ISSN Online: 2377-424X
International Heat Transfer Conference 12
Heat transfer in calcium chloride reactor bed for chemical heat pumps
Abstract
This paper deals with an investigation of the heat transfer in reactor beds for gas solid chemical heat pumps
driven by the reaction of calcium chloride with methylamine, methanol or ammonia. The experimental results
showed that the effective thermal conductivity of reactive pellet bed was reduced to less than one half of that of
the unreacted calcium chloride. Am odel for the effective thermal conductivity in a porous pellet bed has been
derived by dividing the overall void fraction of the bed into the void fractions inside and outside porous pellets,
which give different contributions to heat transfer. The thermal conductivity of reactive pellet estimated from
the measured effective thermal conductivity by the model was 0.15W/(mK), while the pellet thermal
conductivity of unreacted calcium chloride was 0.96W/(mK) under the condition of the same pellet void
fraction. Then a model for the heat flow through a porous pellet has been developed. The analysis using the
model suggests that the significant decrease in the pellet thermal conductivity is caused by the increase in the
contact resistance between grains in the pellet. This is in accord with the difference in grain structure observed in
SEM photographs. Estimations of the effective thermal conductivity based on the model equations represent well
the measured variations of the effective thermal conductivity under various conditions of reaction progress,
reactive gas substance and gas phase pressure.