サブクール沸騰高熱流束域における伝熱面近傍の気液構造(熱工学,内燃機関,動力など)

概要

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A conductance probe method with high accuracy was developed to measure liquid-vapor structure at high heat flux in the vicinity of boiling surface. The probe with tip diameter below 5μm was made using electro-polishing technique. Measurements were carried out for water boiling on an upward-facing copper surface in the range of subcooling 0K to 30K. The probe signals were acquired in a pulse analysis system where the width and arrival time of each of continuous probe signals were recorded. Measured void fraction and the probe signals show that there is little difference in liquid-vapor structure between saturated and subcooled boiling and that a liquid rich layer rests beneath large coalesced bubbles in the range of heat fluxes up to 3.5MW/m^2. The interface of the liquid rich layer was determined from the location where the probe signals corresponding to the large coalesced bubbles disappear. The thicknesses of the liquid rich layer formed in subcooled boiling are comparable to or thicker than those formed near the critical heat flux in saturated boiling, and this is most likely one of the causes that the CHF increases with the increase in subcooling.
社団法人日本機械学会の論文
2004-11-25