High Power Density Dissipations by Spray Cooling

An experimental set up is developed to deliver monodisperse microdroplets at different volumetric flows over a hot surface. In-house built circuitry activates a Thermal Ink Jet (TIJ) atomizer to spray controlled amounts of deionized water to cool a small area of 5 mm by 3 mm on a copper block. The temperature history is monitored through K-type thermocouples and the dissipated power is calculated using Fourier’s law. Digital cameras are used to track the wetted area unveiling considerable changes in the wetted area present close to the CHF. The controlled flow delivery and small droplets (50 μm diameter) result in small wetted areas near the CHF. The wetted area is measured and used to compute the dissipated heat. Experimental results show dissipation of heat fluxes up to 4 kW/cm² based on the best estimate of the wetted area.