Development and performance evaluation of locally fabricated thermal conductivity apparatus

Abstract

This paper presents the design and construction of a Guarded Hot Plate (GHP) apparatus for the accurate assessment of thermal conductivities of some Nigerian local building materials. The GHP apparatus is a steady-state measurement device. This apparatus is designed to measure the thermal conductivities of masonry building materials of different compositions. The design features included hot and cold plates fabricated with aluminum plates of 6 mm thickness and varying dimensions; the guard plates also made of aluminum, but of 6.35 mm thickness, forms a rigid enclosure for the specimen all encased in a mild steel housing. The operating measuring temperature range is from -20 for varying specimen thickness up to 60mm. Results are presented for concrete, laterite, and a mixture of cement with laterite, clay, and sand respectively, and it covers a range of thermal conductivities of 0.77W/mK to 1.80 W/mK. Moisture effect on concrete was recorded for the lightweight concrete as the thermal conductivity value reduced from 1.80W/m.K to 1.32W/m.K for the oven-dried concrete sample over a 1.5% (by weight) reduction in water content. The performance evaluation of the locally fabricated GHP apparatus showed a 3.03% percentage difference over ASHRAE’s published data on oven-baked concrete thermal conductivities