High-power fuel cell thermal management system and heat exchange coefficient calculation method thereof

Abstract

The invention relates to a high-power fuel cell thermal management system which comprises a hydrogen source, a proportional valve, an air compressor, a heat exchanger, a water tank, an atomizer and a plate heat exchanger, high-temperature and high-pressure air output by the air compressor passes through the heat exchanger, exchanges heat with tail exhaust gas of the galvanic pile for cooling, and then enters a cathode of the galvanic pile; liquid water in the water tank enters the atomizer to form vaporific liquid water, the vaporific liquid water passes through the plate heat exchanger and exchanges heat with high-temperature cooling liquid circularly entering the plate heat exchanger from the galvanic pile to be heated, and the vaporific liquid water is vaporized to humidify hydrogen at an anode inlet of the galvanic pile and air at a cathode inlet of the galvanic pile. The heat exchanger is arranged on the air flow path between the air compressor and the electric pile, tail gas of the fuel cell is fully utilized, high-temperature cooling water in the plate heat exchanger is utilized to exchange heat with vaporific liquid water, the vaporific liquid water is vaporized, internal resources of a fuel cell system are fully utilized, internal parts of the fuel system can be reduced, and the fuel cell system is more energy-saving and environment-friendly. The system integration degree is improved; and the system thermal load is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and particularly to a high-power fuel cell thermal management system and a calculation method for its heat transfer coefficient. Background Art

[0002] With the increasing maturity of the development of hydrogen energy and its market promotion, more and more on-vehicle fuel cell systems are being applied. Especially for commercial heavy vehicles, the required power of hydrogen fuel cells basically reaches more than 200 kW. Compared with the current hydrogen fuel cells below 130 kW, the complexity of all aspects of the system is even greater. Moreover, as the power of the hydrogen fuel cell increases, its power generation efficiency gradually decreases. When reaching the rated point, the general power generation efficiency is 45%. For a 200-kW fuel cell system, its heat generation power reaches 240 kW, bringing an extremely heavy heat load to the entire system. The thermal management of hydrogen fuel cells generally uses coolant to convect and dissipate heat with the outside air through a fan. For high-power fuel cells, to meet the normal inlet stack water temperature requirements of the fuel cell, a sufficient number of cooling fans are required to ensure the heat dissipation effect, but this is not very realistic on the vehicle. Therefore, the current thermal management of high-power fuel cell systems is a difficult point.

[0003] In the prior art, the thermal management of fuel cells mainly focuses on solving the heat dissipation problem and the size problem. For example, CN216597649U proposes an integrated thermal management device with a small floor space; CN109698368A starts from the perspective of the whole vehicle and proposes to use a new type of coolant medium, which is gaseous inside the fuel cell stack and liquid through the fan, and performs reciprocating circulation without a water tank. However, this patent does not consider the actual situation. The existence of the gas-liquid two-phase will cause cavitation to the water pump and reduce the service life of the water pump; CN114335594A provides a method of coupling with the vehicle air conditioning refrigeration. The hot water of the radiator first exchanges heat through the air conditioning refrigeration unit and then is secondarily cooled by the fan to reduce the overall load. However, this method requires considering the thermal management from the perspective of the whole vehicle, with a complex structure and poor practicability; CN116454316B provides a control method for the cooling fan of a high-power fuel cell system, which is symmetrically controlled and grouped controlled to reduce noise and the water temperature fluctuation caused by the frequent start and stop of the fan.

[0004] The above patents all make certain controls for the existing thermal management, or optimize the structure, or couple with the vehicle air conditioning system. None of them start from the principle or the fuel cell system itself to think about solving the related thermal management problems. At the same time, in the prior art, the thermal management system is usually designed based on experience, lacking accurate calculation and analysis, so it is difficult to ensure the heat dissipation efficiency of the thermal management system.

[0005] In summary, it is urgent to propose a high-power fuel cell thermal management system based on accurate calculation to solve the above technical problems. Summary of the Invention

[0006] In view of this, the present invention provides a high-power fuel cell thermal management system and a method for calculating its heat transfer coefficient. The purpose is to, on the premise of making full use of the internal resources of the fuel cell, through mathematical modeling and precise analysis and calculation, reduce the internal components of the fuel system, improve the system integration degree, and at the same time reduce the system heat load, so as to achieve precise control of the thermal management of the fuel cell.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A high-power fuel cell thermal management system includes a hydrogen source, a proportional valve, an air compressor, a heat exchanger, a water tank, an atomizer, and a plate heat exchanger;

[0009] The hydrogen output from the hydrogen source enters the anode of the fuel cell stack through the proportional valve;

[0010] The high-temperature and high-pressure air output by the air compressor passes through the heat exchanger, exchanges heat with the tail gas of the fuel cell stack to cool down, and then enters the cathode of the fuel cell stack;

[0011] The liquid water in the water tank enters the atomizer to form atomized liquid water, and then passes through the plate heat exchanger, exchanges heat with the high-temperature coolant circulating from the fuel cell stack into the plate heat exchanger to heat up. After the atomized liquid water vaporizes, it humidifies the hydrogen at the anode inlet of the fuel cell stack and the air at the cathode inlet respectively.

[0012] The present invention also provides a method for calculating the heat transfer coefficient based on the above high-power fuel cell thermal management system, including the following steps:

[0013] S1. Establish a mathematical model based on the equality of the heat generated by the fuel cell stack and the latent heat of vaporization of the atomized liquid water for humidification, and calculate the heat transfer coefficient K1 of the plate heat exchanger;

[0014] S2. Establish a mathematical model based on the equality of the heat required to cool down the high-temperature and high-pressure air output by the air compressor and the heat that can be exchanged by the tail gas of the fuel cell stack, and calculate the heat transfer coefficient K2 of the heat exchanger;

[0015] S3. According to the heat transfer coefficient K1 of the plate heat exchanger and the heat transfer coefficient K2 of the heat exchanger calculated in step S1, select a plate heat exchanger and a heat exchanger that meet the requirements for use in the high-power fuel cell thermal management system.

[0016] Further, step S1 includes:

[0017] S1-1. Calculate the heat Q generated by the fuel cell stack q ;

[0018] The heat Q generated by the fuel cell stack q is calculated by the following formula:

[0019] Qq = C water * m water *(T s_in - T s_out ) (1);

[0020] In the formula, C water is the specific heat capacity of the cooling liquid of the plate heat exchanger, with a value of 4.2 KJ / kg / K; m water is the mass flow rate of the cooling liquid of the plate heat exchanger, measured by a flow meter arranged at the inlet of the cooling liquid of the plate heat exchanger; T s_out is the temperature at the outlet of the cooling liquid of the plate heat exchanger, measured by a temperature sensor arranged at the outlet of the cooling liquid of the plate heat exchanger; T s_in is the inlet temperature of the cooling liquid of the plate heat exchanger.

[0021] Furthermore, the step S1 further includes:

[0022] S1-2. Calculate the latent heat of vaporization Q of the liquid water for humidification v :

[0023] The latent heat of vaporization Q of the liquid water for humidification v is calculated by the following formula:

[0024] Q v = h water *(m an-water + m ca-water ) (2);

[0025] In the formula, h water is the enthalpy value of the latent heat of vaporization of water, with a value of 2550 KJ / kg; m an-water is the amount of water for anodic humidification; m ca-water is the amount of water for cathodic humidification.

[0026] Furthermore, the amount of water for anodic humidification m in the step S1-2 an-water is calculated by the following formula:

[0027]

[0028] In the formula, P water is the saturation pressure of water vapor at the current temperature; RH an is the humidity at the anodic inlet, measured by a humidity sensor arranged at the anodic inlet; P an is the pressure at the anodic inlet, measured by a pressure sensor arranged at the anodic inlet, is the inlet mass flow rate of hydrogen at the current current;

[0029] The saturation pressure P of water vapor at the current temperature water is calculated by the following formula:

[0030]

[0031] Wherein, T is the temperature of the fuel cell stack. a, b, c, d, e, and f are all coefficients related to the saturated pressure of water vapor, and the specific values are: a = -5800.2206; b = 1.3914993; c = -0.048640239; d = 0.41764768E-4; e = -0.14452093E-7; f = 6.5459673;

[0032] The inlet mass flow rate of hydrogen at the current current It is calculated by the following formula:

[0033]

[0034] Wherein, I is the current of the fuel cell, N is the number of single cells in the stack, and t is the operating time of the fuel cell thermal management system.

[0035] Further, the amount of cathode humidification water m in step S1-2 ca-water It is calculated by the following formula:

[0036]

[0037] Wherein, P water is the saturated pressure of water vapor at the current temperature; RH ca is the humidity at the cathode inlet, which is measured by a humidity sensor arranged at the cathode inlet; P ca is the pressure at the cathode inlet, which is measured by a pressure sensor arranged at the cathode inlet, and q Air is the inlet mass flow rate of air at the current current;

[0038] The inlet mass flow rate of air q at the current current Air It is calculated by the following formula:

[0039]

[0040] Wherein, I is the current of the fuel cell, N is the number of single cells in the stack, t is the operating time of the fuel cell thermal management system, and λ Air is the air stoichiometry ratio, and λ Air is set artificially according to needs, is the molar mass of oxygen.

[0041] Further, step S1 further includes:

[0042] S1-3. Calculate the heat transfer coefficient K1 of the plate heat exchanger:

[0043] The heat Q generated by the stack qEqual to the latent heat of vaporization Q of the liquid water for humidification, i.e.: v Equal, namely:

[0044] Q q = Q v (8);

[0045] For the plate heat exchanger, the following relationship exists:

[0046] Q v = K1 * (T s_in - T s_out ) (9);

[0047] In the formula, T s_out is the temperature at the outlet of the coolant of the plate heat exchanger, measured by the temperature sensor arranged at the outlet of the coolant of the plate heat exchanger; T s_in is the inlet temperature of the coolant of the plate heat exchanger;

[0048] Substitute the calculated results in steps S1-1 and S1-2 into formula (8) and formula (9), and obtain two equations with two unknowns. The unknowns are K1 and T s_in , and calculate the value of the heat transfer coefficient K1.

[0049] Furthermore, the said step S2 includes:

[0050] S2-1. Calculate the heat Q required to cool the high-temperature and high-pressure air output by the air compressor: ca :

[0051] Q ca = q Air * C Air * (T c_out - T ca_in ) (10);

[0052] In the formula, q Air is the inlet mass flow rate of air at the current current, calculated by formula (7); C Air is the specific heat capacity of air, with a value of 1.004 KJ / kg / K; T c_out is the outlet temperature of the air compressor, measured by the temperature sensor arranged at the outlet of the air compressor; T ca_in is the inlet temperature of the cathode of the fuel cell stack.

[0053] Furthermore, the said step S2 also includes:

[0054] S2-2. Calculate the heat exchange quantity Q of the tail gas of the fuel cell stack: ca_out :

[0055] Q ca_out = (q Air - q con ) * CAir *(T ca -T ca_out ) (11);

[0056] In the formula, q Air is the intake air mass flow rate of air under the current current, calculated from formula (7); q con is the air consumption of the stack; C Air is the specific heat capacity of air, with a value of 1.004 KJ / kg / K; T ca_out is the temperature of the exhaust gas when it exits the stack, measured by a temperature sensor arranged at the exhaust gas outlet of the stack; T ca is the temperature of the exhaust gas after being heated by the heat exchanger;

[0057] The air consumption q of the stack con is calculated by the following formula:

[0058]

[0059] In the formula, I is the current of the fuel cell, and N is the number of single cell sheets of the stack.

[0060] Furthermore, step S2 further includes:

[0061] S2-3. Calculate the heat transfer coefficient K2 of the heat exchanger:

[0062] The heat required Q for the high-temperature and high-pressure air output by the air compressor to cool down ca is equal to the heat exchangeable Q with the exhaust gas of the stack ca_out , that is:

[0063] Q ca =Q ca_out (13);

[0064] For the heat exchanger, there is the following relationship:

[0065]

[0066] In the formula, T c_out is the temperature at the outlet of the air compressor, measured by a temperature sensor arranged at the outlet of the air compressor; T ca_in is the temperature at the cathode inlet of the stack; T ca_out is the temperature of the exhaust gas when it exits the stack, measured by a temperature sensor arranged at the exhaust gas outlet of the stack; T ca is the temperature of the exhaust gas after being heated by the heat exchanger;

[0067] Substitute the calculated results in steps S2-1 and S2-2 into formula (13) to obtain T ca_in and T caThe relational expression is substituted into formula (14) to obtain a relational expression regarding K2 and T ca_in The relational expression;

[0068] The inlet temperature T of the cathode of the stack ca_in Is determined by the temperature requirement at the inlet of the stack. According to the set demand value of the inlet temperature T of the cathode of the stack ca_in The heat transfer coefficient K2 of the heat exchanger is calculated.

[0069] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0070] (1) By arranging a heat exchanger on the air flow path between the air compressor and the stack, using the tail exhaust gas of the stack as a cold source to exchange heat with the high-temperature and high-pressure air output from the air compressor, the air temperature is reduced. Such a setting can not only cancel the intercooler component in the traditional fuel cell, but also make full use of the tail exhaust gas of the fuel cell without the need to additionally set a cold source.

[0071] (2) A water tank and an atomizer are set as the humidifying components of the fuel cell system. The atomized liquid water ejected by the atomizer first passes through a plate heat exchanger before humidifying the incoming hydrogen and air. Using the high-temperature cooling water that takes away the heat of the stack in the plate heat exchanger to exchange heat with the atomized liquid water, the atomized liquid water is vaporized, that is, the atomized liquid water can be used as the cold source of the high-temperature liquid water in the plate heat exchanger to cool it down, and the high-temperature liquid water in the plate heat exchanger can also be used as the heat source of the atomized liquid water to provide energy for its vaporization. Making full use of the internal resources of the fuel cell system can reduce the internal components of the fuel system, improve the system integration degree while reducing the system heat load.

[0072] (3) Based on the following two heat balances: the heat generated by the stack is equal to the latent heat of vaporization of the atomized liquid water for humidification, and the heat required to cool the high-temperature and high-pressure air output from the air compressor is equal to the heat that can be exchanged by the tail exhaust gas of the stack. A mathematical model of the thermal management system for high-power fuel cells is established. Through the accurate calculation of the heat of each part, the heat source of the fuel cell thermal management is clarified. Then, based on the two heat balances, the heat transfer coefficient K1 of the plate heat exchanger and the heat transfer coefficient K2 of the heat exchanger are calculated respectively. The heat exchanger is appropriately selected for the fuel cell system according to the heat transfer coefficient to ensure that the thermal management system for high-power fuel cells can operate fully and effectively, reduce the fuel cell heat load, and provide conditions for the precise control of the fuel cell thermal management.

[0073] Other features and advantages of the present invention will be described in the subsequent specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained through the structures pointed out in the specification and the drawings. Brief Description of the Drawings

[0074] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0075] Figure 1 Fig. shows the structural schematic diagram of the high-power fuel cell thermal management system according to the embodiment of the present invention;

[0076] In the figure: 1, hydrogen source; 2, proportional valve; 3, air compressor; 4, heat exchanger; 5, water tank; 6, atomizer; 7, plate heat exchanger; 8, fuel cell stack. Detailed implementation manners

[0077] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0078] An embodiment of the present invention provides a high-power fuel cell thermal management system, as shown in the attached Figure 1 figure, which includes a hydrogen source 1, a proportional valve 2, an air compressor 3, a heat exchanger 4, a water tank 5, an atomizer 6, and a plate heat exchanger 7;

[0079] The hydrogen output by the hydrogen source 1 enters the anode of the fuel cell stack 8 after passing through the proportional valve 2;

[0080] The high-temperature and high-pressure air output by the air compressor 3 passes through the heat exchanger 4, exchanges heat with the tail gas of the fuel cell stack 8 to reduce the temperature, and then enters the cathode of the fuel cell stack 8;

[0081] The liquid water in the water tank 5 enters the atomizer 6 to form atomized liquid water, and then passes through the plate heat exchanger 7, exchanges heat with the high-temperature coolant circulating from the fuel cell stack into the plate heat exchanger 7 to increase the temperature. After the atomized liquid water vaporizes, it humidifies the hydrogen at the anode inlet of the fuel cell stack 8 and the air at the cathode inlet respectively.

[0082] By providing a heat exchanger in the air flow path between the air compressor and the fuel cell stack, using the tail gas of the fuel cell stack as a cold source to exchange heat with the high-temperature and high-pressure air output from the air compressor, the air temperature can be reduced. Such a setting can not only cancel the intermediate cooler component in the traditional fuel cell, but also make full use of the tail gas of the fuel cell stack without the need to additionally set a cold source.

[0083] A water tank and an atomizer are set as the humidifying components of the fuel cell system. The atomized liquid water ejected by the atomizer first passes through a plate heat exchanger before humidifying the hydrogen and air entering the stack. The high-temperature cooling water that takes away the heat of the fuel cell stack in the plate heat exchanger is used to exchange heat with the atomized liquid water, vaporizing the atomized liquid water. That is, the atomized liquid water can be used as the cold source of the high-temperature liquid water in the plate heat exchanger to cool it down, and the high-temperature liquid water in the plate heat exchanger can also be used as the heat source of the atomized liquid water to provide energy for its vaporization. By making full use of the internal resources of the fuel cell system, the number of internal components of the fuel system can be reduced, the system integration degree can be improved, and the system heat load can be reduced at the same time.

[0084] An embodiment of the present invention also proposes a calculation method for the heat transfer coefficient of a heat management system based on the above-mentioned high-power fuel cell, including the following steps:

[0085] S1. Establish a mathematical model based on the equality of the heat generated by the fuel cell stack and the latent heat of vaporization of the atomized liquid water for humidification, and calculate the heat transfer coefficient K1 of the plate heat exchanger;

[0086] S2. Establish a mathematical model based on the equality of the heat required to cool the high-temperature and high-pressure air output by the air compressor and the heat that can be exchanged by the exhaust gas of the fuel cell stack, and calculate the heat transfer coefficient K2 of the heat exchanger;

[0087] S3. According to the heat transfer coefficient K1 of the plate heat exchanger and the heat transfer coefficient K2 of the heat exchanger calculated in step S1, select a plate heat exchanger and a heat exchanger that meet the requirements for use in the high-power fuel cell heat management system.

[0088] The specific content of step S1 is as follows:

[0089] S1-1. Calculate the heat Q generated by the fuel cell stack q :

[0090] The heat Q generated by the fuel cell stack q is calculated by the following formula:

[0091] Q q = C water * m water *(T s_in - T s_out ) (1);

[0092] In the formula, C water is the specific heat capacity of the cooling liquid of the plate heat exchanger, with a value of 4.2 KJ / kg / K; m water is the mass flow rate of the cooling liquid of the plate heat exchanger, which is measured by a flow meter arranged at the inlet of the cooling liquid of the plate heat exchanger; T s_out is the temperature at the outlet of the cooling liquid of the plate heat exchanger, which is measured by a temperature sensor arranged at the outlet of the cooling liquid of the plate heat exchanger; T s_in is the inlet temperature of the cooling liquid of the plate heat exchanger.

[0093] S1-2. Calculate the latent heat of vaporization Q of the liquid water for humidification v :

[0094] The latent heat of vaporization Q of the liquid water for humidification v is calculated by the following formula:

[0095] Q v = h water * (m an-water + m ca-water ) (2);

[0096] In the formula, h water is the latent heat of vaporization enthalpy value of water, and the value is 2550 KJ / kg; m an-water is the anode humidification water quantity; m ca-water is the cathode humidification water quantity.

[0097] The anode humidification water quantity m an-water is calculated by the following formula:

[0098]

[0099] In the formula, P water is the saturation pressure of water vapor at the current temperature; RH an is the humidity at the anode inlet, which is measured by a humidity sensor arranged at the anode inlet; P an is the pressure at the anode inlet, which is measured by a pressure sensor arranged at the anode inlet, is the intake mass flow rate of hydrogen under the current current.

[0100] The saturation pressure P of water vapor at the current temperature water is calculated by the following formula:

[0101]

[0102] In the formula, T is the temperature of the fuel cell stack. a, b, c, d, e, f are all coefficients related to the saturation pressure of water vapor, and the specific values are: a = -5800.2206; b = 1.3914993; c = -0.048640239; d = 0.41764768E-4; e = -0.14452093E-7; f = 6.5459673.

[0103] The intake mass flow rate of hydrogen under the current current is calculated by the following formula:

[0104]

[0105] Wherein, I is the current of the fuel cell, N is the number of single cells in the stack, and t is the operating time of the fuel cell thermal management system.

[0106] The cathode humidification water volume m ca-water is calculated by the following formula:

[0107]

[0108] Wherein, P water is the saturation pressure of water vapor at the current temperature; RH ca is the humidity at the cathode inlet, which is measured by a humidity sensor arranged at the cathode inlet; P ca is the pressure at the cathode inlet, which is measured by a pressure sensor arranged at the cathode inlet, and q Air is the inlet air mass flow rate of air at the current current.

[0109] The inlet air mass flow rate of air q at the current current Air is calculated by the following formula:

[0110]

[0111] Wherein, I is the current of the fuel cell, N is the number of single cells in the stack, t is the operating time of the fuel cell thermal management system, and λ Air is the air stoichiometry ratio, and λ Air is artificially set according to needs, is the molar mass of oxygen.

[0112] S1-3. Calculate the heat transfer coefficient K1 of the plate heat exchanger:

[0113] The heat Q generated by the stack q is equal to the latent heat of vaporization Q v of the liquid water for humidification, that is:

[0114] Q q = Q v (8);

[0115] For the plate heat exchanger, there is the following relationship:

[0116] Q v = K1 * (T s_in - T s_out ) (9);

[0117] Wherein, T s_out is the temperature at the coolant outlet of the plate heat exchanger, which is measured by a temperature sensor arranged at the coolant outlet of the plate heat exchanger; T s_in is the coolant inlet temperature of the plate heat exchanger.

[0118] Substitute the calculated results in steps S1-1 and S1-2 into formula (8) and formula (9) to obtain two equations with two unknowns, where the unknowns are K1 and T respectively. s_in , and calculate the value of the heat transfer coefficient K1.

[0119] The specific steps of step S2 are as follows:

[0120] S2-1. Calculate the heat Q required to cool the high-temperature and high-pressure air output by the air compressor. ca :

[0121] Q ca = q Air * C Air * (T c_out - T ca_in ) (10);

[0122] In the formula, q Air is the intake mass flow rate of air at the current current, which is calculated by formula (7); C Air is the specific heat capacity of air, with a value of 1.004 KJ / kg / K; T c_out is the temperature at the outlet of the air compressor, which is measured by a temperature sensor arranged at the outlet of the air compressor; T ca_in is the inlet temperature of the cathode of the fuel cell stack.

[0123] S2-2. Calculate the heat exchange amount Q of the exhaust gas of the fuel cell stack. ca_out :

[0124] Q ca_out = (q Air - q con ) * C Air * (T ca - T ca_out ) (11);

[0125] In the formula, q Air is the intake mass flow rate of air at the current current, which is calculated by formula (7); Q con is the air consumption of the fuel cell stack; C Air is the specific heat capacity of air, with a value of 1.004 KJ / kg / K; T ca_out is the temperature of the exhaust gas when it exits the fuel cell stack, which is measured by a temperature sensor arranged at the exhaust gas outlet of the fuel cell stack; T ca is the temperature of the exhaust gas after being heated by the heat exchanger.

[0126] The air consumption q con of the fuel cell stack is calculated by the following formula:

[0127]

[0128] Wherein, I is the current of the fuel cell, and N is the number of single cells in the stack.

[0129] S2-3. Calculate the heat transfer coefficient K2 of the heat exchanger:

[0130] The heat Q required for cooling the high-temperature and high-pressure air output by the air compressor ca is equal to the heat exchangeable with the exhaust gas of the stack, i.e.: ca_out Equal, that is:

[0131] Q ca = Q ca_out (13);

[0132] For the heat exchanger, there is the following relationship:

[0133]

[0134] Wherein, T c_out is the temperature at the outlet of the air compressor, which is measured by a temperature sensor arranged at the outlet of the air compressor; T ca_in is the inlet temperature of the cathode of the stack; T ca_out is the temperature when the exhaust gas exits the stack, which is measured by a temperature sensor arranged at the exhaust gas outlet of the stack; T ca is the temperature of the exhaust gas after being heated by the heat exchanger.

[0135] Substitute the calculated results in steps S2-1 and S2-2 into formula (13) to obtain the relationship between T ca_in and T ca , and substitute it into formula (14) to obtain the relationship between K2 and T ca_in .

[0136] The inlet temperature T ca_in of the cathode of the stack is determined by the temperature requirement at the inlet of the stack, generally between 60-80 °C, that is, according to the set required value of the inlet temperature T ca_in of the cathode of the stack, calculate the heat transfer coefficient K2 of the heat exchanger.

[0137] Based on the following two heat balances: the heat generated by the stack is equal to the latent heat of vaporization of the atomized liquid water for humidification, and the heat required for cooling the high-temperature and high-pressure air output by the air compressor is equal to the heat exchangeable with the exhaust gas of the stack, establish a mathematical model for the thermal management system of high-power fuel cells. By accurately calculating the heat of each part, clarify the heat source of the fuel cell thermal management, and then based on the two heat balances, calculate the heat transfer coefficient K1 of the plate heat exchanger and the heat transfer coefficient K2 of the heat exchanger respectively. Appropriately select the heat exchanger for the fuel cell system according to the heat transfer coefficient to ensure that the high-power fuel cell thermal management system can operate fully and effectively, reduce the fuel cell heat load, and provide conditions for realizing precise control of the fuel cell thermal management.

[0138] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-power fuel cell thermal management system, characterized in that, It includes a hydrogen source (1), a proportional valve (2), an air compressor (3), a heat exchanger (4), a water tank (5), an atomizer (6) and a plate heat exchanger (7); The hydrogen output from the hydrogen source (1) enters the anode of the fuel cell stack (8) after passing through the proportional valve (2); The high-temperature and high-pressure air output from the air compressor (3) passes through the heat exchanger (4), exchanges heat with the tail gas of the fuel cell stack (8) to cool down, and then enters the cathode of the fuel cell stack (8); The liquid water in the water tank (5) enters the atomizer (6) to form atomized liquid water, and then passes through the plate heat exchanger (7), exchanges heat with the high-temperature coolant circulating from the fuel cell stack into the plate heat exchanger (7) to increase the temperature. After the atomized liquid water vaporizes, it humidifies the hydrogen at the anode inlet and the air at the cathode inlet of the fuel cell stack (8) respectively.

2. A calculation method for the heat transfer coefficient of the high-power fuel cell thermal management system according to claim 1, characterized in that It includes the following steps: S1. Establish a mathematical model based on the heat generated by the fuel cell stack being equal to the latent heat of vaporization of the atomized liquid water for humidification, and calculate the heat transfer coefficient K1 of the plate heat exchanger; S2. Establish a mathematical model based on the heat required to cool the high-temperature and high-pressure air output from the air compressor being equal to the heat that can be exchanged by the tail gas of the fuel cell stack, and calculate the heat transfer coefficient K2 of the heat exchanger; S3. Select a plate heat exchanger and a heat exchanger that meet the requirements for use in the high-power fuel cell thermal management system according to the heat transfer coefficient K1 of the plate heat exchanger and the heat transfer coefficient K2 of the heat exchanger calculated in step S1.

3. The heat transfer coefficient calculation method of the high-power fuel cell thermal management system according to claim 2, characterized in that The step S1 includes: S1-1. Calculate the heat Q generated by the stack q ; The heat Q generated by the stack q is calculated by the following formula: Q q = C water * m water *(T s_in - T s_out ) (1); Where, C water is the specific heat capacity of the coolant of the plate heat exchanger, with a value of 4.2 KJ / kg / K; m water is the mass flow rate of the coolant of the plate heat exchanger, which is measured by a flow meter arranged at the inlet of the coolant of the plate heat exchanger; T s_out is the temperature at the outlet of the coolant of the plate heat exchanger, which is measured by a temperature sensor arranged at the outlet of the coolant of the plate heat exchanger; T s_in is the inlet temperature of the coolant of the plate heat exchanger.

4. The heat transfer coefficient calculation method of the high-power fuel cell thermal management system according to claim 3, characterized in that The step S1 also includes: S1-2. Calculate the latent heat of vaporization Q of the liquid water for humidification v : Latent heat of vaporization Q of liquid water for humidification v Calculated by the following formula: Q v = h water *(m an-water + m ca-water ) (2); where h water is the latent heat of vaporization enthalpy of water, with a value of 2550 KJ / kg; m an-water is the amount of water for anodic humidification; m ca-water is the amount of water for cathodic humidification.

5. The heat transfer coefficient calculation method of the high-power fuel cell thermal management system according to claim 4, characterized in that The anode humidification water volume m in the step S1-2 an-water is calculated by the following formula: where P water is the saturation pressure of water vapor at the current temperature; RH an is the humidity at the anode inlet, measured by a humidity sensor arranged at the anode inlet; P an is the pressure at the anode inlet, measured by a pressure sensor arranged at the anode inlet, is the inlet mass flow rate of hydrogen at the current current; The saturation pressure P of water vapor at the current temperature water is calculated by the following formula: In the formula, T is the temperature of the fuel cell stack. a, b, c, d, e, f are all coefficients related to the saturated vapor pressure of water vapor, and the specific values are: a = -5800.2206; b = 1.3914993; c = -0.048640239; d = 0.41764768E-4; e = -0.14452093E-7; f = 6.5459673; The intake mass flow rate of hydrogen at the current current Calculated by the following formula: In the formula, I is the current of the fuel cell, N is the number of single cells in the fuel cell stack, and t is the operating time of the fuel cell thermal management system.

6. The calculation method of the heat transfer coefficient of the high-power fuel cell thermal management system according to claim 5, characterized in that, The cathode humidification water volume m in the step S1-2 ca-water is calculated by the following formula: where P water is the saturation pressure of water vapor at the current temperature; RH ca is the humidity at the cathode inlet, measured by a humidity sensor arranged at the cathode inlet; P ca is the pressure at the cathode inlet, measured by a pressure sensor arranged at the cathode inlet, and q Air is the inlet mass flow rate of air at the current current; The intake mass flow rate q of air at the current current Air is calculated by the following formula: Wherein, I is the current of the fuel cell, N is the number of single cells in the stack, t is the operating time of the fuel cell thermal management system, and λ Air is the air stoichiometry ratio, and λ Air is artificially set as required, and is the molar mass of oxygen.

7. The heat transfer coefficient calculation method of the high-power fuel cell thermal management system according to claim 6, wherein The step S1 also includes: S1-3. Calculate the heat transfer coefficient K1 of the plate heat exchanger: The heat Q generated by the stack q is equal to the latent heat of vaporization Q of the liquid water for humidification v That is: Q q = Q v (8); For the plate heat exchanger, there is the following relationship: Q v = K1 * (T s_in - T s_out ) (9); where T s_out is the temperature at the coolant outlet of the plate heat exchanger, which is measured by a temperature sensor arranged at the coolant outlet of the plate heat exchanger; T s_in is the inlet temperature of the coolant of the plate heat exchanger; Substitute the calculated results in Step S1-1 and Step S1-2 into Formula (8) and Formula (9) to obtain two equations with two unknowns, where the unknowns are K1 and T respectively s_in , and calculate the value of the heat transfer coefficient K1 8. The calculation method of the heat transfer coefficient of the high-power fuel cell thermal management system according to claim 1, wherein, The step S2 includes: S2-1. Calculate the heat quantity Q required for cooling the high-temperature and high-pressure air output by the air compressor ca : Q ca = q Air * C Air *(T c_out - T ca_in ) (10); where q Air is the intake air mass flow rate at the current current, calculated by formula (7); C Air is the specific heat capacity of air, with a value of 1.004 KJ / kg / K; T c_out is the temperature at the outlet of the air compressor, measured by a temperature sensor arranged at the outlet of the air compressor; T ca_in is the inlet temperature of the cathode of the fuel cell stack.

9. The heat transfer coefficient calculation method of the high-power fuel cell thermal management system according to claim 3, characterized in that The step S2 also includes: S2-2. Calculate the heat exchange quantity Q of the tail gas of the stack ca_out : Q ca_out = (q Air - q con ) * C Air * (T Ca - T ca_out ) (11); where q Air is the intake mass flow rate of air at the current current, calculated by formula (7); q con is the air consumption of the fuel cell stack; C Air is the specific heat capacity of air, with a value of 1.004 KJ / kg / K; T ca_out is the temperature of the tail gas when it exits the fuel cell stack, measured by a temperature sensor arranged at the tail gas outlet of the fuel cell stack; T ca is the temperature of the tail gas after being heated by the heat exchanger; The air volume q consumed by the stack con is calculated by the following formula: In the formula, I is the current of the fuel cell, and N is the number of single cells in the fuel cell stack.

10. The heat transfer coefficient calculation method of the high-power fuel cell thermal management system according to claim 2, wherein, The step S2 also includes: S2-3. Calculate the heat transfer coefficient K2 of the heat exchanger: The heat Q required for cooling the high-temperature and high-pressure air output by the air compressor ca The heat exchangeable quantity Q with the tail gas of the stack ca_out is equal, that is: Q ca = Q ca_out (13); For the heat exchanger, there is the following relationship: Where, T c_out is the outlet temperature of the air compressor, which is measured by a temperature sensor arranged at the outlet of the air compressor; T ca_in is the inlet temperature of the cathode of the stack; T ca_out is the temperature when the tail gas exits the stack, which is measured by a temperature sensor arranged at the exhaust outlet of the tail gas of the stack; T ca is the temperature of the tail gas after being heated by the heat exchanger; Substitute the calculated results in steps S2-1 and S2-2 into formula (13) to obtain T ca_in and T ca to obtain the relational expression between them, and substitute it into formula (14) to obtain the relational expression about K2 and T ca_in ; The inlet temperature T of the cathode of the stack ca_in It is determined by the temperature requirement at the inlet of the stack. According to the set inlet temperature T of the cathode of the stack ca_in demand value, the heat transfer coefficient K2 of the heat exchanger is calculated.

Images