CN106091463A - 4K thermal coupling regenerating type low-temperature refrigerator based on controlled heat pipe and refrigerating method thereof - Google Patents

Abstract

The invention discloses a kind of 4K thermal coupling regenerating type low-temperature refrigerator based on controlled heat pipe and refrigerating method thereof, Cryo Refrigerator includes compressor, multistage regenerating type low-temperature refrigerator and connects the heat bridge of refrigeration machine at different levels, and uses controlled heat pipe to substitute traditional material copper as heat bridge.Controlled heat pipe relies on the gas-liquid phase transition heat transfer of working fluid, and thermal resistance is the least, the big several orders of magnitude of the thermal conductivity ratio copper of controlled heat pipe under unit mass；Being filled with noble gas in controlled heat pipe, the thermal resistance of its condensation segment reduces along with the increase of heat flow density, and therefore the operating temperature of heat pipe only has small change；Controlled heat pipe has the advantages such as lightweight, volume is little compared to copper, is particularly well-suited to the fields such as Space Military.

Description

4K thermally coupled regenerative cryogenic refrigerator based on controllable heat pipe and its refrigeration method

technical field

The invention relates to a refrigerator, in particular to a 4K heat-coupled regenerative low-temperature refrigerator based on a controllable heat pipe and a refrigeration method thereof.

Background technique

With the continuous development of science and technology, due to the advantages of high reliability, long life, high efficiency, simple control, etc. more and more widely used.

Multi-stage regenerative cryogenic refrigerators can be divided into thermal coupling and gas coupling according to the coupling mode. The thermally coupled structure is that the high-temperature regenerator precools the low-temperature regenerator through a thermal bridge. Compared with gas coupling, thermal coupling generally uses multiple compressors to drive separately, and there is no distribution problem of working fluid mass flow between stages, which is convenient for experiment and theoretical analysis; the optimal operating frequency and inflation pressure of regenerators in different temperature zones The gas-coupled type cannot be optimized separately, while the heat-coupled type has no mass flow coupling between the low-temperature stage and the pre-cooling stage at low temperatures. performance. Therefore, multi-stage regenerative cryogenic refrigerators generally adopt thermal coupling.

Traditional multi-stage regenerative cryogenic refrigerators generally use copper as the thermal bridge. There are many problems when copper is used as a thermal bridge: in order to enhance the heat transfer capacity, traditional thermal bridges generally use solid copper tubes, but copper has a high density and a large mass, which is not conducive to reducing the load of the refrigerator; copper has high thermal resistance and heat transfer The temperature difference is large, and as the heat flux density (pre-cooling capacity) in the heat bridge increases, the heat transfer temperature difference increases, and the irreversible heat loss of the regenerator increases, which is not conducive to improving the cooling efficiency and reducing the no-load cooling temperature, especially for 20K In the temperature zone, the increase in the heat transfer temperature difference will lead to a sharp increase in the irreversible heat transfer loss of the regenerator. Therefore, how to optimize the thermal bridge design is of great significance for the optimization of multi-stage regenerative cryogenic refrigerators.

Contents of the invention

The technical problem to be solved by the present invention is to provide a controllable heat pipe-based 4K thermally coupled regenerative low-temperature refrigerator and its refrigeration method with good refrigeration efficiency and high reliability for the defects involved in the background technology.

The present invention adopts the following technical solutions for solving the problems of the technologies described above:

A 4K thermally coupled regenerative cryogenic refrigerator based on controllable heat pipes, including the first compressor, the second compressor, the first gas storage, the first inertia tube, the first pulse tube, the first regenerator, and the second regenerator. Heater, tertiary regenerator, tertiary gas storage, tertiary inertial tube, primary diversion tube, primary thermal bridge, secondary gas storage, secondary inertial tube, secondary pulse tube, tertiary pulse tube, Secondary diversion tube, secondary heat bridge and third stage diversion tube;

Among them, the first compressor, the first-stage regenerator, the first-stage diversion pipe, the first-stage pulse pipe, the first-stage inertia tube, and the first-stage gas storage are connected in sequence; the outlet of the second compressor is respectively connected to the second-stage regenerator, The inlet of the third-stage regenerator is connected; the second-stage regenerator, the second-stage diversion pipe, the second-stage pulse pipe, the second-level inertia tube, and the second-stage gas storage are connected in sequence; the third-stage regenerator and the third-stage diversion pipe , third-level pulse tube, third-level inertia tube, and third-level gas storage are connected in sequence; the first-level heat bridge wraps the outlet of the first-level regenerator, the middle part of the second-level regenerator, and the upper half of the third-level regenerator part, for thermal coupling connection; the secondary thermal bridge respectively wraps the outlet of the secondary regenerator and the lower half of the tertiary regenerator for thermal coupling connection;

Both the first heat bridge and the second heat bridge use controllable heat pipes as heat conducting materials.

The above-mentioned controllable heat pipe realizes heat conduction in different temperature zones by filling different working fluids, realizes heat conduction in 80K temperature zone by filling nitrogen gas, and realizes heat conduction in 20K temperature zone by filling hydrogen gas.

The working principle of the controllable heat pipe is as follows: the condensation section of the controllable heat pipe is connected with a gas storage chamber, which is filled with inert gas. When the heat pipe is not working, the inert gas and the working medium vapor are evenly mixed. When the heat pipe is working, the working medium vapor in the evaporating section carries the inert gas and flows to the condensing section. The working fluid vapor is condensed into liquid in the condensation section and returns to the evaporation section through the tube core. Inert gas builds up continuously at the cold end. After a period of time, all the inert gas accumulates in the gas storage chamber and condensation section, forming a gas lock. When the working temperature of the heat pipe increases, the internal vapor pressure increases, compressing the air plug, increasing the effective heat dissipation area of the condensation section, reducing the thermal resistance of the condensation section, increasing the cooling capacity, and suppressing the rise in the working temperature of the heat pipe. On the contrary, when the working temperature of the heat pipe decreases, the air plug expands, increasing the thermal resistance of the condensation section, so that the working temperature of the heat pipe does not drop any longer. In this way, the working temperature of the heat pipe can be kept within a certain range.

The present invention also discloses the refrigeration method of the controllable heat pipe-based 4K thermally coupled regenerative cryogenic refrigerator, which includes the following steps:

Step 1), the gas working medium is compressed by the first compressor and firstly enters the first-stage regenerator for pre-cooling, and then enters the first-stage pulse tube through the first-stage diversion tube, and the first-stage pulse tube passes through the first-stage gas storage and the first-stage The inertia tube creates a phase difference between the mass flow and the pressure wave of the gas working medium to enhance heat transfer. The gas working medium is compressed at the hot end of the first-stage pulse tube to release heat, and then expands and cools at the cold end to produce a cooling effect, and The middle part of the second-stage regenerator and the upper part of the third-stage regenerator are pre-cooled through the first-stage thermal bridge;

Step 2), a part of the gas working fluid in the second compressor passes through the precooled secondary regenerator, the mass enthalpy flow is reduced, and then the gas working fluid enters the secondary pulse tube through the secondary flow guide tube, and the secondary pulse The tube passes through the secondary gas reservoir and the secondary inertia tube to generate a phase difference between the mass flow and pressure wave of the gas working medium to enhance heat transfer. The gas working medium is compressed at the hot end of the secondary pulse tube to release heat, and then cool End expansion and cooling, resulting in refrigeration effect, and precooling the lower half of the third-stage regenerator through the second-stage heat bridge;

Step 3), after another part of the gas working fluid in the second compressor passes through the precooled three-stage regenerator, the mass enthalpy flow is significantly reduced, thereby significantly increasing the net cooling capacity of the cold end of the three-stage pulse tube and reducing the no-load refrigeration temperature.

The present invention also discloses another 4K thermally coupled low-frequency regenerative cryogenic refrigerator based on controllable heat pipes:

Including the first compressor, the first-level gas storage, the first-level inertia tube, the first-level pulse tube, the first-level regenerator, the second-level regenerator, the first-level diversion tube, the first-level heat bridge, the second-level gas storage, and the second-level The first-level inertial tube, the second-level pulse tube and the second-level diversion tube;

Among them, the first compressor is respectively connected with the inlets of the primary regenerator and the secondary regenerator; connected in sequence; the secondary regenerator, the secondary diversion tube, the secondary pulse tube, the secondary inertia tube, and the secondary gas storage are connected in sequence; the primary thermal bridge wraps the outlet of the primary regenerator and the secondary The middle part of the stage regenerator for thermal coupling connection;

The first heat bridge (12) uses a controllable heat pipe as a heat conducting material.

The present invention also discloses the refrigeration method of the 4K thermally coupled low-frequency regenerative cryogenic refrigerator based on the controllable heat pipe, which includes the following steps:

Step 1), a part of the gas working medium in the first compressor first enters the first-stage regenerator for pre-cooling, and then enters the first-stage pulse pipe through the first-stage diversion tube, and the first-stage pulse pipe passes through the first-stage gas storage and the first-stage The inertia tube creates a phase difference between the mass flow and the pressure wave of the gas working medium to enhance heat transfer. The gas working medium is compressed at the hot end of the first-stage pulse tube to release heat, and then expands and cools at the cold end to produce a cooling effect, and Precool the middle part of the secondary regenerator through the primary heat bridge;

Step 2), another part of the gas working fluid in the first compressor passes through the precooled secondary regenerator, and the mass enthalpy flow is significantly reduced, thereby significantly increasing the net cooling capacity of the cold end of the secondary pulse tube and reducing the no-load refrigeration temperature .

The invention innovatively uses a controllable heat pipe to replace the traditional material copper as a heat bridge. Compared with copper heat bridges, controllable heat pipes have the following advantages:

1. The inside of the heat pipe mainly relies on the gas-liquid phase change of the working fluid to transfer heat, and the thermal resistance is very small, so it has a high thermal conductivity. The controllable heat pipe can transfer several orders of magnitude more heat than copper per unit mass;

2. The steam in the inner cavity of the heat pipe is in a saturated state, and the pressure drop and temperature drop caused by the saturated steam flowing from the evaporating section to the condensing section are very small, so the heat pipe has excellent isothermal properties;

3. The controllable heat pipe is filled with inert gas, and a gas storage chamber is connected to the condensation section. With the change of the heat flux density in the heat pipe, the inert gas expands or compresses in the storage chamber, changing the effective heat dissipation area of the condensation section, thereby changing The thermal resistance of the condensing section maintains only small changes in the operating temperature of the heat pipe.

Description of drawings

Figure 1 is a schematic diagram of a 4K thermally coupled regenerative cryogenic refrigerator based on a controllable heat pipe;

Figure 2 is a schematic diagram of a 4K thermally coupled low-frequency regenerative cryogenic refrigerator based on a controllable heat pipe;

Figure 3 is a schematic diagram of the controllable heat pipe;

Fig. 4 shows the effect of the temperature of the hot end of the regenerator on the heat loss of the regenerator under different pressure ratios of the cold end of the helium-4 working fluid;

Figure 5 is a comparison of the thermal conductivity values of copper and heat pipes per unit mass.

In the figure, 1-the first compressor, 2-the second compressor, 3-the first-level gas storage, 4-the first-level inertia tube, 5-the first-level pulse tube, 6-the first-level regenerator, 7-the second level Regenerator, 8-third-level regenerator, 9-third-level gas storage, 10-third-level inertia tube, 11-first-level diversion tube, 12-first-level heat bridge, 13-second-level gas storage, 14- Second-level inertia tube, 15-second-level pulse tube, 16-third-level pulse tube, 17-second-level diversion tube, 18-second-level thermal bridge, 19-third-level diversion tube.

detailed description

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:

As shown in Figure 1, a 4K thermally coupled regenerative cryogenic refrigerator based on a controllable heat pipe includes a first compressor 1, a second compressor 2, a first-stage gas storage 3, a first-stage inertial tube 4, and a first-stage pulse tube 5. First-level regenerator 6, second-level regenerator 7, third-level regenerator 8, third-level gas storage 9, third-level inertia tube 10, first-level diversion tube 11, first-level heat bridge 12, second-level Gas storage 13, secondary inertia tube 14, secondary vessel 15, tertiary vessel 16, secondary flow guide tube 17, secondary thermal bridge 18 and third level flow guide tube 19;

Among them, the first compressor 1, the first-stage regenerator 6, the first-stage guide tube 11, the first-stage pulse tube 5, the first-stage inertia tube 4, and the first-stage gas storage 3 are connected in sequence; the outlets of the second compressor 2 are respectively It is connected with the inlet of the secondary regenerator 7 and the inlet of the tertiary regenerator 8 ; connected; the third-stage regenerator 8, the third-stage diversion pipe 19, the third-stage pulse tube 16, the third-stage inertia tube 10, and the third-stage gas storage 9 are sequentially connected; the first-stage heat bridge 12 respectively wraps the first-stage heat recovery The outlet of the secondary regenerator 6, the middle part of the secondary regenerator 7, and the upper half of the third-stage regenerator 8 are thermally coupled and connected; the secondary heat bridge 18 wraps the outlet of the secondary regenerator 7 and the third-stage regenerator The lower half of the heater 8 is thermally coupled.

The above-mentioned 4K heat-coupled regenerative low-temperature refrigerator based on controllable heat pipes uses controllable heat pipes as the heat conduction materials of the primary heat bridge 12 and the secondary heat bridge 18, and realizes cooling in different temperature zones by filling different working fluids. The heat conduction is achieved by filling nitrogen to achieve heat conduction in the 80K temperature range, and by filling hydrogen to achieve heat conduction in the 20K temperature range.

The above-mentioned refrigeration method based on the controllable heat pipe of the 4K thermally coupled regenerative cryogenic refrigerator includes the following steps:

Step 1), the gas working medium is compressed by the first compressor 1 and firstly enters the first-stage regenerator 6 for pre-cooling, and then enters the first-stage pulse tube 5 through the first-stage guide tube 11, and the first-stage pulse tube 5 passes through the first-stage The gas reservoir 3 and the primary inertia tube 4 create a phase difference between the mass flow and the pressure wave of the gas working medium to enhance heat exchange. The gas working medium is compressed at the hot end of the primary pulse tube 5 to release heat, and then at the cold end Expansion and cooling, resulting in refrigeration effect, and pre-cooling the middle part of the secondary regenerator 7 and the upper half of the tertiary regenerator 8 through the primary thermal bridge 12;

Step 2), a part of the gas working medium in the second compressor 2 passes through the precooled secondary regenerator 7, the mass enthalpy flow is reduced, and then the gas working medium enters the secondary pulse tube 15 through the secondary flow guide tube 17 , the secondary pulse tube 15 generates a phase difference between the mass flow and the pressure wave of the gas working medium through the secondary gas reservoir 13 and the secondary inertia tube 14 to enhance heat exchange, and the gas working medium is at the hot end of the secondary pulse tube 15 It is compressed to release heat, and then expands and cools down at the cold end to produce a refrigeration effect, and precools the lower half of the third-stage regenerator 8 through the secondary heat bridge 18;

Step 3), after another part of the gas working fluid in the second compressor 2 passes through the precooled three-stage regenerator 8, the mass enthalpy flow is significantly reduced, thereby significantly increasing the net cooling capacity at the cold end of the three-stage pulse tube 16, reducing No-load cooling temperature.

As shown in Figure 2, the present invention also discloses another 4K thermally coupled low-frequency regenerative cryogenic refrigerator based on controllable heat pipes, including a first compressor 1, a first-stage gas storage 3, a first-stage inertia tube 4, a Level pulse tube 5, level one regenerator 6, level two regenerator 7, level one draft tube 11, level one heat bridge 12, level two gas storage 13, level two inertia tube 14, level two pulse tube 15 and Secondary draft tube 17;

Among them, the first compressor 1 is respectively connected to the inlets of the primary regenerator 6 and the secondary regenerator 7; Pipe 4 and primary gas storage 3 are connected in sequence; secondary regenerator 7, secondary diversion pipe 17, secondary vessel 15, secondary inertia tube 14, and secondary gas storage 13 are sequentially connected; primary thermal The bridge 12 respectively wraps the outlet of the primary regenerator 6 and the middle part of the secondary regenerator 7 for thermal coupling connection.

The controllable heat pipe-based 4K thermally coupled low-frequency regenerative cryogenic refrigerator adopts the controllable heat pipe as the heat conduction material of the first heat bridge 12 .

The above-mentioned 4K heat-coupled low-frequency regenerative cryogenic refrigerator refrigeration method based on controllable heat pipes includes the following steps:

Step 1), a part of the gas working medium in the first compressor 1 first enters the primary regenerator 6 for pre-cooling, and then enters the primary pulse tube 5 through the primary draft tube 11, and the primary pulse tube 5 passes through the primary The gas reservoir 3 and the primary inertia tube 4 create a phase difference between the mass flow and the pressure wave of the gas working medium to enhance heat exchange. The gas working medium is compressed at the hot end of the primary pulse tube 5 to release heat, and then at the cold end Expansion and cooling, resulting in refrigeration effect, and pre-cooling the middle part of the secondary regenerator through the primary heat bridge 12;

Step 2), another part of the gas working fluid in the first compressor 1 passes through the precooled secondary regenerator 7, and the mass enthalpy flow is significantly reduced, thereby significantly increasing the net cooling capacity at the cold end of the secondary pulse tube 15 and reducing the useless load cooling temperature.

As shown in Figure 3, the working principle of the controllable heat pipe is: the condensation section of the controllable heat pipe is connected with a gas storage chamber, which is filled with inert gas. When the heat pipe is not working, the inert gas and the working medium vapor are evenly mixed. When the heat pipe is working, the working medium vapor in the evaporating section carries the inert gas and flows to the condensing section. The working fluid vapor is condensed into liquid in the condensation section and returns to the evaporation section through the tube core. Inert gas builds up continuously at the cold end. After a period of time, all the inert gas accumulates in the gas storage chamber and condensation section, forming a gas lock. When the working temperature of the heat pipe increases, the internal vapor pressure increases, compressing the air plug, increasing the effective heat dissipation area of the condensation section, reducing the thermal resistance of the condensation section, increasing the cooling capacity, and suppressing the rise in the working temperature of the heat pipe. On the contrary, when the working temperature of the heat pipe decreases, the air plug expands, increasing the thermal resistance of the condensation section, so that the working temperature of the heat pipe does not drop any longer. In this way, the working temperature of the heat pipe can be kept within a certain range.

As shown in Figure 4, as the temperature of the hot end increases, the irreversible heat loss of the regenerator increases, especially when the pressure ratio of the cold end is 1.2 and the temperature of the hot end is greater than 20K, the irreversible heat loss of the regenerator Dramatic increase. Therefore, when copper is used as the heat bridge, the heat transfer temperature difference is large, resulting in a large irreversible heat loss of the regenerator, while the controllable heat pipe has a small heat transfer temperature difference, which can effectively reduce the irreversible heat loss of the regenerator.

As shown in Figure 5, although the thermal conductivity of copper increases with the increase of temperature, it is still small compared with the heat pipe. It can be seen from the numerical value that at the same temperature, the thermal conductivity of the heat pipe is that of copper. Thousands of times. Therefore, using a controllable heat pipe as a thermal bridge can effectively enhance the heat transfer capacity, reduce the heat transfer temperature difference between the cold and hot ends, and reduce the irreversible heat loss of the regenerator.

Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as herein Explanation.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (4)

1. A 4K thermally coupled regenerative cryogenic refrigerator based on a controllable heat pipe, characterized in that: Including the first compressor (1), the second compressor (2), the primary gas storage (3), the primary inertia tube (4), the primary pulse tube (5), the primary regenerator (6), Second-level regenerator (7), third-level regenerator (8), third-level gas storage (9), third-level inertia tube (10), first-level diversion tube (11), and first-level thermal bridge (12) , the secondary air reservoir (13), the secondary inertia tube (14), the secondary vessel (15), the tertiary vessel (16), the secondary diversion tube (17), the secondary thermal bridge (18) and Tertiary draft tube (19); Among them, the first compressor (1), the first-stage regenerator (6), the first-stage guide tube (11), the first-stage pulse tube (5), the first-stage inertia tube (4), and the first-stage gas storage (3 ) in sequence; the outlet of the second compressor (2) is connected to the inlet of the second-stage regenerator (7) and the third-stage regenerator (8); the second-stage regenerator (7), the second-stage draft tube (17), secondary pulse tube (15), secondary inertia tube (14), secondary gas storage (13) are connected in sequence; The first-level pulse tube (16), the third-level inertia tube (10), and the third-level gas storage (9) are connected in sequence; the first-level thermal bridge (12) wraps the outlet of the first-level regenerator (6), and the second-level regenerator The middle part of the heater (7) and the upper half of the third-stage regenerator (8) are thermally coupled; the second-level thermal bridge (18) wraps the outlet of the second-stage The lower half of the heater (8) is thermally coupled; Both the primary heat bridge (12) and the secondary heat bridge (18) use controllable heat pipes as heat conduction materials. 2. The refrigeration method based on the controllable heat pipe-based 4K thermally coupled regenerative cryogenic refrigerator according to claim 1, characterized in that it comprises the following steps: Step 1), the gas working medium is compressed by the first compressor (1) and first enters the first-stage regenerator (6) for pre-cooling, and then enters the first-stage pulse tube (5) through the first-stage diversion tube (11), The primary pulse tube (5) generates a phase difference between the mass flow and pressure wave of the gas working medium through the primary gas reservoir (3) and the primary inertia tube (4) to enhance heat transfer. The hot end of the tube (5) is compressed to release heat, and then expands and cools at the cold end to produce a cooling effect, and passes through the primary heat bridge (12) to the middle of the secondary regenerator (7) and the third stage regenerator (8 ) The upper part is pre-cooled; Step 2), a part of the gas working medium in the second compressor (2) passes through the precooled secondary regenerator (7), the mass enthalpy flow is reduced, and then the gas working medium passes through the secondary draft pipe (17) Entering the secondary pulse tube (15), the secondary pulse tube (15) generates a phase difference between the mass flow of the gas working medium and the pressure wave through the secondary gas reservoir (13) and the secondary inertial tube (14) to enhance the conversion Heat, the gas working fluid is compressed at the hot end of the secondary pulse tube (15) to release heat, and then expands and cools at the cold end to produce a cooling effect, and passes through the secondary heat bridge (18) to the tertiary regenerator (8) The lower half of the pre-cooling; Step 3), after another part of the gas working fluid in the second compressor (2) passes through the precooled third-stage regenerator (8), the mass enthalpy flow is significantly reduced, thereby significantly improving the cooling of the third-stage pulse tube (16). The net cooling capacity at the end, reducing the no-load cooling temperature. 3. 4K thermally coupled low-frequency regenerative cryogenic refrigerator based on controllable heat pipes, characterized in that: Including the first compressor (1), the first-level gas storage (3), the first-level inertia tube (4), the first-level pulse tube (5), the first-level regenerator (6), and the second-level regenerator (7) , first-level diversion tube (11), first-level thermal bridge (12), second-level air reservoir (13), second-level inertial tube (14), second-level pulse tube (15) and second-level draft tube (17) ; Among them, the first compressor (1) is respectively connected to the inlets of the primary regenerator (6) and the secondary regenerator (7); the primary regenerator (6), the primary draft pipe (11) , primary vessel (5), primary inertial tube (4), and primary gas storage (3) are connected sequentially; secondary regenerator (7), secondary diversion tube (17), secondary vessel (15), the secondary inertia tube (14), and the secondary gas storage (13) are connected sequentially; the primary heat bridge (12) wraps the outlet of the primary regenerator (6) and the secondary regenerator ( 7) in the middle, for thermal coupling connection; The primary heat bridge (12) uses a controllable heat pipe as a heat conducting material. 4. The refrigeration method based on the controllable heat pipe-based 4K thermally coupled low-frequency regenerative cryogenic refrigerator according to claim 3, characterized in that it comprises the following steps: Step 1), a part of the gas working medium in the first compressor (1) first enters the first-stage regenerator (6) for pre-cooling, and then enters the first-stage pulse tube (5) through the first-stage guide tube (11), The primary pulse tube (5) generates a phase difference between the mass flow and pressure wave of the gas working medium through the primary gas reservoir (3) and the primary inertia tube (4) to enhance heat transfer. The hot end of the tube (5) is compressed to release heat, and then expands and cools down at the cold end to produce a cooling effect, and pre-cools the middle of the second-stage regenerator through the first-stage heat bridge (12); Step 2), another part of the gas working fluid in the first compressor (1) passes through the precooled secondary regenerator (7), the mass enthalpy flow is significantly reduced, thereby significantly increasing the temperature of the cold end of the secondary pulse tube (15). Net cooling capacity, lower no-load cooling temperature.