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

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. •Constructal law has been implanted to design treelike fins protruded into the PCM.•Higher construct fins decreases the melting time significantly.•3rd-construct fins on both the walls take 9 % of lesser time to than the fins only on inner surface.•Hybrid fins are better than any other considered designs.•Rigorous flow circulation is observed for the fins of higher constructs as well as hybrid fins.