Nucleate pool boiling : the influence of heated surface inclination on heat transfer and vapour bubble dynamics

The present work comprises a theoretical and experimental study of nucleate pool boiling with particular reference to the effects of varying the inclination of heated surface. Distilled water is used as the boiling liquid and is maintained at atmospheric pressure throughout. An electrically heated metallic ribbon forms the boiling surface. Typical boiling curves are constructed for each inclination of the heated surface to provide a comparison of rates of energy exchange. Pool boiling heat transfer mechanisms are examined by considering convection cooling, latent heat transport, liquid temperature gradients, nucleation site density, and the incipient temperature requirements for boiling. The Rohsenow heat transfer correlation is extended to enable boiling heat transfer data to be correlated for all inclinations of the heated surface. An investigation of vapour bubble dynamics is made using high speed cinematography. Waiting period, initial bubble radius, growth and departure of vapour bubbles on the heated surface are examined for a range of heated surface inclinations. Theoretical models are developed to predict the above phenomena, and the results are found comparable with those obtained experimentally.