Effect of baffle angles on flow and heat transfer in a circular duct with nanofluids.

This work numerically analyzes the hydraulic and thermal performance of CuO-water nanofluid in a circular duct with different baffle angles. In the numerical work, governing equations are discretized with the finite volume method, and the simulations are solved with SIMPLE algorithm. The surfaces of the duct containing baffles are kept at 340 K. In the analysis, the effects of different Reynolds numbers (200 ≤ Re ≤ 1000), nanoparticle volume fractions (1% ≤ ϕ ≤ 3%), and baffle angles (30º ≤ α ≤ 150º) on the thermal enhancement factor (η) and the friction factor are investigated. In addition, the flow and temperature contours are presented for different parameters within the duct. From those contours, it is observed that the baffles cause flow oscillation and recirculation zones are formed. The numerical results show that baffles and nanofluid flow contribute significantly to the thermal enhancement. The Nusselt number (Nu) and relative friction factor (r) increase as the Reynolds number and nanoparticle volume fraction increase. While the highest thermal enhancement factor and relative friction factor are obtained at α = 90º baffle angle, the best performance evaluation criterion (PEC) value is found at α = 150º baffle angle. [ABSTRACT FROM AUTHOR]