A Mars surface methane liquefaction system

Abstract

A methane liquefaction system for the surface of Mars includes a methane cylinder, wherein the methane cylinder outlet is connected to the inlet of a non-insulated storage tank via a first cooler and a first compressor; the outlet of the non-insulated storage tank is connected to the outlet of a second cooler; the outlet of the first compressor is connected to the outlet of the second cooler; the outlet of the second cooler is connected via a heat exchanger, a Jiao-Tang expansion valve, and an inlet of a gas-liquid separator; the liquid outlet at the bottom of the gas-liquid separator is connected to the inlet of a liquid methane storage tank, the gas outlet at the top of the gas-liquid separator is connected to the inlet of a liquid methane storage tank after passing through a heat exchanger, a second compressor, and an insulated storage tank, the heat exchanger is connected to an expander, and the outlet of the insulated storage tank is connected to the inlet of the first compressor; the present invention utilizes solar energy during the daytime on Mars to achieve energy supply, utilizes the cold environment at night on Mars to provide the cooling capacity required for pre-cooling of methane gas liquefaction, thereby significantly reducing the energy consumption of methane liquefaction on the surface of Mars, and has the advantages of low unit liquefaction energy consumption, small radiator size requirement, and continuous operation day and night.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas liquefaction, and in particular relates to a methane liquefaction system on the surface of Mars. Background Art

[0002] Mars is humanity's preferred deep space exploration target beyond the Earth-Moon system. Utilizing in-situ Martian resources to prepare liquid methane propellant for spacecraft return can significantly reduce the cost of Mars exploration missions. This is a forward-looking technology of great significance for future Mars exploration. Therefore, the efficient preparation of liquid methane propellant on the Martian surface is of great value.

[0003] The average length of a Martian solar day is approximately 24 hours and 40 minutes, only 2.7% longer than on Earth. Therefore, a Martian day can be considered approximately equal to an Earth day. Martian daylight lasts 12 hours, followed by nighttime, which lasts 12 hours. The Martian surface temperature reaches a high of 290K during daytime, dropping to 170K during nighttime. This significant temperature difference between day and night places significant demands on the technology for in-situ production of methane propellant on the Martian surface, while also providing a unique energy resource.

[0004] Human development and utilization of in-situ Martian resources are still in their infancy, and there are few reports on the efficient production of liquid methane on the Martian surface. Some researchers have proposed using cryogenic refrigerators to provide cooling to liquefy propellant gases on the Martian surface (e.g., Hauser DM et al., 2016, "Liquefaction and storage of in-situ O2 on the surface of Mars"). However, this approach consumes significant energy and has low liquefaction efficiency. Furthermore, the equipment can only operate during the Martian daytime, and the radiator occupies a large area. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a methane liquefaction system on the surface of Mars, which realizes energy supply by utilizing solar energy during the day on Mars and uses the cold environment at night on Mars to provide the cooling capacity required for pre-cooling of methane gas liquefaction, thereby greatly reducing the energy consumption of methane liquefaction on the surface of Mars. It has the advantages of low unit liquefaction energy consumption, small radiator size requirement, and continuous operation day and night.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A methane liquefaction system on the surface of Mars, comprising a methane cylinder 1, wherein the outlet of the methane cylinder 1 is connected to the inlet of a first cooler 2, the outlet of the first cooler 2 is sequentially connected to the inlet of a first compressor 5 via a first check valve 3 and a first solenoid valve 4, the outlet of the first compressor 5 is connected to the inlet of a non-insulated storage tank 7 via a second solenoid valve 6, the outlet of the non-insulated storage tank 7 is connected to the inlet of a second cooler 9 via a third solenoid valve 8, the outlet of the first compressor 5 is connected to the outlet of the second cooler 9 via a fourth solenoid valve 10; the outlet of the second cooler 9 is connected to the inlet of a coke-soak expansion valve 15 via a third heat exchanger 14, and the outlet of the coke-soak expansion valve 15 is connected to the gas The inlet of the liquid separator 16 is connected, and the liquid pipeline arranged at the bottom of the gas-liquid separator 16 is connected to the inlet of the liquid methane storage tank 17; the gas pipeline arranged at the top of the gas-liquid separator 16 is connected to the inlet of the second compressor 18 through the third heat exchanger 14, and the outlet of the second compressor 18 is connected to the inlet of the insulated storage tank 21 through the fifth solenoid valve 19, and the outlet of the insulated storage tank 21 is connected to the pipeline between the first check valve 3 and the first solenoid valve 4 through the sixth solenoid valve 22 and the second check valve 23 in sequence. A bypass branch is set at the cold end outlet of the first heat exchanger 11, which is connected to the pipeline between the first check valve 3 and the first solenoid valve 4 through the seventh solenoid valve 24.

[0008] The outlet of the second cooler 9 passes through the first heat exchanger 11, the second heat exchanger 12, and the third heat exchanger 14 in sequence and is connected to the inlet of the coke-tang expansion valve 15; the gas pipeline arranged on the top of the gas-liquid separator 16 passes through the third heat exchanger 14, the second heat exchanger 12, and the first heat exchanger 11 in sequence and is connected to the inlet of the second compressor 18; wherein, the hot end inlet of the second heat exchanger 12 is connected to the inlet of the expander 13, and the outlet of the expander 13 is connected to the cold end inlet of the second heat exchanger 12.

[0009] The exhaust port of the liquid methane storage tank 17 is connected to the pipeline between the first check valve 3 and the first solenoid valve 4 through the eighth solenoid valve 25. The opening and closing state of the eighth solenoid valve 25 is controlled by the pressure of the liquid methane storage tank 17. When the set pressure is reached, it opens to realize the reliquefaction of the evaporated exhaust gas (BOG) in the liquid methane storage tank 17.

[0010] The inlet of the methane cylinder 1 is connected to the outlet of the Sabatier / electrochemical reactor to realize the integration of methane preparation and liquefaction on the surface of Mars; the methane cylinder 1 may store methane gas.

[0011] The non-insulated storage tank 7 is made of stainless steel or aluminum alloy, is resistant to high pressure, and can withstand a pressure higher than 3 MPa.

[0012] The insulated storage tank 21 is made of stainless steel or aluminum alloy, resistant to medium pressure, and has a pressure bearing capacity higher than 2 MPa; the surface of the insulated storage tank 21 is wrapped with an insulating layer 20, which is made of low thermal conductivity foam, such as polyurethane foam (PU), phenolic foam (PF) or polystyrene foam (PS).

[0013] The first compressor 5 is a piston compressor with an outlet pressure greater than 3 MPa; the energy of the first compressor 5 comes from the conversion of solar energy during the day on Mars; the energy of the second compressor 18 comes from the output power of the expander 13 or other power sources.

[0014] The first cooler 2 and the second cooler 9 have the same structure, including a serpentine tube 26, which is bonded to a radiation plate 27. A high-emissivity coating 28 is applied to the surface of the radiation plate 27. Methane gas flows in the serpentine tube 26, and the heat exchange form outside the serpentine tube 26 is convection heat exchange and radiation heat exchange of the Martian atmosphere.

[0015] The serpentine tube 26 is a threaded tube, and the radiation plate 27 is made of a high thermal conductivity material such as aluminum or copper.

[0016] The first cooler 2 has a high operating temperature, and the material of its high emissivity coating 28 is selected from oxidized cast iron, platinum, etc.; the second cooler 9 has a low operating temperature, and the material of its high emissivity coating 28 is selected from cuprous oxide.

[0017] The beneficial effects of the present invention are:

[0018] The methane raw gas of the present invention comes from the Sabatier / electrolysis chemical reactor, which can utilize the local environmental resources of Mars to prepare high-temperature methane gas, realize the integration of methane preparation and liquefaction on the surface of Mars, and further promote the technology of in-situ methane preparation on the surface of Mars.

[0019] The present invention utilizes the cold background resources of Mars at night to achieve pre-cooling of gaseous methane before liquefaction, thereby greatly reducing the energy consumption of methane liquefaction, significantly improving the liquefaction rate, and reducing the demand for liquefaction energy consumption, which is conducive to the efficient preparation of liquid methane propellant or reducing the scale of the system.

[0020] The present invention enables continuous methane liquefaction day and night. During Martian daylight, methane feed gas, after being pressurized by a compressor, enters the back-end liquefaction system directly, where it is cooled and liquefied by an expander and throttling device. Simultaneously, the abundant feed gas during the day can be pressurized and stored in a non-insulated storage tank 7, serving as the feed gas source for nighttime liquefaction. During the Martian night, when the chemical reactor stops supplying gas, the non-insulated storage tank 7 serves as the gas source to the liquefaction system, ensuring the continuation of the liquefaction process. The low temperature of the Martian nighttime environment is also utilized for pre-cooling before liquefaction, enabling the liquefaction system to operate continuously day and night, thereby increasing the methane liquefaction rate.

[0021] The present invention can achieve reliquefaction of evaporated exhaust gas (BOG) from the liquid methane storage tank 17. By connecting the inlet of the first compressor 5 and the exhaust port of the liquid methane storage tank 17 via a pipeline, the liquid methane can be stored without loss, the pressure of the liquid methane storage tank 17 can be maintained stable, and the storage efficiency of the liquid methane can be improved. There is no need to set up a dedicated reliquefaction system, which reduces complexity. In addition, after the exhaust gas from the liquid methane storage tank 17 merges with the high-temperature methane gas, the temperature of the high-temperature methane is reduced, which helps to reduce the energy consumption of liquefaction.

[0022] When the present invention works at night, the compressed storage of the unliquefied gas is achieved through the second compressor 18 and the insulated storage tank 21. The energy supply of the second compressor 18 comes from the expansion work of the expander 13, thereby achieving the compressed storage of the unliquefied gas and the dual recovery of energy and resources.

[0023] The present invention recovers all unliquefied methane gas in the liquefaction system and boil-off gas (BOG) in the liquid methane storage tank 17, thereby achieving zero-loss production of liquid methane on Mars, where resources are scarce.

[0024] The cooler of the present invention can comprehensively utilize radiation heat exchange and convection heat exchange, and can achieve good heat exchange effect in the low-pressure environment of Mars, which is beneficial to reducing the size and cost of the heat exchanger.

[0025] In summary, the present invention has the advantages of low unit liquefaction energy consumption, small radiator size requirement, and continuous operation day and night, and has considerable application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of Example 1 of the present invention.

[0027] Figure 2 This is a structural diagram of Example 2 of the present invention.

[0028] Figure 3 This is a structural diagram of Example 3 of the present invention.

[0029] Figure 4 It is a structural schematic diagram of the cooler of the present invention. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0031] Example 1, as Figure 1As shown, a methane liquefaction system on the surface of Mars includes a methane cylinder 1, the outlet of the methane cylinder 1 is connected to the inlet of the first cooler 2, the outlet of the first cooler 2 is connected to the inlet of the first compressor 5 through the first check valve 3 and the first solenoid valve 4 in sequence, the outlet of the first compressor 5 is connected to the inlet of the non-insulated storage tank 7 through the second solenoid valve 6, and the outlet of the non-insulated storage tank 7 is connected to the inlet of the second cooler 9 through the third solenoid valve 8; the outlet of the first compressor 5 is connected to the outlet of the second cooler 9 through the fourth solenoid valve 10; the outlet of the second cooler 9 is connected to the inlet of the coke-tang expansion valve 15 through the first heat exchanger 11, the second heat exchanger 12, and the third heat exchanger 14 in sequence, the outlet of the coke-tang expansion valve 15 is connected to the inlet of the gas-liquid separator 16, and the liquid pipeline provided at the bottom of the gas-liquid separator 16 is connected to the liquid methane The inlet of the storage tank 17 is connected; the gas pipeline arranged on the top of the gas-liquid separator 16 passes through the third heat exchanger 14, the second heat exchanger 12, the first heat exchanger 11 and is connected to the inlet of the second compressor 18 in sequence, wherein the hot end inlet of the second heat exchanger 12 is connected to the inlet of the expander 13, and the outlet of the expander 13 is connected to the cold end inlet of the second heat exchanger 12; the outlet of the second compressor 18 is connected to the inlet of the insulated storage tank 21 through the fifth solenoid valve 19, the surface of the insulated storage tank 21 is wrapped with an insulating layer 20, and the outlet of the insulated storage tank 21 passes through the sixth solenoid valve 22, the second check valve 23 and is connected to the pipeline between the first check valve 3 and the first solenoid valve 4 in sequence; a bypass branch is set at the cold end outlet of the first heat exchanger 11, which is connected to the pipeline between the first check valve 3 and the first solenoid valve 4 through the seventh solenoid valve 24.

[0032] The inlet of the methane cylinder 1 is connected to the outlet of the Sabatier / electrolysis chemical reactor to receive the high-temperature methane gas generated by the chemical reaction, thereby realizing the integration of methane preparation and liquefaction on the surface of Mars; the methane cylinder 1 can also contain stored methane gas, which directly supplies gas to the liquefaction system.

[0033] The non-insulated storage tank 7 is made of stainless steel or aluminum alloy, is resistant to high pressure, and has a pressure resistance higher than 3 MPa; the insulated storage tank 21 is made of stainless steel or aluminum alloy, is resistant to medium pressure, and has a pressure resistance higher than 2 MPa; the insulation layer 20 is made of low thermal conductivity foam, using polyurethane foam (PU), phenolic foam (PF) or polystyrene foam (PS); the insulation layer 20 wraps the entire surface of the insulated storage tank 21.

[0034] The first compressor 5 is a piston compressor with an outlet pressure greater than 3 MPa; the energy of the first compressor 5 comes from the conversion of solar energy during the day on Mars; the energy of the second compressor 18 comes from the output power of the expander 13 or other power sources.

[0035] like Figure 1As shown, in Example 1, during Martian daylight: the first solenoid valve 4, the second solenoid valve 6, and the sixth solenoid valve 22 are open, connecting the front and rear containers of each solenoid valve; the third solenoid valve 8, the fourth solenoid valve 10, the fifth solenoid valve 19, and the seventh solenoid valve 24 are closed, disconnecting the front and rear containers of each solenoid valve; the high-temperature methane gas at the outlet of the methane cylinder 1 first passes through the first cooler 2, where it is cooled to approximately ambient temperature under the influence of Martian daylight; the insulated storage tank 21 stores low-temperature methane reflux gas that has not been liquefied from the previous night. Due to the opening of the sixth solenoid valve 22, the methane gas stored in the insulated storage tank 21 enters the first compressor 5 together with the methane gas at the outlet of the first cooler 2; the provision of the first check valve 3 and the second check valve 23 allows the gas to enter the first compressor 5 smoothly, preventing gas backflow; the methane gas is converted into high-pressure methane gas by the first compressor 5 and then enters the non-insulated storage tank 7; and due to the disconnection of the third solenoid valve 8, the high-pressure methane gas at the outlet of the first compressor 5 is temporarily stored in the non-insulated storage tank 7 during Martian daylight.

[0036] After the non-insulated storage tank 7 is full, the second solenoid valve 6 is disconnected, the fourth solenoid valve 10 and the seventh solenoid valve 24 are opened, and the states of the other solenoid valves remain unchanged. The high-pressure methane gas at the outlet of the first compressor 5 passes through the branch where the fourth solenoid valve 10 is located and directly enters the first heat exchanger 11; after passing through the first heat exchanger 11, the gas is divided into two parts: one part of the gas enters the expander 13, where the temperature is reduced and work is performed externally. The expanded gas merges with the return gas and flows into the second heat exchanger 12 and the first heat exchanger 11 to pre-cool the high-pressure methane; the other part of the gas is pre-cooled after passing through the second heat exchanger 12 and the third heat exchanger 14 and enters the coke-tang expansion valve 15, where it is liquefied under the cooling effect of isenthalpic throttling. , obtaining liquid methane with a higher liquefaction rate; the liquid methane and the unliquefied gaseous methane are separated in the gas-liquid separator 16, and the liquid is transported to the liquid methane storage tank 17 as a product. The gas is drawn out from the top of the gas-liquid separator 16, first passes through the third heat exchanger 14, and provides cooling for the methane gas at the hot end, and then merges with the methane gas at the outlet of the expander 13, passes through the second heat exchanger 12 and the first heat exchanger 11, and directly enters the branch where the seventh solenoid valve 24 is located, and flows back to the inlet of the first compressor 5, completing a cycle.

[0037] During the Martian night: the third solenoid valve 8 and the fifth solenoid valve 19 are open, and the front and rear containers of each solenoid valve are connected; the first solenoid valve 3, the second solenoid valve 6, the fourth solenoid valve 10, the sixth solenoid valve 22 and the seventh solenoid valve 24 are disconnected, and the connection between the front and rear containers of each solenoid valve is disconnected. Since the first compressor 5 loses its energy supply at night, the high-pressure gas source at night comes from the methane gas pre-stored in the non-insulated storage tank 7. The high-pressure methane gas stored in the non-insulated storage tank 7 passes through the second cooler 9 and is cooled to about the night ambient temperature under the action of the Martian night, and then enters the first heat exchanger 11; after passing through the first heat exchanger 11, the gas is divided into two parts: one part of the gas enters the expander 13, where the temperature is reduced and work is performed externally. The expanded gas merges with the reflux gas and flows into the second heat exchanger 12 and the first heat exchanger 11 to pre-cool the high-pressure methane; the other part of the gas passes through the second heat exchanger 12 and the third heat exchanger 14 After pre-cooling, it enters the coke-tang expansion valve 15 and is liquefied under the cooling effect of isenthalpic throttling to obtain liquid methane with a high liquefaction rate; the liquid methane and the unliquefied gaseous methane are separated in the gas-liquid separator 16, and the liquid is transported to the liquid methane storage tank 17 as a product. The gas is drawn out from the top of the gas-liquid separator 16, first passes through the third heat exchanger 14, and provides cooling for the methane gas at the hot end, and then merges with the methane gas at the outlet of the expander 13, and enters the second heat exchanger 12 and the first heat exchanger 11 together to provide cooling; since the sixth solenoid valve 22 is disconnected, the reflux gas passes through the second compressor 18 and is temporarily stored in the insulated storage tank 21.

[0038] Example 2, reference Figure 2 On the basis of Example 1, the exhaust port of the liquid methane storage tank 17 is connected to the pipeline between the first check valve 3 and the first solenoid valve 4 through the eighth solenoid valve 25. The opening and closing state of the eighth solenoid valve 25 is controlled by the pressure of the liquid methane storage tank 17. When the set pressure is reached, it opens to achieve reliquefaction of the evaporated exhaust gas (BOG) in the liquid methane storage tank 17.

[0039] The liquid methane tank 17 is parked on the surface of Mars. Due to inevitable heat leakage, the liquid methane will slowly evaporate, causing the pressure of the liquid methane tank 17 to gradually increase. The initial state of the eighth solenoid valve 25 is closed. When the pressure of the liquid methane tank 17 rises to the set value, the eighth solenoid valve 25 opens, and the evaporated gas in the liquid methane tank 17 is sent to the first compressor 5 for recycling, thereby realizing lossless storage of liquid methane, which is conducive to maintaining the pressure stability of the liquid methane tank 17. At the same time, the exhaust gas of the liquid methane tank 17 merges with the high-temperature methane gas to reduce the temperature of the high-temperature methane.

[0040] Example 3, reference Figure 3, adopts a structure without an expander 13. On the basis of Example 1, the first heat exchanger 11, the second heat exchanger 12 and the expander 13 are omitted. The operation mode of this embodiment is basically the same as that of Example 1, but the energy supply of the second compressor 18 no longer comes from the expander, but from other power sources; when there are other power sources on the surface of Mars, the adoption of this embodiment can simplify the liquefaction system process and reduce equipment investment.

[0041] The first cooler 2 and the second cooler 9 described in Example 1, Example 2 and Example 3 have the same structure. Figure 4 As shown, the system includes a serpentine tube 26 bonded to a radiant plate 27, which is coated with a high-emissivity coating 28. Methane gas flows within the serpentine tube 26, while heat transfer occurs through convection and radiation from the Martian atmosphere. The serpentine tube 26 is a threaded tube, and the radiant plate 27 is made of a high-thermal-conductivity material such as aluminum or copper. The first cooler 2 operates at a higher temperature, and its high-emissivity coating 28 is made of materials such as oxidized cast iron or platinum. The second cooler 9 operates at a lower temperature, and its high-emissivity coating 28 is made of cuprous oxide.

Claims

1. A methane liquefaction system for the surface of Mars, comprising a methane cylinder (1), characterized in that: The outlet of the methane gas cylinder (1) is connected to the inlet of the first cooler (2), the outlet of the first cooler (2) is connected to the inlet of the first compressor (5) through the first check valve (3) and the first solenoid valve (4) in sequence, the outlet of the first compressor (5) is connected to the inlet of the non-insulated storage tank (7) through the second solenoid valve (6), the outlet of the non-insulated storage tank (7) is connected to the inlet of the second cooler (9) through the third solenoid valve (8), the outlet of the first compressor (5) is connected to the outlet of the second cooler (9) through the fourth solenoid valve (10); the outlet of the second cooler (9) is connected to the inlet of the coke-tang expansion valve (15) through the third heat exchanger (14), and the outlet of the coke-tang expansion valve (15) is connected to the inlet of the gas-liquid separator (16). The liquid pipeline provided at the bottom of the gas-liquid separator (16) is connected to the inlet of the liquid methane storage tank (17); the gas pipeline provided at the top of the gas-liquid separator (16) is connected to the inlet of the second compressor (18) through the third heat exchanger (14); the outlet of the second compressor (18) is connected to the inlet of the insulation storage tank (21) through the fifth electromagnetic valve (19); the outlet of the insulation storage tank (21) is connected to the pipeline between the first check valve (3) and the first electromagnetic valve (4) through the sixth electromagnetic valve (22) and the second check valve (23) in sequence; a bypass branch is provided at the cold end outlet of the first heat exchanger (11), and is connected to the pipeline between the first check valve (3) and the first electromagnetic valve (4) through the seventh electromagnetic valve (24).

2. The Martian surface methane liquefaction system according to claim 1, characterized in that: The outlet of the second cooler (9) passes through the first heat exchanger (11), the second heat exchanger (12), and the third heat exchanger (14) in sequence and is connected to the inlet of the coke-tang expansion valve (15); the gas pipeline arranged on the top of the gas-liquid separator (16) passes through the third heat exchanger (14), the second heat exchanger (12), the first heat exchanger (11) in sequence and is connected to the inlet of the second compressor (18); wherein, the hot end inlet of the second heat exchanger (12) is connected to the inlet of the expander (13), and the outlet of the expander (13) is connected to the cold end inlet of the second heat exchanger (12).

3. The Martian surface methane liquefaction system according to claim 2, characterized in that: The exhaust port of the liquid methane storage tank (17) is connected to the pipeline between the first check valve (3) and the first solenoid valve (4) through the eighth solenoid valve (25). The opening and closing state of the eighth solenoid valve (25) is controlled by the pressure of the liquid methane storage tank (17). When the set pressure is reached, the eighth solenoid valve (25) opens to realize the reliquefaction of the evaporated exhaust gas (BOG) in the liquid methane storage tank (17).

4. The Martian surface methane liquefaction system according to claim 1, characterized in that: The inlet of the methane cylinder (1) is connected to the outlet of the Sabatier / electrochemical reactor, realizing the integration of methane preparation and liquefaction on the surface of Mars; the methane cylinder (1) contains or stores methane gas.

5. The Martian surface methane liquefaction system according to claim 1, characterized in that: The non-insulated storage tank (7) is made of stainless steel or aluminum alloy material, is resistant to high pressure, and can withstand a pressure higher than 3 MPa.

6. The Martian surface methane liquefaction system according to claim 1, characterized in that: The insulated storage tank (21) is made of stainless steel or aluminum alloy, is resistant to medium pressure, and has a pressure bearing capacity higher than 2MPa; the surface of the insulated storage tank (21) is wrapped with an insulating layer (20), and the insulating layer (20) is composed of low thermal conductivity foam, using polyurethane foam plastic (PU), phenolic foam plastic (PF) or polystyrene foam plastic (PS).

7. The Martian surface methane liquefaction system according to claim 1, characterized in that: The first compressor (5) is a piston compressor with an outlet pressure greater than 3 MPa; the energy of the first compressor (5) comes from the conversion of solar energy during the day on Mars; the energy of the second compressor (18) comes from the output power of the expander (13) or other power sources.

8. The Martian surface methane liquefaction system according to claim 1, characterized in that: The first cooler (2) and the second cooler (9) have the same structure, including a serpentine tube (26), the serpentine tube (26) is attached to the radiation plate (27), the surface of the radiation plate (27) uses a high emissivity coating (28), methane gas flows in the serpentine tube (26), and the heat exchange form outside the serpentine tube (26) is convection heat exchange and radiation heat exchange of the Martian atmosphere.

9. The Martian surface methane liquefaction system according to claim 8, characterized in that: The serpentine tube (26) is a threaded tube, and the radiation plate (27) is made of a high thermal conductivity material such as aluminum or copper.

10. The Martian surface methane liquefaction system according to claim 8, characterized in that: The first cooler (2) has a high operating temperature, and its high emissivity coating (28) is made of oxidized cast iron or platinum; the second cooler (9) has a low operating temperature, and its high emissivity coating (28) is made of cuprous oxide.

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