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ÖZDEMİR, MEHMED RAFET

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ÖZDEMİR

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MEHMED RAFET

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2022 - 20232
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Start date: 2020 × Subject: Engineering and Technology ×

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Now showing 1 - 2 of 2
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    PublicationOpen Access
    A review on laminar-to-turbulent transition of nanofluid flows
    (2022-11-01) ÖZDEMİR, MEHMED RAFET; Subaşı A., ÖZDEMİR M. R. , Estelle P.
    Nanofluids have emerged as powerful instruments in heat transfer applications due to their improved thermophysical properties. Additionally, many heat transfer equipments are started to be operated within the range of transitional flow regions in the advances in thermal management enhancement techniques. However, up to date, the friction factor and heat transfer coefficient features of nanofluids within the transitional flow regions and the effect of nanoparticle addition into the base fluid on the laminar-to-turbulent transition characteristics are still not understood clearly with contradictory published results. At this point, this paper comprehensively reviews the studies dealing with the nanofluid flow within the transitional flow regions for internal flow applications. After the presentation of applications of nanofluid flow in the transitional flow regions, the nanofluid properties such as nanoparticle type and concentration and base fluid type in the reviewed studies are given in detail. The pressure drop and heat transfer features of nanofluid flow within the transitional flow regions are distinctly identified and discussed for internal flows. The effect of the nanoparticle addition into the liquid on the transition onset is discussed with results from different research groups. A complete evaluation, challenges and further studies are proposed based on available results in the literature.
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    A new distributor selection methodology for refrigeration cycles
    (2023-01-01) ÖZDEMİR, MEHMED RAFET; Hacımusalar H. A., ÖZDEMİR M. R., Sökücü M. H., DALKILIÇ A. S.
    The pressure gradient analysis is important to be able to observe the homogeneity of the refrigerant and to choose the correct distributor equipment in refrigeration cycles. This research proposes a new method for determining the two-phase pressure gradient accurately compared to existing methods. Two-phase pressure gradient determination approach of Chisholm was modified by integrating the flow pattern map of Thome and Cioncolini. The thermophysical properties of refrigerant 404A were obtained through EES software and the proposed method was coded in the same software. The two-phase pressure gradient results of the proposed method were verified using the experimental data for the refrigerant 404A and compared with the commonly used methods and correlations. It was found that the proposed method predicted the experimental data of R404A better compared to other methods and correlations. The proposed method accurately determines the two-phase pressure drop under superheating and subcooling conditions for various tube wall thicknesses.