To improve the heat transfer characteristics of a gas-solid packed-bed reactor, an inert solvent was added to the reactor. For sodium carbonate decahydrate dehydration, used in a chemical heat pump, n-pentanol was chosen as a solvent, and the dehydration rate in the solvent was measured. The dehydration rate was found to be proportional to the total surface area of the decahydrate particles, and the rate equation was determined. Particle size distribution (less than 400 mu m) remained unchanged for a three-time cyclic operation. The packed-bed of decahydrate with n-pentanol solvent showed considerable improvement in heat transfer characteristics compared with the case having no solvent, and cold heat generation was more than doubled. A simulation study showed that the addition of n-pentanol may make it possible to construct a high-performance heat pump with cold storage capability, attaining 280 K in less than 5 s and total heat release within 1600 s.