Numerical study of two phase laminar mixed convection nanofluid in elliptic ducts

Abstract

Laminar mixed convection Al 2 O 3-Water nanofluid flow in elliptic ducts with constant heat flux boundary condition has been simulated employing two phase mixture model. Threedimensional Navier-Stokes, energy and volume fraction equations have been discretized using the finite volume method. The Brownian motions of nanoparticles have been considered to determine the thermal conductivity and dynamic viscosity of Al 2 O 3-Water nanofluid, which depend on temperature. Simulation effects of solid volume fraction, aspect ratio and buoyancy forced on thermal and hydraulics behaviors of nanofluid flow in elliptic ducts have been presented and discussed. The calculated results show good agreement with the previous numerical data. Results show that in a given Reynolds number (Re) and Richardson number (Ri), increasing solid nanoparticles volume fraction increases the Nusselt number (Nu) while the skin friction factor decreases. Increasing aspect ratio (AR=b/a) in elliptic tubes reduces the local skin friction factor whereas it does not have any specified effect on the local Nusselt number.

Numerical Investigation on the Turbulent Flow Characteristic of Nanofluids in a Horizontal Circular Tube

“…However, in the liquid-solid two-phase flow, the viscosity and density of the nanoparticle should be at least of the same order of magnitude as those of liquid phase, or even higher, which is confirmed in the following section. Equation (16) cannot be simplified as Miller did, which directly indicates that the traditional empirical correlation based on gas-solid circulating fluidized bed is not appropriate for the viscosity calculation of nanoparticles.…”

“…There are commonly four popular approaches for numerically studying nanofluids: the single-phase model [6,7], the mixture multiphase model [8][9][10][11][12][13][14][15][16][17][18][19][20][21], the EulerianEulerian multiphase model [22][23][24][25][26][27] and the Euler-Lagrange multiphase model [28][29][30][31]. Although a variety of modified models that describe the heat transfer process in nanofluids is continually presented, thus far all modeling results are not very satisfactory: they all underestimate heat transfer coefficients when compared with experiment.…”

Thermally Developing Flow and Heat Transfer in Elliptical Minichannels with Constant Wall Temperature

“…They further investigated the laminar flow in a curved duct of elliptical cross-section with fins and found the heat transfer rate is the maximum with the same aspect ratio [25]. However, Shariat et al [26] numerically calculated the Nusselt number of laminar mixed convection in elliptic channels with a constant heat flux boundary condition, and found that the best heat transfer performance appears when the aspect ratio is 0.75. The difference may be ascribed to the different thermal boundary conditions and the nanofluid chosen as the working fluid.…”

Heat transfer enhancement with elliptical tube under turbulent flow TiO2-water nanofluid

“…Turbulent forced convection heat transfer of water and nanofluid inside tube under single phase approach was carried out by [2][3][4][5][6]. Pak and Cho [7] were investigated the effect of two different metallic oxide particles, TiO 2 , and Al 2 O 3 , with mean diameters of 27 nm and 13inm, respectively, on base fluid (water) experimentally.…”