THEORY AND EXPERIMENTS BY HOT BALL METHOD FOR MEASUREMENT OF THERMAL CONDUCTIVITY

The paper deals with theory and application of a hot ball sensor for measuring thermal conductivity. The sensor, in a form of a small ball, generates heat and simultaneously measures temperature response. A working relation of the sensor has been found on the base of an ideal model. The ideal model represents an empty sphere placed in specimen. Consequently there is a constant heat flow q for t > 0 streaming from the empty sphere into surrounding environment. A calibration procedure has been proposed to obtain reliable data. A working range of thermal conductivities of the tested materials has been estimated to be from 0.06 up to 1 W m K. Ideal model and a model considering heat capacity of the hot ball were tested.