55results about How to "Solve the problem of oil return" patented technology

The invention discloses a natural circulation gravity liquid supply evaporator, aiming to provide an evaporator which can enhance the heat transfer coefficient so as to further improve the performance and efficiency of the entire refrigeration device. The low-pressure liquid refrigerant outlet of a gas-liquid separator is connected with the refrigerant inlet of an evaporator; the refrigerant outlet of the evaporator is connected with the inlet of the gas-liquid separator through a return gas pipe; the gas outlet of the gas-liquid separator is connected with a compressor return gas pipe; a liquid level sensor is arranged at the external side of the gas-liquid separator; the liquid level sensor is connected with a liquid level controller; the control signal outlet end of the liquid level controller is connected with the control end of an electronic expansion valve; one end of the electronic expansion valve is connected with the low-pressure liquid refrigerant inlet of the gas-liquid separator; and the other end of the electronic expansion valve is connected with the tube side outlet of a gas-liquid heat exchanger. As the evaporator increases the flow amount of the liquid refrigerant in the evaporator, the refrigerant with high flow rate can completely contact the inner wall of the refrigerant evaporation pipe so as to make full of the heat exchange surface and achieve higher heat transfer coefficient.

The invention pertains to heating and hot water supply field, relating to a high efficiency large temperature rise compression heat pump set with a big inlet-outlet temperature difference at both a heat sink side and a head source side. The large temperature rise compression heat pump set is configured by assembling two water source heat pump devices, and each heat pump set comprises separately in series or in parallel a compressor, a condenser, an evaporator, a subcooler, and a throttling device, or an added economizer, and forms a separate working medium circulation loop. The inventive large temperature rise compression heat pump set can heat returned hot water step by step from a low temperature to a high temperature, the cold water is cooled step by step in a reverse direction of the temperature rise of the cooling water, and temperature difference between the hot water and cold water at the inlet and outlet of the heat pump is enlarged; and the performance coefficient of the heat pump set is further enhanced comparing with a simple two-stage compression heat pump in series, so that the comprehensive energy utilization efficiency and economy of the inventive system are increased greatly comparing with a common heat pump set.

The invention discloses an air conditioner oil return control method and device. The method comprises the steps that whether a multi-connected air-conditioning system meets the oil return condition ornot is detected; when it is detected that the multi-connected air-conditioning system meets the oil return condition, the operation frequency of a compressor of the multi-connected air-conditioning system is adjusted to the preset frequency; and in the process that the operation frequency of the compressor is adjusted to the preset frequency, the opening degree of a valve of an inner unit, in therefrigeration mode, of the multi-connected air-conditioning system is adjusted to the preset opening degree from the current opening degree so that oil return control can be conducted on the multi-connected air-conditioning system, and the preset opening degree is larger than the current opening degree. Through the air conditioner oil return control method and device, the problem that in relatedtechnologies, when a heat recovery multi-connected unit conducts oil return, the opening degree of an electronic expansion valve of a refrigeration inner unit is decreased, thus, compressor overflowing is caused, and oil return is influenced is solved.

A special evaporator for a heat-pipe refrigerating hybrid air-conditioner contains a finned pipe heat exchanger, a gas collecting pipe, a liquid distribution head, a liquid distribution pipe and a heat exchange pipe. The special evaporator is characterized in that a liquid collecting pipe is arranged between the heat exchange pipe and the liquid separating pipe, and the liquid separating pipe runs through the liquid collecting pipe to insert and stretch into the heat exchange pipe; the gas collecting pipe adopts a U-shaped pipe which is composed of a first rising vertical pipe, a second rising vertical pipe and an oil return bend pipe; and the heat exchange pipe is communicated with the first rising vertical pipe through the finned pipe heat exchanger. The special evaporator of the invention realizes the fusion of performance and safety of a vapor compression refrigerating mode and a heat-pipe natural circulation mode on the same evaporator through a special pipeline design, ensures oil return safety of the vapor compression refrigerating mode, and reduces the pipe resistance of the evaporator. The evaporator which is applicable to the heat-pipe refrigerating hybrid air-conditioning unit has simple structure, low cost and obvious effect, thus effectively solving the problems of oil return and resistance reduction of the unit, and improving the operating reliability and high efficiency.

The invention discloses a variable-frequency air conditioner and a compressor oil return system thereof. The compressor oil return system comprises a compressor, an oil separator and an oil level controller, wherein an air suction port, a first air exhaust port and an oil injection hole are formed in the compressor; the oil separator communicates with the first air exhaust port through a first air exhaust tube; the oil separator is further provided with a second air exhaust port and an oil outlet; the oil level controller is used for controlling whether the compressor intakes oil or not; the oil level controller comprises a switch; one end of the oil level controller communicates with the oil injection hole; the other end of the oil level controller communicates with the oil outlet through an oil outlet tube; the oil level controller comprises a switch; when oil in the compressor is insufficient, the switch is opened; and when oil in the compressor is sufficient, the switch is closed. By adopting the variable-frequency air conditioner, the problem that the compressor is difficult to return oil at a far distance under low frequency can be effectively solved, so that the service life of the compressor is prolonged; and the variable-frequency air conditioner is simple in structure and is reasonable in design.

The invention discloses a water-source ultrahigh temperature heat pump which comprises a compressor, an oil separator, a pressure maintenance valve, a condenser, an evaporator, an oil cooler, first and second drying filters, a throttling device, a sub-cooler, first, second, third and fourth stop valves, an oil flow switch, first, second, third and fourth solenoid valves and a liquid spraying valve. A large quantity of parts used on a present common heat pump unit can be used by thewater-source ultrahigh temperature heat pump; the research and development cost is lowered; the production cost is effectively lowered; the energy efficiency ratio of the heat pump is increased; the oil return problem is solved; the water-source ultrahigh temperature heat pumpcan long-term reliably and stably run under high-temperature severe working conditions.

Provided is an air conditioning refrigeration system. An outlet of a high-back-pressure rotary compressor is connected with an inlet of a condenser, an outlet of the condenser is connected with a liquid inlet of a heat regenerator, a liquid outlet of the heat regenerator is connected with an inlet of an expansion valve, an outlet of the expansion valve is connected with an inlet of an evaporator, an outlet of the evaporator is connected with a gas inlet of the heat regenerator, and a gas outlet of the heat regenerator is connected with an inlet of the high-back-pressure rotary compressor. Refrigerating fluid enters the high-back-pressure rotary compressor firstly, and is compressed into high-temperature high-pressure gas entering the condenser, the gas is condensed into intermediate-temperature high-pressure liquid, and heat is discharged into air. The refrigerating fluid flows through the heat regenerator and enters the expansion valve, and is throttled to be in a low-temperature low-pressure gas-liquid mixing state, then the refrigerating fluid enters the evaporator, heat exchange is carried out on the refrigerating fluid and the air in the environment, the temperature of the air is reduced, and therefore the refrigeration effect is achieved. According to the system, efficiency and stability are improved, oil return is good, the probability of blocking capillary tubes is reduced, and the injection amount of the refrigerating fluid is reduced.

The invention relates to the technical field of data center refrigeration air conditioners, in particular to a multi-connected air conditioning system and a running control method thereof. The multi-connected air conditioning system comprises a main controller, an outdoor unit and a plurality of parallelly-connected indoor units, each indoor unit is connected with the outdoor unit through a refrigerant pipeline, the outdoor unit comprises a compressor and a condenser which are mutually connected, the compressor is connected with the main controller in an electric signal manner, each indoor unit comprises at least two parallelly-connected indoor unit bodies, each indoor unit body comprises an electronic expansion valve and a first connector connected with the electronic expansion valve, and the first connectors are connected with the main controller in an electric signal manner. The multi-connected air conditioning system is simple in structure, simple and convenient to install, small in occupied space, good in economy and applicable to different types of compressors, investment cost and installation cost are reduced, and the number of the indoor unit bodies can be flexibly adjusted according to actual use conditions, so that versatile user requirements are met.

The invention discloses a cabinet-based direct evaporative cooled machine room air-conditioning system. The system comprises a refrigerant circuit, an oil return circuit and a cooling water circuit. According to the cabinet-based direct evaporative cooling machine room air-conditioning system, refrigerants are directly delivered to a server and are directly evaporated to cool the server through evaporators arranged on the server. Compared with a machine room air-conditioning system cooled by supplying air conventionally, the system has the advantages of high heat dissipation power, high efficiency, small size and the like. Compared with a conventional refrigerant evaporative cooled air-conditioning system, the machine room air-conditioning system directly delivers all liquid to the evaporators through a low-pressure circulating barrel and a first variable frequency magnetic force pump, so that the system has the advantages that the pressure drops of refrigerants in the evaporators are small; the back temperature of a compressor is low, and a heat exchange system is large; through the arrangement of the oil return circuit, the problem of oil return of the system is solved creatively, and the system has the characteristics of high comprehensive energy efficiency and the like.

A variable capacity heat pump system, which comprises the separate device and the main system, the separate device is set between the first throttling gear and the crossing of the condensator exit and the compressor exit, which consist of the rectified column and the water storage tank which fill the working substance with low boiling-point. The system is that changes the thickness of the working substance by the separation and distills of the high and low boiling-point working substance, which can fulfill the need of different capability. The invention can avoid the damage of lack oil of compressor.

The invention discloses an efficient full-wet inner surface evaporator which is mainly formed by connecting a refrigerant distributor, a first evaporating heat exchange pipe, a first refrigerant air return pipe, a first refrigerant air return main pipe, a gas-liquid separator and a refrigerant air return pipe in sequence. The evaporator also comprises a secondary evaporating heat exchange assembly, wherein the secondary evaporating heat exchange assembly is formed by connecting a secondary evaporating air inlet main pipe, a secondary evaporating heat exchange pipe, a secondary refrigerant air return pipe and a secondary evaporating air return main pipe; and a refrigerant entering the gas-liquid separator enters the secondary evaporating heat exchange pipe for carrying out secondary evaporation by the secondary evaporating air inlet main pipe and returns into the gas-liquid separator by syphonage. The invention has certain ingenuity on improving the heat exchange efficiency of the evaporator and solving the problems of wet compression and oil return, can improve the heat transfer performance of the evaporator and improve the performance coefficient of a unit by 15 percent or so, is not only suitable for a pure medium but also suitable for a mixed medium.

The invention discloses an air conditioning system. The air conditioning system comprises a refrigeration module, a first intermediate heat exchanger, a first liquid storage tank, a first circulation pump and a tail end module, wherein the first intermediate heat exchanger comprises a first cold source side and a first hot source side; a first closed cycle is formed by the first cold source side and the refrigeration module; and the first hot source side, first liquid storage tank, first circulation pump and tail end module communicate in succession via a refrigerant pipeline to form a second closed cycle. Through application of the air conditioning system provided by the invention, problems of water leakage and oil returning existing in large air conditioning systems could be solved, and reliability of the air conditioning system could be enhanced in comparison with the prior art.

A variable capacity heat pump system, which comprises the separate device and the main system, the separate device is set between the first throttling gear and the crossing of the condensator exit and the compressor exit, which consist of the rectified column and the water storage tank which fill the working substance with low boiling-point. The system is that changes the thickness of the working substance by the separation and distills of the high and low boiling-point working substance, which can fulfill the need of different capability. The invention can avoid the damage of lack oil of compressor.

The invention provides a parallel compressors unit capable of self-adaptively operating at low load. The parallel compressors unit comprises compressors, an oil separator, a condenser, a liquid storage device, a filter, a visual liquid lens, an expansion valve and an evaporator, which are connected in sequence in an end-to-end manner. The output end of the oil separator is connected with the input ends of the compressors through a hot gas bypass solenoid valve and a hot gas bypass valve and connected with the input end of the evaporator through an oil supply solenoid valve, and the output end of the filter is connected with the input ends of the compressors through a superheat-removing solenoid valve and a superheat-removing expansion valve. Meanwhile, the invention further provides an implementation method of the self-adaptive operation of the parallel compressors unit at low load. According to the parallel compressors unit and the implementation method thereof, by improving the structure of the parallel compressors unit, the frequent start and stop of one compressor is avoided when the cool storage load is reduced to be below the lowest regulation load, and the problems of temperature fluctuation and oil return of the evaporator are avoided. Meanwhile, a manual control mode is added, so that the parallel compressors unit is stable and saves energy.

The invention discloses a dry evaporator and a condensing oil gas recovery device comprising the dry evaporator. The dry evaporator comprises an evaporator body (1), a refrigerant inlet (2) and a liquid collection bag (3) which are positioned on the lower part of the evaporator body, and a gas collection bag (4) and a refrigerant outlet (5) which are positioned on the upper part of the evaporator body, wherein the refrigerant inlet (2) is connected to the liquid collection bag (3); the refrigerant outlet (5) is connected to the gas collection bag (4); the liquid collection bag (3) is communicated with the gas collection bag (4) in the evaporator body (1) through a refrigerant pipeline; the refrigerant outlet (5) is connected with an air suction pipe of a compressor; and the dry evaporator is characterized by also comprising at least one oil return pipe (6), wherein a lower port of the oil return pipe (6) is communicated with the liquid collection bag (3), and an upper port of the oil return pipe (6) is communicated with the air suction pipe of the compressor. The dry evaporator has a simple oil return structure, so that refrigeration oil can timely return to the compressor at low evaporating temperature, the compressor is stably operated, and the oil gas recovery efficiency is high.

A high efficient liquid filling coupling heat exchanger has a casing. In the casing, a heat exchanging pipe beam is vertically fixed in the casing by a pipe board and divides the casing into an upper and a lower monitor cavity. An evaporate side refrigerating fluid inlet and a gas outlet are arranged corresponding to the monitor cavity. A condensate side refrigerating gas inlet and a condensate liquid outlet are arranged corresponding to the monitor cavity. An oil-return opening, a liquid viewing mirror and a liquid level controller are arranged on the refrigerating fluid level corresponding to the monitor cavity; the heat exchanging pipe is composed of a base pipe and an axially rib that is integrally formed on the base pipe and with a height that is as 0.2 to 0.8 time as an outer diameter of the base pipe; the heat exchanging pipe is provided with an axially inner rib piece that is integrally formed with the base pipe. The invention, because of solving the condenser oil-returning problem of the evaporate side loop, enables the evaporate side to adopt the liquid-filling heat exchanging structure an operation manner and exchanges heat for the heat exchanging pipe by a highly finned coefficient, so as to improve energy efficiency of the heat exchanger.

The invention relates to a lubrication and diversion structure of a dual-clutch transmission. The lubrication and diversion structure comprises a clutch casing, a shaft end bearing which is connected to the clutch casing in a matching manner and corresponds to a clutch installation cavity and a transmission shaft, and the left end of the transmission shaft is connected with the shaft end bearing in a matching manner. The lubrication and diversion structure is characterized in that the transmission shaft is provided with a central oil duct which penetrates through the shaft axis of the transmission shaft and a plurality of lubrication small holes communicated with the central oil duct, lubricating oil reaches positions which need to be lubricated through the plurality of lubrication small holes, a diversion member is arranged at the left side of the shaft end bearing, the diversion member is communicated with the central oil duct of the transmission shaft, a casing upper shunting groove is arranged next to the upper part of the diversion member, a casing lower upper shunting groove is arranged next to the lower part of the diversion member. The lubrication and diversion structure of the dual-clutch transmission can satisfy the oil return requirement of the dual clutch, and also can satisfy the shafting lubrication requirement, the lubricating system is simplified, and the lubrication efficiency is improved.

The invention discloses a non-returning and filtering device for a grease gun, and belongs to the technical field of oil injection tools. The non-returning and filtering device comprises a non-returning and filtering inner cavity in threaded connection with a grease gun head, a non-returning device arranged in the non-returning and filtering inner cavity, and a filtering net arranged in the non-returning and filtering inner cavity. The other end of the non-returning and filtering inner cavity is connected with an oil pipe in a threaded manner. One end of the oil pipe stretches into the non-returning and filtering inner cavity and is in threaded connection with the non-returning and filtering inner cavity, and an oil injection nozzle is in threaded connection to the other end of the oil pipe. The non-returning device is composed of a spacer with a hole, a spring and a non-returning ball. One end of the spring abuts against an oil pipe port located in the non-returning and filtering inner cavity, and the non-returning ball is clamped between the other end of the spring and the spacer with the hole. The non-returning and filtering device is reasonable in structure and easy to manufacture. The problems of oil leakage and oil returning of the grease gun are solved through the additionally-arranged lubricating oil non-returning device, and the problem of blockage of the grease gun head is solved through the filtering net. The non-returning and filtering device is wide in application range, easy to operate, convenient to carry, wide in application range and capable of improving the work efficiency.

This invention relates to an air conditioner including a compressor, a four-way valve, a condenser, a first and second evaporators and a first and second electromagnetic valves, in which, the first evaporator is serial to the first electromagnetic valve to compose a first serial device, a second evaporator is serial to the second electromagnetic valve to make up of a second serial device, which is parallel to the first serial device to form a parallel device characterizing in also including heating and cooling capillaries, one to four single-way valves, the heating capillary is serial to the first single-way valve to make up of a third serial device, the cooling capillary is serial to the second single-way valve to constitute a fourth serial device, the third and fourth serial devices make up of a bridge loop device with the third and fourth single-way valve, which makes the trend of a refrigerant flowing in the evaporator the same either at the heating state or the cooling state and the outlet of the evaporator is always connected with the air entry of the compressor.

This invention relates to an air conditioner including a compressor, a four-way valve, a condenser, a first and second evaporators and a first and second electromagnetic valves, in which, the first evaporator is serial to the first electromagnetic valve to compose a first serial device, a second evaporator is serial to the second electromagnetic valve to make up of a second serial device, which is parallel to the first serial device to form a parallel device characterizing in also including heating and cooling capillaries, one to four single-way valves, the heating capillary is serial to the first single-way valve to make up of a third serial device, the cooling capillary is serial to the second single-way valve to constitute a fourth serial device, the third and fourth serial devices make up of a bridge loop device with the third and fourth single-way valve, which makes the trend of a refrigerant flowing in the evaporator the same either at the heating state or the cooling state and the outlet of the evaporator is always connected with the air entry of the compressor.

The invention discloses a running control method of a double-stage compression heat pump system and a heat pump system, and aims at providing a method and a system for balancing and coordinating lubricating oil between high pressure stage and low pressure stage as well as realizing uniform power consumption of each compressor in running. The method comprises the steps of changing output points ofa high pressure stage compressor set and a low pressure stage compressor set in order to enable the high pressure stage compressor set to run as the low pressure stage compressor set and enable the low pressure stage compressor set to run as the high pressure stage compressor set when the single running time t of the compressor sets is beyond the alternative running time cycle T; starting compressor sets based on the principle of high and low pressure stage compressor launching ratio m and the principle of firstly starting the compressor with the minimum running time; adding 1 to the running time corresponding to the started compressor; synchronously clearing the single running time of the compressor sets in previous running cycle; starting to record the single running time of the compressor set in the current cycle; and starting new running cycle. According to the method and the system, the power consumption of each compressor in running is uniform; the system reliability is high; theoil retuning uniformity is realized.

The invention discloses a cascaded refrigeration system in which a variable flow single working substance is connected in parallel with a condenser and an evaporator. Each refrigeration compressor unit of the present invention is made up of refrigeration compressor and four solenoid valves, condenser, evaporator, and the discharge end of each refrigeration compressor is respectively connected with first solenoid valve and second solenoid valve, and each refrigeration compressor The suction end of the machine is respectively connected with the third solenoid valve and the fourth solenoid valve, the first solenoid valve connected to each refrigeration compressor is connected with the inlet of the condenser, and the outlet of each condenser is connected in parallel and passes through the high-temperature throttling valve It is connected to the inlet of the evaporating side of the condensing evaporator. The second solenoid valve connected to each refrigeration compressor is connected in parallel to the inlet of the condensing evaporator. The third solenoid valve connected to each refrigerating compressor is connected in parallel to the evaporation side of the condensing evaporator. The outlet connection, the fourth electromagnetic valve connected to each refrigeration compressor is connected to the outlet of the evaporator, and the inlet of each evaporator is connected in parallel to the outlet of the condensing side of the condensing evaporator through a low-temperature throttling valve. The cascade refrigerating system of the invention is composed of a single working medium, without expansion vessels and other devices, and the system structure is simple.

The invention relates to the technical field of heat pump air conditioning, and discloses a tube-plate type heat pump system comprising a four-way valve, a throttling valve and a tube-plate type heatexchanger. The tube-plate type heat exchanger comprises an inlet end arranged on the top and an outlet end arranged at the bottom. The tube-plate type heat pump system further comprises a first three-way piece. Three ports of the first three-way piece are connected with a first port, an inlet end and an outlet end of the four-way valve correspondingly. The tube-plate type heat pump system furthercomprises a second three-way piece. Three ports of the second three-way piece are connected with a first port, an inlet end and an outlet end of the throttling valve correspondingly. According to thetube-plate type heat pump system, by arranging the first three-way piece and the second three-way piece, a circulation refrigerant mixed with lubricating oil flows from top to bottom in the tube-platetype heat exchanger both in the refrigerating circulation working condition mode and the heating circulation working condition mode; the problem that the refrigerant accumulates at the tube bottom when flowing in gaps in sheets from bottom to top is solved; the tube-plate type heat pump system is simple in structure, convenient to use and practical; and by means of the tube-plate type heat exchanger, the aim of achieving two purposes through one machine can be better achieved.

The invention discloses a grease gun capable of preventing flowing back of lubricating oil, and belongs to the technical field of oil injecting tools. The grease gun comprises an oil cylinder, a gun head and a back cover respectively positioned at the head part and the bottom of the oil cylinder, and a handle positioned on one side of the oil cylinder. The grease gun is characterized in that the end part of the gun head is in threaded connection with an oil pipe; one end of the oil pipe extends in an inner cavity of the gun head, and is in threaded connection with the same; the other end of the oil pipe is in threaded connection with a conical oil injecting nozzle; a hole separation plate, a spring and a stop round ball are arranged in an inner cavity of the gun head; one end of the spring is butted against a port of the oil pipe positioned in the inner cavity of the gun head; the stop round ball is clamped between the other end of the spring and the hole separation plate; and the diameter of the stop round ball is larger than the aperture of the hole separation plate. The grease gun is reasonable in structure and easy to manufacture, and adds a lubricating oil stop device to solve the oil leaking and returning problems. The grease gun is wide in application range, simple in operation, convenient for carrying and wide in application range, and improves the working efficiency.

The invention provides a thermal management system and a vehicle with the same, the thermal management system comprises a heat pump air conditioning subsystem, the heat pump air conditioning subsystemcomprises: a compressor; an evaporator; and a first pipeline assembly which comprises a first pipeline and an oil separator, one end of the first pipeline is connected with the compressor, and the other end of the first pipeline is connected with the evaporator; the oil separator is arranged on the first pipeline, the oil separator comprises an air inlet, an air outlet and an oil return port, theair inlet and the air outlet are both connected with the first pipeline, and the oil return port is connected with the compressor. The thermal management system can solve the problem that a compressor in a thermal management system in the prior art cannot return oil.

The invention discloses a fluorine pump system and a control method thereof. A condenser is a double-coil heat exchanger and comprises a condenser coil A and a condenser coil B; the compressor, the condenser coil A, the electronic expansion valve and the intermediate heat exchanger form a first refrigeration cycle, the indoor terminal, the electric flow regulating valve III, the intermediate heat exchanger, the electric flow regulating valve II, the liquid storage tank and the refrigerant pump form a second refrigeration cycle, and the first refrigeration cycle and the second refrigeration cycle exchange heat in the intermediate heat exchanger; and the indoor tail end, the electric flow regulating valve IV, the condenser coil pipe B, the electric flow regulating valve I, the liquid storage tank and the refrigerant pump form a third refrigeration cycle. The refrigerant in the first refrigeration cycle of the intermediate heat exchanger is separated from the refrigerant at the tail end in the supply chamber, so that the oil return problem of the refrigeration system under the conditions of long pipeline and height difference is solved, and higher applicability is achieved; meanwhile, the system has three operation modes, a compressor or a natural cold source can be used according to different working conditions, and energy consumption is reduced.

The invention discloses a variable-flow single-working medium cascade heat pump system with parallel heat exchangers. According to the invention, each compressor unit comprises a compressor, a four-way reversing valve, four electromagnetic valves, a first heat exchanger and a second heat exchanger, wherein an exhaust end of each compressor is connected with the first connector of the corresponding four-way reversing valve; a suction end of each compressor is connected with the third connector of the corresponding four-way reversing valve; one end of each first electromagnetic valve is connected with one end of the corresponding second electromagnetic valve in parallel and then is connected with the second connector of the corresponding four-way reversing valve; the other ends of the first electromagnetic valves pass through the first heat exchangers, then are connected in parallel, and are connected with the second connector of a condensation evaporator through a first throttle valve; the other ends of the second electromagnetic valves are connected in parallel and then are connected with the third connector of the condensation evaporator; one ends of the third electromagnetic valve and the fourth electromagnetic valve are connected in parallel and then are connected with the fourth connector of the four-way reversing valve; the other ends of the third electromagnetic valves are connected in parallel and then are connected with the first connector of the condensation evaporator; the other ends of the fourth electromagnetic valves are connected in parallel and then are connected with the fourth connector of the condensation evaporator through the second heat exchangers and a second throttle valve. The cascade heat pump system of the invention is formed by single working medium, and does not contain an expansion container and other devices, so that the structure is simple.

The invention discloses a variable-flow single-working medium cascade refrigeration system with a common condenser and a common evaporator. According to the invention, each refrigeration compressor unit is composed of a refrigeration compressor and four electromagnetic valves, wherein an exhaust end of the refrigeration compressor is connected with the corresponding first electromagnetic valve and the corresponding second electromagnetic valve; a suction end of each refrigeration compressor is connected with the corresponding third electromagnetic valve and the corresponding fourth electromagnetic valve; the first electromagnetic valves connected to the refrigeration compressors are connected in parallel and then are connected with an inlet in the condenser; the second electromagnetic valves connected to the refrigeration compressors are connected in parallel and then are connected with a condensation side inlet in a condensation evaporator; the third electromagnetic valves connected to the refrigeration compressors are connected in parallel and then are connected with an evaporation side outlet in the condensation evaporator; the fourth electromagnetic valves connected to the refrigeration compressors are connected in parallel and then are connected with an outlet in the evaporator; an outlet in the condenser is connected with an evaporation side inlet in the condensation evaporator through a high temperature level throttle valve; a condensation side outlet in the condensation evaporator is connected with an inlet in the evaporator through a low temperature level throttle valve. The cascade refrigeration system of the invention is formed by single working medium, and does not contain an expansion container and other devices, so that the structure is simple.

The invention discloses an oil returning device of a refrigerating system. The oil returning device comprises an evaporator, an oil loop, an ascending vertical tube, a horizontal cross tube and a gas-liquid separator which are connected successively. The oil returning device also comprises an auxiliary oil returning mechanism which comprises a first pressure transmitter, a second pressure transmitter, a hot gas sprayer nozzle, an electromagnetic valve and an electric control unit; the first pressure transmitter is arranged on a connecting pipeline of the gas-liquid separator and a compressor,the second pressure transmitter is arranged on a connecting pipe of the evaporator and the oil loop, one end of the hot gas spray nozzle is connected to a high pressure exhaust port of the compressorwhile the other end of the hot gas spray nozzle is connected to the side, close to the ascending vertical tube, of the oil loop, and the electromagnetic valve is arranged on the hot gas spray nozzle;the electric control unit is used for controlling the electromagnetic valve to open and close according monitored values of the first and second pressure transmitters. The invention also discloses anoil returning method of the refrigerating system. The oil returning device and the oil returning method disclosed by the invention solve the oil returning problem of the refrigerating system in an extremely low temperature operating condition fundamentally, and the oil returning device is simple in structure, reliable in method, high in degree of automation and safe to use.

The invention discloses a flooded type compound cooling-air unit, which consists of a compressor, a condenser, an evaporator, a liquid connecting tube, a liquid control solenoid valve, a throttling device and an air connecting tube. Thee cooling-air unit has the technical features as follows: the evaporator is a cold flooded type evaporator; a three-way valve is arranged at the junction of the inlet pipe of the condenser and a heating tube branch. By adopting the cold flooded type evaporator, the cooling-air unit not only solves the matching problem on charging volume of natural circulating refrigerants and refrigeration circulating refrigerants, but also guarantees the effect of safe oil return and refrigerants distribution, and improves the reliability and operational performance of thecooling-air unit; by adopting the three-way valve, the cooling-air unit reduces failure rate and improves reliability. The cooling-air unit of the invention not only can be used for mobile communication base stations and service rooms as special machines of a machine room, but also can be used as cooling devices for a high-temperature refrigeratory or other heating places. The cooling-air unit ofthe invention is safe and reliable, efficient and energy-saving.