EXPERIMENTAL-STUDY OF THE CONVECTIVE COOLING OF A HEATED CONTINUOUSLY MOVING MATERIAL

Abstract

An experimental investigation of the heat transfer associated with a continuously moving material has been carried out. This thermal transport circumstance is encountered in many manufacturing processes, such as hot rolling, fiber drawing, plastic extrusion, crystal growing, and continuous casting. The transport associated with a heated plate or a cylindrical rod being cooled due to its own movement at uniform velocity in a stationary extensive fluid is considered. Very little experimental work has been done on this problem and this study focuses on the resulting thermal fields. Time-dependent temperature distributions in the solid, as well as in the flow, are measured for the material moving vertically downward in water and moving vertically upward or downward in air. The effects of thermal buoyancy, material speed, and properties of the material and the fluid on the thermal field are studied. The results indicate that the temperature profiles obtained are similar to those obtained in earlier numerical and analytical studies. At low material speeds, the upstream penetration of the conductive transport due to temperature variation in the material was seen to be substantial. This effect decreased with an increase in the material speed. The thermal boundary layer is found to be thicker in air than in water, as expected. The effect of thermal buoyancy on the temperature distributions in air was found to be very significant. High-thermal-conductivity materials, such as aluminum, are cooled down more rapidly than low-conductivity materials, such as teflon. The experimental results obtained lead to a better understanding of the underlying transport mechanisms and add to the data base needed for the design and optimization of the relevant systems.