摘要：The gaseous low-pressure nanofluid flow of a steady-state two-dimensional laminar forced convection heat transfer in the entrance region of pipes is numerically investigated. Such flows are of interest for many engineering applications like the nuclear reactor and electronic equipment cooling, heat exchangers, and many others. Physical parameters considered in this study are Reynolds number (Re), Prandtl number (Pr), nanosolid particles volume fraction ( ϕ ) , Knudsen number (Kn), and the aspect ratio (AR). These parameters ranges are as follows: 500 ≤ Re ≤ 2000 , 0 . 76 ≤ Pr ≤ 0 . 95 , 0 ≤ ϕ ≤ 0 . 5 , 0 ≤ Kn ≤ 0 . 1 , and 1 ≤ AR ≤ 10 . The outcome of this study shows that by increasing Kn, velocity slip and temperature jump at the solid boundaries increase. In addition, heat transfer is enhanced by dispersing Al2O3 nanoparticles in the base low-pressure gaseous flow. Results show that there is no effect of the nanoparticles volume fraction with values below 0.03 on the average Nusselt number. The average Nusselt number increases ( Nu ¯ ) as the value of the nanoparticles volume fraction exceeds 0.03. For instance, at Re = 1000, results show that when dispersing Al2O3 nanosolid particles with volume fractions of 0.3 and 0.5; there is an enhancement in the average Nusselt number of 30.35% and 136.74%, respectively, when compared to the case of dispersing Al2O3 nanosolid particles of 0.03 volume fraction.. Moreover, it is concluded that the average Nusselt number ( Nu ¯ ) depends directly on Reynolds (Re), Prandtl (Pr) numbers, and the nanoparticles volume fraction ( ϕ ) and inversely on Knudsen number (Kn) and the aspect ratio (AR) for the investigated range of parameters considered in this study. Finally, a correlation of Nusselt number among all the investigated parameters in this study is proposed as Nu ¯ = 0 . 976 A R − 0 . 0536 P r 2 . 39 R e 0 . 22 K n − 0 . 378 ϕ 0 . 07 .
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