EXPERIMENTAL-STUDY OF THE CONVECTIVE COOLING OF A HEATED CONTINUOUSLYMOVING MATERIAL

An experimental investigation of the heat transfer associated with a c ontinuously moving material has been carried out. This thermal transpo rt circumstance is encountered in many manufacturing processes, such a s 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 veloci ty in a stationary extensive fluid is considered. Very little experime ntal 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 movin g vertically downward in water and moving vertically upward or downwar d in air. The effects of thermal buoyancy, material speed, and propert ies of the material and the fluid on the thermal field are studied. Th e 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 substantia l. This effect decreased with an increase in the material speed. The t hermal boundary layer is found to be thicker in air than in water, as expected. The effect of thermal buoyancy on the temperature distributi ons in air was found to be very significant. High-thermal-conductivity materials, such as aluminum, are cooled down more rapidly than low-co nductivity materials, such as teflon. The experimental results obtaine d lead to a better understanding of the underlying transport mechanism s and add to the data base needed for the design and optimization of t he relevant systems.