This study investigates the thermo–exergy performance of a single-pass solar air heater (SAH) integrated with nine PCM-filled metallic cans beneath the absorber plate, designed for low-grade heating applications in North Indian winter conditions. The merit of this work lies in developing a transient three-dimensional Computational fluid dynamics (CFD) model (ANSYS Fluent 2024R1) that couples the enthalpy–porosity phase-change formulation, the discrete ordinate solar radiation model, and Delhi Typical Meteorological Year (TMY) data with a Taguchi L \(_9\) design-of-experiments framework. Three organic Phase Change Materials (PCMs) (RT60 paraffin, myristic acid, and stearic acid) and three encapsulation metals (copper, aluminium, stainless steel) were systematically assessed in terms of outlet air temperature rise, thermal and exergy efficiencies, melt fraction dynamics, and pressure drop. Results demonstrate that RT60 paraffin in aluminium cans achieves the best overall performance with a daily thermal efficiency of 72.1% and exergy efficiency of 12.9%, outperforming stainless steel–PCM combinations by over 15%. Copper also shows high effectiveness but with higher weight and cost. Exergy analysis revealed that high-conductivity cans significantly reduce entropy generation. The study provides a validated CFD–exergy pipeline for material and design screening, and future work will focus on experimental validation, nano-enhanced PCMs, and adaptive flow control to further enhance system reliability and efficiency.
