Effects of surfactant additive on flow boiling over a microheater under pulse heating

An experimental investigation has been carried out to study effects of surfactant additive on microscale boiling under pulse heating over a Pt microheater (140 × 100 μm2) fabricated in a trapezoidal microchannel (600 μm in width and 150 μm in depth). Experiments are carried out for six different surfactant concentrations of Triton X-100 ranging from 47 ppm to 2103 ppm, for mass flux in the range from 45 kg/m2 s to 225 kg/m2 s, pulse width in the range from 50 μs to 2 ms, and heat flux in the range from 3 MW/m2 to 65 MW/m2. As in existing work on pool boiling under steady heating, it is found that nucleate boiling becomes more vigorous and heat transfer is enhanced greatly with the addition of surfactant with maximum boiling heat transfer occurs at the critical micelle concentration (cmc). Furthermore, these maximum values of boiling heat transfer coefficient increase with decreasing pulse width. When concentration is below cmc, the heat flux needed for nucleation increases with increasing concentration and the nucleation temperature is reduced. When concentration is higher than cmc, the boiling heat transfer coefficient decreases and nucleation temperature is higher than that of pure water.