Analysis of entropy generation due to natural convection in rhombic enclosures / R. Anandalakshmi in Industrial & engineering chemistry research, Vol. 50 N° 23 (Décembre 2011)  

Analysis of entropy generation due to natural convection in rhombic enclosures [texte imprimé] / R. Anandalakshmi, Auteur ; Tanmay Basak, Auteur . - 2012 . - pp. 13169–13189.
Chimie industrielle
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 13169–13189

Mots-clés :	Entropy generation
Résumé :	One way of increasing the energy efficiency in thermal processing of materials is to reduce exergy losses due to irreversibilities, measured as “entropy generation”. In this study, an analysis of entropy generation during natural convection in rhombic enclosures with various inclination angles (φ = 30°, 45°, and 75°) has been carried out for the efficient thermal processing of various fluids (Prandtl numbers of Pr = 0.015, 0.7, 7.2, and 1000) in a range of Rayleigh numbers (Ra = 103–105). The enclosure is bounded by an adiabatic top wall, cold side walls, and an isothermally (case 1) and nonisothermally (case 2) heated bottom wall. Isotherms (θ), streamlines (ψ), and entropy generation contours due to heat transfer (Sθ) and fluid friction irreversibility (Sψ) are analyzed for both cases. At low Rayleigh number (Ra = 103), the entropy generation in the cavity is dominated by Sθ for all φ, irrespective of Pr. As Ra increases to 105, the fluid flow intensifies and Sψ also increases for all φ, irrespective of Pr. The total entropy generation (Stotal), average Bejan number (Beav), and average heat-transfer rate (Nub) are plotted for Rayleigh number ranges of 103 ≤ Ra ≤ 105. The total entropy generation (Stotal) is found to be low for φ = 30° and high for φ = 75° for all Pr values at Ra = 105. Analysis of variations of Beav with Ra for high-Pr fluids indicates that Sψ contributes significantly for increase in Stotal. It is also found that the largest heat-transfer rate (Nub) corresponds to minimum entropy generation (Stotal) for φ = 30° cavities at Ra = 105 with all Pr in case 1. The nonisothermal heating strategy (case 2) is energy efficient, because of its lower Stotal value, corresponding to low Nub, which is due to a lesser heating effect than case 1 for all φ. Overall, rhombic cavities with φ = 30° may be the optimal geometrical design for thermal processing of all types of fluids (Pr = 0.015, 0.7, 7.2, and 1000), irrespective of the heating strategy.
DEWEY :	660
ISSN :	0888-5885
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie200184y