Dynamics of water sorption on a single adsorbent grain caused by a large pressure jump: Modeling of coupled heat and mass transfer

Here we present a mathematical model of coupled heat and mass transfer in the course of water adsorption on a single adsorbent grain, which is in thermal contact with an isothermal metal plate. Adsorption is caused by a large jump of vapour pressure over the grain. The radial profiles of the grain temperature and the water concentrations in the adsorbed and gas phases were calculated as a function of time. Strong interrelationship between the shapes of the water sorption isotherm and the radial uptake profile was revealed. The best fit to the experimental data of [B. Dawoud, Yu. I. Aristov, Experimental study on the kinetics of water vapour sorption on selective water sorbents, silica–gels and alumina under typical operating conditions of sorption heat pumps, Int. J. Heat Mass Transfer 46 (2) (2003) 273–281] corresponds to the water diffusivity De = 6.0 × 10−6 m2/s and the coefficient of the heat transfer αp = 70 W/(m2 K) which are larger than those measured in quasi-equilibrium experiments.