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Apparent diffusivity of water in silica gel and NaX zeolite pellets
José M Gurgel, Luiz S Andrade Filho, Pedro P Souza Couto

The apparent mass diffusivity of water vapour (moist air) in silica gel and zeolite particles was measured at 2 kPa with a simple constant volume/pressure apparatus. A theoretical simple model is presented, with the overall kinetics controlled by an apparent diffusivity identified by a curve-fitting method which consists of a comparison of experimental and theoretical results. The model presents good agreement with experimental results and is in good agreement with earlier publications. The results are useful for the optimisation of the heat and mass transfer in adsorbent beds of thermal adsorption devices and deisiccant systems of cooling by low temperature from solar heating or industrial waste heat. There is a different rate of sorption between silica gel and zeolite at the working pressures of the desiccant device.

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