Journal Articles
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Item Critical review of ribbed solar air heater and performance evaluation of various V-rib configuration(Elsevier Ltd, 2021) Nidhul, K.; Yadav, A.K.; Anish, S.; Kumar, S.The low heat transfer rate in a flat plate solar air heater (SAH) is due to the development of a laminar sub-layer near the heated absorber plate. Owing to this, the plate temperature rises substantially, instigating losses and thus reducing the efficiency. Extensive research has been carried out to mitigate this problem, of which passive technique emerged to be a promising solution. The passive method involves the application of fins/turbulators/ribs on the surface where the boundary layer develops so that it breaks the same. Various profiles and configurations of the ribs ranging from transverse to inclined and continuous to discrete have been presented concisely. Correlations on Nusselt number (Nu) and friction factor (f) for different rib configurations have been summarized in order so that it can be accessed for future research. 3-D CFD analysis is carried out to gain insight into the flow pattern of various V-ribbed SAH, and with the help of streamlines and contours, the findings are established. Furthermore, various exergy destruction has been studied in detail for different V-rib configurations, namely– V-rib, multiple V-rib, and multiple V-rib with the gap, and analyzed in detail for prospective studies. Exergetic performance study of these rib configurations indicates that the multiple ribs and the multiple rib-gap combinations enhance exergetic efficiency (ηex) by 12% and 31.6%, respectively, in comparison to V-rib SAH. © 2021 Elsevier LtdItem 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 Computational and experimental studies on the development of an energy-efficient drier using ribbed triangular duct solar air heater(Elsevier Ltd, 2020) Nidhul, K.; Kumar, S.; Yadav, A.; Anish, S.Triangular duct cross-section is introduced for solar air heater (SAH) of an indirect type of solar dryer (ITSD). Using computational study, the thermo-hydraulic performance of triangular duct SAH with inclined ribs for varying rib inclination (30° < ? < 75°) in the turbulent flow regime (5000 < Re < 17500) is studied. With the rib configuration providing maximum thermos-hydraulic performance, a ribbed rectangular duct SAH is designed, and the performance of the same is compared to the former for similar heat input. Results show that the ribbed (? = 45°) triangular duct has 17% higher effectiveness compared to the latter and 79% when compared to smooth SAH. Ribs in triangular duct solar air heater facilitate the increase in temperature even in the core of the duct, delivering the air at 6 K additional temperature relative to a rectangular ribbed duct for same heat input and flow Re. The superiority of the ribbed triangular SAH is further confirmed by studying the drying characteristics of Okra and two variants of banana, namely Nendran and Robusta for the maximum temperature obtained at the outlet of the respective SAH. Various thin layer drying models available in the literature were analyzed, and Modified page model represented the drying behaviour with R2 = 0.99. For ITSD, ribbed triangular duct SAH exhibits a maximum of 60.3% reduction in moisture ratio with a maximum increase of 97.9% increase in average values of diffusivity coefficient confirming that it is an energy-efficient design for an ITSD. © 2020 International Solar Energy SocietyItem Thermo-hydraulic and exergetic performance of a cost-effective solar air heater: CFD and experimental study(Elsevier Ltd, 2022) Nidhul, K.; Yadav, A.K.; Anish, S.; Arunachala, U.C.An experimental and computational fluid dynamics (CFD) study is carried out to investigate the impact of secondary flow strengthening the thermo-hydraulic performance of discrete multiple inclined baffles in a flat plate solar air heater (SAH) with semi-cylindrical sidewalls. Initially, for a fixed relative baffle height (Rh = 0.1), the relative baffle pitch (Rp) for continuous baffles is varied in the range of 0.6–1 to obtain the optimum baffle pitch for 6000 p. A maximum thermo-hydraulic performance of 2.69 is obtained for the gap at the trailing apex. The proposed design has a higher collector efficiency, 55–70%, compared to the ribbed rectangular SAH design exhibiting 30–55%. With lower exergy losses, the present SAH design has higher exergetic efficiency (1.5%–2.2%)than ribbed rectangular SAH (0.9%–1.7%) for the range of Re studied. Further, at low Re, the present SAH design has a higher coefficient of performance, indicating that it is cost-effective than ribbed rectangular SAH designs. © 2021 Elsevier LtdItem Analytical investigation on thermo hydraulic performance augmentation of triangular duct solar air heater integrated with wavy fins(Taylor and Francis Ltd., 2023) Renald, T.R.; P, S.; Matheswaran, M.; Gnanasekaran, G.Present work deals with performance improvement of triangular duct solar air heater by integration of wavy fin on absorber plate. An analytical model has been developed for the investigation of design parameters such as fin pitch ratio with ranges 0.05–0.2 and fin amplitude ratio with ranges 0.025–0.125. MATLAB code is generated to solve the energy balance equations by iterative procedure. The influence of design parameters on effective thermal and thermal efficiency is presented and its influences are discussed. Increasing the fin pitch ratio decreases the thermal and thermo hydraulic efficiency drastically. The positive effect of fin amplitude ratio is observed; increasing of fin amplitude ratio improves the thermal efficiency and effective efficiency up to the critical Reynolds number. The peak thermal efficiency of 85% is observed and thermo hydraulic efficiency of 80.16% is found at fin pitch ratio of 0.05 and fin amplitude ratio of 0.125. The maximum thermo hydraulic performance enhancement is 15.7% as it compared simple conventional solar triangular duct air extractors. The design plots are developed to select the performance parameters to attain required temperature rise values. © 2022 Taylor & Francis Group, LLC.Item Thermohydraulic Efficiency of a Solar Air Heater in the Presence of Graded Aluminium Wire Mesh—A Combined Experimental–Numerical Study(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Diganjit, R.; Gnanasekaran, N.; Mobedi, M.In this work, aluminium wire mesh (WM) samples with 3, 9, and 18 pores per inch (PPI) and porosities of 0.894, 0.812, and 0.917, respectively, were combined together to form graded structures including 3-9-18, 9-18-3, and 18-3-9 PPIs. A 5 mm thickness for each WM was considered for a length of 2 m and inserted into a single-pass solar air heater (SAH) in which the height of the SAH was 120 mm. For the numerical analysis, a 3D numerical model was considered in ANSYS fluent software, and the Rosseland radiation model renormalization group (RNG) k-ε enhanced wall function was incorporated to account for solar radiation. The local thermal equilibrium (LTE) model was considered to obtain the heat-transfer characteristics of the WM. The numerical results of the thermohydraulic performance parameter (THPP) of the 9-18-3 PPI WM were 13.04% and 11.92% higher than the 3-9-18 and 18-3-9 PPI samples, respectively. Later, 25% of the 9-18-3 graded wire mesh (GWM) was considered at four different locations, i.e., 0, 0.5, 1, and 1.5 m away from the inlet, and analysed to obtain the best location for efficient heat transfer. The computational results show that 1.5 m away from the inlet is the best location among the different locations considered. The experimental results of the GWM at 1.5 m away from the inlet demonstrated a 20.91% and 23.32% increase in thermal efficiency compared to the empty channel for the 0.027 kg/s and 0.058 kg/s mass flow rates, respectively. From numerical-cum-experimental analysis, it was found that inserting 25% length of GWM of the entire length of the test section at a distance of 1.5 m from the inlet in single pass SAH improves the overall performance of the empty channel of single-pass SAH. © 2023 by the authors.Item Detailed thermo-hydraulic investigation of 3D octet lattice structure integrated heat sink(Elsevier Ltd, 2025) Narkhede, A.; Gnanasekaran, N.; Yadav, A.K.The present research work examined the thermo-fluidic characteristics of a heat sink packed with octet-structured periodic metal foam having varying porosity (0.83–0.93) and unit cell lengths (UCL) of 2.5–5 mm for electronic cooling application. AlSi10Mg material is considered for the octet lattice structure with water as the cooling medium, with the inlet velocity ranging from 0.02 to 0.05 m/s and a steady heat flux of 10 W/cm2 applied at base of the substrate. The effect of the porosity, unit cell length, and inlet velocity on pressure gradient, friction factor, Nusselt number, wall temperature, heat transfer coefficient, and thermo-hydraulic performance parameter is analyzed. Larger pressure gradients are observed for lower values of porosity and unit cell length, with a maximum value of approximately 5000 Pa/m for the thermal system having 0.83 porosity, 2.5 mm UCL, and 0.05 m/s inlet velocity. The wall temperature drops with a rise in inlet velocity and a reduction in porosity and UCL, with the lowest value of 311 K for the case of 0.83 porosity, 2.5 mm UCL, and 0.05 m/s inlet velocity. The case of 0.83 porosity, 5 mm UCL, and 0.02 m/s velocity was determined as optimum design based on thermo-hydraulic performance parameter. © 2024Item 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.Item A novel optimized liquid cooled heat sink integrated with 3D lattice structure under different blockage ratios(Elsevier Ltd, 2025) Narkhede, A.; Gnanasekaran, N.; Yadav, A.K.In this numerical work, investigation is focused on thermo-hydraulic nature of a periodic metal foam-integrated heat sink with an octet lattice-structure topology. Heat sink is partially filled with octet structure based periodic metal foam having 2.5 mm unit cell length with blockage ratios of 0.25/0.5/0.75/1, porosity of 0.83/0.87/0.91, and flow velocity of 0.02–0.05 m/s for electronic thermal management. The effect of porosity and blockage ratio on the wall temperature and pressure gradient of the heat sink is examined. Among all configurations, the lowest value of wall temperature of 311.24 K and the highest value of pressure gradient of 5091 Pa/m are observed for the case of blockage ratio 1, porosity 0.83, and flow velocity of 0.05 m/s. Additionally, the thermo-hydraulic performance enhancement owing to the partly packed configuration is observed based on the enhancement ratio and thermo-hydraulic performance parameter (THPP). The highest enhancement ratio is observed for the case with a blockage ratio of 1, porosity of 0.83, and a velocity of 0.02 m/s. The thermal design with a velocity of 0.03 m/s, a blockage ratio of 0.75, and a porosity of 0.83 is considered the optimal design in accordance with the THPP, which has a value of approximately 1.7. © 2025 Elsevier Ltd