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Author: search.filters.author.Ranganayakulu, ChennuSubject: search.filters.subject.Heat exchanger

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Now showing 1 - 9 of 9
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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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    Condensation heat transfer and pressure drop of R-134a saturated vapour inside a brazed compact plate fin heat exchanger with serrated fin
    (Springer, 2016-05) Ranganayakulu, Chennu
    This paper presents the experimental heat transfer coefficient and pressure drop measured during R-134a saturated vapour condensation inside a small brazed compact plate fin heat exchanger with serrated fin surface. The effects of saturation temperature (pressure), refrigerant mass flux, refrigerant heat flux, effect of fin surface characteristics and fluid properties are investigated. The average condensation heat transfer coefficients and frictional pressure drops were determined experimentally for refrigerant R-134a at five different saturated temperatures (34, 38, 40, 42 and 44 °C). A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 22 kg/m2s. In the forced convection condensation region, the heat transfer coefficients show a three times increase and 1.5 times increase in frictional pressure drop for a doubling of the refrigerant mass flux. The heat transfer coefficients show weak sensitivity to saturation temperature (Pressure) and great sensitivity to refrigerant mass flux and fluid properties. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow. Correlations are provided for the measured heat transfer coefficients and frictional pressure drops.
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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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    Steady state and transient analysis of compact plate-fin heat exchanger fins for generation of design data using CFD
    (Emerald, 2016-03) Ranganayakulu, Chennu
    The purpose of this paper is to carry out numerical modeling of single-blow transient analysis using FLUENT porous media model for estimation of heat transfer and pressure drop characteristics of offset and wavy fins
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    Flow boiling heat transfer and pressure drop analysis of R134a in a brazed heat exchanger with offset strip fins
    (Springer, 2017-05) Ranganayakulu, Chennu
    The saturated flow boiling heat transfer and friction analysis of R 134a were experimentally analyzed in a brazed plate fin heat exchanger with offset strip fins. Experiments were performed at mass flux range of 50–82 kg/m2 s, heat flux range of 14–22 kW/m2 and quality of 0.32–0.75. The test section consists of three fins, one refrigerant side fin in which the boiling heat transfer was estimated and two water side fins. These three fins are stacked, held together and vacuum brazed to form a plate fin heat exchanger. The refrigerant R134a flowing in middle of the test section was heated using hot water from upper and bottom sides of the test section. The temperature and mass flow rates of water circuit is controlled to get the outlet conditions of refrigerant R134a. Two-phase flow boiling heat transfer and frictional coefficient was estimated based on experimental data for offset strip fin geometry and presented in this paper. The effects of mass flux, heat flux and vapour quality on heat transfer coefficient and pressure drop were investigated. Two-phase local boiling heat transfer coefficient is correlated in terms of Reynolds number factor F, and Martinelli parameter X. Pressure drop is correlated in terms of two-phase frictional multiplier ϕ f , and Martinelli parameter X.
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    Boiling of R134a in a Plate-Fin Heat Exchanger Having Offset Fins
    (ASME, 2015-12) Ranganayakulu, Chennu
    This paper presents experimental results on boiling heat transfer of R134a in a compact plate fin heat exchanger. The exchanger is made of aluminum and has high density offset fins (30 fins/in.). Such heat exchangers are widely used in air separation industry and aerospace applications because of their high compactness and low weight. The test heat exchanger is attached to a vapor cycle refrigeration basic module to study the effects of boiling phenomena and its influence on performance as there is limited information available for this type of fins. This in turn allows for discussion on boiling mechanism of R134a inside the fins using the water circuit on the other side of the test heat exchanger. The water side single phase heat transfer coefficient (Colburn j factor) is calculated using the cfd tool fluent and validated with available open literature. The results are presented for heat fluxes up to 5500 W/m2 and mass fluxes up to 20 kg/(m2s) with water side flow rate varying from 0.033 to 0.17 kg/s for water temperatures of 10, 15, 20, 25, and 30 °C.
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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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    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.