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In this study, a three-dimensional and non-isothermal model of a polymer electrolyte membrane (PEM) fuel cell according to the multiphase mixture method was employed to analyze the influence of microporous layer (MPL) characteristics on water saturation and fuel cell performance. The modeled domain is divided into several regions comprising bipolar plate, gas channels, gas diffusion layers (GDLs), catalyst layers and polymer electrolyte membrane. A microporous layer has been sandwiched between the cathode GDL and the catalyst layer. In order to validate the model, the results were compared with the experimental data and a good agreement was observed. The results show that by placing the microporous layer between GDL and catalyst layer, a discontinuity appears in the liquid saturation and the species concentration at the contact surface of the layers. Therefore, the liquid water distribution in porous layers alongside the performance of the fuel cell largely depends on both structural and wetting properties of MPL. According to the results obtained, increasing the MPL porosity leads to decrease in the liquid water saturation, thereby improving the cell performance, while increasing the MPL thickness reduces the cell performance. Moreover, an MPL with a higher contact angle and gas permeability enhances the fuel cell performance due to the facilitation of water removal and reactant transport.

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In this study, a numerical study is performed on the cooling phenomenon of three heat source electronic devices. The electronic devices are cooled in the form of natural heat transfer by the airflow in a porous medium. Electronic devices are installed on the boundary walls of a square environment. Cooling simulations are performed by drawing flow lines and constant temperature lines. Our main goal is to find the highest cooling rate in different Darcy numbers and different Rayleigh numbers in our investigation. The range of Darcy numbers and Rayleigh numbers is between 0.0001 to 0.01 and 1000 to 100,000, respectively. Our investigation showed the maximum cooling is obtained at the Darcy number of about 0.01. And also, by decreasing the value of Darcy number, a higher cooling rate for the hot boundary walls is achieved.