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Research Papers: Porous Media

Experimental Pressure Drop and Heat Transfer in a Rectangular Channel With a Sinusoidal Porous Screen

[+] Author and Article Information
Gazi I. Mahmood

Mechanical Engineering Department,
University of Saskatchewan,
Saskatoon, SK S7N 5A9, Canada
e-mail: Gazi.Mahmood@up.ac.za

Carey J. Simonson

Mechanical Engineering Department,
University of Saskatchewan,
Saskatoon, SK S7N 5A9, Canada
e-mail: Carey.Simonson@usask.ca

Robert W. Besant

Mechanical Engineering Department,
University of Saskatchewan,
Saskatoon, SK S7N 5A9, Canada
e-mail: bob.besant@usask.ca

1Corresponding author.

2Present address: Mechanical and Aerospace Engineering Department, University of Pretoria, Pretoria 0028, South Africa.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received July 30, 2014; final manuscript received November 25, 2014; published online January 13, 2015. Assoc. Editor: Ali Khounsary.

J. Heat Transfer 137(4), 042601 (Apr 01, 2015) (11 pages) Paper No: HT-14-1499; doi: 10.1115/1.4029349 History: Received July 30, 2014; Revised November 25, 2014; Online January 13, 2015

Experiments are conducted to investigate turbulence enhancing effects of a porous mesh-screen with a sinusoidal shape normal to the flow direction inside a rectangular cross section air channel at low Reynolds numbers (i.e., Re = 1360–3800). The baseline measurements are obtained at the same channel and Reynolds numbers without the screen present. The surface of the screen pores are oriented parallel to the mean flow. Data are presented for the total and wall-static pressure drop along the channel, Nusselt number distributions on the heated wall at several constant heat rates, and air temperature distributions at the channel exit with and without (baseline cases) the screen. The heat transfer measurements are obtained with one wall heated as well as two parallel walls heated to simulate different applications for air channels in the flat plate heat exchangers. The results indicate that the ratio of screen channel to baseline Nusselt number (Nu/Nu0) and the ratio of screen channel to baseline friction factor (f/f0) increase with the Reynolds number (Re). The fully developed Nu/Nu0 is 2.0–2.5 as the fully developed f/f0 is 4.4 at 3100 < Re ≤ 3800. However, the screen channel heat convection performance index, (Nu/Nu0)/(f/f0)1/3 is only greater than 1.0 when Re > 2500 which is the design objective of reducing the pumping power and heat transfer area in the channel. Nonetheless, the screen insert is only beneficial to augment the convective heat transfer in the channel over the range of transition Reynolds number tested. The average total pressure drop across the channel and average exit air temperature suggest that the screen insert promotes good mixing of fluid across the channel for the Reynolds numbers tested.

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References

Figures

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Fig. 3

(a) Image of the actual sinusoidal air-filter screen and schematic of the screen sinusoid in YZ-plane (X: mean flow direction), and (b) approximate geometry of screen mesh (dimensions in mm) and screen placement in test channel

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Fig. 2

(a) Plane view of thermocouple tip locations along test plate (dimensions in mm) and (b) elevation view of thermocouple tip locations in test plate

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Fig. 1

(a) Schematic of test stand elevation view, (b) test section geometry, and (c) test section wall heater arrangement (drawn not to scale)

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Fig. 4

(a) Normalized wall static pressure drop along test section with and without screen versus normalized distance and (b) friction factor ratio versus Reynolds number

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Fig. 7

Nusselt numbers for one wall heated: (a) and (b) local Nu and Nu/Nu0 along X/L, (c) streamwise-averaged Nu/Nu0 along Y/W, and (d)–(f) globally averaged Nu and Nu/Nu0 as dependent upon Re and f/f0 (Re = 1360–3800)

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Fig. 5

(a) Contours of normalized local total pressure, ΔP0* at Re = 1670 and (b) pitch-averaged normalized total pressure, ΔP0* along height (Z/H) in exit plane (X/L = 1.02) of screen test section

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Fig. 6

Nusselt numbers for two heated walls: (a) and (b) local Nu and Nu/Nu0 along X/L, (c) streamwise-averaged Nu/Nu0 along Y/W, and (d)–(f) globally averaged Nu and Nu/Nu0 as dependent upon Re and f/f0 (Re = 1360–3800)

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Fig. 8

The performance index: (a) (Nu/Nu0)/(f/f0)(1/3) and (b) (Nu/Nu0)/(f/f0) of the screen test section as dependent upon Re for two heated walls and one heated wall

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Fig. 9

Pitch-averaged normalized air temperature, ΔTa* along height (Z/H) at exit plane of screen test section with two walls heated

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