Hydrogen fuel cell test stand waste heat recovery system and control method

Abstract

This invention discloses a waste heat recovery system and control method for a hydrogen fuel cell test bench, relating to the field of fuel cell testing technology. The system includes an anode hydrogen module, a cathode air module, a heat pump module, and a stack cooling module. The heat pump module is connected to the anode hydrogen module, cathode air module, and stack cooling module simultaneously. The heat pump module exchanges heat with the stack cooling module to absorb the waste heat of the coolant in the stack cooling module. Both the anode hydrogen module and the cathode air module exchange heat with the heat pump module to increase the temperature of their own circulating water. The heat pump module includes a reheating device for pressurizing and heating the heat pump working fluid after absorbing waste heat in the heat pump module. This invention replaces pure electric heating with waste heat recovery, solving the problem of no effective heat exchange temperature difference under high humidity conditions, reducing testing energy consumption, and ensuring accurate and stable inlet air temperature and humidity and stack temperature.

Description

Technical Field

[0001] This invention relates to the field of hydrogen fuel cell testing technology, and specifically to a waste heat recovery system and control method for a hydrogen fuel cell test bench. Background Technology

[0002] Hydrogen fuel cells, as a highly efficient and clean new type of power generation device, can directly convert the chemical energy of hydrogen and oxygen into electrical energy. They offer advantages such as zero pollution, high efficiency, and low noise, and are currently widely used in vehicles, ships, and distributed power generation. However, due to polarization losses, the power generation efficiency of a fuel cell stack is only about 50%, with nearly half of the energy lost as waste heat. Therefore, a cooling system is essential to maintain a stable operating temperature for the stack. Currently, the industry commonly uses liquid cooling, where coolant circulates to remove waste heat from the stack and directly discharges it. While this method meets the stack's temperature control requirements, it results in the direct waste of low-temperature, low-grade heat from the stack, leading to low overall system energy utilization efficiency.

[0003] Meanwhile, to ensure efficient and stable discharge of the fuel cell, both hydrogen and air entering the stack must be preheated and humidified to the target temperature and relative humidity. Existing commercial hydrogen fuel cell test benches generally adopt a separate architecture where the cooling system and the reaction gas temperature and humidity control system are independent, with no energy interaction between the two systems: the heat required for heating and humidifying the reaction gas is entirely supplied by the electric heater, while a large amount of waste heat generated during stack operation is directly discharged through the cooling system, resulting in an energy mismatch where one side consumes electricity for heating and the other side wastes waste heat; in long-term continuous operation scenarios such as durability testing, variable operating condition cycle testing, and long-term stability testing, the electric heater needs to maintain high load operation for a long time, resulting in high energy consumption and overall operating costs of the test bench.

[0004] Especially under high-humidity conditions where bubbling humidification is commonly used for reactant gases, the water temperature inside the humidification tank is roughly the same as, or even slightly higher than, the coolant outlet temperature of the fuel cell stack. Conventional heat exchangers rely on the temperature difference between the hot and cold media to transfer heat. When the water temperature on the heated side is not lower than the coolant temperature on the waste heat side, an effective heat exchange temperature difference cannot be formed. This means that relying solely on conventional passive heat exchange structures cannot utilize the low-grade waste heat from the fuel cell stack for heating and humidifying the reactant gases, becoming a key bottleneck restricting the improvement of energy utilization efficiency in fuel cell testing systems.

[0005] In summary, existing hydrogen fuel cell test benches lack the technical means to improve the quality and recover low-grade waste heat from the fuel cell stack, making it difficult to achieve resource utilization of waste heat while simultaneously ensuring precise control of the temperature and humidity of the reaction gases and constant temperature dissipation of the fuel cell stack. Therefore, a novel waste heat recovery system and control method for hydrogen fuel cell test benches is urgently needed to solve the aforementioned problems in existing technologies. Summary of the Invention

[0006] The purpose of this invention is to provide a waste heat recovery system for a hydrogen fuel cell test bench. This system addresses the problems of existing hydrogen fuel cell test benches where the cooling system and the reaction gas temperature and humidity control system are independent, low-grade waste heat from the fuel cell stack is directly discharged, and the heating and humidification of the reaction gas relies entirely on electric heating. Furthermore, conventional heat exchangers cannot utilize this waste heat under high humidity conditions due to a lack of effective heat exchange temperature difference. This results in low system energy utilization efficiency, high energy consumption during long-term continuous testing, and high overall costs. The specific technical solution is as follows: A waste heat recovery system for a hydrogen fuel cell test bench includes an anode hydrogen module, a cathode air module, a heat pump module, and a stack cooling module, wherein the heat pump module is simultaneously connected to the anode hydrogen module, the cathode air module, and the stack cooling module. The heat pump module exchanges heat with the fuel cell stack cooling module to absorb the waste heat of the coolant in the fuel cell stack cooling module. Both the anode hydrogen module and the cathode air module exchange heat with the heat pump module to increase the temperature of their own circulating water. The heat pump module includes a heat replenishment device, which is used to pressurize and heat up the heat pump working fluid after it has absorbed waste heat in the heat pump module.

[0007] Preferably, the heat pump module further includes an evaporator, a gas-liquid separator, an oil separator, a working fluid distribution valve, a first condenser, a second condenser, a third condenser, and a main expansion valve; The evaporator, gas-liquid separator, heat replenishment device, oil separator, and working fluid distribution valve are connected in series. The two outlets of the working fluid distribution valve are respectively connected to the inlets of the first condenser and the second condenser. The outlets of the first condenser and the second condenser are both connected to the inlet of the third condenser. The outlet of the third condenser is connected to the inlet of the evaporator through the main expansion valve, forming a heat pump working fluid circulation loop. The evaporator exchanges heat with the fuel cell stack cooling module, the first condenser exchanges heat with the cathode air module, and the second condenser exchanges heat with the anode hydrogen module.

[0008] Preferably, the heat pump module further includes a liquid injection valve and a hot gas bypass valve; The inlet of the liquid injection valve is connected to the outlet of the third condenser, and the outlet of the liquid injection valve is connected to the inlet of the gas-liquid separator. The inlet of the hot gas bypass valve is connected to the outlet of the oil separator, and the outlet of the hot gas bypass valve is connected to the inlet of the gas-liquid separator.

[0009] Preferably, the heat pump module further includes a suction pressure sensor, a suction temperature sensor, an exhaust temperature sensor, a condensation temperature sensor, and a condensation pressure sensor; The intake pressure sensor and the intake temperature sensor are located between the outlet of the gas-liquid separator and the inlet of the heating device. The exhaust temperature sensor is located between the outlet of the heating device and the inlet of the oil separator; The condensation temperature sensor and condensation pressure sensor are located at the outlet of the third condenser.

[0010] Preferably, the anode hydrogen module includes a hydrogen heating and humidification circulation loop, which includes an anode humidification tank, a first circulating water pump, a first water circuit switch valve, a second heater, and a first heat exchanger connected in series to form the loop. The water-side inlet of the second condenser is connected to the inlet side of the first water circuit switch valve through the first waste heat utilization valve, and the water-side outlet of the second condenser is connected to the outlet side of the first water circuit switch valve through the second waste heat utilization valve.

[0011] Preferably, the cathode air module includes an air heating and humidification circulation loop, which includes a cathode humidification tank, a second circulating water pump, a second water circuit switch valve, a fourth heater, and a second heat exchanger connected in series to form the loop. The water-side inlet of the first condenser is connected to the inlet side of the second water circuit switch valve through the third waste heat utilization valve, and the water-side outlet of the first condenser is connected to the outlet side of the second water circuit switch valve through the fourth waste heat utilization valve.

[0012] Preferably, the fuel cell stack cooling module includes a fuel cell stack, a coolant pump, a coolant on / off valve, and a third heat exchanger connected in series to form a circuit; The coolant inlet of the evaporator is connected to the inlet side of the coolant switch valve through the sixth waste heat utilization valve, and the coolant outlet of the evaporator is connected to the outlet side of the coolant switch valve through the fifth waste heat utilization valve.

[0013] Preferably, the fuel cell stack is provided with a coolant outlet temperature sensor at the coolant outlet and a coolant inlet temperature sensor at the coolant inlet.

[0014] This invention also provides a waste heat recovery control method for a hydrogen fuel cell test bench, employing the aforementioned waste heat recovery system for the hydrogen fuel cell test bench, comprising: The condensation temperature of the heat pump working fluid in the heat pump module is controlled to be higher than the larger of the target dew point temperatures of the anode hydrogen module and the cathode air module, and the evaporation temperature of the heat pump working fluid is controlled to be lower than the set operating temperature of the fuel cell stack. The real-time heat load requirements of the anode hydrogen module, the real-time heat load requirements of the cathode air module, and the recoverable waste heat of the coolant in the fuel cell stack cooling module are obtained. The difference between the sum of the real-time heat load requirements of the anode hydrogen module and the real-time heat load requirements of the cathode air module and the recoverable waste heat is taken as the target supplementary heat load of the heat pump module. The heat pump module's heat replenishment device pressurizes and heats the heat pump working fluid after absorbing recoverable waste heat according to the target heat replenishment load. Based on the ratio of the real-time heat load demand of the anode hydrogen module to the real-time heat load demand of the cathode air module, the distribution ratio of the pressurized and heated heat pump working fluid to the anode hydrogen module and the cathode air module is adjusted so that the heat obtained by the anode hydrogen module and the cathode air module matches their own real-time heat load demand.

[0015] Preferably, the heat pump working fluid, after absorbing recoverable waste heat, is pressurized and heated according to the target heat replenishment load, specifically as follows: If the target heating load is less than or equal to the minimum operating load of the heating device, the heating device shall operate at the minimum operating load. If the target heat replenishment load is greater than the minimum operating load of the heat replenishment device and less than or equal to the maximum operating load of the heat replenishment device, then the heat replenishment device shall operate at the target heat replenishment load. If the target heat replenishment load is greater than the maximum operating load of the heat replenishment device, the heat replenishment device will operate at the maximum operating load.

[0016] The application of the technical solution of the present invention has the following beneficial effects: The heat pump module of this invention is connected to the fuel cell stack cooling module, the anode hydrogen module, and the cathode air module. After its evaporator absorbs the low-grade waste heat carried by the fuel cell stack coolant, the heat pump working fluid after heat absorption is pressurized and heated by the heat replenishment device, so that the condensation temperature of the working fluid is higher than the larger of the target dew point temperatures on both sides. Thus, even under high humidity conditions where the waste heat side temperature is not originally dominant, it can still actively establish a positive heat exchange temperature difference, and upgrade the low-grade waste heat that could not be directly utilized and could only be directly discharged into high-grade heat energy that meets the heating and humidification requirements of the reaction gas. This overcomes the inherent defect of conventional passive heat exchangers that cannot recover waste heat under high humidity conditions.

[0017] This invention connects the originally independent heat dissipation circuit of the fuel cell stack with the heating and humidification circuits of the reactant gases on both sides through a heat pump module. The heating and humidification circulating water of the anode and cathode is now mainly supplied by the corresponding condensers using the waste heat after heat treatment. Each electric heater only provides auxiliary heating when the system starts up, when the waste heat is insufficient, or when the supplementary heating device is at full load but still has a shortage. This changes the heating structure that relies entirely on electric heating for the heating and humidification of the reactant gases. Since durability testing and variable operating condition cycle testing are characterized by long duration and uninterrupted operation, this system can significantly reduce the power consumption of the test bench and the long-term comprehensive operating cost.

[0018] This invention controls the condensation temperature of the heat pump working fluid to be higher than the larger of the target dew point temperatures on both sides, and controls the evaporation temperature to be lower than the set operating temperature of the fuel cell stack. This ensures that the heat pump working fluid has a positive heat exchange temperature difference relative to the circulating water on the condenser side and relative to the coolant on the evaporator side. This controls the heat transfer to be carried out in the expected direction and maximizes the recovery of low-grade waste heat without compromising the heat dissipation of the fuel cell stack.

[0019] This invention obtains the real-time heat load demand of the anode and cathode reaction gases and the recoverable waste heat of the coolant. The target heat load of the heat replenishment device is determined by the difference between the sum of the heat load demand on both sides and the recoverable waste heat. Then, the distribution ratio of the heat pump working fluid after pressurization and heating is adjusted according to the ratio of the real-time heat load demand on both sides, so that the total heat supply is offset by the total demand and the heat obtained by each side is matched with its own demand, thus avoiding insufficient or excessive heat supply.

[0020] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the anode hydrogen module in the waste heat recovery system of Example 1; Figure 2 This is a schematic diagram of the cathode air module in the waste heat recovery system of Example 1; Figure 3 This is a schematic diagram of the structure of the heat pump module and the fuel cell stack cooling module in the waste heat recovery system of Example 1; Figure 4 This is a flowchart of the waste heat recovery control method for the hydrogen fuel cell test bench in Example 2; The components are as follows: 1. Hydrogen source; 2. Hydrogen inlet temperature sensor; 3. First dry gas mass flow controller; 4. First heater; 5. First humidity temperature sensor; 6. Anode humidification tank; 7. First humidified gas mass flow controller; 8. First water temperature sensor; 9. First circulating water pump; 10. First waste heat recovery valve; 11. First water circuit switch valve; 12. Second waste heat recovery valve; 13. Second heater; 14. First heat exchanger; 15. Air source; 16. Air inlet temperature sensor; 17. Second dry gas mass flow controller; 18. Third heater; 19. Second humidity temperature sensor; 20. Cathode humidification tank; 21. Second humidified gas mass flow controller; 22. Second water temperature sensor; 23. Second circulating water pump; 24. Third waste heat recovery valve. 25. Second water circuit switch valve; 26. Fourth waste heat recovery valve; 27. Fourth heater; 28. Second heat exchanger; 29. ​​Coolant pump; 30. Coolant outlet temperature sensor; 31. Fuel cell stack; 32. Coolant inlet temperature sensor; 33. Third heat exchanger; 34. Fifth waste heat recovery valve; 35. Coolant switch valve; 36. Sixth waste heat recovery valve; 37. Evaporator; 38. Suction pressure sensor; 39. Suction temperature sensor; 40. Gas-liquid separator; 41. Compressor; 42. Discharge temperature sensor; 43. Oil separator; 44. Working fluid distribution valve; 45. First condenser; 46. Second condenser; 47. Third condenser; 48. Condensation temperature sensor; 49. Condensation pressure sensor; 50. Main expansion valve; 51. Injection valve; 52. Hot gas bypass valve. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more complete description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0024] Example 1: Reference Figures 1-3This embodiment provides a waste heat recovery system for a hydrogen fuel cell test bench. The system includes an anode hydrogen module, a cathode air module, a heat pump module, and a fuel cell stack cooling module. The heat pump module is connected to the anode hydrogen module, the cathode air module, and the fuel cell stack cooling module simultaneously. The heat pump module exchanges heat with the fuel cell stack cooling module to absorb the waste heat of the coolant in the fuel cell stack cooling module. Both the anode hydrogen module and the cathode air module exchange heat with the heat pump module to increase the temperature of their own circulating water. The heat pump module includes a heat replenishment device for pressurizing and heating the heat pump working fluid after absorbing waste heat in the heat pump module.

[0025] Preferably, the heat replenishment device in this embodiment is a compressor 41. In other embodiments, the heat replenishment device may also take other forms, as long as it can pressurize and heat the heat pump working fluid after absorbing waste heat, and upgrade the low-grade waste heat into high-grade heat energy.

[0026] Reference Figure 3 The heat pump module includes an evaporator 37, a gas-liquid separator 40, a compressor 41, an oil separator 43, a working fluid distribution valve 44, a first condenser 45, a second condenser 46, a third condenser 47, and a main expansion valve 50. The evaporator 37, gas-liquid separator 40, compressor 41, oil separator 43, and working fluid distribution valve 44 are connected in series. The two outlets of the working fluid distribution valve 44 are connected to the inlets of the first condenser 45 and the second condenser 46, respectively. The outlets of the first condenser 45 and the second condenser 46 are both connected to the inlet of the third condenser 47. The outlet of the third condenser 47 is connected to the inlet of the evaporator 37 via the main expansion valve 50, forming a heat pump working fluid circulation loop. The evaporator 37 exchanges heat with the fuel cell stack cooling module, the first condenser 45 exchanges heat with the cathode air module via interfaces B1 and B2, and the second condenser 46 exchanges heat with the anode hydrogen module via interfaces A1 and A2.

[0027] Specifically, the evaporator 37 is a heat pump working fluid heat absorption component. Coolant from the fuel cell stack cooling module flows through one side of it, and heat pump working fluid flows through the other side. It is used to absorb the low-grade waste heat of the fuel cell stack carried by the coolant, so that the low-pressure liquid heat pump working fluid absorbs heat and evaporates into a low-pressure gaseous working fluid.

[0028] Furthermore, the gas-liquid separator 40 is disposed between the outlet of the evaporator 37 and the inlet of the compressor 41 to perform gas-liquid two-phase separation on the heat pump working fluid flowing out of the evaporator 37, ensuring that the working fluid entering the compressor 41 is in a gaseous state and preventing liquid slugging from occurring in the compressor 41.

[0029] Furthermore, the compressor 41 is a quality improvement component of the heat pump module, used to pressurize and heat the low-pressure, low-temperature heat pump working fluid after absorbing waste heat, converting the low-grade waste heat that cannot be directly utilized into high-grade heat energy with a temperature grade that meets the heating and humidification requirements of the reaction gas.

[0030] Furthermore, the oil separator 43 is located between the outlet of the compressor 41 and the inlet of the working fluid distribution valve 44. It separates the lubricating oil carried in the exhaust of the compressor 41, purifies the heat pump working fluid, and prevents lubricating oil from entering the subsequent condenser and affecting heat exchange efficiency. Simultaneously, the oil separator 43 is also connected to the compressor 41 via a pipeline, allowing the separated lubricating oil to return to the compressor 41, preventing the lubricating oil from being carried away by the heat pump working fluid and causing the compressor 41 to lack lubricating medium, thus affecting its service life.

[0031] Furthermore, the working fluid distribution valve 44 is a three-way proportional regulating valve. Its inlet is connected to the outlet of the oil separator 43, and its two outlets are connected to the inlets of the first condenser 45 and the second condenser 46, respectively. It is used to proportionally distribute the high-temperature and high-pressure heat pump working fluid according to the real-time heat load requirements of the anode hydrogen module and the cathode air module, so as to realize the independent regulation of the heat supply of the anode and cathode.

[0032] Furthermore, both the first condenser 45 and the second condenser 46 are water-side heat exchange components where the heat pump working fluid releases heat to the circulating water. The water side of the first condenser 45 is connected to the circulating water circuit of the cathode air module via interfaces B1 and B2, transferring the heat of the heat pump working fluid to the circulating water in the cathode air module; the water side of the second condenser 46 is connected to the circulating water circuit of the anode hydrogen module via interfaces A1 and A2, transferring the heat of the heat pump working fluid to the circulating water in the anode hydrogen module.

[0033] Furthermore, the inlet of the third condenser 47 is simultaneously connected to the outlets of the first condenser 45 and the second condenser 46, so that the heat pump working fluids after completing the heat exchange between the anode and cathode converge and enter the third condenser 47 in a unified manner; the third condenser 47 is used for pressure stabilization and temperature regulation, and uniformly regulates the condensation temperature and subcooling of the heat pump working fluid to stabilize the condensation conditions of the system.

[0034] The other side of the third condenser 47 is the cooling side, which is connected to a first cooling circuit. A cooling medium flows through the first cooling circuit to further cool and subcool the heat pump working fluid after the flow converges, so as to regulate the condensation temperature and subcooling degree of the heat pump working fluid. In addition, the third condenser 47 can also be cooled by cooling air, and the specific cooling method is not limited.

[0035] Furthermore, the main expansion valve 50 is located between the outlet of the third condenser 47 and the inlet of the evaporator 37, and is used to throttle and reduce the pressure of the high-pressure liquid heat pump working fluid, so that the working fluid pressure is reduced to the evaporation pressure and then enters the evaporator 37 to absorb heat and evaporate.

[0036] Preferably, the heat pump module further includes a liquid injection valve 51 and a hot gas bypass valve 52 to ensure stable operation of the heat pump system under multiple operating conditions.

[0037] The inlet of the injection valve 51 is connected to the outlet of the third condenser 47, and the outlet of the injection valve 51 is connected to the inlet of the gas-liquid separator 40. When the discharge temperature of the compressor 41 is too high and there is a risk of high temperature overload, the injection valve 51 is opened to throttle the high-pressure liquid heat pump working fluid at the outlet of the third condenser 47 and inject it into the inlet of the gas-liquid separator 40, thereby reducing the intake temperature of the compressor 41 and thus reducing the discharge temperature, preventing the compressor 41 from being damaged due to excessively high discharge temperature.

[0038] Furthermore, the inlet of the hot gas bypass valve 52 is connected to the outlet of the oil separator 43, and the outlet of the hot gas bypass valve 52 is connected to the inlet of the gas-liquid separator 40. When the system suction pressure is too low or the heating condition fluctuates, the hot gas bypass valve 52 is opened to bypass the high-temperature and high-pressure heat pump working fluid at the outlet of the oil separator 43 to the inlet of the gas-liquid separator 40, thereby increasing the system suction pressure, stabilizing the operating condition of the compressor 41, and preventing the evaporation temperature from dropping below the freezing point due to the low suction pressure, which could cause the coolant in the evaporator 37 to freeze and block or crack the heat exchanger. At the same time, it also prevents the compressor 41 from triggering low-pressure protection shutdown.

[0039] Preferably, the heat pump module further includes a suction pressure sensor 38, a suction temperature sensor 39, an exhaust temperature sensor 42, a condensing temperature sensor 48, and a condensing pressure sensor 49, which are used to monitor the operating conditions of the heat pump system in real time and provide data support for the control of the liquid injection valve 51, the hot gas bypass valve 52, the main expansion valve 50, and the compressor 41.

[0040] Specifically, the suction pressure sensor 38 and suction temperature sensor 39 are positioned between the outlet of the gas-liquid separator 40 and the inlet of the compressor 41, respectively, to monitor the suction pressure and suction temperature of the compressor 41 in real time. The suction pressure is the basis for the operation of the hot gas bypass valve 52. There is no specific requirement for the position of the suction pressure sensor 38 and suction temperature sensor 39 in the flow direction of the heat pump working fluid; either the suction pressure sensor 38 or the suction temperature sensor 39 can be positioned in front. The discharge temperature sensor 42 is positioned between the outlet of the compressor 41 and the inlet of the oil separator 43, to monitor the discharge temperature of the compressor 41 in real time. The discharge temperature is the basis for the operation of the liquid injection valve 51. The condensing temperature sensor 48 and condensing pressure sensor 49 are located at the outlet of the third condenser 47 to monitor the condensing temperature and condensing pressure of the heat pump working fluid in real time, respectively. The operating data collected by the condensing temperature sensor 48 and condensing pressure sensor 49 are fed back to the third condenser 47 to coordinate with the third condenser 47 to uniformly regulate the condensing temperature and subcooling of the heat pump working fluid, and at the same time provide a basis for adjusting the opening of the main expansion valve 50.

[0041] Reference Figure 1The anode hydrogen module includes a hydrogen source 1, a dry hydrogen branch, a humidified hydrogen branch, a first heater 4, and a hydrogen heating and humidification circulation loop.

[0042] Specifically, the hydrogen heating and humidification circulation loop includes an anode humidification tank 6, a first circulating water pump 9, a first water circuit switch valve 11, a second heater 13, and a first heat exchanger 14 connected in series to form the loop. The anode humidification tank 6 is a bubbling humidification container that also serves as a water storage container for circulating water. The circulating water flowing out of its bottom outlet is driven by the first circulating water pump 9, flows sequentially through the first water circuit switch valve 11, the second heater 13, and the first heat exchanger 14, and then flows back to the anode humidification tank 6.

[0043] Furthermore, the anode hydrogen module also includes a first waste heat utilization valve 10 and a second waste heat utilization valve 12; the water-side inlet of the second condenser 46 is connected to the inlet side of the first water circuit switch valve 11 via interface A1 and the first waste heat utilization valve 10, and the water-side outlet of the second condenser 46 is connected to the outlet side of the first water circuit switch valve 11 via interface A2 and the second waste heat utilization valve 12, so that the second condenser 46 is connected in parallel to the two ends of the first water circuit switch valve 11 via the first waste heat utilization valve 10 and the second waste heat utilization valve 12. The first waste heat utilization valve 10 and the second waste heat utilization valve 12 are used to control the on / off connection between the circulating water in the anode hydrogen module and the second condenser 46 of the heat pump module.

[0044] Furthermore, the first circulating water pump 9 provides power for the flow of anode circulating water, and the first water circuit switch valve 11 controls the on / off state of the conventional heating and humidification water circuit, closing when using a heat pump module for heating and opening when using conventional electric heating. The second heater 13 is an auxiliary electric heater, supplementing the heating of circulating water when the heat pump waste heat is insufficient or during system startup, ensuring that the water temperature in the anode humidification tank 6 reaches the target value. The first heat exchanger 14 is a heat dissipation component, cooling the circulating water when the water temperature in the tank is too high, preventing the hydrogen from overheating or the water in the tank from boiling. The bottom of the anode humidification tank 6 is equipped with a first water temperature sensor 8 (of course, the first water temperature sensor 8 can also be set between the bottom outlet of the anode humidification tank 6 and the first circulating water pump 9), which is used to monitor the circulating water temperature in the anode humidification tank 6 in real time, providing a basis for power adjustment of the second heater 13 and start / stop control of the first heat exchanger 14.

[0045] Specifically, the hydrogen source 1 is a high-pressure hydrogen storage cylinder. The high-pressure hydrogen in the cylinder is output after depressurization to provide the hydrogen required for the anode reaction. A hydrogen inlet temperature sensor 2 is installed at its outlet to monitor the initial temperature of the hydrogen inlet in real time. Both the dry hydrogen branch and the humidified hydrogen branch are connected to the outlet of hydrogen source 1 and are located downstream of hydrogen inlet temperature sensor 2. The hydrogen output from hydrogen source 1 is divided into two paths: the dry hydrogen branch includes a first dry gas mass flow controller 3, which regulates the flow rate of hydrogen to form dry hydrogen and delivers it to the confluence point; the humidified hydrogen branch includes a first humidifying gas mass flow controller 7, which regulates the flow rate of hydrogen and connects it in series to the anode humidification tank 6. Hydrogen enters from the bottom of the anode humidification tank 6, bubbles in the circulating water inside the tank, carries water vapor, and flows out from the top, achieving hydrogen humidification and heating. The humidified and heated hydrogen is then monitored by a first humidity temperature sensor 5 located at the outlet of the anode humidification tank 6 and delivered to the confluence point to merge with the dry hydrogen from the dry hydrogen branch. After the dry hydrogen branch and the humidified hydrogen branch merge, the hydrogen is heated to the target temperature by the first heater 4 and delivered to the anode inlet of the fuel cell stack. By adjusting the flow ratio of the first dry gas mass flow controller 3 and the first humidifying gas mass flow controller 7, and combining this with the temperature adjustment of the circulating water in the anode humidification tank 6 and the heating power of the first heater 4, precise control of the temperature and humidity of the anode hydrogen can be achieved.

[0046] Specifically, the hydrogen heating and humidification circulation loop has two operating modes: heat pump module heating and conventional electric heating. When using heat pump module heating, the first water circuit switch valve 11 is closed, and the first waste heat utilization valve 10 and the second waste heat utilization valve 12 are opened. The circulating water in the anode hydrogen module flows out from the first circulating water pump 9, enters the second condenser 46 via the first waste heat utilization valve 10 to absorb heat from the heat pump working fluid, then flows out via the second waste heat utilization valve 12 and into the inlet side of the second heater 13. Subsequently, it flows back to the anode humidification tank 6 via the second heater 13 and the first heat exchanger 14. When using conventional electric heating, the first water circuit switch valve 11 is opened, and the first waste heat utilization valve 10 and the second waste heat utilization valve 12 are closed. The circulating water directly enters the second heater 13 for heating via the first water circuit switch valve 11. Furthermore, when using heat pump module heating, the second heater 13 or the first heat exchanger 14 can also be turned on as needed to further heat or cool the circulating water.

[0047] Reference Figure 2 The cathode air module includes an air source 15, a dry air branch, a humidified air branch, a third heater 18, and an air heating and humidification circulation loop.

[0048] Specifically, the air heating and humidification circulation loop includes a cathode humidification tank 20, a second circulating water pump 23, a second water circuit switch valve 25, a fourth heater 27, and a second heat exchanger 28 connected in series to form the loop. The cathode humidification tank 20 is a bubble-type humidification container that also serves as a water storage container for circulating water. The circulating water flowing out of its bottom outlet is driven by the second circulating water pump 23, flows sequentially through the second water circuit switch valve 25, the fourth heater 27, and the second heat exchanger 28, and then flows back to the cathode humidification tank 20.

[0049] Furthermore, the cathode air module also includes a third waste heat utilization valve 24 and a fourth waste heat utilization valve 26; the water-side inlet of the first condenser 45 is connected to the inlet side of the second water circuit switch valve 25 via interface B1 and the third waste heat utilization valve 24, and the water-side outlet of the first condenser 45 is connected to the outlet side of the second water circuit switch valve 25 via interface B2 and the fourth waste heat utilization valve 26, so that the first condenser 45 is connected in parallel to both ends of the second water circuit switch valve 25 via the third waste heat utilization valve 24 and the fourth waste heat utilization valve 26. The third waste heat utilization valve 24 and the fourth waste heat utilization valve 26 are used to control the on / off connection between the circulating water in the cathode air module and the first condenser 45 of the heat pump module.

[0050] Furthermore, the second circulating water pump 23 provides power for the flow of cathode circulating water, and the second water circuit switch valve 25 is used to control the on / off state of the conventional heating and humidification water circuit, closing when using a heat pump module for heating and opening when using conventional electric heating. The fourth heater 27 is an auxiliary electric heater, which supplements the heating of circulating water when the heat pump waste heat is insufficient or during system startup, ensuring that the water temperature in the cathode humidification tank 20 reaches the target value. The second heat exchanger 28 is a heat dissipation component, which cools the circulating water when the water temperature in the tank is too high, preventing the water temperature from being too high and causing the air to overheat or the water in the tank to boil. The bottom of the cathode humidification tank 20 is equipped with a second water temperature sensor 22 (of course, the second water temperature sensor 22 can also be set between the bottom outlet of the cathode humidification tank 20 and the second circulating water pump 23), which is used to monitor the circulating water temperature in the cathode humidification tank 20 in real time, providing a basis for the power adjustment of the fourth heater 27 and the start / stop control of the second heat exchanger 28.

[0051] Specifically, the air source 15 is an air compressor used to provide compressed air required for the cathode reaction. An air intake temperature sensor 16 is installed at its outlet to monitor the initial temperature of the incoming air in real time. Both the dry air branch and the humidifying air branch are connected to the outlet of the air source 15 and are located downstream of the air intake temperature sensor 16. The air output from the air source 15 is divided into two paths: the dry air branch includes a second dry gas mass flow controller 17, which regulates the flow rate of the air to form dry air, which is then transported to the confluence point; the humidifying air branch includes a second humidifying gas mass flow controller 21, which regulates the flow rate of the air before connecting it in series with the cathode humidification tank 20. The air enters from the bottom of the cathode humidification tank 20, bubbles in the circulating water inside the tank, carries water vapor, and then flows out from the top, achieving air humidification and heating. The humidified and heated air is then transported to the confluence point after its temperature is monitored by a second humidity temperature sensor 19 located at the outlet of the cathode humidification tank 20, where it merges with the dry air from the dry air branch. After the dry air branch and the humidified air branch merge, the air is heated to the target temperature by the third heater 18 and then delivered to the cathode inlet of the fuel cell stack. By adjusting the flow ratio of the second dry gas mass flow controller 17 and the second humidified gas mass flow controller 21, and in combination with the temperature adjustment of the circulating water in the cathode humidification tank 20 and the heating power of the third heater 18, precise control of the cathode air temperature and humidity can be achieved.

[0052] Specifically, the air heating and humidification circulation loop has two operating modes: heat pump module heating and conventional electric heating. When using heat pump module heating, the second water circuit switch valve 25 is closed, and the third waste heat utilization valve 24 and the fourth waste heat utilization valve 26 are opened. The circulating water in the cathode air module flows out from the second circulating water pump 23, enters the water side of the first condenser 45 through the third waste heat utilization valve 24 to absorb heat from the heat pump working fluid, then flows out through the fourth waste heat utilization valve 26 and into the inlet side of the fourth heater 27. Subsequently, it flows back to the cathode humidification tank 20 through the fourth heater 27 and the second heat exchanger 28. When using conventional electric heating, the second water circuit switch valve 25 is opened, and the third waste heat utilization valve 24 and the fourth waste heat utilization valve 26 are closed. The circulating water directly enters the fourth heater 27 for heating through the second water circuit switch valve 25. Furthermore, when using heat pump module heating, the fourth heater 27 or the second heat exchanger 28 can also be opened as needed to further heat or cool the circulating water.

[0053] Reference Figure 3The fuel cell stack cooling module includes a fuel cell stack 31, a coolant pump 29, a coolant switching valve 35, and a third heat exchanger 33 connected in series to form a loop. Waste heat generated by the fuel cell stack 31 is carried away by the coolant. The coolant flows out from the coolant outlet of the fuel cell stack 31, is driven by the coolant pump 29, flows sequentially through the coolant switching valve 35 and the third heat exchanger 33, and then flows back to the coolant inlet of the fuel cell stack 31, forming a coolant circulation loop. The fuel cell stack 31 is a hydrogen fuel cell stack and is the source of waste heat for the system; the coolant pump 29 provides power for the coolant circulation; the coolant switching valve 35 controls the on / off state of the conventional cooling water circuit, closing it in waste heat recovery mode and opening it in conventional heat dissipation mode; the third heat exchanger 33 is an auxiliary forced cooling component, which forcibly dissipates heat from the coolant when the temperature of the fuel cell stack 31 is too high or waste heat recovery cannot meet the heat dissipation requirements, ensuring the stable operating temperature of the fuel cell stack 31.

[0054] The third heat exchanger 33 is connected to a second cooling circuit on the other side. A cooling medium flows through the second cooling circuit to dissipate the heat carried by the coolant to the outside. The second cooling circuit can be controlled to be turned on and off. It is turned on when the temperature of the fuel cell stack 31 is too high or the waste heat recovery cannot meet the heat dissipation requirements, and turned off under other operating conditions so that the waste heat can be recovered first through the evaporator 37.

[0055] Furthermore, the fuel cell stack cooling module also includes a fifth waste heat recovery valve 34 and a sixth waste heat recovery valve 36, used to control the on / off connection between the coolant and the evaporator 37 of the heat pump module. The coolant-side inlet of the evaporator 37 is connected to the inlet side of the coolant switching valve 35 through the sixth waste heat recovery valve 36, and the coolant-side outlet of the evaporator 37 is connected to the outlet side of the coolant switching valve 35 through the fifth waste heat recovery valve 34. When using the waste heat recovery mode, the coolant switch valve 35 is closed, and the fifth waste heat utilization valve 34 and the sixth waste heat utilization valve 36 are opened. After the coolant flows out from the coolant pump 29, it enters the coolant side of the evaporator 37 through the sixth waste heat utilization valve 36, transferring the low-grade waste heat carried by the fuel cell stack to the heat pump working fluid. Then, it flows out through the fifth waste heat utilization valve 34 and into the inlet side of the third heat exchanger 33, and then flows back to the fuel cell stack 31 through the third heat exchanger 33. When using the conventional heat dissipation mode, the coolant switch valve 35 is opened, and the fifth waste heat utilization valve 34 and the sixth waste heat utilization valve 36 are closed. The coolant directly enters the third heat exchanger 33 for heat dissipation through the coolant switch valve 35.

[0056] Furthermore, a coolant outlet temperature sensor 30 is provided at the coolant outlet of the fuel cell stack 31, and a coolant inlet temperature sensor 32 is provided at the coolant inlet, to monitor the outlet and inlet temperatures of the coolant in the fuel cell stack 31 in real time. In this embodiment, the coolant pump 29 operates at a constant speed to keep the mass flow rate of the coolant in the coolant circuit constant. Under the condition of constant flow rate, the temperature difference between the inlet and outlet of the coolant flowing through the fuel cell stack 31 directly reflects the heat load per unit flow of the fuel cell stack 31. By monitoring the inlet and outlet temperatures and calculating the temperature difference through the coolant outlet temperature sensor 30 and the coolant inlet temperature sensor 32, the heat dissipation status of the fuel cell stack 31 can be determined: when the inlet and outlet temperature difference is greater than the temperature difference threshold (preferably 5°C in this embodiment), it indicates that the current heat generation of the fuel cell stack 31 has exceeded the upper limit that the evaporator 37 can handle alone, and the heat dissipation demand cannot be met by waste heat recovery alone. The third heat exchanger 33 is then activated for auxiliary forced heat dissipation.

[0057] In this embodiment, the waste heat recovery system of the hydrogen fuel cell test bench operates in concert with each module to achieve the improved recovery and resource utilization of low-grade waste heat from the fuel cell stack. The specific working process is as follows: Waste heat recovery stage: During operation, the fuel cell stack 31 continuously generates waste heat, which is carried by the coolant. The system closes the coolant switch valve 35 and opens the fifth waste heat utilization valve 34 and the sixth waste heat utilization valve 36. The coolant flows through the coolant side of the evaporator 37 and exchanges heat with the heat pump working fluid, transferring the low-grade waste heat of the fuel cell stack to the heat pump working fluid, thus completing the waste heat recovery.

[0058] Heat pump upgrading stage: The low-pressure, low-temperature heat pump working fluid, after absorbing waste heat, flows out from the evaporator 37, passes through the gas-liquid separator 40 for gas-liquid separation, and enters the compressor 41 after being monitored by the suction pressure sensor 38 and the suction temperature sensor 39. The compressor 41 pressurizes and heats the heat pump working fluid, upgrading the low-grade waste heat into high-grade heat energy. After being monitored by the exhaust temperature sensor 42 and purified by the oil separator 43, the high-temperature, high-pressure heat pump working fluid is proportionally distributed to the first condenser 45 and the second condenser 46 by the working fluid distribution valve 44 according to the real-time heat load demand of the anode and cathode.

[0059] Waste heat utilization stage: On the anode side, the first water circuit switch valve 11 is closed, and the first waste heat utilization valve 10 and the second waste heat utilization valve 12 are opened. The circulating water in the anode hydrogen module flows through the second condenser 46 to absorb heat and then flows back to the anode humidification tank 6, providing a heat source for hydrogen bubbling humidification heating. On the cathode side, the second water circuit switch valve 25 is closed, and the third waste heat utilization valve 24 and the fourth waste heat utilization valve 26 are opened. The circulating water in the cathode air module flows through the first condenser 45 to absorb heat and then flows back to the cathode humidification tank 20, providing a heat source for air bubbling humidification heating. The reaction gases are combined through a dry and wet gas flow ratio and then pass through the first heater 4 and the third heater 18 respectively, achieving precise temperature and humidity control.

[0060] Working fluid circulation stage: After the heat is released by the first condenser 45 and the second condenser 46, the working fluids of each heat pump flow into the third condenser 47. The third condenser 47, in conjunction with the operating data collected by the condensing temperature sensor 48 and the condensing pressure sensor 49, stabilizes the pressure and regulates the temperature, and uniformly controls the condensing temperature and subcooling of the working fluid. After being throttled and depressurized by the main expansion valve 50, it flows back to the evaporator 37, completing the heat pump working fluid circulation.

[0061] Heat pump protection control: When the exhaust temperature sensor 42 detects that the exhaust temperature of the compressor 41 is too high, the system automatically opens the liquid injection valve 51 to inject the liquid working fluid from the outlet of the third condenser 47 into the inlet of the gas-liquid separator 40, thereby reducing the intake temperature of the compressor 41 and thus reducing the exhaust temperature; when the suction pressure sensor 38 detects that the suction pressure is too low, the system automatically opens the hot gas bypass valve 52 to bypass the high-temperature and high-pressure working fluid from the outlet of the oil separator 43 to the inlet of the gas-liquid separator 40, thereby increasing the suction pressure and stabilizing the operating conditions.

[0062] Fuel cell stack cooling balance control: Under the condition that the coolant pump 29 operates at a constant speed and the coolant flow rate is constant, the system monitors the inlet and outlet temperatures of the coolant in real time and calculates the temperature difference through the coolant outlet temperature sensor 30 and the coolant inlet temperature sensor 32. When the inlet and outlet temperature difference is greater than the temperature difference threshold (preferably 5°C in this embodiment), it indicates that the heat generated by the fuel cell stack 31 has exceeded the recovery capacity of the evaporator 37 alone, and the heat recovery alone cannot meet the heat dissipation requirements of the fuel cell stack 31. The system then activates the third heat exchanger 33 to assist in forced heat dissipation, ensuring that the fuel cell stack 31 is always in a constant temperature, safe and stable working state.

[0063] The technical solution of this embodiment upgrades the low-grade waste heat that was originally directly discharged in the stack cooling circuit through a heat pump module, and then supplies it to the anode hydrogen module and cathode air module for heating and humidifying the reaction gas. This waste heat recovery replaces the traditional pure electric heating mode, effectively improving the system's energy utilization efficiency and reducing the operating energy consumption and long-term operating costs of the hydrogen fuel cell test bench.

[0064] Example 2: Reference Figure 4 This embodiment provides a waste heat recovery control method for a hydrogen fuel cell test bench, employing the waste heat recovery system for the hydrogen fuel cell test bench in Embodiment 1. The control method includes: S1. Control the condensation temperature of the heat pump working fluid in the heat pump module to be higher than the larger of the target dew point temperatures of the anode hydrogen module and the cathode air module, and control the evaporation temperature of the heat pump working fluid to be lower than the set operating temperature of the fuel cell stack. S2. Obtain the real-time heat load requirements of the anode hydrogen module, the real-time heat load requirements of the cathode air module, and the recoverable waste heat of the coolant in the fuel cell stack cooling module. S3. The difference between the real-time heat load requirement of the anode hydrogen module and the real-time heat load requirement of the cathode air module and the recoverable waste heat is used as the target supplementary heat load of the heat pump module. S4. Control the heat pump module's heat replenishment device to pressurize and heat the heat pump working fluid after absorbing recoverable waste heat according to the target heat replenishment load. S5. Adjust the distribution ratio of the pressurized and heated heat pump working fluid to the anode hydrogen module and the cathode air module according to the ratio of the real-time heat load demand of the anode hydrogen module to the real-time heat load demand of the cathode air module, so that the heat obtained by the anode hydrogen module and the cathode air module matches their own real-time heat load demand.

[0065] The control method of this embodiment will be described in detail below: Specifically, in order to determine the temperature boundary between the high-temperature side and the low-temperature side when the heat pump working fluid cycle is established, the target dew point temperature of the anode is first calculated based on the target temperatures, target relative humidity, and target pressures of the anode and cathode reactant gases. and cathode target dew point temperature Take the larger of the two values. Simultaneously read the set operating temperature of fuel cell stack 31. .

[0066] To ensure that the heat pump working fluid can continuously release heat to the circulating water on the condenser side and continuously absorb heat from the coolant on the evaporator 37 side, this embodiment sets the condensing temperature and evaporating temperature as follows: in, This is the condensation temperature of the heat pump working fluid; The larger of the target dew point temperatures for the anode and cathode; The evaporation temperature of the heat pump working fluid; Set the operating temperature for fuel cell stack 31; and All are preset temperature values. Take 2-5℃, Set the temperature to 5-10℃.

[0067] That is, condensation temperature The temperature is higher than the larger of the target dew point temperatures on both sides, ensuring that even on the side with the higher dew point requirement, the heat pump working fluid in the condenser still has a positive heat exchange temperature difference relative to its circulating water; evaporation temperature The operating temperature is kept below the set operating temperature of the fuel cell stack to ensure that the heat pump working fluid in the evaporator 37 has a positive heat absorption temperature difference relative to the coolant, so as to maximize the recovery of low-grade waste heat.

[0068] Specifically, the condensation temperature is regulated by the third condenser 47: the main control unit adjusts the flow rate (i.e., cooling capacity) of the cooling medium in the first cooling circuit connected to the third condenser 47 based on the measured feedback from the condensation temperature sensor 48 and the condensation pressure sensor 49, thereby stabilizing the condensation temperature of the heat pump working fluid. This ensures the required subcooling; the water sides of the first condenser 45 and the second condenser 46 are responsible for releasing heat to the cathode and anode circulating water as needed according to step S5. The evaporation temperature... Controlled by the main expansion valve 50: The main control unit adjusts the throttling opening of the main expansion valve 50 to stably control the evaporation temperature. It is monitored by inhalation temperature sensor 39 and inhalation pressure sensor 38.

[0069] Specifically, the real-time heat load requirements of the anode hydrogen module and the cathode air module are calculated in real time based on their respective target operating parameters and the stack loading current. The recoverable waste heat is calculated based on the measured temperature and flow rate of the stack cooling circuit.

[0070] In this embodiment, unless otherwise specified, all physical quantities in the calculation formulas use uniform units: temperature is in degrees Celsius (°C), pressure is in kilopascals (kPa), mass flow rate is in kilograms per second (kg / s), and volumetric flow rate is in cubic meters per second (m³ / s). The compressor's displacement per revolution is calculated in cubic meters per revolution (m³ / s). Rotational speed is measured in revolutions per minute (r / min), and density is measured in kilograms per cubic meter (kg / m³). Specific enthalpy and compression work per unit mass are expressed in kJ / kg (based on dry gas and heat pump working fluid, respectively), moisture content in kilograms of dry gas (kg / kg dry gas), specific heat capacity at constant pressure in kJ / (kg·K) Kelvin, heat load and power in kilowatts (kW), molar mass in kilograms of moles (kg / mol); relative humidity, excess ratio, isentropic efficiency, volumetric efficiency and margin coefficient are all dimensionless quantities.

[0071] Furthermore, the real-time heat load requirement of the anode hydrogen module is calculated as follows: First, the target dew point temperature and the specific enthalpy and moisture content of wet hydrogen under the target anode operating conditions are determined. Then, the total inlet mass flow rate of dry hydrogen is determined by the stack loading current (the enthalpy of wet hydrogen is based on a unit mass of dry hydrogen). The specific enthalpy, moisture content, and saturated vapor pressure of water are expressed as follows: in, Let be the specific enthalpy calculation function for wet hydrogen gas. For temperature The specific enthalpy of wet hydrogen gas, when It degenerates into the specific enthalpy of dry hydrogen; Temperature of wet hydrogen gas (independent variable of the function); 14.3 is the moisture content of wet hydrogen, which is the mass of water vapor carried by a unit mass of dry hydrogen; 14.3 is the specific heat capacity of dry hydrogen at constant pressure; 1.86 is the specific heat capacity of water vapor at constant pressure; and 2501 is the latent heat of vaporization of water at 0℃. The relative humidity of the anode target; For temperature The saturated vapor pressure of wastewater; The target pressure at the anode; coefficient 9 represents the molar mass ratio of water to hydrogen (18 / 2); 101.325 is the standard atmospheric pressure, which is related to... Use consistent pressure units; in the above empirical formula for saturated vapor pressure Substitute ℃ In kPa, it is suitable for the normal operating temperature range of hydrogen fuel cells.

[0072] The total mass flow rate of dry hydrogen gas entering the anode is determined by the electrochemical equivalence relationship of the hydrogen oxidation reaction, expressed as: in, The total mass flow rate of dry hydrogen gas entering the anode (subscript 3 corresponds to the dry and wet mixed state of the gas, and the enthalpy of wet hydrogen gas is based on the unit mass of dry hydrogen gas). Apply current to the fuel cell stack; This refers to the number of battery cells in a 31-cell fuel cell stack. The hydrogen excess ratio; The molar mass of hydrogen ( kg / mol); is Faraday's constant; denominator 2 is the number of electrons transferred per mole of hydrogen oxidation reaction.

[0073] Read the initial anode inlet temperature measured by hydrogen inlet temperature sensor 2 The hydrogen output from hydrogen source 1 is dry hydrogen with zero moisture content before entering the humidification branch. Therefore, the heat load required to heat and humidify all the anode intake gas from this initial dry hydrogen state to the target dew point temperature and humidity state, i.e., the real-time heat load requirement of the anode, is: in, This refers to the real-time heat load requirement of the anode hydrogen module, which is the total heat required to process the anode intake gas from its initial dry hydrogen state to the target dew point temperature and humidity state (including sensible heat of heating and latent heat of vaporization of water evaporation). The total inlet mass flow rate of dry hydrogen at the anode; The specific enthalpy of wet hydrogen at the target dew point is calculated using the function. Substitution Compared with the target moisture content of the anode get, The target dew point temperature of the anode; The enthalpy of dry hydrogen at the initial intake state, when the hydrogen is not yet humidified and its moisture content is zero, is calculated using the function. Substitution And order To obtain, that is .

[0074] The above calculations are completed by the main control unit (i.e., the host computer controller); the initial intake temperature is provided by the hydrogen intake temperature sensor 2; the flow rates of the drying branch and the humidification branch are measured by the first dry gas mass flow controller 3 and the first humidifying gas mass flow controller 7, respectively; and the target operating parameters are preset by the main control unit.

[0075] Furthermore, the real-time heat load requirement of the cathode air module is calculated as follows: The calculation process on the cathode side is the same as that on the anode side, the only difference being the relationship between the physical property coefficients of moist air and the equivalent of the electrochemical reaction. The specific enthalpy and moisture content of moist air are: The total dry air inlet mass flow rate at the cathode is determined by the electrochemical equivalence of the oxygen reduction reaction: considering that each mole of oxygen transfers 4 mol of electrons, the volume (molar) fraction of oxygen in the air is 0.21, and the air excess ratio, the oxygen molar flow rate is first calculated from the stack loading current and the number of battery cells, and then converted into the dry air mass flow rate. The calculation formula is as follows: in, Let be the function for calculating the specific enthalpy of moist air. For temperature The specific enthalpy of moist air, when It degenerates into the specific enthalpy of dry air; is the temperature of the moist air (the independent variable of the function); 1.005 is the moisture content of moist air, which is the mass of water vapor carried by a unit mass of dry air; 1.86 is the specific heat capacity of dry air at constant pressure; 2501 is the specific heat capacity of water vapor at constant pressure; and 2501 is the latent heat of vaporization of water at 0℃. The relative humidity of the cathode target; For temperature The saturated vapor pressure of wastewater; The target pressure at the cathode is 0.622, which is the molar mass ratio of water to dry air (18 / 29). The total mass flow rate of dry air entering the cathode (subscript 3 corresponds to the dry and wet mixed state of the gas, and the enthalpy of wet air is based on the unit mass of dry air). Apply current to the fuel cell stack; This refers to the number of battery cells. Air excess ratio; The average molar mass of dry air (approximately) kg / mol); is Faraday's constant; denominator 4 is the number of electrons transferred per mole of oxygen in the reduction reaction, and 0.21 is the volume fraction of oxygen in the air.

[0076] The air output from air source 15 is measured as dry air with zero moisture content before entering the humidification branch. The initial temperature of the cathode air intake is then read from the air intake temperature sensor 16. Similarly, by heating and humidifying all the air entering the cathode from the initial dry air state to the target dew point temperature and humidity state, the real-time heat load requirement of the cathode can be obtained: in, This refers to the real-time heat load requirement of the cathode air module, which is the total heat required to process the cathode air from its initial dry air state to the target dew point temperature and humidity state (including sensible heat of heating and latent heat of vaporization of water). This represents the total mass flow rate of the cathode dry air intake. For the specific enthalpy of moist air at the target dew point, according to the calculation function Substitution Moisture content of the cathode target get, The target dew point temperature of the cathode; The enthalpy of dry air at the initial intake state, when the air is not yet humidified and its moisture content is zero, is calculated using the function. Substitution And order To obtain, that is .

[0077] The calculation is performed by the main control unit. The initial intake temperature is provided by the air intake temperature sensor 16. The flow rates of the drying branch and the humidification branch are measured by the second dry gas mass flow controller 17 and the second humidification gas mass flow controller 21, respectively.

[0078] Furthermore, the calculation of the recoverable waste heat of the fuel cell stack coolant is as follows: In waste heat recovery mode, when the coolant flows through the fifth waste heat utilization valve 34 and the sixth waste heat utilization valve 36 into the evaporator 37, and the third heat exchanger 33 is not in operation, all the heat generated by the fuel cell stack 31 and carried away by the coolant is recovered through the evaporator 37, which is approximately equal to the recoverable waste heat of the heat pump working fluid, expressed as: in, This refers to the recoverable waste heat of the coolant; This refers to the specific heat capacity at constant pressure of the coolant. The mass flow rate of the coolant is determined by the flow rate of the coolant pump 29 or its speed-flow characteristic. The coolant outlet temperature of the fuel cell stack is measured by the coolant outlet temperature sensor 30. The temperature at the inlet of the fuel cell coolant is measured by the coolant inlet temperature sensor 32.

[0079] Furthermore, taking the sum of the real-time heat load demands on both sides as the total heating target, and deducting the residual heat already recovered from the coolant by the evaporator 37, the difference is the target supplementary heating load that the supplementary heating device needs to input additionally. : in, To provide supplemental heating load to the target; Waste heat can be recovered from the coolant; The loss margin coefficient is determined according to the system calibration value and is used to cover the heat loss from the heat pump circulation to the environment, the small amount of heat carried away by the cooling side of the third condenser 47 to regulate the condensing temperature and subcooling, the heat loss from the pipeline, and the heat loss caused by insufficient heat exchange efficiency of each heat exchanger.

[0080] To avoid judging supply and demand balance based on a single value and to cover situations where the heating device is still insufficient even at full load, this embodiment further defines two characteristic loads: This represents the minimum operating load for the heat exchange device; This is the maximum operating load of the heat replenishment device (corresponding to the highest allowable operating frequency, determined by the rated capacity of the heat replenishment device).

[0081] The main control unit performs cycle-by-cycle calculations. The actual heat compensation load of the heat compensation device is determined in three cases. : when At that time, take The heat exchanger maintains minimum heat-boosting operation, and excess heat in the coolant is discharged to the third heat exchanger 33 as needed. when When the deficit is within the capacity of the heating device, take... The heat replenishment device is loaded according to the target heat replenishment load; when When the deficit exceeds the maximum capacity of the heating device, take The heat replenishment device is operating at full capacity, with a remaining deficit. (in the formula) (To compensate for the heating shortfall that still exists after the supplementary heating device is at full load) the second heater 13 and the fourth heater 27 are used according to... The proportions are respectively used to supplement the heating of the circulating water at the anode and cathode.

[0082] Therefore, the main control unit determines the actual heat replenishment load of the heat replenishment device on a cycle-by-cycle basis. This serves as the target value for adjusting the operating parameters of the heating device in step S4.

[0083] Furthermore, the heating device is a compressor 41, which is composed of... Determine the target compressor speed, specifically: The actual heat replenishment power of compressor 41 to the heat pump working fluid is equal to the compression work it performs on the delivered heat pump working fluid per unit time. First, the suction state is measured by suction pressure sensor 38 and suction temperature sensor 39 to determine the suction density. Inhalation enthalpy The compression ratio is determined by the evaporation and condensation temperatures determined in step S1, and the isentropic exhaust enthalpy is obtained by isentropically compressing the heat pump working fluid to the condensation pressure. Combined with the isentropic efficiency of the compressor The actual specific compression work per unit mass of working fluid is obtained as follows: in, The actual specific compression work per unit mass of the heat pump working fluid; The isentropic exhaust enthalpy is the enthalpy of the heat pump working fluid when it is isentropically compressed from the suction state to the condensation pressure, and is determined by the evaporation temperature, condensation temperature, and the thermal properties of the working fluid. The inhalation enthalpy is determined by the inhalation state measured by the inhalation pressure sensor 38 and the inhalation temperature sensor 39. This refers to the isentropic efficiency of the compressor.

[0084] The required heat pump working fluid mass flow rate to meet the actual heat replenishment load is: in, To meet the heat pump working fluid mass flow rate required for heat replenishment; This represents the actual supplemental heating load. It represents the actual specific compression work per unit mass of working fluid.

[0085] Assume the compressor's displacement per revolution is Volumetric efficiency is The target speed of the compressor is: in, The target speed of the compressor; This refers to the compressor's displacement per revolution. The density of the working fluid in the intake state is determined by the intake state. This represents the compressor's volumetric efficiency; the coefficient 60 is used to convert mass flow rate in seconds to flow rate in minutes.

[0086] The main control unit provides the target speed of compressor 41 in a feedforward manner. (Operating frequency), the variable frequency drive compressor 41; simultaneously, PID correction is performed on the target speed using suction pressure (suction pressure sensor 38) and condensing temperature (condensing temperature sensor 48) as feedback quantities, and the measured value of exhaust temperature sensor 42 is used as the limiting constraint. The above... , , For compressor inherent or calibrated parameters, the specific enthalpy, density, and saturation pressure of the working fluid are obtained from the thermophysical property charts or property equations of the selected heat pump working fluid. The flow direction of the heat pump working fluid is: evaporator 37 → gas-liquid separator 40 (gas-liquid separation, preventing liquid slugging) → compressor 41 pressurization and heating → oil separator 43 separates lubricating oil and returns oil → working fluid distribution valve 44.

[0087] Preferably, since the first condenser 45 corresponds to the cathode (heat load) ), the second condenser 46 corresponds to the anode (heat load) The main control unit adjusts the opening of the two outlets of the working fluid distribution valve 44 to make the ratio of the working fluid flow to the first condenser 45 and the second condenser 46 be [value missing]. This ensures that the heat output of the two condensers is matched. , The heat pump working fluid heats the circulating water in the cathode air module and anode hydrogen module in the first condenser 45 and the second condenser 46 respectively, and then flows into the third condenser 47 to regulate the condensation temperature and subcooling. After being throttled and depressurized by the main expansion valve 50, it flows back to the evaporator 37 to complete the working fluid cycle.

[0088] Preferably, in this embodiment, the temperature and humidity of the anode reaction gas are controlled by a combination of dry-wet ratio, dew point closed-loop, and mixed gas final temperature closed-loop: Hydrogen from hydrogen source 1 is divided into a drying branch and a humidification branch after passing through hydrogen inlet temperature sensor 2. These branches are measured by the first drying gas mass flow controller 3 and the first humidifying gas mass flow controller 7, respectively. In the humidification branch, hydrogen bubbles through the bottom of the anode humidification tank 6, carrying water vapor, and flows out from the top of the tank. The outlet temperature of the humidified gas is detected by the first humidity temperature sensor 5, and the temperature of the circulating water inside the tank is detected by the first water temperature sensor 8. Based on the principles of mass conservation and moisture conservation, the following is obtained: in, The mass flow rate of dry hydrogen in the anode drying branch (subscript 1 corresponds to the gas drying state) is measured by the first dry gas mass flow controller 3; The mass flow rate of dry hydrogen in the anode humidification branch (subscript 2 corresponds to the gas humidification state, and the mass of water vapor it carries is measured separately by the moisture content meter) is measured by the first humidified gas mass flow controller 7; The total mass flow rate of dry hydrogen gas entering the anode (subscript 3 corresponds to the dry and wet mixed state of the gas). The moisture content of the humidifier at the outlet (state 2) of the anode humidifier tank 6 is determined by the water temperature inside the tank or the moisture temperature at the outlet of the tank based on near saturation. The target moisture content of the anode (state 3) is the moisture content of wet hydrogen gas under the target state.

[0089] Therefore, the two flow paths can be deduced as follows: Based on this, the main control unit sets the output flow rates of the first humid gas mass flow controller 7 and the first dry gas mass flow controller 3 to be respectively... , .

[0090] Furthermore, the moisture temperature at the tank outlet measured by the first moisture temperature sensor 5 is compared with the target dew point temperature at the anode. Comparison: When the moisture temperature at the tank outlet is lower than At that time, the heat supply on the circulating water side is adjusted by PID control (mainly by the second condenser 46, with the second heater 13 as auxiliary heat supply) to raise the temperature of the wet gas at the tank outlet to [amount missing]. When the moisture temperature at the tank outlet meets the requirements, and the water temperature inside the tank measured by the first water temperature sensor 8 is higher than the required temperature... When the temperature reaches 10℃, the first heat exchanger 14 is turned on to cool the circulating water and prevent the gas from overheating and the deionized water in the tank from boiling.

[0091] Furthermore, after the dry hydrogen and humidified hydrogen meet at the junction, they are heated to the target temperature by the first heater 4. The gas is then transported to the anode inlet of the fuel cell stack 31, where the heating power of the first heater 4 ensures the final intake temperature through a closed-loop system.

[0092] Preferably, the cathode side and the anode side have a symmetrical structure, and their regulation is the same: In the waste heat recovery state, the second water circuit switch valve 25 is closed, and the third waste heat utilization valve 24 and the fourth waste heat utilization valve 26 are opened. The circulating water is driven by the second circulating water pump 23 and returns to the cathode humidification tank 20 after absorbing heat in the first condenser 45. The air output from the air source 15 is divided into a drying branch and a humidification branch after passing through the air intake temperature sensor 16. The air is measured by the second drying gas mass flow controller 17 and the second humidifying gas mass flow controller 21, respectively. The humidified air is bubbled through the cathode humidification tank 20 and detected by the second humidity temperature sensor 19. The water temperature inside the tank is detected by the second water temperature sensor 22. Similarly, the flow rates of the two cathode circuits are deduced. , The dew point closed-loop system primarily uses the first condenser 45 for heating, supplemented by the fourth heater 27. The water temperature inside the tank is higher than the target dew point temperature at the cathode. When the temperature reaches 10°C, the second heat exchanger 28 is activated to dissipate heat; after the dry and humid air merges, it is heated to the target temperature in a closed loop by the third heater 18. It is transported to the cathode inlet of fuel cell stack 31.

[0093] Preferably, the control method in this embodiment further includes steady-state adjustment and safety protection of the heat pump module: Firstly, the compressor 41 operates at a variable frequency, and works in conjunction with the suction pressure sensor 38 and the suction temperature sensor 39 to control the suction pressure of the closed-loop system and maintain the stability of the heat pump's basic operating conditions. Secondly, when the exhaust temperature sensor 42 detects that the exhaust temperature of the compressor 41 is too high, the liquid injection valve 51 is opened to throttle the high-pressure liquid working fluid at the outlet of the third condenser 47 and inject it into the inlet of the gas-liquid separator 40, thereby reducing the intake temperature of the compressor 41 and suppressing the exhaust temperature to prevent the compressor 41 from being damaged by high temperature. Third, when the suction pressure sensor 38 detects that the suction pressure is too low, the hot gas bypass valve 52 is opened to bypass the high-temperature and high-pressure heat pump working fluid at the outlet of the oil separator 43 to the inlet of the gas-liquid separator 40, thereby increasing the suction pressure and preventing the evaporation temperature from dropping below the freezing point, which could cause the coolant in the evaporator 37 to freeze, become blocked, or crack. At the same time, it prevents the compressor 41 from triggering the low-pressure protection shutdown.

[0094] Preferably, the control method in this embodiment also ensures the heat dissipation safety of the fuel cell stack by opening and closing the third heat exchanger 33, specifically: In this embodiment, the coolant pump 29 operates at a constant speed, and the mass flow rate of the coolant in the coolant circuit remains constant. From the thermal balance relationship of the fuel cell stack 31, it can be seen that the heat carried away by the coolant is equal to the product of the coolant mass flow rate, the specific heat capacity at constant pressure, and the inlet and outlet temperature difference. Under the condition of constant mass flow rate, the inlet and outlet temperature difference of the coolant is proportional to the heat load per unit flow rate of the fuel cell stack 31; a larger temperature difference indicates that more heat needs to be carried away per unit mass of coolant.

[0095] The main control unit calculates the temperature difference between the inlet and outlet of the fuel cell coolant in real time through the coolant outlet temperature sensor 30 and the coolant inlet temperature sensor 32. When the temperature difference is greater than the temperature difference threshold (the temperature difference threshold is calibrated according to the allowable temperature rise of the fuel cell and the recovery capacity of the heat pump module, and is taken as 5°C in this embodiment), it is determined that the current heat generation of the fuel cell 31 has exceeded the upper limit that the evaporator 37 can handle alone, and the heat recovery alone cannot meet the heat dissipation needs of the fuel cell 31. At this time, the second cooling circuit connected to the third heat exchanger 33 is turned on, and the third heat exchanger 33 assists in the forced heat dissipation of the coolant to share the excess heat that the evaporator 37 has failed to recover. When the temperature difference between the inlet and outlet falls below the temperature difference threshold, the third heat exchanger 33 is turned off, so that the waste heat is recovered first through the evaporator 37, thereby taking into account both the constant temperature safety of the fuel cell 31 and the waste heat recovery efficiency.

[0096] Furthermore, steps S1 to S5 in this embodiment are executed cyclically according to a set control cycle: The stack loading current is reread each cycle. Recalculate based on the measured values ​​of each sensor. , , Target supplemental heating load Compared with actual heat replenishment load The working parameters of the heat recovery device, the distribution ratio of the working fluid distribution valve 44, and the control targets of the condensing temperature and evaporation temperature are updated to achieve real-time matching of waste heat recovery under all test conditions such as steady-state power generation and dynamic load change.

[0097] The control method in this embodiment mainly uses the recovery of waste heat from the fuel cell stack, supplemented by the on-demand heating device, which replaces the pure electric heating method of heating and humidifying the reaction gas. Under all test conditions, it significantly reduces the energy consumption of the test bench and ensures accurate and stable control of the inlet air temperature and humidity and the fuel cell stack operating temperature.

[0098] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A waste heat recovery system for a hydrogen fuel cell test bench, characterized in that, It includes an anode hydrogen module, a cathode air module, a heat pump module, and a fuel cell stack cooling module, wherein the heat pump module is connected to the anode hydrogen module, the cathode air module, and the fuel cell stack cooling module simultaneously; The heat pump module exchanges heat with the fuel cell stack cooling module to absorb the waste heat of the coolant in the fuel cell stack cooling module. Both the anode hydrogen module and the cathode air module exchange heat with the heat pump module to increase the temperature of their own circulating water. The heat pump module includes a heat replenishment device, which is used to pressurize and heat up the heat pump working fluid after it has absorbed waste heat in the heat pump module.

2. The waste heat recovery system for a hydrogen fuel cell test bench according to claim 1, characterized in that, The heat pump module also includes an evaporator (37), a gas-liquid separator (40), an oil separator (43), a working fluid distribution valve (44), a first condenser (45), a second condenser (46), a third condenser (47), and a main expansion valve (50). The evaporator (37), gas-liquid separator (40), heat replenishment device, oil separator (43), and working fluid distribution valve (44) are connected in series. The two outlets of the working fluid distribution valve (44) are connected to the inlets of the first condenser (45) and the second condenser (46), respectively. The outlets of the first condenser (45) and the second condenser (46) are both connected to the inlet of the third condenser (47). The outlet of the third condenser (47) is connected to the inlet of the evaporator (37) through the main expansion valve (50), forming a heat pump working fluid circulation loop. The evaporator (37) exchanges heat with the fuel cell stack cooling module, the first condenser (45) exchanges heat with the cathode air module, and the second condenser (46) exchanges heat with the anode hydrogen module.

3. The waste heat recovery system for a hydrogen fuel cell test bench according to claim 2, characterized in that, The heat pump module also includes a liquid injection valve (51) and a hot gas bypass valve (52). The inlet of the injection valve (51) is connected to the outlet of the third condenser (47), and the outlet of the injection valve (51) is connected to the inlet of the gas-liquid separator (40). The inlet of the hot gas bypass valve (52) is connected to the outlet of the oil separator (43), and the outlet of the hot gas bypass valve (52) is connected to the inlet of the gas-liquid separator (40).

4. The waste heat recovery system for a hydrogen fuel cell test bench according to claim 3, characterized in that, The heat pump module also includes a suction pressure sensor (38), a suction temperature sensor (39), an exhaust temperature sensor (42), a condensation temperature sensor (48), and a condensation pressure sensor (49). The intake pressure sensor (38) and intake temperature sensor (39) are located between the outlet of the gas-liquid separator (40) and the inlet of the heating device; The exhaust temperature sensor (42) is located between the outlet of the heating device and the inlet of the oil separator (43); The condensation temperature sensor (48) and condensation pressure sensor (49) are located at the outlet of the third condenser (47).

5. The waste heat recovery system for a hydrogen fuel cell test bench according to claim 2, characterized in that, The anode hydrogen module includes a hydrogen heating and humidification circulation loop, which includes an anode humidification tank (6), a first circulating water pump (9), a first water circuit switch valve (11), a second heater (13), and a first heat exchanger (14) connected in series to form the loop. The water-side inlet of the second condenser (46) is connected to the inlet side of the first water circuit switch valve (11) through the first waste heat utilization valve (10), and the water-side outlet of the second condenser (46) is connected to the outlet side of the first water circuit switch valve (11) through the second waste heat utilization valve (12).

6. The waste heat recovery system for a hydrogen fuel cell test bench according to claim 2, characterized in that, The cathode air module includes an air heating and humidification circulation loop, which includes a cathode humidification tank (20), a second circulating water pump (23), a second water circuit switch valve (25), a fourth heater (27), and a second heat exchanger (28) connected in series to form a loop. The water-side inlet of the first condenser (45) is connected to the inlet side of the second water circuit switch valve (25) through the third waste heat utilization valve (24), and the water-side outlet of the first condenser (45) is connected to the outlet side of the second water circuit switch valve (25) through the fourth waste heat utilization valve (26).

7. The waste heat recovery system for a hydrogen fuel cell test bench according to claim 2, characterized in that, The fuel cell stack cooling module includes a fuel cell stack (31) connected in series to form a circuit, a coolant pump (29), a coolant switching valve (35), and a third heat exchanger (33). The coolant side inlet of the evaporator (37) is connected to the inlet side of the coolant switch valve (35) through the sixth waste heat utilization valve (36), and the coolant side outlet of the evaporator (37) is connected to the outlet side of the coolant switch valve (35) through the fifth waste heat utilization valve (34).

8. The waste heat recovery system for a hydrogen fuel cell test bench according to claim 7, characterized in that, The fuel cell stack (31) is equipped with a coolant outlet temperature sensor (30) at the coolant outlet and a coolant inlet temperature sensor (32) at the coolant inlet.

9. A waste heat recovery control method for a hydrogen fuel cell test bench, characterized in that, The waste heat recovery system for the hydrogen fuel cell test bench as described in any one of claims 1-8 includes: The condensation temperature of the heat pump working fluid in the heat pump module is controlled to be higher than the larger of the target dew point temperatures of the anode hydrogen module and the cathode air module, and the evaporation temperature of the heat pump working fluid is controlled to be lower than the set operating temperature of the fuel cell stack. The real-time heat load requirements of the anode hydrogen module, the real-time heat load requirements of the cathode air module, and the recoverable waste heat of the coolant in the fuel cell stack cooling module are obtained. The difference between the sum of the real-time heat load requirements of the anode hydrogen module and the real-time heat load requirements of the cathode air module and the recoverable waste heat is taken as the target supplementary heat load of the heat pump module. The heat pump module's heat replenishment device pressurizes and heats the heat pump working fluid after absorbing recoverable waste heat according to the target heat replenishment load. Based on the ratio of the real-time heat load demand of the anode hydrogen module to the real-time heat load demand of the cathode air module, the distribution ratio of the pressurized and heated heat pump working fluid to the anode hydrogen module and the cathode air module is adjusted so that the heat obtained by the anode hydrogen module and the cathode air module matches their own real-time heat load demand.

10. The waste heat recovery control method for a hydrogen fuel cell test bench according to claim 9, characterized in that, The heat pump working fluid, after absorbing recoverable waste heat, is pressurized and heated according to the target heat replenishment load. Specifically: If the target heating load is less than or equal to the minimum operating load of the heating device, the heating device shall operate at the minimum operating load. If the target heat replenishment load is greater than the minimum operating load of the heat replenishment device and less than or equal to the maximum operating load of the heat replenishment device, then the heat replenishment device shall operate at the target heat replenishment load. If the target heat replenishment load is greater than the maximum operating load of the heat replenishment device, the heat replenishment device will operate at the maximum operating load.

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