On the Melting of an Ice Sphere in Forced Convection

Abstract

The purpose of this paper is to obtain basic data to calculate the amount of ice required for an ice bunker in forced convection type precooling and cold storage facilities. The melting phenomena of an ice sphere placed in forced air convection was investigated experimentally. The results are as follows: 1) The total heat transfer rate to an ice sphere can be obtained as the algebraic sum of free convection, radiation and condensation heat transfer rates. 2) An ice sphere melted in an almost spherical shape on the front hemisphere, while it changed to an anomalous shape on the rear hemisphere. There was a stagnant point on each hemisphere. 3) Separation point moved backward with melting. 4) Local Nusselt and Sherwood numbers were larger near the both stagnant points and smaller at the separation point than any other points. The dependence of these values on Reynolds number was minimum near the front stagnant point and maximum near the rear stagnant point. 5) When Reynolds number was constant, there was a tendency that local Nusselt and local Sherwood numbers increased with turbulent intensity. 6) Average Nusselt and Sherwood numbers were given by the following equations: Nu_Q=2+0.46 Re^0.51 Pr^1/3, Sh_Q=2+0.46 Re^0.51 Sc^1/3. Average Nusselt and Sherwood numbers were smaller than those in the heat transfer without fusion, presumably due to the resistance of melted water film to heat transfer.