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    Analysis of pressure distribution of turbulent asymmetric flow in a flat duct symmetric sudden expansion with small aspect ratio
    (Iop Publishing Ltd, 2004) Canbazoglu, S; Bozkir, O
    This paper describes the pressure distribution of turbulent airflow through a flat duct containing one-dimensional symmetric sudden expansion in cross-sectional area encountered frequently in plate heat exchangers and other devices of practical importance. The pressure distributions of turbulent asymmetric airflow through constant width flat ducts having modest expansion ratios of 2, 2.5 and 3, aspect ratios of the expansion of 0.40, 0.26 and 0.20 and modest area ratios of the expansion of 1/3, 1/2.5 and 1/2 were investigated experimentally. The axial and vertical pressure distributions of the turbulent asymmetric flow with relatively small Reynolds numbers (Re-Dh = uD(h)/v = 12 000,4887 and 4125) in downstream cross section of the duct were analyzed. The variations of pressure coefficient with local Reynolds numbers were also investigated. Turbulent flow in flat ducts with symmetric sudden expansion has not sufficiently been studied contrary to axisymmetrical or two-dimensional case for which a large numbers of papers can be found in the literature. This experimental study fulfills this gap and shows that the flow is asymmetric as in a two-dimensional case. It also brings interesting data for numerical simulations for the presented flat duct configurations. These data,concern the axial and vertical distribution of pressure coefficient, the axial velocity in the duct and Reynolds numbers based on the hydraulic diameter, the step height or the local axial distance of the duct. The results obtained complement and extend the previous results, and show that the expansion ratio and Reynolds number affect the flow field. (C) 2004 Published by The Japan Society of Fluid Mechanics and Elsevier B.V. All rights reserved.
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    Unsteady thermal performance analysis of a room with serial and parallel duct radiant floor heating system using hot airflow
    (Elsevier Science Sa, 2004) Bozkir, O; Canbazoglu, S
    In this study, the unsteady thermal performance of a test room heated by circulating hot airflow under the floor was analyzed with a developed mathematical model based on heat transfer equilibrium among the air flow, the floor and the indoor air. The time variations in the indoor air temperature for the serial duct floor heating system were investigated theoretically and experimentally. The time variations in the floor surface and the indoor air temperatures were predicted theoretically for the parallel duct floor heating system. Experiments on the time variations of the dimensionless numbers such as Nu for the airflow in duct and the indoor air, Gr for the indoor air and the heat ratios of convection and radiation to total heat for the serial duct floor heating system were performed. The theoretical and experimental results showed a good agreement. (C) 2004 Elsevier B.V. All rights reserved.