STUDY OF TRANSIENT TRANSITION BOILING HEAT FLUXES FROM SPHERES SUBJECTED TO FORCED VERTICAL FLOW
Experimental observations of transient boiling heat fluxes have been made by quenching 19 mm diameter copper and silver spheres in a stationary or a moving vertical column of distilled water. In the reported experiments water subcooling has been varied from 0 to 60K while the flow velocity past the spheres has been varied from 0 to 45 cm/sec. Use of spheres of different materials but of the same size allows the determination of the effect of thermal capacity of the sphere on the nature of the transient and in turn on the maximum heat flux. The transient critical heat fluxes are observed to increase non-linearly with liquid subcooling as opposed to the known linear dependence of the steady state heat fluxes on liquid subcooling. The non-linearity is seen to increase with the magnitude of the (maximum) heat flux which itself depends on the liquid subcooling, flow velocity and thermal capacity of the sphere.