Explosive Vaporization of Ethanol on Microheater during Pulse Heating

Abstract

The article is devoted to the research of transient heat transfer, explosive vaporization and condensation in subcooled ethanol on microheater during pulsed heating. Experiments were performed using high-speed infrared thermography and visualization for various initial liquid temperatures 30–60 °C and heat fluxes in the range of 3.3–7.8 MW/m2. The evolution of temperature field of the microheater and liquid during transient heating and the nucleation temperatures for different heat fluxes and liquid subcooling were determined. It was shown that the nucleation temperature was almost independent on heating power and amounted to 194 °C, which is close to the calculations based on homogeneous nucleation theory. New experimental data were obtained on the times of convection and boiling onset, evolution of vapor bubbles, including the dependence of their maximum sizes on the heat flux and initial liquid temperature. It was shown that the maximum bubble size decreases with an increase in the heat flux and liquid subcooling, varying in the same range as for water. It was demonstrated that at low heat fluxes, during condensation, a liquid funnel was formed at the bubble top, which resembled the formation of a liquid jet during the collapse of cavitation bubbles.