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Sudhanshu Pandey(판데이수단슈),Yong Gap Park(박용갑),Man Yeong Ha(하만영) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Natural convection inside a square enclosure containing an internal circular cylinder in the presence of non-Newtonian power law fluid is investigated using commercial CFD tool Fluent. The effects of Rayleigh number (103≤ Ra ≤106) and power index (0.6≤ n≤ 1.6) on flow and heat transfer characteristics are demonstrated for a fixed value of Prandtl number of 10. The internal cylinder is placed at three different positions along the vertical centerline. The flow experienced a transition from steady to unsteady state at n=0.6 under the shear thinning regime at Ra=106. The time and surface-averaged Nusselt number found to be a decreasing function of the power law index in all the cases considered.
Sudhanshu Pandey,Yong Gap Park,Young Min Seo,Man Yeong Ha 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.10
The objective of present study is to carry out an unsteady numerical analysis to investigate the buoyancy-driven flows in a square enclosure containing an inner circular cylinder. The square enclosure is filled with dilatant fluids commonly known as shear thickening fluids. The inner circular cylinder is placed at the center of the square enclosure. The effects of Prandtl number (10, 100 and 1000) and Rayleigh number (10 3 to 10 6 ) on heat transfer characteristics are reported. The power-law index (n) varied from 1.0-1.6 where n = 1 corresponds to the Newtonian fluid. The heat transfer characteristics are almost insignificant to the change in Prandtl number. The flow and heat transfer characteristics diminished in square enclosure when filled with dilatant fluid in comparison to the Newtonian fluid. The present study demonstrates the adequacy of incorporating artificial neural network model in estimating the heat transfer characteristics.
Sudhanshu Pandey,Hyun Woo Cho,최훈기,Yong Gap Park,서영민,하만영 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.4
The thermal and flow characteristics at Ra = 10 7 were evaluated in a square cavity containing a circular cylinder in different places along the diagonal and horizontal centerlines. The enclosure contained non-Newtonian fluids of pseudoplastic and dilatant natures. The power-law index was varied in the range of 0.6-1.6 with an interval of 0.2 and a fixed Prandtl number of 10. The effects on the laminar natural convection are reported. The flow regimes were categorized as steady symmetric, steady asymmetric, non-periodic unsteady symmetric, non-periodic unsteady asymmetric, periodic unsteady symmetric, and periodic unsteady asymmetric. Artificial neural network was used to predict the thermal performance in the enclosure. The thermal transport in cases of n < 1 was much higher than that in cases of n > 1. The ANN model was effective in estimating the heat transfer performance with appropriate training.
Sudhanshu Pandey,박용갑,하만영 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.7
Buoyancy-driven flows were investigated inside an enclosure with an inner cylinder embedded within it. The square enclosure contains the power law fluids. The effects are reported for the position of the cylinder along the horizontal and diagonal directions on the flow and thermal characteristics based on a rigorous unsteady numerical analysis. The cylinder was placed at several locations along the diagonal near the top-left corner, the center, and near the bottom right corner. The cylinder was also placed along the horizontal centerline near the right wall. This paper reports the effects of shear thickening and thinning fluids on the heat transfer mechanism in the enclosure. The thermal characteristics were more pronounced when the cylinder was near the bottom right corner than when near the top left corner and at the center. Pseudoplastic and dilatant fluids can be used in applications requiring increased and decreased heat transfer rates, respectively.
Sudhanshu Pandey,박용갑,Man Yeong Ha 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.8
The present study deals with an unsteady laminar free convection inside the annuli confined between an outer square enclosure and an inner circular cylinder. The annuli are filled with non-Newtonian power law fluids. The inner cylinder is located at three positions along the vertical center line. The unsteadiness arising due to bifurcation of flow from steady state is also reported in this study. The flow characteristics were found to be steady in nature in case of shear thickening fluid. However, most of the cases in the shear thinning fluid regime are found to be unsteady in nature with periodic and non-periodic fluctuations. The bifurcation of the flow from steady to unsteady state is mainly governed by the location of the cylinder as well as the characteristics of non-Newtonian fluid. The Bernard cells arising due to very high convective flow at Ra = 107 are also observed in the flow fields.
Pandey, Sudhanshu,Park, Yong Gap,Ha, Man Yeong Pergamon Press 2019 International journal of heat and mass transfer Vol. No.
<P><B>Abstract</B></P> <P>Natural convection has been extensively studied due to its presence in many engineering applications. It is one of the most important modes of heat transfer and arises due to buoyancy-induced flows resulting from temperature differences. This review presents a detailed summary of numerical and experimental studies related to laminar natural convection in enclosures with and without internal bodies. Square, circular, and elliptical cylinders are mostly considered as internal bodies. The presence of internal bodies makes significant changes in the flow characteristics within the enclosure. The effects on the flow regime and thermal fields of various parameters have been discussed in detail, including the Rayleigh number, aspect ratio, position of internal bodies, number of internal bodies, and inclination angle. The different flow regimes depending on the input parameters are categorized based on observations made from flow and thermal patterns. This review discusses various methodologies used by a large group of researchers to improve the hydrodynamic and thermal behavior for buoyancy-driven flows within an enclosure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Review on numerical and experimental studies pertaining to natural convection in enclosures. </LI> <LI> Effect of internal bodies such as square, circular and elliptical cylinder on flow mechanism. </LI> <LI> Summarization of different methodologies used to improve the thermal behavior of buoyancy driven flows within an enclosure. </LI> <LI> Effect of wall boundary conditions, position and number of internal bodies. </LI> <LI> Categorization of flow regimes and the factors affecting the transition from steady to unsteady state. </LI> </UL> </P>
Understanding the electrocatalysis OER and ORR activity of ultrathin spinel Mn3O4
Chinmayee Chowde Gowda,Ankita Mathur,Arko Parui,Partha Kumbhakar,Prafull Pandey,Sudhanshu Sharma,Amreesh Chandra,Abhishek K. Singh,Aditi Halder,Chandra Sekhar Tiwary 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.113 No.-
Rapid depletion of non-renewable sources has made us look into possible green energy alternatives tomeet energy challenges. Electrocatalytic reactions involving oxygen evolution reaction (OER) and oxygenreduction reaction (ORR) play crucial roles in assisting the derivation of clean forms of energy. Here, wedemonstrate that few layers of the manganese oxide: hausmannitene (atomically thin two dimensional(2D-Mn3O4) can be exfoliated from its bulk form hausmannite (Mn3O4). Most significantly, the hausmanniteneexhibits catalytic activity towards oxygen reduction and evolution reactions. The hausmannitenehas enhanced Mn(III) ions (65%) compared to its parent structure hausmannite (31%). The Mn(III) ionsin a distorted lattice show the highest catalytic activity towards OER performance with the oxygen electrodeactivity (DE) of 1.08 eV for hausmannitene. The density functional theory (DFT) calculations, confirmedthe presence of both Mn(III) and Mn(II) sites on the (112)-oriented surface of Mn3O4 which arehighly active for OER and ORR, having vacant and filled orbitals of lowest and highest energy, respectively. Increased oxidation sites aiding to better performance of 2D structure was theoretically manifested. Therefore, demonstrating that similar mechanisms can be used to explore other 2D oxides aspossible efficient stable electrocatalyst substitute for energy conversion.