Experimental study on subcooled flow boiling heat transfer of water-SDS mixtures in a vertical macrochannel

Flow boiling heat transfer performance of surfactant solutions is studied at a basis of deionized water. The tested fluids are aqueous solutions of SDS at concentrations ranging from 100 to 12500 ppm. Tests are performed at vertical, upward, 3 x 40 mm cross-section channel at 75 degrees C subcooling, atmospheric pressure, flow rates 200-300 kg/m2s (Re: 1400-2600) and heat fluxes 200-1000 kW/m2. The present experimental data show that the trend of heat transfer enhancement follows the opposite direction of surface tension trend when surfactant concentration increases. At CMC (Critical Micellar Concentration) heat transfer coefficient and bubble density take their maximum value, while bubble diameter takes its minimum value. Concentrations above CMC show minimal or no further effect on flow boiling heat transfer characteristics. The tendency of the heat transfer coefficient experimental data with respect to changes in surfactant concertation allows the development of a modified version of the well-known two phase model heat transfer of Shah, by incorporating a surfactant con-centration dependent correction factor that predicts this work's values at a +/- 10% margin and a mean absolute percentage error of 3.6%.