Cascade water chilling unit system

Abstract

The utility model discloses a cascade type water chilling unit system which comprises a circulating water tank, a water system inner circulating unit, a water system outer circulating unit, a high-temperature section refrigerating circulating unit and a low-temperature section refrigerating circulating unit. The circulating water tank is connected with the high-temperature-section refrigerating cycle unit and the low-temperature-section refrigerating cycle unit through the water system inner circulating unit. The circulating water tank is connected with a to-be-tested pipeline through the water system outer circulating unit; the circulating water tank conveys a solution to the high-temperature-section refrigeration cycle unit or the low-temperature-section refrigeration cycle unit through the water system inner circulating unit, and the solution achieves heat exchange through the high-temperature-section refrigeration cycle unit or the low-temperature-section refrigeration cycle unit. The circulating water tank conveys a solution to the to-be-tested pipeline through the water system external circulating unit, and the solution is used for testing the test pipeline.

Description

Technical Field

[0001] This utility model relates to the field of chiller technology, and in particular to a cascade chiller system. Background Technology

[0002] In many industries today, such as new energy vehicles, aerospace, and electronics, the environmental testing requirements for various equipment and components are becoming increasingly stringent. Among these requirements, precise temperature control has become a key element in the testing process.

[0003] Taking new energy vehicles as an example, their core components, such as motors, battery cells, battery packs, controllers, and PTCs, need to undergo rigorous testing under different temperature environments during the research and development and production stages to ensure their reliability and stability in actual operation. This requires high and low temperature chiller units to provide a medium ranging from -40℃ to 140℃ to simulate various extreme environments.

[0004] However, traditional high and low temperature single-stage compression chiller systems have significant limitations. Regarding the low-temperature cooling rate, when dropping from -30℃ to -40℃, the rate is often less than 1℃ / min. Such a cooling rate is insufficient for efficient testing, significantly extending the testing cycle and increasing R&D and production costs. Furthermore, existing refrigeration systems suffer from serious deficiencies in the flexibility of coolant circulation paths. Traditional systems often have a single, fixed coolant circulation path, making it impossible to flexibly adjust the coolant flow direction according to testing requirements or equipment operating conditions. Utility Model Content

[0005] This utility model provides a cascade chiller system to address at least one defect in the existing technology.

[0006] This utility model embodiment provides a cascade chiller unit system, including:

[0007] Circulating water tank, internal water system circulation unit, external water system circulation unit, high-temperature section refrigeration circulation unit, low-temperature section refrigeration circulation unit;

[0008] The circulating water tank is connected to the high-temperature section refrigeration circulation unit and the low-temperature section refrigeration circulation unit respectively through the internal circulation unit of the water system;

[0009] The circulating water tank is connected to the pipeline to be tested through the internal circulation unit of the water system;

[0010] The circulating water tank delivers a solution to the high-temperature section refrigeration cycle unit or the low-temperature section refrigeration cycle unit through the internal circulation unit of the water system, and the solution achieves heat exchange through the high-temperature section refrigeration cycle unit or the low-temperature section refrigeration cycle unit;

[0011] The circulating water tank supplies a solution to the pipeline under test through the external circulation unit of the water system, and the solution is used for testing the pipeline.

[0012] Optionally, the water system internal circulation unit includes an internal circulation pump and a three-way valve;

[0013] The circulating water tank is connected to the three-way valve via the internal circulation pump, and the three-way valve is connected to the liquid inlet of the high-temperature section refrigeration cycle unit and the low-temperature section refrigeration cycle unit.

[0014] The outlets of the high-temperature refrigeration cycle unit and the low-temperature refrigeration cycle unit are connected to the circulating water tank.

[0015] Optionally, the water system external circulation unit includes an external circulation pump;

[0016] The circulating water tank is connected to the inlet of the pipeline under test via the external circulation pump, and the return port of the pipeline under test is connected to the circulating water tank.

[0017] Optionally, the water system external circulation unit further includes: a first ball valve, a second ball valve, a third ball valve, and a proportional regulating valve;

[0018] The first ball valve is configured on the pipeline connecting the circulating water tank and the inlet of the pipeline to be tested, and is used to open or close the inlet channel;

[0019] The second ball valve is configured on the pipeline connecting the circulating water tank and the return port of the pipeline to be tested, and is used to open or close the return channel;

[0020] The first ball valve and the second ball valve are installed on the pipeline connecting the circulating water tank to the inlet of the pipeline to be tested. The first ball valve and the second ball valve are connected to the air source. The first ball valve and the second ball valve are used to open or close the air source channel.

[0021] Optionally, the water system external circulation unit further includes: a first temperature sensor, a second temperature sensor, a first pressure sensor, a second pressure sensor, a flow meter, and a filter;

[0022] The first temperature sensor and the first pressure sensor are disposed on the pipeline connecting the circulating water tank and the inlet of the pipeline to be tested;

[0023] The second temperature sensor, the second pressure sensor, the flow meter, and the filter are configured on the pipeline connecting the circulating water tank and the return port of the pipeline to be tested.

[0024] Optionally, the circulating water tank is also equipped with a heater.

[0025] Optionally, an expansion tank is also provided outside the circulating water tank.

[0026] Optionally, the external circulation unit of the water system is also equipped with a bypass valve, which is connected to the inlet and outlet of the circulating water tank respectively.

[0027] Optionally, the high-temperature section refrigeration cycle unit is equipped with a first bypass pipeline unit, which is used for cooling the high-temperature section refrigeration cycle unit.

[0028] Optionally, the low-temperature refrigeration cycle unit is equipped with a second bypass pipeline unit, which is used for cooling the low-temperature refrigeration cycle unit.

[0029] Compared with existing technologies, the advantages of this utility model are as follows: This utility model proposes a cascade chiller system, which includes a circulating water tank, an internal water system circulation unit, an external water system circulation unit, a high-temperature refrigeration circulation unit, and a low-temperature refrigeration circulation unit. The internal and external water system circulation units can switch the path of the coolant output from the circulating water tank. When there are different usage requirements for the coolant, the flow direction of the coolant can be quickly adjusted by switching the circulation path of the coolant between the test system and the cascade chiller. The circulating water tank, as the storage and regulation center of the coolant, combined with the internal and external water system circulation units, enables the cascade chiller to operate efficiently under different operating conditions. When the test system does not require coolant, the external water system circulation unit can circulate the coolant inside the cascade chiller to maintain the low-temperature environment of the unit, preparing it for the next test. This avoids energy loss and equipment wear caused by frequent start-ups and shutdowns, and improves the equipment utilization rate of the cascade chiller. Attached Figure Description

[0030] Figure 1 This is a block diagram of the cascade chiller system structure in the embodiment;

[0031] Figure 2 This is a schematic diagram of the cascade chiller system structure in the embodiment. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.

[0033] Figure 1 This is a block diagram of the cascade chiller system structure in the embodiment, for reference. Figure 1 The cascade chiller system includes:

[0034] Circulating water tank 303, water system internal circulation unit 200, water system external circulation unit 300, high temperature section refrigeration circulation unit 400, low temperature section refrigeration circulation unit 500;

[0035] The circulating water tank 303 is connected to the high-temperature section refrigeration circulation unit 400 and the low-temperature section refrigeration circulation unit 500 respectively through the water system internal circulation unit 200;

[0036] The circulating water tank 303 is connected to the pipeline to be tested through the internal circulation unit 200 of the water system;

[0037] The circulating water tank 303 delivers solution to the high-temperature section refrigeration cycle unit 400 or the low-temperature section refrigeration cycle unit 500 through the water system internal circulation unit 200. The solution achieves heat exchange through the high-temperature section refrigeration cycle unit 400 or the low-temperature section refrigeration cycle unit 500.

[0038] The circulating water tank 303 delivers a solution to the pipeline to be tested through the external circulation unit 300 of the water system. The solution is used for testing the pipeline.

[0039] For example, in this solution, the circulating water tank 303 is set to store coolant (coolant). The type of coolant can be determined according to the usage requirements. For example, ethylene glycol solution can be used as coolant.

[0040] Because of its low freezing point, ethylene glycol solution can withstand low-temperature environments. For example, in a cascade chilled water system, where the temperature of the low-temperature stage evaporator may reach -40°C or even lower, an ethylene glycol solution of a suitable concentration (such as an ethylene glycol mass fraction of about 50%-60%) can still remain liquid, effectively transferring cooling energy to the areas that need it, without clogging the pipes due to solidification.

[0041] For example, in this solution, taking ethylene glycol solution as an example, its uses in feeding it into the high-temperature refrigeration cycle unit 400 and the low-temperature refrigeration cycle unit 500 include:

[0042] In the low-temperature stage circulation of a cascade high-low temperature chiller system, ethylene glycol solution serves as the refrigerant. After the low-temperature stage evaporator absorbs cold energy, the ethylene glycol solution is cooled within the evaporator, and its temperature decreases. Subsequently, this low-temperature ethylene glycol solution is piped to equipment or areas requiring low-temperature cooling.

[0043] In a cascade high and low temperature chilled water system, when high temperatures are required, the circulation path of the refrigerant can be changed by switching. At this time, the high-temperature stage uses an evaporator-condenser to cool the refrigerant in the low-temperature stage, causing the refrigerant in the low-temperature stage to condense into a liquid, thereby meeting the specific high-temperature requirements and maintaining the stable operation of the entire cascade system.

[0044] For example, in this solution, the high-temperature section refrigeration cycle unit 400 and the low-temperature section refrigeration cycle unit 500 constitute a cascade chiller. In this solution, the specific structure and connection relationship of the high-temperature section refrigeration cycle unit 400 and the low-temperature section refrigeration cycle unit 500 are not limited.

[0045] The high-temperature refrigeration cycle unit 400 includes at least a high-temperature compressor, a condenser, a high-temperature evaporator, a condenser-evaporator, an expansion valve, and a dryer filter.

[0046] The low-temperature refrigeration cycle unit 500 includes at least a low-temperature compressor, a low-temperature evaporator, a condenser-evaporator, and an expansion valve;

[0047] Its working principle can be summarized as follows:

[0048] In the low-temperature evaporator, the refrigerant absorbs heat from the object being cooled and evaporates, becoming a low-temperature, low-pressure refrigerant gas. This gas is then drawn into the low-temperature compressor and compressed into a high-temperature, high-pressure gas, which then enters the condenser-evaporator. In the condenser-evaporator, the low-temperature refrigerant gas releases heat to the high-temperature refrigerant, thus condensing into a high-pressure liquid. Next, the high-pressure liquid passes through an expansion valve, becoming a low-temperature, low-pressure liquid again, and re-enters the low-temperature evaporator, completing one low-temperature refrigeration cycle.

[0049] The high-temperature refrigerant gas, which absorbs heat and evaporates in the condenser-evaporator, is drawn into the high-temperature compressor and compressed into a high-temperature, high-pressure gas. It then enters the condenser, where it releases heat to the cooling medium and condenses into a high-pressure liquid. Afterward, the high-pressure liquid is filtered through a dryer filter and its pressure is reduced by an expansion valve before entering the condenser-evaporator again, where it evaporates and absorbs heat, completing one high-temperature refrigeration cycle.

[0050] The condenser-evaporator facilitates heat transfer between the high-temperature and low-temperature sections. The evaporation of the refrigerant in the high-temperature section absorbs the heat released by the condensation of the refrigerant in the low-temperature section, allowing the refrigerant in the low-temperature section to condense at a lower temperature, while the refrigerant in the high-temperature section evaporates at a relatively higher temperature, thus achieving the goal of producing low-temperature chilled water.

[0051] For example, in this solution, the water system internal circulation unit 200 is specifically used to realize the circulation of coolant between the circulating water tank and the high-temperature section refrigeration circulation unit 400 and the low-temperature section refrigeration circulation unit 500;

[0052] Specifically, based on the circulation pipeline provided by the water system internal circulation unit 200, the coolant can exchange heat with the high-temperature section evaporator to reduce the temperature to the target value, or the coolant can exchange heat with the low-temperature section evaporator to reduce the temperature to the target value.

[0053] For example, in this solution, the water system external circulation unit 300 is specifically used to realize the circulation of coolant between the circulating water tank and the pipeline to be tested, wherein the type of pipeline to be tested is not limited;

[0054] The pipelines to be tested may include automotive engine cooling pipelines, electric vehicle battery thermal management system pipelines, automotive air conditioning system pipelines, automotive braking system cooling pipelines, etc.

[0055] This embodiment proposes a cascade chiller system, which includes a circulating water tank, an internal water circulation unit, an external water circulation unit, a high-temperature refrigeration circulation unit, and a low-temperature refrigeration circulation unit. The internal water circulation unit can store the cooling medium processed by the high-temperature or low-temperature refrigeration circulation unit in the circulating water tank, and the external water circulation unit can transport the cooling medium in the circulating water tank to the test object.

[0056] The circulating water tank, serving as the storage and regulation center for coolant, combined with internal and external water system circulation units, enables the cascade chiller unit to operate efficiently under various conditions. When the test system does not require coolant, the external water system circulation unit can circulate the coolant within the cascade chiller unit, maintaining the unit's low-temperature environment and preparing it for the next test. This avoids energy loss and equipment wear caused by frequent start-ups and shutdowns, improving the equipment utilization rate of the cascade chiller unit.

[0057] Furthermore, in this design, the high-temperature cooling cycle unit and the low-temperature cooling cycle unit constitute a cascade refrigeration system, which can achieve cooling over a wide temperature range. It consists of two refrigeration cycles: a high-temperature cycle and a low-temperature cycle. The high-temperature cycle first transfers heat to the low-temperature cycle, which then further cools the air. This structure allows the unit to produce very low temperatures, typically reaching -80℃ or even lower, while also providing relatively low temperatures in the high-temperature range, such as around -5℃ to -10℃, making it suitable for various testing scenarios with different temperature requirements.

[0058] exist Figure 1 Based on the scheme shown, in one possible implementation, the water system internal circulation unit includes an internal circulation pump and a three-way valve;

[0059] The circulating water tank is connected to a three-way valve via an internal circulation pump. The three-way valve is connected to the liquid inlet of the high-temperature section refrigeration cycle unit and the low-temperature section refrigeration cycle unit.

[0060] The outlets of the high-temperature refrigeration cycle unit and the low-temperature refrigeration cycle unit are connected to the circulating water tank.

[0061] For example, in this solution, an internal circulation pump is used to drive the coolant to flow within the pipes of the water system's internal circulation unit.

[0062] For example, in this solution, the three-way valve is used to switch between the coolant input to the high-temperature section of the refrigeration cycle unit and the coolant input to the low-temperature section of the refrigeration cycle unit.

[0063] For example, in this solution, the above switching process can be implemented based on the following strategy:

[0064] When the target value of the coolant is greater than or equal to the set value, the three-way valve can be controlled to connect the circulating water tank and the high-temperature section refrigeration cycle unit. The internal circulation pump will then exchange heat between the coolant in the circulating water tank and the high-temperature section evaporator to reduce the coolant temperature to the target value.

[0065] When the target coolant value is less than the set value, the three-way valve is controlled to connect the circulating water tank and the low-temperature refrigeration cycle unit. The internal circulation pump then exchanges heat between the coolant in the circulating water tank and the low-temperature evaporator to lower the coolant temperature to the target value.

[0066] Based on any of the aforementioned schemes, in one possible implementation scheme, the water system external circulation unit includes an external circulation pump;

[0067] The circulating water tank is connected to the inlet of the pipeline under test via an external circulation pump, and the return port of the pipeline under test is connected to the circulating water tank.

[0068] For example, in this solution, an external circulation pump is used to drive the coolant to flow in the pipeline of the water system external circulation unit.

[0069] Based on the aforementioned scheme where the external circulation unit of the water system includes an external circulation pump, in one possible implementation, the external circulation unit of the water system further includes: a first ball valve, a second ball valve, a third ball valve, and a proportional regulating valve;

[0070] The first ball valve is installed on the pipeline connecting the circulating water tank and the inlet of the pipeline to be tested, and is used to open or close the inlet channel.

[0071] The second ball valve is installed on the pipeline connecting the circulating water tank and the return port of the pipeline to be tested, and is used to open or close the return channel.

[0072] A third ball valve and a proportional regulating valve are installed on the pipeline connecting the circulating water tank to the inlet of the pipeline to be tested. The third ball valve and the proportional regulating valve are connected to the air source and are used to open or close the air source channel.

[0073] For example, in this solution, when the first ball valve and the second ball valve are open, the circulating water tank and the pipeline to be tested are connected, and the liquid in the circulating water tank can enter the pipeline to be tested and circulate. The first ball valve and the second ball valve can be manually controlled or program-controlled to achieve the specified opening or closing action.

[0074] For example, in this solution, by controlling the third ball valve and the proportional regulating valve, the air source can be connected to the circulation loop between the pipeline under test and the circulating water tank. The air source blows the liquid in the pipeline under test back into the circulating water tank, preventing liquid residue in the pipeline under test from causing leakage.

[0075] Specifically, close the first ball valve (disconnect the inlet channel, at which point the external circulation pump cannot pump liquid into the pipeline to be tested), open the second ball valve (open the return channel), the third ball valve, and the proportional control valve. The liquid in the pipeline to be tested is then blown back into the circulating water tank by compressed air.

[0076] For example, in this solution, the gas flow rate is precisely controlled according to the input signal by using a proportional control valve. It adjusts the flow rate by changing the valve opening, and there is a certain proportional relationship between the opening and the flow rate, thereby improving the energy utilization efficiency of the system.

[0077] Based on the aforementioned scheme where the external circulation unit of the water system includes an external circulation pump, in one possible implementation, the external circulation unit of the water system further includes: a first temperature sensor, a second temperature sensor, a first pressure sensor, a second pressure sensor, a flow meter, and a filter;

[0078] The first temperature sensor and the first pressure sensor are configured on the pipeline connecting the circulating water tank and the inlet of the pipeline to be tested.

[0079] The second temperature sensor, the second pressure sensor, the flow meter, and the filter are configured on the pipeline connecting the circulating water tank and the return port of the pipeline to be tested.

[0080] For example, in this solution, temperature sensors are installed on the inlet and return pipes respectively, so that the liquid temperature at the inlet and return ends can be obtained respectively. When testing the heat exchange performance, the inlet temperature, return temperature and other parameters (such as liquid flow rate, heat exchange area of ​​heat exchanger, etc.) are used together to calculate the heat exchange efficiency.

[0081] In addition, the temperature sensor in the liquid inlet pipeline can monitor in real time whether the liquid inlet temperature meets the test requirements. By monitoring the change in the liquid return temperature, it can be determined whether the reaction is proceeding as expected, whether it has been completed, or whether any abnormalities have occurred.

[0082] For example, in this solution, pressure sensors are installed on the inlet and return lines respectively, so that the liquid pressure at the inlet and return ends can be obtained respectively.

[0083] The pressure sensor at the inlet end can monitor the inlet pressure in real time to ensure that the liquid can enter the pipeline under test at a suitable pressure. In an automated liquid testing system, the control system can adjust the speed of the inlet pump (external circulation pump) or the opening of the specified valve by using the inlet pressure signal fed back by the pressure sensor, thereby achieving precise control of the liquid flow rate and meeting the liquid flow rate requirements during the testing phase.

[0084] During liquid circulation testing, changes in return pressure can reflect changes in resistance within the test system piping (the piping under test).

[0085] For example, when testing complex pipeline systems containing multiple devices such as filters and reactors, the resistance within the pipeline changes due to scaling, blockage, or changes in fluid conditions, which directly leads to changes in return pressure. By monitoring the return pressure, these problems can be detected in a timely manner, providing a basis for system maintenance and fault diagnosis.

[0086] For example, in this solution, the flow meter mainly detects the actual flow in the external circulation pipeline (the pipeline between the circulating water tank and the pipeline to be tested). Based on the actual flow and the flow target value set by the control system, the frequency (size) of the external circulation pump is controlled to change so that the actual flow is consistent with the flow target value.

[0087] Based on any of the aforementioned solutions, in one possible implementation, a heater is also provided inside the circulating water tank.

[0088] For example, in this solution, a heater is installed inside the circulating water tank. When it is necessary to heat the coolant in the circulating water tank, the heater can be activated to heat the coolant in the circulating water tank.

[0089] For example, in this solution, the type of heater configured in the circulating water tank is not limited; for example, the heater can be an electric heating element.

[0090] Based on the aforementioned scheme of equipping the circulating water tank with a heater, in one possible implementation, an expansion tank is also provided outside the circulating water tank.

[0091] For example, in this solution, when the coolant in the circulating water tank needs to be heated during testing, the volume of coolant in the circulating water tank increases as the coolant temperature rises. The expansion tank can accommodate this expansion, avoiding large fluctuations in water pressure due to the expansion of the coolant and ensuring the safe and stable operation of the system.

[0092] When the circulating water tank leaks or cools down for some reason, the water level in the expansion tank drops, which can replenish the circulating water tank in time to ensure that there is enough coolant in the circulating water tank to maintain normal circulation.

[0093] In this design, an expansion tank is connected to the top of the circulating water tank. Because the volume of coolant in the circulating water tank will expand and contract during the heating and cooling process, the expansion tank is used to adjust the coolant capacity in the circulating water tank.

[0094] Based on the aforementioned scheme of the water system external circulation unit including an external circulation pump, in one possible implementation, the water system external circulation unit is also equipped with a bypass valve, which is connected to the inlet and outlet of the circulating water tank respectively.

[0095] For example, in this solution, a bypass valve can be used to connect a branch of the inlet pipeline to the return pipeline, which serves as a bypass. The bypass valve 306 installed on this branch can be opened when the external circulation pipeline (the pipeline between the circulating water tank and the pipeline under test) requires a small flow rate, thus ensuring the stability of the flow rate and temperature supplied to the test component (the pipeline under test).

[0096] Based on any of the aforementioned schemes, in one possible implementation scheme, the high-temperature section refrigeration cycle unit is equipped with a first bypass pipeline unit, which is used for cooling the high-temperature section refrigeration cycle unit.

[0097] For example, in this solution, the first bypass pipeline unit may include a first bypass pipeline, and a solenoid valve may be configured in the first bypass pipeline. The opening and closing of the solenoid valve is controlled by the action of electromagnetic force to realize automatic control of the refrigerant flow in the first bypass pipeline.

[0098] In the cascade chiller unit, the control system sends signals to control the opening and closing of the solenoid valve based on parameters such as system temperature and pressure, thereby regulating the on / off state of the first bypass pipeline.

[0099] An expansion valve can also be configured in the first bypass pipeline. This expansion valve can be used to regulate the flow and pressure of the refrigerant so that the refrigerant can reach a suitable state before entering the high-temperature evaporator or other components. The expansion valve can throttle and reduce the pressure of the refrigerant as needed to control the flow of the refrigerant to meet the cooling requirements under different operating conditions.

[0100] Based on any of the aforementioned schemes, in one possible implementation scheme, the low-temperature refrigeration cycle unit is equipped with a second bypass pipeline unit, which is used for cooling the low-temperature refrigeration cycle unit.

[0101] For example, in this solution, the second bypass pipeline unit may include a second bypass pipeline, and a solenoid valve may be configured in the second bypass pipeline. The opening and closing of the solenoid valve is controlled by the action of electromagnetic force to realize automatic control of the refrigerant flow in the second bypass pipeline.

[0102] In the cascade chiller unit, the control system sends signals to control the opening and closing of the solenoid valve based on parameters such as system temperature and pressure, thereby regulating the on / off state of the second bypass pipeline.

[0103] An expansion valve can also be configured in the second bypass pipeline. The expansion valve can be used to regulate the flow and pressure of the refrigerant so that the refrigerant can reach a suitable state before entering the low-temperature evaporator or other components. The expansion valve can throttle and reduce the pressure of the refrigerant as needed to control the flow of the refrigerant to meet the refrigeration requirements under different operating conditions.

[0104] Figure 2 This is a schematic diagram of the cascade chiller system structure in the embodiment, for reference. Figure 2 Based on any of the aforementioned schemes, in one possible implementation scheme, the cascade chiller system includes:

[0105] Circulating water tank 303, expansion tank 304, external circulation pump 305, first ball valve 309, second ball valve 311, third ball valve 315, proportional regulating valve 316, bypass valve 306, first temperature sensor 307, second temperature sensor 313, first pressure sensor 308, second pressure sensor 312, flow meter 314, filter 310, heating element 001;

[0106] Heating element 001 is installed inside circulating water tank 303, and expansion tank 304 is installed on top of circulating water tank 303;

[0107] The outlet of the circulating water tank 303 is connected to the heat transfer medium supply port through the first ball valve 309. A first temperature sensor 307 and a first pressure sensor 308 are installed on the pipeline between the external circulation pump 305 and the first ball valve 309.

[0108] The heat transfer medium inlet and outlet are connected to the inlet of the circulating water tank 303 through filter 310 and second ball valve 311. A second pressure sensor 312, a second temperature sensor 313, and a flow meter 314 are installed on the pipeline between the second ball valve 311 and the inlet.

[0109] The bypass valve 306 is installed on the pipeline connecting the outlet of the external circulation pump 305 and the inlet of the circulation line 303.

[0110] It also includes an internal circulation pump 302 and a three-way valve 301;

[0111] It also includes a high-temperature refrigeration cycle unit, which includes:

[0112] The system comprises a high-temperature compressor 101, a first oil separator 102, a condenser 103, a first dryer filter 104, a sight glass 105, a first expansion valve 106, a high-temperature evaporator 107, a check valve 108, a first solenoid valve 116, a second expansion valve 109, a condenser-evaporator 110, and a gas-liquid separator 111.

[0113] It also includes a second solenoid valve 112, a first energy regulating valve 113, a third solenoid valve 114, and a first cooling expansion valve 115;

[0114] The outlet of the circulating water tank 303 is connected to the three-way valve 301 via the internal circulation pump 302, and the three-way valve 301 is connected to the high-temperature section evaporator 107.

[0115] The high-temperature section evaporator 107 is connected to the condenser evaporator 110 and the high-temperature compressor 101. The high-temperature compressor 101 forms a circulation loop with the high-temperature section evaporator 107 through the condenser 103.

[0116] The gas-liquid separator 111 is installed on the pipeline between the high-temperature section evaporator 107 and the high-temperature compressor 101, and the first oil separator 102 is installed on the pipeline between the high-temperature compressor 101 and the condenser 103.

[0117] The second solenoid valve 112 and the first energy regulating valve 113 are installed on the pipeline between the liquid outlet of the first oil separator 102 and the inlet of the gas-liquid separator 111. The second solenoid valve 112 and the first energy regulating valve 113 form a hot gas bypass pipeline to provide energy regulation for the high-temperature section system.

[0118] The third solenoid valve 114 and the first cooling expansion valve 115 are installed on the pipeline between the first outlet of the condenser 103 and the inlet of the gas-liquid separator 111. The third solenoid valve 114 and the first cooling expansion valve 115 form a cooling bypass pipeline to provide cooling for the high-temperature section system.

[0119] The first dryer filter 104 and the sight glass 105 are installed on the first outlet side of the condenser 103. The first outlet side of the condenser 103 is connected to the high-temperature section evaporator 107 through the first dryer filter 104, the sight glass 105, and the first expansion valve 106.

[0120] The cooling bypass pipeline, consisting of the third solenoid valve 114 and the first cooling expansion valve 115, is led out from the pipeline between the sight glass 105 and the first expansion valve 106.

[0121] The first outlet side of the condenser 103 is connected to the condenser-evaporator 110 via the first dryer filter 104 and the first solenoid valve 116 and the second expansion valve 109.

[0122] It also includes a low-temperature refrigeration cycle unit, which includes:

[0123] Low-temperature compressor 201, condenser 103, second oil separator 202, condenser-evaporator 110, second dryer filter 203, third expansion valve 204, low-temperature section evaporator 205;

[0124] The outlet of the circulating water tank 303 is connected to the three-way valve 301 through the internal circulation pump 302. The three-way valve 301 is connected to the low-temperature section evaporator 205. The low-temperature section evaporator 205, the low-temperature compressor 201, the condenser 103, and the condenser-evaporator 110 form a circulation loop.

[0125] The second dryer filter 203 and the third expansion valve 204 are installed on the pipeline between the outlet of the condenser evaporator 110 and the low-temperature section evaporator 205;

[0126] It also includes a fourth solenoid valve 206 and a second energy regulating valve 207. The fourth solenoid valve 206 and the second energy regulating valve 207 are installed on the pipeline between the outlet of the second oil separator 202 and the inlet of the cryogenic compressor 201. The fourth solenoid valve 206 and the second energy regulating valve 207 form a hot gas bypass pipeline to provide energy regulation for the high-temperature section system.

[0127] It also includes a fifth solenoid valve 208 and a second cooling expansion valve 209. The fifth solenoid valve 208 and the second cooling expansion valve 209 are installed on the pipeline between the second dryer filter 203 and the inlet of the low-temperature compressor 201. The fifth solenoid valve 208 and the second cooling expansion valve 209 form a cooling bypass pipeline to provide cooling for the high-temperature section system.

[0128] For example, in this solution, ethylene glycol solution is stored in the circulating water tank 303.

[0129] For example, in this solution, the cascade chiller system includes an internal circulation unit and an external circulation unit. The internal circulation unit is used to switch between the high-temperature section refrigeration cycle unit and the low-temperature section refrigeration cycle unit. The switching is performed through a three-way valve 301 according to the target value of the liquid supply temperature.

[0130] When the target value of the liquid supply temperature is greater than or equal to the set value, the pipeline of the three-way valve 301 is switched to the high-temperature section evaporator 107. The ethylene glycol solution in the circulating water tank 303 is exchanged with the high-temperature section evaporator 107 through the internal circulation pump 302 to reduce the temperature to the target value.

[0131] When the target value of the liquid supply temperature is less than the set value, the pipeline of the three-way valve 301 is switched to the low-temperature section evaporator 205. The ethylene glycol solution in the circulating water tank 303 is exchanged with the low-temperature section evaporator 205 through the internal circulation pump 302 to reduce the temperature to the target value.

[0132] The external circulation unit pumps the ethylene glycol solution in the circulating water tank 303 into the pipeline to be tested through the external circulation pump 305, thus forming a circulation.

[0133] The flow meter 314 mainly detects the actual flow rate in the external circulation pipeline. Based on the flow target value set by the control system, it controls the frequency of the external circulation pump 305 to keep the actual flow rate consistent with the target flow rate.

[0134] The outlet of the external circulation pump 305 is branched off and connected to the return pipeline of the circulating water tank 303, which serves as a bypass. A bypass valve 306 is installed on this branch. When the external circulation pipeline requires a small flow rate, the bypass valve 306 is opened to ensure the stability of the flow rate and temperature supplied to the test object.

[0135] An expansion tank 304 is connected to the top of the circulating water tank. Because the volume of the ethylene glycol solution in the system will expand and contract during the heating and cooling process, it needs to be adjusted through the expansion tank 304.

[0136] After the test, a purging function was set up to ensure that the liquid in the boiler under test could return to the unit and prevent leakage in the pipeline.

[0137] By closing the first ball valve 309 and opening the second ball valve 311, the external compressed air is introduced into the liquid supply pipeline through the proportional regulating valve 316 and the third ball valve 315, and the liquid in the pipeline to be tested is blown back into the circulating water tank 303 using compressed air.

[0138] An electric heating element 001 is installed in the circulating water tank 303. When the control system needs to raise the temperature, the electric heating element 001 is activated to heat the ethylene glycol solution in the circulating water tank.

[0139] For example, in this solution, the basic working principles of the high-temperature refrigeration cycle unit and the low-temperature refrigeration cycle unit are the same as those described above.

[0140] Among them, the high-temperature compressor 101 is mainly used to compress the refrigerant, increase the pressure and temperature of the refrigerant, so that it can flow in the high-temperature section and transfer heat to the cooling medium;

[0141] The first oil separator 102 is used to separate the lubricating oil carried in the refrigerant discharged from the high-temperature compressor 101, so as to prevent the oil from entering the condenser and other components and affecting the heat exchange efficiency.

[0142] The condenser 103 is used to condense and release heat in the high-temperature and high-pressure refrigerant gas, and transfer the heat to the external cooling medium (usually air or water), so that the refrigerant changes from a gaseous state to a liquid state.

[0143] The first dryer filter 104 filters impurities and moisture from the refrigerant;

[0144] The sight glass 105 is used to facilitate operators to observe the flow state of the refrigerant and the presence of bubbles, thereby determining whether the refrigeration system is working properly, such as whether the refrigerant is sufficient.

[0145] The first expansion valve 106 is used to throttle and reduce the pressure of the high-pressure liquid refrigerant coming out of the condenser 103, thereby reducing the refrigerant pressure and temperature and controlling the refrigerant flow rate into the high-temperature section evaporator 107.

[0146] The high-temperature section evaporator 107 is used to evaporate and absorb heat in the low-pressure liquid refrigerant, thereby lowering the temperature of the medium being cooled (such as water), and changing the refrigerant from a liquid state to a gaseous state, thus completing the refrigeration process.

[0147] The check valve 108 is used to prevent refrigerant backflow, ensuring that the refrigerant flows in the predetermined direction and guaranteeing the normal operation of the high-temperature refrigeration cycle;

[0148] The first solenoid valve 116 is used to open or close the refrigerant flow path by electromagnetic control, and can control the refrigerant flow direction according to the system's operating requirements, such as when starting, stopping or switching operating modes.

[0149] The second expansion valve 109 is used to throttle and reduce the pressure of the refrigerant, and control the flow rate of the refrigerant entering the condenser-evaporator 110;

[0150] The condenser-evaporator 110 is used as a heat exchanger between the high-temperature section and the low-temperature section. The refrigerant in the high-temperature section condenses and releases heat, transferring the heat to the refrigerant in the low-temperature section, causing the refrigerant in the low-temperature section to evaporate and absorb heat.

[0151] The gas-liquid separator 111 is used to separate the refrigerant from the condenser evaporator 110 or the high-temperature section evaporator 107 into gas and liquid, to prevent liquid refrigerant from entering the high-temperature compressor 101 and causing liquid slugging, and to ensure that gaseous refrigerant enters the compressor, thus protecting the high-temperature compressor 101.

[0152] The cryogenic compressor 201 is used to compress the refrigerant in the cryogenic range, increase its pressure and temperature, so that it can flow in the cryogenic range to realize the refrigeration cycle;

[0153] The second oil separator 202 is used to separate the oil in the refrigerant discharged from the low-temperature compressor to prevent it from entering components such as the condenser and evaporator.

[0154] The dryer filter 203 is used to filter impurities and moisture in the refrigerant in the low-temperature section, ensuring the normal operation of the low-temperature refrigeration system and preventing impurities from clogging and moisture from freezing.

[0155] The third expansion valve 204 is used to throttle and reduce the pressure of the refrigerant coming out of the condenser-evaporator, and control the flow rate of the refrigerant entering the low-temperature section evaporator 205, so that the refrigerant can evaporate and absorb heat normally in the low-temperature section evaporator 205.

[0156] The low-temperature section evaporator 205 is used for the evaporation and heat absorption of low-pressure liquid refrigerant, which allows the cooled medium to reach a lower temperature. The refrigerant changes from a liquid state to a gas state, thus achieving low-temperature refrigeration.

[0157] In this design, the high-temperature refrigeration cycle unit and the low-temperature refrigeration cycle unit constitute a cascade refrigeration system. The limiting evaporation temperature of a single-stage compression system is -45℃, while the limiting evaporation temperature of the cascade refrigeration system can reach -70℃ or even lower. The cooling capacity of the single-stage compression system decreases significantly at the limiting evaporation temperature of -45℃, while the cooling capacity of the cascade refrigeration system decreases less at low temperatures. Therefore, when the temperature drops from -20℃ to -40℃ in the low-temperature section, the rate of cooling using a single-stage compression system is very slow, only reaching about 1℃ / min, while the cascade system can achieve a rate of over 4℃ / min. In this design, the high-temperature refrigeration cycle unit includes a high-temperature evaporator, enabling the cascade refrigeration system to achieve its maximum cooling capacity even above 0℃.

[0158] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A cascade chiller system, characterized in that, include: Circulating water tank, internal water system circulation unit, external water system circulation unit, high-temperature section refrigeration circulation unit, low-temperature section refrigeration circulation unit; The circulating water tank is connected to the high-temperature section refrigeration circulation unit and the low-temperature section refrigeration circulation unit respectively through the internal circulation unit of the water system; The circulating water tank is connected to the pipeline to be tested through the external circulation unit of the water system; The circulating water tank delivers a solution to the high-temperature section refrigeration cycle unit or the low-temperature section refrigeration cycle unit through the internal circulation unit of the water system, and the solution achieves heat exchange through the high-temperature section refrigeration cycle unit or the low-temperature section refrigeration cycle unit; The circulating water tank supplies a solution to the pipeline under test through the external circulation unit of the water system, and the solution is used for testing the pipeline.

2. The cascade chiller system as described in claim 1, characterized in that, The water system internal circulation unit includes an internal circulation pump and a three-way valve; The circulating water tank is connected to the three-way valve via the internal circulation pump, and the three-way valve is connected to the liquid inlet of the high-temperature section refrigeration cycle unit and the low-temperature section refrigeration cycle unit. The outlets of the high-temperature refrigeration cycle unit and the low-temperature refrigeration cycle unit are connected to the circulating water tank.

3. The cascade chiller system as described in claim 1, characterized in that, The water system external circulation unit includes an external circulation pump; The circulating water tank is connected to the inlet of the pipeline under test via the external circulation pump, and the return port of the pipeline under test is connected to the circulating water tank.

4. The cascade chiller system as described in claim 3, characterized in that, The external circulation unit of the water system also includes: a first ball valve, a second ball valve, a third ball valve, and a proportional regulating valve; The first ball valve is configured on the pipeline connecting the circulating water tank and the inlet of the pipeline to be tested, and is used to open or close the inlet channel; The second ball valve is configured on the pipeline connecting the circulating water tank and the return port of the pipeline to be tested, and is used to open or close the return channel; The third ball valve and the proportional regulating valve are configured on the pipeline connecting the circulating water tank to the inlet of the pipeline to be tested. The third ball valve and the proportional regulating valve are connected to the air source and are used to open or close the air source channel.

5. The cascade chiller system as described in claim 3, characterized in that, The water system external circulation unit also includes: a first temperature sensor, a second temperature sensor, a first pressure sensor, a second pressure sensor, a flow meter, and a filter; The first temperature sensor and the first pressure sensor are disposed on the pipeline connecting the circulating water tank and the inlet of the pipeline to be tested; The second temperature sensor, the second pressure sensor, the flow meter, and the filter are configured on the pipeline connecting the circulating water tank and the return port of the pipeline to be tested.

6. The cascade chiller system as described in claim 1, characterized in that, The circulating water tank is also equipped with a heater.

7. The cascade chiller system as described in claim 6, characterized in that, An expansion tank is also provided outside the circulating water tank.

8. The cascade chiller system as described in claim 3, characterized in that, The external circulation unit of the water system is also equipped with a bypass valve, which is connected to the inlet and outlet of the circulating water tank respectively.

9. The cascade chiller system as described in claim 1, characterized in that, The high-temperature section refrigeration cycle unit is equipped with a first bypass pipeline unit, which is used for cooling the high-temperature section refrigeration cycle unit.

10. The cascade chiller system as described in claim 1, characterized in that, The low-temperature refrigeration cycle unit is equipped with a second bypass pipeline unit, which is used for cooling the low-temperature refrigeration cycle unit.

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