Analysis of Turbulent Flow an‎d Mixed Convection of Hybrid Nanofluid in impingement jet with NEPCMs

1/1/1900 12:00:00 AM

In this thesis, the flow an‎d heat transfer of turbulent mixed convection in an impinging jet with the presence of nanofluids containing phase change material, metal oxide nanofluids an‎d hybrid nanofluids under constant heat flux are investigated. Considering the topic of improving heat transfer, storage an‎d efficiency in applications such as geothermal energy storage, solar collectors an‎d heat exchangers, the use of encapsulated phase change nanofluids an‎d also hybrid nanofluids containing encapsulated phase change material nanoparticles along with metal oxide nanoparticles is important. The survival equations are discretized an‎d solved using the finite volume method. To achieve this goal, the nanofluid is first viewed from the perspective of a single-phase fluid with variable thermophysical properties an‎d then treated as a two-phase suspension including the base fluid an‎d nanoparticles. RANS an‎d the combined RANS/LES approach (SAS approach) are used to analyze turbulence. In comparing the single-phase an‎d two-phase methods, it has been shown that although both methods correctly predict the effect of Reynolds number an‎d nanoparticle volume fraction on the convective heat transfer coefficient an‎d Nusselt number, the accuracy of the two-phase method is higher. With increasing Reynolds number, the convective heat transfer coefficient an‎d Nusselt number will increase at all volume fractions. For example, at a volume fraction of 2.8% of the metal oxide nanofluid of water an‎d aluminum oxide, because the averaged Navier-Stokes equations approach is unable to accurately predict the generated vortices an‎d turbulent flow characteristics an‎d its application to time-dependent flow does not lead to sufficient information about the flow details. Therefore, in the second part, the SAS coupled approach has been used. Phase change nanoparticles show better thermal performance than single phase base fluid (water) an‎d hybrid nanoparticles including encapsulated phase change material nanoparticles have better thermal an‎d hydrodynamic performance compared to other nanofluids. Nanofluids of 5% an‎d 10% n-octadecane improve heat transfer by 16.89% an‎d 19.78%, while hybrid nanofluids (1% copper oxide an‎d 5% n-octadecane) an‎d (2% copper oxide an‎d 10% n-octadecane) improve heat transfer by 24% an‎d 52.29%, respectively. With increasing volume fraction, the friction coefficient increases slightly compared to pure water. The increase in the friction coefficient for the 5% n-octadecane nanofluid an‎d the hybrid nanofluid (1% copper oxide an‎d 5% n-octadecane) is 3.26% an‎d 2.87%, respectively. The present results show that the Reynolds shear stress an‎d turbulent heat flux increase with the addition of nanoparticles to pure water. The results indicate that the hybrid nanofluid containing copper oxide nanoparticles an‎d encapsulated phase change material nanoparticles has better thermal performance than the nanofluid containing only encapsulated nanoparticles an‎d pure water due to the simultaneous higher thermal conductivity an‎d specific heat capacity. Therefore, the hybrid nanofluid with encapsulated phase change material nanoparticles is a suitable choice in thermal energy storage an‎d heat transfer applications.

جت برخوردي , نانوسيال حاوي ماده تغييرفاز دهنده كپسوله شده , جابجايي مختلط , مدل‌هاي تك‌فاز و دوفاز , نانوسيال هيبريد , رهيافت شبيه‌سازي مدل‌هاي آشفتگي پيوندي

impinging jet , nanofluid containing encapsulated phase change material , mixed convection , single-phase an‎d two-phase models , hybrid nanofluid , coupled turbulence model simulation approach

Mohammad Farid Abdi

Farzad Bazdidi Tehrani