Design and performance optimization of solar water heating system with perforated obstacle using hybrid multi-criteria decision-making approach

Solar water heating system (SWHS) is a cost-effective technology with high household adoption rates worldwide. The performance of SWHS significantly deteriorates due to several factors, including design parameters as well as radiative and convective heat losses from the system, which considerably impair the system's efficiency. Novel designs and unique heat transfer techniques are increasingly being explored to improve the efficiency of SWHS. In this framework, the following research focuses on designing and optimizing an SWHS integrated with perforated delta obstacles. The influence of Reynolds number (400, 800, 1200), angle of attack (15 degrees, 30 degrees, 45 degrees), and pitch ratio (0.5, 1, 1.5, 2.0) on the friction factor, Nusselt number, and thermo-hydraulic performance was investigated and optimized. The combination of Reynolds number = 1200, angle of attack = 45 degrees, and pitch ratio = 1 yielded the most significant Nusselt number (90.55). In contrast, the combination of Reynolds number = 1200, angle of attack = 15 degrees, and pitch ratio = 0.5 yielded the lowest friction factor (0.38). The largest thermo-hydraulic efficiency (2.75) was obtained using Reynolds number = 400, angle of attack = 45 degrees, and pitch ratio = 1. Since no single SWHS design alternative can meet all desired performance criteria, selecting the best among SWHS design alternatives is not easy. Therefore, a hybrid multi-criteria decision-making approach called AHP (analytic hierarchy process)-ARAS (additive ratio assessment) was implemented, suggesting the SWHS design alternative having the angle of attack = 45 degrees, Reynolds number = 1200, and pitch ratio = 1 satisfies the preset performance criteria. Finally, sensitivity analysis and validation with other decision-making approaches were performed to verify the proposed decision-making framework's effectiveness, proving the results' robustness.