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

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.

Automated summary

In order to maximize the efficiency of sorption bed heat exchangers in adsorption heat pumps, a balance between thermal conductance and coefficient of performance needs to be achieved. The effects of different geometries on conductance and COP were studied, and a dynamic heat pump model was developed to find the suitable balance point.