Cryopump

Abstract

A pump for pumping cryogenic liquid includes a pump housing defining an elongate cylinder. The elongated piston slides within the cylinder such that an intermediate fluid chamber configured to receive an intermediate fluid is defined within the cylinder adjacent a first end of the piston and a fluid pumping chamber is defined within the cylinder adjacent a second end of the piston. The fluid pumping chamber includes an inlet and an outlet. The pump housing is located within the reservoir. The sump is configured to receive and submerge a portion of the pump housing within the cryogenic liquid and to provide the cryogenic liquid to the inlet of the pumping chamber for pumping. The reservoir jacket surrounds the reservoir so as to define a reservoir isolation space therebetween. The pump jacket surrounds the pump housing defining a pump isolation space therebetween.

Description

[0001] Priority claim

[0002] This application claims priority to U.S. Provisional Application No. 63 / 331,482, filed on April 15, 2022, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates generally to pumps for cryogenic liquids and, more particularly, to cryogenic pumps using an intermediate fluid. Background Art

[0004] Cryogenic fluids, such as liquid natural gas and hydrogen, are fluids with boiling points below -130°F / -90°C. Cryogenic fluids have many important industrial uses and are growing in importance as energy sources. With regard to the latter, the importance of hydrogen as an alternative clean energy source has increased with advances in fuel cell technology and its use in home power generation. In addition, the use of fuel cell technology, such as in fuel cell-powered vehicles, is growing.

[0005] Like other cryogenic fluids such as liquefied natural gas, hydrogen is more efficiently transported and stored in liquid form. In addition, it is desirable to store hydrogen at high density and to transport and use hydrogen at reduced volume and low cost to help build a practical hydrogen infrastructure. In addition, other cryogenic liquids are often required to be pressurized for use and transportation as well as for efficient storage. Therefore, cryogenic pumps are key components for the storage and transportation of cryogenic liquids.

[0006] There is a need for cryogenic pumps that are reliable, space-saving, and economical to construct and operate. Summary of the invention

[0007] Aspects of the present subject matter may be implemented individually or together in the devices and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to exclude the individual use of these aspects or the individual claims of these aspects or the different combinations set forth in the appended claims.

[0008] In one aspect, a pump for pumping cryogenic liquids includes a pump housing defining an elongated cylinder. An elongated piston is slidably positioned within the cylinder such that an intermediate fluid chamber receiving an intermediate fluid is defined within the cylinder adjacent to a first end of the piston, and a fluid pumping chamber is defined within the cylinder adjacent to a second end of the piston. The fluid pumping chamber includes an inlet and an outlet. The pump housing is positioned within a sump that receives a portion of the pump housing and immerses it within the cryogenic liquid and provides cryogenic liquid to an inlet of the pumping chamber for pumping. A sump jacket surrounds the sump, thereby defining a sump insulation space therebetween. A pump jacket surrounds the pump housing, thereby defining a pump insulation space therebetween. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a process flow and schematic diagram illustrating a system including an embodiment of the disclosed cryopump.

[0010] Figure 2 is a process flow and schematic diagram illustrating a system including an alternative embodiment of the cryopump of the present invention.

[0011] Figure 3 Shows the available Figure 1 and 2 An embodiment of an isolation system for a cryogenic pump of a system.

[0012] Figure 4A is a schematic diagram showing a second embodiment of the cryopump of the present invention, wherein the piston is at the top dead center position.

[0013] Figure 4B is a schematic diagram showing a second embodiment of the cryopump of the present invention, wherein the piston is at the bottom dead center position.

[0014] Figure 5 yes Figure 4A and 4B Exploded side view of the piston and pump housing.

[0015] Figure 6 yes Figure 4A-5 Exploded side view of the top and bottom of the tank and tank jacket.

[0016] Figure 7 yes Figure 4A-5 Exploded side view of the piston and pump housing and the top and bottom of the sump and sump jacket.

[0017] Figure 8 yes Figure 4A-5 Exploded perspective view of the piston and pump housing and the top and bottom of the reservoir and reservoir jacket.

[0018] Fig. 9 yes Figure 4A-8 Side view of the assembled piston and pump housing and the top and bottom of the sump and sump jacket.

[0019] Fig.10 yes Figure 4A-8 A side view of an alternative embodiment of a pump piston.

[0020] Fig.11 yes Fig.10 Side view of the piston with the top cover removed.

[0021] Fig.12 yes Fig.10 and 11 A cross-sectional view of a piston core, wherein the section passes through the length of the longitudinal axis of the piston.

[0022] Fig.13 yes Fig.10 and 11 Magnified view of the piston seal. DETAILED DESCRIPTION

[0023] It should be noted that while the embodiments shown and presented below are described in terms of pumping liquid hydrogen, the present invention may be used to pump other types of cryogenic liquids.

[0024] Figure 1 A system for pumping liquid hydrogen to high pressure is shown. By way of example only, the system may pump liquid hydrogen to about 1000 bar. The system includes a first cryopump, generally indicated at 10, and a second cryopump, generally indicated at 12. As will be described in more detail below, pumps 10 and 12 are driven by an intermediate fluid, such as propane, 1-butene, or other fluids known in the art. Although two cryopumps are shown, the system may include a single cryopump or more than two cryopumps.

[0025] Figure 1 The embodiment uses propane as an intermediate fluid to drive pumps 10 and 12. Propane can remain liquid at reasonably warm temperatures (about -14 ° F) and therefore low pressures. Liquid hydrogen is about -415 ° F. As explained in more detail below, propane can be pumped to very high pressures (1000 bar = 14500 psi) using a fracturing pump. High pressure propane drives the pistons of pumps 10 and 12, pumping liquid hydrogen to nearly 1000 bar. The use of an intermediate fluid reduces sealing problems, and the pressure differential across the seals can be kept to a minimum. As a result, hydrogen seal leakage and friction (both of which are detrimental to the overall performance of the hydrogen pump) can be reduced.

[0026] Fluids other than propane, including but not limited to 1-butene, may alternatively be used as the intermediate fluid to drive pumps 10 and 12 .

[0027] Reference Figure 1 , cryogenic pumps 10 and 12 are located in respective storage tanks 14 and 16, respectively. Storage tank 14 includes a hydrogen liquid inlet 18 through which liquid hydrogen flows into the storage tank so that the bottom of the housing 20 of pump 10 is submerged. As a result, pump 10 is kept cool by liquid hydrogen so that vapor formation within pump 10 during pumping is eliminated (or at least minimized). Storage tank 14 also includes a liquid hydrogen outlet 22 so that liquid hydrogen can be returned to the source to provide recirculation of liquid hydrogen through storage tank 14 (e.g., when the pump is idle and not in use). Storage tank 16 similarly has a pump housing 23, a hydrogen liquid inlet 24, and a hydrogen liquid outlet 26.

[0028] Pump housing 20 of pump 10 defines a cylinder 32 in which a piston 34 is slidably disposed. The piston includes an intermediate fluid or propane seal 36 and a pumping fluid or hydrogen seal 38. Pump housing 23 of pump 12 similarly defines a cylinder 42 containing a piston 44. The pistons 34 and 44 of pumps 10 and 12 are respectively located at Figure 1 The bottom dead center position shown in the middle pump 10 and Figure 1 When moving from the bottom dead center to the top dead center position, the piston of each pump moves along Figure 1 The piston of each pump moves in the upward stroke or hydrogen intake direction as shown by arrow 46, and when moving from the top dead center to the bottom dead center position, the piston of each pump moves along Figure 1 The pump 10 moves in the downstroke or hydrogen discharge direction as indicated by arrow 48 .

[0029] The piston 34 divides the cylinder 32 of the pump 10 into a pumping chamber 52 and an intermediate fluid chamber 54. Figure 1 A pump 10 (indicated by arrow 56 in the figure) is formed in the pumping chamber 52 so that during the upward stroke of the piston 34, liquid hydrogen from the storage tank 14 enters the pumping chamber. During the downward stroke of the piston 34, the liquid hydrogen in the pumping chamber 52 leaves the pumping chamber through the pump discharge line 58. By way of example only, the liquid hydrogen may leave the pump 10 through the pump discharge line 58 at a pressure of about 1000 bar to a liquid hydrogen storage tank or disposal. The pump 12 has a similar structure and function.

[0030] Continue to refer Figure 1 , an annular differential pressure ("dP") space 62 of the pump 10 is defined between the sidewalls of the piston 34, the intermediate fluid seal, the pumping fluid seal, and the inner surface of the pump housing 34. The annular dP space 62 is connected to a vent line 64 having a dP vent valve 66 controlled by a dP switch 68, which opens and closes based on the difference between the pressure within the annular dP space and the intermediate fluid pressure within the intermediate fluid pump line 72.

[0031] The pressure in the annular dP space can be controlled via a vent line 64 (eg Figure 1 dP switch 68 may be a switch that senses pressure, or may alternatively include a pressure sensor or controller that senses pressure and an independent switch that is activated based on the pressure sensed by the sensor or controller.

[0032] Figure 1The cryopumps 10 and 12 are driven by a drive system, such as an intermediate fluid loop generally indicated at 80. The intermediate fluid loop includes a cooling vessel 82 including a refrigeration coil 84. The cooling vessel 82 can be refilled with propane via line 86, and is also provided with a vent line 88 to accommodate filling with liquid propane. As is known in the art, the vent line 88 can be provided with a vent valve that automatically opens when the pressure in the cooling vessel 82 reaches a predetermined level.

[0033] Refrigeration coil 84 receives refrigerant from a refrigeration system or other source and cools the propane in cooling vessel 82. The refrigeration system and coil 84 are preferably configured to cool the propane in the cooling vessel to a temperature corresponding to a pressure lower than the pressure in hydrogen storage tank 14 (or 16).

[0034] Liquid propane from cooling vessel 82 is pumped via one or more high pressure intermediate fluid pumps 92 to cryogenic pump actuated valves 94a and 94b for pump 10 and pump actuated valves 96a and 96b for pump 12. By way of example only, high pressure pump 92 may be a frac-type pump that pumps propane to very high pressures, such as 1000 bar. Alternative high pressure pumps known in the art may alternatively be used.

[0035] The pistons 34 and 44 of the slave pumps 10 and 12 are in Figure 1 Starting from the positions shown in FIG. 1 (i.e., bottom dead center and top dead center), actuating valve 94a is closed and actuating valve 94b is opened. As a result, when piston 34 moves along its upward stroke or suction direction (relative to the Figure 1 When the piston 44 moves in the direction opposite to the direction of the arrow 48 in the middle, the liquid propane in the intermediate fluid chamber 54 is directed back to the cooling vessel 82 via the recirculation line 98 through the valve 94b. At the same time, the actuation valve 96a is opened and the actuation valve 96b is closed, so that the pressurized propane from the high pressure intermediate fluid pump 92 is supplied to the intermediate fluid chamber 102 of the cryogenic pump 12. As a result, the piston 44 moves along its downward stroke or hydrogen discharge direction (which is opposite to the direction of the arrow 48 in the middle). Figure 1 The piston 34 is driven in the opposite direction of the arrow 46 in the middle) to force / pump the liquid hydrogen in the pumping chamber 104 of the pump 12 to reach the liquid hydrogen storage or treatment through the cryogenic pump discharge line 106. When the piston 34 reaches the top dead center and the piston 44 reaches the bottom dead center, the actuating valves 94a and 96b are opened, and the actuating valves 94b and 96a are closed, so that pressurized liquid propane can be introduced from the intermediate fluid pump 92 into the intermediate fluid chamber 54 of the pump 10, and the liquid propane is driven from the intermediate fluid chamber 102 of the pump 12 to the cooling container 82 via the recirculation line 108.

[0036] The cycle of the previous paragraph is repeated so that the cryogenic pumps 10 and 12 are driven by the intermediate fluid delivered to the pumps in a cyclical manner, and the liquid hydrogen is pumped at high pressure in a cyclical fashion through the pump discharge lines 58 and 106 during the downstroke / discharge stroke of the pumps 10 and 12. As this occurs, the intermediate fluid / propane is driven back to the cooling vessel 82 through the recirculation lines 98 and 108 in a cyclical fashion during the upstroke / suction stroke of the pumps 10 and 12.

[0037] A high pressure recirculation valve 112 is also in fluid communication with the outlet of the intermediate fluid pump 92. When the piston in each of the cryogenic pumps 10 and 12 drops to / reaches bottom dead center, the high pressure recirculation valve 112 is temporarily opened to prevent system over-pressurization when the corresponding piston switches to movement in the upward stroke / intake direction. When the valve 112 is open, the propane flow from the intermediate fluid pump 92 that is not directed to the actuation valve is directed back to the cooling vessel 82 through the recirculation line 108 (although a dedicated return line may be used).

[0038] The propane stream pressure is set by actuating valves 94a, 94b, 96a and 96b and is determined by the pressure required to force the pistons of pumps 10 and 12 to reach 1000 bar hydrogen pressure to pump liquid hydrogen to storage or disposal.

[0039] Alternative drive systems known in the prior art may be used instead Figure 1 The intermediate fluid circuit 80 is configured to drive the cryopumps 10 and 12 using the intermediate fluid.

[0040] Optional proximity switches 114 and 116 may be used in conjunction with piston position rods 115 and 117 to indicate the position of pistons 34 and 44 of cryopumps 10 and 12. These switches may be used to control the rate of intermediate fluid flow and the speed of the pistons and to ensure that the pistons can bottom out in the cylinders without damage to minimize the clearance volume in the pumps.

[0041] Intermediate fluid seals 36 and 122 and pumping fluid seals 38 and 124 generally maintain annular dP space 62 of pump 10 and annular dP space 132 of pump 20 free of hydrogen and propane.

[0042] The dP switch 68 of pump 10 and the dP switch 118 of pump 12 are configured to prevent leakage of the propane intermediate fluid into the liquid hydrogen, and to prevent leakage of the liquid hydrogen into the propane intermediate fluid, and in each case to reduce the pressure differential across the intermediate fluid seals 36, 122 and the pumping fluid seals 38, 124, preferably to a minimum.

[0043] exist Figure 1In the embodiment of the present invention, the pressure setting of the dP switch 68 and 118 of each cryogenic pump 10 and 12 is slightly less than the intermediate fluid pressure (measured by the intermediate fluid pump lines 72 and 126) to prevent the intermediate fluid from leaking into the hydrogen product during the downstroke (arrow 48), where the intermediate fluid pressure must be higher than the hydrogen storage tank pressure. This pressure setting of each dP switch also prevents hydrogen from leaking into the intermediate fluid during the upstroke (arrow 46), where the hydrogen storage tank pressure must be higher than the intermediate fluid pressure.

[0044] In operation, refer to Figure 1 In the cryogenic pump 10 of FIG. 1 , the pressure of the propane must be higher than the pressure in the hydrogen reservoir during the piston downstroke performed by the pump 10 (to drive the piston 34 and pump the hydrogen). Propane may therefore leak through the intermediate fluid seal 36 into the annular dP space 62. The dP switch 68 will control the vent valve 66 so that the pressure in the annular dP space 62 is slightly less than the intermediate fluid / propane pressure, which will also be less than the pressure at which the hydrogen in the reservoir 14 and pumping chamber 52 is pumped. As a result, if the pressure in the annular dP space 62 rises to a level just below the propane pressure in the intermediate fluid chamber 54 (and line 72), the propane leaking into the annular dP space 62 will be driven out of the open dP vent valve 66, rather than through the seal 38 and into the liquid hydrogen. The propane leaving the open dP vent valve 66 can be vented or recovered for use, such as in the intermediate fluid loop 80.

[0045] In contrast, with respect to the cryogenic pump 12, during the piston upstroke performed by the pump 12, the hydrogen pressure in the pumping chamber 104 of the pump 12 will be higher than the intermediate fluid pressure in the intermediate fluid chamber 102 (and line 126). As a result, hydrogen may leak through the pumping fluid seal 124 into the annular dP space 132. As in the case of the pump 10, the dP switch 118 will control the dP vent valve 136 so that the pressure in the annular dP space 132 is slightly less than the intermediate fluid / propane pressure. As a result, if the pressure in the annular dP space 122 rises to a level just below the propane pressure in the intermediate fluid chamber 102 (and line 126), the hydrogen leaking into the annular dP space 132 will be driven out of the open dP vent valve 136, rather than through the seal 122 and into the propane intermediate fluid. The hydrogen leaving the open dP vent valve 136 can be vented or recovered for use, such as in a system that supplies hydrogen to the storage tanks 14 and 16.

[0046] Pump 10 then operates as described above for pump 12 during its upstroke phase, while pump 12 operates as described above for pump 10 during its downstroke phase, with pumps 10 and 12 cycling through the various phases as liquid hydrogen is pumped.

[0047] like Figure 2As shown, one or more optional supplemental seals 202 and 204 may be used to separate leaking intermediate fluid from leaking hydrogen between the intermediate fluid seal 236 and the pumping fluid seal 238 of the cryogenic pump 210 and the intermediate fluid seal 222 and the pumping fluid seal 224 of the pump 212. Figure 2 As shown, the supplementary seals 202 and 204 divide the annular dP spaces of the pumps 210 and 212 into intermediate fluid annular dP spaces 242 and 244 and pumped fluid dP spaces 246 and 250. Either one dP annular space of each pump 210 and 212 or both dP annular spaces of each pump may be provided with the above reference Figure 1 A dP switch and a dP ventilation valve arrangement are described.

[0048] Figure 2 2 and 3. The cryopump 210 also includes an embodiment of a dedicated dP switch and a dP valve. More specifically, as previously described, the cryopump 210 includes an intermediate fluid annular dP space 242 and a pumping fluid dP space 246. An intermediate fluid dP ventilation valve 252 is in fluid communication with the intermediate fluid annular dP space 242. The intermediate fluid dP ventilation valve 252 is controlled by an intermediate fluid dP switch 254, which opens and closes based on the difference between the pressure in the intermediate fluid annular dP space 242 and the pressure in the intermediate fluid pump line 256. The cryopump 212 has a similar arrangement.

[0049] Similarly, a pumped fluid dP vent valve 262 is in fluid communication with the pumped fluid annular dP space 246. The pumped fluid dP vent valve 262 is controlled by a pumped fluid dP switch 264, which opens and closes based on the difference between the pressure within the pumped fluid annular dP space 246 and the pressure within the intermediate fluid pump line 256. The cryogenic pump 212 has a similar arrangement.

[0050] as Figure 1 An embodiment of Figure 2 The dP switches 254 and 264 (and the corresponding dP switch of pump 212) are set slightly less than the intermediate fluid pressure (measured by intermediate fluid pump line 256) to prevent leakage of intermediate fluid into the hydrogen product during the downstroke (indicated by arrow 248 of pump 210), where the intermediate fluid pressure must be higher than the hydrogen storage pressure. This pressure setting of each dP switch also prevents hydrogen from leaking into the intermediate fluid during the upstroke (indicated by arrow 256 of pump 212), where the hydrogen storage tank pressure must be higher than the intermediate fluid pressure.

[0051] Figure 1 Cryopumps 10 and 12, or Figure 2 The cryopumps 210 and 212 may be Figure 3The insulation shown in the illustrated embodiment is shown. As shown for pump 10, a reservoir jacket 302 is formed around the reservoir 14 to provide a vacuum space 304. In addition, a pump jacket 306 is disposed around the pump housing 20 to form a vacuum space 308. The vacuum spaces 304 and 308 may be connected by a neck jacket 312. The neck jacket 312 may be used to suspend the pump jacket within the reservoir and define a vacuum space that is open relative to the vacuum spaces 304 and 308. The neck jacket 312 may also surround the structure for suspending the pump housing 20 within the reservoir and the piston position rod 115 ( Figure 1 ). Pump 12 has similar insulation.

[0052] Continue to refer Figure 3 , the intermediate portion of the wall of pump housing 20 provides a heat transfer path between the liquid propane in intermediate fluid chamber 54 (shown for pump 10) and the liquid hydrogen in pumping chamber 52 (shown for pump 12). More specifically, when intermediate fluid chamber 54 is filled with propane, as shown Figure 3 As shown in the pump 10 in FIG. 1 , the surrounding upper portion of the pump housing wall reaches a temperature corresponding to the temperature of the liquid propane. In addition, when the pumping chamber 52 is filled with liquid hydrogen, as shown in FIG. Figure 3 As shown for pump 12, the surrounding lower portion of the pump housing wall is cooled to a temperature corresponding to the temperature of the liquid hydrogen. As a result, as shown by arrows 314 and 316, heat is transferred downwardly through the middle portion of the wall of the pump housing 20 along the length of the heat transfer path shown at 318. This may cause the liquid propane in the intermediate fluid chamber 54 to freeze or condense, which may hinder the pump drive system (e.g., Figure 1 Normal operation of the intermediate fluid circuit 80).

[0053] According to another embodiment of the present invention, Figure 4A and 4B As shown, the above problems are solved or at least reduced by providing a pump generally indicated at 310 having an elongated piston generally indicated at 322 which slides within an elongated cylinder 323 defined by a pump housing 320. The piston divides the cylinder 323 into an intermediate fluid chamber 324 and a pumping chamber 326. Figure 1-3 In an embodiment, the piston is provided with a seal (in Figure 4A and 4B (not shown), the seal slidably engages the inner surface of the cylinder 323 of the pump housing 320.

[0054] As in the above-mentioned embodiment, the intermediate fluid chamber 324 is driven by a pump drive system (e.g. Figure 1 The intermediate fluid circuit 80 of the embodiment of the present invention receives and discharges the pressurized intermediate fluid through the intermediate fluid passage 319 to drive the piston 322. As in the previous embodiment, alternative pump drive systems known in the art can be used instead of Figure 1 The intermediate fluid circuit 80.

[0055] The pump housing 320 is located within a reservoir 328, which includes a liquid hydrogen inlet 332 through which liquid hydrogen flows into the reservoir. As a result, the bottom of the pump housing 320 is immersed in liquid hydrogen 333 (with hydrogen vapor 335 above) so as to be kept cool by the liquid hydrogen, thereby eliminating (or at least reducing) vapor formation within the pump 310 during pumping. The reservoir 328 also includes a liquid hydrogen outlet 334 so that the liquid hydrogen can be returned to the source to provide recirculation of liquid hydrogen through the reservoir 328 (e.g., when the pump is idle and not in use).

[0056] Piston 322 Figure 4A The top dead center position and Figure 4B As a result, when moving from the bottom dead center to the top dead center position, the piston 322 moves in the upward stroke or hydrogen intake direction, as shown. Figure 4A As shown by arrow 336 in FIG. 1 , when moving from the top dead center to the bottom dead center position, the piston 322 moves in the downward stroke or hydrogen discharge direction, as shown in FIG. Figure 4B As shown by arrow 338 in FIG.

[0057] exist Figure 4A A pumping inlet, indicated by arrow 342, is formed in the pumping chamber 326 so that liquid hydrogen from the storage tank 328 enters the pumping chamber during the upward stroke of the piston 322. During the downward stroke of the piston 322, the liquid hydrogen in the pumping chamber 326 leaves the pumping chamber through a pumping outlet, indicated by arrow 344. The pumping outlet 344 is in fluid communication with a conduit (not shown) that delivers the pumped liquid hydrogen out of the pump. By way of example only, the liquid hydrogen may leave the pump 310 through the pumping outlet 344 at a pressure of about 1000 bar to a liquid hydrogen storage tank or disposal.

[0058] A reservoir jacket 346 is formed around the reservoir 328, thereby providing a vacuum space 348. In addition, a pump jacket 352 is provided around the pump housing 320, thereby forming a vacuum space 354. Figure 4A As shown, the bottom end of the pump jacket 352 may be substantially coplanar with the bottom end of the piston 322 when the piston is in the top dead center position.

[0059] The vacuum spaces 348 and 354 may be connected by a neck sheath 356. The neck sheath 356 may be used to suspend the pump sheath within the reservoir and define a vacuum space 358 that is open relative to the vacuum spaces 348 and 354. The neck sheath 356 may also surround a structure for suspending the pump housing 320 within the reservoir 328.

[0060] like Figure 4A and 4B As shown, the piston 322 is at the top dead center position ( Figure 4A ) and bottom dead center position ( Figure 4B) along the stroke length of 357. In addition, the piston has Figure 4B The length shown in 359. Select Figure 4A and 4B The stroke length 357(I) and piston length 359(L) of the embodiment can be increased to provide greater thermal isolation via the heat transfer path length indicated at 360(P), where P = L1. By way of example only, the piston length 359(L) can be 30", while the stroke length 357(I) can be 20", giving a heat transfer path length 360(P) of ten inches according to the above equation. In the illustrated embodiment, the heat transfer path length 360(P) is preferably about 6 inches or longer. A heat transfer path length 360(P) of about 12 inches or longer would be even more beneficial.

[0061] because Figure 4A and 4B The heat transfer path length 360 provides greater thermal isolation, and the liquid propane in the intermediate fluid chamber 324 transfers less heat to the cooler liquid hydrogen in the pumping chamber 326. This reduces the possibility of condensation and / or freezing of the liquid propane.

[0062] Figure 5-9 Show Figure 4A and 4B Non-limiting examples of components and dimensions of pump 310 .

[0063] refer to Figure 5 , the piston 322 may be cylindrical with an oval end cap 362 at each end and having a longitudinal length or height 364 of 30 inches. The pump housing 320 may be tubular with a pump housing cylinder (323) longitudinal length or height 366 of about 49 inches. The diameter 368 of the cylinder 323 may be about 4 inches. Thus, the ratio of the pump housing cylinder diameter to the pump housing cylinder length is about 8%.

[0064] As shown by arrow 372, piston 322 is inserted into pump housing 320 through the open bottom of the pump housing. Next, as shown by arrow 374, bottom cover 376 is bolted or otherwise secured to the bottom of the pump housing to cover and seal the open bottom. The piston and pump housing may have alternative dimensions.

[0065] refer to Figure 6, the jacketed tanks (328 and 346) include a top portion, generally designated 382, ​​which includes the tank 328 and tank jacket 346 and the tops of the pump jacket 352 and neck jacket 356. The jacketed tank also includes a bottom portion, generally designated 384, which includes the bottoms of the tank 328 and tank jacket 346 and the liquid hydrogen inlet 332 and outlet 334. By way of non-limiting example only, the length 381 between the bottom of the pump jacket 352 and the top of the tank jacket 346 may be about 44 inches, the length 383 between the bottom of the pump jacket 352 and the top of the pump jacket may be about 36.5 inches, the inner diameter 387 of the tank 328 may be about 22 inches, the inner diameter of the pump jacket may be about 10.5 inches, and the inner diameter 391 of the liquid hydrogen inlets 332 and 334 may be about 10.5 inches. Alternative dimensions may be used in the construction of these components.

[0066] like Figure 7 and 8 As shown, the pump housing 320 is inserted through the open bottom of the pump jacket 352 and welded or otherwise fixed in place. As previously described, the piston 322 is inserted into the pump housing 320 through the open bottom of the pump housing, and the bottom cover 376 is bolted or otherwise fixed to the bottom of the pump housing 320 to cover and seal the open bottom. Fig. 9 As shown, the top 382 and bottom 384 of the jacketed tank are then secured together via flanges 386 and 388 by bolts, welding, or other fastening methods known in the art.

[0067] exist Fig.10 and 11 middle, Figure 4A-5 An alternative embodiment of the piston 322 is generally indicated at 422. The piston 422 may include a top cover 421 ( Fig.10 ) and a bottom cover 423, having a polytetrafluoroethylene (PTFE) coating on the surface between the top cover and the bottom cover, the coating being molded to provide a circumferential seal 424. Fig.11 and 12 As shown, the piston 422 may include a core 426 made of steel or another rigid material capable of withstanding low temperatures and high pressures. Fig.12 As shown, the core 426 may include a cavity 428. By way of non-limiting example only, the length or height 432 of the piston (minus the top cover) may be approximately 30 inches, the length or depth 434 of the core cavity may be approximately 25 inches, and the outer diameter 436 of the core 426 may be approximately 4 inches. Alternative dimensions may be used in the construction of the core and piston.

[0068] Fig.13 Provided is a molded Fig.10 and 11) is an enlarged view of the circumferential seal 424 in the PTFE coating. The radial width 438 of the seal may be approximately 0.25 inches.

[0069] Aspects of the present subject matter may be implemented individually or together in the methods, devices, and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the description of these aspects is not intended to exclude the individual use of these aspects or the individual claims of these aspects or the different combinations set forth in the appended claims.

[0070] While the preferred embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made thereto without departing from the spirit of the invention, the scope of which is defined by the appended claims.

Claims

1. A pump for pumping cryogenic liquid, comprising: a. The pump housing defines an elongated cylinder; b. an elongated piston slidably positioned within the cylinder such that an intermediate fluid chamber configured to receive an intermediate fluid is defined within the cylinder adjacent a first end of the piston, and a fluid pumping chamber is defined within the cylinder adjacent a second end of the piston, the fluid pumping chamber comprising an inlet and an outlet; c. a sump in which the pump housing is positioned, the sump being configured to receive a portion of the pump housing and immerse it in a cryogenic liquid and to provide cryogenic liquid to the inlet of the pumping chamber for pumping; d. a tank jacket surrounding the tank, thereby defining a tank insulation space therebetween; e. A pump jacket surrounding the pump housing to define a pump isolation space therebetween.

2. The pump according to claim 1, further comprising a drive system for cyclically providing an intermediate fluid to the intermediate fluid chamber so that the piston is actuated to pump the cryogenic liquid from the pumping chamber.

3. The pump according to claim 1, wherein The piston moves between a top dead center position and a bottom dead center position, and wherein the bottom end of the pump jacket is generally coplanar with the second end of the piston when the piston is in the top dead center position.

4. The pump according to claim 1, wherein The heat transfer path length, defined as the difference between the piston length and the stroke length of the piston between top dead center and bottom dead center positions, is about 6 inches or more.

5. The pump according to claim 4, wherein The ratio of the diameter of the pump housing cylinder to the longitudinal length of the pump housing cylinder is about 8% or less.

6. The pump according to claim 1, wherein The heat transfer path length, defined as the difference between the piston length and the piston stroke length between top dead center and bottom dead center positions, is about 12 inches or more.

7. The pump according to claim 6, wherein The ratio of the diameter of the pump housing cylinder to the longitudinal length of the pump housing cylinder is about 8% or less.

8. The pump according to claim 1, wherein The cryogenic liquid is hydrogen liquid.

9. The pump according to claim 1, wherein: The intermediate fluid is propane.

10. The pump according to claim 1, wherein The intermediate fluid is 1-butene.

11. The pump according to claim 1, wherein The piston includes a polytetrafluoroethylene coating that is molded to provide a circumferential seal.

12. The pump according to claim 11, wherein The piston includes a core with the coating disposed on the core, wherein the core includes a cavity.

13. The pump according to claim 1, wherein The pump isolation space and the tank isolation space include vacuum isolation.

14. The pump of claim 13, further comprising a neck sheath connecting the reservoir to the pump sheath so as to suspend the pump sheath within the reservoir, the neck sheath defining a vacuum space open to the pump isolation space and the reservoir isolation space.

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