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Heat transfer and binary diffusion with thermodynamic coupling in variable‐property forced convection on a flat plate
Author(s) -
Zeh Dale W.,
Gill William N.
Publication year - 1967
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690130126
Subject(s) - thermodynamics , laminar flow , adiabatic process , heat transfer , mechanics , diffusion , mass transfer , coupling (piping) , chemistry , dissipation , materials science , physics , metallurgy
The variable‐property, laminar, boundary‐layer equations, which describe simultaneous momentum, heat, and binary mass transfer with thermodynamic coupling, Thermodynamic coupling refers to the Soret (or thermaldiffusion)effect, which is the flow of mass caused hy a temperaturegradient, and the Dufour (or diffusion thermo) effect, which is theflow of heat caused by a concentration gradient. are analyzed for air flows over a flat plate with the injection of foreign gases through the solid surface. A simplified general treatment of thermodynamic coupling is developed and applied to yield approximate but accurate expressions for evaluating heat transfer rates and adiabatic wall temperatures for injection of hydrogen, helium, and carbon dioxide. This method explains why the driving force based on (T ω − T ω ) can be used to correlate heat transfer results for situations where diffusion thermo is important. Furthermore, and perhaps most significant, the method provides a simple error estimate for the correlation obtained by using the adiabatic wall temperature. It is shown that the injection of lightweight gases can significantly reduce viscous dissipation in flows over slender bodies and that diffusion thermo and dissipation effects can be otion in flows over slender bodies and that diffusion thermo and dissipation effects can be of the same order of magnitude even for reasonably high‐velocity flows. These effects are discussed in terms of convenient quantities, called σ functions.