Numerical investigation of nanofluid heat transfer in helically coiled tubes using the dispersion model

In the present work, laminar, incompressible, steady state viscous flow in helically coiled tubes is studied numerically to investigate the forced convective heat transfer behavior of nanofluid. The three dimensional governing equations are solved using finite difference method with projection algorithm. Periodic boundary conditions in axial direction for momentum equation and constant wall temperature for energy equation are considered. Dispersion model is used to predict enhancement of nanofluid heat transfer because of irregular movements of the nanoparticles. Heat transfer of nanofluids using dispersion model is compared with homogenous model with constant effective properties and pure fluids in helical coiled tubes with different curvature ratio and Reynolds number that has not been studied by previous investigations. In addition, the effect of volume fraction of the nanoparticles on Nusselt number is studied. The results of pure fluid flow in helical coils are validated by previous studies, and dispersion model is validated by previous work done in straight tubes. The results show heat transfer enhancement of nanofluids to pure fluids. The dispersion model predicts more heat transfer enhancement than homogenous model with effective properties in helical tubes. Also enhancement of Nusslet number with increment of curvature of coils and volume fraction of the nanoparticles can be seen.

کلیدواژه ها:

Nanofluid ، Dispersion model ، Convection ، Helical coiled ، Projection algorithm