Effective thermal conductivity of graphite-metallic salt complex for chemical heat pumps

Abstract

An experimental procedure was developed for measuring the effective thermal conductivities of graphite-CaCl2. nNH(3) (n = 8, 4, 2), MnCl2. nNH(3) (n = 6, 2), and BaCl2. 8NH(3) complex for chemical heat pumps. Graphite-metallic salt complex was manufactured through the impregnation of metallic salt into a porous graphite matrix. Experimental conditions of pressure and temperature were directly established by the thermodynamic equilibrium lines of salt-ammonia systems obtained by the calorimetric method. Afterward, effective thermal conductivities were measured using a transient one-dimensional heat flow technique at a fixed pressure and temperature under an ammonia atmosphere. Effective thermal conductivities of the graphite-metallic salt complex were in the range of 10-49 W/mK, which are significant higher values than powder beds of 0.1-0.5 W/mK. Results showed that the effective thermal conductivity of a graphite-metallic salt complex has a strong dependency on the bulk density, the weight fraction of graphite, and the ammoniated state of salt.