HEAT TRANSFER ENHANCEMENT FOR NATURAL CONVECTION FLOW OF WATER-BASED NANOFLUIDS IN A SQUARE ENCLOSURE

Numerical analysis is performed to examine the heat transfer enhancement of Au, Al2O3, Cu and TiO2 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 103 <= Ra <= 105, and for the nanoparticles' volume fraction range 0 <= phi <= 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. (Received in May 2011, accepted in October 2011. This paper was with the authors 2 months for 1 revision.)