Numerical investigation of nanofluids forced convection in circular tubes

Abstract

In this paper, developing laminar forced convection flow of a water-Al 2 O 3 nanofluid in a circular tube, submitted to a constant and uniform heat flux at the wall, is numerically investigated.A single and two-phase model (discrete particles model) is employed with either constant or temperaturedependent properties. The investigation is accomplished for size particles equal to 100 nm. The maximum difference in the average heat transfer coefficient between single and two phase models results is about 11%.Convective heat transfer coefficient for nanofluids is greater than that of the base liquid. Heat transfer enhancement increases with the particle volume concentration, but it is accompanied by increasing wall shear stress values. Higher heat transfer coefficients and lower shear stresses are detected in the case of temperature dependents models. The heat transfer always improves, as Reynolds number increases, but it is accompanied by an increase of shear stress too.Moreover a comparison with data present in the literature is carried out.

Numerical Study of the Enhancement of Heat Transfer for Hybrid CuO-Cu Nanofluids Flowing in a Circular Pipe

“…This is due to the increase of the Prandtl number of the nanofluid and also to an increase in volume fraction. Here, the results are similar to that observed by Bianco et al 19 and He et al 21 . The figures show the increase of the Cu content in the nanofluid instead of the CuO tends to increase the heat transfer coefficients for the same volume fraction nanofluid.…”

“…The results obtained for each particular test case showed that for the tube flow problem under consideration, the 757,817 elements appeared to be satisfactory to ensure the precision of the numerical results as well as their independency with respect to the number of nodes used. The computer model was successfully validated with correlations reported by Shah 2006 19 for thermally and hydraulically developing flow, which showed an average error of less than 2 , as reported in Fig. 2 and Fig.…”

“…fully-developed laminar flow for water was compared with the empirical correlation given by Shah Equation 19 . Figure 5 shows the comparison of the Nusselt number for water calculated using equation 13 with the Nu determinate by Shah Equation 16.…”

CFD assessment of the effect of nanoparticles on the heat transfer properties of acetone/ZnBr2 solution

“…Figure 5b shows Nu as a function of flow rate at the nanoparticle volume fraction of 1 % in both experimental (previous work) and CFD (current work), with maximum difference between the experiment and numerical results of 9 %. The difference could be caused by some factors such as particle size, which effect on the viscosity, temperature dependant properties and the Brownian motion of the particles which effect on the thermal conductivity [38][39][40]. Comparison between the experimental Nu from [28] and the predicted Nu from [37].…”

Further Investigation on Laminar Forced Convection of Nanofluid Flows in a Uniformly Heated Pipe Using Direct Numerical Simulations

“…For example, Mehrez et al [15] numerically investigated the entropy generation and the mixed convection heat transfer of copper/water-based nanofluids in an inclined open cavity with uniform heat flux at the wall. During the last decade, many other authors compared the performance of the different single and two-phase models with constant or temperature-dependent properties in the context of nanofluid flows [16][17][18][19][20][21]. A detailed state-of-the-art review has been besides recently proposed by Kakaç and Pramuanjaroenkij [10].…”