66 results about "Cascade refrigeration" patented technology

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 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.

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 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.

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.

This invention discloses a self-cascade refrigeration system, its control method, and a constant temperature and humidity environment chamber. The self-cascade refrigeration system includes: a compressor, a first heat exchanger, a gas-liquid separator, a second heat exchanger, a first throttling component, a second throttling component, a third throttling component, an evaporator, a first valve, a second valve, an expansion branch, and a control module. The control module is configured to control the system's operating mode by controlling the opening and closing of the first throttling component, the second throttling component, the third throttling component, the first valve, and the second valve. The operating modes include a temperature mode and a humidity mode. During the temperature mode and the switching between temperature and humidity modes, the compressor's discharge temperature and discharge pressure are adjusted by regulating the expansion branch. In the humidity mode, the compressor's discharge temperature and discharge pressure are adjusted by controlling the second throttling component. This system can prevent the compressor from experiencing excessively high discharge pressure and temperature, improving the compressor's reliability.

The invention relates to a cold exchange station standby refrigerating system and method based on carbon dioxide energy storage, and the system comprises an LNG heat exchange system which is used for liquefying carbon dioxide when LNG supply is sufficient; receiving gaseous carbon dioxide used by the cold exchange station; the cold exchange station circulating system is used for carrying out flow control and pressure regulation on the liquid carbon dioxide when the LNG supply is sufficient and then inputting the liquid carbon dioxide into the cold exchange station for use; the carbon dioxide energy storage system is used for transferring the cold energy of the liquid refrigerant to gaseous carbon dioxide when the LNG supply is insufficient, and liquefying and storing the gaseous carbon dioxide; when the LNG supply is insufficient, the stored liquid carbon dioxide is input into the cold exchange station for use; the cascade refrigeration high-temperature system is used for carrying out compression and water cooling on a gaseous refrigerant after cold transfer to obtain a liquid refrigerant when LNG supply is insufficient, and the cascade refrigeration high-temperature system can be widely applied to the technical field of LNG cold energy utilization.

The invention relates to the technical field of cold-chain transportation, and discloses an energy-saving aquatic product ultralow-temperature cold-chain transportation device and a fresh-keeping method.The energy-saving aquatic product ultralow-temperature cold-chain transportation fresh-keeping method comprises the steps that aviation cargo hold direct-current power source data is obtained, and an ultralow-temperature environment data set is generated through direct-current boost conversion and three-stage cascade refrigeration; constructing an energy storage layer and controlling intermittent operation; magneto-rheological vibration reduction is carried out, and a cooperative control strategy is combined; defrosting collaborative multispectral sensing and quality prediction are carried out; a hierarchical control strategy of a three-layer architecture is adopted to obtain a multi-parameter cooperative control scheme; performing thermoelectric conversion; performing multi-layer composite heat preservation to obtain a heat preservation structure optimization scheme; under the condition that air transportation is limited, the ultralow temperature of minus 65 DEG C can be stably kept, temperature fluctuation is controlled within an extremely small range, aquatic product tissues are effectively protected against vibration damage, the preservation effect is monitored in real time, and a technical solution is provided for high-end aquatic product air cold chain transportation.

This utility model discloses an energy-saving cascade refrigeration system, belonging to the technical field of refrigeration equipment. It includes a high-temperature stage refrigeration module and a low-temperature stage refrigeration module, connected by a cascaded evaporator-condenser. The system employs a dual-condenser and dual-evaporator design, automatically switching operating modes according to ambient temperature and set requirements: when the set temperature is ≥-10℃, only the high-temperature stage single-stage refrigeration is activated, directly cooling through the evaporator inside the chamber; when the set temperature is <-10℃, the cascade mode is activated, utilizing the evaporator-condenser to provide a cold source for the low-temperature stage. An environmental compensation module handles extreme conditions through an electric heater and a fan speed controller: in summer high temperatures (≥30℃), dual-stage water cooling is activated simultaneously; in winter low temperatures (≤-20℃), dual-stage electric heating is activated. The system uses VRF technology to precisely regulate refrigerant flow, coupled with multiple safety protections, achieving a temperature control accuracy of ±0.5℃, stable operation within an environmental range of -30℃ to +50℃, and energy savings of over 40%.

The invention belongs to the technical field of geotechnical engineering freezing test equipment, and particularly relates to an intelligent self-maintenance and multi-mode visual ultralow-temperature frost heaving test system and method.The intelligent self-maintenance and multi-mode visual ultralow-temperature frost heaving test system comprises an active thermal field programmable cooling head which comprises a multi-stage auto-cascade refrigeration unit used for providing the basic low temperature of-120 DEG C, the two-dimensional thermoelectric semiconductor (TEC) array is integrated on an output cold plate of the refrigeration unit in a heat conduction manner; the one-way freezing and multi-mode visualization system comprises an optical imaging unit, an electrical tomography unit and an acoustic phased array imaging unit which are used for monitoring the internal freezing process of the sample; and an intelligent diagnosis and stepped hot fluorine defrosting system. The system not only can realize a repeatable and controllable frost heaving experiment at the level of-120 DEG C, but also can reveal the mechanism of ice lenticular inoculation and freezing frontal surface evolution under the condition of whole-course dynamic visualization, so that the mechanism research depth of an extremely low temperature artificial freezing technology and the accuracy of engineering application design are remarkably improved.

The invention relates to the technical field of refrigeration, and discloses a CO2CO circulation module based on waste heat driving, a high-temperature end circulation module and an oil rectification module. The oil rectification module receives oil-containing liquid CO of a low-pressure circulation barrel through a buffer cavity, and high-temperature end compressor exhaust waste heat recycled by a gas separation type gas-liquid heat exchanger is used as a heat source to achieve separation of CO and lubricating oil. The separated pure lubricating oil converges into the oil storage tank and returns to the compressor together with oil content return oil, and CO steam returns to the low-temperature end for circulation. According to the invention, the gas separation type gas-liquid heat exchanger is arranged between the high-temperature-stage compressor and the high-temperature-stage condenser, so that heat in exhaust gas of the high-temperature-stage compressor is transferred to the oil rectifier through the gas separation type gas-liquid heat exchanger to serve as a heating heat source required by oil rectification, and therefore, waste heat of the exhaust gas at the high-temperature end is used for replacing an independent electric heating device; and the external energy consumption demand in the oil rectification process is reduced.

The embodiment of the present disclosure discloses a method, device, equipment and medium for calibrating refrigerant injection amount in a cascade refrigeration system, wherein the method comprises: determining a sample data set based on a plurality of groups of charge amount groups corresponding to refrigerants in an at least two-stage refrigeration cycle system; constructing a refrigeration capacity model for solving refrigeration capacity and an operating current model for solving operating current based on the sample data set and the plurality of groups of charge amount groups; solving the refrigeration capacity model and the operating current model with the maximum refrigeration capacity and the minimum operating current as the target to obtain a plurality of groups of data; and determining a target data group from the plurality of groups of data based on the candidate physical parameters to obtain a target charge amount corresponding to the refrigerants in the at least two-stage refrigeration cycle system. The target charge amount obtained by the embodiment of the present disclosure meets the requirements of the maximum refrigeration capacity and the minimum operating current at the same time, and improves the energy utilization rate of the cascade refrigeration system.

The application relates to the technical field of refrigeration equipment, in particular to a three-stage cascade refrigeration system which comprises a carrier refrigerant system and a three-stage compression refrigeration system; the three-stage compression refrigeration system comprises a first compressor, a second compressor and a third compressor; the carrier refrigerant system comprises a liquid storage tank, a circulating pump and a first evaporator, a second evaporator and a third evaporator which are arranged in series; the liquid storage tank is connected with a first carrier refrigerant passage inlet of the first evaporator through a pipeline and the circulating pump; the liquid storage tank is connected with a second carrier refrigerant passage inlet of the second evaporator through a pipeline and the circulating pump; the liquid storage tank is connected with a third carrier refrigerant passage inlet of the third evaporator through a pipeline and the circulating pump; a first carrier refrigerant passage outlet of the first evaporator, a second carrier refrigerant passage outlet of the second evaporator and a third carrier refrigerant passage outlet of the third evaporator all return to the liquid storage tank through pipelines; the application can reduce the cost of refrigeration in different temperature ranges.

The invention belongs to the technical field of aircraft refrigerating systems, and particularly relates to an airborne auto-cascade refrigerating system control method and system. The cold source temperature T1 at the fuel supply position of the aircraft fuel system and the heat sink temperature T2 at the liquid return position of the airborne equipment needing temperature control are collected, and when T2-T1 is larger than T02, the airborne auto-cascade refrigeration system operates in an auto-cascade mode; and when T2-T1 is greater than or equal to T01 and less than or equal to T02, acquiring gravity overload or attitude change data of the aircraft, acquiring the temperature T3 and the pressure P3 at the inlet of the gas-liquid separator, constructing an agent model representing the mapping relation of the two-phase inlet state, the gravity condition and the separation efficiency of the gas-liquid separator, and calculating the gas-liquid separation efficiency of the gas-liquid separator through the agent model. The separation efficiency is compared with a preset separation efficiency threshold value, and the airborne auto-cascade refrigeration system is controlled to operate according to an auto-cascade mode or a single-stage compression mode according to a comparison result; when T2-T1 is smaller than T01, the airborne auto-cascade refrigeration system operates in a single-stage compression mode, T01 is the lower threshold value of the difference value between the heat sink temperature T2 and the cold source temperature T1, and T02 is the upper threshold value of the difference value between the heat sink temperature T2 and the cold source temperature T1. According to the invention, efficient and reliable operation of the airborne refrigeration cycle system can be realized in a complex dynamic environment and a wide temperature range working condition.

A control system and method for a separation-enhanced self-cascade refrigeration cycle are disclosed. The system includes a controller connecting sensors, adjustment mechanisms, and a control structure. The method includes inputting preset parameters of the separation-enhanced self-cascade refrigeration cycle system, real-time parameter acquisition by the controller, parameter judgment by the controller, and defining the start-up phase, the low-temperature pull-down phase, and the steady-state operation phase. The system compares the operating time with the set time to distinguish between the start-up phase and the low-temperature pull-down phase; it also compares the evaporator outlet temperature with the set temperature to distinguish between the low-temperature pull-down phase and the steady-state operation phase. In each of the three operating phases, the system achieves efficient operation by adjusting the opening of the electronic expansion valve, the on / off state of the solenoid valve, and the start / stop of the fan and compressor. The control system and method proposed in this invention can protect the safe start-up of the separation-enhanced self-cascade refrigeration cycle system, increase the rate of low-temperature pull-down and the cooling capacity, significantly improve the thermodynamic performance of the separation-enhanced self-cascade refrigeration cycle system, and maintain the system's efficient and stable operation.

A cascade refrigeration natural gas liquefaction system and process, which relate to the technical field of refrigeration and cryogenic engineering. The process may include an ethane refrigeration cycle and a mixed refrigerant refrigeration cycle. Refrigerants according to the present disclosure may include propane, ethane and a mixed refrigerant that may be composed of nitrogen, methane and ethane. Except for nitrogen supplied from public utilities, the refrigerants may be sourced from the natural gas itself. The comprehensive energy consumption of liquefaction per unit according to the present disclosure may be lower than the propane precooling mixed refrigerant process and the conventional cascade process. Although it may be slightly higher than that of the dual mixed refrigerant process in winter working condition, the energy consumption of the dual mixed refrigerant process is exceedingly high in summer, and the total energy consumption of the process of the present disclosure is still low comprehensively.

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).