Numerical study of conjugate heat transfer in laminar and turbulent nanofluid flow in double pipe heat exchangers

In this paper, the conjugate heat transfer for water-AI2O3 nanofluid flow in double pipe heat exchangers was numerically modeled. The important parameters such as temperature distribution, local heat transfer coefficient, 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 nanofluid. The nanofluid flow was modeled by employing a twophase mixture method. The findings indicate that parallel or counter flows have a more significant effect 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 effective mechanism is to use nanofluids in the tube containing the warm fluid. Similarly, for cooling a warm fluid, the most efficient method is to use nanofluids in the tube containing the cold fluid (using the nanofluid in the other tube).