Fuel cell thermal management system based on loop heat pipe

Abstract

The invention provides a fuel cell thermal management system of a loop heat pipe, and belongs to the technical field of fuel cells. The fuel cell thermal management system of the loop heat pipe comprises a liquid storage tank, a temperature control unit, a first electromagnetic valve, a working medium pump, an evaporator inlet preheater, a fuel cell stack, a second electromagnetic valve, a condenser and a condenser outlet preheater, the temperature control unit is arranged on the liquid storage tank and used for adjusting the temperature of a liquid working medium in the liquid storage tank, and the first electromagnetic valve is arranged on the first electromagnetic valve. The fuel cell stack is provided with a liquid working medium channel, an outlet of the liquid storage tank is connected with the evaporator inlet preheater through a first electromagnetic valve and then connected with an inlet of the liquid working medium channel, an outlet of the liquid working medium channel is connected with an inlet of the condenser through a second electromagnetic valve, and an outlet of the condenser is connected with the condenser outlet preheater and then connected with the condenser outlet preheater. The working medium pump is connected with an inlet of the liquid storage tank and used for providing flowing power of the liquid working medium. The characteristic of high two-phase state heat exchange capacity is ingeniously utilized, and the cooling efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cells, and in particular relates to a fuel cell thermal management system of a loop heat pipe. Background Art

[0002] When a proton exchange membrane fuel cell (PEMFC) is working, the electrochemical reaction between hydrogen and oxygen converts about 50% of chemical energy into electrical energy, and the chemical energy that is not converted into electrical energy is released in the form of heat. In addition, the heat in the PEMFC also includes the Joule heat generated by the resistor and the heat released by the condensation of water vapor. The power density of the PEMFC is closely related to the temperature distribution. If the waste heat cannot be discharged in time, it will seriously affect the performance of the battery and even damage the battery. Therefore, the thermal management of the battery is crucial. During operation, the temperature and distribution of the PEMFC should be controlled within a reasonable range to ensure safety, efficiency and durability. A reasonable thermal management strategy is an effective way to achieve these goals.

[0003] The common cooling method for PEMFC is passive cooling, which usually uses water and different heat pipes to dissipate heat for the fuel cell. For example, flat heat pipes and microchannel heat pipes; among them, loop heat pipes are not restricted by the layout of liquid pipes or steam pipes, have long heat transfer distances, strong heat transfer capacity, can work under different gravity acceleration environments, have no capillary wicks in the liquid infusion pipe, and have two phases of gas and liquid separated without carrying restrictions.

[0004] Invention patent CN117080482A discloses a liquid-cooled fuel cell stack including: a fuel cell stack, an air system, a hydrogen system, a water heat management system, and a tail exhaust pipe system; although this liquid-cooled fuel cell stack can maintain a certain heat dissipation effect, the cooling water temperature will gradually increase along the flow direction, which will lead to uneven temperature of the fuel cell stack; at the same time, the temperature control of the fuel cell stack by this scheme is single and inflexible, and the temperature of the fuel cell stack cannot be controlled to meet the user's requirements for battery temperature control, and cannot cope with complex external environments. For example, when the temperature of the fuel cell is too low, a cold start is required, and the device cannot immediately heat the fuel cell to the optimal temperature of 60-80°C.

[0005] Invention patent CN117080482A discloses a fuel cell system and heat dissipation method using an integral heat pipe. The system includes a plurality of fuel cell units, a plurality of heat pipe groups and a control system; wherein a heat pipe groove is provided between the bipolar plates of each two adjacent fuel cell units, the evaporation end is connected to the heat pipe groove, and the condensation end is left outside the fuel cell unit. Although the integral heat pipe can efficiently exchange heat and ensure the temperature uniformity of the fuel cell, attaching the evaporation end of the heat pipe in the middle of the bipolar plate will multiply the volume of the fuel cell stack.

[0006] The utility model patent CN216084968U discloses an integrated microchannel heat pipe air-cooled fuel cell stack, which is composed of two end plates, a current collecting plate, multiple membrane electrodes and multiple groups of bipolar plates. A micro heat pipe array is bonded between each anode plate 201 and the cathode plate. The part bonded to the anode plate 201 and the cathode plate is the evaporation end of the micro heat pipe array, and the part of the battery stack extending outward is the condensation end of the micro heat pipe array. The evaporation end of the micro heat pipe array can transfer the heat generated by the contact between hydrogen and air through the proton exchange membrane to the condensation end of the micro heat pipe array, and then dissipate heat through natural convection or forced convection by an external fan. Similar to the previous patent CN117080482A, this patent has a micro heat pipe array bonded between each anode plate 201 and the cathode plate, which will double the volume of the fuel cell stack and is not suitable for use in a specific small volume situation; in addition, similar to the previous patent CN117080482A, since the operating temperature of the evaporation end is directly affected by the temperature of the condensation end, this solution cannot flexibly adjust the operating temperature of the fuel cell stack.

[0007] Patent CN116914179A discloses an anti-gravity loop heat pipe air-cooled fuel cell stack and drone, including a fuel cell group installed on the top of the drone's fuselage shell; an anti-gravity heat pipe, including an evaporator, a steam pipeline, a condenser, and a liquid pipeline connected in sequence to form a loop, the evaporator is installed between the fuel cells, and the condenser is located below the evaporator and extends to the outside of the fuselage shell. The system uses the evaporation area to fit tightly inside the fuel cell stack to absorb heat, and the condensation end is exposed to the environment to release heat with the help of a fan. This method requires the evaporation ends of several loop heat pipes to fit inside the fuel cell, and the condensation ends of several loop heat pipes to be exposed to the environment to release heat. Although this heat dissipation device can effectively cool the fuel cell and overcome the influence of gravity, it will still increase the volume of the fuel cell stack exponentially.

[0008] In summary, the defects of the conventional fuel cell stacks cooled by water, integral heat pipes or loop heat pipes can be summarized as follows: (1) When using water cooling, the temperature of the fuel cell stack is uneven, the adjustment method is single and inflexible, and it cannot cope with complex external conditions; (2) Cooling the fuel cell stack by integral heat pipes or loop heat pipes will increase the volume of the fuel cell stack exponentially; (3) The existing solutions of cooling fuel cells with heat pipes and liquid-cooled fuel cells cannot cope with sudden situations; (4) The existing solutions of cooling fuel cell stacks with heat pipes cannot flexibly adjust the temperature of the heat pipe evaporation zone, that is, the operating temperature of the fuel cell stack cannot be flexibly controlled. Summary of the invention

[0009] The present invention is made to solve the above-mentioned problems, and its purpose is to provide a fuel cell thermal management system based on a loop heat pipe.

[0010] The present invention provides a fuel cell thermal management system based on a loop heat pipe, which has the following characteristics: a liquid storage tank, a temperature control unit, a first solenoid valve, a working fluid pump, an evaporator inlet preheater, a fuel cell stack, a second solenoid valve, a condenser and a condenser outlet preheater, wherein the temperature control unit is arranged on the liquid storage tank and is used to adjust the temperature of the liquid working fluid in the liquid storage tank, the fuel cell stack has a liquid working fluid channel, the outlet of the liquid storage tank is connected to the evaporator inlet preheater through the first solenoid valve, and then connected to the inlet of the liquid working fluid channel, the outlet of the liquid working fluid channel is connected to the inlet of the condenser through the second solenoid valve, the outlet of the condenser is connected to the condenser outlet preheater, and then connected to the inlet of the liquid storage tank, and the working fluid pump is used to provide power for the flow of the liquid working fluid.

[0011] In the fuel cell thermal management system based on the loop heat pipe provided by the present invention, it can also have the following characteristics: wherein, the temperature control unit includes Peltier elements and electric heaters evenly and alternately arranged on the outer surface of the liquid storage tank, and a controller that can flexibly adjust the power of the Peltier elements and the electric heater according to the size of the system's cold and hot loads, two temperature measuring points are set on the wall of the liquid storage tank for measuring the gas temperature and liquid temperature in the liquid storage tank, and a pressure measuring point is set at the outlet position of the liquid storage tank for measuring the pressure change at the outlet of the liquid storage tank.

[0012] In the fuel cell thermal management system based on the loop heat pipe provided by the present invention, it can also have such features, and also include: an economizer, having a liquid pipeline and a two-phase pipeline, the inlet and outlet of the liquid pipeline are respectively connected to the first solenoid valve and the evaporator inlet preheater, and the inlet and outlet of the two-phase pipeline are respectively connected to the outlet of the liquid working fluid channel and the second solenoid valve.

[0013] The fuel cell thermal management system based on the loop heat pipe provided by the present invention may also have the following feature: wherein the working fluid pump is connected between the first solenoid valve and the inlet of the liquid pipeline to pump the liquid working fluid flowing through the first solenoid valve into the liquid pipeline.

[0014] In the fuel cell thermal management system based on the loop heat pipe provided by the present invention, it may also have such a feature, and also include: a third solenoid valve, one end of which is connected between the condenser outlet preheater and the inlet of the liquid storage tank, and the other end is connected between the first solenoid valve and the working fluid pump.

[0015] The fuel cell thermal management system based on the loop heat pipe provided by the present invention may also have the following characteristics: wherein the condensation method of the condenser is air cooling or water cooling, and the liquid working medium is a refrigerant.

[0016] In the fuel cell thermal management system based on the loop heat pipe provided by the present invention, it can also have the following characteristics: wherein, the fuel cell stack is formed by stacking multiple bipolar plates and multiple membrane battery assemblies, the bipolar plates and the membrane battery assemblies are arranged in a one-to-one correspondence, the bipolar plates include an anode plate and a cathode plate, the membrane battery assembly is clamped between the anode plate and the cathode plate, the anode plate and the cathode plate both have liquid working fluid channels, the liquid working fluid channels of the anode plate and the cathode plate are connected in parallel, and the liquid working fluid channels of all the bipolar plates are connected in parallel.

[0017] In the fuel cell thermal management system based on the loop heat pipe provided by the present invention, it can also have the following characteristics: wherein, the anode plate and the cathode plate are bonded together, the anode plate also has a hydrogen channel, the cathode plate also has an oxygen channel, the two width directions of the bipolar plate are respectively provided with a hydrogen inlet and outlet, an air inlet and outlet, and a working fluid inlet and outlet, the middle reaction area of ​​the bipolar plate contacts the membrane electrode of the membrane battery assembly to conduct electrons, the working fluid inlet and outlet are located at a diagonal position of the bipolar plate, the air inlet and outlet are located at another diagonal position of the bipolar plate, and the hydrogen inlet and outlet are located in the middle position of the bipolar plate.

[0018] In the fuel cell thermal management system based on the loop heat pipe provided by the present invention, it can also have such features, including: in the normal operation mode, the temperature control unit is flexibly opened according to the temperature control setting and the temperature and pressure of the working fluid in the fuel cell stack to ensure that the temperature and pressure of the liquid storage tank are at a certain level, the supercooled liquid working fluid in the liquid storage tank enters the working fluid pump after passing through the first solenoid valve, and then enters the liquid pipeline of the economizer, the supercooled liquid working fluid is preheated in the liquid pipeline, and then enters the evaporator inlet preheater to be heated to a saturated state or a two-phase state; then, the saturated or two-phase working fluid enters the interior of the bipolar plate of the fuel cell stack, absorbs the heat energy generated by the fuel cell, at which time the dryness of the working fluid increases, but it is still in a two-phase state; then, the two-phase working fluid after absorbing heat enters the two-phase state pipe of the economizer to be precooled, and the dryness is initially reduced; the precooled two-phase working fluid enters the condenser after passing through the second solenoid valve to be cooled into a supercooled liquid, and then is preheated by the condenser outlet preheater and is divided into two paths, one path enters the liquid storage tank, and the other path enters the working fluid pump after passing through the third solenoid valve.

[0019] In the fuel cell thermal management system based on the loop heat pipe provided by the present invention, it can also have such features, and also include: multiple special operating modes, including:

[0020] The first special operating mode:

[0021] When the condensation load is reduced, the working fluid flowing out of the condenser will be in a gaseous state or a two-phase state. At this time, the third solenoid valve, the condenser outlet preheater and the electric heater of the temperature control unit are closed, and the Peltier element of the temperature control unit is turned on. The gaseous state or the two-phase state is cooled and becomes liquid, and then enters the working fluid pump through the first solenoid valve;

[0022] The second special operating mode:

[0023] When the heat load of the fuel cell stack suddenly increases, the outlet working fluid of the bipolar plate will be too dry or overheated. At this time, the evaporator inlet preheater and the electric heater of the temperature control unit are turned off, the condensing power of the condenser is increased, and the Peltier element is turned on;

[0024] The third special operation mode:

[0025] When the fuel cell stack is cold started, the initial heat load is very low. At this time, the electric heater, evaporator inlet preheater, and condenser outlet preheater are turned on, and the Peltier element is turned off to heat the working fluid in the entire system;

[0026] Fourth special operating mode:

[0027] When the condensing load suddenly increases, the subcooling of the working fluid flowing out of the condenser will increase, causing the working fluid temperature entering the liquid storage tank to decrease. At this time, the condenser outlet preheater and electric heater are turned on, and the Peltier element is turned off.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The liquid working medium channel of the fuel cell stack is used to absorb the heat of the fuel cell. Compared with the water cooling method, the volume of the fuel cell stack does not increase; compared with the traditional integral and loop heat pipe cooling method, the volume of the fuel cell stack can be greatly reduced and the temperature of the fuel cell can be kept constant;

[0030] (2) The strong heat transfer capacity of the two-phase state is cleverly utilized and combined with the dynamic loop heat pipe technology to improve the cooling efficiency and further reduce its volume ratio;

[0031] (3) Using a temperature control unit as a supplement, combined with a liquid storage tank, can better control the temperature of the liquid storage tank, thereby controlling the temperature of the evaporation end;

[0032] (4) The settings of the temperature control unit and the evaporator inlet preheater and condenser outlet preheater can be adjusted according to the size of the cold load and the heat load to achieve auxiliary temperature control of the liquid storage tank, and then achieve flexible temperature control of the fuel cell; the above components can avoid sudden conditions in the fuel cell thermal management system and the shortcomings of uncontrollable heat load and cold load, thereby improving the system energy supply stability.

[0033] In summary, as a fuel cell thermal management system, the present invention can achieve efficient, stable and flexible cooling and control of fuel cells, and can overcome the disadvantage of the large volume of traditional heat pipe cooling fuel cell stacks. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic structural diagram of a fuel cell thermal management system based on a loop heat pipe in Example 1 of the present invention;

[0035] Figure 2 The structure of the fuel cell stack in Example 1 of the present invention is shown in FIG. Figure 1 ;

[0036] Figure 3 The structure of the fuel cell stack in Example 1 of the present invention is shown in FIG. Figure 2 ;

[0037] Figure 4 is a schematic diagram of the three-dimensional structure of the bipolar plate and the corresponding membrane battery assembly in Example 1 of the present invention;

[0038] Figure 5 is an exploded schematic diagram of a bipolar plate in Example 1 of the present invention;

[0039] Figure 6 Schematic diagram of the channels of hydrogen, oxygen and working fluid in Example 1 of the present invention;

[0040] Figure 7 It is a schematic diagram of the structure of a fuel cell thermal management system based on a loop heat pipe in Example 2 of the present invention. DETAILED DESCRIPTION

[0041] In order to make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments and the accompanying drawings specifically illustrate the fuel cell thermal management system based on the loop heat pipe of the present invention.

[0042] Example 1

[0043] Figure 1 It is a schematic diagram of the structure of a fuel cell thermal management system based on a loop heat pipe in Example 1 of the present invention.

[0044] like Figure 1 Embodiment 1 provides a fuel cell thermal management system 100 based on a loop heat pipe, which includes: a liquid storage tank 101, a temperature control unit, a first solenoid valve 113, a second solenoid valve 115, a third solenoid valve 114, a DC working fluid pump 104, an economizer 105, a condenser outlet preheater 106, an evaporator inlet preheater 107, a fuel cell stack 300 and a condenser 109.

[0045] The temperature control unit includes a Peltier element 102 , an electric heater 103 and a controller.

[0046] The Peltier element 102 and the electric heater 103 are evenly and alternately arranged on the outer surface of the liquid storage tank 101. The electric heater 103 is used to heat the working medium in the liquid storage tank 101, and the Peltier element 102 is used to cool the working medium in the liquid storage tank 101. The controller can flexibly adjust the power of the Peltier element 102 and the electric heater 103 according to the size of the cold and hot loads of the system.

[0047] The outlet of the liquid storage tank 101 is connected to the inlet of the DC working fluid pump 104 through a pipeline. A first solenoid valve 113 is provided on the pipeline. The first solenoid valve 113 can regulate the on-off and flow rate of the working fluid flowing from the liquid storage tank 101 into the DC working fluid pump 104.

[0048] Two temperature measuring points are arranged on the wall of the liquid storage tank 101 for measuring the gas temperature and liquid temperature in the liquid storage tank, and a pressure measuring point is arranged at the outlet of the liquid storage tank 101 for measuring the pressure change at the outlet of the liquid storage tank 101. The DC working fluid pump 104 is used to provide power for the flow of the liquid working fluid. In this embodiment, the liquid working fluid is a refrigerant. Pressure measuring points are arranged at the inlet and outlet of the DC working fluid pump 104, and the resistance to the flow of the working fluid is monitored by observing the change in its pressure.

[0049] Figure 2 The structure of the fuel cell stack in Example 1 of the present invention is shown in FIG. Figure 1 ; Figure 3 The structure of the fuel cell stack in Example 1 of the present invention is shown in FIG. Figure 2 ; Figure 4 is a schematic diagram of the three-dimensional structure of the bipolar plate and the corresponding membrane battery assembly in Example 1 of the present invention; Figure 5 is an exploded schematic diagram of a bipolar plate in Example 1 of the present invention; Figure 6 It is a schematic diagram of the channels of hydrogen, oxygen and working fluid in Example 1 of the present invention.

[0050] like Figure 2 to Figure 5 As shown, the fuel cell stack 300 is formed by stacking a plurality of bipolar plates 200 and a plurality of membrane battery assemblies 301. The bipolar plates 200 and the membrane battery assemblies 301 are arranged in a one-to-one correspondence.

[0051] like Figure 5 and Figure 6 As shown, the bipolar plate 200 includes an anode plate 201 and a cathode plate 202 .

[0052] The anode plate 201 includes an anode plate body 206, a liquid working medium channel 110 and a hydrogen channel 205. The liquid working medium channel 110 and the hydrogen channel 205 are two channels etched on the anode plate body 206 and are independent of each other. A hydrogen inlet and outlet and a working medium inlet and outlet are respectively provided in two width directions of the anode plate body 206. The hydrogen inlet and outlet are connected to the hydrogen channel 205, and the working medium inlet and outlet are connected to the liquid working medium channel 110. The working medium inlet and outlet are located at the diagonal position of the anode plate body 206, and the hydrogen inlet and outlet are located in the middle position of the anode plate body 206.

[0053] The cathode plate 202 includes a cathode plate body 207, a liquid working medium channel 110 and an oxygen channel 204. The liquid working medium channel 110 and the oxygen channel 204 are two independent channels etched on the cathode plate body 207. The shape and size of the cathode plate body 207 are the same as those of the anode plate 201, and the two are arranged opposite to each other. The two width directions of the anode plate body 206 are respectively provided with an air inlet and a working medium inlet, the air inlet and the working medium inlet are connected to the oxygen channel 204, and the working medium inlet and the working medium channel 110 are connected. The working medium inlet and the working medium inlet are located at a diagonal position of the cathode plate body 207, and the working medium inlet and the working medium inlet are located directly below the projection of the working medium inlet and the working medium inlet of the anode plate 201. The air inlet and the working medium inlet are located at another diagonal position of the cathode plate 202.

[0054] The membrane battery assembly 301 is correspondingly arranged between the anode plate 201 and the cathode plate 202 of the bipolar plate 200, and the intermediate reaction area of ​​the bipolar plate 200 contacts the membrane electrode of the corresponding membrane battery assembly 301 to conduct electrons. The anode plate 201 and the cathode plate 202 are bonded together. The liquid working medium channels 110 of the anode plate 201 and the cathode plate 202 are connected in parallel, and the liquid working medium channels 110 of all the bipolar plates 200 of the fuel cell stack 300 are connected in parallel (see Figure 1 ).

[0055] like Figure 1 As shown, the economizer 105 has a liquid pipeline 111 and a two-phase pipeline 112. The inlet of the liquid pipeline 111 is connected and communicated with the outlet of the DC working medium pump 104, and the outlet of the liquid pipeline 111 is connected and communicated with the inlet of all liquid working medium channels 110 of the fuel cell stack 300 through the evaporator inlet preheater 107. The inlet of the two-phase pipeline 112 is connected and communicated with the outlet of all liquid working medium channels 110 of the fuel cell stack 300, and the outlet of the two-phase pipeline 112 is connected and communicated with the inlet of the condenser 109 through a pipeline, and a second solenoid valve 115 is provided on the pipeline.

[0056] The economizer 105 can preheat the liquid working medium entering the evaporator inlet preheater 107 to reduce the power of the evaporator inlet preheater 107; and can also precool the two-phase working medium entering the condenser 109 to reduce the condensation power.

[0057] The evaporator inlet preheater 107 can ensure that the working fluid flowing into the bipolar plate 200 is in a saturated state, and ensure that the working fluid can be maintained in a two-phase state in the cooling channel of the bipolar plate 200, thereby achieving constant temperature control.

[0058] The second solenoid valve 115 can control the speed and amount of the fluid flow. By adjusting the opening and closing of the second solenoid valve 115, the speed and amount of the fluid passing through the condenser 109 can be adjusted. When the opening degree of the second solenoid valve 115 becomes smaller, the fluid flow speed slows down, the pressure before the condenser increases, and the working temperature of the condenser 109 increases; conversely, when the opening degree of the second solenoid valve 115 becomes larger, the fluid flow speed increases, the pressure before the condenser decreases, and the working temperature of the condenser 109 decreases.

[0059] The condenser 109 can be cooled by air cooling or water cooling. In this embodiment, the cooling of the working medium in the condenser 109 is achieved by the fan 108. The outlet of the condenser 109 is connected and communicated with the inlet of the liquid storage tank 101 through the condenser outlet preheater 106. The setting of the condenser outlet preheater 106 can reduce the power of the electric heater 103 of the liquid storage tank 101, thereby improving the flexibility of the temperature adjustment of the liquid storage tank 101.

[0060] The first solenoid valve 113 and the third solenoid valve 114 can be arranged to prevent gaseous or two-phase working fluid from directly entering the DC working fluid pump 104 , thereby avoiding damage to the DC working fluid pump 104 .

[0061] The liquid storage tank 101 is the core control device for temperature control. The temperature and pressure inside the liquid storage tank 101 satisfy a specific functional relationship with the temperature and pressure of the two-phase cooling medium inside the bipolar plate 200 of the fuel cell stack 110. Therefore, the operating temperature of the fuel cell stack 110 can be indirectly controlled by controlling the temperature of the liquid storage tank 101.

[0062] The fuel cell thermal management system 100 based on the loop heat pipe needs to be evacuated after the connection is intact and the pressure is maintained, and then the working fluid is filled into the liquid storage tank. Different working fluids can be selected for the fuel cell according to the type and cooling requirements.

[0063] The fuel cell thermal management system 100 based on a loop heat pipe includes a normal operation mode and multiple special operation modes.

[0064] 1. Normal operation mode

[0065] The Peltier element 102 and the electric heater 103 on the liquid storage tank 101 are flexibly opened according to the temperature control setting and the temperature and pressure of the working fluid in the bipolar plate 200 to ensure that the temperature and pressure of the liquid storage tank 101 are at a certain level. The supercooled liquid working fluid in the liquid storage tank 101 enters the DC working fluid pump 104 after passing through the first solenoid valve 113, and then enters the liquid pipeline 111 of the economizer 104. The supercooled liquid working fluid is preheated in the liquid pipeline 111, and then enters the evaporator inlet preheater 107 to be heated to a saturated state or a two-phase state to ensure that the working fluid in the bipolar plate is always in a two-phase state, thereby maintaining a constant temperature; afterwards, the saturated state or two-phase state of the working fluid enters the liquid working fluid channel 110 of the bipolar plate 200 of the fuel cell stack 300 and absorbs The heat energy generated by the fuel cell increases the dryness of the working fluid, but it is still in a two-phase state; afterwards, the two-phase working fluid after absorbing heat enters the two-phase tube 112 of the economizer 104 to be pre-cooled, and the dryness is initially reduced; the pre-cooled two-phase working fluid passes through the second solenoid valve 115 and enters the condenser 109 to be cooled into a supercooled liquid, and then is preliminarily preheated by the condenser outlet preheater 106, and then is divided into two paths, one path enters the liquid storage tank 101, and the other path enters the DC working fluid pump 104 after passing through the third solenoid valve 114, completing the whole cycle.

[0066] 2. The first special operating mode

[0067] When the condensation load is reduced, the working fluid flowing out of the condenser will be in a gaseous or two-phase state. At this time, the third solenoid valve 114 is closed to prevent the gaseous or two-phase working fluid from directly entering the DC working fluid pump 104; and the condenser outlet preheater 106 and the electric heater 106 are closed, and the Peltier element 103 is turned on. The gaseous or two-phase state is cooled and becomes liquid, and then its cycle is the same as the cycle in the normal operation mode. After several oscillation cycles, the system will re-establish a new balance. If the condensation load power is reduced too much, the Peltier element 102 power is turned to the maximum. After several minutes, observe the temperature measurement point. If the system cannot establish a new balance or cannot reach the preset control temperature, the system will automatically shut down and stop the supply of hydrogen and oxygen.

[0068] 3. Second special operation mode

[0069] When the heat load of the fuel cell stack suddenly increases, the dryness of the outlet working fluid of the bipolar plate 200 will be too high or overheated. At this time, the evaporator inlet preheater 107 and the electric heater 103 are turned off, the speed of the cooling fan 108 is increased, and the Peltier element 102 is turned on. The heat load is adjusted by increasing the condensing power and the cooling power of the liquid storage tank 101; after several oscillations, the system will establish a new balance to meet the system temperature control requirements; if the condensing power at the condensing end and the power of the Peltier element 102 of the liquid storage tank 101 reach the maximum value, observe the temperature measurement point, and still cannot establish a new balance within several minutes, that is, the fuel cell cannot be controlled in the required temperature control range. At this time, the system will automatically shut down and stop the supply of hydrogen and oxygen. In addition, when the overheating of the outlet working fluid of the bipolar plate 200 reaches a certain degree, the supply of hydrogen and oxygen should also be immediately turned off to prevent the damage of the bipolar plate 200 and the sub-exchange membrane of the membrane battery assembly 301 due to excessive temperature.

[0070] 4. The third special operation mode

[0071] When the fuel cell stack is cold started, the initial heat load is very low. At this time, the electric heater 103, the evaporator inlet preheater 107, and the condenser outlet preheater 106 are turned on, and the Peltier element 102 is turned off to heat the working fluid in the entire system, and the temperature measurement point is observed until the working fluid reaches the set temperature. After that, the system will quickly rise and reach the preset temperature to achieve temperature control of the fuel cell.

[0072] 5. The fourth special operating mode

[0073] When the condensation load suddenly increases, the supercooling of the working fluid flowing out of the condenser 109 will increase, causing the working fluid temperature entering the liquid storage tank 101 to decrease. At this time, turn on the condenser outlet preheater 106 and the electric heater 103, and turn off the Peltier element 102. After that, the system will establish a new balance after several oscillations to achieve temperature control of the fuel cell. Observe the temperature measurement points. If the system still cannot establish a new balance after all heating elements reach maximum power, the supply of hydrogen and oxygen should be immediately turned off after several minutes.

[0074] In summary, the fuel cell thermal management system 100 based on the loop heat pipe of the present invention can greatly reduce the volume ratio of the fuel cell stack 300 while effectively cooling, and can flexibly control the operating temperature of the fuel cell stack.

[0075] Example 2

[0076] Figure 6 It is a schematic diagram of the structure of a fuel cell thermal management system based on a loop heat pipe in Example 2 of the present invention.

[0077] like Figure 6As shown, Embodiment 2 provides a fuel cell thermal management system 100' based on a loop heat pipe, which differs from the fuel cell thermal management system 100 based on a loop heat pipe of Embodiment 1 only in that it does not have a pipeline connecting the preheater 106 and the DC working fluid pump 104 and a third solenoid valve 114 as in Embodiment 1. The other structures of Embodiment 2 are exactly the same as those of Embodiment 1. For the sake of convenience, the same symbols are given to the same structures as those of Embodiment 1 in this embodiment, and the same descriptions are omitted.

[0078] Based on the above structure, in this embodiment, the cold liquid or two-phase state coming out of the condenser 109 all enters the liquid storage tank 101. This method is suitable for application scenarios with relatively small or moderate condensing power, that is, application scenarios with low heating demand.

[0079] The fuel cell thermal management system 100' based on the loop heat pipe of the second embodiment also includes a normal operation mode and first to fourth special operation modes.

[0080] The only difference between the conventional operation mode of Example 2 and the conventional operation mode of Example 1 is that the cold liquid or two-phase state coming out of the condenser 109 all enters the liquid storage tank 101, and the other circulation processes are the same as those of Example 1.

[0081] The first to fourth special operation modes of the second embodiment are respectively the same as the first to fourth special operation modes of the first embodiment, and are not described again herein.

[0082] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A fuel cell thermal management system based on a loop heat pipe, characterized in that: include: A liquid storage tank, a temperature control unit, a first solenoid valve, a working fluid pump, an evaporator inlet preheater, a fuel cell stack, a second solenoid valve, a condenser, and a condenser outlet preheater. The temperature control unit is arranged on the liquid storage tank and is used to adjust the temperature of the liquid working medium in the liquid storage tank. The fuel cell stack has a liquid working medium channel. The outlet of the liquid storage tank is connected to the inlet preheater of the evaporator through the first solenoid valve, and then connected to the inlet of the liquid working medium channel. The outlet of the liquid working medium channel is connected to the inlet of the condenser through the second solenoid valve. The outlet of the condenser is connected to the outlet preheater of the condenser, and then connected to the inlet of the liquid storage tank. The working medium pump is used to provide power for the flow of liquid working medium.

2. The fuel cell thermal management system based on a loop heat pipe according to claim 1, characterized in that: in, The temperature control unit includes Peltier elements and electric heaters uniformly and alternately arranged on the outer surface of the liquid storage tank, and a controller that can flexibly adjust the power of the Peltier elements and the electric heater according to the size of the cold and hot load of the system. Two temperature measuring points are arranged on the wall surface of the liquid storage tank to measure the gas temperature and liquid temperature in the liquid storage tank. A pressure measuring point is arranged at the outlet of the liquid storage tank to measure the pressure change at the outlet of the liquid storage tank.

3. The fuel cell thermal management system based on a loop heat pipe according to claim 2, characterized in that: Also includes: The economizer comprises a liquid pipeline and a two-phase pipeline, wherein the inlet and outlet of the liquid pipeline are respectively connected to the first solenoid valve and the evaporator inlet preheater, and the inlet and outlet of the two-phase pipeline are respectively connected to the outlet of the liquid working medium channel and the second solenoid valve.

4. The fuel cell thermal management system based on a loop heat pipe according to claim 3, characterized in that: in, The working medium pump is connected between the first solenoid valve and the inlet of the liquid pipeline, and is used to pump the liquid working medium flowing through the first solenoid valve into the liquid pipeline.

5. The fuel cell thermal management system based on a loop heat pipe according to claim 4, characterized in that: Also includes: A third solenoid valve has one end connected between the condenser outlet preheater and the inlet of the liquid storage tank, and the other end connected between the first solenoid valve and the working fluid pump.

6. The fuel cell thermal management system based on a loop heat pipe according to claim 1, characterized in that: in, The condensation method of the condenser is air cooling or water cooling. The working medium is a refrigerant.

7. The fuel cell thermal management system based on a loop heat pipe according to any one of claims 1 to 6, characterized in that: in, The fuel cell stack is formed by stacking a plurality of bipolar plates and a plurality of membrane battery assemblies, wherein the bipolar plates and the membrane battery assemblies are arranged in a one-to-one correspondence. The bipolar plate comprises an anode plate and a cathode plate, and the membrane battery assembly is sandwiched between the anode plate and the cathode plate. The anode plate and the cathode plate both have the liquid working medium channel, the liquid working medium channels of the anode plate and the cathode plate are connected in parallel, and the liquid working medium channels of all the bipolar plates are connected in parallel.

8. The fuel cell thermal management system based on a loop heat pipe according to claim 7, characterized in that: in, The anode plate and the cathode plate are bonded together, The anode plate also has a hydrogen channel, and the cathode plate also has an oxygen channel. The bipolar plate is provided with a hydrogen inlet and outlet, an air inlet and outlet, and a working fluid inlet and outlet in two width directions, respectively. The middle reaction area of ​​the bipolar plate contacts the membrane electrode of the membrane battery assembly to conduct electrons. The working medium inlet and outlet are located at a diagonal position of the bipolar plate, the air inlet and outlet are located at another diagonal position of the bipolar plate, and the hydrogen inlet and outlet are located at a middle position of the bipolar plate.

9. The fuel cell thermal management system based on a loop heat pipe according to claim 7, characterized in that: include: In the normal operation mode, the temperature control unit is flexibly opened according to the temperature control setting and the temperature and pressure of the working fluid in the fuel cell stack to ensure that the temperature and pressure of the liquid storage tank are at a certain level. The supercooled liquid working fluid in the liquid storage tank enters the working fluid pump after passing through the first solenoid valve, and then enters the liquid pipeline of the economizer. The supercooled liquid working fluid is preheated in the liquid pipeline, and then enters the evaporator inlet preheater to be heated to a saturated state or a two-phase state; then, the saturated or two-phase working fluid enters the interior of the bipolar plate of the fuel cell stack and absorbs the heat energy generated by the fuel cell. At this time, the dryness of the working fluid increases, but it is still in a two-phase state; then, the two-phase working fluid after absorbing heat enters the two-phase state tube of the economizer to be precooled, and the dryness decreases initially; the precooled two-phase working fluid enters the condenser after passing through the second solenoid valve to be cooled into a supercooled liquid, and then is preheated by the condenser outlet preheater and is divided into two paths, one path enters the liquid storage tank, and the other path enters the working fluid pump after passing through the third solenoid valve.

10. The fuel cell thermal management system based on a loop heat pipe according to claim 7, characterized in that: Also includes: Multiple special operating modes, including: The first special operating mode: When the condensation load is reduced, the working medium flowing out of the condenser will be in a gaseous state or a two-phase state. At this time, the third solenoid valve, the condenser outlet preheater and the electric heater of the temperature control unit are closed, and the Peltier element of the temperature control unit is turned on. The gaseous state or the two-phase state is cooled and becomes a liquid state, and then enters the working medium pump through the first solenoid valve; The second special operating mode: When the heat load of the fuel cell stack suddenly increases, the dryness of the outlet working fluid of the bipolar plate may be too high or it may be overheated. At this time, the evaporator inlet preheater and the electric heater of the temperature control unit are turned off, the condensing power of the condenser is increased, and the Peltier element is turned on; The third special operation mode: When the fuel cell stack is cold started, the initial heat load is very low, at which time the electric heater, the evaporator inlet preheater, and the condenser outlet preheater are turned on, and the Peltier element is turned off to heat the working fluid in the entire system; Fourth special operating mode: When the condensation load suddenly increases, the subcooling degree of the working medium flowing out of the condenser will increase, so that the temperature of the working medium entering the liquid storage tank will decrease. At this time, the condenser outlet preheater and the electric heater are turned on, and the Peltier element is turned off.

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