Numerical investigation and response surface optimization of a sorption heat storage systems performance using Y-shaped fins

Abstract

Several previously developed prototypes have proven the high energy density of sorption heat storage systems. However, the very poor thermal conductivity of the material bed, especially in closed sorption storage systems, has remained one of the main challenges for introducing this technology to the market. In this paper, the use of straight and Y-shaped fins is investigated to break through the limitation of heat transfer. An axisymmetric transient analysis is established for the adsorption and desorption processes of zeolite/water pair in an adsorption bed containing Y-shaped fins. The results of numerical simulations reveal higher adsorption rates, and improved heat transfer throughout the bed and also between zeolite and heat transfer fluid using Y-shaped fins during the adsorption process, leading to increasing outlet temperature of the heat transfer fluid. The effect of Yshaped fin length and the angle between the branches has been investigated through a parametric study, aiming to find the optimized fin geometry. The response surface method (RSM) has been applied to relate the achieved outlet temperature to the fin geometry. The investigations were carried out independent of the amount of metal used, to study the improvement only as a result of changing the geometry and arrangement of fins. Based on the investigations, the optimized geometry of the Y-shaped fins has been defined. The average temperature lift for a time period of 800 min has increased by 4.6 K compared to the case with straight fins and 8.7 K compared to the case without fins, and for the average output power, 103 % and 238.8 % improvement is observed compared with the case with straight fins and without fins, respectively. The result of the study for the desorption process shows an increase of 42 K in the temperature of the adsorbent bed for the optimum case compared with the case without fins.