دراسة كمية ونوعية لأداء المبادلات الحرارية ثنائية الأنابيب باستخدام السوائل النانوية القائمة على الماء

Abstract

Heat exchangers are very important equipment for cooling and heating processes in different industrial fields and applications. The heat transfer performance of base fluids is greatly improved with suspended nanoparticles in a variety of applications such as solar collectors, heat pipes, nuclear reactors, cooling systems, automotive radiators, and more. In the present thesis, the problem of flow of nanofluids with forced convection is studied in detail in three cases, under constant mass flow rates (Case 1), under optimized mass flow rates with two different geometric configuration scenarios of the heat exchangers, N-shaped pipe heat exchanger (Case 2) and M-shaped pipe heat exchanger (Case 3). Numerical results in the previous works, as obtained for water–Al2O3 mixture, have been demonstrated that of nanoparticles into the base fluids fluid led to a significant increase of the heat transfer coefficient, which clearly increases with an increase in particle concentration. However, those particles also caused drastic effects on the wall shear stress that increases correspondingly with the particle loading. Therefore, in the current study, the full performance of the different heat exchanger designs will be investigated numerically under the effect of different particle concentrations and different nano materials such as Al2O3, CuO, TiO2 and SiO2. Additionally, the Computational Fluid Dynamics (CFD) single-phase model is adopted for predicting the heat transfer performance in fluent using ANSYS. Therefore, the results show enhancement in heat transfer for the heat exchanger is due to increased volume fraction, and a direct correlation between overall heat transfer effectiveness and volume fraction percentage of nanofluids, while CuO was proven most effective amongst considered nano particles and has reached an optimum overall heat transfer effectiveness estimated around 89% under 4.5% volume fraction percentage. Besides, adjusting the geometry into an M-shaped pipe had resulted in an enhanced heat transfer effectiveness.