Heterogeneous nanofluids: natural convection heat transfer enhancement

Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case

Mixed convection in a channel partially filled with metal foam blocks

The present work is a numerical simulation of the mixed convection of an incompressible fluid in a horizontal channel under sun radiation partially filled with metal foam blocks. The Darcy-Brinkman model is adopted. The control volume approach is used to solve the motion and energy equations governing mixed convection. The study focuses on the effect of certain control parameters such as the Rayleigh number (Ra), the thermal conductivity ratio and the porosity on the flow structure and heat transfer. Indeed, the results for flow structures and temperature distribution are presented in the form of velocity fields with streamtraces and isotherms, while the average Nusselt number (Nu) is used to quantify heat transfer

Mixed convection in a channel partially filled with metal foam blocks

The present work is a numerical simulation of the mixed convection of an incompressible fluid in a horizontal channel under sun radiation partially filled with metal foam blocks. The Darcy-Brinkman model is adopted. The control volume approach is used to solve the motion and energy equations governing mixed convection. The study focuses on the effect of certain control parameters such as the Rayleigh number (Ra), the thermal conductivity ratio and the porosity on the flow structure and heat transfer. Indeed, the results for flow structures and temperature distribution are presented in the form of velocity fields with streamtraces and isotherms, while the average Nusselt number (Nu) is used to quantify heat transfer