Effects of thermocouple electrical insulation on the measurement ofᅡᅠsurface temperature

Analytical, numerical and experimental analyses have been performed to investigate the effects of thermocouple wire electrical insulation on the temperature measurement of a reference surface. Two diameters of type K thermocouple, 80 mm and 200 mm, with different exposed wire lengths (0 mm, 5 mm, 10 mm, 15 mm and 20 mm) were used to measure various surface temperatures (4 C, 8 C, 15 C, 25 C and 35 C). Measurements were made with the thermocouple in direct contact with the surface, with wires extending vertically and exposed to natural convection. Analytical results of the thermocouple wire with insulation confirm that there is no specific value for the critical radius and the rate of heat flux around the thermocouple wire continuously increases with the wire diameter evenwhen this is larger than the critical radius. Numerical simulation using COMSOL Multiphysics software also confirms that there is negligible thermal effect from the electrical insulation. Moreover, the experimental results agree well with those obtained by both the analytical and numerical methods and further confirm that the diameter of the thermocouple has an impact on the temperature measurement. © 2015 Elsevier Ltd. All rights reserved.