Faculty Publications
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Publications by NITK Faculty
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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 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 Investigating the effect of thermomechanical cycles on shape memory effect of four-dimensional printed glass fiber/polyether ketone ketone composite(John Wiley and Sons Inc, 2025) Ojha, N.; Kumar, S.; Ramesh, M.R.; Doddamani, M.Assessing the shape memory effect (SME) under repetitive thermomechanical cycles is crucial for designing structures undergoing subsequent fold and deployment during functioning, such as morphing structures and soft grippers. Four dimensional (4D) printing is a revolutionizing manufacturing technology, offering dynamic feature into three dimensional (3D) printed part. This work presents the first study on 4D printing and SME assessment of glass fiber (GF)/polyether ketone ketone (PEKK) composite for morphing structures and grippers in aerospace applications. GF/PEKK composite is developed using blending, and then filament is extruded for 3D printing. Annealing is performed on the 3D printed parts and evaluated using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and SME under subsequent cycles. The SEM analysis demonstrated the uniform distribution of GFs into PEKK with good interfacial bonds, indicating the appropriate selection of the process parameters. The composite depicted remarkable shape fixity (Rf) and shape recovery (Rr) of 91.07% and 96.08%, respectively, in first cycle. However, in tenth cycle, Rr is found to be decreased to 86.30%, a reduction of 9.78% is observed. Key findings of this research are the excellent storage modulus of 3150 MPa, which is 82.93% higher than PEKK. Thermal studies revealed very high glass transition temperature (Tg) of 175°C and thermal degradation temperature (Td) of 561.36°C, which is higher than PEKK (Tg = 161°C and Td = 548°C), demonstrating excellent thermal performance and showing potential for high-temperature shape memory applications. Highlights: Composite showed excellent shape fixity (91.07%) and shape recovery (96.08%). Quick shape recovery in 20 s showed potential for a swift actuator. Storage modulus of 3150 MPa is observed for the composite. Composite has a glass transition temperature of 175°C. Composite exhibited a high thermal degradation temperature of 561.36°C. © 2025 Society of Plastics Engineers.