Effect of Size on Cooling Kinetics of Spherical Samples from Different Grades of Aluminum

Abstract

The influence of the size of spherical specimens of different aluminum grades (A0, A5, A6, AB98, and A5N) on their characteristic cooling times and heat transfer coefficients in a wide temperature range has been investigated. It is shown that the cooling process of spherical samples in all cases is carried out by convective and radiative mechanisms of heat exchange with the environment, possessing characteristic times. The values of characteristic times of cooling due to convection and radiation are estimated. Using experimental data on the cooling rate of samples and theoretically calculated values of their heat capacity according to the Neumann-Kopp rule, the coefficients of radiant and convective heat transfer as a function of temperature are determined. It was compared with the regularities of the effect of sample size on the thermophysical properties of cylindrical samples. It is found that spherical specimens cool faster than cylindrical specimens of the same mass, and the heat transfer coefficients are larger. During the experiment, it turned out that the convective heat transfer coefficient lies in the range of 10-20 W/m²·K.