Simulation of pool boiling regimes for a sphere using a hydrogen evolving system

Abstract

Pool boiling phenomena for a sphere were simulated by electrical reduction of hydrogen in an aqueous solution of sulfuric acid (H2SO4), with copper and stainless steel(SUS316L) spheres used as the cathode. The cell potential and current density, which correspond to superheat and heat flux were controlled, respectively. The cell potential–current density curve from nucleate to transition bubble regimes was analogous to the typical boiling curve. In addition, the hydrogen bubble behaviors in each bubble regime, observed using a high-speed camera, were also similar to the vapor behaviors in boiling systems, except for the difference in bubble size. The critical current density (CCD) was determined similarly to the determination of critical heat flux (CHF). The calculated CHF values, based on the measured CCDs, were smaller than the CHF values of the boiling system due to the bubble volume. The CCD value increased with decreasing sphere diameter due to the increasing bubble frequency. In conclusion, the hydrogen evolving system can reasonably simulate the boiling regime for a sphere.