A theoretical treatment of the design and optimization of adsorption heat pumps

Highlights: • Optimization of sorption bed with fin and tube geometry. • Silica gel-water and Activated carbon fiber-ethanol considered. • Sorption bed designed to achieve a balance between component UA and COP. • Dynamic system model developed using lumped and distributed parameter methods. • Lumped parameter model deemed acceptable for system simulation. The thermal conductance of sorption bed heat exchangers in adsorption heat pumps should be large to maximize the change in equilibrium uptake and refrigerant throughput. However, the use of extended surfaces to increase the heat transfer area affect the coefficient of performance detrimentally as energy stored in the inert heat exchanger during desorption is discarded during the subsequent pre-cooling and adsorption stages. The effects of fin and tube geometry on conductance and coefficient of performance are investigated for the silica gel-water and activated carbon fiber (ACF)-ethanol working pairs. A systematic procedure to achieve a balance between thermal conductance and COP is presented. A dynamic heat pump model is developed using two methods – lumped parameter and distributed parameter approach. For the specified operating conditions and geometry, the two models agree within 1.5%, which suggests the suitability of the lumped-parameter approach for system modeling.