FORCED-CONVECTION BOILING FROM A NONFLUSH SIMULATED ELECTRONIC CHIP

An experimental investigation has been undertaken to determine the eff ect of heated surface height on forced convective boiling. An inert fl uorocarbon, FC-72 (3M Industrial Chemical Products Division) is circul ated through a vertical rectangular channel at velocities of 1-4 m/s a nd subcoolings of 20 and 35-degrees-C. Results for five surface height s, as measured relative to the flow channel wall, were obtained. These were 0.127-mm recessed, 0.229-, 0.457-, and 0.635-mm protruded and fl ush with the flow channel wall. A reduction in critical heat flux (CHF ) occurred at low velocities, while an increase occurred at higher vel ocities for the protruded cases. A reduction of CHF occurred at all ve locities for the recessed condition. Additional results in the velocit y range of 5-7 m/s are presented for the flush condition. This data sh ows that for velocities greater than 4 m/s, CHF becomes weakly depende nt on the Weber number. Weak dependence on Weber number also implies a direct proportionality to velocity and a weak dependence on heated le ngth.