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Subject: search.filters.subject.Computational Fluid Dynamics

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Now showing 1 - 8 of 8
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    Heat Transfer and Flow Friction correlations for Compact Wavy Plate Fin Heat Exchanger
    (JNTU, 2008) Ranganayakulu, Chennu
    The most popularly used fins in Compact Heat Exchangers (CHEs) are the plain fins, offset strip fins, louvered fins and wavy fins. Thermo hydraulic performance of the above mentioned fins are strongly depends upon the geometric parameters and flow parameters. The wavy fin performance is generally evaluated based on the fin thickness, wavelength, curvature radius, amplitude, fin spacing and fin height. The objective of the present study is focused on investigation of the influence of above mentioned fin parameters and establishing a correlation in terms of dimensionless parameters such as Colburn factor (j), Fanning friction factor (f), geometrical parameters and flow parameters. A CFD approach has been used for numerical analysis of different fin configurations to determine the thermo-hydraulic parameters. The investigations include the study of flow pattern for laminar and turbulent regimes and validated with available data.
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    Turbulence Models Commonly Used in CFD
    (Intechopen, 2021-08) Bhattacharyya, Suvanjan
    Here we provide an overview of some of the most commonly used turbulence models used in current CFD modeling. We compare the governing equations, applications of use, and results between the models. Finally, we provide our own recommendations, based on more than two decades of collaborative research.
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    Spark Advance Modeling of Hydrogen-Fueled Spark Ignition Engines Using Combustion Descriptors
    (ASME, 2018-08) Verma, Saket
    In-cylinder pressure-based combustion descriptors have been widely used for engine combustion control and spark advance scheduling. Although these combustion descriptors have been extensively studied for gasoline-fueled spark ignition (SI) engines, adequate literature is not available on use of alternative fuels in SI engines. In an attempt to partially address this gap, present work focuses on spark advance modeling of hydrogen-fueled SI engines based on combustion descriptors. In this study, two such combustion descriptors, namely, position of the pressure peak (PPP) and 50% mass fraction burned (MFB) have been used to evaluate the efficiency of the combustion. With a view to achieve this objective, numerical simulation of engine processes was carried out in computational fluid dynamics (CFD) software ANSYS fluent and simulation data were subsequently validated with the experimental results. In view of typical combustion characteristics of hydrogen fuel, spark advance plays a very crucial role in the system development. Based on these numerical simulation results, it was observed that the empirical rules used for combustion descriptors (PPP and 50% MFB) for the best spark advance in conventional gasoline fueled engines do not hold good for hydrogen engines. This work suggests revised empirical rules as: PPP is 8–9 deg after piston top dead center (ATDC) and position of 50% MFB is 0–1 deg ATDC for the maximum brake torque (MBT) conditions. This range may vary slightly with engine design but remains almost constant for a particular engine configuration. Furthermore, using these empirical rules, spark advance timings for the engine are presented for its working range.
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    Vortex dynamics around a fluctuating beam
    (AIP, 2023-05) Aneesh, A.M.
    Fluid Structure Interaction (FSI) analysis for fluctuating beam in viscous fluids has been carried out for the preliminary design of propeller-less underwater drones. The Immersed Boundary Method has been used to address a large variety of Fluid Structure Interaction problems such as insect flight, locomotion of fishes and batoid pieces etc.IB2d is an open-source MATLAB code developed by Battista, which can be used for solving two-dimensional Fluid Structure Interaction problems using the Immersed Boundary Method. The settings of IB2d solver have been verified by reproducing a flapping beam problem. The parameters for this problem have been changed to study the flow generated around a beam tethered at both ends and subjected to a perturbation of the beam in static fluid. The beam has been modelled as a setof Lagrangian points for a given length and stiffness value and the fluid around the beam is modelled as a Eulerian regionof certain viscosity and density. The beam has been perturbed from its equilibrium position by an ellipsoidal arc and the dynamics of vortices around the beams are analyzed both qualitatively and quantitatively. The simulations have been repeated by varying viscosities of the Eulerian region, varying length of the beam and varying stiffness values betweenthe Lagrangian points. The parametric study shows that the magnitude of vorticity around the beam reduces with increasein viscosity and stiffness It is also found that for the same curvature, the motion speed reduces with reduction in the beamlength.
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    Thermal-hydraulic characteristics and performance of 3D straight channel based printed circuit heat exchanger
    (Elsevier, 2016-04) Aneesh, A.M.
    CFD study is done to propose an efficient PCHE (Printed Circuit Heat Exchanger) model; used as a recuperator in International Thermonuclear Experimental Reactor (ITER). 3D steady-state conjugate heat-transfer simulations are done with helium as a working fluid and alloy 617 as the solid substrate. Effect of variation of thermo-physical properties, operating conditions and three different design modifications are studied. Thermal hydraulic performance is found better for single as compared to double banking and is the same for aligned as compared to the staggered arrangement of the hot and cold channels. PCHE models with hemispherical dimples are found to give better thermal hydraulic performance. The performance is presented for the variation of the heat transfer density (for a PCHE model) and the pressure drop (in the hot and cold channel). Various types of flow patterns are presented to analyze the thermal-hydraulic characteristics − leading to the heat transfer enhancement by the dimples.
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    Effects of wavy channel configurations on thermal-hydraulic characteristics of Printed Circuit Heat Exchanger (PCHE)
    (Elsevier, 2018-03) Aneesh, A.M.
    Printed Circuit Heat Exchanger (PCHE) is a widely chosen plate type compact heat exchanger for high pressure applications. The present work mainly focuses on two high pressure applications; firstly, Helium Cooling System (HCS) of Test Blanket Module (TBM) in International Thermonuclear Experimental Reactor (ITER) and secondly, Intermediate Heat exchangers (IHX) in Very High Temperature Reactors (VHTR). In this work, a reduced numerical model for a single banked PCHE core working in He-He counter flow circuit has been numerically modelled and verified against the results available in the literature. The same model is then extended for studying the effect of three wavy-channel configurations viz. triangular, sinusoidal and trapezoidal in a single banked PCHE core made of Alloy-617. The nature of local flow and heat transfer in the periodic channels has been studied by visualizing the vortex core using iso-normalized helicity surfaces. Thereafter, the thermo-hydraulic performances of these models are compared with straight channel PCHEs. Among the various models studied, the trapezoidal PCHE model is found to offer highest heat transfer with the largest pressure drop compared to sinusoidal, triangular and straight channel based PCHE models. A maximum of 41% increase in the heat transfer rate is predicted for the trapezoidal wavy channel compared to the straight channel PCHEs, for the tested operating conditions. For the sinusoidal and triangular wavy-channel PCHE configurations, the corresponding heat transfer advantages are predicted to be 33% and 28% respectively. The optimal thermo-hydraulic performance is also assessed, considering the thermal performance factor (TPF) obtained for all the three channels. The highest values of TPF are predicted for trapezoidal wavy channels (3.5) which is followed by sinusoidal (2.5) and triangular (1.5) wavy channels.
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    Parametric analysis and optimization of a latent heat thermal energy storage system for concentrated solar power plants under realistic operating conditions
    (Elsevier, 2021-08) Srinivasan, P.; Rai, Aakash Chand
    High-temperature latent heat thermal energy storage (LHTES) systems are currently being considered for integration into concentrated solar power (CSP) plants; however, the challenge is to properly design the LHTES system under real-world operating conditions. Thus, this numerical investigation studied the effects of the LHTES system's design parameters on its performance under periodic steady-state with charging and discharging ‘cutoff’ temperatures to mimic its real-world operation. The study found that with the incorporation of cutoff temperatures, the system's specific energy and storage effectiveness decreased by 74% and 68%, respectively, due to lower useful charging and discharging times. Furthermore, the study demonstrated that the system's useful charging and discharging time could be augmented by increasing the shell radius (R) or length (L) of the system, or by decreasing the system's tube radius (ro) or the velocity of the heat transfer fluid (um) that flows through the system. The system's geometrical parameters (R, L, and ro) and um also substantially influenced its performance, but in a different manner than their influence on charging-discharging times. For example, increasing R deteriorated the system's performance substantially. Thus, we proposed optimized designs that achieved high charging-discharging times as well as good performance levels, using the response surface methodology.
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    Heat Transfer Simulation by CFD from Fins of an Air Cooled Motorcycle Engine under Varying Climatic Conditions
    (World Congress on Engineering, 2011-07) Srinivasan, P.
    An air-cooled motorcycle engine releases heat to the atmosphere through the mode of forced convection. To facilitate this, fins are provided on the outer surface of the cylinder. The heat transfer rate depends upon the velocity of the vehicle, fin geometry and the ambient temperature. Many experimental methods are available in literature to analyze the effect of these factors on the heat transfer rate. However, an attempt is made to simulate the heat transfer using CFD analysis. The heat transfer surface of the engine is modeled in GAMBIT and simulated in FLUENT software. An expression of average fin surface heat transfer coefficient in terms of wind velocity is obtained. It is observed that when the ambient temperature reduces to a very low value, it results in overcooling and poor efficiency of the engine