Browsing by Author "Yurddas A."

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    Numerical analysis of mixed convection heat transfer in pulsating flow for a horizontal channel with a cavity heated from vertical side and below
    (2012) Selimefendigil F.; Yurddas A.
    In this study, a channel with a cavity heated from below and a left vertical side is numerically investigated for the mixed convection case in pulsating flow for a range of Richardson numbers (Ri = 0.1, 1, 10, 100) and Reynolds numbers of 300, 500, and 800 in the laminar flow regime. At the inlet of the channel, pulsating velocity is imposed for Strouhal numbers of 0.25, 0.5, 0.75 and 1 and velocity amplitude ratios of 0.7, 0.8, and 0.9. The effect of the pulsation frequency, amplitude, Reynolds number, and Richardson number on heat transfer enhancement is analyzed numerically. The results are presented in terms of streamlines, isotherm plots, and averaged Nusselt number plots. Transfer function plots for the Nusselt number response to single sinusoidal velocity forcing at the inlet and nonlinearity in the response is also provided. © 2012 by Begell House, Inc.
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    An analytical study on the entropy generation in flow of a generalized Newtonian fluid
    (Serbian Society of Heat Transfer Engineers, 2019) Aksoy Y.; Gurkan N.; Aksoy A.B.; Dogan Durgun D.D.; Yurddas A.
    In this study, an analytical investigation on pressure driven flow of Powell-Eyring fluid is conducted to understand the irreversibilities due to heat transfer and viscous heating. The flow between infinitely long parallel plates is considered as fully developed and laminar with constant properties and subjected to symmetrical heat fluxes from solid boundaries. The internal heating due to viscous friction accompanies external heat transfer, that is, viscous dissipation term is to be involved in the energy equation. As a cross-check, accuracy of analytical solutions is confirmed by a predictor-corrector numerical scheme with variable step size. © 2019 Society of Thermal Engineers of Serbia.
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    Prediction of heat and fluid flow in microchannel condensation
    (EDP Sciences, 2019) Basaran A.; Benim A.C.; Yurddas A.
    The condensing flow inside the microchannel has gained importance as the microchannel heat exchangers are widely used in the industry. In this study, a number of numerical simulations on condensing flow inside the microchannel were conducted to investigate heat transfer characteristic. Circularmicrochannel geometries with the various diameters were considered. The Volume of Fluid model was used to model twophase flow. The phase change at the saturation temperature was modeled by the Lee model.In the considered geometries, different from the conventional channels, surface tension forces can be importantcomparedto other forces. Therefore, surface tension was considered in the simulations. Constant wall heatflux and constant saturation temperature were applied as simulation conditions, similar to actual operating conditions. The predictions were validated by comparisons with the experimental results that exist in the literature. A satisfactory agreement of the present predictions with the experimental data was observed. © The Authors, published by EDP Sciences, 2019.
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    Energy and exergy analysis of the heating and cooling system of a public building
    (Inderscience Publishers, 2020) Sevim S.; Yurddas A.
    Efficient use of energy spent in existing systems is of great importance in terms of energy saving. The aim of this study was to carry out the energy and exergy analyses of the existing heating and cooling systems of a public building and determine the system performances, and bring the system to a thermoeconomic structure by making necessary improvements. In the building, natural gas is used as energy source (fuel) in hot water boilers within the existing heating installation, and electricity is used as energy source in air-cooled water chillers within the cooling system. As a result of the calculations, it was determined that the biggest exergy destruction in the heating system was in the hot water boiler and the biggest exergy destruction in the cooling system was in the water chiller. Other point data obtained were evaluated and heating and cooling system efficiencies were determined. Copyright © 2020 Inderscience Enterprises Ltd.
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    Numerical Simulation of the Condensation Flow of the Isobutane (R600a) inside Microchannel
    (Taylor and Francis Ltd., 2021) Basaran A.; Benim A.C.; Yurddas A.
    A numerical investigation of the condensing flow of isobutane inside microchannel has been performed. Impact of mass flux, hydraulic diameter, and vapor quality on the heat transfer rate and pressure drop is determined. To this purpose, steady-state numerical simulations of condensation flow of isobutane have been performed at mass fluxes ranging from 200 to 600 kg/m2s inside a single circular microchannel with varying diameter. Similar to the usual operation conditions, the simulations have been conducted for constant saturation temperature and constant wall heat flux as the thermal boundary condition. The proposed model has been based on the volume of fluid approach, which is an interface tracking method. The Lee model has been used to model the phase change mass transfer at the interface. A verification study has been performed by comparing the proposed model results with the experimental and visual data available in the literature. The currently available correlations are assessed by comparisons with the simulation results. Based on the presently validated simulations, a new correlation has been proposed for the heat transfer coefficient and pressure drop of isobutane condensing flow inside small-scale channels. This is a novel aspect of the present paper, since such a correlation does not yet exist. © 2021 Taylor & Francis Group, LLC.