title: Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger.
abstract: This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%-0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%-24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles.
authors.affiliation: Department of Chemical Engineering, Shahrood Branch, Islamic Azad University, Shahrood 36199-43189, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Aghayari
authors.affiliation: Department of Chemistry, Sciences Faculty, Arak Branch, Islamic Azad University, Arak, Iran.
authors.forename: Heydar
authors.initials: H
authors.lastname: Maddah
authors.affiliation: Department of Chemical Engineering, Shahrood Branch, Islamic Azad University, Shahrood 36199-43189, Iran.
authors.forename: Malihe
authors.initials: M
authors.lastname: Zarei
authors.affiliation: Department of Chemical Engineering, Damghan Branch, Islamic Azad University, Damghan 36716-39998, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Dehghani
authors.affiliation: Department of Chemistry, Saveh Branch, Islamic Azad University, Saveh 39197-15179, Iran.
authors.forename: Sahar Ghanbari
authors.initials: SG
authors.lastname: Kaskari Mahalle