Probes for contemporary measurement of thermal conductivity: thermal diffusivity and convection heat transfer

Four probes for measurement of thermal conductivity, thermal diffusivity and convection heat transfer coefficient have been designed, built, and tested. In two of these probes (SP-1 and SP-2) three thermocouples were located at 25%, 50%, and 75% of the total length of 150 mm, while the third one (SP-3) has the three thermocouples at 10%, 50% and 90%. The fourth probe (DP-1) is double, to measure thermal diffusivity with the pulse method. First results show good performances of the devices when used to measure a reference material (glycerol). In fact, an accuracy of about ±5% was achieved both in thermal conductivity and thermal diffusivity measurements. Due to their size (length 150 mm, diameter 2 mm) the probes are especially suited to measure the thermophysical properties of bulk materials, as soils, composites, walls of buildings, etc. Convection can be studied thanks to the presence of three thermocouples, so also the boundary layer can be evaluated.