EFFECT OF PRANDTL NUMBER ON THE HEAT TRANSFER FROM A ROTATING DISK: AN EXPERIMENTAL STUDY

摘要

Heat transfer coefficients were experimentally determined for a free rotating disk in still air and water. These were obtained with an electrically heated disk placed in a cylindrical pool. The accuracy of the employed experimental apparatus was assessed by heat transfer measurements in air. For this fluid, an excellent agreement with reliable literature data was found. Essentially new experimental data were obtained for water as fluid. Based upon the experimental data, the validity of theoretical correlations and the effect of the Prandtl number on the connective heat transfer from a rotating disk were discussed. It was found that in laminar water flow, the value of the correlation exponent for the Prandtl number is practically identical to 1/2 as theoretically predicted in 1948 by Dorfman. In turbulent flow, its value is better given by 1/3 as in case of the classical turbulent boundary layer theory.