Degradation of Desiccants Upon Contamination: An Experimental Study

Experiments were conducted to quantify the effects of thermal cycling and exposure to contamination on solid desiccant materials that may be used in desiccant cooling systems. A test apparatus was used to thermally cycle several desiccant samples and expose them to 'ambient' or 'contaminated' humid air. The source of contamination was cigarette smoke. Six different solid desiccants were tested:two types of silica gel, activated alumina, activated carbon, molecular sieves, and lithium chloride. The exposed; desiccant samples were removed after 0.5, 1, 2, 4, or 11 months of exposure and their moisture capacities were measured. Other tests were conducted to characterize pollutants deposited on the exposed samples or to evaluate impact of exposure on internal structure of the samples.Compared to fresh samples, the capacity loss due to thermal cycling with ambient air was generally 10% to 30%. The capacity loss due to only cigarette smoke was generally between 20% to 50%.