Department of Mechanical engineering

Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1921

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Subject: search.filters.subject.CFD

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Now showing 1 - 10 of 14
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    Experimental and CFD analysis of multi nozzle ejector system for aircraft compact heat exchanger applications
    (Taylor & Francis, 2021-10) Ranganayakulu, Chennu
    In the present study, analysis of multi-nozzle ejector systems for aircraft compact heat exchanger applications is performed. CFD procedure is validated with experimental data of a single-nozzle ejector. Experimentation is carried out with a multi-nozzle ejector to evaluate the performance of the system at ambient temperature (307 K). Based on the pressure drop data obtained from the experiment, the computational domain for CFD studies is simplified. Further the analysis of air ejector systems at higher operating temperature (813 K) is performed. Primary air inlet temperatures and pressure are varied as parameters. Velocity contour, pressure contour and temperature contours are plotted for cold and hot fluid cases. High pressure zones are observed in the mixing regime of primary and secondary fluid. Improper mixing of primary and secondary fluid is observed. The mass ratio is reduced with increase in primary pressure. Based on the CFD results at high temperature, the performance of the compact heat exchanger is computed using the heat exchanger carpet curve for the different secondary (cold) air flows induced by the ejector.
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    Colburn ‘j’ Factor and Fanning Friction Factor ‘f’ Correlations of Triangular Plain Fin Surface of a Compact Heat Exchanger Using CFD
    (Scientific net, 2015) Ranganayakulu, Chennu
    This paper presents the heat transfer and friction coefficient correlations for triangular plain fin surfaces of plate fin compact heat exchanger. It will be prohibitively expensive and time consuming to fabricate heat exchanger cores and conduct experiments over reasonable ranges of all the geometric variables. In contrast, it is relatively easy and cost effective to carry out a parametric study through numerical simulation and derive acceptable correlations for use in industry. A numerical model has been developed for the triangular plain fin of plate fin heat exchanger. The CFD analysis is carried out using FLUENT 12.1, Colburn factor j and fanning friction factor f are calculated for different Reynolds numbers. These values are compared with the available literature data of j and f factors. The correlations have been expressed in terms of two separate equations over the low and high Re regions along with dimensionless geometric parameters.
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    Development of Colburn j Factor and Fanning Friction Factor Correlations for Compact Surfaces of the Triangular Perforated Fins Using CFD
    (Taylor & Francis, 2015-07) Ranganayakulu, Chennu
    The necessity of increased heat transfer surface area has resulted in the development of compact heat exchangers, which are widely used in the aerospace and automobile industries. Hence perforations are made on triangular plain fins to study the effects on the heat transfer coefficient. A numerical model has been developed for the perforated fin of a triangular plate fin heat exchanger. Perforated fin performance has been analyzed with the help of computational fluid dynamics (CFD) by changing the various parameters of the fin. The Colburn j factor and the Fanning friction factor are calculated for different Reynolds numbers. The values of the Colburn j factor and the Fanning friction factor are validated for known geometric fins with available data in the literature and extended to triangular perforated fins. The correlations have been developed between Reynolds number, Colburn j factor, and Fanning friction factor by taking into account fin height, fin thickness, and fin spacing. The present numerical analysis is carried out for air media.
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    The single-blow transient testing technique for offset and wavy fins of compact plate-fin heat exchangers
    (Elsevier, 2017-01) Ranganayakulu, Chennu
    A single-blow transient test technique is employed to measure the Colburn j factor versus Reynolds number characteristics of high efficiency compact heat exchanger surfaces having offset and wavy fins. Using the experimental data, the NTU values are estimated for 5 types of fins. The measured data is evaluated using the maximum slope method to obtain the corresponding heat transfer coefficient in terms of Colburn j factor, and then is compared with the available correlations of theoretical steady state CFD model. In this analysis, the effects of non-adiabatic side walls and longitudinal heat conduction on the exit fluid temperature response and NTU values are discussed. The test core pressure drops are also measured, and the pressure drop components of entrance, acceleration, core friction and exit losses are compared with the CFD results.
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    Development of colburn ‘j’ factor and fanning friction factor ‘f’ correlations for compact heat exchanger plain fins by using CFD
    (Springer, 2013-03) Ranganayakulu, Chennu
    A numerical model has been developed for plain fin of plate fin heat exchanger. Plain fin performance has been analyzed with the help of CFD by changing the various parameters of the fin, Colburn ‘j’ and fanning friction ‘f’ factors are calculated. These values compared with the standard values. The correlations have been developed between Reynolds number Re, fin height h, fin thickness t, fin spacing s, Colburn factor ‘j’ and friction factor ‘f’.
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    Development of heat transfer coefficient and friction factor correlations for offset fins using CFD
    (Emerald, 2011-11) Ranganayakulu, Chennu
    In aerospace applications, due to the severe limitations on the weight and space envelope, it is mandatory to use high performance compact heat exchangers (CHEs) for enhancing the heat transfer rate. The most popularly used ones in CHEs are the plain fins, offset strip fins (OSFs), louvered fins and wavy fins. Amongst these fin types, wavy and offset fins assume a lot of importance due to their enhanced thermo‐hydraulic performance. The purpose of this paper is to investigate the influence of geometrical fin parameters, in addition to Reynolds number, on the thermo‐hydraulic performance of OSFs.
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    Computational Approaches in Industrial Centrifugal Pumps
    (Intechopen, 2022-09) Bhattacharyya, Suvanjan
    The growing energy demand is expected to be met with increased oil and gas production. Hence, there is a need to design high-performance industrial centrifugal pumps. Recent improvements in CFD are considered as a valuable research tool to investigate the flow inside the pump and its influence on the performance of the centrifugal pump. The scope of the chapter is to emphasize the use of CFD and theoretical analysis for design and to show the prospect of improving the efficiency of a centrifugal pump. The chapter discusses the computational approaches to the CAD modeling and CFD simulation of the industrial centrifugal pumps, and the strategies and methodologies adopted. The chapter would be relevant and useful to both the pump designers, manufacturers, and industrial users.
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    Numerical Analysis of Heat Transfer and Pressure Drop in a Square Channel with Novel Centre Hole Inclined Ribs
    (Springer, 2023-04) Bhattacharyya, Suvanjan
    In present simulation analysis, heat transfer, pressure drop and thermal performance factor in a square channel equipped with inclined ribs with central hole is investigated. The study is conducted in turbulent flow regime with Reynolds number ranging from 10000 to 80000. The variable parameters are pitch ratio (y = p/D = 0.5, 1.0 and 1.5), hole ratio (h = d/D = 0.1 and 0.2) and rib angle (θ =30°, 45°, and 60°). ANSYS Fluent 19.0 is used for simulations and governing equation are solved using RANS turbulence model. It is revealed from the investigation that presence of inclined ribs enhance the heat transfer and pressure drop. For the case of inclined ribs with central hole, enhancement is further increased. For all the cases the thermal performance factor remains higher than unity.
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    Computational heat transfer analysis of a counter-flow heat exchanger with fins
    (RDME, 2015) Bhattacharyya, Suvanjan
    A numerical work has been conducted to examine laminar flow and heat transfer characteristics in a two-dimensional isothermal-fluxed circular-duct fitted horizontal with finned tapes. The computations are based on the finite volume method with the SIMPLE algorithm implemented. This paper reports the Computational Fluid Dynamics (CFD) modelling studies on heat transfer, friction factor and thermal performance of a counter-flow heat exchanger equipped with two types of tube insert including fins. The principle of heat transfer enhancement in the core flow of tube has been proposed to improve the temperature uniformity and heat transfer enhancement in the boundary flow of tube. The studied the temperature profile and velocity profile was obtained by the fins inserts with an inclined angle of 90°. The results have also revealed that the difference between the heat transfer rates obtained from two models with fins and without fins. The CFD predicted results were used to explain the observed results in terms of swirl intensity.
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    Computational investigation of heat transfer enhancement by alternating inclined ribs in tubular heat exchanger
    (Inder Science, 2017) Bhattacharyya, Suvanjan
    This paper encapsulates results of a numerical investigation on flow and heat transfer of an incompressible medium with constant properties through an isothermal circular tube with alternating inclined ribs. Simulations are conducted for laminar, transitional, and turbulent flow regimes. As turbulence model, the transitional shear stress transport model is employed. The problem is investigated for four rib angle of attack values, as well as for a plain tube without any ribs. All configurations are observed to lead to a thermal performance factor close to or greater than unity. Within the investigated range, the larger thermal performance factors are observed to occur for the intermediate Reynolds numbers. Maximum values in the range 2.0-2.5 are predicted for the Reynolds number of 2,000, where a subsequent drop to values within the range 1.0-1.5 are found to occur for Reynolds numbers around 3,000-4,000, which may be attributed to the transitional effects.