2.2. Validation
As shown in Fig. 2a, grid independence test was performed for the studied cavity filled with Al2O3-MWCNT/water hybrid nanofluid to analyze the effects of grid sizes on the results for generated grid mesh. In this section, the Al2O3nanoparticles volume fraction is 0.05 and the MWCNT nanoparticles volume fraction is 0.01. Furthermore, three different Reynolds numbers are considered to analyze the effects of various flow velocities on the grid mesh independency test. As it is seen numerous sets of mesh are generated and tested versus different Reynolds numbers. By comparing the results, it is concluded that mesh configuration contains 468986 nodes is assumed to get a satisfactory agreement between the computational time and the accuracy of results with the maximum error of 1 percent. It is realized that for all studied models the appropriate node numbers are achieved for the case at Re=8000. Therefor for all studied configurations and cases in present work. The model with 468986 nodes has been employed. Also, Fig. 2b illustrates images of produced grid mesh in present study.
Also, the validation was performed by comparison of present numerical findings and experimental results of Dudley et al. [62] at similar geometrical dimension and boundary conditions. These results, in case of energy efficiency variations versus s = (Tout -Tin )/Ib , compressions are displayed in Fig. 3. It can be understood from this figure that a good agreement (with maximum 10.12% error) exists among the empirical data of Dudley et al. [62] and numerical findings gained from present study.