TRANSIENT ONE-DIMENSIONAL HEAT-FLOW TECHNIQUE APPLIED TO POROUS REACTIVE MEDIUM

A transient one-dimensional heat flow technique was presented to measu re the effective thermal conductivity of porous reactive media. The po rous reactive medium was in contact with a flat thermistor in a cell, and vacuum was applied to remove the air and the moisture. Afterwards, ammonia atmosphere was maintained in the cell under a fixed temperatu re and pressure. A varistor with max. 100 Ohm was used to equate with the resistance of the thermistor corresponding to the fixed temperatur e. The temperature increase of thermistor was 2-3 degrees C, which was sufficient to avoid the enthalpy effect due to chemical reaction. A g raphite-CaCl2 .NH3 complex was given as a test specimen for the porous reactive medium. Measurements showed that the thermal conductivity of graphite-CaCl(2 .)8NH(3) complex has distinctively higher values than the graphite-CaCl(2 .)4NH(3) and CaCl(2 .)2NH(3) complex. The accurac y of measured conductivity was estimated to be within 10%. (C) 1998 Am erican Institute of Physics.