Alexandria Engineering Journal (Feb 2023)
Heat transfer and entropy analysis for nanofluid flow in a semi-circular open cavity under mixed convection
Abstract
This paper presents a numerical simulation of nanofluid flowing in an open cavity under mixed convection by considering various heat transfer zones. To enhance the heat transfer, water was augmented with copper nanoparticles at different ϕ (volume fraction of nanoparticles) values. The present paper aims to determine the optimal position which maximizes the heat transfer in a circular open cavity. Also, in this research the investigation of combined convection flow in a specific geometry, taking into account the changes in the flow parameters, is an attempt to model the temperature field and heat transfer. For this purpose, the nanofluid flow for Reynolds numbers of Re =10, 50 and 100 is investigated. On the other hand, the hot areas in the curved part of the open cavity are separated in various cases. The results show that due to the low velocity of the fluid in the circular part of the cavity, especially in the hot wall area, most of the fluid exchange is due to natural convection due to density difference and the hot areas are strengthen the flow circulation. The exchange is also improved by increasing Re (Reynolds number) or the momentum term, and the distribution of T (temperature) in the cavity becomes more uniform. Hot spots with low heat transfer coefficient were attenuated at higher Re. The most suitable temperature distributions were achieved for W4 and W2. By increasing ϕ, the friction factor decreases for pure water, especially in W2 and W3. However, due to fluid-surface impact at Re = 100 in W2 and W3, the friction factor does not change significantly by altering ϕ. Using a higher Re and the dominance of the fluid momentum in comparison with the viscous force, the effect of nanoparticle concentration decreases. In general, the best heat transfer occurs at higher volume fraction of nanoparticles. Finally, at all Reynolds numbers, the heat transfer increases by 8–19%. This is because nanoparticles are added to pure water (working fluid).
