An investigation of the stagnation point heat transfer coefficient of such a single-phase, microscale impinging jet is discussed. Standard MEMS processes were used to fabricate a heat transfer measurement device. In this device, a water jet issued from a 67-μm orifice and impinged on an 80-μm square heated normal surface 200 μm from the orifice. Heat transfer coefficients up to 80,000 W/m2-K were measured. This heat transfer coefficient results in a heat flux greater than 400 W/cm2 given a 50°C temperature difference. However, this heat transfer coefficient is an order-of-magnitude less than that predicted by correlations developed from larger jets. In addition, the heat transfer coefficients were relatively insensitive to Reynolds number. Further investigation of microjet heat transfer is needed to explain this deviation from expected behavior. The pressure drop across the jet orifice was measured, and the calculated pressure loss coefficients agree well with available correlations. Curve fits for the Nusselt number and pressure loss coefficient are given.

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