Evaluation of thermal conductivity for compacted kaolin Clay-Shredded tire mixtures as thermal insulation material

Abstract

Thermo-active engineering projects have been extensively constructed with the rapid increase in energy consumption, which poses high requirements on the design of thermal insulation materials. The present study investigated the thermal conduction behaviors of kaolin clay mixed with shredded tires with different particle gradations. The thermal conductivity of compacted kaolin-shredded tire mixtures was measured using a thermal needle probe to evaluate the combined effects of shredded tire mixing ratio and mean particle size. Based on the experimental data, an empirical model was developed to describe thermal conductivity behavior of the mixtures. The results showed that thermal conductivity of kaolin-shredded tire mixtures decreased with increasing shredded tire mixing ratio, and a maximum reduction in thermal conductivity (Δk = 66.14%) was detected in the sample with 50% volumetric ratio of shredded tire with mean particle size D50 of 0.20. The heat conduction mode of the mixtures changed from ‘shredded tire-matrix’ to ‘kaolin-matrix’ with an increase in particle size of shredded tires, corresponding to the lower thermal conductivity measured in the sample with a relatively smaller size of shredded tire. Linear increasing trends were found in the plot of percentage difference in thermal conductivity Δk versus shredded tire mixing ratio Rs, and the slope values exhibited a power function relation with the mean particle size of shredded tires. The developed thermal conductivity model of kaolin-shredded tire mixtures perfectly captured the trends in the testing data, with an absolute percentage error δ of less than 3% and root mean square error RMSE value of 0.0087 W/m·K. This empirical model may be extended to other compacted clay-shredded tire mixtures by adjusting/introducing calculation parameters.