Employing numerical method for evaluating the heat transfer rate of a hot tube by nanofluid natural convection

Abstract

One of the major issues in industry is cooling of pipes when using forced convection mechanism is not able to cool pipes, but free convection mechanism can be a suitable method. In this regard, a half-pipe was installed in the center of a half-elliptical enclosure in which the gap of between them was saturated with nanofluid of water and alumina (aluminum oxide) nanoparticle depending on temperature and nanoparticle diameter. Several samples were simulated by means of CFD and FVM to understand the impacts of Rayleigh number, inclined angle, and volume fraction of nanoparticles on the heat flux of hot pipe. In addition, the dynamic viscosity and thermal conductivity coefficient of nanofluid depended on temperature, nanoparticle diameter, and volume fraction, which were used for precising simulation to physical results. The obtained results showed that adding 3% volume fraction of alumina could increase the average heat flux of hot half-pipe by 8.7%. Moreover, at high Rayleigh numbers, volume fraction of 1% was optimum amount for volume fraction. In addition, inclined angle had considerable influence on average heat flux, specifically, in high Rayleigh numbers.

Keywords

• Numerical study
• Nanofluid
• Free convection
• Alumina and water
• Half-elliptical geometry