The Heat-Transfer Characteristics of a Small Droplet Impinging upon a Hot Surface

Abstract

The purpose of this paper is to obtain fundamental information concerning the heat transfer process and breakup behavior characteristics of individual small droplets impinging upon a hot surface. A uniform sized water droplet array at room temperature under atmospheric pressure was produced by the vibratory method to impinge upon a heated flat copper surface. And then, heat transfer from a surface to the droplets is assessed by a transient technique. Further, the deformation and the breakup behavior owing to the impingement of the droplet is observed by means of a drum camera recording high-speed microscopic photographs. Heat transfer effectiveness in a low temperature range of less than 125°C decreases as droplet impingement frequency increases because of interference between the impinging droplet and the remaining liquid film on a surface. It is possible that heat transfer per droplet is transfermed into a heat transfer coefficient by use of droplet residence time and film contact area on a surface. And Variations in the heat transfor coefficient for a droplet array with surface temperature are measured by difference calculus of the one dimensional unsteady heat conduction equation.