Research On Output Characteristics Of Proton Exchange Membrane Fuel Cell Stacks With Ultra-thin Vapor Chambers And Multiple Gas Supply Means

As a high-efficiency energy conversion device,the proton exchange membrane fuel cell has the potential of zero emissions,which is of great significance for our country to achieve the goal of peak carbon dioxide emissions and carbon neutrality.However,problems such as large temperature difference in the in-plane,uneven component distribution,and flooding seriously affect the output characteristics of proton exchange membrane fuel cells and limit their large-scale application.In response to the above-mentioned problems that need to be solved,theoretical analysis,experimental verification and numerical simulation methods are used to study the output characteristics of proton exchange membrane fuel cells in this paper,focusing on the high thermal conductivity of ultra-thin vapor chambers and its uniform temperature effect,and multi-channel gas supply improves the flow distribution of each single cell and the uniformity of internal component distribution.The heat transfer process of ultra-thin vapor chambers used in the thermal management of proton exchange membrane fuel cell stacks is analyzed.The relationship between the temperature difference in the contact plane of the ultra-thin vapor chamber and the fuel cell flow field plate and the equivalent thermal conductivity of the ultra-thin vapor chamber is obtained.It is found that the temperature difference is inversely proportional to the equivalent thermal conductivity.The relationship between temperature difference and heat conduction distance is quadratic.The relationship between the thickness of the wick,the thickness of the vapor chamber and the heat transfer performance of the ultra-thin vapor chamber is studied from the two aspects of the total thermal resistance and the flow pressure loss of the internal working fluid.The total thickness of the ultra-thin vapor chamber is determined to be 1.5 mm.A thermal resistance network model of the combination of the ultra-thin vapor chamber and the proton exchange membrane fuel cell is established.It is found that the contact thermal resistance is the main factor affecting the temperature distribution and the maximum temperature in the through-plane.The ultra-thin vapor chamber and the graphite flow field plate are combined into a composite bipolar plate(the equivalent thermal conductivity is 7415?16025W/(m K)),and then combine it with membrane electrode assemblies to to form a proton exchange membrane fuel cell stack for experiment.The effect of ultra-thin vapor chambers on the output characteristics of proton exchange membrane fuel cell stacks under different heat dissipation conditions is studied.When the condensing section of the ultra-thin vapor chamber adopts the forced convection heat dissipation method,the temperature distribution on the cathode gas diffusion layer surface of the single cell in the ultra-thin vapor chamber fuel cell stack is more uniform;when the average cell voltage is 0.643 V,the temperature difference on the cathode gas diffusion layer surface of the single cell in the ultra-thin vapor chamber fuel cell stack is reduced to 0.4?;when the current density is 0.5 A/cm~2,the average cell voltage of the open cathode fuel cell stack with ultra-thin vapor chamber is 9.0%higher than that of the fuel cell stack without ultra-thin vapor chambers.A theoretical model for the uniformity of hydrogen flow distribution is established,and the results show that the multi-gas path setting can improve the uniformity of hydrogen flow distribution.The multi-gas path setting can also change the distribution of reaction gases and the water in flow channels,which improves the output performance of proton exchange membrane fuel cell stacks.For example,when the current density is 0.6 A/cm~2,compared with the output voltage of the U-shaped single-way hydrogen supply mode,the output voltage of the ultra-thin vapor chamber fuel cell stack in the dual,triple and quad hydrogen supply mode is increased by 4.08%,4.50%and 5.06%,respectively.The multi-gas path hydrogen supply setting improves the uniformity of hydrogen flow distribution and the uniformity of the cell voltage of each cell in the proton exchange membrane fuel cell stack.The output voltage and internal composition distribution of the proton exchange membrane fuel cell with alternating air flow directions and dual hydrogen supply mode are studied by experimental and numerical simulation methods.Alternating air flow directions and dual hydrogen supply mode can increase the output voltage of the fuel cell stack;alternating air flow directions can improve the water distribution in the cathode flow channel,increase the water content in the fuel cell,and improve the wettability of the membrane;the hydrogen mass fraction in the downstream of anode channels can be increased by the dual hydrogen supply mode.