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TECHNICAL PAPERS: Experimental Techniques

Quantitative Salt-Water Modeling of Fire-Induced Flows for Convective Heat Transfer Model Development

[+] Author and Article Information
Xiaobo Yao

Department of Fire Protection Engineering, University of Maryland, College Park, MD, 20742-3031

André W. Marshall1

Department of Fire Protection Engineering, University of Maryland, College Park, MD, 20742-3031awmarsh@eng.umd.edu

1

Corresponding author.

J. Heat Transfer 129(10), 1373-1383 (Feb 23, 2007) (11 pages) doi:10.1115/1.2754943 History: Received July 02, 2006; Revised February 23, 2007

This research provides a detailed analysis of convective heat transfer in ceiling jets by using a quantitative salt-water modeling technique. The methodology of quantitative salt-water modeling builds on the analogy between salt-water flow and fire induced flow, which has been successfully used in the qualitative analysis of fires. Planar laser induced fluorescence and laser doppler velocimetry have been implemented to measure the dimensionless density difference and velocity in salt-water plumes. The quantitative salt-water modeling technique has been validated through comparisons of appropriately scaled salt-water measurements, fire measurements, and theory. This analogy has been exploited to develop an engineering heat transfer model for predicting heat transfer in impinging fire plumes using salt-water measurements along with the adiabatic wall modeling concept. Combining quantitative salt-water modeling and adiabatic wall modeling concepts introduces new opportunities for studying heat transfer issues in basic and complex fire induced flow configurations.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of plume and ceiling jet flow for an unconfined ceiling: I, plume region; II, turning region; and III, ceiling jet region

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Figure 2

Quantitative salt-water modeling facility with PLIF/LDV diagnostics; impinging plume configuration shown

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Figure 3

(a) Instantaneous and (b) mean PLIF images of dimensionless density difference θsw

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Figure 4

Dimensionless characteristic density along plume centerline: (a) mean profile, θ¯c. (b) Mean profile, (u¯3)c∕(gD*)1∕2; (◇) McCaffrey’s plume (22) salt-water model. (▵) case 1; (◻) case 2; (엯) case 3: (—) theory (23).

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Figure 5

Adiabatic wall heat transfer model

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Figure 6

Distribution of effectiveness η along ceiling: (∎) Salt water measurements for case 1; (엯) Veldman (15); (—) curve of Eq. 10.

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Figure 7

Velocity similarity profile in the ceiling jet layer

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Figure 8

Scaling laws of distribution of source independent velocity and maximum velocity position. (a) (u¯1*)max; (◻) salt-water model; (—) curve of Eq. 17 with c1=0.727, α=0.878. (b) δ1∕H; (◻) salt-water model; (—) curve of Eq. 16 with c2=0.038. (c) Similarity function of f(χ) in boundary layer; (◻) salt-water model; (—) curve of Eq. 15 with n=5.707.

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Figure 9

Heat transfer coefficient along ceiling: (—) Eq. 23 curve for test 1 of Veldman (15). (—) Eq. 23 curve for test 2 of Veldman Cf=0.024; (---), Alpert’s correlation (13); (∎) experiments of Veldman (15) for test 1, H=0.813m, Q=1.17kW. (▵) experiments of Veldmann (15) for test 2, H=0.584m, Q=1.17kW(8).

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Figure 10

(a) Heat transfer rate along ceiling radial position between the model and You and Faeth’s experiments (16); (◻) Q=0.385kW, Hf∕Hc=0.15; (▵) Q=0.24kW, Hf∕Hc=0.08(9). (– –) author’s model with Qc=Q. (—) author’s model with Qc=0.8Q. (b) Heat transfer rate along ceiling radial position between the model and experiments of Veldman (15) for test 1, Q=1.17kW, Hc=0.813m; (◻) t=1min, (▵) t=2min; (◇) t=3min; (▷) t=5min(8). (—) authors’ model predictions sorted with color.

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Figure 11

Comparison of different heat transfer model with You and Faeth’s (16) experiment. (◻) You and Faeth’s (16) experiment (16) of Q=0.24kW, Hf∕Hc=0.08(9); (– –) You and Faeth’s correlation (16); (—-—) Cooper’s model (17) with Qc=0.8Q(12); (—) author’s model with Qc=0.8Q.

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