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Local single-phase flow heat transfer downstream a single pin fin in a microchannel was experimentally and numerically studied. Three distinct flow regimes, depending on the Reynolds number, were characterized, namely: laminar flow with steady wake, laminar flow with unsteady wake, and turbulent flow. Local temperature measurements with high spatial resolution were obtained by incorporating an array of micro resistance temperature detectors (RTDs) (∼55 µm × 55 µm) on the internal microchannel surface. Local surface temperatures were related to the flow structures under different flow regimes. An enhanced local heat transfer coefficient at the trailing edge of the wake region downstream the pillar was observed. It is believed to be a result of vortex shedding and large-scale flow mixing triggered by flow instability at high Reynolds number. The numerical model enabled a full conduction/convection conjugate analysis of the entire system including heat conduction within the solid substrates and heat losses to the surrounding environment. Local heat transfer coefficient downstream the pin fin at each Reynolds number was obtained. [ABSTRACT FROM AUTHOR]

Local heat transfer downstream a single pin fin in a microchannel was experimentally studied by incorporating an array of micro resistance temperature detectors (RTD) (∼55 μm × 55 μm) on the internal microchannel surface. Local temperature distribution with spatial resolution as high as 150 μm 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. [ABSTRACT FROM AUTHOR]