A novel optimal constructal fork-shaped fin array design to ascertain thermo-heightened performance under dehumidifying conditions

Abstract

The current work deals with the design and analysis of an array of constructal fork-shaped fins attached to a circular tube and operating under fully wet condition. For the mass transport process, a linear relation is adopted between the humidity ratio of saturated air and the corresponding fin surface temperature. After obtaining temperature distribution analytically, a metaheuristic optimization technique is adopted to maximize the net heat transfer rate of the fin array and un-finned surface imposing certain constraints. The constraints are taken such that the radial space limitations, fin material limitations as well minimum fin gap considerations are taken into account. As the present problem involves a large number of design parameters as well as the interrelated constraints, Particle Swarm Optimization technique has been employed for determining the optimum condition. The proposed theoretical analysis has been performed for different operating conditions and the results have been compared with the corresponding rectangular fin array. From the analysis, it has been found that optimum fork–shaped fin array with two branches gives higher heat transfer rate than the corresponding optimum rectangular fin array. For a typical situation (fin volume 0.0005 m3, air relative humidity 70%, ambient temperature 30 °C, base temperature 5 °C, convective heat transfer coefficient 20Wm-2 K−1, fin material thermal conductivity 236 Wm-1 K−1 and minimum gap between fins 0.002 m), optimum fork-shaped array with two branches gives 59.58% higher heat transfer rate than that of the optimum rectangular fin array. In certain cases, though the difference in heat transfer rate between optimum fork–shaped fin array with two branches and the corresponding optimum rectangular fin array is small, but the total fin length for the former case is found to be lower and thus fork shaped fin array with two branches is a better option than the rectangular fin array. However, no benefit in terms of either higher optimum heat transfer rate or lower total fin length is obtained by increasing the number of branches of the fork shaped fins beyond two.