EVAPORATIVE COOLING DUE TO A SPARSE SPRAY

The cooling effect of a sparse spray impinging on a semi-infinite soli d is investigated. Experiments are conducted by monitoring (via infrar ed thermography) the surface of the solid heated by radiation and cool ed by sprays of uniform size droplets until steady-state conditions ar e reached. The surface temperature field in the proximity of a single droplet is modeled with a closed-form solution based on the hypothesis of constant and uniform heat flux at the solid-liquid interface. In t he far-field, an instantaneous point-sink solution is adequate to repr esent a single droplet cooling effect. These closed-form solutions are used to fit the results of a coupled model previously developed, whic h solves the liquid and solid temperature fields for the evaporative t ransient. Inputs from this model are necessary for the formulation of both the closed-form solutions. The spray model formulation is based o n the superposition of the cooling effect of all the droplets deposite d on the surface. The transient surface temperature distributions and die average surface temperature are compared for the data and computat ions. The results are in good agreement for similar random droplet dis tributions of the order of 1 g/m(2)/s with initial solid surface tempe ratures ranging between 130 and 160 degrees C. (C) 1997 Elsevier Scien ce Ltd.