World Applied Sciences Journal 22 (5): 601-607, 2013 ISSN 1818-4952 © IDOSI Publications, 2013 DOI: 10.5829/idosi.wasj.2013.22.05.1172 Corresponding Author: S.I. Vasefi, Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran. 601 Experimental and Numerical Investigation of Al O -Water Nanofluid Inside a Triangular Tube 2 3 K. Zabihi, F. Gholamian and S.I. Vasefi Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran Abstract: An experimental and numerical study has been performed to investigate the effect of nanofluids on convective heat transfer through a triangular straight tube with a constant heat flux boundary condition in the laminar flow regime. The convective heat transfer coefficient of nanofluids has been obtained for different nanoparticle concentrations and Re number. Experimental results show heat transfer coefficient increases by increasing the concentration of nanoparticles in nanofluid. The increase in heat transfer coefficient due to presence of nanoparticles is much higher than the prediction of single phase heat transfer correlation used with nanofluid properties. The axial development of temperature and convective heat transfer coefficient at the outer wall is obtained numerically. The results show a good agreement between numerical and experimental data. The velocity profiles are presented in transverse plane at the fully developed region. The effect of nanoparticles concentration on temperature, velocity and convective heat transfer coefficient is shown and discussed. Key words: Convective heat transfer Triangular tube Nano-fluid Heat transfer coefficient INTRODUCTION enhancement, the effect of the presence of nanoparticles In many industries, enhancement of heat transfer coefficients and the mechanisms of heat transfer characteristics of the thermal systems, such as energy enhancement under various conditions. Different and transportation is at the center of attention. The parameters such as particle type, volume fraction and conventional methods to improve the heat transfer rate particle diameter can affect the amount of enhancement in such as using fins or vibration of heated surfaces is not convective heat transfer. Wen and Ding [5] investigated applicable or show restricted application in many heat convective heat transfer of Al O -water nanofluid in a transfer instruments [1]. After proposing nanofluids by straight tube. Their results showed considerable Choi [2] as new engineering materials, many researchers enhancement of convective heat transfer using the investigated the characteristics of nanofluids. Several nanofluids. The enhancement was particularly significant authors investigated different nanoparticle volume in the entrance region and was much higher than that just fractions and materials in several base fluids and all due to the enhancement on thermal conduction. Heris et findings show higher thermal conductivity of nanofluids al. [6] have experimentally investigated laminar flow compared to base fluids. Xuan et al. [3] obtained thermal forced convection heat transfer of Al O -water nanofluid conductivity of Cu-water nanofluid of 100 nm diameter in a circular tube with constant wall temperature. They copper particles experimentally. They have observed that have found that increasing Peclet number and this nanofluid with 5% volume fraction remains stable for nanoparticle concentration lead to an increase in heat more than 30 hours. Murshed et al. [4] investigated transfer. They have conveyed that presence of thermal conductivity and viscosity of nanofluids. nanoparticles increases heat transfer coefficient and this They showed that both the thermal conductivity and enhancement in heat transfer coefficient cannot be viscosity of nanofluids increase with the nanoparticle predicted by correlations of single phase method. volume fraction. The thermal conductivity of nanofluids Different numerical research has been performed to was also observed to be strongly dependent on predict heat transfer characteristics of nanofluids and temperature. However, disagreements exist in the literature identify the mechanisms that increase heat transfer of in terms of the extent of the thermal conduction nanofluids. Keblinski et al. [7] have studied different on forced and natural convection heat transfer 2 3 2 3