Developing laminar mixed convection of nanofluids in an inclined tube with uniform wall heat flux

Abstract

Purpose -The aim is to study the conjugate problem of developing laminar mixed convection flow and heat transfer of water-Al 2 O 3 nanofluid inside an inclined tube submitted to a uniform wall heat flux. Design/methodology/approach -The set of non-linear, coupled and fully elliptic governing equations has been solved using a ''finite-control-volume'' numerical method, the classical power-law scheme for computing heat and momentum fluxes staggered and non uniform grids for spatial discretization of various regions of the tube. Findings -Numerical results have shown that the presence of nanoparticles slightly intensifies the secondary flow due to buoyancy, in particular in the developing region. It also increases the average Nusselt number and decreases slightly the product ReC f with respect to those of water. For the horizontal inclination, two new correlations have been proposed to calculate these two variables in the fully developed region, for Grashof number ranging from 10 3 to 10 5 and particle volume concentrations up to 7 per cent. Practical implications -The results of this study can be employed for various practical heat transfer and thermal applications using nanofluids. Originality/value -The present study constitutes an original contribution to the knowledge of nanofluid thermal behaviour.

An empirical study on fluid properties and pressure drop of nanofluid flow inside inclined smooth and microfin tubes

“…In addition, at lower velocities, the effect of natural convection is increased and as a result less pressure drop is obtained. For the tested Ri ranging from 0.1 to 12 which assures having a mixed convection regime, similar trends were achieved by other scientists [6,12].…”

“…Knowledge of the heat transfer characteristics under both conditions is necessary for the design of a heat exchanger. Ben Mansour et al [6,7] studied the conjugate problem of laminar mixed convection flow of Al 2 O 3 /water nanofluid in a uniformly heated inclined tube, both experimentally and numerically. They found that the presence of nanoparticles intensifies the buoyancy-induced secondary flow, especially in the developing region.…”

Comparative assessment of single and two-phase models for numerical studies of nanofluid turbulent forced convection

“…Most such studies have treated nanofluids as single-phase fluids with effective thermophysical properties which are obtained from a combination of the corresponding properties of the liquid carrier and the solid particles (Abu-Nada et al, 2008;Akbarinia and Behzadmehr, 2007;Ben Mansour et al, 2009;Maiga et al, 2006).…”

Two-phase modelling of nanofluid heat transfer in a microchannel heat sink

“…In fact, the capability of nanofluids for the heat transfer enhancement purpose has clearly been established for internal flow configurations -see in particular Pak and Cho [1], Li and Xuan [2], Wen and Ding [3], Yang et al [4], Maïga et al [5,6]. A similar heat transfer enhancement was also observed experimentally for a closed-liquid system destined for cooling of high-powered electronic components, Roy et al [7] and Nguyen et al [8], as well as in cases of free convection (Polidori et al [9]) and laminar mixed convection flow (Ben Mansour et al [10][11][12] and Popa et al [13]). …”