Faculty Publications
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Item Exergy Analysis of a Triangular Duct Solar Air Heater with Square Ribs(Springer Science and Business Media Deutschland GmbH, 2022) Nidhul, K.; Kumar, S.; Yadav, A.K.; Anish, S.The awareness about limited energy resources has urged the scientific community to scrutinize the energy conversion devices and optimize existing limited resources. In this analytical study, the exergetic performance analysis of a triangular cross-section square ribbed solar air heater (SAH) is compared with a conventional SAH. Reynolds number (Re) and temperature rise parameter (∆T/G) are varied, and their effect on exergetic efficiency is quantified. For the present study, maximum exergetic efficiency for the present study is obtained for non-dimensionalized rib height (e/D) of 0.05 and non-dimensionalized rib pitch (P/e) of 10. The optimum combinations of roughness parameters are interpreted through plots to design turbulators for triangular cross-section solar air heaters. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Enhanced thermo-hydraulic performance in a V-ribbed triangular duct solar air heater: CFD and exergy analysis(Elsevier Ltd, 2020) Nidhul, K.; Kumar, S.; Yadav, A.; Anish, S.Computational fluid dynamics (CFD) and exergy analysis are conducted to investigate the impact of secondary flow produced by V-ribs on the overall performance of a triangular solar air heater (SAH) duct. For a fixed relative rib pitch (Rp = 10) and relative rib height (Rh = 0.05), the effect of rib inclination (?) is studied using CFD technique for varying Reynolds number (5000 ? Re ? 20000). Based on the CFD simulation results, empirical correlations capable of predicting Nu and f with an absolute variance of 8.7%, and 4.7%, respectively, are developed. Employing these correlations, exergetic performance analysis is carried out. Maximum effectiveness parameter (?) of 2.01 is obtained for ? = 45° at Re = 7500. The exergy analysis reveals that the entropy generated is lower for the ribbed triangular duct compared to the smooth duct with maximum enhancement in exergetic efficiency (?ex) as 23% for ? = 45°. The study is extended for the rectangular duct to compare the performance with the ribbed triangular duct SAH (? = 45°). Results show that ribbed triangular duct SAH (? = 45°) is superior over various configurations of the ribbed rectangular duct SAH at higher mass flow rates. © 2020 Elsevier LtdItem Efficient design of an artificially roughened solar air heater with semi-cylindrical side walls: CFD and exergy analysis(Elsevier Ltd, 2020) Nidhul, K.; Yadav, A.; Anish, S.; Arunachala, U.C.Solar air heater (SAH) with semi-cylindrical sidewalls and W-baffles is analyzed for energy and exergy efficiency in the turbulent flow regime. Computational fluid dynamics (CFD) analysis is carried out for a fixed baffle inclination (?) and varying the relative baffle height (Rh = e/D) and relative baffle pitch (Rp = P/D) in the range 0.046–0.115 and 0.46–1.15, respectively. For Reynolds number (5000 < Re < 17,500), the numerical methodology is substantiated using experimental and theoretical correlations obtained from the literature. Smaller vortices near the sharp corners are removed by rounding the sharp edges, allowing the flow of fluid from inside and horizontal walls of the duct towards the semi-cylindrical sidewalls. This increases the overall turbulent kinetic energy. A peak augmentation of 3.24 and 4.03 times is obtained for Nusselt number (Nu) and friction factor (f), respectively, in contrast to conventional SAH. With a maximum enhancement of 127% in the effectiveness parameter relative to smooth SAH, this novel SAH design is evidently energy efficient. Based on CFD results, new correlations are developed in terms of Rh and Rp, which predicts the values with an absolute deviation of 4% and 7.4%, respectively. With lower exergy destruction, maximum enhancement in thermal and exergetic efficiency is obtained as 40.7% and 95.4%, respectively, for the proposed SAH relative to conventional SAH. Upon comparison with ribbed rectangular duct SAH configurations, the present design with semi-cylindrical side walls outperforms at all flow Re. © 2020 International Solar Energy SocietyItem Influence of Rectangular Ribs on Exergetic Performance in a Triangular Duct Solar Air Heater(American Society of Mechanical Engineers (ASME), 2020) Nidhul, K.; Kumar, S.; Yadav, A.; Anish, S.Several artificial roughness (ribs) configurations have been used in flat plate solar air heaters (SAH) in recent years to improve their overall performance. In the present work, energy and exergy analyses of rectangular ribs in a triangular duct SAH for varying relative rib heights (e/D = 0.02-0.04), relative rib pitches (P/e = 5-15), and rib aspect ratios (e/w = 0.5-4) are evaluated and compared with smooth SAH. The analysis reveals that the entropy generated due to heat transfer is lower for the ribbed triangular duct compared to the smooth duct. It is also observed that the width of the rib plays a crucial role in minimizing heat losses to the environment. A maximum reduction of 43% and 62% in exergy losses to the environment and exergy losses due to heat transfer to the fluid is achieved, respectively, with a rib aspect ratio (e/w) of 4 compared to the smooth plate. It is found that in contrast to the smooth plate, ribs beneath the absorber plate effectively improves thermal and exergetic efficiency. Maximum enhancement of 36% and 17% is obtained in exergetic efficiency (?ex) and thermal efficiency (th), respectively, for e/w = 4, P/e = 10 and e/D = 0.04. Results also show the superiority of the ribbed triangular duct over the ribbed rectangular duct for an application requiring compact SAH with a higher flowrate. © 2020 by ASME.Item Energy and exergy analysis of solar air heater with non-uniform porous medium under varying solar intensity and radiation effects: a 3-D CFD study(Taylor and Francis Ltd., 2025) Nidhul, K.; Joshi, A.; Yadav, A.K.; Anish, S.The effect of a thin porous layer on the performance of a solar air heater (SAH) is investigated for both uniform and non-uniform configurations. 3-D computational fluid dynamic (CFD) simulations of SAH are performed for turbulent flow, and the transient performance with porous medium configurations is studied. A discrete-ordinate (D-O) model is employed, and diurnal variations of solar heat flux and inlet air temperature variations are considered in this study. The porous medium above the absorber plate significantly enhances the SAH's thermo-hydraulic performance parameter (THPP). The proposed configuration reduces the irreversibility in heat transfer and the possible hot spots that could occur when ribs are employed as artificial roughness, thereby enhancing the Nusselt number (Nu). The highest increment in Nu is obtained as 7.5 times, leading to maximum enhancement in THPP by 60% for descending porous medium compared to uniform porous medium configuration. Further, from the exergy analysis, the descending porous medium reported higher collector efficiency (66-70%). Owing to higher exergy gain and lower exergy losses, the energetic efficiency of the descending porous configuration is higher than the uniform porous configuration. Both thermo-hydraulic and exergy performance increases due to conduction and radiation within the porous medium apart from convection. © 2025 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.