Experimental measurements of the thermal conductivity of ash deposits: Part 1. Measurement technique

This paper describes a technique developed to make in situ, time-resolved m easurements of the effective thermal conductivity of ash deposits formed un der conditions that closely replicate those found in the convective pass of a commercial boiler. Since ash deposit thermal conductivity is thought to be strongly dependent on deposit microstructure, the technique is designed to minimize the disturbance of the natural deposit microstructure. Traditio nal techniques for measuring deposit thermal conductivity generally do not preserve the sample microstructure. Experiments are described that demonstr ate the technique, quantify the experimental uncertainty, and determine the thermal conductivity of highly porous, unsintered deposits. The average me asured thermal conductivity of loose, unsintered deposits is 0.14 +/- 0.03 W m(-1) K-1, approximately midway between rational theoretical limits for d eposit thermal conductivity.