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Flows, Gradients, and Transport Properties
Published in Joel L. Plawsky, Transport Phenomena Fundamentals, 2020
In this chapter, we introduced several flux-potential gradient laws and showed the relationships and analogies that exist between the various transport phenomena. We separated the fluxes into primary and secondary sources. The primary fluxes are most commonly encountered and their relationship between flux and potential gradient is the strongest. For example, Fourier's Law relates the flux of heat to a temperature gradient. This is the primary flux quantity, yet heat can be transferred via molecular diffusion as in the Dufour effect. The Dufour effect, a secondary transport mechanism, is characteristic of all secondary mechanisms. It is smaller than the primary mechanism and is only appreciable in certain circumstances (when the secondary gradient is extraordinarily high). Moreover, the secondary fluxes have a reciprocal relationship with another transport system. The Dufour effect, causing a heat flux due to a concentration gradient, has a sister mechanism in mass transport called the Soret effect. This effect forces a mass flux in response to a temperature gradient. Moreover, the transport properties associated with each effect are the same and the laws of irreversible thermodynamics assert that this must be the case. Such symmetry is fundamental to nature and natural transport processes.
Out-of-Equilibrium Thermodynamics
Published in Pier Luigi Gentili, Untangling Complex Systems, 2018
With thermal diffusion, we mean two phenomena. The first phenomenon is the relative motion of the components of a gaseous mixture or a liquid solution when there is a thermal gradient; it is named as Soret effect. The second phenomenon is a heat flow driven by concentration gradients, which is named as the Dufour effect. For both effects, the entropy production per unit volume can be written as [] p*=Ju∇(1T)−∑kJk∇(μkT)
External Condensation
Published in Van P. Carey, Liquid-Vapor Phase-Change Phenomena, 2020
In systems with a concentration gradient, an additional energy flux contribution occurs due to species diffusion. This additional energy transport effect is termed as the diffusion thermo effect or the Dufour effect. This effect is small in most systems of interest and we will therefore neglect it in the model analysis here.
An impact on non-Newtonian free convective MHD Casson fluid flow past a vertical porous plate in the existence of Soret, Dufour, and chemical reaction
Published in International Journal of Ambient Energy, 2022
M. Anil Kumar, Yanala Dharmendar Reddy, B. Shankar Goud, V. Srinivasa Rao
Figure 6 depicts the relationship between Dufour number Du and the temperature. The Dufour effect is known as a kind of heat flux that occurs because of a concentration gradient. In the occurrence of the Dufour effect, the temperature profiles are vaster than without the Dufour effect. When the Dufour number rises, so does the thermal boundary layer, and boundary layer flow is electrified with the mounting Dufour number. The temperature distribution for several plausible values of Prandtl number Pr = 0.63, 0.71,1.38, and 2.36 is shown in Figure 7. These values are noteworthy since they physically correlate to oxygen, air, ammonia, and carbon disulphide. When a consequence, as Pr rises, thermal conductivity decreases, and the thickness of the thermal boundary layer deteriorates. The temperature profiles in Figure 8 are influenced by the heat absorption coefficient . Physically, the existence of heat absorption (thermal sink) effects tends to cool the fluid. This results in a diminution in thermal buoyant effects, which results in a net drop in fluid temperature. Figure 9 portrays the temperature profile θ as a function of the radiation absorption parameter . When absorbed heat is radiated into the fluid that upsurges the fluid temperature near the porous boundary layer.
Darcy–Forchheimer flow of nanofluid invoking irreversibility
Published in Waves in Random and Complex Media, 2022
Muhammad Adil Sadiq, T. Hayat, Sohail Ahmad Khan
In the collaborated thermal and solutal transfer procedure, the flow is handled by density variance generated through gradient of temperature, material structure and gradient of concentration. Mass flux generated by a gradient of temperature is the well-known Soret effect. Heat flux created by gradient of concentration is called as the Dufour effect. The Soret effect is useful for isotope partition and in mixture among gases with very large and medium molecular weights. Diffusion-thermo and thermal-diffusion effects have tremendous useful applications in the field of geoscience, chemical and industrial engineering. Pal and Mondal [24,25] examined Dufour and Soret impacts for magnetohydrodynamic convective non-Darcian flow of thermal and solutal transport. Alao et al. [26] examined the Dufour and Soret impacts in chemically reactive time-dependent flow over a semi-infinite surface. Some advancements about this topic are seen in [27–31].
Study of radiative magneto-non-Newtonian fluid flow over a nonlinearly elongating sheet with Soret and Dufour effects
Published in Numerical Heat Transfer, Part A: Applications, 2023
Manasa Manjari Biswal, Kharabela Swain, Gouranga Charan Dash, Kanakalata Ojha
Soret effect is the mass flux generated by a temperature gradient and Dufour effect is the energy flux initiated by concentration differences. Both effects have applied in the field of geoscience and chemical engineering. The Soret effect has been employed for separation of isotopes while Dufour effect is more significant in mixtures between gases. Hayat et al. [20] and Reddy et al. [21] studied the Soret and Dufour effects on Casson fluid flow past an extending plate. Several researchers [21–25] have studied the influences of Soret and Dufour number by taking various flow models.