A STUDY OF THE MECHANISM OF BOILING HEAT TRANSFER

Abstract

Part I. An Experimental Study of Partial and Complete Film Boiling with Forced Convection. An apparatus was developed to investigate the regions of peak heat flux, partial film boiling, and complete film boiling. High-speed motion pictures and experimental data were taken to study the effects of liquid velocity, pressure, and temperature on the boiling heat transfer in subcooled-distilled-degassed water. The motion pictures showed the types of vapor formation which occur in each of the three regions and indicated that the heat transfer at the transition from nucleate boiling to partial film boiling was about 90 per cent of the peak heat flux. Part II. A Detailed Photographic Study of Nucleate Pool Boiling. The dynamics of nucleate bubbles in aerated and degassed liquids was studied by means of high-speed motion picture cameras. A mechanism is proposed for the growth and collapse of nucleate bubbles which successfully predicts the effects of liquid properties and conditions on bubble dynamics. The liquids chosen for this study were distilled water and carbon tetrachloride because of their widely different physical properties. The influence of surface tension on the bubble dynamics was investigated separately by adding a surface-tension depressor to the water. For a range of liquid temperature experimental data are presented including the size and lifetime of the bubbles as well as the peak heat flux values.