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Two Phase Flow Phase Change and Numerical Modeling Part 5

Tham khảo tài liệu 'two phase flow phase change and numerical modeling part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 110 Two Phase Flow Phase Change and Numerical Modeling Fig. 14. Evolution of the curvature radius along a microchannel In the evaporator and adiabatic zones the curvature radius in the parallel direction of the microchannel axis is lower than the one perpendicular to tills axis. Therefore the meniscus is described by only one curvature radius. In a given section rc is supposed constant. The axial evolution of rc is obtained by the differential of the Laplace-Young equation. The part of wall that is not in contact with the liquid is supposed dry and adiabatic. In the condenser the liquid flows toward the microchannel corners. There is a transverse pressure gradient and a transverse curvature radius variation of the meniscus. The distribution of the liquid along a microchannel is presented in Fig. 14. The microchannel is divided into several elementary volumes of length dz for which we consider the Laplace-Young equation and the conservation equations written for the liquid and vapor phases as it follows Laplace-Young equation dPv dPj _ drc dz dz rc2 dz Liquid and vapor mass conservation 9 10 11 d 1 W Aj 1 dQ dz hv dz d v wv Av 1 dQ dz h dz Liquid and vapor momentum conservation td X dz d Pi dz Afl U Alw lw J g AjSin dz 12 111 Theoretical and Experimental Analysis of Flows and Heat Transfer within Flat Mini Heat Pipe Including Grooved Capillary Structures d Avwị az dz d A Fv dz I il Ail I vw Aw dz g Av sin dz 13 Energy conservation _2k _b_ T Tt 1 2 . V w sat 14 The quantity dQ dz in equations 10 11 and 14 represents the heat flux rate variations along the elementary volume in the evaporator and condenser zones which affect the variations of the liquid and vapor mass flow rates as it is indicated by equations 10 and 11 . So if the axial heat flux rate distribution along the microchannel is given by Qa z Le Le La zi Lc-Lb J 0 z Le Le z Le La Le La z Lt Lb 15 we get a linear flow mass rate variations along the microchannel. In equation 15 h represents the heat transfer