The effect of the liquid motion induced by air and vapor bubbles on heat transfer around a cylinder

This paper reports on a study into the effects of bubble-induced motion on heat transfer around a cylinder. Local heat flux due to vapor or air injected bubble motion is measured at different positions around a heated copper cylinder using a hot film technique as well as a heat flux sensor. The first set of experiments, carried out during the first stages of nucleate boiling, showed a dependence of the heat transfer on surface orientation. A similar conclusion was reached in the second set of experiments where the air bubbles were injected using an external source. Average heat flux values computed in the two cases on the upper part of the cylinder were shown to compare relatively well. Finally, the mechanisms involved in the heat transfer enhancement at the same location, on the upper part of the cylinder, in the two sets of experiments are described using a. simultaneous analysis of the heat flux time-series and bubble motion. (C) 2004 Elsevier Ltd. All rights reserved.