Constructal invasion of fins for melting time prediction of a phase change material in a triplex-tube heat exchanger

Abstract

In this work, the melting time of a phase-change material (PCM) has been estimated by invading different constructs of fins (i.e., 2nd, 3rd and 4th) in a triplex-tube heat exchanger using the constructal law. The continuity, momentum, and energy equations based on the enthalpy-porosity formulation have been solved in a finite volume platform of Ansys Fluent R16. The constructal fins are made up of copper, and installed on the both walls protruding into the PCM (i.e., RT-82). We estimate and compare the melting times of seven different configurations of constructal fin arrangements so as to obtain the best configuration with a low melting time, which is main object of this work. We observe that melting time decreases significantly with the higher construct of fins. For the fourth-construct fins (i.e., 4C-in), the melting time decreases by 42.5 % compared to the 2nd-construct fins (i.e., 2C-in). Fins on the both surfaces (i.e., inner and outer) performs better than the fins only on the inside or outside surfaces. The 3rd-construct with fins both on the inner and outer surfaces (i.e., 3C-in-out) reduces melting time by 50.3 % as compared to the 2nd construct fins (i.e., 2C-in-out). At a particular time (i.e., t = 2600 s), the 4th construct fins melts 96 %; whereas, the 3rd-construct fins melts only 91.9 % of PCM. The hybrid fins are better than the simple Y-shaped fins. The heat transfer and fluid flow dynamics are presented thorough the temperature, melt fraction as well as the velocity contours. Hybrid fins produce rigorous local flow circulations.