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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Heat transfer in calcium chloride reactor bed for chemical heat pumps

Get access (open in a dialog) DOI: 10.1615/IHTC12.2900
6 pages

要約

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.