Thermal Conductivity and Radiative Experiments Measurement *

Abstract

The thermal conductivities of polycarbonate, polystyrene and plywood were individually determined by sandwiching the test material between three 3.8 × 30.5 × 45.7 cm (1 1/2 × 12 × 18 in) aluminum plates. After the center plate was heated to 70°C–80°C, the sandwich was assembled and insulated on all sides. The temperatures of the center plate and one of the outer plates were measured with time and used to calculate the rate of heat transfer and then the thermal conductivity. The differences between experimental and literature values for thermal conductivity were 0% for plywood, 2.5% for polystyrene foam and 26% for Plexiglass®. Radiative absorptivities were obtained for five metallic surfaces with different surface finishes in comparison to a matte black paint surface finish as the control. Metallic rods were first cooled to <18°C prior to inserting a thermocouple into the center end of the rod and then insulating the ends. A 1000 W lamp was used to heat the rods while monitoring the temperature inside the rod as a function of time. Heat balances were then used to determine the surface absorptivity relative to the black matte finish. Finally, the experimental absorption coefficients were compared to values from the literature.