The effects of oil/MWCNT nanofluids and geometries on the solid oxide fuel cell cooling systems: a CFD study

Abstract

In this numerical study, the variations in the surface area of the cooling channels in a solid oxide fuel cell with different cross sections and multi-walled carbon nanotubes oil/MWCNT nanofluid volume fractions are considered. Rectangular, trapezoidal and elliptical cross sections, and nanofluid volume fractions of 0–6% for the fluid are chosen as the studied parameters as well as the mass flow rates. In this research, a 3D model is developed by the finite volume method using the computational fluid dynamics (CFD). Then, the flow field and the heat transfer rate are predicted. The results show that the dissipated heat in the fuel cell is dependent on the mass flow rate of the fluid. That increased heat increases the heat transfer rate. The presence of the solid particles can also reinforce the heat conduction of the coolant fluid and consequently improve the heat transfer performance. The pumping power is maximum for the highest mass flow rate and the highest solid nanoparticle volume fractions. Additionally, the pumping power is dependent on the route in which the sections with lowest momentum changes and lowest pressure drops have the least amount of the pumping power. The ratio of the dissipated heat by the nanofluid over the base fluid is compared to a pressure drop. The movement of flow with the lower mass flow rates will result in penetrations of the thermal boundary layers into different flow regions, which can increase the optimum temperature in the solid part of the fuel cell. By increasing the mass flow rate of the fluid passing through the channels from 0.002 to 0.004 kg s−1, the maximum temperature is decreased by 6.13, 3.34 and 6.35% for rectangular, trapezoidal and elliptical channels, respectively.