|
The paper presents the influence of crossflow, surface motion
and entrainment boundary on the flow and heat
transfer characteristics of a turbulent slot jet
impinging on an isothermal surface. The parameters
studied include the jet Reynolds number (Rej ),
dimensionless nozzle-to-surface spacing (H/W), the ratio of
crossflow mass flow rate to the jet mass flow rate (M) and the
ratio of impingement surface velcity to the mean jet velocity
(Us/Vj ). The governing equations are solved by a control-
volume based finite-difference method with power-law
scheme and the well known ｋ - ε model and its associate
wall function to describe the turbulence structure. The
velocity and pressure terms of momentum equations are
solved by SIMPLE (Semi-Implicit Methods for Pressure-Linked
Equation). It is found that the flow between the walls
closer to a channel flow when both sides of the slot jet is
confined. In the case of confined surface, as the nozzle-to-
surface spacing (H/W) increases, discrepancy of the shear
stress and local Nusselt number between the prediction and
experiment of Gardon & Akfirat [1] is about 20 ％. As M
increases, the maximum value of the shear stress decreases
and its position shift downstream a little with considering
the effect of crossflow. The increase of shear stress due to
the increase of surface velocity is presented when both the
crossflow and surface motion effect are imposed. The local
Nusselt number increases with increasing surface motion
velocity in the upstream, and decreases in the downstream. In
the case with entrainment boundary and surface motion, the
ambient fluid enter the jet flow field, it is not like a
channel flow. It is found that near the jet the influence of
the surface motion is more significant than the upstream and
downstream region.
|