TED-AJ03-193 EFFECT OF "INTERFACIAL VAPORIZATION HEAT SINK" IN PROCESS OF FLOW BOILING WITH INTRODUCTION OF INERT GAS

概要

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Flow boiling heat transfer in a vertical annulus with inner side heated with and without air introduction is experimentally studied. The results show that boiling heat transfer is significantly enhanced by the introduction of air. When air is introduced into the liquid with a temperature below boiling point, the enhancement of heat transfer is also detected. The mechanism of such an enhancement of heat transfer is analyzed, and the major effect is attributed to the effect of interfacial vaporization heat sink caused by air introduction. Recently, several papers have been published concerning the heat transfer enhancement by air injection. The mechanism of such an enhancement effect is attributed to the turbulence increase caused by the injected air bubbles, and the related suppression of the laminarization effect in the near wall region. In this paper, it is likewise analyzed with the concept of the effect of interfacial vaporization heat sink. It is concluded from the results of the study that the heat transfer enhanced by introduction of inert gas is due to the liquid vaporization at the gas-liquid interface near the wall, which removes a large amount of latent heat and lowers the interfacial temperature considerably. Thus the gas-liquid interface acts as a "heat sink" and heat transfer is augmented significantly.
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