- Local temperature measurements were made in a microchannel jet impingement cooling system with a single slot jet ( D h = 68 µm and standoff distance of 210 µm). A 40%/60% solution of propylene glycol in deionized water was used as the working fluid. Resistance temperature detectors ( RTD s) were fabricated over a rectangular heater of size 1500 µm × 400 µm allowing local temperature measurements. Nominal heat fluxes ranged between 50 W/cm 2 and 150 W/cm 2 , and jet Reynolds numbers were in the range of 122–435. A three-dimensional conduction/convection conjugated numerical model with laminar and turbulent variants was developed to predict the jet hydrodynamics and heat transfer process. Good agreement was achieved between the model and the experimental data in terms of flow coefficients and local wall temperatures. Furthermore, a generalized Nusselt number dependence on Reynolds number was formulated, taking into account the temperature-dependent viscosity of the working fluid. The results provide valuable information about local and surface-averaged heat transfer due to a flow field generated by an impinging micro slot jet.