Local heat transfer in a microchannel with a pin fin—experimental issues and methods to mitigate

•Local heat transfer downstream a single pin fin in a microchannel was experimentally studied.•The interaction between the flow structure and the local heat transfer was revealed.•An interplay of fluid convection and solid substrate conduction was discovered and explained.•Numerical simulation was used to resolve the local heat transfer coefficient. Local heat transfer downstream a single pin fin in a microchannel was experimentally studied by incorporating an array of micro resistance temperature detectors (RTD) (∼55μm×55μm) on the internal microchannel surface. Local temperature distribution with spatial resolution as high as 150μm was obtained and was superimposed onto the velocity field to reveal the interaction between the flow structure and the local heat transfer at different regions downstream the pin fin. Initial result in which the surface temperature inside the steady wake region was lower than in the regions outside the recirculation zone was explained and linked to an interplay of fluid convection and solid substrate conduction. Ignoring this local interplay and processing the data without careful consideration to the conduction process resulted in misinterpretation of the heat transfer processes. To address this issue numerical thermal and fluid model of the entire device was simulated to provide local heat flux distribution. This in turn allowed to resolve the local heat transfer coefficient in the vicinity, and outside the region, of the pin fin.