A passive phase change cooling system coupled with expansion cold energy of a hydrogen fuel cell air compressor

Abstract

This invention discloses a passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling, comprising a centrifugal air compressor, a flow-through wall, a spiral flow-through pipe, a centrifugal pump, a vacuum pump, a water tank, and a pipeline pressure regulating box. The centrifugal air compressor includes a motor, a compression-end impeller, an expansion-end impeller, a diffuser, a volute, and an air-bearing bearing. The capillary heat pipe cooling system includes an evaporation section of the spiral flow-through pipe, insulated pipes, a cold energy airflow heat exchanger at the expansion end, and a capillary wick. The working space of the heat pipe cooling system is located in the gap between the outer wall of the air compressor, the internal chamber, and the spiral flow-through pipe. The cooling system uses water as a medium, offering advantages such as high efficiency, energy saving, and low cost to assist the reliable operation of the on-board fuel cell. Furthermore, the cooling system features adaptive liquid filling, pipeline anomaly protection, and uses a ring-type double capillary layer cold fluid pipe to enhance heat exchange efficiency. The cooling system requires no external power drive, adapts to the continuous high-load operation requirements of the air compressor, and ensures the long-term reliability of the fuel cell.

Description

Technical Field

[0001] This invention relates to the field of thermal management and fluid machinery technology for hydrogen fuel cells, specifically to a passive phase change cooling system for coupling expansion and cold energy in a hydrogen fuel cell air compressor. This system integrates a distributed capillary heat pipe loop with a residual heat exchange structure at the expansion end, achieving distributed, efficient self-circulating cooling of the air compressor housing, motor, and flow piping, as well as passive recovery and utilization of cold energy at the expansion end, all without requiring any additional auxiliary power. Background Technology

[0002] Centrifugal air compressors, as fluid machines that convert mechanical energy into pressure energy by performing work on gas through a high-speed rotating impeller, are widely used in hydrogen fuel cell gas supply systems, gas circulation, and energy recovery. In hydrogen fuel cell systems, the air compressor needs to operate under high pressure ratio and high speed conditions. The frictional heat between the compressed gas and the high-speed rotor, as well as the Joule heat generated by the motor windings, cause continuous heat accumulation inside the air compressor. If this heat buildup cannot be efficiently dissipated, it will have the following serious and destructive consequences: First, high heat will reduce air density and decrease the intake mass flow rate, directly affecting the volumetric efficiency of the air compressor. Second, when the high-temperature airflow enters the fuel cell stack, it will disrupt the stack's thermal balance, causing proton exchange membrane (PEM) dehydration and membrane structure shrinkage, leading to increased membrane ohmic resistance and decreased output voltage, and in severe cases, even irreversible membrane failure. In addition, the air compressor's own components also face severe thermal damage. The motor windings are prone to insulation aging, insulation layer breakdown, and permanent magnet demagnetization at high temperatures, while the casing will experience impeller dynamic-static clearance failure due to inconsistent thermal expansion, leading to structural damage such as rotor rubbing and collision.

[0003] Currently, for heat dissipation of centrifugal air compressors used in high-power hydrogen fuel cells, the industry generally adopts an active liquid cooling solution based on water circulation. This solution typically involves creating a complex spiral or reciprocating cooling water jacket on the outer casing of the air compressor motor stator. The air compressor is then connected to the low-temperature heat dissipation circulation loop of the entire fuel cell stack via external piping. Its working logic is to use an externally equipped electric water pump as a power source to force deionized water or ethylene glycol cooling medium to flow across the motor's heated surfaces, removing electromagnetic loss heat and mechanical friction heat generated during motor operation through sensible heat exchange. However, in actual operation, this solution has revealed significant drawbacks. The obvious limitations are, firstly, the efficiency loss due to parasitic power consumption: the electric water pump and its associated cooling fan consume valuable electrical energy from the fuel cell stack. Under full operating conditions, this additional power consumption often offsets 15%–30% of the energy recovered by the expander, resulting in a lower-than-expected net system gain. Secondly, system complexity and reliability are mutually constrained: due to the extremely high speed of the centrifugal air compressor, the sealing requirements of the liquid cooling jacket are stringent. Long-term vibration conditions can easily lead to coolant leakage into the motor, causing insulation breakdown or short circuits. Furthermore, the liquid cooling solution relies on ambient air for terminal heat exchange, which is problematic in high-temperature summers or high-altitude environments. When the temperature difference between the cooling medium and the environment narrows, the heat dissipation capacity decreases drastically, making it difficult to maintain the continuous and stable operation of the air compressor under high loads. Furthermore, the large volume of piping and water tanks severely limits the integration level of the fuel cell powertrain. Another common heat dissipation method is forced convection air cooling, especially in compact or low-to-medium power air compressors. This technology typically involves adding a cooling impeller (fan) to the end of the air compressor shaft, or drawing a portion of high-pressure air from the compressor volute outlet as a cooling air source, and directing it through jet nozzles or guide channels to the motor bearings, stator windings, and the downstream power controller. Cooling is achieved through the convective heat transfer of high-speed airflow. This method attempts to solve the thermal management problem by utilizing the rotational or aerodynamic energy of the air compressor itself, avoiding the introduction of a complex liquid cooling system. However, in-depth patent comparison analysis reveals that this solution has significant technical flaws. First, the adaptability of the cooling energy level is extremely poor: forced air cooling utilizes ambient air or heated air compressed by the compressor. The heat exchange temperature difference is small, and the specific heat capacity of the air is low. When the heat generation power per unit volume of the motor is extremely high, a significant "heat accumulation" effect often occurs, leading to excessive temperature rise at the center of the motor and the risk of demagnetization of the permanent magnet.

[0004] Therefore, it is necessary to improve the cooling system of the current energy recovery fuel cell centrifugal air compressor to solve the problems existing in the above solution. Summary of the Invention

[0005] To address the aforementioned technical challenges, this invention proposes a passive phase change cooling system for hydrogen fuel cell air compressors that couples expansion and cold energy. The system integrates an expansion energy recovery function into a composite air compressor, utilizing the high-temperature, high-pressure exhaust gas from the fuel cell stack for expansion and work. This converts the pressure energy of the exhaust gas into mechanical energy, which is directly transferred to the capillary heat pipe cooling system and indirectly fed back to the fuel cell centrifugal air compressor system. This achieves highly efficient passive cooling with zero additional power consumption, suitable for long-term reliable operation of vehicle-mounted fuel cell systems in various climatic environments.

[0006] To achieve the above objectives, this invention proposes a passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling, comprising a hydrogen fuel cell, an energy recovery centrifugal air compressor, a compression impeller, an expansion impeller, a flow channel wall, a spiral flow channel, a centrifugal pump, a vacuum pump, a water tank, a pipeline pressure regulating box, a pipeline detection component, and a pipeline control component.

[0007] The passive phase change capillary heat pipe cooling system includes a spiral flow pipe, a tube-and-shell condenser, insulated pipes, a double-layer capillary pipe, a first insulated pipe connecting the outlet of the centrifugal air compressor's flow wall and the steam inlet of the condenser, a second insulated pipe connecting the spiral flow pipe's wall gap outlet in the flow section between the centrifugal air compressor's compression wheel outlet and the hydrogen fuel cell and the steam inlet of the condenser, a third insulated pipe connecting the outlet of the internal circulation pipe (including the motor's circumference) within the centrifugal air compressor's cavity and the steam inlet of the condenser, and a fourth insulated pipe connecting the spiral flow pipe's wall gap outlet in the flow section between the fuel cell and the centrifugal air compressor's expansion wheel inlet and the steam inlet of the condenser. The spiral flow pipe includes a fluid flow pipe between its inner and outer walls, and the fluid flow pipe includes spiral blades and a double capillary flow guide layer. The tube-and-shell condenser includes a shell and fins disposed inside the shell. The heat exchanger comprises a shell-and-tube heat exchanger with an expansion airflow rectifier mounted on the outer surface of the shell. The outer wall of the condensing section is provided with several flat or corrugated metal fins, evenly arranged axially or radially. The fins are tightly bonded to the metal tubes by brazing or mechanical expansion. The tubes are all horizontally placed and connected in series. A double-layer capillary core is added in the pipeline between the tubes inside the heat exchanger and each liquid inlet of the centrifugal compressor. A vacuum pump is placed between the liquid outlet of the condenser and the inlet of each cold fluid inlet of the centrifugal air compressor. The vacuum pump assembly consists of a vacuum pump, control valves, and related pipelines. A liquid filling system is provided between the capillary core cold fluid pipeline and each cooling pipeline. The liquid filling system includes a water tank, a centrifugal pump, control valves, and related pipelines. The cooling pipeline is equipped with a pipeline pressure regulating box. The device includes a gas injection box, pressure regulating valve, safety valve, check valve, and other components, as well as all the control valves of the assembly.

[0008] The pipeline detection assembly includes temperature sensors installed in the first, second, third, and fourth insulated pipelines; temperature sensors installed at the inlet and outlet of the tube-and-shell condenser; temperature sensors installed at the inlet and outlet of the fuel cell; temperature sensors installed at the fuel cell inlet and outlet; pressure sensors installed in the first, second, third, and fourth insulated pipelines; pressure sensors installed in the pipeline pressure regulating box; pressure sensors installed at the fuel cell inlet; pressure sensors installed at the vacuum pump inlet section; vortex flow meters installed in the pipeline between the air compressor impeller outlet and the fuel cell inlet; vortex flow meters installed in the pipeline between the air compressor expander inlet and the fuel cell outlet; vortex flow meters installed at the water tank and centrifugal pump outlet sections; and temperature sensors for detecting ambient temperature.

[0009] The pipeline control assembly includes a first control valve located at the inlet water pipe of the first insulated pipeline, a second control valve located at the inlet water pipe of the second insulated pipeline, a third control valve located at the inlet water pipe of the third insulated pipeline, a fourth control valve located at the inlet water pipe of the fourth insulated pipeline, a fifth control valve located at the outlet of the vacuum pump, a sixth control valve located at the inlet of the water tank, a seventh control valve located at the outlet of the centrifugal pump, an eighth control valve located at the outlet of the pipeline pressure regulating box, a ninth solenoid valve located between the fuel cell and the centrifugal air compressor, a tenth solenoid valve located between the fuel cell and the centrifugal air compressor, and an eleventh solenoid valve located in the spiral pipeline between the compression end and the expansion end of the centrifugal air compressor.

[0010] The controller system operates synchronously with the centrifugal air compressor. The controller controls a vacuum pump equipped with a pressure sensor to detect the internal pressure of the heat pipe. The vacuum pump operates by connecting its intake port to the main circuit to extract impurities from the air inside the pipeline, creating a vacuum state inside the pipeline. The controller also controls a centrifugal pump equipped with a vortex flow meter, which delivers coolant to the pipeline according to the target operating temperature of the air compressor. Finally, the controller controls a pipeline pressure regulating box equipped with a pressure sensor, which activates protection devices immediately if any abnormality occurs in the pipeline.

[0011] The pipeline control system is designed to automatically adjust the gas flow direction, balance pressure, circulate cooling medium, and control safety within the system. While ensuring the efficient operation of the compressor, the system can precisely control the gas and heat transfer process between the heat pipe, air cooler, and gas supply device, thereby improving the overall heat dissipation efficiency and system stability.

[0012] A further improvement is that, during the operation of the centrifugal air compressor, the low-temperature gas at the expansion end cools the tubes. The cooling process does not require external power and achieves self-circulation. The self-designed spiral flow pipe, shell, and inner cavity serve as the evaporation section of the heat pipe system. Capillary force causes the condensate to flow back and continue evaporation to achieve medium circulation, which can meet the continuous high-load operation requirements of the air compressor and ensure the long-term reliability of the fuel cell system.

[0013] A further improvement is that when the centrifugal air compressor is ready to work, the air compressor system includes an expansion end operation protection system. The protection system uses a low-speed start-up to ensure that the expansion end has an initial take-off airflow, thus ensuring the reliable operation of the energy recovery end when the air compressor is running.

[0014] A further improvement is that, when the centrifugal air compressor is ready to operate, the cooling system includes a pipeline operation test system. The test system uses a centrifugal pump to perform operation tests on the capillary heat pipe pipeline to ensure that the cooling system operates in a timely manner when the air compressor is running.

[0015] A further improvement is that the spiral flow pipe uses a spiral blade structure to ensure overall cooling of the compressed gas when the liquid level is not full, thus avoiding the phenomenon that the cooling system is obstructed due to excessively high temperature in the evaporation section.

[0016] A further improvement is that the connection between the cooling system piping and the centrifugal air compressor is sealed to prevent air leakage or reduced efficiency during air compressor operation.

[0017] A further improvement is that the capillary core is formed by wrapping multiple layers of copper wire mesh around the tube wall to form a capillary layer, and the annular capillary layer is attached to increase the fluid flow efficiency.

[0018] A further improvement is that the heat pipe can be independently installed and removed, and is connected to the compressor body through a slot and a self-designed spiral pipeline, which facilitates later maintenance and compatibility with different models.

[0019] A further improvement is that the cooling system also includes temperature monitoring and over-temperature alarm. When the shell temperature exceeds the set threshold, the fin angle is automatically adjusted or a signal is issued to improve operational safety and reliability.

[0020] A further improvement is that the condenser is provided with an annular cooling air duct and a guide shroud on the outside, and the expansion end outlet is installed at the air duct inlet. High-speed cold air flows tangentially into the gap between the condenser fins along the guide box, which improves the heat dissipation uniformity of the condensing section, and sound insulation material is applied inside the guide shroud to reduce operating noise.

[0021] The passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling provided by this invention has the following advantages compared with the prior art:

[0022] This invention employs a passive phase-change cooling architecture, breaking away from the reliance on high-energy-consuming auxiliary components such as electric water pumps and cooling fans in traditional active thermal management systems. This eliminates additional parasitic power losses, thereby effectively improving the overall net power generation efficiency of the hydrogen fuel cell system.

[0023] The energy of "waste cooling" that would otherwise be directly discharged into the environment from the turbine expansion end of an air compressor is captured and used as a cold source for a phase change cooling cycle. By deeply coupling the work done by gas expansion with the latent heat of phase change, waste is turned into treasure, greatly optimizing the overall thermodynamic cycle efficiency of the fuel cell system.

[0024] To address the severe thermo-structural stress coupling failure problem that easily occurs in high-pressure, high-speed centrifugal air compressors under extreme operating conditions, phase change working fluids, with their isothermal endothermic physical properties, can provide extremely uniform and efficient surface temperature control for high-speed motors and bearing areas. This effectively avoids the formation of localized hot spots and significantly improves the operational reliability and service life of core rotating components.

[0025] This invention installs a self-designed interstage spiral flow pipe in the flow section of the centrifugal air compressor as the evaporation section of the heat pipe heat exchanger. This invention places the cooling device in the middle high-temperature zone of the compressor, rather than at the inlet or outlet position in the traditional technology. During the compression process, the gas temperature rises rapidly at the trailing edge of the impeller. The middle cooling structure of this invention can quickly remove the heat before it dissipates, significantly improving the compression efficiency of the air compressor.

[0026] Furthermore, to address the operational requirements of fuel cell air compressors in various climatic environments, this invention optimizes the capillary wick material and reflux structure, maintaining high thermal conductivity within an ambient temperature range of −50℃ to +50℃. Under complex operating conditions such as high temperature, high humidity, and low pressure, the working fluid inside the heat pipe can still stably evaporate and reflux, avoiding freezing, drying, or stagnation. Moreover, the toughness of the medium is improved under vacuum conditions, allowing the system to operate normally in extreme environments, thus meeting the long-term reliable operation requirements of on-board fuel cell systems in multiple climatic environments.

[0027] The control system is used to monitor and adjust the cooling circulation pipeline filling, fin angle adjustment, vacuum pumping, and safety protection in real time. The water tank is equipped with a liquid level sensor and a solenoid valve, which can automatically adjust the liquid replenishment according to the temperature and workload. The fuel cell inlet pipeline is equipped with a safety solenoid valve, which immediately activates the circuit breaker protection when the fuel cell malfunctions. In addition, the vacuum pump control module automatically starts and stops according to the system pressure to maintain the pipeline vacuum environment. The control system also integrates safety devices such as temperature over-limit alarm and overpressure protection to ensure that the system can operate stably under various climates and operating conditions. The overall control logic is fast-responding, energy-efficient, highly reliable, and has a high degree of automation. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make its features, characteristics, and advantages more apparent. The illustrative embodiments and descriptions of the accompanying drawings are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 Schematic diagram of a passive phase change cooling system for air compressor expansion and cold energy coupling in hydrogen fuel cells Figure 2 Schematic diagram of a finned tube heat exchanger with passive phase change cooling The components are: 1-vacuum pump; 2-water tank; 3-centrifugal pump; 4-pipeline pressure regulating box; 5-10, 26, 41, 42, 44 solenoid valves; 11-air compressor motor; 12-air suspension bearing; 13-condenser internal steam pipe; 14-condenser; 15-condenser tubes; 16-condenser fins; 17-condenser liquid pipe; 18-insulation pipe 1; 19-insulation pipe 3; 20-expansion end outlet; 21-spiral blade; 22-air compressor balance platform; 23-air compressor inner cavity; 24-casing flow wall; 25-air compressor fluid inlet; 27-internal structure of energy recovery type air compressor. ; 28-Evaporator section outlet; 29-Expansion end cryogenic fluid flow pipe; 30-Heat exchanger internal tubes; 31-Finned heat exchanger housing; 32-Cryogenic airflow rectifier; 33-Finned heat exchanger liquid outlet; 34-Insulation pipe 4; 35-Centrifugal air compressor; 36-Condenser; 37-Air compressor compression wheel; 38-Air compressor expansion wheel; 39-Insulation pipe 2; 40-Hydrogen fuel cell; 43-Air compressor compression end outlet spiral flow pipe 1; 45-Expansion end inlet spiral flow pipe 2; 46-Expansion end air replenishment spiral flow pipe 3; Default controllable components come with relevant sensors. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices. In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," "longitudinal," etc., indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings. These terms are primarily used to better describe this application and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation. Furthermore, some of the aforementioned terms may have other meanings besides indicating orientation or positional relationships; for example, the term "above" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application according to the specific circumstances. Additionally, the term "multiple" should mean two or more.

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments. Example 1

[0032] Appendix Figure 1 This is a schematic diagram of a passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling, as shown in the attached diagram. Figure 1The structure shown completes the assembly and welding of the air suspension bearing 12, centrifugal air compressor 35, spiral flow pipes 43, 45, 46, hydrogen fuel cell 40, and capillary finned heat pipe heat exchange structure. The centrifugal air compressor is fixed using a balance seat 22. The passive phase change cooling system with expansion-cold energy coupling includes a cold fluid rectifier 32, a condenser 36, a vacuum pump 1, a water tank 2, a first insulated pipe 18 connecting the centrifugal air compressor flow wall outlet 24 and the condenser steam inlet 13, a second insulated pipe 39 placed between the spiral flow pipe wall gap outlet 43 in the inter-stage flow section of the centrifugal air compressor and the condenser steam inlet 13, a third insulated pipe 19 placed between the outlet of the internal circulation pipe (including the motor 11) in the centrifugal air compressor cavity 23 and the condenser steam inlet, and a fourth insulated pipe placed between the expansion end inlet of the fuel cell air compressor and the condenser steam inlet. The condenser 36 includes a shell 31, a finned tube heat exchanger 15 disposed inside the shell, and a shroud 32 disposed on the outer surface of the shell. The outer wall of the condensing section is provided with several flat or corrugated metal fins 16, evenly arranged axially or radially. The fins 16 are tightly joined to the metal tubes by brazing or mechanical expansion. The tubes 15 are all vertically placed and connected in series 30. Capillary wicks are added in the pipes between the tubes 15 inside the heat exchanger and the liquid inlets of the centrifugal compressor 35. A vacuum pump 1 is placed between the liquid outlet 17 of the condenser 36 and the inlets 8-10 of the cold fluid inlets of the centrifugal air compressor. The vacuum pump 1 assembly consists of a vacuum pump 1, a control valve 6, and related pipes 17. A liquid filling system is provided between the capillary cold fluid pipeline 17 and each cooling pipeline. The liquid filling system includes a water tank 2, a centrifugal pump 3, a control valve 5 and related pipelines. The cooling pipeline is equipped with a pipeline pressure regulating box 4. The device includes components such as an air supply box 4, a pressure regulating valve 26, a safety valve and a check valve, as well as all control valves of the components. The pipeline detection assembly includes a temperature sensor installed in the first insulated pipeline 18, a temperature sensor installed in the second insulated pipeline 39, a temperature sensor installed in the third insulated pipeline 23, a temperature sensor installed in the fourth insulated pipeline 34, a temperature sensor installed at the inlet 13 of the tube condenser, a temperature sensor installed at the outlet 17 of the tube condenser, a temperature sensor installed at the inlet of the fuel cell, a temperature sensor installed at the outlet of the fuel cell, a pressure sensor installed in the first insulated pipeline 18, a pressure sensor installed in the second insulated pipeline 39, a pressure sensor installed in the third insulated pipeline 23, a pressure sensor installed in the fourth insulated pipeline 34, a pressure sensor installed in the pipeline pressure regulating box 4, a pressure sensor installed at the inlet of the fuel cell, a pressure sensor installed at the inlet section of the vacuum pump 3, a vortex flow meter installed in the pipeline between the outlet of the air compressor impeller 37 and the inlet of the fuel cell 40, a vortex flow meter installed in the pipeline between the inlet of the air compressor expansion impeller 38 and the outlet of the fuel cell 40, a vortex flow meter installed in the water tank 2 and the outlet section of the centrifugal pump 3, and a temperature sensor for detecting ambient temperature. The pipeline control assembly includes a first control valve located at the inlet water inlet of the first insulated pipeline 18, a second control valve located at the inlet water inlet of the second insulated pipeline 39, a third control valve located at the inlet water inlet of the third insulated pipeline 23, a fourth control valve located at the inlet water inlet of the fourth insulated pipeline 34, a fifth control valve located at the outlet of the vacuum pump 1, a sixth control valve located at the inlet of the water tank 2, a seventh control valve located at the outlet of the centrifugal pump 3, an eighth control valve located at the outlet of the pipeline pressure regulating box 4, a ninth solenoid valve located between the fuel cell 40 and the centrifugal air compressor 25, a tenth solenoid valve located between the fuel cell 40 and the centrifugal air compressor 25, and an eleventh solenoid valve located in the spiral pipeline 46 between the compression end 37 and the expansion end 38 of the centrifugal air compressor 25. Example 2

[0033] When the fuel cell air compressor 35 system starts in normal temperature mode, the passive phase change cooling system of expansion and cold energy coupling is automatically adjusted by the controller. Specifically, the controller controls the system to run synchronously with the centrifugal air compressor 35. The controller controls the vacuum pump 2, which is equipped with a pressure sensor to detect the internal pressure of the heat pipe. The vacuum pump 1 operates with its intake port connected to the main circuit to extract the impurities in the air inside the pipeline, so that a vacuum state is formed inside the pipeline. The controller controls the centrifugal pump 1, which is equipped with a vortex flow meter. The centrifugal pump 1 delivers coolant to the spiral flow pipes 43, 46, and 45 according to the target operating temperature of the air compressor. The controller controls the pipeline pressure regulating box 4, which is equipped with a pressure sensor. If the pipeline has an abnormality, the pipeline pressure regulating box 4 will activate the protection device. In addition, the controller precisely controls the controllable valves in the pipeline and the fin angle in the condenser 36. Example 3

[0034] The passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling operates year-round under various climatic conditions. The specific method is as follows: When the centrifugal air compressor 35 is ready to operate, the cooling system includes a pipeline operation test system. This test system uses a centrifugal pump 1 to test the heat pipe pipelines, ensuring the normal operation of the cooling system and expansion end energy recovery during air compressor 35 operation. The cooling target area is the high-temperature zone inside the air compressor 35, including the motor 11, the casing flow wall 24, and flow pipes 43, 46, and 45. The heat pipe evaporation end is in close contact with the aforementioned high-temperature wall, and the condensation end 36 is connected to the external finned heat exchanger 16, forming a dual-channel structure of internal gas-liquid phase change and external air convection heat dissipation. The expansion recovery end is tested by opening solenoid valves 44 and 42, driving the fuel cell air compressor 35 at low speed to test whether the expansion end 38 is operating normally. When the vehicle starts or the fuel cell system is powered on, the control module enters the cooling system preparation state, and the vacuum pump 1 evacuates the inside of the circulation pipeline until the internal vacuum level reaches a set value (approximately). The vacuum environment allows the condensate to vaporize at low saturation temperatures, thus accelerating the start-up response. Once the set vacuum value is reached, vacuum pump 1 automatically shuts off. The control system automatically starts centrifugal pump 3 based on the liquid level sensor signal, injecting coolant from water tank 2 into the cooling circuit. The coolant is directed through the main pipeline into spiral flow pipe 43, wall flow pipe 18, and inner cavity 19 via the electric regulating valve 26, providing working fluid for heat exchange. The interstage spiral flow pipe uses self-developed spiral blades 21 placed inside the condensate flow pipe to improve the heat conversion rate of the condensate to high-temperature, high-pressure fluids. This structure allows intelligent learning of the habitual average speed and inlet flow rate of the air compressor 35 when the on-board fuel cell system is powered on, enabling intelligent variable liquid filling. After filling is complete, the system automatically closes the replenishment valve, forming a closed loop. After the air compressor 35 starts, air enters the impeller through the inlet and is compressed and heated under high-speed rotation. Heat is concentrated in the impeller outlet, diffuser channel, motor cavity 11, and spiral pipe area. After the evaporation section absorbs heat, the condensate inside the heat pipe begins to vaporize. The vaporized steam is transported to the steam pipe 13 of the condenser 36 through the first insulated pipe 18, the second insulated pipe 39, the third insulated pipe 19, and the fourth insulated pipe 34, and then quickly flows into the tube 15. The insulated pipe 13 is equipped with a sheath made of corrosion-resistant PVDF material. The tube 15 uses copper tubes with high thermal conductivity and high pitting corrosion resistance. The heat exchange chamber is made of pure copper to prevent electrochemical corrosion in condensation and high humidity environments. At the same time, the air compressor expansion end 38 absorbs the airflow from the compression wheel 37 and the exhaust gas from the fuel cell 40. After expansion, the high-temperature airflow is rapidly cooled and enters the heat exchanger shroud 32 through the outlet of the expansion end 20, allowing the low-temperature airflow to fully flow through the tube 30 and the condenser fins 16 to carry away heat.The fins 16 are made of aluminum alloy and treated with epoxy resin spraying or anti-corrosion coating (PVDF coating). High-temperature steam releases heat and condenses into liquid at the condenser end. The liquid is adsorbed by the capillary pores and flows back to the evaporator end along the capillary channel, forming a gas-liquid dual-channel self-circulation. The coolant temperature is monitored by a temperature sensor, and the data is transmitted to the control module in real time. When the temperature rises above 50°C, the control system increases the fin tilt angle to increase heat exchange efficiency and ensures that the outlet temperature of the air compressor is suitable for fuel cell operation. The top of the water tank 2 is equipped with a liquid level sensor and an electric regulating valve 7. When the liquid level is below the lower limit, the system automatically replenishes the liquid, and when it reaches the upper limit, it automatically shuts off. The pipeline is equipped with a pressure regulating protection box 4, which contains a safety valve 26, a check valve, and a pressure relief port. When the internal pressure rises abnormally, the control system immediately triggers the pressure relief device to prevent damage to the heat pipe or pipeline structure. It also has automatic over-temperature speed limit alarm, liquid shortage shutdown protection, electrical overload, leakage protection, and vacuum abnormality self-repair function.

[0035] In this example, the condenser 36 is externally equipped with an annular cooling duct and a flow guide. The flow guide is installed at the duct inlet, allowing cold air to flow tangentially into the gaps between the condenser fins 16 along the flow guide, improving the uniformity of heat dissipation in the condensing section. Sound-insulating material is also applied inside the flow guide to reduce operating noise. All connections between the cooling system piping and the centrifugal air compressor 35 are sealed to prevent air leakage or efficiency reduction during compressor operation. The heat pipes are independently detachable and connected to the compressor 35 body via slots and a self-designed spiral piping system, facilitating future maintenance and compatibility with different models.

[0036] In this example, to increase heat exchange efficiency, the capillary core is formed by wrapping multiple layers of copper wire mesh around the tube wall to form a capillary layer, and the capillary core cold fluid tube is optimized into a synchronously operating annular double capillary layer cold fluid tube.

[0037] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. This invention discloses a passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling, comprising a hydrogen fuel cell, an energy recovery centrifugal air compressor, a compression impeller, an expansion impeller, a flow wall, a spiral flow pipe, a centrifugal pump, a vacuum pump, a water tank, a pipeline pressure regulating box, a pipeline detection component, and a pipeline control component, characterized in that: The passive phase change capillary heat pipe cooling system includes a spiral flow pipe, a tube-and-shell condenser, insulated pipes, a double-layer capillary tube, a first insulated pipe connecting the outlet of the centrifugal air compressor's flow wall and the steam inlet of the condenser, a second insulated pipe located between the outlet of the spiral flow pipe wall gap in the flow section between the centrifugal air compressor's compression wheel outlet and the hydrogen fuel cell and the steam inlet of the condenser, a third insulated pipe located between the outlet of the internal circulation pipe (including the motor circumference) inside the centrifugal air compressor and the steam inlet of the condenser, and a fourth insulated pipe located between the outlet of the spiral flow pipe wall gap in the flow section between the fuel cell and the centrifugal air compressor's expansion wheel inlet and the steam inlet of the condenser. The system includes a fluid flow channel between its inner and outer walls, comprising spiral blades and a double capillary core guide layer. The tube-and-shell condenser includes a shell, a finned tube-and-shell heat exchanger inside the shell, and an expansion airflow rectifier on the outer surface of the shell. The outer wall of the condensing section is provided with several flat or corrugated metal fins, uniformly arranged axially or radially. The fins are tightly bonded to the metal tubes by brazing or mechanical expansion. The tubes are horizontally placed and connected in series. A double capillary core is added to the piping between the tubes inside the heat exchanger and the liquid inlets of the centrifugal compressor. A vacuum pump is placed between the liquid outlet of the condenser and the cold fluid inlets of the centrifugal air compressor. The air pump assembly consists of a vacuum pump, control valves, and related pipelines. A liquid filling system is installed between the capillary wick cold fluid pipeline and each cooling pipeline. This liquid filling system includes a water tank, a centrifugal pump, control valves, and related pipelines. The cooling pipelines are equipped with a pipeline pressure regulating box. The device includes a gas injection box, pressure regulating valve, safety valve, and check valve, as well as all the control valves of the assembly. The pipeline detection assembly includes temperature sensors installed in the first, second, third, and fourth adiabatic pipelines, the inlet of the shell-and-tube condenser, and the outlet of the shell-and-tube condenser. Temperature sensors installed at the fuel cell inlet, temperature sensors installed at the fuel cell outlet, pressure sensors installed in the first insulated pipeline, pressure sensors installed in the second insulated pipeline, pressure sensors installed in the third insulated pipeline, pressure sensors installed in the fourth insulated pipeline, pressure sensors installed in the pipeline pressure regulating box, pressure sensors installed at the fuel cell inlet, pressure sensors installed at the vacuum pump inlet section, vortex flow meters installed in the pipeline between the air compressor compression wheel outlet and the fuel cell inlet, vortex flow meters installed in the pipeline between the air compressor expansion wheel inlet and the fuel cell outlet, vortex flow meters installed in the water tank and centrifugal pump outlet section, and temperature sensors for detecting ambient temperature; The pipeline control assembly includes a first control valve located at the inlet water pipe of the first insulated pipeline, a second control valve located at the inlet water pipe of the second insulated pipeline, a third control valve located at the inlet water pipe of the third insulated pipeline, a fourth control valve located at the inlet water pipe of the fourth insulated pipeline, a fifth control valve located at the outlet of the vacuum pump, a sixth control valve located at the inlet of the water tank, a seventh control valve located at the outlet of the centrifugal pump, an eighth control valve located at the outlet of the pipeline pressure regulating box, a ninth solenoid valve located between the fuel cell and the centrifugal air compressor, a tenth solenoid valve located between the fuel cell and the centrifugal air compressor, and an eleventh solenoid valve located in the spiral pipeline between the compression end and the expansion end of the centrifugal air compressor. The controller system operates synchronously with the centrifugal air compressor. It controls a vacuum pump equipped with a pressure sensor to detect the internal pressure of the heat pipe. This vacuum pump connects its intake port to the main circuit, extracting impurities from the air inside the pipeline to create a vacuum. The controller also controls a centrifugal pump equipped with a vortex flow meter, which delivers coolant to the pipeline according to the target operating temperature of the air compressor. Finally, it controls a pipeline pressure regulating box equipped with a pressure sensor, which activates protection devices in case of pipeline abnormalities. This pipeline control system aims to achieve automatic adjustment of gas flow direction, pressure balance, cooling medium circulation, and safety control within the system. While ensuring efficient compressor operation, this system can precisely control the gas and heat transfer process between the heat pipe, air cooler, and air supply device, thereby improving overall heat dissipation efficiency and system stability.

2. The passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling as described in claim 1, characterized in that: When the centrifugal air compressor is running, it relies on the low-temperature gas at the expansion end to cool the tubes. The cooling process does not require external power and achieves self-circulation. It relies on the self-designed spiral flow pipe, shell, and inner cavity as the evaporation section of the heat pipe system. It relies on capillary force to make the condensate flow back and continue to evaporate to achieve medium circulation, which can meet the continuous high-load operation requirements of the air compressor and ensure the long-term reliability of the fuel cell system.

3. The passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling as described in claim 1, characterized in that: When the centrifugal air compressor is ready to work, the air compressor system includes an expansion end operation protection system. The protection system uses a low-speed start-up to ensure that the expansion end has an initial take-off airflow, thus ensuring the reliable operation of the energy recovery end when the air compressor is running.

4. The passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling as described in claim 1, characterized in that: When the centrifugal air compressor is ready to work, the cooling system includes a pipeline operation test system. The test system uses a centrifugal pump to test the operation of the capillary heat pipe pipeline to ensure that the cooling system operates in a timely manner when the air compressor is running.

5. The passive phase change cooling system for hydrogen fuel cell air compressor expansion and cold energy coupling as described in claim 1, characterized in that: The spiral flow pipe uses a spiral blade structure to ensure overall cooling of the compressed gas when the liquid level is not full, thus avoiding the phenomenon that the cooling system is obstructed due to excessively high temperature in the evaporation section.

6. The passive phase change cooling system for expansion and cold energy coupling of a hydrogen fuel cell air compressor as described in claim 1, characterized in that: The insulated piping is equipped with a sheath made of corrosion-resistant PVDF material. The shell and heat exchange chamber are made of copper to prevent electrochemical corrosion in condensation and high humidity environments. The fins are made of aluminum alloy and are treated with epoxy resin spraying or anti-corrosion coating (PVDF coating) on ​​their surface. The tubes are made of copper tubes with high thermal conductivity and high pitting corrosion resistance.

7. The passive phase change cooling system for expansion and cold energy coupling of a hydrogen fuel cell air compressor as described in claim 1, characterized in that: The capillary core is formed by wrapping multiple layers of copper wire mesh around the tube wall to form a capillary layer, and the annular capillary layer is attached to increase the fluid flow efficiency.

8. The passive phase change cooling system for expansion and cold energy coupling of a hydrogen fuel cell air compressor as described in claim 1, characterized in that: The heat pipe can be independently installed and removed, and is connected to the compressor body through a slot and a self-designed spiral pipeline, which facilitates later maintenance and compatibility with different models.

9. The passive phase change cooling system for expansion and cold energy coupling of a hydrogen fuel cell air compressor as described in claim 1, characterized in that: The cooling system also includes temperature monitoring and over-temperature alarm. When the shell temperature exceeds the set threshold, it automatically adjusts the fin angle or issues a signal to improve operational safety and reliability.

10. The passive phase change cooling system for expansion and cold energy coupling of a hydrogen fuel cell air compressor as described in claim 1, characterized in that: The condenser is equipped with an annular cooling air duct and a guide shroud on the outside. The expansion end outlet is installed at the air duct inlet. High-speed cold air flows tangentially into the gap between the condenser fins along the guide box, improving the heat dissipation uniformity of the condensing section. Sound insulation material is applied inside the guide shroud to reduce operating noise.

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