Experimental investigation of contact resistance in adsorber of solar adsorption refrigeration

The key component of a solar adsorption refrigeration unit is the adsorber packed with an adsorbent such as zeolite, active carbon and CaCl2. One essential problem faced is the poor heat transfer in adsorbers, which strongly influences the performance of the system. Poly-aniline, with the advantage of superior thermal conduction, was introduced into an adsorber to increase the thermal conductivity of the adsorbents. As the thermal conductivity coefficient of adsorbent in the adsorber is enhanced, the thermal contact resistance of the interface becomes a significant proportion and needs to be improved. The heat transfer of solid interfaces, particularly the effects of the adsorbent granule or block with rough surfaces, is studied in this paper. Methods for decreasing the contact resistance using spreading adhesive or exerting pressure on the interface are presented and analysed. A test facility and relevant procedure are developed to measure the effects of different interfaces on the contact resistance. The heat transfer at the interface between the copper surface and the adsorbent granule or block is investigated, and its effect in improving the thermal performance of the adsorber in solar adsorption refrigeration is compared. The experimental results show that exerting pressure or spreading adhesive on the interface can reduce the contact resistance significantly without affecting the mass transfer of the adsorbent in an adsorber. (C) 2002 Elsevier Science Ltd. All rights reserved.