Activated carbon adsorption cycles for refrigeration and heat pumping

Abstract

Adsorption cycles were used for cooling before the advent of reliable mechanical compression refrigerators, and are now attracting renewed interest as the basis of solar powered refrigerators for vaccine storage etc. They also have potential for use in heat pump systems. The cycle thermodynamics are reviewed and the suitability of a range of refrigerants with active carbon adsorbents is assessed. Methanol, sulphur dioxide, ammonia, methyl amine, and formaldehyde are of particular interest. Experimental p-T-x data is presented for ammonia and methanol with a range of carbons, together with their calculated performance in refrigeration cycles. Currently available carbons can give good performance, but it is possible that specially developed carbons might show significant improvement. A major development area lies not in changing the porosity characteristics but in trying to improve heat and mass transfer to and from the adsorbent.