No abstract

Numerical analysis is performed to examine the heat transfer enhancement of Au, Al 2 O 3 , Cu and TiO 2 water-based nanofluids. The analysis uses a two-dimensional enclosure under natural convection heat transfer conditions and has been carried out for the Rayleigh number range 10 3 ≤ Ra ≤ 10 5 , and for the nanoparticles' volume fraction range 0 ≤ φ ≤ 0,10. The governing equations were solved with the standard finite-volume method and the hydrodynamic and thermal fields were coupled together using the Boussinesq approximation. Highly accurate numerical results are presented in the form of average Nusselt number and heat transfer enhancement. The results indicate clearly that the average Nusselt number is an increasing function of both, Rayleigh number and volume fraction of nanoparticles. The results also indicate that heat transfer enhancement is possible using nanofluids in comparison to conventional fluids, resulting in the compactness of many industrial devices. However, low Rayleigh numbers show more enhancement compared to high Rayleigh numbers.

No abstract

The present work deals with the laminar natural convection in a square cavity with differentially heated side walls subjected to constant temperatures and filled with homogenous 0,4 wt. % aqueous solution of carboxymethyl cellulose (CMC) based Au, Al 2 O 3 , Cu and TiO 2 nanofluids obeying the Power law rheological model. The governing differential equations have been solved by the standard finite volume method and the hydrodynamic and thermal fields are coupled together using the Boussinesq approximation.The main objective of this study is to investigate the influence of the nanoparticles' volume fraction (0 % ≤ φ ≤ 10 %) on the heat transfer characteristics of CMC based nanofluids over a wide range of nanofluid Rayleigh number (10 3 ≤ Ra nf ≤ 10 6 ). Accurate numerical results are presented in the form of dimensionless temperature and velocity variations, isotherms, mean Nusselt number and heat transfer enhancement. The results indicate clearly that the heat and momentum transfer characteristics are affected only by the nanofluid Rayleigh number, while the type of nanoparticles (i.e. thermo-phyisical properties) and their volume fraction have effect only on the heat transfer enhancement.

No abstract