Heat transfer characteristics in an adsorption heat pump (AHP) using a packed silica gel module (PS-module) were experimentally studied on the basis of results compared with those for the AHP with a direct heat exchange module (DS-module) type adsorber. Ultimate heat transfer enhancement for an adsorber of AHP is almost achieved by using the PS-module because of high packing density and thermal conductivity, and the possibility of its application to a refrigerator for producing low temperature cold heat energy is suggested.