Effects of Rib Shapes on the Entropy Generation in a Ribbed Duct

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Effects of Rib Shapes on the Entropy Generation in a Ribbed Duct

Javadi, P. / Rashidi, S. / Esfahani, J. A.

Ducts are often used in reactors and heat exchangers. Using rough surfaces in ducts is recognized as an effective technique to enhance heat transfer. In this research, an entropy generation analysis is carried out for turbulent flow inside a ribbed duct. Numerical simulations are performed to study the effects of rib shapes and flow Reynolds numbers on friction factor, Nusselt number, and different types of entropy generation containing the frictional and thermal ones. All simulations are performed for Reynolds number in the range of 20,000 to 60,000 and six rib shapes (rectangular, square, isosceles trapezoidal, rectangular trapezoidal, equilateral triangle, and nonequilateral triangle). A shear stress transport k-omega turbulence model is used for the numerical simulations. It was found that the ribs with no inclined surfaces such as square and rectangular shapes create more thermal irreversibility. Moreover, it was shown that among different rib shapes, the equilateral triangle rib has the highest frictional entropy generation over the entire range of the Reynolds number, whereas the rectangular rib has the lowest one.