Magnetic Nanofluids for Heat Transfer Enhancement Inside Straight Channels

A numerical study for investigating the fluid flow and heat transfer enhancement inside square, circular and triangular straight channels with hydraulic diameter of 0.01 m using magnetic nanofluid (Fe3O4 suspended in water) as a base fluid under constant heat flux subjected around the geometries walls has been presented to determine the effects of nanoparticle volume fraction and flow rate on the convective heat transfer and friction factor of nanofluid without the influence of magnetic field. The nanofluid consists of Fe3O4 magnetic nanoparticles with average diameter of 36 nm suspended in water with a different volume fraction which were 0.2, 0.4, and 0.6%. The study was conducted at steady state, turbulent forced convection with Reynolds number (5000 ≤ Re ≤ 20000), three-dimensional flow, and single-phase approach. Certain boundary conditions and assumptions to solve the governing equations have been implemented using finite volume method. CFD software involving GAMBIT and FLUENT were employed to perform the investigation numerically. The results revealed that as Reynolds number increased, the heat transfer rate was also increased for all the geometries but it is better in circular tube case. While in the case of using pure water as a coolant, the heat transfer rate is lower than that the case of using nanofluid with respect to the flow inside all the geometries. In addition, as Reynolds number increase, friction factor decreases for all cases and it is large in case of square duct. New correlations were proposed to predict Nusselt number and friction factor based on the dimension less numbers which are valid for the three geometries. a of a length of the of the with The nanofluid nanoparticles in with nanoparticle volume concentrations from 0 to 0.6% and range of number from to 22000. to estimate Nusselt number and friction factor. The raveled that the heat transfer is enhanced by 30.93%.