SPHERICAL FURNACE CALORIMETER FOR DIRECT MEASUREMENT OF SPECIFIC HEAT AND THERMAL CONDUCTIVITY*

Abstract

AbstractA spherical calorimeter was constructed for measuring true specific heat and thermal conductivity. It was formed of two concentric spherical platinum shells, and a spherical sample was fitted into the inner shell. Electric heat was supplied at the center of the sample, and the calorimeter was housed in a spherical electric furnace.Thermal conductivity was measured by determining the inner and outer sample temperatures at steady heat flow using the equation of heat conduction in a sphere; specific heat was measured by noting the temperature rise of the sample with a known heat input while maintaining the calorimeter shells near the adiabatic condition; and a correction for heat leakage was made by using the conductivity determination to calculate this factor.Specific heat and thermal conductivity measurements were made on quartz sand, chrome refractory cement, four types of insulating firebrick, and 85% magnesia insulation over a total temperature range of 100° to 2200°F. The estimated accuracy of specific heat measurement of 3 to 5% is consistent with engineering requirements. No estimate of accuracy can be given as yet for thermal conductivity results.