Liquid methane subcooler and using method

Abstract

The invention relates to a subcooler for conveying liquid methane and a using method. The liquid methane subcooler is simple in structure, high in reliability, high in temperature and flow adjusting capacity and high in adjusting precision. The liquid methane subcooler comprises a shell and a heat exchange mechanism, the shell comprises an upper sealing head, a straight barrel and a lower sealing head, the upper sealing head is provided with a liquid methane inflow pipe, a liquid methane outflow pipe, a gas medium pressurizing pipe, a hot gas medium blow-off pipe and a gas medium discharge pipe, and an adjusting butterfly valve is installed on a pipe opening of the gas medium discharge pipe; the heat exchange mechanism comprises an inlet distribution cavity, a heat exchange pipe, an outlet collection cavity and a fixing plate, the heat exchange pipe is fixedly arranged in the heat exchange area through the fixing plate, the inlet distribution cavity is arranged at one end of the heat exchange pipe in a sealed mode, the outlet collection cavity is arranged at the other end of the heat exchange pipe in a sealed mode, and the lower end socket is provided with a liquid medium inflow pipe and a liquid medium outflow pipe; the subcooler is provided with a control system.

Description

Technical Field

[0001] The present invention relates to a subcooler, in particular to a subcooler for liquid methane transportation and a use method thereof. Background Art

[0002] Supercooling technology is considered one of the most effective means of improving the quality of cryogenic propellants and reducing the size and structural mass of launch vehicles. By supercooling liquid methane from its standard boiling point to the triple point (90.69K), its density increases by 6.89% and its saturated vapor pressure drops from 101.325 kPa to 11.705 kPa. This increased density and mass allow a limited-volume tank to hold more cryogenic propellant, improving space utilization, reducing the overall size and structural mass of the launch vehicle, and significantly improving launch vehicle efficiency. The reduction in the saturated vapor pressure of the cryogenic propellant effectively suppresses turbopump cavitation, ensuring proper engine operation. Furthermore, filling with supercooled propellant maintains a supercooled single-phase flow in the delivery pipeline, effectively preventing the formation of two-phase flow and ensuring smooth filling. This significantly reduces cryogenic propellant evaporation losses in the onboard tank and the number of automatic refills, sometimes eliminating the need for automatic refills. This significantly improves cryogenic propellant filling quality.

[0003] In the existing methane fueling system, there is a 13.69K temperature difference between conventional liquid nitrogen (77K) and the triple point of methane (90.69K). The outlet temperature of the liquid methane subcooler easily approaches the triple point of methane, which creates the risk of condensation. This condensation can cause the subcooler to clog, affecting the stable operation of the rocket. Furthermore, the existing liquid methane subcooler uses a horizontal tube bundle structure, and its heat exchange area is adjusted in a step-by-step manner. This makes it difficult to achieve dynamic, continuous, and precise adjustment of the liquid methane subcooling temperature and precise flow control, resulting in poor stability and unfavorable long-term operation. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a liquid methane subcooler and a method for using the same, which has a simple structure, high reliability, strong temperature and flow regulation capabilities, and high regulation accuracy.

[0005] The present invention provides a liquid methane supercooler, comprising a shell and a heat exchange mechanism, wherein the shell comprises an upper head, a straight tube and a lower head, wherein the upper head and the lower head are respectively connected to the upper and lower openings of the straight tube to form a closed heat exchange area, wherein the upper head is provided with a liquid methane inlet pipe, a liquid methane outflow pipe, a gas medium boosting pipe, a hot gas medium blowing pipe and a gas medium discharge pipe, wherein a boosting valve is provided on the gas medium boosting pipe, an inlet valve is provided on the hot gas medium blowing pipe, and a regulating butterfly valve is installed on the gas medium discharge pipe; wherein the heat exchange mechanism comprises an inlet distribution chamber, a heat exchange pipe, an outlet collecting chamber and a fixing plate, wherein the heat exchange pipe It is fixed in the heat exchange area by a fixed plate, the inlet distribution chamber is sealed at one end of the heat exchange tube and is connected to the heat exchange tube, the outlet collecting chamber is sealed at the other end of the heat exchange tube and is connected to the heat exchange tube, the liquid methane inlet pipe is connected to the inlet distribution chamber pipeline, and the liquid methane outflow pipe is connected to the outlet collecting chamber pipeline; the lower head is provided with a liquid medium inflow pipe and a liquid medium outflow pipe; the subcooler is equipped with a control system, the control system adjusts the shell pressure by adjusting the butterfly valve, and adjusts the heat exchange area by controlling the liquid medium level, and at the same time controls the hot gas medium flow through the inlet valve to eliminate liquid methane condensation in the subcooler.

[0006] The present invention provides a liquid methane supercooler, wherein the heat exchange tube is a U-shaped heat exchange tube.

[0007] The present invention provides a liquid methane subcooler, wherein the shell also includes a liquid level monitoring system, and the liquid level monitoring system includes: an upper tube of a liquid level gauge arranged on an upper head, and a first upper liquid valve is installed on the upper tube of the liquid level gauge; a first lower tube of a liquid level gauge arranged on a lower head, and a first lower tube of the liquid level gauge is installed on the first lower tube of the liquid level gauge; a first pressure taking tube connected between the upper tube of the liquid level gauge and the first lower tube of the liquid level gauge, and a first liquid level gauge and a first balancing valve are provided in parallel on the first pressure taking tube.

[0008] The present invention provides a liquid methane subcooler, wherein the shell further includes a pressure monitoring system, the pressure monitoring system including: a second pressure-taking pipe connected to the upper pipe of the liquid level gauge; a first pressure sensor and a first sensor valve arranged on the second pressure-taking pipe; a pressure measuring pipe connected to the second pressure-taking pipe, the pressure measuring pipe being equipped with a pressure gauge valve and a pressure gauge.

[0009] The present invention provides a liquid methane subcooler, wherein the liquid level monitoring system further includes: a second lower tube of a liquid level gauge arranged on a lower head, a second submerged valve being installed on the second lower tube of the liquid level gauge; a third pressure taking tube connected between the second pressure taking tube and the second lower tube of the liquid level gauge, a second submerged valve and a second liquid level gauge being connected in series, and a second balancing valve being connected in parallel with the second liquid level gauge being provided on the third pressure taking tube.

[0010] The present invention provides a liquid methane subcooler, wherein the pressure monitoring system further includes: a fourth pressure-taking pipe connected to the wall of the liquid methane inlet pipe, the fourth pressure-taking pipe being provided with a second sensor valve and a second pressure sensor; and a fifth pressure-taking pipe connected between the liquid methane outflow pipe and the fourth pressure-taking pipe, the fifth pressure-taking pipe being provided with a third sensor valve and a pressure differential sensor.

[0011] The present invention provides a liquid methane subcooler, wherein the shell further comprises a temperature monitoring system, and the temperature monitoring system comprises a temperature sensor arranged on the liquid methane outflow pipe.

[0012] The present invention provides a liquid methane supercooler, wherein the shell further comprises a sampling system, the sampling system comprises a sampling tube connected to the liquid methane outflow pipe, and the sampling tube is provided with a sampling valve.

[0013] The present invention provides a liquid methane supercooler, wherein the shell further includes two groups of pressure relief systems, each group of the pressure relief systems including: a first pressure relief pipe and a three-way valve arranged at the end of the first pressure relief pipe, the end of the first pressure relief pipe being connected to one port of the three-way valve; two parallel second pressure relief pipes respectively connected to the other two ports of the three-way valve; a safety valve respectively arranged on each second pressure relief pipe; the first pressure relief pipes in the two groups of pressure relief systems are respectively connected to the gas medium discharge pipe and the liquid methane outflow pipe.

[0014] A method for using a liquid methane subcooler according to the present invention comprises the following steps:

[0015] (1) Precooling the subcooler by adding liquid medium to the shell through the liquid medium inlet pipe to a preset low liquid level, keeping the first liquid upper valve, the second liquid upper valve, the first liquid lower valve, the second liquid lower valve, the first sensor valve and the pressure gauge valve open, and the first balancing valve and the second balancing valve closed;

[0016] The first liquid level gauge and the second liquid level gauge are redundant with each other. For low liquid level monitoring, the first pressure sensor monitors the shell pressure in real time and transmits the monitoring signal to the control system. The control system adjusts the opening of the butterfly valve according to the signal to control the discharge of the gas medium.

[0017] (2) Liquid methane is added through the liquid methane inlet pipe so that the liquid methane enters the subcooler at a preset flow rate; the liquid methane is evenly distributed to the U-shaped heat exchange tube in the inlet distribution chamber, and sequentially passes through the gas phase heat exchange zone and the liquid phase heat exchange zone to exchange heat with the liquid medium;

[0018] The control system automatically starts the liquid medium addition program, adding liquid medium to the heat exchange zone through the liquid medium inlet pipe. The temperature sensor monitors the liquid methane outlet temperature in real time. When the temperature reaches the target range, the addition of liquid medium is stopped.

[0019] The liquid methane inlet pressure is monitored in real time by the second pressure sensor, and the liquid methane inlet and outlet pressure difference is monitored by the pressure differential sensor to maintain the liquid methane inlet and outlet pressure difference within the target range. When the target range is exceeded, the subcooler anti-condensation operation is performed to prevent the heat exchange tube from being blocked.

[0020] (3) After the liquid methane is delivered, the control system opens the boost valve, closes the regulating butterfly valve, introduces gaseous medium into the shell through the gaseous medium boost pipe to increase the shell pressure, and discharges the liquid medium to below the low liquid level through the liquid medium outflow pipe;

[0021] After the liquid medium in the shell leaks below the low liquid level, stop adding liquid methane and the liquid methane stops flowing;

[0022] The control system opens the hot gas medium inlet valve and uses the hot gas medium to purge and replace the heat exchange structure. The replacement time is ≥15 minutes.

[0023] (4) During the replacement process, the sampling valve was opened periodically to collect gas samples from the sampling tube and analyze the methane content;

[0024] When the methane volume fraction meets the requirement of ≤0.5% for three consecutive sampling monitoring results, the replacement is considered to be completed;

[0025] Close all valves to end the subcooler usage process.

[0026] The difference between the present invention and the prior art is that the heat exchange tube of the present invention adopts a U-shaped heat exchange tube, and the shell adopts a vertical structure. The liquid level monitoring system, pressure monitoring system, temperature monitoring system, sampling system and pressure relief system on the shell monitor the shell in real time, and transmit the monitoring signal to the control system. The control system judges the operating status of the subcooler based on the received temperature, pressure, liquid level and other signals. If a deviation occurs, the control system adjusts the corresponding system to ensure the normal operation of the subcooler and meet the subcooling requirements.

[0027] The liquid methane subcooler and method of use disclosed herein have at least the following beneficial effects: The liquid methane subcooler utilizes the aforementioned novel structure to dynamically adjust the heat exchange area; a new pathway is added to rapidly address liquid methane condensation. This achieves continuous dynamic adjustment and precise control of the liquid methane subcooling temperature and flow rate, and enables long-term stable operation, laying the foundation for the construction of liquid methane subcooling and filling systems.

[0028] The present invention will be further described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a structural schematic diagram of a liquid methane subcooler according to the present invention;

[0030] Figure 2 Schematic diagram of the structure of the shell in the present invention;

[0031] Figure 3 It is a structural schematic diagram of the heat exchange mechanism in the present invention.

[0032] Reference numerals:

[0033] 01-shell; 11-upper head; 111-liquid methane inlet pipe; 1111-liquid methane blow-off pipe; 1112-liquid methane blow-off valve; 112-hot gas blow-off pipe; 1121-inlet valve; 113-liquid methane outlet pipe; 114-gas medium booster pipe; 1141-boosting valve; 115-gas medium discharge pipe; 1151-regulating butterfly valve; 116-manhole; 12-straight cylinder; 13-lower head; 131-liquid medium inlet Tube; 132-Liquid medium outflow pipe; 14-Liquid level monitoring system; 141-Liquid level gauge upper pipe; 1411-First liquid upper valve; 142-Liquid level gauge first lower pipe; 1421-First liquid lower valve; 143-First pressure taking pipe; 1431-First liquid level gauge; 1432-First balancing valve; 144-Liquid level gauge second lower pipe; 1441-Second liquid lower valve; 145-Third pressure taking pipe; 1451-Second liquid upper valve; 1452-Second Liquid level gauge; 1453-second balancing valve; 15-pressure monitoring system; 151-second pressure pipe; 1511-first pressure sensor; 1512-first sensor valve; 152-pressure measuring pipe; 1521-pressure gauge valve; 1522-pressure gauge; 153-fourth pressure pipe; 1531-second sensor valve; 1532-second pressure sensor; 154-fifth pressure pipe; 1541-differential pressure sensor; 1542-third Sensor valve; 16-temperature monitoring system; 161-temperature sensor; 17-sampling system; 171-sampling tube; 1711-sampling valve; 18-pressure relief system; 181-first pressure relief pipe; 182-three-way valve; 183-second pressure relief pipe; 184-safety valve; 02-heat exchange mechanism; 21-inlet distribution chamber; 22-heat exchange tube; 23-U-type heat exchange tube; 24-outlet collecting chamber; 25-fixed plate; 03-control system. DETAILED DESCRIPTION

[0034] like Figure 1 、 3As shown, the present invention is a liquid methane supercooler, comprising a shell 01 and a heat exchange mechanism 02, the shell 01 comprising an upper head 11, a straight cylinder 12 and a lower head 13, the upper head 11 and the lower head 13 are respectively connected to the upper and lower openings of the straight cylinder 12 to form a closed heat exchange area (the heat exchange area is the shell cavity), the upper head 11 is provided with a liquid methane inlet pipe 111, a liquid methane outflow pipe 113, a gas medium boosting pipe 114, a hot gas medium blowing pipe 112 and a gas medium discharge pipe 115, the gas medium boosting pipe 114 is provided with a boosting valve 1141, the hot gas medium blowing pipe 112 is provided with an inlet valve 1121, and the gas medium discharge pipe 115 is provided with a regulating butterfly valve 1151 on the pipe wall; the heat exchange mechanism 02 comprises an inlet distribution chamber 21, a heat exchange pipe 22, an outlet The heat exchange tubes 22 are fixed within the heat exchange zone via the inlet manifold 24 and fixed plate 25. The inlet distribution chamber 21 is sealed and connected to one end of the heat exchange tubes 22. The outlet manifold 24 is sealed and connected to the other end of the heat exchange tubes 22. The liquid methane inlet pipe 111 is connected to the inlet distribution chamber 21, and the liquid methane outflow pipe 113 is connected to the outlet manifold 24. The lower end cap 13 is provided with a liquid medium inlet pipe 131 and a liquid medium outflow pipe 132. The subcooler is equipped with a control system 03, which adjusts the shell 01 pressure by regulating the butterfly valve 1151 and the heat exchange area by controlling the liquid medium level. The inlet valve 1121 controls the hot gas medium flow rate to eliminate liquid methane condensation in the subcooler. The heat exchange tubes 22 are U-shaped heat exchange tubes 23.

[0035] At standard atmospheric pressure, methane has a boiling point of 111.7K. When the temperature drops below this value, methane liquefies; however, when the temperature drops further to below 90.69K, liquid methane may condense into a solid state (freeze). The heat exchange medium for the liquid methane subcooler of the present invention is preferably nitrogen, which has a moderate boiling point, is readily available, safe, inert, and low-cost. Because liquid methane subcooling requires controlling the temperature between 91K and 112K, the boiling point of liquid nitrogen (77K) can be adjusted by pressure (e.g., when pressurized to 0.5MPa, the boiling point rises to approximately 85K) to maintain a temperature difference of 5-20K with the liquid methane, achieving gentle, controllable cooling with high cooling efficiency.

[0036] The heat exchange tube 22 adopts a vertical U-shaped heat exchange tube 23, which can increase the heat exchange area and improve the heat exchange effect.

[0037] Liquid nitrogen flows into the heat exchange zone from the liquid medium inlet pipe 131 at the lower end of the shell 01, and gaseous nitrogen flows into the heat exchange zone from the gas medium booster pipe 114 at the upper end of the shell 01. As a result, a gas phase heat exchange zone and a liquid phase heat exchange zone are formed in the heat exchange zone. The heat exchange tube 22 is heat exchanged by gaseous nitrogen and liquid nitrogen respectively. By changing the amount of liquid nitrogen and gaseous nitrogen injected into the heat exchange zone, the continuous change of the heat exchange area between the liquid methane in the heat exchange tube 22 and the gas phase heat exchange zone and the liquid phase heat exchange zone is achieved, thereby achieving dynamic adjustment of the liquid methane subcooling temperature of 91K-112K, improving the adjustment accuracy of the subcooler and the liquid methane flow control accuracy. There is no special limitation on the material of the heat exchange tube 22 here, and any material that meets the transportation requirements can be used, such as 304 stainless steel, but the polishing process inside the heat exchange tube needs to be indicated.

[0038] This subcooler is a vertical subcooler. The lower end cap 13 is fitted with a fixed mount for stable positioning. The outer shell is formed by welding or other sealing methods to the upper end cap 11, the straight tube 12, and the lower end cap 13, forming a hollow, airtight cylindrical structure, thereby forming the heat exchange zone. The heat exchange tubes 22 are bolted or welded to the inner wall of the straight tube 12 using multiple fixing plates 25. The inlet distribution chamber 21 is sealed to the left opening of the heat exchange tubes 22 via a flange and a mating gasket. Similarly, the outlet manifold 24 is sealed to the right opening of the heat exchange tubes 22. This sealing method can also be achieved by other equally effective methods, such as welding.

[0039] Four pipe holes are left on the upper head 11, and the liquid methane inlet pipe 111, the liquid methane outflow pipe 113, the gas medium boosting pipe 114 and the gas medium discharge pipe 115 are respectively welded to the corresponding pipe holes. Similarly, the liquid medium inlet pipe 131 and the liquid medium outflow pipe 132 are respectively welded to the corresponding pipe holes of the lower head 13, wherein the liquid methane inlet pipe 111 is connected to the inlet distribution chamber 21, and the liquid methane outflow pipe 113 is connected to the outlet collecting chamber 24 to form a liquid methane delivery channel; the gas medium boosting pipe 114 and the gas medium discharge pipe 115 are connected to the heat exchange area to form a gas medium channel.

[0040] The gas medium channel has a dual function. First, during heat exchange, nitrogen is injected into the heat exchange area through the gas medium booster pipe 114. In the gas phase heat exchange area, heat is exchanged with the liquid methane in the heat exchange pipe 22. If the nitrogen pressure is too high during the heat exchange process, the control system 03 opens the regulating butterfly valve 1151 on the gas medium discharge pipe 115 to discharge the nitrogen.

[0041] Second, when the liquid methane is delivered and the subcooler needs to be shut down or return liquid, high-pressure nitrogen is injected into the heat exchange area through the gas medium booster pipe 114. The high-pressure nitrogen pushes the liquid nitrogen in the liquid phase heat exchange area to complete the liquid nitrogen return.

[0042] The liquid medium inlet pipe 131 and the liquid medium outlet pipe 132 are also connected to the heat exchange zone to form a liquid medium channel, thereby dividing the heat exchange zone into a gas phase heat exchange zone (the upper part of the heat exchange zone) and a liquid phase heat exchange zone (the lower part of the heat exchange zone). Liquid nitrogen is injected into the heat exchange zone for continuous heat exchange with the liquid methane in the heat exchange tube 22, and the nitrogen in the gas phase heat exchange zone is used to form a dynamic adjustment of liquid methane supercooling, thereby ensuring stable transportation of liquid methane without condensation.

[0043] The hot gas medium blow-off pipe 112 with an inlet valve 1121 is connected to the wall of the liquid methane inlet pipe 111 and communicates with the heat exchange area, forming a blow-off channel to prevent liquid methane condensation. This channel has an anti-condensation effect in multiple supercooling processes.

[0044] In addition, the liquid methane inlet pipe 111 is connected to a liquid methane blow-off pipe 1111, and a liquid methane blow-off valve 1112 is installed on the liquid methane blow-off pipe. The control system 03 opens the liquid methane blow-off valve 1112, blows nitrogen into the heat exchange tube 22, and heats the heat exchange tube 22 with the hot nitrogen, thereby further enhancing the anti-condensation effect of liquid methane.

[0045] First, pipe purge: During or after liquid methane delivery, residual liquid methane may remain in the heat exchange tubes 22. To prevent condensation and damage to the heat exchange tubes 22, the liquid methane must be quickly discharged. Stop the liquid methane supply, open the liquid methane purge valve 1112, and use nitrogen to discharge most of the liquid methane from the pipeline.

[0046] Second, hot nitrogen purge: After the pipeline is purged, liquid methane and possibly solid methane may remain in the heat exchange tubes 22. Open inlet valve 1121 and introduce hot nitrogen into the heat exchange zone through the hot gas purge pipe 112. The hot nitrogen heats the heat exchange tubes 22, vaporizing the liquid methane or condensed solid methane. The resulting methane gas is then discharged through the liquid methane outflow pipe 113.

[0047] Third, gas replacement: After entering the heat exchange zone through the hot gas medium purge pipe 112, the hot nitrogen dilutes and displaces the low-temperature nitrogen within the shell 01 (i.e., some of the low-temperature nitrogen is discharged through the gas medium discharge pipe 115), raising the overall temperature of the shell 01 and reducing the risk of condensation during the subsequent liquid methane cooling process. For example, after a shutdown, low-temperature nitrogen (<90K) may remain in the shell 01. The introduction of hot nitrogen can raise its temperature to above 100K, preventing the rapid cooling of the liquid methane due to the low-temperature environment during the next startup.

[0048] Fourth: In extreme cases, such as when the heat exchange tube 22 is severely blocked, the heat exchange tube 22 can be unblocked by combining liquid nitrogen backflow and hot nitrogen blowdown:

[0049] Open the boost valve 1141 and fill the heat exchange area with high-pressure nitrogen through the gas medium boost pipe 114, pressing the liquid nitrogen in the shell 01 back to the storage tank through the liquid medium outflow pipe 132 (lowering the liquid level). At the same time, the hot gas medium blow-off pipe 112 introduces hot nitrogen into the heat exchange area to heat the heat exchange tube 22 and vaporize the condensed solid methane for discharge.

[0050] The operation of the subcooler is regulated by the control system 03. The control system 03 adjusts the shell 01 pressure by adjusting the butterfly valve 1151 according to the operating status of the subcooler, adjusts the liquid methane heat exchange area by controlling the liquid medium level, and controls the high-temperature nitrogen flow through the inlet valve 1121 to prevent methane condensation. The specific control process will be described in detail later.

[0051] like Figure 2 As shown, the shell 01 also includes a liquid level monitoring system 14, which includes: an upper tube 141 of a liquid level gauge arranged on the upper head 11, and a first upper liquid valve 1411 is installed on the upper tube 141 of the liquid level gauge; a first lower tube 142 of a liquid level gauge arranged on the lower head 13, and a first lower tube 142 of the liquid level gauge is installed on the first lower tube 142 of the liquid level gauge; a first pressure taking tube 143 connected between the upper tube 141 of the liquid level gauge and the first lower tube 142 of the liquid level gauge, and a first liquid level gauge 1431 and a first balancing valve 1432 are provided in parallel on the first pressure taking tube 143.

[0052] The liquid level monitoring system 14 is used to monitor the liquid nitrogen level in the shell 01 in real time. The upper tube 141 of the liquid level gauge and the first lower tube 142 of the liquid level gauge are welded to the upper head 11 and the lower head 13 respectively and are connected to the interior of the shell 01 (i.e., the heat exchange area). The upper and lower ends of the first pressure taking tube 143 are connected to the upper tube 141 of the liquid level gauge and the first lower tube 142 of the liquid level gauge respectively, thereby forming a first liquid measuring channel.

[0053] A display panel and a valve operation panel are installed on the straight cylinder 12. When monitoring the liquid level, the first above-liquid valve 1411 and the first below-liquid valve 1421 are opened, and the first liquid level gauge 1431 monitors the liquid nitrogen injected into the shell 01 in real time. The liquid level information is intuitively displayed on the display panel and transmitted to the control system 03 in the form of a signal. The control system 03 controls the injection amount of liquid nitrogen according to the liquid level signal, and then controls the liquid nitrogen level to achieve continuous changes in the heat exchange area with the heat exchange tube 22, thereby achieving dynamic adjustment of the liquid methane subcooling and enhancing the monitoring accuracy, heat exchange efficiency and stability of the subcooler.

[0054] In addition, the first balancing valve is mainly used to balance the pressure on both sides of the first liquid level gauge 1431. The liquid level gauge display can be reset to zero through the balancing valve, which not only ensures high accuracy of liquid level monitoring, but also facilitates calibration or maintenance of the liquid level monitoring system 14.

[0055] like Figure 2As shown, the shell 01 also includes a pressure monitoring system 15, which includes: a second pressure-taking tube 151 connected to the upper tube 141 of the liquid level gauge; a first pressure sensor 1511 and a first sensor valve 1512 arranged on the second pressure-taking tube 151; a pressure measuring tube 152 connected to the second pressure-taking tube 151, and a pressure gauge valve 1521 and a pressure gauge 1522 are installed on the pressure measuring tube 152.

[0056] Pressure monitoring system 15 is used to monitor the pressure within shell 01 in real time. Second pressure-taking pipe 151 is connected to liquid level gauge upper pipe 141. The pressure within second pressure-taking pipe 151 is the same as the pressure within the heat exchange zone, thus forming a pressure measurement path. Pressure-taking pipe 152 is connected to pressure gauge 1522 and second pressure-taking pipe 151, which displays the pressure of shell 01 in real time.

[0057] When monitoring pressure, the first sensor valve 1512 and the pressure gauge valve 1521 are opened. The pressure gauge 1522 monitors the pressure changes within the housing 01 in real time. At the same time, the first pressure sensor 1511 transmits the pressure signal to the control system 03. The control system 03 controls the pressure of the housing 01 by adjusting the regulating butterfly valve 1151 according to the pressure signal. When the pressure within the housing 01 is too high, the control system 03 increases the opening of the regulating butterfly valve 1151, allowing the nitrogen in the housing 01 to be discharged outward through the gas medium discharge pipe 115 until the pressure within the housing 01 reaches the standard. The control system 03 then closes the regulating butterfly valve 1151. When the pressure within the housing 01 is too low, the control system 03 opens the boost valve 1141 and injects nitrogen into the housing 01 through the gas medium boost pipe 114 to increase the pressure until the pressure reaches the standard.

[0058] In addition, a manhole 116 is provided on the upper head 11 for workers to enter and exit, so as to facilitate the overhaul and maintenance of the subcooler or the replacement of internal parts.

[0059] The liquid level monitoring system 14 and the pressure monitoring system 15 share the liquid level gauge upper pipe 141 , which reduces the number of pipes to be laid out and thus improves space utilization.

[0060] It should be noted that, as a whole, the liquid level monitoring system 14 and the pressure monitoring system 15 cooperate with each other during operation, and the liquid methane in the heat exchange tube 22 can be efficiently supercooled by nitrogen and liquid nitrogen in the gas phase heat exchange zone and the liquid phase heat exchange zone, and the liquid nitrogen in the shell 01 can be discharged by nitrogen pressurization, thereby realizing efficient circulation of the subcooler and enhancing its adjustment ability and stability.

[0061] like Figure 2As shown, the liquid level monitoring system 14 also includes: a second lower tube 144 of the liquid level gauge arranged on the lower head 13, and a second submerged valve 1441 is installed on the second lower tube 144 of the liquid level gauge; a third pressure taking tube 145 connected between the second pressure taking tube 151 and the second lower tube 144 of the liquid level gauge, and a second above-liquid valve 1451 and a second liquid level gauge 1452 connected in series are provided on the third pressure taking tube 145, and a second balancing valve 1453 is connected in parallel with the second liquid level gauge 1452.

[0062] The second lower tube 144 of the liquid level gauge is welded to the outer surface of the lower head 13 and is connected to the interior of the shell 01. The upper and lower ends of the third pressure taking tube 145 are respectively connected to the second pressure taking tube 151 and the second lower tube 144 of the liquid level gauge, forming a second liquid measuring channel for monitoring the liquid nitrogen level.

[0063] Liquid level measurement is the core link in controlling the liquid nitrogen level in the subcooler, which directly affects the heat exchange area and shell 01 pressure regulation. If only a single liquid level gauge is used, once problems such as liquid level gauge failure, pressure pipe blockage, valve jamming or signal transmission interruption occur, the liquid nitrogen level in the heat exchange area cannot be known, resulting in the inability to accurately control the flow of liquid methane, and even causing liquid methane freezing to damage the subcooler. Therefore, the liquid level monitoring system 14 of the subcooler adopts a redundant design of the second liquid level gauge 1452 and the first liquid level gauge 1431. This design has many advantages: First, when one liquid measuring path fails, the other can still independently provide accurate liquid level data to maintain the normal operation of the system; Second, the two liquid measuring paths operate independently of each other, and the control system 03 can cross-verify the measurement data of the two liquid level gauges, take the average value as the liquid level data, and improve the accuracy of liquid level monitoring; Third, if the liquid measuring channel needs to be inspected or maintained, the corresponding valve (such as the first submersible valve 1421 and the first balancing valve 1432) can be closed to isolate the liquid measuring channel, and the other liquid measuring channel can still work normally, ensuring that the subcooler does not need to be shut down, which not only improves work efficiency but also reduces long-term operation risks.

[0064] The upper and lower ends of the first liquid measuring channel are respectively connected to the upper head 11 and the lower head 13 of the shell 01. In this way, a communicating vessel is formed between the shell 01 and the first liquid measuring channel. That is, the shell 01 and the liquid nitrogen level in the first liquid measuring channel are at the same height. The first liquid level gauge 1431 can measure the liquid nitrogen level in the first liquid measuring channel, that is, the liquid nitrogen level in the shell 01.

[0065] The second liquid measuring channel has the same working principle as the first liquid measuring channel. When working, the second liquid upper valve 1451 and the second liquid lower valve 1441 are opened, and the second liquid level gauge 1452 monitors the liquid nitrogen injected into the shell 01 in real time. The liquid level information is displayed on the display panel. At the same time, the liquid level sensor in the second liquid level gauge 1452 transmits the liquid level signal to the control system 03. The control system 03 cross-compares the liquid level data of the two liquid level gauges. If the deviation between the two liquid level data is small (such as less than 5%), the average value is taken as the basis for liquid level control, and then the injection amount of liquid nitrogen is controlled to achieve dynamic adjustment of liquid methane subcooling; if the deviation between the two liquid level data is large, the control system 03 triggers an alarm to prompt maintenance, and the worker can resume operation after the inspection is completed.

[0066] like Figure 2 As shown, the pressure monitoring system 15 also includes: a fourth pressure-taking pipe 153 connected to the wall of the liquid methane inlet pipe 111, and a second sensor valve 1531 and a second pressure sensor 1532 are provided on the fourth pressure-taking pipe 153; a fifth pressure-taking pipe 154 connected between the liquid methane outflow pipe 113 and the fourth pressure-taking pipe 153, and a third sensor valve 1542 and a differential pressure sensor 1541 are provided on the fifth pressure-taking pipe 154.

[0067] The liquid methane pressure measurement channel in the pressure monitoring system 15 is mainly used to monitor the liquid methane inlet pressure and the pressure difference between the liquid methane inlet and outlet. The specific settings are as follows:

[0068] The left end of the fourth pressure-taking pipe 153 is connected to the liquid methane inflow pipe 111 , and the right end thereof is provided with a second pressure sensor 1532 , which monitors the inlet pressure of the liquid methane in real time. The left end of the fifth pressure-taking pipe 154 is connected to the fourth pressure-taking pipe 153, and the right end is connected to the liquid methane outflow pipe 113. The pressure difference between the liquid methane inlet and outlet is monitored in real time by the pressure difference sensor 1541. This arrangement has two advantages. First, it is used to monitor the flow and blockage of liquid methane: by monitoring the pressure difference between the liquid methane inlet and outlet, it is indirectly judged whether the liquid methane flow meets the standard. If the pressure difference increases abnormally, the heat exchange tube 22 may be blocked. At this time, the control system 03 can issue an early warning and take appropriate measures. For example, when the pressure difference exceeds the normal range, the system automatically starts the alarm program to remind workers to pay attention and take corresponding measures, such as checking whether there is foreign matter blocking the heat exchange tube 22. If liquid methane condenses in the heat exchange tube 22, the control system 03 opens the inlet valve 1121 to inject hot nitrogen into the shell 01 to heat the heat exchange tube 22, and at the same time discharges part of the liquid nitrogen to lower the liquid nitrogen level until the liquid methane flow returns to normal.

[0069] Second, to ensure heat exchange efficiency: Control System 03 adjusts the liquid nitrogen level and shell 01 pressure based on data such as the liquid nitrogen level, shell 01 pressure, and the liquid methane inlet and outlet pressure differential to maintain a reasonable heat exchange area and ensure a stable liquid methane flow, thereby ensuring the effectiveness and stability of liquid methane subcooling. For example, when the pressure differential is stable, it indicates that the medium flow and heat exchange process are in a stable state. When the pressure differential suddenly changes, Control System 03 makes corresponding adjustments. For example, if the pressure differential suddenly decreases, indicating a decrease in heat exchange efficiency, Control System 03 will automatically increase the liquid nitrogen level to improve the cooling effect and maintain normal heat exchange efficiency.

[0070] During monitoring, it is only necessary to open the second sensor valve 1531 and the third sensor valve 1542. The second pressure sensor 1532 and the differential pressure sensor will transmit the monitoring signal to the control system 03. The control system 03 will adjust the liquid nitrogen level and the shell 01 pressure according to the received pressure signal, and dynamically adjust the heat exchange area of ​​the heat exchange tube 22, thereby controlling the flow of liquid methane and ensuring stable operation of the subcooler.

[0071] like Figure 2 As shown, the housing 01 further includes a temperature monitoring system 16 , which includes a temperature sensor 161 disposed on the liquid methane outflow pipe 113 .

[0072] Temperature monitoring system 16 is primarily used to monitor the outlet temperature of liquid methane in real time. Temperature sensor 161 can be mounted directly on liquid methane outlet pipe 113 or connected to it via a pipe. During monitoring, temperature sensor 161 transmits a temperature signal to control system 03, which is then linked to the aforementioned parameters, such as pressure and liquid level, to determine whether the subcooling effect meets the required standards.

[0073] If the liquid methane outlet temperature is too high, indicating insufficient supercooling, the control system 03 will increase the liquid nitrogen injection to increase the heat exchange area with the heat exchange tube 22; if the temperature is too low, it may trigger liquid nitrogen level adjustment and hot nitrogen blow-off protection to prevent liquid methane condensation and blockage of the pipeline, thereby ensuring stable operation of the subcooler.

[0074] like Figure 2 As shown, the housing 01 further includes a sampling system 17 . The sampling system 17 includes a sampling tube 171 connected to the liquid methane outflow pipe 113 . A sampling valve 1711 is provided on the sampling tube 171 .

[0075] The sampling system 17 is mainly used for monitoring the removal of liquid methane before the subcooler is shut down. When the liquid methane is delivered, the residual liquid methane in the heat exchange tube 22 needs to be removed before the subcooler is shut down to prevent condensation and damage to the heat exchange tube 22. The specific operation is as follows:

[0076] First, control system 03 opens boost valve 1141 to inject high-pressure nitrogen into shell 01, thereby increasing the pressure of shell 01. During this process, the liquid nitrogen in shell 01 will flow back through liquid medium outflow pipe 132 and be discharged. After this step is completed, boost valve 1141 is closed. Next, liquid methane purge valve 1112 is opened to displace the remaining liquid methane in heat exchange tube 22. Simultaneously, inlet valve 1121 is opened to inject hot nitrogen into shell 01 to purge and reheat heat exchange tube 22. During this process, sampling valve 1711 is periodically opened to collect gas samples from sampling tube 171 to monitor the methane content. When the monitoring results of three consecutive samplings meet the methane volume fraction requirement of ≤0.5%, the replacement is complete, all valves are closed, and the subcooler switch is turned off to stop operation.

[0077] like Figure 2 As shown, the shell 01 also includes two sets of pressure relief systems 18, each set of pressure relief systems 18 includes: a first pressure relief pipe 181 and a three-way valve 182 arranged at the end of the first pressure relief pipe 181, the end of the first pressure relief pipe 181 is connected to one port of the three-way valve 182; two parallel second pressure relief pipes 183 connected to the other two ports of the three-way valve 182 respectively; a safety valve 184 is respectively arranged on each second pressure relief pipe 183; the first pressure relief pipes 181 in the two sets of pressure relief systems 18 are respectively connected to the gas medium discharge pipe 115 and the liquid methane outflow pipe 113.

[0078] The main function of the pressure relief system 18 is to quickly exhaust and release pressure to the outside when the shell 01 is over-pressured, so that the pressure of the shell 01 quickly returns to normal. This not only improves the regulation efficiency, but also effectively prevents the shell 01 from being damaged due to excessive pressure.

[0079] In the subcooler's operating scenario, if the pressure relief system 18 is a single-group setup, when the pressure during subcooler operation is severely over-pressurized, once the safety valve 184 of the pressure relief system 18 is clogged or damaged, the nitrogen in the shell 01 will not be discharged in time, resulting in damage to the shell 01 due to prolonged exposure to high pressure. Therefore, this subcooler adopts a redundant design with two sets of pressure relief systems 18, one connected to the gas medium discharge pipe 115, and the other connected to the liquid methane outflow pipe 113. This setting can, on the one hand, enhance the pressure relief efficiency; on the other hand, it can effectively avoid the situation where the pressure relief is not timely and the shell 01 is damaged due to damage to one of the pressure relief systems 18, thereby improving the pressure relief fault tolerance of the subcooler.

[0080] When the control system 03 detects that the shell 01 is overpressured, it first opens the regulating butterfly valve 1151 to release the pressure outward; if the pressure of the shell 01 further increases to a serious overpressure state, the four safety valves 184 of the two sets of pressure relief systems 18 are opened. At this time, the nitrogen in the shell 01 is quickly released outward through the first pressure relief pipe 181, the three-way valve 182 and the second pressure relief pipe 183 until the pressure returns to normal, and then the safety valve 184 and the regulating butterfly valve 1151 are closed. The control system 03 adjusts the subcooler to a normal subcooling state based on parameters such as air pressure, liquid level and temperature at this time to ensure its safe and stable operation.

[0081] A method for using a liquid methane subcooler according to the present invention comprises the following steps:

[0082] (1) Liquid medium is added to the shell 01 through the liquid medium inlet pipe 131 to a preset low liquid level to pre-cool the subcooler, and the first upper liquid valve 1411, the second upper liquid valve 1451, the first submersible valve 1421, the second submersible valve 1441, the first sensor valve 1512 and the pressure gauge valve 1521 are kept open, and the first balancing valve 1432 and the second balancing valve 1453 are closed;

[0083] The first liquid level gauge 1431 and the second liquid level gauge 1452 are redundant and monitor the low liquid level. The first pressure sensor 1511 monitors the pressure of the shell 01 in real time and transmits the monitoring signal to the control system 03. The control system 03 adjusts the opening of the butterfly valve 1151 according to the signal to control the gas nitrogen emission.

[0084] (2) Liquid methane is added through the liquid methane inlet pipe 111, so that the liquid methane enters the subcooler at a preset flow rate; the liquid methane is evenly distributed in the inlet distribution chamber 21 to the U-shaped heat exchange tube 22, and sequentially passes through the gas phase heat exchange zone and the liquid phase heat exchange zone to exchange heat with liquid nitrogen;

[0085] The control system 03 automatically starts the liquid replenishment program, adding liquid nitrogen to the heat exchange zone through the liquid nitrogen inlet pipe 131. The temperature sensor 161 monitors the liquid methane outlet temperature in real time. When the temperature reaches the target range, the addition of liquid nitrogen is stopped.

[0086] The liquid methane inlet pressure is monitored in real time by the second pressure sensor 1532, and the liquid methane inlet and outlet pressure difference is monitored by the pressure differential sensor 1541, so that the liquid methane inlet and outlet pressure difference is maintained within the target range. When the target range is exceeded, the subcooler anti-condensation operation is performed to prevent the heat exchange tube 22 from being blocked by differential pressure monitoring.

[0087] (3) After the liquid methane is delivered, the control system 03 opens the boost valve 1141, closes the regulating butterfly valve 1151, introduces gaseous nitrogen into the shell 01 through the gas nitrogen boost pipe 114 to increase the shell pressure, and discharges the liquid nitrogen to below the low liquid level through the liquid nitrogen outflow pipe 132;

[0088] After the liquid nitrogen in shell 01 leaks below the low liquid level, the addition of liquid methane is stopped and the liquid methane stops flowing;

[0089] The control system 03 opens the liquid methane purge valve 1112 to replace the remaining liquid methane in the heat exchange tube 22. At the same time, it opens the hot nitrogen inlet valve 1121 to purge and replace the heat exchange structure with hot nitrogen. The replacement time is ≥15 minutes.

[0090] (4) During the replacement process, the sampling valve 1711 is opened periodically to collect gas samples from the sampling tube 171 and analyze the methane content;

[0091] When the methane volume fraction meets the requirement of ≤0.5% for three consecutive sampling monitoring results, the replacement is considered to be completed;

[0092] Close all valves to end the subcooler usage process.

[0093] It should be noted that the directions or positional relationships indicated by terms such as "center", "up", "down", "front", "back", "left", "right", and "middle" are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0094] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0095] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A liquid methane subcooler, characterized in that: It includes a shell and a heat exchange mechanism, the shell includes an upper head, a straight cylinder and a lower head, the upper head and the lower head are respectively connected to the upper and lower openings of the straight cylinder to form a closed heat exchange area, the upper head is provided with a liquid methane inlet pipe, a liquid methane outflow pipe, a gas medium boosting pipe, a hot gas medium blowing pipe and a gas medium discharge pipe, the gas medium boosting pipe is provided with a boosting valve, the hot gas medium blowing pipe is provided with an inlet valve, and the gas medium discharge pipe is installed with a regulating butterfly valve; the heat exchange mechanism includes an inlet distribution chamber, a heat exchange pipe, an outlet collecting chamber and a fixing plate, the heat exchange pipe is fixed by the fixing plate It is arranged in the heat exchange area, the inlet distribution chamber seal is arranged at one end of the heat exchange tube and is connected to the heat exchange tube, the outlet collecting chamber seal is arranged at the other end of the heat exchange tube and is connected to the heat exchange tube, the liquid methane inlet pipe is connected to the inlet distribution chamber pipeline, and the liquid methane outflow pipe is connected to the outlet collecting chamber pipeline; the lower head is provided with a liquid medium inflow pipe and a liquid medium outflow pipe; the subcooler is equipped with a control system, the control system adjusts the shell pressure by adjusting the butterfly valve, and adjusts the heat exchange area by controlling the liquid medium level, and at the same time controls the hot gas medium flow through the inlet valve to eliminate liquid methane condensation in the subcooler.

2. A liquid methane subcooler according to claim 1, characterized in that: The heat exchange tube is a U-shaped heat exchange tube.

3. The liquid methane subcooler according to claim 2, characterized in that: The shell also includes a liquid level monitoring system, which includes: an upper tube of a liquid level gauge arranged on the upper head, on which a first upper liquid valve is installed; a first lower tube of a liquid level gauge arranged on the lower head, on which a first lower liquid valve is installed; a first pressure taking tube connected between the upper tube of the liquid level gauge and the first lower tube of the liquid level gauge, on which a first liquid level gauge and a first balancing valve are connected in parallel.

4. The liquid methane subcooler according to claim 1, characterized in that: The shell also includes a pressure monitoring system, which includes: a second pressure-taking pipe connected to the upper pipe of the liquid level gauge; a first pressure sensor and a first sensor valve arranged on the second pressure-taking pipe; a pressure measuring pipe connected to the second pressure-taking pipe, and a pressure gauge valve and a pressure gauge installed on the pressure measuring pipe.

5. The liquid methane subcooler according to claim 4, characterized in that: The liquid level monitoring system also includes: a second lower tube of the liquid level gauge arranged on the lower head, and a second submersible valve is installed on the second lower tube of the liquid level gauge; a third pressure taking tube connected between the second pressure taking tube and the second lower tube of the liquid level gauge, and a second upper liquid valve and a second liquid level gauge are provided in series on the third pressure taking tube, and a second balancing valve is connected in parallel with the second liquid level gauge.

6. The liquid methane subcooler according to claim 4, characterized in that: The pressure monitoring system also includes: a fourth pressure-taking pipe connected to the wall of the liquid methane inlet pipe, on which a second sensor valve and a second pressure sensor are provided; and a fifth pressure-taking pipe connected between the liquid methane outflow pipe and the fourth pressure-taking pipe, on which a third sensor valve and a differential pressure sensor are provided.

7. The liquid methane subcooler according to claim 1, characterized in that: The shell further includes a temperature monitoring system, and the temperature monitoring system includes a temperature sensor arranged on the liquid methane outflow pipe.

8. The liquid methane subcooler according to claim 1, characterized in that: The housing further comprises a sampling system, wherein the sampling system comprises a sampling tube connected to the liquid methane outflow pipe, and a sampling valve is provided on the sampling tube.

9. The liquid methane subcooler according to claim 1, characterized in that: The shell also includes two sets of pressure relief systems, each of which includes: a first pressure relief pipe and a three-way valve arranged at the end of the first pressure relief pipe, the end of the first pressure relief pipe is connected to one port of the three-way valve; two parallel second pressure relief pipes respectively connected to the other two ports of the three-way valve; a safety valve respectively arranged on each second pressure relief pipe; the first pressure relief pipes in the two sets of pressure relief systems are respectively connected to the gas medium discharge pipe and the liquid methane outflow pipe.

10. A method for using the liquid methane subcooler according to any one of claims 1 to 9, characterized in that The following steps are involved: (1) Precooling the subcooler by adding liquid medium to the shell through the liquid medium inlet pipe to a preset low liquid level, keeping the first liquid upper valve, the second liquid upper valve, the first liquid lower valve, the second liquid lower valve, the first sensor valve and the pressure gauge valve open, and the first balancing valve and the second balancing valve closed; The first liquid level gauge and the second liquid level gauge are redundant with each other. For low liquid level monitoring, the first pressure sensor monitors the shell pressure in real time and transmits the monitoring signal to the control system. The control system adjusts the opening of the butterfly valve according to the signal to control the discharge of the gas medium. (2) Liquid methane is added through the liquid methane inlet pipe so that the liquid methane enters the subcooler at a preset flow rate; the liquid methane is evenly distributed to the U-shaped heat exchange tube in the inlet distribution chamber, and sequentially passes through the gas phase heat exchange zone and the liquid phase heat exchange zone to exchange heat with the liquid medium; The control system automatically starts the liquid medium addition program, adding liquid medium to the heat exchange zone through the liquid medium inlet pipe. The temperature sensor monitors the liquid methane outlet temperature in real time. When the temperature reaches the target range, the addition of liquid medium is stopped. The liquid methane inlet pressure is monitored in real time by the second pressure sensor, and the liquid methane inlet and outlet pressure difference is monitored by the pressure differential sensor to maintain the liquid methane inlet and outlet pressure difference within the target range. When the target range is exceeded, the subcooler anti-condensation operation is performed to prevent the heat exchange tube from being blocked. (3) After the liquid methane is delivered, the control system opens the boost valve, closes the regulating butterfly valve, introduces gaseous medium into the shell through the gaseous medium boost pipe to increase the shell pressure, and discharges the liquid medium to below the low liquid level through the liquid medium outflow pipe; After the liquid medium in the shell leaks below the low liquid level, the addition of liquid methane is stopped and the liquid methane stops flowing; The control system opens the hot gas medium inlet valve and uses the hot gas medium to purge and replace the heat exchange structure. The replacement time is ≥15 minutes. (4) During the replacement process, the sampling valve was opened periodically to collect gas samples from the sampling tube and analyze the methane content; When the methane volume fraction meets the requirement of ≤0.5% for three consecutive sampling monitoring results, the replacement is considered to be completed; Close all valves to end the subcooler usage process.

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