Cascade refrigeration system and refrigerator

Abstract

The application relates to a cascade refrigeration system and a refrigerator, the cascade refrigeration system comprising a Stirling refrigeration part, an evaporation refrigeration part and an inner low-temperature chamber, the cascade refrigeration system being provided with an outer refrigeration cavity, the Stirling refrigeration part, the evaporation refrigeration part and the inner low-temperature chamber being arranged in the outer refrigeration cavity, the evaporation refrigeration part being capable of refrigerating in the outer refrigeration cavity, the inner low-temperature chamber being provided with a valve structure communicating with the outer refrigeration cavity, so that the cold energy in the outer refrigeration cavity can enter the inner low-temperature chamber through the valve structure, the side wall of the inner low-temperature chamber and the outer refrigeration cavity being heat-insulated, the cold end of the Stirling refrigeration part being heat-conductively connected to the inner wall of the inner low-temperature chamber, and the hot end of the Stirling refrigeration part being heat-conductively connected to the evaporation refrigeration part. The cascade refrigeration system and the refrigerator provided by the application solve the problem that the refrigerating capacity generated by the Stirling refrigerator of the existing refrigerator is limited, and a special heat dissipation device is needed to dissipate heat for the Stirling refrigerator.

Description

Technical Field

[0001] This application relates to the field of refrigerator technology, and in particular to a cascade refrigeration system and a refrigerator. Background Technology

[0002] Traditional refrigerators typically use mixed refrigerants to achieve deep cooling, but this method is noisy, and the lowest temperature achievable is only around -40°C. Furthermore, mixed refrigerant systems require advanced manufacturing technology, necessitating storage devices for both types of refrigerants. To overcome these technical challenges, current technology often employs Stirling engines for refrigeration. However, a single Stirling engine has limited cooling capacity and requires dedicated cooling systems, resulting in larger and more expensive refrigerators. Utility Model Content

[0003] Therefore, it is necessary to provide a cascade refrigeration system and refrigerator to solve the problems of limited cooling capacity generated by existing refrigerators using Stirling refrigeration and the need for a dedicated heat dissipation device to cool the Stirling engine.

[0004] The cascade refrigeration system provided in this application includes a Stirling refrigeration section, an evaporative refrigeration section, and an inner low-temperature chamber. The cascade refrigeration system has an outer refrigeration chamber, and the Stirling refrigeration section, evaporative refrigeration section, and inner low-temperature chamber are all located in the outer refrigeration chamber. The evaporative refrigeration section can perform refrigeration in the outer refrigeration chamber. The inner low-temperature chamber has a valve structure that connects to the outer refrigeration chamber, so that the cold energy in the outer refrigeration chamber can enter the inner low-temperature chamber through the valve structure. The side wall of the inner low-temperature chamber and the outer refrigeration chamber are thermally insulated. The cold end of the Stirling refrigeration section is thermally connected to the inner wall of the inner low-temperature chamber, and the hot end of the Stirling refrigeration section is thermally connected to the evaporative refrigeration section.

[0005] In one embodiment, the cascade refrigeration system further includes a controller. When the temperature of the inner low-temperature chamber is higher than the first target temperature, the controller can control the valve structure to open and cause the evaporative refrigeration unit to deliver cold air to the inner low-temperature chamber through the valve structure. When the temperature of the inner low-temperature chamber reaches the first target temperature and remains there for a preset time, the controller can control the valve structure to close and control the Stirling refrigeration unit to start working, so that the temperature of the inner low-temperature chamber reaches a second target temperature, which is lower than the first target temperature.

[0006] In one embodiment, a heating element is provided at the evaporator coil of the evaporative cooling unit. When the Stirling cooling unit is running and the temperature of the evaporator coil of the evaporative cooling unit is equal to the defrosting start temperature, the controller can control the heating element to heat the evaporative cooling unit so that the temperature of the evaporator coil of the evaporative cooling unit reaches the standard defrosting temperature. The standard defrosting temperature is greater than or equal to 0°C, the defrosting start temperature is lower than the first target temperature, and the defrosting start temperature is higher than the second target temperature.

[0007] In one embodiment, when the Stirling refrigeration unit is operating and the evaporator coil temperature of the evaporative refrigeration unit is higher than the defrosting start temperature, in the first operating condition, when the temperature at the hot end of the Stirling refrigeration unit is higher than a preset upper limit temperature, the controller can control the Stirling refrigeration unit to operate at a first power, which is less than the rated power of the Stirling refrigeration unit; the controller can also control the evaporative refrigeration unit to operate at a second power, which is greater than the rated power of the evaporative refrigeration unit, so that the evaporator coil temperature of the evaporative refrigeration unit reaches the defrosting start temperature; in the second operating condition, when the temperature at the hot end of the Stirling refrigeration unit is less than or equal to the preset upper limit temperature, and the internal cavity temperature of the inner low-temperature chamber and the second target... When the temperature difference is greater than the preset temperature difference, the controller can control the Stirling refrigeration unit to operate at its rated power, and the controller can also control the evaporative refrigeration unit to operate at its second power, so that the evaporator coil temperature of the evaporative refrigeration unit reaches the defrosting start temperature; in the third operating condition, when the difference between the inner cavity temperature of the inner low temperature chamber and the second target temperature is less than or equal to the preset temperature difference, the controller can control the Stirling refrigeration unit to operate at its third power, which is less than the first power, and the controller can also control the evaporative refrigeration unit to operate at its fourth power, which is less than the rated power of the evaporative refrigeration unit, so that the evaporator coil temperature of the evaporative refrigeration unit reaches the defrosting start temperature.

[0008] In one embodiment, the hot end of the Stirling refrigeration unit is provided with a second fan. When the Stirling refrigeration unit is running and the temperature of the evaporator coil of the evaporative refrigeration unit is equal to the defrosting start temperature, the controller can control the second fan to run so that the heat at the hot end of the Stirling refrigeration unit can be transferred to the evaporative refrigeration unit through the airflow formed by the second fan.

[0009] In one embodiment, the inner low-temperature chamber includes an insulation shell, a heat-conducting plate, and a heat-conducting block. The insulation shell is disposed on the outer side of the inner low-temperature chamber to isolate the heat transfer between the inner low-temperature chamber and the outer refrigeration chamber. The heat-conducting plate is disposed on the inner side of the inner low-temperature chamber. The heat-conducting block is sandwiched between the insulation shell and the heat-conducting plate. The cold end of the Stirling refrigeration unit is provided with a first heat-conducting pipe. The heat-conducting block is thermally connected to the cold end of the Stirling refrigeration unit through the first heat-conducting pipe, so that the cold energy of the cold end of the Stirling refrigeration unit can be transferred to the inner low-temperature chamber in sequence through the first heat-conducting pipe, the heat-conducting block, and the heat-conducting plate.

[0010] In one embodiment, the hot end of the Stirling refrigeration unit is provided with a second heat pipe, the two ends of which are thermally connected to the hot end of the Stirling refrigeration unit and the evaporative refrigeration unit, respectively, so that the heat of the hot end of the Stirling refrigeration unit can be transferred to the evaporative refrigeration unit through the second heat pipe.

[0011] In one embodiment, the second heat pipe is spirally arranged around the hot end of the Stirling cooling section.

[0012] In one embodiment, the cascade cooling system further includes a first fan disposed in the outer cooling chamber to enable the gas in the outer cooling chamber to circulate.

[0013] This application also provides a refrigerator that includes the cascade refrigeration system described in any of the above embodiments.

[0014] Compared with existing technologies, the cascade refrigeration system and refrigerator provided in this application, specifically, during operation, the evaporative cooling unit first cools the outer cooling chamber. When the temperature inside the outer cooling chamber reaches a set value, the valve structure opens to allow cold air to enter the inner low-temperature chamber. Once the temperature of the inner low-temperature chamber drops to the initial target value, the Stirling cooling unit activates. Its cold end deeply cools the inner low-temperature chamber through a heat conduction path, while the heat generated at the hot end is transferred to the evaporative cooling unit through a heat conduction connection, utilizing the heat dissipation capacity of the evaporative cooling system to achieve heat release. The insulation structure ensures that the inner low-temperature chamber maintains a stable ultra-low temperature environment during the Stirling cooling stage, preventing the intrusion of external heat.

[0015] Compared to existing technologies, traditional Stirling engines require a separate cooling system. This solution integrates the cooling requirements of the Stirling cooling unit into the evaporative cooling unit through a thermally conductive connection between the hot end and the evaporative cooling section, effectively reducing the need for additional cooling components. Existing mixed refrigerant systems require complex piping and storage devices; this solution simplifies refrigerant management through a cascade structure, achieving multi-stage cooling with only a single refrigerant.

[0016] Through the above technical solution, this application achieves efficient synergy between two refrigeration systems, significantly reducing equipment size while ensuring ultra-low temperature cooling capacity. The heat from the Stirling refrigeration unit is directly handled by the evaporative refrigeration unit, avoiding the need for dedicated heat dissipation devices and reducing manufacturing costs. The combined use of valve structure and insulation design enables the system to automatically switch operating modes at different temperature stages, improving overall energy efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A partial structural diagram of a cascade cooling system according to an embodiment of this application. Figure 1 ;

[0019] Figure 2 A partial structural diagram of a cascade cooling system according to an embodiment of this application. Figure 2 ;

[0020] Figure 3 A partial structural diagram of a cascade cooling system according to an embodiment of this application. Figure 3 ;

[0021] Figure 4 A partial structural diagram of a cascade cooling system according to an embodiment of this application. Figure 4 .

[0022] Reference numerals: 100, Stirling cooling section; 110, cold end; 120, first heat pipe; 130, hot end; 140, second heat pipe; 150, second fan; 200, evaporative cooling section; 210, evaporator coil; 300, inner low-temperature chamber; 310, heat insulation shell; 320, heat-conducting plate surface; 330, heat-conducting block; 340, valve structure; 341, inlet valve; 342, outlet valve; 400, outer shell; 410, outer cooling cavity. Detailed Implementation

[0023] Please see Figures 1-4 This application provides a cascade refrigeration system, which includes a Stirling refrigeration unit 100, an evaporative refrigeration unit 200, and an inner low-temperature chamber 300. The outer casing 400 of the cascade refrigeration system has an outer refrigeration chamber 410, and the Stirling refrigeration unit 100, the evaporative refrigeration unit 200, and the inner low-temperature chamber 300 are all disposed within the outer refrigeration chamber 410. In other words, the cascade refrigeration system of this application includes two layers of refrigeration space: the outer refrigeration chamber 410 and the inner low-temperature chamber 300. Furthermore, the inner low-temperature chamber 300 can further reduce the indoor temperature based on the outer refrigeration chamber 410, thereby achieving ultra-low temperature refrigeration (below -40°C) of the cascade refrigeration system.

[0024] The evaporative refrigeration section 200 provides refrigeration to the external refrigeration chamber 410. Specifically, the evaporative refrigeration section 200 is a closed loop that circulates a special liquid called "refrigerant" (formerly Freon, now mostly environmentally friendly refrigerants such as R600a). This cycle mainly includes the following four steps: compression, condensation, throttling (expansion), and evaporation. The compression process involves the compressor drawing in low-temperature, low-pressure gaseous refrigerant that has absorbed heat and vaporized from the evaporator. The compressor then performs work on the low-temperature, low-pressure gaseous refrigerant, compressing it violently and transforming it into a high-temperature, high-pressure gaseous refrigerant. The condensation process involves the high-temperature, high-pressure gaseous refrigerant being pumped into the condenser coil. Because the refrigerant's temperature is much higher than the room temperature outside the refrigerator, it dissipates heat to the surrounding air through the condenser coil. As heat is lost, the refrigerant condenses from a gaseous state into a medium-temperature, high-pressure liquid state. The throttling step involves the high-pressure liquid refrigerant flowing through a very thin tube (called a capillary tube) or an expansion valve. This device acts like a checkpoint, greatly... The capillary tube restricts the flow of refrigerant, acting as a "throttling" and "pressure reduction" mechanism. After exiting the capillary tube, the refrigerant pressure drops sharply, and its temperature also decreases rapidly, transforming into a low-temperature, low-pressure liquid (mixed with a small amount of gas) mist-like mixture. The evaporation process is as follows: the low-temperature, low-pressure mist-like refrigerant enters the evaporator coil 210 (the main structure of the evaporative refrigeration unit 200 in this application) installed in the freezer compartment (the external refrigeration chamber 410 in this application). Due to the extremely low pressure, the boiling point of the refrigerant also becomes very low, causing it to evaporate violently within the evaporator coil 210, rapidly changing from a liquid to a gaseous state. Since the evaporation process requires the absorption of a large amount of heat, which is taken from the air and food in the freezer and refrigerator compartments, the temperature inside the external refrigeration chamber 410 drops. It should be noted that after absorbing heat, the refrigerant returns to a low-temperature, low-pressure gaseous state and is then drawn back into the compressor waiting at the start of the cycle to begin a new cycle.

[0025] like Figure 2 and Figure 4 As shown, the inner low-temperature chamber 300 is equipped with a valve structure 340 that is specifically connected to the outer refrigeration chamber 410, so that the cold energy (mainly carried by cold air) in the outer refrigeration chamber 410 can enter the inner low-temperature chamber 300 through the valve structure 340. When the temperature of the inner low-temperature chamber 300 drops to the same level as or similar to that of the outer refrigeration chamber 410, the valve structure 340 will close to prevent the cold energy from being lost into the outer refrigeration chamber 410 after the temperature of the inner low-temperature chamber 300 continues to drop.

[0026] Specifically, in one embodiment, the valve structure 340 includes an inlet valve 341 and an outlet valve 342. The inlet valve 341 is a motor-controlled door switch, or it can be a solenoid valve or other regulating valve. Cold air from the external cooling chamber 410 can enter the internal low-temperature chamber 300 through the inlet valve 341. The outlet valve 342 is a one-way valve, or it can be a gravity valve that opens and closes by gravity. The upper end of the gravity valve is hinged to the upper sidewall of the outlet, while the lower end of the gravity valve is free to move. When the air pressure in the internal low-temperature chamber 300 exceeds a certain value, the gravity valve will automatically open under the action of the pressure difference. When the pressure difference decreases, the gravity valve will automatically close. However, this is not a limitation. In other embodiments, the inlet and outlet of the valve structure 340 can also be the same opening.

[0027] In one embodiment, the cascade refrigeration system further includes a first fan (not shown), which is disposed in the outer refrigeration chamber 410 to enable gas circulation within the outer refrigeration chamber 410 and to accelerate the entry of the low-temperature gas from the outer refrigeration chamber 410 into the inner low-temperature chamber 300, thereby accelerating the cooling of the inner low-temperature chamber 300. Specifically, when the Stirling refrigeration unit 100 and the evaporative refrigeration unit 200 operate simultaneously, the first fan is configured to start and form a gas circulation. For example, when the fan operates, it drives the flow of low-temperature gas within the outer refrigeration chamber 410, rapidly transferring the cooling energy generated by the cold end 110 of the Stirling refrigeration unit 100 to the inner low-temperature chamber 300.

[0028] It is important to note that the side walls of the inner low-temperature compartment 300 and the outer cooling cavity 410 are insulated. That is, the side walls of the inner low-temperature compartment 300 are made of insulating material to prevent direct heat transfer between the inner low-temperature compartment 300 and the outer cooling cavity 410, thereby helping to maintain the temperature difference between them. Specifically, to achieve maximum energy efficiency and storage space, the side walls of the inner low-temperature compartment 300 can use vacuum insulation panels. The superior insulation capacity of vacuum insulation panels effectively reduces cold air loss, contributing to energy savings in the long run. Furthermore, the thinner vacuum insulation panels significantly increase the effective volume of the refrigerator. Of course, from the perspective of prioritizing cost-effectiveness and reliability, traditional polyurethane (PU) foam is also a very reliable choice for the side walls of the inner low-temperature compartment 300. Furthermore, in other embodiments, in order to cope with special or complex structures, such as when the partition layer needs to simultaneously provide structural support or has a particular emphasis on sound insulation, the sidewall of the inner low-temperature greenhouse 300 can also adopt a composite thermal insulation structure (such as adding a perlite layer). The composite thermal insulation structure can provide stronger overall structural integrity and better sound insulation.

[0029] like Figure 2 and Figure 4As shown, the cold end 110 of the Stirling refrigeration unit 100 is thermally connected to the inner wall of the inner low-temperature chamber 300, and the hot end 130 of the Stirling refrigeration unit 100 is thermally connected to the evaporative refrigeration unit 200. It should be noted that the Stirling refrigeration unit 100 is a gas regenerative refrigerator operating under a reverse Stirling cycle. Its core principle is to periodically compress, cool, expand, and heat the working gas (usually helium) within a closed system, and to efficiently transfer heat using a regenerator, thereby generating a low temperature at the expansion end (i.e., the cold end 110 in this application). Specifically, the Stirling refrigeration unit 100 forces the working gas to reciprocate between the hot end 130 and the cold end 110 via mechanical drive (compression piston and discharge device), and forces it to flow through the regenerator. At the hot end 130, the gas is compressed and cooled to ambient temperature (ambient temperature in this application is the temperature of the outer refrigeration chamber 410). In the cold chamber, the gas expands, cools, and absorbs heat (refrigeration). The regenerator efficiently recovers and reuses the heat inside the system, allowing the expansion process to take place at temperatures far below ambient, thus continuously generating cooling.

[0030] Specifically, during the operation of the cascade refrigeration system, the evaporative cooling unit 200 first cools the outer cooling chamber 410. When the temperature inside the outer cooling chamber 410 reaches the set value, the valve structure 340 opens to allow cold air to enter the inner low-temperature chamber 300. Once the temperature of the inner low-temperature chamber 300 drops to the initial target value, the Stirling cooling unit 100 starts up. Its cold end 110 deeply cools the inner low-temperature chamber 300 through a heat conduction path, while the heat generated by the hot end 130 is transferred to the evaporative cooling unit 200 through a heat conduction connection, utilizing the heat dissipation capacity of the evaporative refrigeration system to achieve heat release. The insulation structure ensures that the inner low-temperature chamber 300 maintains a stable ultra-low temperature environment during the Stirling cooling stage, preventing the intrusion of external heat.

[0031] Compared to existing technologies, traditional Stirling engines require independent cooling systems. This solution integrates the cooling requirements of the Stirling cooling unit 100 into the evaporative cooling unit 200 through a thermally conductive connection between the hot end 130 and the evaporative cooling unit 200, effectively reducing the need for additional cooling components. Existing mixed refrigerant systems require complex piping and storage devices. This solution simplifies refrigerant management through a cascade structure, achieving multi-stage cooling with only a single refrigerant.

[0032] Through the above technical solution, this application achieves efficient synergy between two refrigeration systems, significantly reducing equipment size while ensuring ultra-low temperature refrigeration capacity. The heat from the Stirling refrigeration unit 100 is directly handled by the evaporative refrigeration unit 200, avoiding the need for a dedicated heat dissipation device and reducing manufacturing costs. The combined use of the valve structure 340 and the thermal insulation design enables the system to automatically switch operating modes at different temperature stages, improving overall energy efficiency.

[0033] In one embodiment, such as Figure 2 and Figure 4 As shown, the inner low-temperature chamber 300 includes a heat-insulating shell 310, a heat-conducting plate surface 320, and a heat-conducting block 330. The heat-conducting plate surface 320 and the heat-conducting block 330 are made of various materials, including but not limited to metal blocks and heat-conducting ceramics. The heat-insulating shell 310 is disposed on the outer side of the inner low-temperature chamber 300 to isolate the heat transfer between the inner low-temperature chamber 300 and the outer cooling chamber 410. The heat-conducting plate surface 320 is disposed on the inner side of the inner low-temperature chamber 300, and the heat-conducting block 330 is sandwiched between the heat-insulating shell 310 and the heat-conducting plate surface 320. Furthermore, the cold end 110 of the Stirling refrigeration unit 100 is provided with a first heat pipe 120, which contains a working fluid capable of phase change heat transfer. A heat-conducting block 330 is thermally connected to the cold end 110 of the Stirling refrigeration unit 100 via the first heat pipe 120, allowing the cooling energy from the cold end 110 of the Stirling refrigeration unit 100 to be sequentially transferred to the inner low-temperature chamber 300 via the first heat pipe 120, the heat-conducting block 330, and the heat-conducting plate surface 320. Specifically, the cooling energy generated by the Stirling refrigeration unit 100 is transferred to the heat-conducting block 330 via the first heat pipe 120, the heat-conducting block 330 evenly diffuses the cooling energy to the heat-conducting plate surface 320, and the heat-conducting plate surface 320 further conducts the cooling energy to the interior space of the inner low-temperature chamber 300. The heat-insulating shell 310 prevents external heat from entering the inner low-temperature chamber 300 by blocking heat exchange between the outer refrigeration chamber 410 and the inner low-temperature chamber 300. The heat-conducting block 330, as an intermediate heat transfer medium, can effectively reduce heat loss during the cold transfer process and alleviate stress concentration caused by the difference in the thermal expansion coefficients of materials.

[0034] Specifically, the first heat pipe 120 is approximately U-shaped. The liquid working fluid inside the first heat pipe 120 absorbs heat at the heat-conducting block 330 and vaporizes into a gaseous working fluid. Then, the gaseous working fluid moves to the cold end 110 of the Stirling refrigeration section 100 and releases heat to liquefy, thereby realizing the transfer of cold energy between the cold end 110 of the Stirling refrigeration section 100 and the inner low temperature chamber 300.

[0035] In one embodiment, the hot end 130 of the Stirling refrigeration unit 100 is provided with a second heat pipe 140. The second heat pipe 140 contains a working fluid capable of phase change heat transfer. Both ends of the second heat pipe 140 are thermally connected to the hot end 130 of the Stirling refrigeration unit 100 and the evaporator coil 210 of the evaporative refrigeration unit 200, respectively, so that the heat from the hot end 130 of the Stirling refrigeration unit 100 can be transferred to the evaporative refrigeration unit 200 through the second heat pipe 140. Specifically, during operation, the heat generated by the hot end 130 of the Stirling refrigeration unit 100 is directly transferred to the evaporative refrigeration unit 200 through the second heat pipe 140. For example, one end of the second heat pipe 140 is tightly attached to the surface of the hot end 130 of the Stirling refrigeration unit 100, and the other end extends to the heat exchange area of ​​the evaporative refrigeration unit 200. When the Stirling refrigeration unit 100 is operating, the heat from the hot end 130 is efficiently conducted to the evaporative refrigeration unit 200 through the second heat pipe 140. At this time, the evaporative refrigeration unit 200 can dissipate the heat outside the system through its own refrigeration cycle. Thus, the heat dissipation requirements of the Stirling refrigeration unit 100 are met through the synergistic effect of the second heat pipe 140 and the evaporative refrigeration unit 200, without the need for an additional dedicated heat dissipation device.

[0036] Specifically, the liquid working fluid in the second heat pipe 140 absorbs heat at the hot end 130 of the Stirling refrigeration section 100 and vaporizes into a gaseous working fluid. Then, the gaseous working fluid moves to the evaporative refrigeration section 200 and releases heat to liquefy, thereby realizing the heat transfer between the hot end 130 of the Stirling refrigeration section 100 and the evaporative refrigeration section 200.

[0037] Furthermore, in one embodiment, as Figure 2 As shown, the second heat pipe 140 is spirally wound around the hot end 130 of the Stirling refrigeration section 100. The second heat pipe 140 can be directly welded to the evaporator coil 210, or it can be wound around and connected to the evaporator coil 210. Specifically, both ends of the second heat pipe 140 are thermally connected to the hot end 130 of the Stirling refrigeration section 100 and the evaporative refrigeration section 200, respectively. When the Stirling refrigeration section 100 is operating, the heat generated at its hot end 130 is transferred to the evaporative refrigeration section 200 through the second heat pipe 140. Because the second heat pipe 140 is spirally wound around the surface of the hot end 130, its contact area with the hot end 130 is significantly increased, thereby absorbing heat more efficiently. At the same time, the spiral structure can extend the heat transfer path within the heat pipe, allowing heat to be distributed more evenly to the evaporative refrigeration section 200 and avoiding localized overheating. The evaporative cooling unit 200 maintains its operation by absorbing this heat, for example, by using this heat to raise the temperature of the evaporator coil 210 during defrosting. Thus, the heat dissipation requirements of the Stirling cooling unit 100 are met by the evaporative cooling unit 200, eliminating the need for an additional dedicated heat dissipation device.

[0038] Compared with existing technologies, this solution directly connects the hot end 130 of the Stirling refrigeration section 100 to the evaporative refrigeration section 200 through a spiral second heat pipe 140, using the evaporative refrigeration section 200 as the heat dissipation medium, which simplifies the structure and reduces heat dissipation energy consumption. In addition, the spirally wound second heat pipe 140 can significantly improve heat conduction efficiency by increasing the contact area and extending the heat transfer path compared with straight pipes or simple curved structures.

[0039] However, this is not the only one. In other embodiments, the second heat pipe 140 may also be in various shapes such as wavy or straight, which will not be listed here.

[0040] In one embodiment, the cascade refrigeration system further includes a controller (not shown). When the temperature of the outer refrigeration chamber 410 is higher than a first target temperature (typically between -10°C and -30°C, preferably -28°C), the controller controls the evaporative refrigeration unit 200 to start refrigeration. When the temperature of the outer refrigeration chamber 410 equals the first target temperature, the controller controls the valve structure 340 to open, allowing cold air to enter the inner low-temperature chamber 300. When the temperature inside the inner low-temperature chamber 300 is higher than the first target temperature, the controller can control the valve structure 340 to open, and the evaporative refrigeration unit 200 to deliver cold air to the inner low-temperature chamber 300 through the valve structure 340. When the temperature inside the inner low-temperature chamber 300 reaches the first target temperature and remains there for a preset time, the controller can control the valve structure 340 to close and control the Stirling refrigeration unit 100 to start working, so that the inner cavity of the inner low-temperature chamber 300 reaches a second target temperature (typically between -45°C and -55°C, preferably -50°C). The second target temperature is lower than the first target temperature, and the first target temperature is lower than -10°C. Specifically, when the temperature sensor detects that the temperature of the inner low-temperature chamber 300 is higher than the first target temperature, the controller sends an opening signal to the solenoid valve and simultaneously starts the compressor of the evaporative cooling unit 200, allowing the cold air generated by the external cooling chamber 410 to enter the inner low-temperature chamber 300 through the air duct. During this stage, the Stirling cooling unit 100 remains closed, and the evaporative cooling unit 200 undertakes the cooling task alone. When the temperature of the inner low-temperature chamber 300 drops to the first target temperature and is maintained for a preset time, the controller closes the solenoid valve to block the cold air delivery and simultaneously starts the Stirling cooling unit 100. At this time, the cold end 110 of the Stirling cooling unit 100 acts directly on the inner wall of the inner low-temperature chamber 300, using its low-temperature cooling capacity to further reduce the temperature to a lower second target temperature.

[0041] Compared with existing technologies, this solution employs a phased control strategy, prioritizing the use of the evaporative cooling unit 200 for rapid cooling during the high-temperature phase, and only activating the Stirling cooling unit 100 after reaching the intermediate temperature threshold, significantly reducing the operating time of the Stirling engine. Simultaneously, the opening and closing control of the valve structure 340 avoids energy conflicts when the two cooling modes operate simultaneously, resolving the overheating problem caused by insufficient heat dissipation in traditional solutions.

[0042] Through the above technical solution, this application achieves efficient and coordinated operation of the refrigeration system. The evaporative cooling unit 200 rapidly reduces the temperature of the inner low-temperature chamber 300 during the high-temperature stage, reducing the initial load on the Stirling cooling unit 100; the Stirling cooling unit 100 precisely controls the temperature during the low-temperature stage, compensating for the inability of the evaporative cooling unit 200 to reach ultra-low temperatures. The sequential control of both reduces overall energy consumption and avoids the problem of excessively large heat dissipation devices. Simultaneously, the isolation effect of the valve structure 340 prevents mutual interference in the transfer of cold energy between different refrigeration stages.

[0043] Furthermore, in one embodiment, a heating element (not shown) is provided at the evaporator coil 210 of the evaporative cooling unit 200. The heating element includes, but is not limited to, heating wires, heating tubes, and heating plates. When the Stirling cooling unit 100 is operating, and the temperature of the evaporator coil 210 of the evaporative cooling unit 200 reaches (i.e., equals) the defrosting start temperature (typically between -30°C and -40°C, preferably -35°C), which is lower than the first target temperature and higher than the second target temperature, the controller can control the heating element to heat the evaporative cooling unit 200 so that the temperature of the evaporator coil 210 reaches the standard defrosting temperature (typically between 0°C and 5°C, preferably 0°C), which is greater than or equal to 0°C, to remove the frost on the evaporator coil 210. Specifically, when the Stirling cooling unit 100 is in operation, frost may form on the surface of the evaporator coil 210 of the evaporative cooling unit 200 due to the low temperature environment. By monitoring the temperature of the evaporator coil 210 in real time, the controller immediately activates the heating element to heat the coil when its temperature drops to the defrosting start temperature. The heating process continues until the coil temperature rises to the standardized defrosting temperature, at which point the frost layer completely melts and the evaporator returns to its optimal heat exchange efficiency. The setting of the standardized defrosting temperature ensures thorough defrosting, while the selection of the defrosting start temperature range balances cooling demand and defrosting frequency, avoiding increased system energy consumption or decreased cooling performance due to defrosting too early or too late.

[0044] Compared with existing technologies, this solution integrates heating elements into the evaporator coil 210 and combines them with a temperature triggering mechanism to achieve parallel control of the refrigeration and defrosting processes. Automated defrosting can be completed without interrupting the operation of the Stirling refrigeration unit 100, significantly improving the system's continuous operating capability. Furthermore, through the above technical solution, this application effectively solves the problem of reduced heat exchange efficiency caused by frost buildup on the evaporator coil 210 under low-temperature conditions. By precisely controlling the start-up and shutdown timing and heating intensity of the heating elements, efficient defrosting is achieved while maintaining stable operation of the refrigeration system, avoiding the reduction in cooling capacity and shortened equipment lifespan caused by frost accumulation.

[0045] Furthermore, in one embodiment, as Figure 2 As shown, the hot end 130 of the Stirling refrigeration unit 100 is equipped with a second fan 150. When the Stirling refrigeration unit 100 is operating and the temperature of the evaporator coil 210 of the evaporative refrigeration unit 200 is equal to the defrosting start temperature, the controller can control the second fan 150 to operate, so that the heat from the hot end 130 of the Stirling refrigeration unit 100 can be transferred to the evaporative refrigeration unit 200 through the airflow generated by the second fan 150. Specifically, during the operation of the Stirling refrigeration unit 100, when the temperature of the evaporator coil 210 of the evaporative refrigeration unit 200 reaches the preset defrosting start temperature, the controller triggers the second fan 150 to operate. The forced airflow generated by the second fan 150 quickly directs the heat accumulated at the hot end 130 of the Stirling refrigeration unit 100 to the evaporative refrigeration unit 200, causing the surface temperature of the evaporator coil 210 to rise above the standard defrosting temperature, thereby achieving automatic defrosting. During this process, the heat from the hot end 130 of the Stirling refrigeration section 100 is effectively transferred to the evaporative refrigeration section 200, which not only solves the heat dissipation problem of the Stirling refrigeration section 100, but also utilizes the waste heat to improve the defrosting efficiency of the evaporator.

[0046] In one embodiment, when the Stirling refrigeration unit 100 is operating and the temperature of the evaporator coil 210 of the evaporative refrigeration unit 200 is higher than the defrosting start temperature (i.e., the defrosting start temperature has not been reached), in the first operating condition, when the temperature of the hot end 130 of the Stirling refrigeration unit 100 is higher than a preset upper limit temperature (usually between 8°C and 15°C, preferably 10°C), the controller can control the Stirling refrigeration unit 100 to operate at a first power, which is less than the rated power of the Stirling refrigeration unit 100. The first power is usually between 40% and 60% of the rated power, preferably 50% of the rated power. Furthermore, the controller can control the evaporative refrigeration unit 200 to operate at a second power, which is greater than the rated power of the evaporative refrigeration unit 200. The second power is usually between 105% and 130% of the rated power, preferably 120% of the rated power, so that the temperature of the evaporator coil 210 of the evaporative refrigeration unit 200 is equal to the defrosting start temperature.

[0047] In the second operating condition, when the temperature of the hot end 130 of the Stirling refrigeration unit 100 is less than or equal to the preset upper limit temperature, and the difference between the internal cavity temperature of the inner low temperature chamber 300 and the second target temperature is greater than the preset temperature difference (usually between 1°C and 10°C, preferably 5°C), the controller can control the Stirling refrigeration unit 100 to operate at rated power, and the controller can control the evaporative refrigeration unit 200 to operate at second power, so that the temperature of the evaporator coil 210 of the evaporative refrigeration unit 200 is equal to the defrosting start temperature.

[0048] In the third operating condition, when the difference between the internal temperature of the inner low-temperature chamber 300 and the second target temperature is less than or equal to the preset temperature difference, the controller can control the Stirling refrigeration unit 100 to operate at a third power, which is less than the first power. The third power is usually 30% to 50% of the rated power. Furthermore, the controller can control the evaporative refrigeration unit 200 to operate at a fourth power, which is less than the rated power of the evaporative refrigeration unit 200. The fourth power is usually 40% to 60% of the rated power, preferably 50% of the rated power, so that the temperature of the evaporator coil 210 of the evaporative refrigeration unit 200 is equal to the defrosting start temperature.

[0049] Specifically, when the Stirling refrigeration unit 100 is operating and the evaporator coil 210 temperature is higher than the defrosting start temperature, the system operates in three control modes based on the temperatures of the hot end 130 and the inner low-temperature chamber 300. In the first mode, if the hot end 130 temperature exceeds the safety threshold, the Stirling refrigeration unit 100 operates at a reduced frequency to decrease heat generation, while the evaporator refrigeration unit 200 operates at overload to accelerate cooling, causing the evaporator coil 210 temperature to quickly drop to the defrosting start condition. In the second mode, when the hot end 130 temperature is within the safe range and the temperature difference between the inner low-temperature chamber 300 and the target temperature is large, the Stirling refrigeration unit 100 operates at full load to provide maximum cooling capacity, while the evaporator refrigeration unit 200 simultaneously operates at overload, rapidly reducing the system temperature through synergistic action. In the third mode, when the inner low-temperature chamber 300 approaches the target temperature, both the Stirling refrigeration unit 100 and the evaporator refrigeration unit 200 reduce their operating power, maintaining temperature accuracy while reducing energy consumption. The switching between the three modes is automatically completed by the controller through real-time monitoring of temperature parameters.

[0050] Through the above technical solution, this application effectively solves the thermal management problem when the Stirling refrigeration unit 100 and the evaporative refrigeration unit 200 work together, avoids the risk of equipment shutdown due to excessively high temperature at the hot end 130, and improves the temperature control accuracy of the system under cryogenic conditions. Through a dynamic power adjustment mechanism, it can maximize cooling capacity when rapid cooling is required, and reduce energy consumption when approaching the target temperature, thus extending the service life of key components.

[0051] The cascade cooling system can be controlled by a voice module, which is equipped with a controller, a voice receiving module, and a voice parsing module. The voice receiving module receives user commands, and the voice parsing module parses the commands. Based on the parsed commands, the controller controls the cascade cooling system to perform corresponding operations, thereby realizing intelligent control of the cascade cooling system and improving the user experience.

[0052] The smart appliance equipped with the cascade cooling system has a smart voice control module, which includes a controller, a voice receiving module, and a voice parsing module. The voice receiving module receives user commands, and the voice parsing module parses the commands. Based on the parsed commands, the controller controls the cascade cooling system to perform corresponding operations, thereby realizing the intelligent control of the cascade cooling system and improving the user experience of using the smart appliance.

[0053] This application also provides a refrigerator that includes the cascade refrigeration system described in any of the above embodiments.

[0054] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

[0056] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0058] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0059] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0060] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A cascade refrigeration system, characterized in that, The cascade refrigeration system includes a Stirling refrigeration unit (100), an evaporative refrigeration unit (200), and an inner low-temperature chamber (300). The system has an outer refrigeration chamber (410). The Stirling refrigeration unit (100), the evaporative refrigeration unit (200), and the inner low-temperature chamber (300) are all located within the outer refrigeration chamber (410). The evaporative refrigeration unit (200) is capable of refrigerating within the outer refrigeration chamber (410). The inner low-temperature chamber (300) is connected to the outer refrigeration chamber (410). A valve structure (340) is provided so that the cold energy in the external cooling chamber (410) can enter the internal low-temperature chamber (300) through the valve structure (340). The side wall of the internal low-temperature chamber (300) and the external cooling chamber (410) are heat-insulated. The cold end (110) of the Stirling refrigeration unit (100) is thermally connected to the inner wall of the internal low-temperature chamber (300), and the hot end (130) of the Stirling refrigeration unit (100) is thermally connected to the evaporative refrigeration unit (200).

2. The cascade cooling system according to claim 1, characterized in that, It also includes a controller. When the temperature inside the inner chamber of the inner low-temperature chamber (300) is higher than the first target temperature, the controller can control the valve structure (340) to open and cause the evaporative cooling unit (200) to deliver cold air to the inner low-temperature chamber (300) through the valve structure (340). When the temperature inside the inner chamber of the inner low-temperature chamber (300) reaches the first target temperature and remains there for a preset time, the controller can control the valve structure (340) to close and control the Stirling cooling unit (100) to start working so that the temperature inside the inner low-temperature chamber (300) reaches the second target temperature, which is lower than the first target temperature.

3. The cascade refrigeration system according to claim 2, characterized in that, The evaporator coil (210) of the evaporator cooling unit (200) is equipped with a heating element. When the Stirling cooling unit (100) is running and the temperature of the evaporator coil (210) of the evaporator cooling unit (200) is equal to the defrosting start temperature, the controller can control the heating element to heat the evaporator cooling unit (200) so that the temperature of the evaporator coil (210) of the evaporator cooling unit (200) reaches the standard defrosting temperature. The standard defrosting temperature is greater than or equal to 0°C, the defrosting start temperature is lower than the first target temperature, and the defrosting start temperature is higher than the second target temperature.

4. The cascade cooling system according to claim 3, characterized in that, When the Stirling refrigeration unit (100) is operating, and the temperature of the evaporator coil (210) of the evaporative refrigeration unit (200) is higher than the start-up defrosting temperature, In the first operating condition, when the temperature of the hot end (130) of the Stirling refrigeration unit (100) is greater than the preset upper limit temperature, the controller can control the Stirling refrigeration unit (100) to operate at a first power, which is less than the rated power of the Stirling refrigeration unit (100). The controller can also control the evaporative refrigeration unit (200) to operate at a second power, which is greater than the rated power of the evaporative refrigeration unit (200), so that the temperature of the evaporator coil (210) of the evaporative refrigeration unit (200) reaches the defrosting start temperature. In the second operating condition, when the temperature of the hot end (130) of the Stirling refrigeration unit (100) is less than or equal to the preset upper limit temperature, and the difference between the inner cavity temperature of the inner low temperature chamber (300) and the second target temperature is greater than the preset temperature difference, the controller can control the Stirling refrigeration unit (100) to operate at rated power, and the controller can control the evaporative refrigeration unit (200) to operate at second power, so that the temperature of the evaporator coil (210) of the evaporative refrigeration unit (200) reaches the defrosting start temperature; In the third operating condition, when the difference between the inner cavity temperature of the inner low temperature chamber (300) and the second target temperature is less than or equal to the preset temperature difference, the controller can control the Stirling refrigeration unit (100) to operate at a third power, which is less than the first power. Furthermore, the controller can control the evaporative refrigeration unit (200) to operate at a fourth power, which is less than the rated power of the evaporative refrigeration unit (200), so that the temperature of the evaporator coil (210) of the evaporative refrigeration unit (200) reaches the defrosting start temperature.

5. The cascade cooling system according to claim 3, characterized in that, The hot end (130) of the Stirling refrigeration unit (100) is provided with a second fan (150). When the Stirling refrigeration unit (100) is running and the temperature of the evaporator coil (210) of the evaporator refrigeration unit (200) is equal to the defrosting start temperature, the controller can control the second fan (150) to run so that the heat of the hot end (130) of the Stirling refrigeration unit (100) can be transferred to the evaporator refrigeration unit (200) through the airflow formed by the second fan (150).

6. The cascade cooling system according to claim 1, characterized in that, The inner low-temperature chamber (300) includes a heat-insulating shell (310), a heat-conducting plate (320), and a heat-conducting block (330). The heat-insulating shell (310) is disposed on the outer side of the inner low-temperature chamber (300) to isolate the heat transfer between the inner low-temperature chamber (300) and the outer cooling cavity (410). The heat-conducting plate (320) is disposed on the inner side of the inner low-temperature chamber (300). The heat-conducting block (330) is sandwiched between the heat-insulating shell (310) and the heat-conducting plate (320). Between the Stirling refrigeration unit (100), the cold end (110) of the Stirling refrigeration unit (100) is provided with a first heat pipe (120), and the heat-conducting block (330) is thermally connected to the cold end (110) of the Stirling refrigeration unit (100) through the first heat pipe (120), so that the cooling capacity of the cold end (110) of the Stirling refrigeration unit (100) can be transferred to the inner low temperature chamber (300) in sequence through the first heat pipe (120), the heat-conducting block (330) and the heat-conducting plate surface (320).

7. The cascade cooling system according to claim 1, characterized in that, The hot end (130) of the Stirling refrigeration unit (100) is provided with a second heat pipe (140). The two ends of the second heat pipe (140) are thermally connected to the hot end (130) of the Stirling refrigeration unit (100) and the evaporative refrigeration unit (200), respectively, so that the heat of the hot end (130) of the Stirling refrigeration unit (100) can be transferred to the evaporative refrigeration unit (200) through the second heat pipe (140).

8. The cascade cooling system according to claim 7, characterized in that, The second heat pipe (140) is spiral in shape and is spirally wound around the hot end (130) of the Stirling cooling section (100).

9. The cascade cooling system according to claim 1, characterized in that, It also includes a first fan, which is located in the external cooling chamber (410) to enable the gas in the external cooling chamber (410) to circulate.

10. A refrigerator, characterized in that, Includes the cascade refrigeration system as described in any one of claims 1-9.

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