Experiments on melting of slush ice in a horizontal cylindrical capsule

Melting phenomena are related to a wide variety of engineering fields: purification of metals, welding, electroslag melting, thawing of moist soil, and latent heat-of-fusion thermal-energy storage are a few of important applications which have motivated research in this area. Melting is a phase transformation process that is accompanied by absorption of thermal energy. The essential feature of the systems that exhibit melting phenomena is the existence of a liquid–solid interface that separates the two phases containing different thermophysical properties and the absorption of thermal energy at the interface. The major problem in melting is thus to determine transport phenomena of the latent and sensible heat of the system. There is quite a large body of literature concerning a variety of such problems in engineering as well as in the applied sciences. Recent reviews summarize prior work in this area [1–8]. In previous studies pertaining to melting of a solid contained in a confined vessel, consideration has been given to either to a melting solid which is constrained to prevent its possible movement owing to gravity or to a solid which is free to fall under gravity [8]. In the first case, the melting solid is maintained at a fixed position inside the vessel throughout the melting process, then is completely surrounded by the liquid melt, and the energy needed for the melting is transported from the heating wall to the solid–liquid interface by free convection within the liquid melt. In the second case, the solid is free to respond to the net force acting on it. If the solid phase has higher density than the liquid phase the solid sinks to the bottom of the vessel. On the contrary, if the solid phase is lighter than the liquid phase the unmelted solid is drawn by buoyancy to the top of the vessel. In either case, a region of close-contact melting arises between the solid and the heating wall. Utilization of thermal-energy storage system for air conditioning has recently evoked energy saving and normalizing the requirement level of the electric power supply [9, 10]. For conventional ice-storage systems using a pure ice system as a phase change material (PCM) it has been pointed out [11–14]that the melting heat transfer performance may be reduced with time because the melting ice surface is separated more far from the heat transfer wall. Marked attention has recently been given to a slush ice [15, 16], which is essentially a mixture of fine ice particles and