Dropwise Cooling: Experimental Tests by Infrared Thermography and Numerical Simulations

In this paper, infrared thermography is used to measure the transient contact temperature between impinging droplets and hot solid surfaces. Droplets are released onto the heated solid surface of a barium fluoride (BaF2) disk, which has a high transmittance (about 90%) in the 8–12 um range (typical of longwave infrared cameras). The interface temperature is measured from below, through the solid material, by infrared thermography. Since the solid is IR-transparent, a black coating layer is used to allow radiative heating of the surface and provide a method to measure the liquid–solid interface temperature. A numerical code is then presented, which simulates the evaporation of water droplets on hot solid surfaces. At the present stage of development, single-phase evaporation is addressed. The three-dimensional energy diffusion equation, discretized using the finite volume method, is employed to model the transient within both the droplets and the solid substrate. The numerical results are validated by comparison with the experimental data.