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Reynolds analogy is popularly known to relate turbulent momentum and heat transfer.〔Geankoplis, C.J. ''Transport processes and separation process principles'' (2003), Fourth Edition, p. 475.〕 The main assumption is that heat flux q/A in a turbulent system is analogous to momentum flux τ, which suggests that the ratio τ/(q/A) must be constant for all radial positions. The complete Reynolds analogy * is: Experimental data for gas streams agree approximately with above equation if the Schmidt and Prandtl numbers are near 1.0 and only skin friction is present in flow past a flat plate or inside a pipe. When liquids are present and/or form drag is present, the analogy is conventionally known to be invalid.〔 In 2008, the qualitative form of validity of Reynolds' analogy was re-visited for laminar flow of incompressible fluid with variable dynamic viscosity (μ).〔Mahulikar, S.P., & Herwig, H., 'Fluid friction in incompressible laminar convection: Reynolds' analogy revisited for variable fluid properties,' ''European Physical Journal B: Condensed Matter & Complex Systems'', 62(1), (2008), pp. 77-86.〕 It was shown that the inverse dependence of Reynolds number (''Re'') and skin friction coefficient(''c''f) is the basis for validity of the Reynolds’ analogy, in laminar convective flows with constant & variable μ. For μ = const. it reduces to the popular form of Stanton number (''St'') increasing with increasing ''Re'', whereas for variable μ it reduces to ''St'' increasing with decreasing ''Re''. Consequently, the Chilton-Colburn analogy of ''St''•''Pr''2/3 increasing with increasing ''c''f is qualitatively valid whenever the Reynolds’ analogy is valid. Further, the validity of the Reynolds’ analogy is linked to the applicability of Prigogine's Theorem of Minimum Entropy Production.〔Prigogine, I. ''Introduction to Thermodynamics of Irreversible Processes'' (1961), Interscience Publishers, New York.〕 Thus, Reynolds' analogy is valid for flows that are close to developed, for whom, changes in the gradients of field variables (velocity & temperature) along the flow are small.〔 ==See also== * Reynolds number * Chilton and Colburn J-factor analogy 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Reynolds analogy」の詳細全文を読む スポンサード リンク
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