Transient Ceiling Jet Temperature and Velocity Profiles in the Presence of an Upper Layer: Comparison with Predictions by LAVENT and JET Computer Fire Models

Abstract

Results of a scaled experimental study are compared with the predictions produced by the LAVENT and JET computer fire models. As in most large-scale fire testing, characterization of heat release rate (HRR) and accuracy of its measurement creates a lot of uncertainty for validation of these codes. Sensitivity of LAVENT results to the assumed radiative loss of 35% is examined by varying the total HRR which corresponds to varying the convective HRR. Comparisons show that LAVENT uses the wall-jet theory at its core for prediction of the ceiling jet flow and thus does not capture the ceiling jet profile well and overpredicts the upper layer temperature during the development of the layer. The velocity is generally overpredicted since the retardation of the jet momentum by the upper layer does not seem to be modeled accurately. JET has a better user interface and slightly different parameters, but does not provide ceiling jet profiles. The major difference between JET and LAVENT include the ceiling jet temperature and velocity algorithms, the fusible link algorithms, and the use of a variable radiative fraction as a function of fire size and type.

Keywords

ceiling jet temperature velocity profile fire model LAVENT JET heat release rate radiative loss convective.

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References

Brozovsky, E. , Motevalli, V. and Custer, R.L.P. (1995). A Preliminary Approach for Smoke Detector Placement Based on Design Fire Size and Detector Aerosol Entry Lag-time, Journal of Fire Technology, 31(4): 336—354.

Cooper, L.Y. (1990). Estimating the Environment and the Response of Sprinkler Links in Compartment Fires with Draft Curtains and Fusible Link-Actuated Ceiling Vents Theory, Fire Safety Journal, 16: 132—163.

Davis, W.D. and Cooper, L.Y. (1989). Estimating the Environment and the Response of Sprinkler Links in Compartment Fires with Draft Curtains and Fusible-Link-Actuated Ceiling Vents-Part II: User Guide for the Computer Code LAVENT, Nat'l Institute of Standards and Technology, Report No. NISTIR 89-4122.

Davis, W.D. and Cooper, L.Y. (1991). A Computer Model for Estimating the Environment and the Response of Sprinkler Links in Compartment Fires with Draft Curtains and Fusible-Link-Actuated Ceiling Vents, Fire Technology, 27(2): 113—127.

Davis, W.D. (1991). The Zone Fire Model Jet: A Model for the Prediction of Detector Activation and Gas Temperature in the Presence of a Smoke Layer, Nat'l Institute of Standards and Technology, Report No. NISTIR 6324.

Motevalli, V. (1989). Transient Characteristics of Unconfined Fire-Plume-Driven Ceiling Jets, Ph.D.Dissertation, University of Maryland .

Alpert, R.L. (1972). Calculations of Response Times of Ceiling Mounted Fire Detectors, Fire Technology, 8: 181—189.

Heskestad, G. and Delichatsios, M.A. (1978). 17th Symp. (Int'l) on Comb., pp. 1113—1123.

Cooper, L.Y. (1982). Heat Transfer from a Buoyant Plume to an Unconfined Ceiling, Journal of Heat Transfer, 104: 446—451.

10.

Motevalli, V. and Marks, C.H. (1991), 3rd Int'l Symp. on Fire Safety Sci., pp. 301—312.

11.

Evans, D.D. (1984). Calculating Fire Plume Charcteristics in a Two-Layer Environment, Fire Technology , 20(3): 39—63.

12.

Cooper, L.Y. (1984). A Buoyant Source in the Lower of Two, Homogeneous Stably Stratified Layers, 20th Symp. (Int'l) on Comb., pp. 1567—1573.

13.

Zukoski, E.E. , Kubota, T. and Cetegen, B. (1980). Estimating of Fire Plumes , Fire Safety Journal, 3: 107—121.

14.

Motevalli, V. and Ricciuti, C. (1992). Characterization of the Confined Ceiling Jet in the Presence of an Upper Layer in Transient and Steady-state Conditions, National Institute of Standards and Technology , NIST-CGR-92-613, pp. 1—134.

15.

Motevalli, V. and Marks, C.H. (1990). Transient Characteristics of Unconfined Fire-Plume-Driven Ceiling Jets, NIST, Rpt.No.NIST/ GCR-90/574.

16.

Motevalli, V. , Marks, C.H. and McCaffrey , B.J. (1992). Measurements of Velocity and Temperature Profiles in Low-Speed, Turbulent, Non-Isothermal Flows, Journal of Heat Transfer, 114(2).

17.

Cox, G. (1977). Gas Velocity Measurements in Fire by the Cross-Correlation of Random Thermal Fluctuations-A Comparison of Conventional Techniques, Combustion and Flame, 28: 155—163.

18.

Deal, S. and Beyler, C. (1991). Correlating Temperatures in Post-Flashover Room Fires, Journal of Fire Protection Engineering, 2(2): 33—48.

19.

McCaffrey, B.J. , Quintire, J.G. and Harkleroad , M.F. (1981). Estimating Room Fire Temperatures and Likelihood of Flash-over Using Fire Test Data Correlations, Journal of Fire Technology, 17(2): 98—119.

20.

Woodhouse, A. , Marks, C.H. and Cooper, L.Y. (1987). Experimental Study of the Transient Thermal Response of Unconfined Ceilings Above Fire Plumes. ASME-JSME Thermal Engineering Conference , In: Cooper, L.Y. and Farouk, B. (eds), Proceedings of Sessions on Heat and Mass Transfer in Compartment Fires, pp. 387—394.

21.

Holman, J.P. (1990). Heat Transfer, 7th edn, McGraw Hill, Corp.

22.

Veldman, C.C. , Zukoski, E.E. and Kubota, T. (1977). An Experimental Investigation of the Heat Transfer from a Buoyant Plume to a Horizontal Ceiling-Part I Unobstructed Ceiling, National Bureau of Standard, Report No. NBS-GCR 77-97.

23.

Cooper, L.Y. (1988). Ceiling Jet-Driven Wall Flows in Compartment Fires, Combustion, Science and Technology , 62: 285—296.