A comparison study of two-phase model in turbulent heat transfer using nanofluids as a coolant in a heat exchanger

Turbulent forced convection of different nanofluids consisting of -Al2O3/Water and CuO/Water in a concentric double tube heat exchanger has been investigated numerically. Nanofluids that areused as coolants flowing in the inner tube while hot pure water flows in outer tube. The study areconducted for Reynolds numbers ranging from 20,000 to 50,000 and nanoparticles volume fractions of 2, 3, 4 and 6 percent. The three-dimensional governing equations are discretized using the finite volume approach. Although, two different nanoparticles have almost the same thermal conductivity but using CuO/Water nanofluid showing better enhancement in heat transfer that proves thermal conductivity is not the only reason of enhancing heat transfer. Also, CuO/Watershowing bigger shear stress in comparison of -Al2O3/Water nanofluid. Comparison between two different two-phase models (Mixture and VOF) shows that they predict identical values. As a result, VOF models is preferred for present study because this approach is less expensive than those common mixture model

Keywords:

Turbulent forced convection , Nanofluid , Concentric double tube heat exchanger , Two-phase models