Application of Cylindrical Fin to Improve Heat Transfer Rate in Micro Heat Exchangers Containing Nanofluid under Magnetic Field

• Main Authors: Yacine Khetib, Ahmad Alahmadi, Ali Alzaed, Suseel Jai Krishnan, Mohsen Sharifpur, Goshtasp Cheraghian
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Processes
• Subjects: non-Newtonian fluid; nanofluid; two-phase flow; corrugated channel; magnetic field; augmented heat transfer
• Online Access: https://www.mdpi.com/2227-9717/9/8/1278

In this study, the convective mode heat transfer phenomena of bi-phase elasticoviscous (non-Newtonian) nanofluid is quantified by forcefully flowing it through a specially designed microchannel test section. The test section, which is rectangularly cross-sectioned and annexed internally with cylindrical needle ribs is numerically investigated by considering the walls to be maintained at a constant temperature, and to be susceptible to a magnetizing force field. The governing system-state equations are numerically deciphered using control volume procedure and SIMPLEC algorithm. With the Reynolds number (Re) varying in the turbulent range from 3000 to 11,000, the system-state equations are solved using the Eulerian–Eulerian monofluid Two-Phase Model (TPM). For the purpose of achieving an apt geometry based on the best thermo-hydraulic behavior, an optimization study must be mandatory. The geometry of the cylindrical rib consists of h (10 × 10⁻³, 15 × 10⁻³, 20 × 10⁻³), <i>p</i> (1.0, 1.5), and d (8 × 10⁻³, 10 × 10⁻³, 12 × 10⁻³), which, respectively, defines the height, pitch, and diameter of the obstacles, with the dimensions placed within the braces being quantified in mm. The results demonstrated that the magnetic field leads to an enhanced amount of average Nusselt number (Nu_av) in contrast with the occurrence at B = 0.0. This is due to the that the magnetic field pushes nanoparticles towards the bottom wall. It was found that B = 0.5 T has the maximum heat transfer compared with the other magnetic fields. The channel with h = 15 μm height leads to the maximum value of Nu_av at all studied <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mi>e</mi></mrow></semantics></math></inline-formula> for constant values of d and h. The channel with <i>p</i> = 1.5 μm results in the maximum value of Nu_av at all studied <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mi>e</mi></mrow></semantics></math></inline-formula> for constant values of d and h. The microchannel with d = 8 μm, <i>p</i> = 1.5 μm, and h = 15 μm in the presence of the magnetic field with B = 0.5 T is the best geometry in the present work.