NUMERICAL ANALYSIS OF HEAT TRANSFER ENHANCEMENT WITH THE USE OF γ-AL_2_3/WATER NANOFLUID AND LONGITUDINAL RIBS IN A CURVED DUCT

摘要

This paper presents a numerical investigation of heat transfer augmentation using internal longitudinal ribs and γ-AL_2_3/water nanofluid in a stationary curved square duct. The flow is assumed 3-D, steady, laminar, and incompressible with constant properties. Computations have been done by solving Navier-Stokes and energy equations utilizing finite volume method. Water has been selected as the base fluid and thermo-physical properties of γ-AL_2_3/water nanofluid have been calculated using available correlations in the literature. The effects of Dean number, rib size and particle volume fraction on the heat transfer coefficient and pressure drop have been examined. Results show that nanoparticles can increase the heat transfer coefficient considerably. For any fixed Dean number, relative heat transfer rate (The ratio of the heat transfer coefficient in the case of γ-AL_2_3/water nanofluid to the base fluid) increases as the particle volume fraction increases; however, the addition of nanoparticle to the base fluid is more useful for low Dean numbers. In the case of water flow, results indicate that the ratio of heat transfer rate of ribbed duct to smooth duct is nearly independent of Dean number. Noticeable heat transfer enhancement, compared to water flow in smooth duct, can be achieved when γ-AL_2_3/water nanofluid is used as the workingfluid in ribbed duct.