Two-phase computation of free convection and entropy generation inside an enclosure filled by a hybrid Al2O3-TiO2-Cu water nanofluid having a corrugated heat source using the generalized Buongiorno’s mathematical model: Employment of finite volume method

Abstract In this article we studied the entropy generation and natural convection of hybrid nanofluid ( A l 2 O 3 - Ti O 2 - Cu and Water) in an enclosure containing a central wavy heated source using the generalized Buongiorno’s mathematical model (i.e., two-phase mixture model). Finite volume method has been used to discretize the governing equations. The studied parameters related to this problem are Rayleigh number 10 3 ≤ R a ≤ 10 6 , proportion of hybrid nanoparticles 0 % ≤ φ ≤ 5 % and dimensionless amplitude of corrugated heater 0 ≤ a ≤ 0.2 . It has been found that the increase in the value of corrugated heater amplitude improves the efficiency of hybrid nanofluid heat transfer inside the enclosure so that it enhances compared to the case of straight heater. In addition, it was concluded that increasing the percentage of hybrid nanoparticles in the base fluid raises the rate of heat transfer. The effect of the problem parameters ( a and φ ) on the heat transfer rate changes with respect to each different values of Rayleigh number, it can be optimized. In addition, the different irreversibility types (entropy due to mass transfer S MT , heat transfer S HT , fluid friction S FF ) have been performed for different Ra numbers and corrugations amplitude. It is found that all mean entropies raise by changing the corrugation amplitude from 0 to 0.2 and they are affected significantly by the growth of Ra number and volume fraction of hybrid nanoparticles. The total entropy generation S T was also calculated and plotted. Moreover, the mean Bejan number variation B e - was studied to determinate the dominant irreversibility type. It is found that the mass and heat irreversibility are dominant at low Ra number ( 10 4 ), on the other hand, for the higher Ra number the fluid friction irreversibility is the dominant. Furthermore, the two-phase simulation has been performed for studying the hybrid nanoparticles distribution. It is found that the maximum volume fraction of hybrid nanoparticles is placed on the bottom left and right corners of the cavity and its uniform values situated on the medium of the hybrid nanofluid, while this uniform part becomes wide when increasing Ra number from 10 4 to 10 6 .