Numerical investigation of heat transfer characteristics and flow structure inside sudden expansion channel

In the present work, a numerical simulation of a sudden expansion channel is investigated under the variation of Reynolds number (Re), expansion ratio (H/h), and expansion length (Le) to study the effect of these parameters on the heat transfer rate and flow behavior inside the sudden expansion zone. The range of (Re) from 4000 to 20000 and the expansion ratio of (1.25, 1.5 and 2) while the expansion length of (Le = 1, 1.5, 2 m). All the tests were applied at a constant heat flux of (1000 w/m2). A two-dimensional numerical simulation is employed to solve the governing equation using Ansys fluent. Results show a strong vortex is generated at a high expansion ratio with a short expansion passage length as well as the absence of the reattachment point in the downstream direction for all Reynolds numbers. Also, for (Re = 4000), with decreasing the expansion ratio form (H/h = 2) to (H/h = 1.5) lead to enhance the local Nusselt number at (x = 0.6 m) of about (72%).