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Summary: In the past decade, nanofluids have proven effective for heat transfer enhancement of many thermal engineering applications. This is due to their superior thermal performance characteristics compared with conventional coolants. Therefore, the adoption of nanofluids as alternative coolants in proton exchange membrane fuel cell (PEMFC) cooling systems is considered a novel technology and a promising contributor to the solution of thermal management problems that are impeding the commercialization of automotive PEMFC engines. In this article, the thermal performance enhancement of a radiator was experimentally investigated through the addition of Zinc oxide (ZnO) and aluminum nitride (AlN) nanoparticles suspended in a 50/50 mixture of water and ethylene glycol (WEG) as the base fluid for automotive PEMFC cooling systems. The nanofluid concentrations of 0.2 wt% and 0.5 wt% from nanoparticles were used, and the inlet temperature range of the nanofluids was 50°C to 80°C. The experimental results indicate that the heat transfer rate and radiator effectiveness were improved with high flow rates of the base fluid and nanofluid. Furthermore, by increasing the mass concentration of nanoparticles, the heat transfer rate, overall heat transfer coefficient, and radiator effectiveness were enhanced. This can be explained by the significant enhancement of thermal conductivity and Brownian motion benefited from nanofluids. Compared with the base fluid, the heat transfer rate increased by 24.3% and 57.7% at concentrations of 0.2 wt% and 0.5 wt% ZnO nanoparticles, respectively, within the considered temperature range. Meanwhile, the AlN/WEG nanofluids enhancements achieved 15.3% and 30.7% at the same concentrations. In conclusion, the use of ZnO nanoparticles is strongly recommended for suspension in the WEG (50/50 v/v) mixture as a proper coolant for better performance of PEMFC‐based engines. [ABSTRACT FROM AUTHOR]

Summary: To answer how surface corrosion affects the heat transfer performance of phase‐change immersion cooling solar cells, electrochemical etching was used for substrate surface treatment of simulated dense‐array solar cells in this paper. Morphology, roughness, and wettability of treated surfaces were characterized by scanning electron microscope, atomic force microscope, and spreading area, respectively. A self‐running cooling system was developed to investigate the effect of surface treatment on self‐running characteristics and heat transfer performance under different ethanol inlet temperatures and concentration ratios. The results show that the surface treated for 2 hours owns higher wettability because of the honeycomb‐like porous structure. Lower ethanol flowing velocity obtained under lower ethanol inlet temperature with treated samples. The maximum declined degree in the wall superheating of 21.1% and the maximum enhancement in the heat transfer coefficient of 33.3% are obtained for sample treated for 2 hours because of its higher wettability and porosity structure. The results show that electrochemical etching on substrate surface can improve the phase‐change immersion cooling performance of solar cells. [ABSTRACT FROM AUTHOR]