Bubble Growth and Fission on MEMS Heat Transfer Surfaces under Subcooled Boiling Conditions(Thermal Engineering)

Abstract

Highly subcooled boiling at high heat flux results in emission of microbubbles from boiling bubbles. This paper proposes a new MEMS heat transfer surface to generate single boiling bubbles in ideal situations and to observe the bubble growth and fission. The surface has seven thermocouples for temperature measurement and nickel electrodes for hydrogen generation, and back-side thin film heaters for transient heating. In a stagnant water pool, the heater makes superheated liquid layer and a hydrogen bubble triggers growth of a boiling bubble. Thermocouple signals reveal evaporation of liquid layer, dryout, and rewetting. Dependence of bubbling feature on heat flux and heating time during highly subcooled boiling is summarized as a bubbling pattern map. Under the conditions of high heat flux, and long heating time, growing bubbles largely deform and generate tiny bubbles from their top part.