Kinetics of water adsorption on loose grains of SWS-1L under isobaric stages of adsorption heat pumps: The effect of residual air

Abstract In this paper we studied the effect of a non-adsorbable gas (air) on kinetics of water adsorption on loose grains of the composite adsorbent SWS-1L (silica modified by calcium chloride) (grain size 0.8–0.9 and 1.4–1.6 mm). The adsorbent grains were placed on the surface of isothermal metal plate at T = 60 °C and equilibrated with the mixture of water vapor at PH2O = 10.3 mbar and air at a certain partial pressure PA. After that the metal plate was subjected to a temperature drop down to 35 °C at almost constant pressure over the grains. Reduction of the adsorption rate was revealed even at the partial pressure of residual air PA as low as 0.06 mbar. At PA > 0.4 mbar the kinetic curves were near-exponential and the characteristic adsorption time τ did not depend on the grain size and increased as τ = τ0 + APA, where A = 700 ± 50 s/mbar. Desorption stage was less affected by the residual air. The specific cooling power generated during the isobaric adsorption stage was estimated as a function of the residual air pressure.