Liquid-solid contact and its relationship to improved film boiling heat transfer rates

The possible improvement of film boiling heat transfer through the use of surface macro-roughness elements is the subject of the present study. A macro-roughened heating surface was fabricated with a flush-mounted micro-thermocouple in the protruding end of one of the macro-roughness elements. The temperature measurements obtained from this micro-thermocouple indicated that intermittent, direct liquid-solid contact occurred between the boiling liquid and the instrumented macro-roughness element at bulk surface temperatures significantly above the smooth surface minimum film boiling temperature. The boiling heat transfer on the macro-roughened surface was found to be as much as 500 percent greater than that measured for the same liquid on a smooth surface at the same bulk surface temperature.