Optimum Loading of Aluminum Additive Particles in Unconsolidated Beds of Finned Flat-Tube Heat Exchangers in an Adsorption Cooling System

In this study, the effects of employing aluminum additive particles in an unconsolidated adsorbent bed on the performance of an adsorption cooling system (ACS) are studied. A three-dimensional distributed-parameter model is developed to investigate whether there is an optimum additive volume fraction for different bed conditions of a finned flat-tube heat exchanger filled with silica gel SWS-1L. Moreover, a qualitative comparison between temporal water uptake patterns in the presence and absence of aluminum additive is made to study the adsorption dynamics. Considering identical diameters for adsorbent and additive particles, results show that 0.3 mm is the optimal particles diameter for the fixed fin depth of 20 mm, yet, different fin heights (3-20 mm) and additive volume fractions (0-25%). Furthermore, while increasing the additive volume fraction leads to a continuous increase and decrease in specific cooling power and coefficient of performance, respectively, it is revealed that the variations of average and volumetric cooling power (VCP) are non-monotonic depending on particle size and fin height. Consequently, for the beds with fin heights of 8 and 20 mm filled with optimal particle diameter, 15% and 20% are found as the optimum additive volume fractions in which the VCP based on a given adsorber heat exchanger total volume is maximized to 370.8 and 399.7 kW/m3, respectively.