Heat Transfer between Liquid and a Sphere in Bubbling Flow

Abstract

The characteristics of bubbling flow of air and water approaching an ice sphere were made clear by means of the photographic recording method and the electroresistivity probe technique. The melting process of the ice sphere was recorded by a video camera and the local Nusselt number Nu_θ, was determined from a change in local radius with the aid of a digitizer supported by a large scale computer. Here, the initial radius of sphere was used as a representative length. The measured values of Nu_θ, increased appreciably all over the surface of the sphere compared to the values in single phase flow of water. As a result, the mean Nusselt number Nu averaged over the surface also increased. The increasing rate of Nu decreased gradually with the passing frequency of bubbles n_b and finally the effect of bubbles on Nu diminished. The effect of the Reynolds number based on the cross-sectional mean velocity of water and the initial diameter of sphere decreased with an increase in n_b.