Impact of Surface Roughness on Flow Physics and Entropy Generation in Jet Impingement Applications

Area of Science:

• Fluid Dynamics
• Heat Transfer
• Thermodynamics

Background:

• Air jets impacting heated surfaces are common in industrial applications.
• Entropy generation due to heat and friction impacts system efficiency.
• Surface modifications offer a potential method to control flow physics and entropy.

Purpose of the Study:

• To numerically investigate the impact of circular surface ribs on entropy generation.
• To analyze flow physics, vortex generation, and heat transfer characteristics.
• To determine optimal rib dimensions and locations for minimizing entropy generation.

Main Methods:

• Numerical investigation of an air jet impinging normally on a horizontal heated plane.
• Utilized concentric circular ribs as surface roughening elements.
• Varied rib radii (R/D), heights (e/D), and jet Reynolds numbers (Re).

Main Results:

• A suitable rib height reduced total entropy (St) by up to 31% compared to a smooth surface.
• Entropy generated by friction (Sf) dominated over heat exchange (Sh) for specific rib heights.
• Rib placement at R/D = 1 resulted in the highest total entropy generation (St).

Conclusions:

• Surface ribs can be effectively used to manage entropy generation in impinging air jets.
• Optimizing rib geometry and location offers a favorable trade-off between entropy generation and heat transfer.
• The Bejan number increases with both rib height and location, indicating altered irreversibility distribution.