Department of Mechanical Engineering, Faculty of Engineering, Arak University, Arak, P.O. Box 38156-88349, Iran.
In this paper, the conjugate heat transfer for water-Al2O3 nano fluid flow in double pipe heat exchangers was numerically modeled. The important parameters such as temperature distribution, local heat transfer coecient, pressure drop, and the heat transfer rate in inner and outer fluids were evaluated and compared. All the obtained results were simultaneously analyzed for parallel and counter flows, laminar and turbulent flows, and the presence or absence of nano fluid. The nano fluid flow was modeled by employing a twophase mixture method. The ndings indicate that parallel or counter flows have a more signicant eect on the heat transfer performance in the laminar flow than the turbulent one. The results also show that for warming a cold fluid, the most eective mechanism is to use nano fluids in the tube containing the warm fluid. Similarly, for cooling a warm fluid, the most ecient method is to use nano fluids in the tube containing the cold fluid (using the nano fluid in the other tube).