On measuring the contributions of various components to heat transfer in air

In the horizontal non-convective configuration, the thermal conductivity of an air volume bounded by polystyrene sidewalls and isothermal parallel surfaces of the heater and cooler was measured at thermal energy emissivities close to 0 or 1. In the vertical configuration, the maximum natural convection-induced increase in thermal conductivity of the same volume was measured, depending on the gap thickness between the heater and cooler. The relationships between radiative, conductive, and convective contributions to heat transfer were determined. The conditions for the onset of natural convection were investigated.