Numerical study of turbulent heat transfer and flow characteristics of hot flow over a sudden-expansion with base mass injection

SummaryThis study presents the numerical calculations of the fluid flow and turbulent heat transfer characteristics of hot flow over a sudden-expansion with cold air base mass injection. The turbulent governing equations are solved by a control-volume-based finite-difference method with power-law scheme, the well knownk-ε model, and its associate wall function to describe the turbulent behavior. The velocity and pressure terms of momentum equations are solved by the SIMPLE (Semi-Implicid Method for Pressure-Linked Equation) method. In this study non uniform staggered grids are used. The parameters interested include the inlet Reynolds number (Re), inlet temperature (T0), and the injection flow rate (Q). The numerical results show that the reattachment lengths are reasonably predicted with a maximum discrepancy within 9.1%. It also shows that the base mass injection suppresses the horizontal velocity and turbulence intensity. In these high temperature heat transfer characteristics, the heat transfer coefficient increased with increasing inlet temperature and inlet Reynolds number, but decreased with increasing injection flow rate of the cooling air.

[1]  B. Launder,et al.  The numerical computation of turbulent flows , 1990 .

[2]  Bassem F. Armaly,et al.  Mixed convection in buoyancy-assisting, vertical backward-facing step flows , 1990 .

[3]  Ephraim M Sparrow,et al.  Turbulent Heat Transfer in the Separated, Reattached, and Redevelopment Regions of a Circular Tube , 1966 .

[4]  E. G. Filetti,et al.  Heat Transfer in Separated, Reattached, and Redevelopment Regions Behind a Double Step at Entrance to a Flat Duct , 1967 .

[5]  Shinji Honami,et al.  The Effect of Inlet Turbulence Intensity on the Reattachment Process Over a Backward-Facing Step , 1989 .

[6]  James P. Johnston,et al.  Investigation of a Reattaching Turbulent Shear Layer: Flow Over a Backward-Facing Step , 1980 .

[7]  C. Jayatilleke,et al.  The influence of Prandtl number and surface roughness on the resistance of the laminar sub-layer to momentum and heat transfer , 1966 .

[8]  De Groot,et al.  Laser Doppler diagnostics of the flow behind a backward facing step , 1985 .

[9]  Jing-Tang Yang,et al.  High temperature heat transfer of separated flow over a sudden-expansion with base mass injection , 1996 .

[10]  S. Patankar.  Numerical Heat Transfer and Fluid Flow , 2018, Lecture Notes in Mechanical Engineering.

[11]  Ephraim M Sparrow,et al.  Relation between the points of flow reattachment and maximum heat transfer for regions of flow separation , 1987 .

[12]  Chung-Lun Kuo,et al.  Numerical study of a backward-facing step with uniform normal mass bleed , 1997 .

[13]  Tetsuo Hirata,et al.  Turbulent Fluctuations and Heat Transfer for Separated Flow Associated With a Double Step at Entrance to an Enlarged Flat Duct , 1976 .

[14]  John K. Eaton,et al.  A Review of Research on Subsonic Turbulent Flow Reattachment , 1981 .

[15]  W. Aung.  An experimental study of laminar heat transfer downstream of backsteps , 1983 .

[16]  John K. Eaton,et al.  Combined Heat Transfer and Fluid Dynamic Measurements Downstream of a Backward-Facing Step , 1985 .

[17]  Win Aung,et al.  Starting Flow and Heat Transfer Downstream of a Backward-Facing Step , 1991 .

[18]  J. A. Schetz,et al.  Turbulent boundary layer with injection and surface roughness , 1977 .

[19]  Go-Long Tsai,et al.  Separated-Reattaching Flow Over a Backstep With Uniform Normal Mass Bleed (Data Bank Contribution) , 1994 .