Numerical Study on Buoyancy Driven Heat Transfer Utilizing Nanofluids in a Rectangular Enclosure Ahmad Faris Ismail Department of Mechanical Engineering, International Islamic University Malaysia P.O Box 10 50728 Kuala Lumpur Malaysia Email: (faris@iiu.edu.my) Rashmi Welvakar Department of Biotechnology Engineering, International Islamic University Malaysia P.O Box 10 50728 Kuala Lumpur Malaysia Email: (rash_chem@engineer.com) Mohammad Khalid Department of Biotechnology Engineering, International Islamic University Malaysia P.O Box 10 50728 Kuala Lumpur Malaysia Email: (khalids@engineer.com) ABSTRACT A numerical study on heat transfer enhancement utilizing nanofluids in a two-dimensional enclosure was investigated for various pertinent parameters using commercial CFD code FLUENT 6.3. Numerical simulations were carried out assuming nanofluid as single phase. Effect of Rayleigh number ranging from 6 3 10 10 ≤ ≤ Ra and nanoparticle volume fraction (0- 20%) was studied on flow pattern and energy transport within the thermal boundary layer for aspect ratio of 1.0. Stream function and isotherm contours were plotted for all the above mentioned parameters. Results show that effect of buoyancy parameter and volume fraction causes increase in average heat transfer enhancement. The results were also compared with the khanafer’s model and found to be in good agreement. Keywords: Nanofluids, Heat transfer, Buoyancy parameter. 1. Introduction Thermal conductivity is an important parameter in enhancing the heat transfer performance of a heat transfer fluid. Since the thermal conductivity of solid metals is higher than that of fluids, the suspended particles are expected to be able to increase the thermal conductivity and heat transfer performance. Low thermal conductivity of process fluid hinders high compactness and effectiveness of heat exchangers, although a variety of techniques is applied to enhance heat transfer. Improvement of the thermal properties of energy transmission fluids may become a trick of augmenting heat transfer. J.C Maxwell [1] was the first to propose the fundamental idea of adding nanoparticles to the base fluid to enhance the effective thermal conductivity of the base fluid. The effect of particle inclusions on the effective thermal conductivity of liquid has attracted more and more interest experimentally and theoretically since 1873. By suspending nanophase particles in heating or cooling fluids, the heat transfer performance of the fluid can be significantly improved. The main reasons may be listed as follows [2]: