Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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  • Article
    Citation - WoS: 33
    Citation - Scopus: 35
    Experimental and Numerical Investigation of Constructal Vascular Channels for Self-Cooling: Parallel Channels, Tree-Shaped and Hybrid Designs
    (Elsevier Ltd., 2016) Yenigün, Onur; Çetkin, Erdal
    In this paper, we show experimentally and numerically how a plate which is subjected to a constant heat load can be kept under an allowable temperature limit. Vascular channels in which coolant fluid flows have been embedded in the plate. Three types of vascular channel designs were compared: parallel channels, tree-shaped and their hybrid. The effects of channel design on the thermal performance for different volume fractions (the fluid volume over the solid volume) are documented. In addition, the effects of the number of channels on cooling performance have been documented. Changing the design from parallel channels to tree-shaped designs decreases the order of pressure drop. Hence increase in the order of the convective heat transfer coefficient is achieved. However, tree-shaped designs do not bathe the entire domain, which increases the conductive resistances. Therefore, additional channels were inserted at the uncooled regions in the tree-shaped design (hybrid design). The best features of both parallel channels and tree-shaped designs are combined in the hybrid of them: the flow resistances to the fluid and heat flow become almost as low as the tree-shaped and parallel channels designs, respectively. The effect of design on the maximum temperature shows that there should be an optimum design for a distinct set of boundary conditions, and this design should be varied as the boundary conditions change. This result is in accord with the constructal law, i.e. the shape should be varied in order to minimize resistances to the flows.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Hydrothermal Synthesis and Characterization of One Dimensional Chain Structures of Monolacunary Keggin Polyoxoanions Substituted With Copper
    (Elsevier Ltd., 2015) Eanes, Mehtap; Önen, Banu; McMillen, Colin D.
    Two novel polymeric polyoxometallates constructed from transition metal substituted heteropolytungstates, [(4,4’bpyH2)2(4,4’bpyH)][PCuW11O39]·H2O (1), and [(4,4’bpyH2)(pyH)3][PCuW11O39]·2H2O (2), (4,4’bpy = 4,4’bipyridine, py = pyridine) have been synthesized under hydrothermal conditions and characterized by IR, TGA, single crystal X-ray diffraction and magnetic measurements. The product formation showed a high sensitivity toward experimental factors including pH and stirring. Compounds 1 crystallizes in the monoclinic space group P2(1)/n with a = 13.503(3) Å, b = 26.726(5) Å, c = 15.168(3) Å, = 99.61(3)° and Z=4. The second compound also crystallizes in space group P2(1)/n, but with a = 13.519(3) Å, b = 20.431(4) Å, c =18.655(4) Å, = 96.52(3)° and Z=4. Compound 1 exhibits a zigzag chain structure, while compound 2 exhibits a straight chain structure. Compound 2 is the first example of a polyoxometallate containing 1D chains of transitionmetal- substituted heteropolytungstate designed with two significantly different organic units as the countercations. The Cu2+ ions in 1 exhibit paramagnetic behavior.