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Research Papers: Natural and Mixed Convection

Underhood Buoyancy Driven Flow—An Experimental Study

[+] Author and Article Information
Parviz Merati

Department of Mechanical and Aeronautical Engineering, Western Michigan University, 4601 Campus Drive, Kalamazoo, MI 49008-5343parviz.merati@wmich.edu

Charles Davis

 MAC Engineering and Equipment Company, 2775 Meadowbrook Road, Benton Harbor, MI 49002cdavis@mac-eng.com

K.-H. Chen

 General Motors Corporation, 30500 Mound Road, MC: 480-106-256 Warren, MI 48090kuo-huey.chen@gm.com

J. P. Johnson

 General Motors Corporation, 16732 Warwick, Detroit, MI 48219jbjohnson68@sbcglobal.net

J. Heat Transfer 133(8), 082502 (May 04, 2011) (9 pages) doi:10.1115/1.4003758 History: Received May 07, 2010; Revised March 03, 2011; Published May 04, 2011; Online May 04, 2011

Particle image velocimetry and thermal measurements using thermocouples are used to measure the buoyant flow of a simplified full-scale model of an engine compartment. The engine block surface temperature and exhaust heaters are kept at about 100 and 600°C, respectively. Thermal measurements include enclosure surface temperature, temperature difference on the enclosure wall at midplane, engine block temperatures, and air temperatures under the hood. The highest surface temperatures were concentrated near the top of the enclosure around the exhaust heaters. This effect was due primarily to radiation from the exhaust heaters. Highest measured air temperature was about 300°C immediately above the right exhaust heater. The measured dominant flow structures are two larger counter rotating vortices over the top right side of the engine block and two counter rotating vortices over the top left side. These flow structures weaken considerably during the first 35 min of the transient cool down of the engine block and the exhaust heaters. Colder ambient air is sucked into the engine compartment at the vents near the bottom of the compartment with some exiting as hot air through the top slots. The time scale of the fluid exchange at the vents is in the order of seconds, indicating that this process is occurring very slowly.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Pro-E model and actual enclosure

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Figure 2

General dimensions of underhood environment (inches)

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Figure 3

Thermocouple access holes for air temperature measurement

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Figure 4

Arrangement of thermocouples for air temperature measurement at vents and slots

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Figure 5

Experimental setup of PIV

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Figure 6

Contours for enclosure surface temperature

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Figure 7

Thermocouple location for midplane temperature measurement

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Figure 8

Enclosure inside and outside temperatures at midplane; ΔT is the temperature difference between inside and outside temperatures at midplane

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Figure 9

Profile of air temperature for the probes under the hood

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Figure 10

Profile of air temperature at vents and slots

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Figure 11

Velocity magnitude contours and stream traces at X=317 mm, X=444 mm, and X=571 mm

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Figure 12

Volumetric flow rate for the front and back slots

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Figure 13

Transient air temperatures at slots: (a) front slot and (b) back slot

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Figure 14

Instantaneous flow field for transient cool down: (a) t=0 and (b) t=35 min

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