Session: 12-08-02: Computational Heat Transfer and Applications II

Paper Number: 166180

Heat Transfer and Flow Analysis of Glycolated Water-CNT Nanofluid in a Hexalobular Tube Having Internal Coil of Elliptical Cross-Section As a Vortex Generator 

In this investigation, heat transfer rate and fluid flow behaviour were assessed having water and different Carbon Nanotubes (CNT) nanofluids as the thermal transport medium inside the hexalobular tube with the presence of an inner coil of elliptical shaped cross-section. The current study was carried out to evaluate the effects of the geometry of the flow paths, presence of internal bodies and nanofluids in glycolated water. To do so, three types of cross-sections, circular, hexagonal and hexalobular, three arrangements of inner coil, straight, converging and diverging, and three concentrations of nanofluid, 1%, 2% and 3% were considered. Navier stokes equations with k-ε turbulence model including enhanced wall treatment and energy equations were solved to determine behaviour of heat transport, local temperature distribution, eddy formation and pressure loss for these cases. It was found that more eddies were formed inside the lobes of the hexalobular section, while comparatively lower swirling occurred in hexagonal and circular tubes. Significant increase of eddy formation obtained with inclusion of inner coil, where straight coil caused uniform distribution of eddies over the length of the tubes along the coil surface. The rise of the turbulence resulted in the desired changes in the temperature distribution as well as the heat transfer characteristics. For quantitative analysis, four output parameters were determined as evaluation criteria of this thermo-fluid system, such as Nusselt number for heat transfer rate, pressure loss for required pumping power, friction factor for flow resistance, and thermal efficiency for overall performance considering both heat transfer and friction loss. The assessment of these performance evaluation parameters was performed within the range of Reynolds number 10000Re30000. From this investigation, it was observed that hexalobular cross-sectional shape had a significant effect on heat transfer performance and thermal efficiency compared to the circular shape, specially at higher Reynolds number, more than 8% improvement was obtained. Inclusion of coil inside the tube facilitated the heat transport with around 30% enhancement by introducing more swirling while acting as a vortex generator. Notably, the straight coil performed remarkably better than that of converging coil and diverging coil. Moreover, instead of using just water as working medium, presence of Carbon nanotube nanoparticles inside the glycolated water augmented the heat transfer significantly. The increase in the concentration of the nanoparticles improved the thermal transport further, however optimization of the overall performance limited the use of high concentration due to the rise in the frictional loss.

Presenting Author: M. Ruhul Amin Montana State Univ

Presenting Author Biography: M. Ruhul Amin has received the Ph.D. degree in mechanical engineering from the University of Tennessee, USA. He is a professor of mechanical engineering at Montana State University, USA with extensive background in computational heat transfer and fluid flow. He is the program coordinator of mechanical engineering program at Montana State University and an ABET Program Evaluator. Dr. Amin is a Fulbright Scholar, a member of ASME, and member of ASME technical committees. He is a registered professional engineer in the State of Montana. He has chaired and co-chaired numerous technical sessions at international technical conferences. He also co-chaired several international conferences on thermal sciences.

Authors:

Md Maruf Tahmid Bangladesh University of Engineering & Technology
Tawsif Iqbal Bangladesh University of Engineering & Technology
Kamol Banik Bangladesh University of Engineering & Technology
Mohammad Ali Bangladesh University of Engineering & Technology
M. Ruhul Amin Montana State Univ