Optimal selection of annulus radius ratio to enhance heat transfer with minimum entropy generation in developing laminar forced convection of water-Al2O3 nanofluid flow

• Published in: Journal of Central South University Vol. 24; no. 8; pp. 1850 - 1865
• Main Authors: Majid, Siavashi, Mohammad, Jamali
• Format: Journal Article
• Language: English
• Published: Changsha Central South University 01.08.2017; Springer Nature B.V
• Subjects: Aluminum oxide; Annuli; Computational fluid dynamics; Engineering; Entropy; Fluid flow; Forced convection; Heat flux; Heat transfer; Laminar flow; Laminar heat transfer; Metallic Materials; Nanofluids; Nanoparticles; Optimization; Reynolds number; annulus; entropy generation; nanofluid; heat transfer enhancement; forced convection; radius ratio
• ISSN: 2095-2899; 2227-5223
• DOI: 10.1007/s11771-017-3593-7

Heat transfer and entropy generation of developing laminar forced convection flow of water-Al 2 O 3 nanofluid in a concentric annulus with constant heat flux on the walls is investigated numerically. In order to determine entropy generation of fully developed flow, two approaches are employed and it is shown that only one of these methods can provide appropriate results for flow inside annuli. The effects of concentration of nanoparticles, Reynolds number and thermal boundaries on heat transfer enhancement and entropy generation of developing laminar flow inside annuli with different radius ratios and same cross sectional areas are studied. The results show that radius ratio is a very important decision parameter of an annular heat exchanger such that in each Re , there is an optimum radius ratio to maximize Nu and minimize entropy generation. Moreover, the effect of nanoparticles concentration on heat transfer enhancement and minimizing entropy generation is stronger at higher Reynolds.