Department of Mechanical engineering

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1996 - 199962000 - 20096

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Author: search.filters.author.Ranganayakulu, ChennuEnd date: 2009

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Now showing 1 - 10 of 12
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    The combined effects of wall longitudinal heat conduction, inlet fluid flow nonuniformity and temperature nonuniformity in compact tube–fin heat exchangers: a finite element method
    (Elsevier, 1999-01) Ranganayakulu, Chennu
    A finite element analysis of a crossflow tube–fin compact heat exchanger is presented. The analysis takes into account the combined effects of one-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow and temperature distributions on both hot and cold fluid sides. A mathematical equation is developed to generate different types of fluid flow⧹temperature maldistribution models considering the possible deviations in fluid flow. Using these fluid flow⧹temperature maldistribution models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction and flow⧹temperature nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performance deteriorations are quite significant in some typical applications due to the combined effects of longitudinal heat conduction, temperature nonuniformity and fluid flow nonuniformity on crossflow tube–fin heat exchanger.
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    The Effects of Inlet Temperature Nonuniformity in a Crossflow Plate-fin Heat Exchanger
    (IHTC, 2002) Ranganayakulu, Chennu
    A finite element analysis of a cross-flow plate-fin compact heat exchanger is presented. The analysis takes into account the effects of non-uniform inlet fluid temperature distributions on both hot and cold fluid sides. Temperature mal-distribution models are generated considering possible deviations in fluid temperatures. Using fluid temperature mal-distribution models, exchanger effectiveness and its deterioration due to the effects of temperature non-uniformity are calculated for various design and operating conditions of the exchanger. It was found that the performance deviations are quite significant in some typical applications due to the temperature non-uniformity on a cross-flow plate-fin heat exchanger.
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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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    Heat transfer from horizontal tubes in pool boiling: influence of three-dimensional heat conduction in the wall of the evaporator tube—a finite element analysis
    (Springer, 2005-10) Ranganayakulu, Chennu
    In pool boiling, the electrically heated tube releases the energy non-uniformly to the liquid, due to different surface roughness and flowing liquid. The heat transfer coefficient therefore varies with axial and azimuthal position on the tube. Hence a finite element analysis has been carried out on a horizontal 1in. copper tube for evaporation in pool boiling for three-dimensional conduction heat transfer. A test tube has been made with different surface structures, tested and analysed for heat conduction effects. It has been observed that significant amount of heat flows in azimuthal and axial directions in addition to the heat flow in radial direction.
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    The combined effects of inlet fluid flow and temperature nonuniformity in cross flow plate-fin compact heat exchanger using finite element method
    (Springer, 1997-06) Ranganayakulu, Chennu
    An analysis of a crossflow plate-fin heat exchanger accouning for the combined effects of inlet fluid flow nonuniformity and temperature nonuniformity on both hot and cold fluid sides is carried out using a Finite Element Model. A mathematical equation is developed to generate different types of fluid flow/temperature maldistribution models considering the possible deviations in inlet fluid flow. Using these fluid flow maldistribution models, the exchanger effectiveness and its deteriorations due to flow/temperature nonuniformity are calculated for entire range of design and operating conditions. It was found that the performance deteriorations are quite significant in some typical applications due to inlet fluid flow/temperature nonuniformity.
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    The combined effects of wall longitudinal heat conduction and inlet fluid flow maldistribution in crossflow plate-fin heat exchangers
    (Springer, 2000-05) Ranganayakulu, Chennu
    An analysis of a crossflow plate-fin compact heat exchanger, accounting for the combined effect of two-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow distribution on both hot and cold fluid sides is carried out using a finite element method. Using the fluid flow maldistribution models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction and flow nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performance deteriorations are quite significant in some typical applications due to the combined effects of wall longitudinal heat conduction and inlet fluid flow nonuniformity on crossflow plate-fin heat exchanger.
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    Bubble formation with pool boiling on tubes with or without basic surface modifications for enhancement
    (Elsevier, 2004-04) Ranganayakulu, Chennu
    Bubble formation is investigated on a single, horizontal copper tube (D=25.4 mm) before and after applying surface modifications in the form of macrocavities with comparatively simple shapes (size: 200 × 100 μm on the tube surface and 50 μm in depth) in order to link bubble formation and heat transfer to the geometric features of the cavities. Two kinds of cavities exist in parallel, one with reduced mouth width (so-called “main structure”) and one without this reduction (“secondary structure”). Pool boiling experiments with different organic liquids have been performed with variation of heat flux and saturation pressure. The resulting bubble formation on the tubes with and without surface modifications is discussed in terms of characteristic parameters such as local distribution and temporal activation behavior of the nucleation sites for bubble formation at active nucleation sites (“primary bubbles”) or for bubbles released from the macrocavities (“secondary bubbles”).
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    The effects of longitudinal heat conduction in compact plate-fin and tube-fin heat exchangers using a finite element method
    (Elsevier, 1997-04) Ranganayakulu, Chennu
    An analysis of the crossflow plate-fin, crossflow tube-fin, counterflow plate-fin and parallel flow plate-fin compact heat exchangers accounting for the effect of ‘longitudinal heat conduction’ through the exchanger wall is carried out using a finite element method. The exchanger effectiveness and its deterioration due to the longitudinal heat conduction effect have been calculated for various designs and operating conditions of the exchanger. The results indicate that the thermal performance deterioration of crossflow plate-fin, crossflow tube-fin and counterflow plate-fin heat exchangers due to longitudinal heat conduction may become significant especially when the fluid capacity rate ratio is equal to one and when the longitudinal heat conduction parameter is large.
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    The combined effects of longitudinal heat conduction, flow nonuniformity and temperature nonuniformity in crossflow plate-fin heat exchangers
    (Elsevier, 1999-07) Ranganayakulu, Chennu
    An analysis of a crossflow plate-fin compact heat exchanger, accounting for the combined effects of two-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow and temperature distribution is carried out using a finite element method. A mathematical equation is developed to generate different types of fluid flow/temperature maldistribution models considering the possible deviations in fluid flow. Using these models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction, flow nonuniformity and temperature nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performance variations are quite significant in some typical applications.
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    The combined effects of wall longitudinal heat conduction, inlet fluid flow nonuniformity and temperature nonuniformity in compact tube–fin heat exchangers: a finite element method
    (Elsevier, 1999-01) Ranganayakulu, Chennu
    A finite element analysis of a crossflow tube–fin compact heat exchanger is presented. The analysis takes into account the combined effects of one-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow and temperature distributions on both hot and cold fluid sides. A mathematical equation is developed to generate different types of fluid flow⧹temperature maldistribution models considering the possible deviations in fluid flow. Using these fluid flow⧹temperature maldistribution models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction and flow⧹temperature nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performance deteriorations are quite significant in some typical applications due to the combined effects of longitudinal heat conduction, temperature nonuniformity and fluid flow nonuniformity on crossflow tube–fin heat exchanger.