Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Numerical and Experimental Investigation of Radial and Tree-Shaped Vascular Channels for Self-Cooling Structures(Izmir Institute of Technology, 2016) Yenigün, Onur; Çetkin, ErdalIn this study, 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: radial, 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 radial 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. Therefore, additional channels were inserted at the uncooled regions (hybrid design). The best features of both radial 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 radials designs, respectively. Furthermore, this thesis shows how delaying the inlet of the coolant fluid for a given time interval affects the peak temperature. 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.Master Thesis Numerical Determination of Permeability and Interfacial Convective Heat Transfer Coefficient for Non-Isotropic and Periodic Dual Scale Porous Medium(Izmir Institute of Technology, 2015) Sabet, Safa; Barışık, Murat; Mobedi, MoghtadaIn this study, the fluid flow and heat transfer in a periodic, non-isotropic dual scale porous media consisting of permeable square rods in inline arrangement is analyzed to determine permeability and interfacial convective heat transfer coefficient, numerically. A periodical representative elementary volume (REV) with the dimensions of H×H is chosen as the computational domain. The flow in the REV is assumed fully developed and periodical. The permeable square particles are placed with in-line arrangement. There are two symmetrical intraparticle pores considered here which are in longitudinal flow direction. The continuity, Navier-Stokes and energy equations are solved to obtain the velocity, pressure and temperature distributions in the unit structures of the dual scale porous media. The obtained fields are upscaled by using volume average method to obtain the intrinsic inter and intraparticle permeabilities, bulk permeability tensor, interfacial convective heat transfer coefficients and the corresponding Nusselt numbers of the dual scale porous media for different values of inter and intraparticle porosities. The study is performed for interparticle porosities between 0.4 and 0.75 and for intraparticle porosities range of 0.2 to 0.8. A correlation based on Kozeny-Carman theory in terms of interparticle and intraparticle porosities and permeabilities is proposed to determine the bulk permeability tensor of the dual scale porous media. The intraparticle porosity value increase the flow rate passes through the porous media and the particle becomes more permeable. However; for high interparticle porosity values, the intraparticle porosity does not have importance effect on bulk permeability. Additionally, the results predicts that the interfacial convective heat transfer coefficient increases with increase of Reynolds number and the ratio of intra to interparticle porosity, while the increase rate shows variation with the porosity ratio and Reynolds number values.