control the fluorine pump and fan to meet the cooling requirements of the radar thermal load. In high-temperature environments, after the compressor refrigeration system starts operating, the refrigerant pump circulates in reverse to cool the condenser of the compressor refrigeration system, thereby reducing the condensing temperature of the condenser and increasing the cooling capacity.

[0063] After the radar stops, the refrigerant pump circulation and compressor refrigeration system are controlled to simultaneously offset the cooling capacity online, achieving an online state without cooling. After the radar goes from stopping to full transmission, it can quickly switch to a new state to increase the cooling capacity and reduce the time delay caused by the start-up and shutdown time difference of the liquid cooling source.

[0064] Different refrigerants can be used in the refrigerant pump cycle and the compressor cycle. Since different refrigerants have different boiling points, the overlapping operating temperature range of the compressor refrigeration and the refrigerant pump cycle will be relatively large. The fluctuation range of the switching operating point temperature is large, and it is not easy to cause repeated switching of the operating mode.

[0065] The refrigerant used in the refrigerant pump can also be the same as that used in the compressor, reducing the types of spare parts required for maintenance. Because different refrigerants have different characteristics, the operating point temperature parameters need to be adjusted based on the actual type of refrigerant being used. For example, if both the compressor and the refrigerant pump use R134a refrigerant, since they have the same boiling point, the compressor refrigerates and compresses gaseous refrigerant, while the refrigerant pump circulates liquid refrigerant. The operating boundaries are clear, so the overlapping operating temperature range of the compressor refrigeration and the refrigerant pump circulation will be very small. The operating point temperature will frequently fluctuate, and this small allowable fluctuation range can easily lead to repeated switching of operating modes.

[0066] The control method proposed in this invention can be programmed into a computer control program and stored on a control chip. When the control chip triggers the computer program to run, the control method of the air source cascade heat pump described above is executed.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the concept and principles of the present invention should be included within the scope of protection defined by the claims of the present invention.

Claims

1. A vehicle-mounted liquid-cooled cascade refrigeration unit, comprising a compression refrigeration cycle, a refrigerant pump cycle, and a coolant cycle, characterized in that, The fluorine pump cycle includes a four-way reversing valve, a first heat exchanger and a second heat exchanger; the condenser of the compression refrigeration cycle and the first heat exchanger of the fluorine pump adopt a cascade structure, and the cooling liquid in the cooling liquid circulation is sequentially cooled through the second heat exchanger and the evaporator of the compression refrigeration cycle.

2. The vehicle-mounted liquid-cooled cascade refrigeration unit according to claim 1, characterized in that, The compression refrigeration cycle includes a compressor, a condenser, a first throttle valve, an evaporator and a first gas-liquid separator which are sequentially connected through a pipeline.

3. The vehicle-mounted liquid-cooled cascade refrigeration unit according to claim 1, characterized in that, The fluorine pump cycle includes a fluorine pump, a four-way reversing valve, a first heat exchanger, a second throttle valve, a liquid storage tank, a third throttle valve, a second heat exchanger and a second gas-liquid separator which are sequentially connected through a pipeline.

4. The vehicle-mounted liquid-cooled cascade refrigeration unit according to claim 3, characterized in that, A bypass is connected in parallel to the refrigerant inlet and outlet of the second heat exchanger, a bypass valve is arranged on the bypass, and check valves are respectively arranged on two sides of the bypass valve.

5. The vehicle-mounted liquid-cooled cascade refrigeration unit according to claim 2 or 3, characterized in that, Temperature sensors are arranged on the condenser, the first heat exchanger, and the liquid supply pipe and the liquid return pipe of the cooling liquid circulation.

6. The control method for the vehicle-mounted liquid-cooled cascade refrigeration unit according to any one of claims 1-5, characterized in that, Four ambient temperature parameters are set as control nodes, three condensing temperature set values are referred to, and the operation mode of the on-vehicle liquid cooling source cascade refrigeration unit is selected according to the interval where the ambient temperature and the condensing temperature are located, including: a compressor cooling mode, a fluorine pump cooling mode, a hybrid cooling mode, a reverse hedging mode, a mode with the fluorine pump cycle as the main part and the compression refrigeration as the auxiliary part, and a mode with the compression refrigeration as the main part and the fluorine pump cycle as the auxiliary part.

7. The control method according to claim 6, characterized in that, When the ambient temperature is greater than or equal to a second set value, T_ambient≥T2, the compression refrigeration cycle is turned on, and the following steps are executed subsequently: When the ambient temperature is greater than or equal to a first set value and the condenser temperature is greater than or equal to a first threshold, T_ambient≥T1 and T_cond≥Ta, the fluorine pump cycle is started, the four-way reversing valve is reversed at the same time, the reverse hedging mode is operated to cool the condenser; when the condenser temperature is less than or equal to the difference between the first threshold and the first temperature fluctuation difference, T_cond≤Ta-T_diff1, the fluorine pump cycle is turned off; When the ambient temperature is greater than or equal to the second set value and less than or equal to the first set value, T2≤T_ambient≤T1, the compressor cooling mode is maintained.

8. The control method according to claim 6, characterized in that, When the ambient temperature is greater than a fourth set temperature and less than the second set temperature, T4<T_ambient<T2, the following steps are executed: The fluorine pump cycle is started first, after operating for a preset time t, the ambient temperature is detected again; when the ambient temperature is greater than or equal to a third set value and less than the second set value, T3≤T_ambient<T2, the operation mode with the compression refrigeration as the main part and the fluorine pump cycle as the auxiliary part is entered; when the ambient temperature is greater than the fourth set value and less than or equal to the third set value, T4<T_ambient≤T3, the operation mode with the fluorine pump cycle as the main part and the compression refrigeration as the auxiliary part is entered.

9. The control method according to claim 8, characterized in that, After entering the operation state with the compression refrigeration as the main part and the fluorine pump cycle as the auxiliary part, the following steps are executed: The compressor cycle is turned on, the condenser temperature is detected, and when the condenser temperature is greater than or equal to a second threshold, T_cond≥Tb, the fluorine pump cycle is turned off; When the condenser temperature is less than or equal to the difference between the second threshold and the second temperature fluctuation difference, T_cond≤Tb-T_diff2, the fluorine pump cycle is turned on, the four-way reversing valve is reversed, and the reverse hedging mode is entered.

10. The control method according to claim 8, characterized in that, After entering the operation state with the fluorine pump as the main part and the compression refrigeration as the auxiliary part, the following steps are executed: Start the refrigerant pump cycle and monitor the condenser temperature. When the condenser temperature is greater than or equal to the third threshold, and Tc ≥ Tcool, start the compressor refrigeration cycle. Then, continuously monitor the condenser temperature. When the condenser temperature is less than or equal to the difference between the third threshold and the third temperature fluctuation difference, and Tc ≤ Tc - Tdifference 3, shut down the compressor refrigeration cycle. If the condenser temperature Tc is again greater than or equal to the third threshold, and Tc ≥ Tc, start the compressor refrigeration cycle.

11. The control method according to claim 6, characterized in that, When the ambient temperature is less than or equal to the fourth set temperature, T_ring ≤ T4, the refrigerant pump cooling mode is activated, the second throttle valve is fully open, the third throttle valve is controlled, and the refrigerant pump frequency and fan frequency are controlled to meet the cooling capacity requirements of the heat load.

12. The control method according to claim 6, characterized in that, This also includes monitoring changes in the coolant return temperature. When the rate of change of return liquid temperature is greater than the set value of temperature decrease rate, V≥K1, the following steps are executed: If the system is in refrigerant pump cooling mode, open the refrigerant pump system bypass valve to stabilize the return liquid temperature and prevent it from decreasing further. If in mixed cooling mode, the four-way reversing valve is reversed, and the refrigerant pump is used to circulate and heat up in reverse to offset the cooling capacity generated by the compressor's refrigeration cycle, thus stabilizing the coolant return temperature so that it no longer decreases. If the compressor is in cooling mode, the refrigerant pump will start to circulate, causing the four-way reversing valve to switch. The refrigerant pump will circulate in reverse to raise the temperature and offset the cooling capacity generated by the compressor cooling cycle, thus stabilizing the coolant return temperature so that it no longer decreases. When the rate of change of the return liquid temperature is detected to be greater than the set value of the temperature recovery rate, V≥K2, the liquid cooling source returns to normal cooling state, the refrigerant pump and compressor are online without stopping, the frequency is immediately increased, and the cooling capacity required by the heat load is restored.

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