Probes for Contemporary Measurement of Thermal Conductivity, Thermal Diffusivity, and Convection Heat Transfer

Abstract

Four probes for measuring thermal conductivity, thermal diffusivity, and convection heat transfer coefficient were designed, built, and tested. In two of these probes (SP-1 and SP-2), three thermocouples were placed at 25%, 50%, and 75% of the total length of 150 mm, while the third probe (SP-3) has the three thermocouples at 10%, 50%, and 90%. The fourth probe (DP-1) is a dual-probe, to measure thermal diffusivity using the pulse method. First results show good performance of the devices when measuring a reference material (glycerol). In fact, an accuracy of about ±5% was achieved in both thermal conductivity and thermal diffusivity measurements. The size of the probes (length 150 mm, diameter 2 mm) makes them particularly suitable for measuring the thermophysical properties of bulk materials, such as soils, composites, buildings walls, etc. Thanks to the presence of three thermocouples, convection can be studied so that also the boundary layer can also be evaluated.