Abstract
Mixed heat convection of three-dimensional unsteady flow of four different types of fluids in a double lid-driven enclosure is simulated by a two-phase mixture model in this project. The cubic cavity with moving isothermal sidewalls has uniform heat flux on the middle part of the bottom wall, and the other remaining walls forming the enclosure are adiabatic and stationary. The relevant parameters in the present research include Reynolds number Re (5000–30,000), nanoparticle diameter (25nm–85nm), and nanoparticle volume fraction (0.00–0.08). In general, remarkable effects on the heat transfer and fluid patterns are observed by using nanofluids in comparison to the conventional fluid. Different types of nanofluids or different diameters of nanoparticles can make pronounced changes in the heat convection ratio. In addition, increasing in either volume fraction of nanoparticles or Reynolds number leads to increasing in the Nusselt number, fluctuation kinetic energy and root mean square velocity of the fluid in the domain. It is also found that both URANS and LES methods have shown good performance in dealing with unsteady flow conducted in this project. However, the comparisons have elucidated clearly the advantages of the LES approach in predicting more detailed heat and flow structures.
Highlights
In the last few years there has been a growing interest in nanofluids acting as a new heat transfer working fluid instead of conventional fluid such as oil or water
It can be seen that the Unsteady Reynolds-Averaged Navier-Stokes (URANS) model predicts slightly lower average Nusselt numbers for all volume fraction values compared to the ones derived by involving the Large Eddy Simulation (LES) model, which reflects the nature of the turbulence models
Nanoparticles’ concentration and nanoparticles’ diameter size were studied at various high values of Reynolds number. These parameters were evaluated in terms of Nusselt number, turbulent kinetic energy, root mean square velocity and isothermal contours
Summary
In the last few years there has been a growing interest in nanofluids acting as a new heat transfer working fluid instead of conventional fluid such as oil or water. Adding nanoparticles into base fluids plays vital roles in the thermal properties of heat transfer fluids. The main concern of mixing metal micro-particles within base fluids can be traced back to Maxwell’s study decades ago but not without major drawbacks such as high pressure drop. These disadvantages have been solved perfectly over few years back through reducing the particles size to the nanometer range. Considerable attention has been paid to the research on these fluids in mixed convection of lid-driven cavity, due to their extensive industrial and engineering applications in, for instance, electronic cooling, solar collectors, coating and mixing, air conditioning and air cooling systems [1]
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