Analytical and numerical study on cooling flow field designs performance of PEM fuel cell with variable heat flux

Abstract

In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models.

Numerical thermal analysis of nanofluid flow through the cooling channels of a polymer electrolyte membrane fuel cell filled with metal foam

“…Since the current density in the fuel cell is not uniform, the heat flux will change along the cell. According to the reported data of Reference , this linear variation is represented by: where x is the distance (m) in the flow direction. The geometrical parameters, the value of heat flux imposed on the cooling surface and its variations, the flow rate of coolant, etc.…”

“…However, in practice, this heat flux is not constant and is a function of local current density of the fuel cell. Here, we derive the data of cell current density curve from Reference and impose a variable heat flux on the cooling plate. We investigate the effects of porosity, pore size and thickness of metal foam, as well as nanoparticles volume fraction, on the cooling system efficiency.…”

Metal foam as a turbulent flow distributor in the cooling channels of a PEM fuel cell—a numerical study

“…We simulate the heat flux imposed to the cooling plate as a variable heat flux distribution, similar to the form of the heat generated in a real PEM fuel cell. The experimental data are obtained from [29]. It is found that the thermal flux changes linearly along the channel length according to the following equation:…”

Optimization of Cooling Channel Structure of Bipolar Plate for Proton Exchange Membrane Fuel Cells Based on CFD Analysis

“…For instance, Ebrahim Afshari and his team [11] conducted a study on the coolant flow and heat transfer in the cooling plates of proton exchange membrane fuel cells. They evaluated and compared the performance of four different coolant flow fields, including simple parallel channels and serpentine channels with one and two parallel channels, based on the maximum surface temperature, uniform temperature distribution, and pressure drop.…”