Fuel cell thermal management system based on heat pump and phase change heat storage

Abstract

The invention discloses a fuel cell thermal management system based on a heat pump and phase change heat storage. In the system, a first heat exchanger is connected to a fuel cell stack to transfer its heat to the surrounding environment through cooling water in a pipeline. A water pump, a first heat exchanger, a three-way valve and a fuel cell stack pipeline are connected to form a cooling water circulation pipeline. A heater is connected and heats the cooling water in the cooling water circulation pipeline to heat the fuel cell stack. A second heat exchanger is connected in parallel to both ends of a heat storage device and a first proportional valve. One end of the second heat exchanger is connected to the heater and the other end is connected to the three-way valve. By adjusting the three-way valve, the heat storage device stores the excess heat generated by the fuel cell stack or releases the heat when the system needs heat. A heat pump module provides heat to the second heat exchanger and / or the fuel cell stack and the cab in a low temperature environment. The system power consumption is reduced and the energy-saving efficiency of the system is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell thermal management, and in particular to a fuel cell thermal management system based on a heat pump and phase change heat storage. Background Art

[0002] Hydrogen fuel cells are energy conversion devices that use hydrogen and air to undergo an electrochemical reaction to convert the chemical energy of hydrogen into electrical energy. They have the advantages of high energy conversion efficiency, low-temperature operation, low noise pollution, and zero emissions, and are very suitable for the transportation field, such as vehicles, ships, and airplanes. The widespread use of hydrogen fuel cells can reduce carbon dioxide emissions.

[0003] The thermal management system of hydrogen fuel cells is to solve the problem that the large amount of waste heat generated by the fuel cell stack during operation causes the temperature of the stack to rise, exceeding its suitable operating temperature range (60-80°C). At the same time, when the fuel cell is started in a low-temperature environment, the thermal management system can promote the heating rate of the stack, so that the cold start of the fuel cell stack is successful. In order to achieve the function of quickly heating the stack, the prior art is to install a PTC electric heater in the thermal management system to heat the cooling water flowing through the fuel cell stack, and further heat the stack through the cooling water. The PTC electric heater is a component with high power consumption. During the startup phase of the fuel cell stack in a low-temperature environment, a large amount of power in the system will be consumed while heating the cooling water, thereby reducing the net output power consumption of the system. In addition, in a low-temperature environment, there is also a heat load demand to heat the air in the cab, and a PTC electric heater is usually used as the only heat source. The use of PTC in the system causes the system to have very high power consumption in a low-temperature environment, reducing the system efficiency. Therefore, developing a high-efficiency method to replace the method of using a PTC heater to heat the stack and the cab in a low-temperature environment can effectively improve the energy-saving efficiency of the system, which is of great significance to the operation of the system in a low-temperature environment.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention proposes a fuel cell thermal management system based on a heat pump and phase change heat storage, which can reduce the power loss of the system and improve the energy-saving efficiency of the system.

[0006] The purpose of the present invention is to achieve the following technical solution: a fuel cell thermal management system based on a heat pump and phase change heat storage comprises:

[0007] Fuel cell stack;

[0008] A main heat dissipation module, which is configured to dissipate heat from the fuel cell stack, the main heat dissipation module comprising:

[0009] A first heat exchanger connected to the fuel cell stack to transfer its heat to the surrounding environment through cooling water in the pipeline,

[0010] a water pump, whose pipeline is connected between the fuel cell stack and the first heat exchanger and pumps cooling water,

[0011] A three-way valve, a first end pipeline of which is connected to the fuel cell stack, and a second end pipeline of which is connected to the first heat exchanger,

[0012] The water pump, the first heat exchanger, the three-way valve and the fuel cell stack pipeline are connected to form a cooling water circulation pipeline.

[0013] a heater connected to and heating the cooling water in the cooling water circulation pipeline to heat the fuel cell stack;

[0014] An auxiliary module, which is configured to start the fuel cell stack in a low temperature environment, the auxiliary module comprising:

[0015] A heat storage device connected to the heater, wherein the heat storage device is filled with a phase change material.

[0016] A first proportional valve, one end of which is connected to the heat storage device, and the other end of which is connected to the third end of the three-way valve,

[0017] A second heat exchanger is connected in parallel to both ends of the heat storage device and the first proportional valve, one end of the second heat exchanger is connected to the heater, and the other end is connected to the third end of the three-way valve. By adjusting the three-way valve, the heat storage device stores excess heat generated by the fuel cell stack or releases heat when the system needs heat;

[0018] A heat pump module, which provides heat to the second heat exchanger and / or the fuel cell stack and the cab in a low temperature environment, the heat pump module comprising:

[0019] a first solenoid valve connected to the second heat exchanger,

[0020] a first expansion valve connected to the first solenoid valve,

[0021] A third heat exchanger is connected to the first expansion valve, and the third heat exchanger is used to exchange heat with the air of the external environment.

[0022] A four-way reversing valve is connected to the third heat exchanger,

[0023] A first working fluid pump is connected to the four-way reversing valve.

[0024] a fourth heat exchanger connected to the four-way reversing valve, wherein the fourth heat exchanger exchanges heat with the air in the cab,

[0025] A second proportional valve is connected to the four-way reversing valve.

[0026] a one-way valve, one end of which is connected to the second proportional valve and the other end of which is connected to the second heat exchanger,

[0027] A third solenoid valve has one end connected to the fourth heat exchanger and the other end connected to the first expansion valve.

[0028] In the fuel cell thermal management system based on heat pump and phase change heat storage, the heat pump module further includes:

[0029] a second solenoid valve connected to the second heat exchanger,

[0030] a second expansion valve, one end of which is connected to the second solenoid valve, and the other end of which is connected to the fourth heat exchanger,

[0031] a fourth solenoid valve connected to the fourth heat exchanger,

[0032] The second working fluid pump has one end connected to the fourth solenoid valve and the other end connected to the first solenoid valve.

[0033] In the fuel cell thermal management system based on heat pump and phase change heat storage, the first solenoid valve, the second solenoid valve and the fourth solenoid valve are normally closed solenoid valves, and the third solenoid valve is a normally open solenoid valve.

[0034] In the fuel cell thermal management system based on heat pump and phase change heat storage, the heat storage device is equipped with a temperature sensor for measuring the temperature value of the phase change material, and the current stored energy value of the heat storage device is determined by setting the low temperature value Tl and the high temperature value Th.

[0035] In the fuel cell thermal management system based on heat pump and phase change heat storage, the phase change material is stearic acid or a combination of stearic acid and expanded graphite.

[0036] In the fuel cell thermal management system based on heat pump and phase change heat storage, in the low-temperature environment startup mode, the main heat dissipation module and the auxiliary module work, the main heat dissipation module heats the cooling water in the pipeline, and increases the temperature of the fuel cell stack through the cooling water. At the same time, the air temperature in the cab is increased through the fourth heat exchanger, and it is determined whether the current temperature T of the heat storage device is lower than the low temperature value Tl. If T is greater than the low temperature value Tl, the heat storage device is preferentially used to heat the cooling water in the pipeline, and the second heat exchanger obtains heat from the heat pump module and heats the cooling water in the pipeline at the same time; if T is less than the low temperature value Tl, all the cooling water is heated by absorbing the heat transferred by the working fluid of the heat pump module through the second heat exchanger.

[0037] In the fuel cell thermal management system based on heat pump and phase change heat storage, when the heat storage device and the second heat exchanger cannot meet the heating rate requirement of the fuel cell stack, the heater is turned on to further heat the cooling water and the first heat exchanger does not work. The working fluid in the heat pump module evaporates into a gaseous state in the third heat exchanger, absorbs the heat of the ambient air, and is further pressurized and heated by the four-way reversing valve and the first working fluid pump. The high-temperature and high-pressure working fluid flows into the fourth heat exchanger for condensation, transfers the heat to the cab, and is then throttled to a low-temperature and low-pressure state through the third solenoid valve and the first expansion valve; when the heat pump module is needed to supply heat to the auxiliary module, the first solenoid valve is opened, and the working fluid pressurized and heated by the first working fluid pump will be divided into a path through the second proportional valve and the one-way valve to enter the second heat exchanger to heat the cooling water. After the cooled working fluid passes through the first solenoid valve, it is throttled to a low-temperature and low-pressure state by the first expansion valve and enters the third heat exchanger.

[0038] In the fuel cell thermal management system based on heat pump and phase change heat storage, in the low-temperature environment operation mode, the heat generated by the fuel cell stack during operation is transferred to the environment through the main heat dissipation module, the first heat exchanger works, the heater does not work, the cooling water flows through the fuel cell stack and is heated, and then flows through the first heat exchanger to cool down, dissipating the heat generated by the fuel cell stack into the surrounding environment.

[0039] In the fuel cell thermal management system based on heat pump and phase change heat storage, it is determined whether the current temperature T of the heat storage device is lower than the high temperature value Th. If T is less than the high temperature value Th, high-temperature cooling water flows through the heat storage device to heat the internal phase change material, so that the energy stored in the heat storage device is sufficient, until the current temperature T exceeds the high temperature value Th, the first proportional valve is adjusted so that the cooling water does not flow through the heat storage device. At the same time, the cooling water flows through the second heat exchanger for heat transfer to achieve heating of the cab. The second solenoid valve and the fourth solenoid valve are opened, and the first solenoid valve and the third solenoid valve are in a closed state. The heated working fluid after flowing through the second heat exchanger enters the fourth heat exchanger after throttling through the second solenoid valve and the second proportional valve, and heats the air in the cab. The cooled working fluid re-enters the second heat exchanger through the fourth solenoid valve and the second working fluid pump to obtain heat.

[0040] In the fuel cell thermal management system based on heat pump and phase change heat storage, in the normal temperature operation mode, the heat generated by the fuel cell stack is transferred to the surrounding environment through the main heat dissipation module, the first heat exchanger works, and the cooling water carrying the heat of the fuel cell stack flows through the first heat exchanger to transfer the heat to the environment. At the same time, the cooling water temperature is reduced, and the cooling water cannot flow into the auxiliary module by adjusting the three-way valve. When the cab needs to be cooled, the heat pump module is operated, and the four-way reversing valve is adjusted to make the working fluid flow to the third heat exchanger. The working fluid absorbs the heat of the cab environment through the fourth heat exchanger, so that the air temperature of the cab is reduced. After that, it is pressurized and heated by the four-way reversing valve and the first working fluid pump, and then flows into the third heat exchanger to transfer the heat to the external environment. The cooled working fluid is throttled and cooled by the first expansion valve, and then flows into the fourth heat exchanger through the third solenoid valve to realize circulation.

[0041] Compared with the prior art, the present invention has the following advantages: the fuel cell thermal management system based on heat pump and phase change heat storage described in the present invention uses a phase change heat storage device to store the waste heat of the previous fuel cell stack, so that the system preferentially uses the energy of the heat storage device when starting in a low-temperature environment, rather than using the high-energy-consuming PTC heater in the prior art, saving the system's power consumption at this stage. When the heat storage device stores insufficient energy, part of the working fluid introduced into the heat pump module indirectly heats the fuel cell stack, which only consumes a small amount of working fluid pump power, which is much lower than directly using the PTC heater. The energy-saving efficiency of the system can be significantly improved during the startup phase. During the system operation phase in a low-temperature environment, the waste heat of the fuel cell stack is used to meet the heat load requirements of the cab. Compared with the use of electric heaters or heat pump modules, this method also requires very little pump power loss, significantly reduces the system's power consumption loss during the system operation phase, and improves the system's energy-saving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used throughout the drawings to represent the same components.

[0043] In the attached picture:

[0044] Figure 1 is a schematic structural diagram of a fuel cell thermal management system based on a heat pump and phase change heat storage according to an embodiment of the present invention;

[0045] The symbols in the accompanying drawings are explained as follows:

[0046] 1- fuel cell stack; 2- water pump; 3- heater; 4- first heat exchanger; 5- heat storage; 6- second heat exchanger; 7- first proportional valve; 8- three-way valve; 9- second solenoid valve; 10- first solenoid valve; 11- first expansion valve; 12- third heat exchanger; 13- four-way reversing valve; 14- first working fluid pump; 15- second expansion valve; 16- fourth heat exchanger; 17- second proportional valve; 18- one-way valve; 19- third solenoid valve; 20- fourth solenoid valve; 21- second working fluid pump.

[0047] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0048] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0049] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0050] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0051] For a better understanding, Figure 1 As shown, the fuel cell thermal management system based on heat pump and phase change heat storage includes: a fuel cell stack 1, a main heat dissipation module, an auxiliary module and a heat pump module, wherein:

[0052] The main heat dissipation module includes a water pump 2, a heater 3 and a first heat exchanger 4; the auxiliary module includes a heat storage 5, a first proportional valve 7, a second heat exchanger 6 and a three-way valve 8. The first heat exchanger 4 is used to transfer the heat generated by the fuel cell stack 1 to the surrounding environment through the cooling water in the pipeline; the heater 3 heats the stack by heating the cooling water in the pipeline, which is used for starting the system in a low temperature environment; the three-way valve 8 is used for the system to control whether to turn on the auxiliary module; the heat storage 5 is used to store the excess heat generated by the fuel cell stack 1, and release the heat for use when the system needs heat; the second heat exchanger 6 is used for heat exchange between the auxiliary module and the heat pump module.

[0053] Preferably, the heat reservoir 5 is filled with phase change material, which may be stearic acid (SA), stearic acid / expanded graphite (SA / EG), etc. The heat reservoir 5 is equipped with a temperature sensor to measure the temperature value of the phase change material, and the low temperature value T1 and the high temperature value Th are set to determine the current storage energy value of the heat reservoir 5.

[0054] Preferably, the heater 3 is turned on during the system low-temperature environment startup phase, if the auxiliary module and the heat pump module cannot work, and if the auxiliary module and the heat pump module can work normally, the heater 3 does not need to work.

[0055] The heat pump module includes a first solenoid valve 10, a first expansion valve 11, a third heat exchanger 12, a four-way reversing valve 13, a first working fluid pump 14, a fourth heat exchanger 16, a second proportional valve 17, a one-way valve 18 and a third solenoid valve 19. The third heat exchanger 12 is used to exchange heat with the air of the external environment; the fourth heat exchanger 16 is used to exchange heat with the air in the cab; the four-way reversing valve 13 is used to change the flow direction of the working fluid after being pressurized by the first working fluid pump 14.

[0056] The heat pump module further includes a second solenoid valve 9 , a second expansion valve 15 , a fourth solenoid valve 20 , and a second working fluid pump 21 .

[0057] Preferably, the first solenoid valve 10, the second solenoid valve 9, and the fourth solenoid valve 20 are normally closed solenoid valves, and the third solenoid valve 19 is a normally open solenoid valve.

[0058] Preferably, the one-way valve 18 is used to prevent the working fluid pressurized by the second working fluid pump 21 from flowing back through the second proportional valve 17 , thereby ensuring that it can only flow into the second heat exchanger 6 .

[0059] Furthermore, the present disclosure provides three operating modes of the fuel cell thermal management system: a low temperature environment start-up mode, a low temperature environment operation mode, and a normal temperature mode.

[0060] The low temperature environment startup mode refers to the stage when the system is ready to start in a low temperature environment. At this time, the main heat dissipation module needs heat to heat the cooling water in the pipeline, and the temperature of the fuel cell stack 1 is increased by the cooling water. At the same time, heat is needed in the cab, and the air temperature in the cab is increased by the fourth heat exchanger 16. For the fuel cell stack 1, the main heat dissipation module and the auxiliary module work. First, it is determined whether the current temperature T of the heat storage 5 is lower than Tl. If T is greater than Tl, it means that the heat storage 5 still stores heat, and the heat storage 5 is used to heat the cooling water in the pipeline first. At the same time, the second heat exchanger 6 obtains heat from the heat pump module and heats the cooling water in the pipeline; if T is less than Tl, it means that the heat storage 5 has no available energy storage energy, and the cooling water is all heated by absorbing the heat transferred by the working fluid of the heat pump module through the second heat exchanger 6. When both the heat storage 5 and the second heat exchanger 6 cannot meet the heating rate requirements of the fuel cell stack 1, the heater 3 will be turned on to further heat the cooling water. It should be noted that at this stage, the first heat exchanger 4 does not work. In response to the heat demand of the cab, the working fluid in the heat pump module evaporates into a gaseous state in the third heat exchanger 12, absorbs the heat of the ambient air, and after further pressurizing and heating through the four-way reversing valve 13 and the first working fluid pump 14, the high-temperature and high-pressure working fluid flows into the fourth heat exchanger 16 for condensation, transfers the heat to the cab, and then is throttled to a low-temperature and low-pressure state through the third solenoid valve 19 and the first expansion valve 11. When the heat pump module is required to supply heat to the auxiliary module, the first solenoid valve 10 is opened, and the working fluid that has been pressurized and heated by the first working fluid pump 14 will be divided into one path and pass through the second proportional valve 17 and the one-way valve 18 to enter the second heat exchanger 6 to heat the cooling water. After the working fluid has been cooled, it passes through the first solenoid valve 10 and also flows through the first expansion valve 11 to be throttled to a low-temperature and low-pressure state and enters the third heat exchanger 12.

[0061] The low-temperature environment operation mode refers to the normal operation stage of the system in a low-temperature environment. At this time, only the cab in the system needs heat. The fuel cell stack 1 generates a large amount of heat during operation, which needs to be transferred to the environment through the main heat dissipation module. In the main heat dissipation module, the first heat exchanger 4 works, the heater 3 does not work, the cooling water flows through the fuel cell stack 1 and is heated, and then flows through the first heat exchanger 4 to cool down, dissipating the heat generated by the fuel cell stack 1 into the surrounding environment. In the auxiliary module, it is determined whether the current temperature T of the heat storage 5 is lower than Th. If T is less than Th, the high-temperature cooling water flows through the heat storage 5 to fully heat the internal phase change material, so that the energy stored in the heat storage 5 is sufficient, until the current temperature T exceeds Th, and the first proportional valve 7 is adjusted so that the cooling water does not flow through the heat storage 5. At the same time, the cooling water will flow through the second heat exchanger 6 for heat transfer to achieve heating of the cab. In the heat pump module, the second solenoid valve 9 and the fourth solenoid valve 20 are open, the first solenoid valve 10 and the third solenoid valve 19 are closed, and the heated working fluid flowing through the second heat exchanger 6 enters the fourth heat exchanger 16 after throttling through the second solenoid valve 9 and the second proportional valve 17 to heat the air in the cab, and the cooled working fluid re-enters the second heat exchanger 6 through the fourth solenoid valve 20 and the second working fluid pump 21 to obtain heat. It should be noted that in the current mode, except for the above-mentioned components, other components in the heat pump module do not work.

[0062] Normal temperature operation mode refers to the stage when the system is running at normal ambient temperature. At this time, the system does not need heat demand. The heat generated by the fuel cell stack 1 is transferred to the surrounding environment through the main heat dissipation module. When the ambient temperature is high, the heat pump module is also needed to cool the cab. In the main heat dissipation module, the first heat exchanger 4 works, and the cooling water carrying the heat of the fuel cell stack 1 flows through the first heat exchanger 4, transferring the heat to the environment, and the cooling water temperature is reduced. In this mode, the auxiliary module does not operate, and the cooling water cannot flow into the auxiliary module by adjusting the three-way valve 8. When the cab needs to be cooled, the heat pump module operates and adjusts the four-way reversing valve 13 so that the working fluid flows to the third heat exchanger 12. The working fluid absorbs the heat of the cab environment through the fourth heat exchanger 16, so that the air temperature of the cab is reduced. After that, it is pressurized and heated by the four-way reversing valve 13 and the first working fluid pump 14, and then flows into the third heat exchanger 12 to transfer the heat to the external environment. After the cooled working fluid is throttled and cooled by the first expansion valve 11, it flows into the fourth heat exchanger 16 through the third solenoid valve 19 to realize circulation. When the cab does not need to be cooled, the heat pump module does not operate and all components in the heat pump module do not work.

[0063] The above embodiments constitute a complete technical solution of the present disclosure. The main advantage of the present disclosure is that when the system has a heat load demand in a low-temperature environment, heat pump technology and phase change heat storage are used to provide heat, replacing the existing technology that only relies on high-energy-consuming electric heating to provide heat. By using the present disclosure, the system can significantly improve the energy-saving efficiency of the system in a low-temperature environment.

[0064] In order to further understand the advantages of the present disclosure, the present disclosure provides another specific embodiment. First, in a low temperature environment (-30°C), it is assumed that the heat load demand of the fuel cell stack 1 in the startup phase is 10kW, and the heat load demand of the cab is 3kW. If the prior art is used, the power consumption required in the low temperature environment is 13kW. If the present disclosure is used, in the startup phase, when the heat storage 5 cannot output heat, that is, the current temperature T of the heat storage 5 is lower than Tl, considering the heat loss of the system, the system heat load margin is set to 30%, that is, the heat exchange power of the second heat exchanger 6 is 13kW, which meets the heat load demand of the fuel cell stack 1, and the heat exchange power of the fourth heat exchanger 16 is 3.9kW, which meets the heat load demand of the cab, and it is assumed that the temperature of the heat pump working fluid in the second heat exchanger 6 and the fourth heat exchanger 16 is 20°C. The isentropic efficiency of the first working fluid pump 14 is 0.7, the mechanical efficiency is 0.8, the heat pump working fluid is R134a, and the working fluid flow rate in the heat pump module is 76g / s. Under the above requirements, the power consumption of the first working fluid pump 14 is calculated to be 6.635kW. Compared with the use of electric heating to meet the system heat load (13kW), the energy saving efficiency of the present disclosure is 48.962%. In the startup phase, when the heat storage 5 can provide heat for the fuel cell stack 1, the heat pump module only needs to provide heat load to the fourth heat exchanger 16, and the working fluid flow rate in the heat pump module is 18g / s. The power consumption of the first working fluid pump 14 is calculated to be 1.571kW. Compared with the use of electric heating to meet the system heat load (13kW), the energy saving efficiency of the present disclosure is 87.915%. When the system is in the normal operation stage of a low temperature environment, only the cab in the system needs a heat load demand (3kW). At this time, the excess heat generated by the fuel cell stack 1 can be utilized through the second heat exchanger 6. The working fluid temperature in the second heat exchanger 6 is 80°C, the working fluid is still R134a, and the working fluid flow rate is 21.56g / s. At this time, the power consumption of the second working fluid pump 21 is calculated to be 0.03149kW. Compared with using electric heating (3kW) to meet the cab heat load, the energy saving efficiency of the present invention is 98.95%; compared with using heat pump technology (1.571kW) to meet the cab heat load, the energy saving efficiency of the present invention is 97.99%.

[0065] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A fuel cell thermal management system based on heat pump and phase change heat storage, characterized in that: These include, Fuel cell stack; A main heat dissipation module, configured to dissipate heat from the fuel cell stack, the main heat dissipation module comprising: A first heat exchanger connected to the fuel cell stack to transfer its heat to the surrounding environment through cooling water in a pipeline; a water pump, whose pipeline is connected between the fuel cell stack and the first heat exchanger and pumps cooling water; A three-way valve, a first end pipeline of which is connected to the fuel cell stack, and a second end pipeline of which is connected to the first heat exchanger; The water pump, the first heat exchanger, the three-way valve and the fuel cell stack pipeline are connected to form a cooling water circulation pipeline; a heater connected to and heating the cooling water in the cooling water circulation pipeline to heat the fuel cell stack; An auxiliary module, which is configured to start the fuel cell stack in a low temperature environment, and the auxiliary module comprises: A heat storage device connected to the heater, wherein the heat storage device is filled with a phase change material; a first proportional valve, one end of which is connected to the heat reservoir, and the other end of which is connected to the third end of the three-way valve; A second heat exchanger is connected in parallel to both ends of the heat storage device and the first proportional valve, one end of the second heat exchanger is connected to the heater, and the other end is connected to the third end of the three-way valve. By adjusting the three-way valve, the heat storage device stores excess heat generated by the fuel cell stack or releases heat when the system needs heat; A heat pump module, which provides heat to the second heat exchanger and / or the fuel cell stack and the cab in a low temperature environment, the heat pump module comprising; a first solenoid valve connected to the second heat exchanger; a first expansion valve connected to the first solenoid valve; A third heat exchanger connected to the first expansion valve, the third heat exchanger is used to exchange heat with air in an external environment; A four-way reversing valve connected to the third heat exchanger; a first working fluid pump connected to the four-way reversing valve; a fourth heat exchanger connected to the four-way reversing valve, the fourth heat exchanger exchanging heat with the air in the cab; a second proportional valve connected to the four-way reversing valve; a one-way valve, one end of which is connected to the second proportional valve and the other end of which is connected to the second heat exchanger; A third solenoid valve has one end connected to the fourth heat exchanger and the other end connected to the first expansion valve.

2. The fuel cell thermal management system based on heat pump and phase change heat storage according to claim 1 is characterized in that: Preferably, the heat pump module further comprises: a second solenoid valve connected to the second heat exchanger; a second expansion valve, one end of which is connected to the second solenoid valve, and the other end of which is connected to the fourth heat exchanger; a fourth solenoid valve connected to the fourth heat exchanger; The second working fluid pump has one end connected to the fourth solenoid valve and the other end connected to the first solenoid valve.

3. The fuel cell thermal management system based on heat pump and phase change heat storage according to claim 2 is characterized in that: The first solenoid valve, the second solenoid valve and the fourth solenoid valve are normally closed solenoid valves, and the third solenoid valve is a normally open solenoid valve.

4. The fuel cell thermal management system based on heat pump and phase change heat storage according to claim 1, characterized in that: The heat storage device is equipped with a temperature sensor for measuring the temperature value of the phase change material, and the current stored energy value of the heat storage device is determined by setting a low temperature value Tl and a high temperature value Th.

5. The fuel cell thermal management system based on heat pump and phase change heat storage according to claim 1, characterized in that: The phase change material is stearic acid or a combination of stearic acid and expanded graphite.

6. The fuel cell thermal management system based on heat pump and phase change heat storage according to claim 2, characterized in that: In the low-temperature environment startup mode, the main heat dissipation module and the auxiliary module work. The main heat dissipation module heats the cooling water in the pipeline, and increases the temperature of the fuel cell stack through the cooling water. At the same time, the air temperature in the cab is increased through the fourth heat exchanger to determine whether the current temperature T of the heat storage device is lower than the low temperature value Tl. If T is greater than the low temperature value Tl, the heat storage device is preferentially used to heat the cooling water in the pipeline. At the same time, the second heat exchanger obtains heat from the heat pump module and heats the cooling water in the pipeline; if T is less than the low temperature value Tl, all the cooling water is heated by absorbing the heat transferred by the working fluid of the heat pump module through the second heat exchanger.

7. The fuel cell thermal management system based on heat pump and phase change heat storage according to claim 6, characterized in that: When both the heat storage device and the second heat exchanger cannot meet the heating rate requirements of the fuel cell stack, the heater is turned on to further heat the cooling water and the first heat exchanger does not work. The working fluid in the heat pump module evaporates into a gas in the third heat exchanger, absorbs the heat of the ambient air, and is further pressurized and heated by the four-way reversing valve and the first working fluid pump. The high-temperature and high-pressure working fluid flows into the fourth heat exchanger for condensation, transfers the heat to the cab, and is then throttled to a low-temperature and low-pressure state through the third solenoid valve and the first expansion valve. When the heat pump module is needed to supply heat to the auxiliary module, the first solenoid valve is opened, and the working fluid pressurized and heated by the first working fluid pump will be divided into a path through the second proportional valve and the one-way valve to enter the second heat exchanger to heat the cooling water. After the cooled working fluid passes through the first solenoid valve, it is throttled to a low-temperature and low-pressure state by the first expansion valve and enters the third heat exchanger.

8. The fuel cell thermal management system based on heat pump and phase change heat storage according to claim 2, characterized in that: In the low-temperature environment operation mode, the heat generated by the fuel cell stack during operation is transferred to the environment through the main heat dissipation module, the first heat exchanger works, the heater does not work, the cooling water flows through the fuel cell stack and is heated, and then flows through the first heat exchanger to cool down, dissipating the heat generated by the fuel cell stack into the surrounding environment.

9. The fuel cell thermal management system based on heat pump and phase change heat storage according to claim 8, characterized in that: Determine whether the current temperature T of the heat storage device is lower than the high temperature value Th. If T is less than the high temperature value Th, the high-temperature cooling water flows through the heat storage device to heat the internal phase change material, so that the energy stored in the heat storage device is sufficient, until the current temperature T exceeds the high temperature value Th, adjust the first proportional valve so that the cooling water does not flow through the heat storage device. At the same time, the cooling water flows through the second heat exchanger for heat transfer to achieve heating of the cab. The second solenoid valve and the fourth solenoid valve are opened, and the first solenoid valve and the third solenoid valve are closed. The heated working fluid after flowing through the second heat exchanger enters the fourth heat exchanger after throttling through the second solenoid valve and the second proportional valve to heat the air in the cab. The cooled working fluid re-enters the second heat exchanger through the fourth solenoid valve and the second working fluid pump to obtain heat.

10. The fuel cell thermal management system based on heat pump and phase change heat storage according to claim 2, characterized in that: In the normal temperature operation mode, the heat generated by the fuel cell stack is transferred to the surrounding environment through the main heat dissipation module, the first heat exchanger works, and the cooling water carrying the heat of the fuel cell stack flows through the first heat exchanger to transfer the heat to the environment. At the same time, the cooling water temperature is reduced, and the cooling water cannot flow into the auxiliary module by adjusting the three-way valve. When the cab needs to be cooled, the heat pump module runs, and the four-way reversing valve is adjusted to allow the working fluid to flow to the third heat exchanger. The working fluid absorbs the ambient heat of the cab through the fourth heat exchanger, so that the air temperature of the cab is reduced. After that, it is pressurized and heated by the four-way reversing valve and the first working fluid pump, and then flows into the third heat exchanger to transfer the heat to the external environment. The cooled working fluid is throttled and cooled by the first expansion valve, and then flows into the fourth heat exchanger through the third solenoid valve to realize circulation.

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