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Abstract. Forced convection uid ow and heat transfer were investigated in a porous channel with expanding or contracting walls, which was lled with Al2O3-Cu/water micropolar hybrid nano uid in the presence of magnetic eld. In order to solve the governing equations analytically, the least square method was employed. The hot bottom wall was cooled by the coolant uid, which was injected into the channel from the top wall. The range of nanoparticles volume fraction (90% Al 2 O 3 and 10% Cu by volume) was between 0% and 2%. The e ects of consequential parameters such as Reynolds number, Hartmann number, micro rotation factor, and nanoparticles volume fraction on velocity and temperature pro les were examined. The results show that with increasing Reynolds number, the values of temperature and micro rotation pro les decrease. Furthermore, when the hybrid nano uid is used, compared to common nano uid, the heat transfer coe cient will increase signi cantly. It is also observed that when the Hartmann number increases, Nusselt number increases, too.

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In the present investigation, the effects of inner diameter and length of porous wall on flame stability limits, temperature distribution, methane conversion, and pressure drop in a premixed burner are numerically analyzed. The governing equations are solved by the control volume method, considering Re-Normalization Group k-ɛ for turbulence modeling and eddy dissipation concept for turbulence–chemistry interaction modeling. The simulations are performed for various porous walls with the inner diameter of 30, 40, and 50 mm and the length of 22, 44, and 66 mm. The results demonstrate that the increase in inner diameter of porous wall causes an increase in the lower flame stability limit and a decrease in the upper flame stability limit, gas and solid temperatures, pressure drop, and methane conversion. Also, the maximum solid and gas temperatures in the porous wall and methane conversion are related to the porous wall with 44 mm length. Furthermore, the methane conversion and pressure drop increase with the rise in the equivalence ratio. Finally, it can be said that the change in inner diameter of porous wall is more important than the length of porous wall in the studied phenomena.