Dynamic characteristics of transient boiling on a square platinum microheater under millisecond pulsed heating

A series of experimental investigations of boiling incipience and bubble dynamics of water under pulsed heating conditions for various pulse durations ranging from 1 ms to 100 ms were conducted. Using a very smooth square platinum microheater, 100 mu m on a side, and a high-speed digital camera, the boiling incipience was observed and investigated as a function of the bulk temperature of the microheater, pulse power level, and pulse duration. Given a specific pulse duration, for low pulse power levels, there would be no bubble nucleation or bubble mergence, for moderate pulse power levels, individual bubbles generated on the heater merged to form a single large bubble, while for high pulse power levels, the rapid growth of the individual bubbles and subsequent bubble interaction, resulted in a reduction in bubble coalescence into a single larger bubble, referred to as bubble splash. The transient heat flux range at which bubble coalescence occurs was identified experimentally, along with the temporal variations of bubble size, bubble interface velocity and interface acceleration. (C) 2007 Elsevier Ltd. All rights reserved.