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Research Papers

# Detailed Heat Transfer Measurements of Jet Impingement on Dimpled Target Surface Under Rotation

[+] Author and Article Information
Prashant Singh

Department of Mechanical Engineering,
Virginia Tech,
445 Goodwin Hall, 635 Prices Fork Road,
Blacksburg, VA 24060
e-mail: psingh1@vt.edu

Department of Mechanical Engineering,
Virginia Tech,
445 Goodwin Hall, 635 Prices Fork Road,
Blacksburg, VA 24060

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received July 11, 2016; final manuscript received November 28, 2017; published online March 28, 2018. Assoc. Editor: Ting Wang.

J. Thermal Sci. Eng. Appl 10(3), 031006 (Mar 28, 2018) (14 pages) Paper No: TSEA-16-1196; doi: 10.1115/1.4039054 History: Received July 11, 2016; Revised November 28, 2017

## Abstract

The present study investigates the effects of Coriolis force and centrifugal buoyancy force on heat transfer due to jet impingement on dimpled target surface (DT). Detailed heat transfer measurements were carried out using transient liquid crystal (LC) thermography, where the target surface was modeled as one-dimensional (1D) semi-infinite solid. Three different configurations of DT surfaces have been studied. The flow and rotation conditions have been kept the same for all the configurations, where the average Reynolds number (based on jet hole hydraulic diameter: $Rej$) was 2500 and the rotational speed was 400 rpm (corresponding to $Roj$ of 0.00274). Under nonrotating conditions, DT surface showed positive heat transfer enhancements compared to smooth target surfaces. Under rotating conditions, it was observed that rotation was helpful in enhancing heat transfer on leading and trailing sides for smooth target surface. However, for the DT surfaces, rotation proved to be detrimental to heat transfer enhancement.

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## References

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## Figures

Fig. 1

Schematic of experimental setup

Fig. 2

Description of configuration, details of dimensions, relative arrangements of dimples and impinging jets

Fig. 3

Side view of impingement, dimpled target and spent flow direction

Fig. 4

Demonstration of jet impingement, coolant flow in feed chamber, spent air flow in impingement channel—relative to rotation

Fig. 5

Sample time-temperature history of wall and coolant temperature, the gray (green) region indicating αϵ[0.3,0.7]

Fig. 6

Discharge coefficient of two jet plates (ST1 and ST2)

Fig. 7

Jet exit Mach number variation with feed plenum pressure ratios for the two jet plates under consideration

Fig. 8

Jet mass flux to average jet mass flux ratio plotted with increasing streamwise distance

Fig. 9

Crossflow mass flux to jet mass ratio plotted with increasing streamwise distance

Fig. 10

Comparison of globally averaged Nusselt number obtained experimentally in the present study with well-established correlations (jet impingement on smooth target surface)—refer Table 2 for values used in this figure

Fig. 11

Detailed Nusselt number contours for all the configurations studied

Fig. 12

Normalized Nusselt number pitch-wise averaged plots, (a) ST1 Nusselt numbers normalized with ST1 stationary case, (b) DT1 Nusselt numbers normalized with corresponding cases of ST1, and (c) DT1 Nusselt numbers normalized with stationary case of DT1

Fig. 13

Normalized Nusselt number pitch-wise averaged plots, (a) ST2 Nusselt numbers normalized with ST2 stationary case, (b) DT2 Nusselt numbers normalized with corresponding cases of ST2, (c) DT2 Nusselt numbers normalized with stationary case of DT2, (d) DT3 Nusselt numbers normalized with corresponding cases of ST2, and (e) DT3 Nusselt numbers normalized with stationary case of DT3

Fig. 14

Rotation-induced forces

Fig. 15

Heat transfer enhancement for dimpled target surface (compared with smooth target) under nonrotating conditions

Fig. 16

Effect of rotation on heat transfer enhancement by dimpled target surface (compared with corresponding stationary cases)

Fig. 17

Effect of rotation on heat transfer enhancement by dimpled target surface (compared with corresponding cases of smooth target impingement)

Fig. 18

Globally averaged Nusselt number enhancement for stationary, leading and trailing side impingement for the three configurations of dimpled target surface

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