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Research Papers: Porous Media

Kazi S. N., Duffy G. G., Chen X. D. The Effect of Varying Fiber Characteristics on the Simultaneous Measurement of Heat and Momentum Transfer to Flowing Fiber Suspensions J. Heat Transfer 137, 012601 (2014) (9 pages);   Paper No: HT-13-1619;   doi:10.1115/1.4028706

Heat transfer and pressure loss measurements were obtained simultaneously for a range of wood pulp fiber suspensions flowing in a pipeline. Data were obtained over a selected range of flow rates and temperatures from a specially built flow loop. It was found that the magnitude of the heat transfer coefficient was above water at equivalent experimental conditions and at very low fiber concentrations, but progressively decreased until it was below water at slightly higher concentrations. Similar trends were obtained for the pressure drop measurements obtained simultaneously, showing good correspondence between the two sets of data. It was found that both heat and momentum transfer are affected in a closely similar way by varying fiber properties, such as fiber length, fiber flexibility, fiber chemical and mechanical treatment, the variation of fibers from different parts of the tree, as well as the different pulping methods used to liberate the fibers from the wood structure. Drag reduction increased and heat transfer coefficient decreased with increasing fiber flexibility as found by previous workers.

Ozgumus Turkuler, Mobedi Moghtada. Effect of Pore to Throat Size Ratio on Interfacial Heat Transfer Coefficient of Porous Media J. Heat Transfer 137, 012602 (2014) (9 pages);   Paper No: HT-14-1341;   doi:10.1115/1.4028764

In this study, the effects of pore to throat size ratio on the interfacial heat transfer coefficient for a periodic porous media containing inline array of rectangular rods are investigated, numerically. The continuity, Navier–Stokes, and energy equations are solved for the representative elementary volume (REV) of the porous media to obtain the microscopic velocity and temperature distributions in the voids between the rods. Based on the obtained microscopic temperature distributions, the interfacial convective heat transfer coefficients and the corresponding Nusselt numbers are computed. The study is performed for pore to throat size ratios between 1.63 and 7.46, porosities from 0.7 to 0.9, and Reynolds numbers between 1 and 100. It is found that in addition to porosity and Reynolds number, the parameter of pore to throat size ratio plays an important role on the heat transfer in porous media. For the low values of pore to throat size ratios (i.e., β = 1.63), Nusselt number increases with porosity while for the high values of pore to throat size ratios (i.e., β = 7.46), the opposite behavior is observed. Based on the obtained numerical results, a correlation for the determination of Nusselt number in terms of porosity, pore to throat size ratio, Reynolds and Prandtl numbers is proposed.

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