DEVELOPMENT OF LOCALLY PRODUCED DEVICE FOR MEASUREMENT OF THERMAL PROPERTIES OF CONDUCTING SOLID MATERIALS

Abstract

The need to provide a useful device that can be deployed in industries and research centres for measurement of thermophysical properties of conducting solid composite materials forms the basis of this research work. The American Society for Testing and Materials (ASTM) E1225 comparative cut bar test method was adopted. Two Heater and Cooler blocks was fabricated using aluminium waste materials and their thermal conductivity determined using the HT11C linear heat conduction apparatus. Ten thermocouple sensors positioned at a distance of 60 mm each was used to monitor the temperature profile along different positions in the system. The developed device also incorporates current and voltage sensing units, ten thermocouple amplifiers, Arduino mega microcontroller, microSD card shield and two liquid crystal displays. The heater block, cold water tank, and the instrumentation unit were powered by a 12 V DC wet battery source. When electrical energy is applied, heat flux from the heater passes through the test column with the respective thermal gradients measured by the temperature sensors. The unknown sample whose thermophysical property is being measured is sandwiched between two reference samples and simultaneously heated at one end and cooled at the other end. Measured values are stored in a microSD card. This process continues until a steady state temperature is attained. The steady state values were then used in determining the thermal conductivity, specific heat and thermal diffusivity properties of the solid composite sample using well established solutions of the Fourier heat equations. The device was calibrated using two standard samples of known thermophysical properties namely Aluminium 6061-T6 and Stainless Steel 304. The HT11C linear heat thermal conductivity device was equally used as standard equipment to calibrate the developed device. Thermal conductivity values of 166.67, and 13.78 𝑊/𝑚𝑜𝐶, specific heat capacity values of 897.08, and 501.69 𝐽/𝑘𝑔𝑜𝐶, and thermal diffusivity values of 6.8 × 10−5, and 0.39 × 10−5 𝑚/𝑠2 were obtained for Aluminium 6061-T6 and Stainless Steel 304 samples respectively. The developed device performed very well as it measured the thermal conductivity of the Aluminium 6061-T6 sample at a percentage deviation of 0.73% from the HT11C standard device, the literature standard. For the 304 Stainless Steel sample, the percentage deviation of the developed device is 2.13% from the HT11C . The specific heat capacity measured by the developed device was at a percentage deviation of 0.12%, and 0.06% while the thermal diffusivity was at a percentage deviation of 6.25%, and 7.14% for Aluminium 6061-T6 and 304 Stainless Steel samples respectively when compared with available literature standards. The developed device is thus useful for measurement of conducting composite materials