Faculty Publications
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Item Computation of fluid flow in double sided cross-shaped lid-driven cavities using Lattice Boltzmann method(Elsevier Ltd, 2018) Bhopalam, S.B.; Arumuga Perumal, D.A.; Yadav, A.K.This work implements Lattice Boltzmann method to compute flows in double-sided cross-shaped lid-driven cavities. Firstly, a complicated geometry which is a symmetrized version of the staggered lid-driven cavity namely, the double-sided cross-shaped lid-driven cavity with antiparallel uniform wall motion is studied employing Single as well as Two Relaxation time models. The streamline patterns and vorticity contours obtained for low to moderate Reynolds numbers (150–1000) are compared with published results and found to be in good accordance. Next, this code is extended to simulate flows in a double-sided cross-shaped lid-driven cavity with parallel uniform wall motion. The effect of three dimensionality is also studied for low Reynolds numbers. Lattice Boltzmann method is then used to investigate the oscillating double-sided cross-shaped lid-driven cavity with antiparallel and parallel wall motions. The movement and formation of primary and secondary vortices have been well captured with the variation of Reynolds numbers and oscillating frequencies for uniform and oscillating wall motions. Reasonable agreements with the established results have been observed for the double-sided cross-shaped cavity with uniform wall motions, while new results have been obtained in the case of oscillating wall motions. © 2018 Elsevier Masson SASItem Stability enhancement of supercritical CO2 based natural circulation loop using a modified Tesla valve(Elsevier B.V., 2020) Wahidi, T.; Chandavar, R.A.; Yadav, A.K.This article deals with the comparative investigation of instability phenomenon in supercritical CO2 based regular natural circulation loop and a new modified Tesla natural circulation loop. Two-dimensional computational fluid dynamics simulation is carried out for square loops. Fluid flow behaviour and performance of both the loops are determined over a range of pressures (80–100 bar) and heat inputs (500–2000 W). Results show that the use of a modified Tesla valve leads to better stabilization for all supercritical pressures and heat inputs. It is also found that loop with Tesla mitigates the temperature and velocity oscillations without reducing the heat transfer performance. A good agreement with existing correlations is also obtained in the present study. The unidirectional fluid flow circulation achieved in loop with Tesla valve, makes it an efficient technique to combat instability. © 2020 Elsevier B.V.Item Effect of loop tilting on the heat transfer and pressure drop in two-phase CO2 based natural circulation loop: An experimental study(American Society of Mechanical Engineers (ASME), 2021) Thippeswamy, L.R.; Yadav, A.K.The natural circulation loop (NCL) is widely used where the safe and economic heat transfer device is desired. However, the instability associated with the regular change in fluid flow behavior due to the imbalance between friction and buoyant forces is a major disadvantage. One of the erudite solutions to overcome this is to tilt the entire loop by a certain angle, with an inherent penalty in heat transfer and pressure drop. In the present study, experimental studies have been carried out on two-phase carbon dioxide (CO2) based NCL, which has gained popularity because of its compactness and higher heat transfer rate. Pressure drop and heat transfer performance of the loop for various tilt angles (0 deg, 30 deg, and 45 deg) in different planes (XY and YZ planes) have been investigated. Methanol is used as the external fluid in cold and hot heat exchangers in order to maintain low operating temperature in the loop. Results show that the tilting of the loop causes a marginal drop in the heat transfer rate of two-phase CO2 based NCL. Hence, tilting of the loop could be a solution to instability problem without conceding the performance of the loop. © © 2020 by ASMEItem Comparative studies on air, water and nanofluids based Rayleigh–Benard natural convection using lattice Boltzmann method: CFD and exergy analysis(Springer Science and Business Media B.V., 2022) Karki, P.; Arumuga Perumal, D.A.; Yadav, A.K.The present study incorporates laminar natural convection and entropy generation in Rayleigh–Benard (R–B) convection with air, water and alumina–water nanofluid as working fluids. The fluid flow and energy equations are solved using D2Q9 and D2Q5 LBM models, respectively. The effects of Rayleigh numbers (Ra = 5 × 103, 104, 105) and volume fractions (? = 0 to 0.08) of nanoparticles on heat transfer and irreversibility are investigated. Results show that the heat transfer evaluated based on Nusselt number is enhanced due to addition of nanoparticles in the base fluid. The maximum enhancement in Nusselt number is found to be 13.93% at Ra = 105 with 8% of nanoparticle in base fluid. The various irreversibilities considered in this study are thermal, fluid flow and total irreversibility, where fluid flow and total irreversibilities in the study depend on irreversibility ratio. The irreversibility ratios taken into account are 10–2, 10–3, 10–4 and 10–5. One facet of study shows the deviation in onset of critical Rayleigh number for air is 1.58%. The other facet indicates dimensionless heat transfer, fluid flow and total irreversibility decrease with the increase in volume fraction of nanoparticles in the base fluid. The analyzed results of irreversibilities are presented in normalized form. In addition, dimensionless entropy generation maps and Bejan number contours are also plotted. © 2021, Akadémiai Kiadó, Budapest, Hungary.Item CFD and exergy analysis of subcritical/supercritical CO2 based naturally circulated solar thermal collector(Elsevier Ltd, 2022) Biradar, M.K.; Parmar, D.N.; Yadav, A.K.Solar water heating system is inefficient during winter due to the chances of water freezing and higher viscosity at low temperatures. Several investigations are being done to increase the efficiency of the solar water heater using various secondary fluids for different climatic conditions. This paper emphasises on the study of heat transfer and fluid flow behavior of CO2 based naturally circulated indirect solar water heating system. Subcritical (liquid and vapour) and supercritical CO2 are considered as loop fluid, and the results are compared with water based system. Three-dimensional computational fluid dynamics simulations are carried out for two different weather conditions i.e., winter (278 K) and summer (305 K). Results are obtained for 33° collector inclination angle from horizontal at various operating pressures 50–70 bar for subcritical and 80–100 bar for supercritical CO2. The CO2 based system yields very high Reynolds number (subcritical liquid: ∼160 times; subcritical vapour: ∼204 times; supercritical vapour: ∼260 times) and very high Nusselt number (subcritical liquid: ∼14 times; subcritical vapour: ∼19.5 times; supercritical vapour: ∼48 times) compared to water based system. Supercritical CO2 based system exhibits 12% higher energy efficiency compared to water. Whereas, subcritical vapour based system exhibits 140% higher exergy efficiency relative to water based system. © 2022 Elsevier Ltd