This document describes a study on the flow and heat transfer characteristics of a confined slot jet impinging on a constant heat flux surface. The study examines the effects of varying the jet width-to-height ratio (H/W) and Reynolds number (Re) on heat transfer properties. Numerical simulations are conducted to analyze the velocity contours, temperature distributions, Nusselt numbers, and pressure coefficients. Results show that heat transfer rate increases with higher H/W ratios and Re numbers. Flow and thermal fields also become time-dependent and asymmetric if Re exceeds a critical value. Validation of the numerical model is also performed.

1. Flow And Heat Transfer Characteristics On A
Confined Slot Jet Impinging On A Constant Heat Flux
Surface
By
Dahiru Umar Lawal
Abba Abdulhamid Abubakar

2. Outline
• Introduction
• Literature Review
• Problem Description & Methodology
• Results and Discussion
• Conclusion

3. Introduction
• Impinging jets are jets of fluid on an impingement surface
that needs to be cooled/heated or dried.
• Impinging jets have received considerable attention due to
their inherent characteristics of high rates of heat transfer.

4. Applications…
Impinging jets are widely applied in many industrial and engineering
applications. These includes:
 Internal cooling of turbine blades
 Cooling of laser weapons, fusion blankets, microelectronic
components and neutron beam system
 Quenching and annealing of non-ferrous sheet metals
 Tempering of glass, drying of textiles, wood, film materials and
paper
 Freezing of tissues in cryosurgery

5. Literature review
Author Reynolds Number Jet inlet
geometry
work
Sparrow et al. [1] 150 - 950 slot Derived the mass transfer correlation for the impinging
slot jet flows
Vadiraj et al. [2] 12000 - 28000 circle Study the effect of jet-to-plate spacing and Reynolds
number on the local heat transfer distribution to normally
impinging submerged circular air jet on a smooth and flat
surface
Chiriac et al. [3] 250-750 slot Investigate unsteady two-dimensional fluid flow and heat
transfer in a confined impinging slot jet using the
FAHTSO finite element codes
Fitzgerald et al. [4] 8500 - 23 000 circle Investigated the flow field of an axisymmetric, confined,
submerged, turbulent jet impinging normally on a flat
plate
Morris et al.[5] 8500 to 13 000 circle Investigate the local heat transfer coefficient distribution
on a square heat source due to a normally impinging,
axisymmetric, confined, and submerged turbulent liquid
jet

6. Objective
To study:
• The effect of Jet Width-to-Height ratio and Reynolds
number on the heat transfer characteristics of a laminar
flow Slot Jet Impinging on a constant heat flux wall

7. Problem Description
• A two-dimensional jet with uniform jet velocity enters from a
nozzle of width W into a channel with height H and length L.
• CASE 1: Re = 500 and H/W = 2 to 5 for L=25 cm
• CASE2: H/W=3 and Re= 200, 300, 400 and 500 for L=25cm
• CASE3: H/W=5 and Re= 200, 300, 400,500,600 and 750 for
L=50 cm

8. Problem Description…
• Air is used as the cooling fluid in all cases, and standard
properties of air at 300K were used.
• Governing Equations: flow assumed as 2-D, unsteady,
incompressible, and laminar, viscous dissipation effects
neglected
∇. 𝑢 = 0 1
𝜕𝑢
𝜕𝑡
+ 𝑢 . ∇u = −
1
ρ
∇p + 𝜈∇2
u 2
𝜕𝑇
𝜕𝑡
+ 𝑢 . ∇T = α∇2
T 3

9. Problem Description…
• Boundary Conditions:
Top plate:
Left and Right walls, 𝜈 = 0,u = 0 and
𝜕𝑇
𝜕𝑦
= 0
Jet inlet, 𝜈 = 𝑉𝑗 ,u = 0 and 𝑇 = 300 K
Bottomplate:
Bottom Wall, 𝜈 = 0,u = 0 and 𝑞 = 1000 W/m2
Left and Right Outlet:
𝜕u
𝜕𝑥
= 0,
𝜕u
𝜕𝑦
= 0,
𝜕𝑇
𝜕𝑥
= 0, 𝑎𝑛𝑑 p = 𝑃𝑎𝑡𝑚

10. Modeling
 Numerical Implementation in Fluent using Finite Volume Technique
 Both Steady & Unsteady analysis was carried out
 Mesh and Time independent tests were also carried.
 Computation is carried out for the entire domain as asymmetry is
expected for the unsteady regime
PROPERTIES OF AIR AT 300K and 101325Pa
Density 1.225kg/m3
Specific Heat Capacity
at constant pressure
1006.43J/kg-k
Thermal conductivity 0.0242w/m-k
Viscosity 0.000017894kg/ms

11. Results & Discussion
Velocity Contour Plot for H/W= 2, 3, 4 and 5 and Re= 500

12. Results & Discussions….
Cp & Nu for H/W= 2, 3, 4 and 5 and Re= 500

13. Results & Discussions….
Velocity Contour for Re= 200-750 and H/W=5

14. Results & Discussions….
Temperature Contour for Re= 200-750 and H/W=5

15. Results & Discussions….
Wall Pressure Coefficients for H/W=5 and Re=200-750

16. Results & Discussions….
Wall Pressure Coefficients for H/W=5, Re=750, and Time=0-6 Seconds

17. Results & Discussions….
Stagnation Nusselt Number for H/W=5 and Re=200- 750

18. Validation

19. Conclusion
• Cp varies with the H/W ratio, and peak values are
noticed in the stagnation region.
• Heat transfer rate is higher for higher H/W ratio.
• Heat transfer rate increases with increasing Reynolds
number.
• If the Reynolds number is greater than the critical
Reynolds number, the flow and the thermal fields
become time dependent and asymmetric.

20. References
1. E.M. Sparrow, T.C. Wong, Impingement transfer coefficients due to initially laminar slot jets,
Int. J. Heat Mass Transfer 18 (1975) 597–605.
2. Vadiraj, K., & Prabhu, S. V. Experimental study and theoretical analysis of local heat transfer
distribution between smooth flat surface and impinging air jet from circular straight pipe
nozzle. Heat and Mass Transfer 51(2008). 4480-4495.
3. Chiriac V.A., Ortega A., “A numerical study of the unsteady flow and heat transfer in a
transitional confined jet impinging on isothermal surface”, International Journal of Heat &
Mass Transfer, 45(2002) 1237-1248
4. J.A. Fitzgerald, S.V. Garimella, Flow field effects on heat transfer in confined jet impingement,
Trans. ASME, J. Heat Transfer 119 (1997) 630–635.
5. G. Morris, S.V. Garimella, Prediction of jet impingement heat transfer using a hybrid wall
treatment with different turbulent Prandtl number functions, Trans. ASME, J. Heat Transfer
118 (1996) 562–569.

21. THANK YOU
?