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Research Papers

# Heat Transfer From an Isothermally Heated Flat Surface Due to Confined Laminar Twin Oblique Slot-Jet Impingement

[+] Author and Article Information

Mem. ASME
Aerospace Engineering
and Mechanics Department,
Aerospace Engineering,
The University of Alabama,
Tuscaloosa, AL 35487-0280
e-mail: msharif@eng.ua.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received August 13, 2014; final manuscript received January 30, 2015; published online March 31, 2015. Assoc. Editor: Srinath V. Ekkad.

J. Thermal Sci. Eng. Appl 7(3), 031001 (Sep 01, 2015) (11 pages) Paper No: TSEA-14-1190; doi: 10.1115/1.4029881 History: Received August 13, 2014; Revised January 30, 2015; Online March 31, 2015

## Abstract

Convective heat transfer from a heated flat surface due to twin oblique laminar slot-jet impingement is investigated numerically. The flow domain is confined by an adiabatic surface parallel to the heated impingement surface. The twin slot jets are located on the confining surface. The flow and geometric parameters are the jet exit Reynolds number, distance between the two jets, distance between the jet exit and the impingement surface, and the inclination angle of the jet to the impingement surface. Numerical computations are done for various combinations of these parameters, and the results are presented in terms of the streamlines and isotherms in the flow domain, the distribution of the local Nusselt number along the heated surface, and the average Nusselt number at the heated surface. It is found that the peak and the average Nusselt number on the hot surface mildly decreases and the location of the stagnation point and the peak Nusselt number gradually moves downstream as the impingement angle is decreased from 90 deg. The heat transfer distribution from the impingement surface gets more uniform as the impingement angle is reduced to 45 deg and 30 deg at lager jet-to-plate distance (4–8) with a corresponding overall heat transfer reduction of about 40% compared to the normal impinging jet case. The specified jet exit velocity profile boundary condition has considerable effect on the predicted Nusselt number around the impingement location. Fully developed jet exit velocity profile correctly predicts the Nusselt number when compared to the experimental data.

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## Figures

Fig. 1

Top—schematic of the flow geometry; bottom—sample mesh for the right half of the domain; L = 2, H = 6

Fig. 2

Convergence of local Nusselt number distribution on the hot bottom surface with mesh refinement

Fig. 3

Comparison of the predicted local Nusselt number distribution at the impingement surface with the experimental data

Fig. 4

Streamlines for the case with L = 4 and H = 4 (colored version is available online) (a) φ = 90 deg, (b) φ = 75 deg, (c) φ = 60 deg, (d) φ = 45 deg, and (e) φ = 30 deg

Fig. 5

Streamlines for the case with L = 4 and H = 8 (colored version is available online) (a) φ = 90 deg, (b) φ = 75 deg, (c) φ = 60 deg, (d) φ = 45 deg, and (e) φ = 30 deg

Fig. 6

Pressure coefficient distribution on the impingement surface for a few representative cases

Fig. 7

Skin friction coefficient distribution on the impingement surface for a few representative cases

Fig. 8

Isotherms for the case with L = 4 and H = 4 (colored version is available online) (a) φ = 90 deg, (b) φ = 75 deg, (c) φ = 60 deg, (d) φ = 45 deg, and (e) φ = 30 deg

Fig. 9

Isotherms for the case with L = 4 and H = 8 (colored version is available online) (a) φ = 90 deg, (b) φ = 75 deg, (c) φ = 60 deg, (d) φ = 45 deg, and (e) φ = 30 deg

Fig. 10

Distribution of the local Nusselt number at the hot bottom surface at different jet impingement angles, H = 2

Fig. 11

Distribution of the local Nusselt number at the hot bottom surface at different jet impingement angles, H = 4

Fig. 12

Distribution of the local Nusselt number at the hot bottom surface at different jet impingement angles, H = 6

Fig. 13

Distribution of the local Nusselt number at the hot bottom surface at different jet impingement angles, H = 8

Fig. 14

Variation of the maximum Nusselt number and its X-location on the hot bottom surface as a function of the jet impingement angle for various combinations of L and H

Fig. 15

Average Nusselt numbers at the hot bottom surface as a function of the jet impingement angle for various combinations of L and H

Fig. 16

Average Nusselt numbers at the hot bottom surface as a function of H for various combinations of L and φ

Fig. 17

Local Nusselt number distribution on the hot impingement plate for various jet exit velocity profiles

Fig. 18

Local Nusselt number distribution on the hot impingement plate as functions of jet channel length, and the corresponding jet exit velocity profiles

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