102 results about "Cascade refrigeration" patented technology

The invention discloses an ultralow-temperature cascade refrigeration device, belongs to the technical field of refrigeration devices, and solves the problems that when a low-temperature screw compressor continuously operates below-80 DEG C, organic acid generated by hydrolysis of trace moisture and ester lubricating oil and metal chips form colloidal deposition, the resistance of a slide valve is increased, displacement lag is caused, and the service life of the slide valve is prolonged. However, the sensor only feeds back an instruction signal and cannot be monitored by a control system, and finally bearing wear or energy efficiency reduction is caused. Comprising a screw compressor and a slide valve state monitoring circuit arranged in the screw compressor. The actual displacement of the slide valve is measured in real time through double-frequency laser interference, the thickness of jelly is analyzed in combination with acoustic surface wave frequency shift, the fault index is calculated after dynamic compensation, early warning is conducted when the limit is exceeded, a blind area of a traditional sensor is eliminated, diagnosis is conducted in advance, and compressor bearing abrasion is avoided.

The invention relates to the technical field of sample storage, particularly provides a cascade refrigeration system and a control method of an ultralow-temperature sample library, and aims to solve the problem that normal operation of a unit is affected due to abnormal oil return of an existing cascade refrigeration system. In order to achieve the purpose, the cascade refrigeration system comprises a high-temperature-stage refrigeration unit, a low-temperature-stage refrigeration unit and an intermediate heat exchanger, the low-temperature-stage refrigeration unit comprises a low-temperature compressor, an oil separation device and a heat exchange device, the oil separation device comprises a plurality of oil separators arranged in sequence, and a heat exchanger is arranged between every two adjacent oil separators; the low-temperature compressor, the oil separation device, the intermediate heat exchanger and the heat exchange device are communicated with one another to form a low-temperature-stage refrigerant circulation loop, and the high-temperature-stage refrigeration unit and the intermediate heat exchanger are communicated with one another to form a high-temperature-stage refrigerant circulation loop. The oil separation efficiency can be improved, deep oil removal is achieved, and oil return is remarkably improved.

A method and apparatus for controlling compressors in a cascade vapor compression system. The process may include controlling the operation of a first compressor based on a constant band control, and controlling the operation of a second compressor based on a proportional band control. Controlling the first compressor based on the constant band control may include operating the compressor at a constant setting if first measurements are within a range associated with a first setpoint. It may also include proportionally adjusting the operation of the first compressor if the first measurements are outside the range. Further, controlling the second compressor based on the proportional band control may include operating the compressor based on one of a plurality of proportional bands, each proportional band having a different proportional factor. Controlling the second compressor operation may further include switching between these proportional bands based on a second measured parameter.

The invention discloses a carbon dioxide purification system based on multi-stage cryogenic coupling, and relates to the technical field of carbon dioxide purification, the carbon dioxide purification system comprises a pretreatment module, a multi-stage compression cooling module, a cryogenic coupling separation module, an adsorption separation module and an intelligent regulation and control module which are sequentially connected through pipelines; through the synergistic effect of the three-stage centrifugal compressor and vortex tube refrigeration, the carbon dioxide liquefaction efficiency is remarkably improved, meanwhile, the system utilizes the pressure balance valve to dynamically couple gradient temperature control of the cryogenic adsorption tower and the membrane separation assembly, the gas-liquid entrainment problem in the phase change process is effectively solved, and the carbon dioxide liquefaction efficiency is improved. Through cooperation of high-temperature cascade refrigeration and low-temperature vortex refrigeration, gradient temperature control layered adsorption of a cryogenic adsorption tower and dynamic separation of a membrane separation assembly are integrated, the recovery efficiency can be greatly improved, in addition, the system is provided with a multi-physics field sensor array, and operation parameters are dynamically regulated and controlled in combination with an intelligent optimization algorithm of a distributed edge calculation unit, so that the recovery efficiency is improved. And the energy efficiency ratio and the operation stability of the system can be obviously improved.

This invention provides a carbon dioxide recovery cascade refrigeration system, including a circulation loop and a first heat exchanger, a compressor, a condenser, and a first oil drain pipe disposed on the circulation loop. The circulation loop is used for the flow of carbon dioxide heat exchange medium. The first heat exchanger has independent first and second heat exchange channels. The first heat exchange channel has a first inlet and a first outlet. The second heat exchange channel has a second inlet and a second outlet respectively connected to the circulation loop. The carbon dioxide heat exchange medium in the second heat exchange channel is used to reduce the temperature of the medium in the first heat exchange channel. An oil drain port is provided at the bottom of the first heat exchange channel. The gas inlet of the compressor is connected to the second outlet of the first heat exchanger. The condenser is located downstream of the compressor and is used to condense the carbon dioxide heat exchange medium after compression by the compressor. The oil drain port is connected to the inlet of the compressor through the first oil drain pipe. This system uses carbon dioxide as the heat exchange medium, resulting in low cost.

The control method comprises the steps that the rotating speed of a high-temperature-stage inverter compressor is mainly comprehensively determined by the high-temperature-stage exhaust temperature, the high-temperature-stage condenser temperature, the high-temperature-side outlet temperature of an intermediate heat exchanger and the high-temperature-stage return air temperature; through dynamic adjustment of the first fuzzy PID controller, the working condition and energy efficiency of the high-pressure side of the system are optimized; the rotating speed of the low-temperature-stage frequency conversion compressor is mainly comprehensively determined by the temperature in the box, the real-time rotating speed of the high-temperature-stage compressor, the low-temperature-stage exhaust temperature, the temperature of the intermediate heat exchanger and the low-temperature-stage return air temperature, and the rotating speed is dynamically adjusted through the second fuzzy PID controller so as to ensure that the temperature in the box is accurate and stable and is matched with the high-temperature-stage capacity in real time. Through cooperative control of the parameter groups, the problems of low efficiency and unstable operation caused by mismatching of two-stage capabilities of the cascade system are solved, and efficient, stable and reliable operation of the system under all working conditions is realized.

The present application provides a startup control method for a cascade refrigeration system of a preservation box, comprising: step S10, powering on the preservation box, and starting the high-temperature compressor of the cascade refrigeration system at a first set frequency RH0; step S11, determining a target operating time of the high-temperature compressor to meet the starting condition of the low-temperature compressor; step S12, determining a target frequency for full-load operation of the high-temperature compressor and the low-temperature compressor of the cascade refrigeration system; step S13, determining a frequency increase / decrease mode, and controlling the high-temperature compressor to increase / decrease the frequency to its target frequency; step S14, when the high-temperature compressor operating time reaches the target time, the low-temperature compressor is started at a second set frequency RL0; step S15, determining a frequency increase / decrease mode, and controlling the low-temperature compressor to increase / decrease the frequency to its target frequency; and step S16, when the actual temperature Td of the compartment reaches the set compartment temperature Ts.

The invention relates to the technical field of ultralow-temperature treatment equipment, in particular to a cascade refrigeration system for a cold therapy instrument, which comprises a first-stage compression cycle module, a second-stage compression cycle module, a third-stage compression cycle module, a fourth-stage compression cycle module, a fifth-stage compression cycle module and a sixth-stage compression cycle module, the first-stage compression circulation module is connected with the second-stage compression circulation module in parallel through the first heat exchanger, and a second heat exchanger and a composite evaporator are arranged on the second-stage compression circulation module; and the third-stage compression circulation module is connected with the second-stage compression circulation module in parallel through the second heat exchanger, and the third-stage compression circulation module is communicated with the composite evaporator. The air conditioner has the effect of increasing the refrigerating temperature range.

The utility model discloses a cascade refrigerating system which comprises a high-temperature-stage refrigerating unit and a low-temperature-stage refrigerating unit. The high-temperature-stage refrigerating unit comprises a high-temperature-stage compressor, a high-temperature-stage condenser and a cascade heat exchanger serving as a high-temperature-stage evaporator. The low-temperature-stage refrigerating unit comprises a low-temperature-stage compressor, a low-temperature-stage evaporator and the cascade heat exchanger serving as a low-temperature-stage condenser in the low-temperature-stage refrigerating unit. A pre-cooling heat exchanger is arranged on a pipeline between the low-temperature-stage compressor and the cascade heat exchanger and arranged on one side of the high-temperature-stage condenser, and the pre-cooling heat exchanger and the high-temperature-stage condenser share a condensation fan. High-temperature and high-pressure gas exhausted by the low-temperature-stage compressor is primarily cooled through the pre-cooling assembly and then is further cooled through the cascade heat exchanger, and the refrigerating capacity of the high-temperature-stage compressor is effectively reduced.

The invention relates to the technical field of sample storage, in particular to a control method of an ultralow-temperature sample library, and aims to solve the problem that an existing cascade refrigeration system is complicated in operation due to the fact that oil return abnormity occurs and personnel need to go to the site for treatment. In order to achieve the purpose, the ultralow-temperature sample library comprises a cascade refrigeration system, and the control method of the ultralow-temperature sample library comprises the steps that under the condition that the cascade refrigeration system is in a refrigeration mode, when the oil level of a high-temperature-level refrigeration unit is abnormal, the cascade refrigeration system is controlled to enter a first oil return mode; and when the oil level of the low-temperature-stage refrigeration unit is abnormal, the cascade refrigeration system is controlled to enter a second oil return mode. According to the invention, the cascade refrigeration system can automatically process the abnormal oil return after monitoring the abnormal oil return, and personnel do not need to go to the field for processing.

The invention relates to a method and apparatus for controlling a compressor in a cascade vapour compression system. The process may include controlling operation of the first compressor based on constant band control, and controlling operation of the second compressor based on proportional band control. If the first measurement is within a range associated with the first setpoint, controlling the first compressor based on the constant band control may include operating the compressor at a constant setting. If the first measurement is outside the range, it may also include proportionally adjusting operation of the first compressor. Further, controlling the second compressor based on proportional band control may include operating the compressor based on one of a plurality of proportional bands, each proportional band having a different proportionality coefficient. Controlling second compressor operation may also include switching between the proportional bands based on a second measured parameter.

This utility model belongs to the field of large-scale cold storage refrigeration technology, specifically relating to a fully automatic oil return system for the low-temperature stage of a carbon dioxide cascade refrigeration system. It includes a gas-liquid separator, with an inlet pipe (II), an exhaust pipe (IV), and a drain pipe (I). A carbon dioxide shielded pump is installed on the drain pipe (I). A drain pipe (II) is installed and connected to the end of the drain pipe (I). An oil return pipe (I) is installed and connected to the outer periphery of the drain pipe (II). A gas return pipe (I) is installed and connected between the carbon dioxide shielded pump and the gas-liquid separator. An oil return valve assembly is installed on the oil return pipe (I). A plate heat exchanger is detachably connected and connected to the end of the oil return pipe (I). A carbon dioxide compressor module is detachably connected and connected to the plate heat exchanger. Compared to existing technologies, this utility model reduces energy loss in subsequent refrigeration stages, achieves fully automatic control of the oil return process, eliminates the need for manual operation, reduces labor costs, and avoids human error.

The invention relates to a cooling unit for storing temperature-sensitive goods at a desired cooling temperature, comprising a cooling compartment (9) for storing the temperature-sensitive goods, an insulation (1) separating the cooling compartment (9) from an ambient space (10), a multi-stage cascade refrigeration system adapted to cool down the cooling compartment (9) to the desired cooling temperature and / or maintain the desired cooling temperature in the cooling compartment (9), said multi-stage cascade refrigeration system comprising at least a high-temperature refrigeration cycle (11) and a low-temperature refrigeration cycle (12), whereas said low-temperature refrigeration cycle (12) comprises a low-temperature evaporator (13) arranged to absorb heat from the cooling compartment (9), and whereas the high-temperature refrigeration cycle (11) comprises a high-temperature condenser (14) arranged to reject heat to the ambient space (10), whereas a high-temperature evaporator (3) of the high-temperature refrigeration cycle (11) is thermally coupled to a low-temperature condenser (4) of the low-temperature refrigeration cycle (12) in order to form an intercooler, whereas said high-temperature evaporator (3) and / or said low-temperature condenser (4) are / is thermally coupled to the insulation (1).

The invention relates to a shell and tube type condensation and evaporation circulating barrel applied to a cold-carrying or cascade refrigeration system. The problems that in the background technology, when a condensation evaporator and a low-pressure circulation barrel are two independent devices, the devices are too high, the manufacturing cost, the transportation cost, the installation cost and the like of the devices can be increased, the cavitation phenomenon of a refrigeration pump can be caused when the height is reduced, and even faults of the refrigeration pump can be caused when the height is serious are solved. According to the technical scheme for solving the technical problem, the equipment is provided with a liquid inlet, a left tube plate, a barrel, a heat exchange tube, an air inlet, a right tube plate, an air outlet, a left liquid cavity, a liquid outlet and a right air cavity; a liquid storage space is arranged at the bottom of the barrel. The invention is suitable for refrigeration systems.

The application relates to a multi-stage cascade refrigeration and heating method, device, storage medium and electronic equipment. The method comprises the following steps: after starting a first-stage compressor of a multi-stage cascade refrigeration and heating device, determining a pressure change rate of the first-stage compressor, wherein the multi-stage cascade refrigeration and heating device at least comprises the first-stage compressor and a second-stage compressor; determining a starting time of the second-stage compressor according to the pressure change rate; and starting the second-stage compressor when the starting time of the second-stage compressor is met. The application solves the technical problem of compressor tripping in a two-stage cascade system.

The invention belongs to the technical field of oil gas recovery, and discloses an ultralow-temperature condensation and ultralow-emission oil gas recovery system and method.A component self-adaptive gradient matching mixed working medium is adopted to be matched with a single-stage inverter compressor, oil gas component online detection and an AI algorithm are combined, the working medium ratio can be dynamically adjusted so as to accurately meet the refrigeration requirements of oil gas with different components, and the oil gas recovery efficiency is improved. A complicated cascade refrigeration structure is not needed, so that the operation stability is improved while the system is simplified; due to the design of the integrated composite heat exchanger, the heat exchange structure is optimized, the cold energy loss is reduced, the heat exchange efficiency is improved, a stable ultralow-temperature cold source is provided for oil-gas deep condensation separation, and oil-gas deep separation is guaranteed from the refrigeration end; the pre-separation module integrates multiple pretreatment functions, strictly controls the cleanliness of oil gas through a secondary pretreatment mechanism, removes impurities in the oil gas, prevents the impurities from blocking, abrading and other influences on the system in an ultralow-temperature environment, and guarantees continuous operation of the system.

The invention relates to a cascade refrigeration system, a control method thereof and refrigeration equipment, relates to the technical field of refrigeration, and aims to improve the refrigeration response speed when a low-temperature refrigeration loop of the cascade refrigeration system is started. The cascade refrigeration system comprises an intermediate heat exchanger, a high-temperature refrigeration loop, a low-temperature refrigeration loop and a bypass loop. The high-temperature refrigerating loop comprises a first compressor, a first condenser, a first throttler and an intermediate heat exchanger which are sequentially connected, and the intermediate heat exchanger is an evaporation side in the high-temperature refrigerating loop. The low-temperature refrigerating loop comprises a second compressor, an intermediate heat exchanger, a second throttler and an evaporator which are sequentially connected, and the intermediate heat exchanger is a condensation side in the low-temperature refrigerating loop. The bypass loop is arranged in the low-temperature refrigeration loop. And the bypass loop comprises a circulating pump and is configured as follows: before the second compressor is started, the high-temperature refrigerating loop is started, and the bypass loop is conducted for a first preset time so as to drive the refrigerant to circularly flow along the low-temperature refrigerating loop.

The invention relates to a plate-shell type condensation and evaporation circulating barrel applied to a cold-carrying or cascade refrigeration system. The problems that in the background technology, when a condensation evaporator and a low-pressure circulation barrel are two independent devices, the devices are too high, the manufacturing cost, the transportation cost, the installation cost and the like of the devices can be increased, the cavitation phenomenon of a refrigeration pump can be caused when the height is reduced, and even faults of the refrigeration pump can be caused when the height is serious are solved. The key point of the technical scheme adopted for solving the technical problem is that the equipment is provided with a liquid inlet, a left seal head, a cylinder body, a plate core, an air inlet, a right seal head, an air outlet and a liquid outlet; a liquid storage space is arranged at the bottom of the barrel. The invention is suitable for refrigeration systems.

The application discloses a cascade refrigeration system flow control method and device, a refrigeration equipment and a medium. The cascade refrigeration system comprises a low-temperature stage compressor, a high-temperature stage compressor, an intermediate heat exchanger, a temperature sensor, a condensing fan and a temperature drop rate sensor. The temperature sensor is arranged on the intermediate heat exchanger. The method comprises the following steps: when the low-temperature stage compressor is started, the real-time temperature monitored by the temperature sensor is synchronously acquired, and the running time length of the low-temperature stage compressor is recorded; the running state of the low-temperature stage compressor is determined according to the real-time temperature and the running time length; and if the low-temperature stage compressor is in a low-flow running state, a low-flow response mode is started. The temperature detected by the temperature sensor and the calculated instantaneous temperature drop rate are utilized to determine the flow condition when the low-temperature stage compressor is started, and the flow control is performed according to the instantaneous temperature drop rate, so that the problem that the refrigerant flow is low and the temperature drop rate is slow due to the liquid accumulation in the intermediate heat exchanger when the low-temperature stage compressor is started is solved.

The invention discloses a starting control method of a cascade refrigeration system, which comprises the following steps: a1, electrifying the cascade refrigeration system, detecting the refrigerant pressure P of an outlet of a low-temperature compressor, and comparing the P with the electrifying calibration pressure P1; a2, if P is larger than P1, it is judged that the system is normal, and a preset system starting step is executed; if P is smaller than P1, it is judged that the system is abnormal, the pressure rapid recovery step of the preset number of times is executed, the refrigerant pressure P of an outlet of the low-temperature-stage compressor is detected again, P and the power-on calibration pressure P1 are compared, if P is smaller than P1, it is judged that the system breaks down, and if P is not smaller than P1, the preset system starting step is executed; the pressure quick recovery step comprises the steps that the low-temperature-stage compressor is started, the low-temperature-stage compressor is closed after the working time of the low-temperature-stage compressor does not exceed t1, and t1 is the preset time for preventing tripping of the low-temperature-stage compressor.

The invention discloses a biogas liquefaction system with an anti-ice-blockage desublimation and decarburization mechanism and a biogas liquefaction method. The biogas liquefaction system comprises a raw material gas pretreatment mechanism, a VPSA nitrogen removal mechanism, a desublimation and decarburization mechanism, a biogas liquefaction mechanism and a cascade refrigeration mechanism, the VPSA nitrogen removal mechanism comprises two nitrogen adsorption towers, and the two nitrogen adsorption towers can alternately perform adsorption and regeneration; the desublimation and decarbonization mechanism comprises two desublimation separators, a cold pipe and a heat pipe are arranged in each desublimation separator, and the two desublimation separators can alternately perform desublimation and carbon dioxide crystallization and sublimation and carbon dioxide removal regeneration. The method has the advantages that the carbon dioxide is effectively separated from the biogas in a crystal form, so that the problem of ice crystal blockage caused by the carbon dioxide, water vapor or impurities at low temperature can be prevented, and the whole decarburization and liquefaction process can be stably and continuously operated for a long time.

The invention discloses a refrigeration pipeline device, a refrigeration circuit, a refrigeration circuit leakage detection system, a connection unit and a method for assembling the refrigeration pipeline device. The refrigeration pipeline device comprises a gas pipeline, and the gas pipeline is provided with a first opening and a second opening which penetrate through the side wall of the gas pipeline. A liquid line including an outer portion and an inner portion extending through the gas line. A connection unit positioned at each opening in the gas line, and each connection unit including a line fitting attached to an end of an inner portion of the liquid line, and a cap attached to an end of an outer portion of the liquid line and fixed to a side wall of the gas line around the opening.

This invention discloses a cascade refrigeration system driven by industrial condensate waste heat, comprising: a first evaporator, an R134a centrifugal compressor, an evaporator-condenser, a first pressure-reducing throttling valve, an absorber, a lithium bromide solution pump, a generator, a heat exchanger, a second pressure-reducing throttling valve, a condenser, and a third pressure-reducing throttling valve. For the R134a refrigerant cycle, the cold fluid side of the first evaporator is a refrigerant flow, and the hot fluid side outlet of the first evaporator is connected to the inlet of the R134a centrifugal compressor. For the lithium bromide refrigeration cycle, the hot fluid side outlet of the evaporator-condenser is connected to the inlet of the absorber, the outlet of the absorber is connected to the inlet of the lithium bromide solution pump, the outlet of the lithium bromide solution pump is connected to the inlet of the heat exchanger, the outlet of the heat exchanger is connected to the inlet of the generator, the solution outlet of the generator is connected to the heat exchanger, the liquid phase outlet of the generator is connected to the hot fluid side inlet of the heat exchanger, and the hot fluid side outlet of the heat exchanger is connected to the second pressure-reducing throttling valve.

The utility model discloses a kind of composite evaporation absorbers of step-by-step refrigeration in the technical field of refrigeration equipment, comprising: fixed tube sheet heat exchanger;Fixed tube sheet heat exchanger is equipped with baffle, the baffle is used to split the inner cavity of fixed tube sheet heat exchanger into low-pressure evaporation cavity, low-pressure absorption cavity, middle-pressure absorption cavity and middle-pressure evaporation cavity;In the application, middle-pressure evaporation cavity first utilizes cold source to preliminarily cool heat transfer medium, low-pressure evaporation cavity is cooled again to heat transfer medium by using the remaining cold source discharged from middle-pressure evaporation cavity, replace single-stage refrigeration by step-by-step refrigeration, solve the problem that cost is too high due to equipment is too large in single-stage refrigeration, reduce the transportation cost of equipment.

The application provides a refrigerating machine cascade refrigeration system and a refrigeration method, relates to the technical field of refrigerating machines, and the system comprises a first cooling loop, a second cooling loop and a third cooling loop. Cooling liquid can circulate in different cooling loops to perform heat exchange cooling on a refrigeration object. The cooled cooling liquid needs to be cooled again before being circulated. The first cooling loop cools the cooling liquid by using a cooling box, the second cooling loop cools the cooling liquid by using a refrigerating machine, and the third cooling loop cools the cooling liquid by using a combination of the cooling box and the refrigerating machine in a faster way. Through the cascade cooling mode, the refrigerating machine can be prevented from being in an overload or underload state, the service life of the refrigerating machine can be prolonged, and the system structure can be simplified through the arrangement of a first three-way valve and a second three-way valve.

Provided is a cascade refrigeration system capable of suppressing a decrease in heating performance due to a rapid startup operation. The cascade refrigeration system includes: a high-order side refrigerant circuit (2) through which a high-order side refrigerant circulates; a low-order side refrigerant circuit (3) through which a low-order side refrigerant circulates, the low-order refrigerant circuit (3) including a first circulation path (23) that performs heat-exchange with the high-order side refrigerant in a cascade heat exchanger (13), and a second circulation path (26) that performs heat-exchange with a heat medium in a low-order side heat exchanger (24); and a heat medium circuit (4) through which a heat medium circulates, the heat medium exchanging heat with the high-order side refrigerant in the high-order side heat exchanger (11) and exchanging heat with the low-order side refrigerant in the low-order side heat exchanger (24). The heat medium circuit (4) includes: a first heat medium circulation path (35) in which the heat medium circulates through the high-order side heat exchanger (11) and the low-order side heat exchanger (24); and a second heat medium circulation path (36) in which the heat medium circulates through the high-order side heat exchanger (11).

This invention relates to the technical field of oil and gas recovery and treatment, and discloses an oil and gas condensation recovery system and method with refrigerant precooling and cascaded cold energy recovery. The system consists of a refrigerant precooling unit, a cryogenic liquefaction unit, a cold energy recovery unit, a refrigerant circulation system, a liquid hydrocarbon recovery unit, a tail gas treatment unit, and an automatic control unit. The precooling heat exchanger uses a refrigerant at -3℃ to -10℃ for indirect heat exchange, stably reducing the oil and gas temperature to -2℃ to -4℃, removing water vapor and heavy hydrocarbons. The primary and secondary cryogenic heat exchangers operate alternately in dual channels, working in conjunction with a cascade refrigeration unit to gradually cool the oil and gas to -20℃ to -40℃ and -65℃ to -75℃, respectively. The high-temperature refrigerant in the unit self-defrosts, ensuring continuous operation. The refrigerant circulation system and the cryogenic refrigeration system operate independently without interference, reducing the overall system failure risk and improving long-term reliability and maintenance convenience. This invention features precise temperature control, high cold energy utilization, no frost or blockage, continuous and stable operation, and combines environmental and economic benefits.

The invention relates to the field of refrigeration, in particular to a subcritical carbon dioxide cascade refrigeration system which is characterized in that a high-temperature stage liquid storage tank, a high-temperature stage condenser and a high-temperature stage compressor are sequentially connected to form a circulation loop which forms a high-temperature stage unit; a circulation loop formed by sequentially connecting the low-temperature-stage liquid storage tank, the air cooler and the low-temperature-stage compressor forms a low-temperature-stage unit, and refrigerant in the circulation loop of the high-temperature-stage unit exchanges heat with carbon dioxide in the circulation loop of the low-temperature-stage unit through the heat exchanger. By controlling the opening degree of the high-temperature-stage electronic expansion valve and the frequency of the high-temperature-stage compressor, the pressure of carbon dioxide in the low-temperature-stage unit can be always kept within the set pressure bearing value range; and meanwhile, the air cooler can be accurately defrosted, and defrosting lagging, incomplete defrosting and excessive defrosting are avoided.

The present disclosure provides a fault handling method and apparatus, a cryogenic storage box, and a storage medium, relating to the field of control. The fault handling method includes: if a first sensor for collecting the temperature within the cryogenic storage box fails, adjusting the frequencies of the high-temperature compressor and the low-temperature compressor in a cascade refrigeration system to preset target frequencies; and controlling the high-temperature compressor and the low-temperature compressor to shut down after a preset refrigeration time.

Provided is a cascade refrigeration cycle apparatus that is highly efficient. The cascade refrigeration cycle apparatus includes a fan, a first cycle, a second cycle, and a cascade heat exchanger. In the first cycle, a first refrigerant having a critical point of 40° C. or higher circulates. The first cycle includes a condenser in which air supplied by the fan and the first refrigerant exchange heat. In the second cycle, carbon dioxide as a second refrigerant circulates. The second cycle includes a first heat exchanger functioning as a radiator in which air supplied by the fan and the second refrigerant exchange heat. In the cascade heat exchanger, the first refrigerant and the second refrigerant exchange heat. The condenser is disposed on a windward side of the radiator in an airflow direction that is a direction of an airflow generated by the fan.