- Author
-
Pietrzak, L. M.
- Title
- Improvements to the Water Vaporization and Surface Cooling Calculations in the Fire Demand Model.
- Coporate
- Toyon Research Corp., Goleta, CA
- Sponsor
- Technical Research Center of Finland Fire Technology Laboratory, Espoo
Swedish Fire Research Board, Stockholm, Sweden
- Report
-
196C0100; Project 6-196,
December 1993,
75 p.
- Keywords
-
water
|
vaporization
|
surface cooling
|
fire suppression
|
solid fuels
|
fuel fires
|
compartments
|
water sprays
|
fire hoses
|
nozzles
|
fire departments
|
flow rate
|
drop sizes
|
combustion products
|
venting
|
room fires
|
equations
|
experiments
|
smothering
- Identifiers
- modifications to the fire demand model; Fire Demand Model (FDM); modifications to the gaseous cooling and water partitioning calculations; modifications to the wall/ceiling surface cooling calculations
- Abstract
- The Swedish Fire Research Board has been supporting the development of a computerized Fire Demand Model (FDM) which simulates the suppression of post-flashover charring and non-charring solid fuel fires in compartments using water sprays from portable hose-nozzle equipment used by fire departments. The output of this FDM shows the extinguishing effects of hose-nozzle systems emitting water spray at various flow rates and droplet sixes. The calculations are based on a heat and mass balance accounting for gas and surface cooling, steam-induced smothering, direct estinguishment of the fuel and water spray induced air inflow and venting of heat and products of combustion. As part of this effort, the VTT Fire Technology Laboratory at the Technical Research Center of Finland conducted several full-scale fire suppression tests. These tests were carried out in a test configuration simulating a significant portion of a building room. The test series involved fully involved room fires which were allowed to bum for several minutes. Measurements were made of room conditions prior to and during manual fire suppression using water hose streams. Based on these tests, as well as tests completed earlier at the National Institute of Standards and Technology in the United States, modifications were made to the FDM. The report includes a description of these modifications including theory and equations. It is shown that the new model incorporates more details on droplet dynamics and water partitioning in the gas phase cooling and vaporization calculations. It also includes improvements in the wall/ceiling surface cooling calculations. The report also compares FDM predictions to the VTT experiments. It is shown that the new model better accounts for suppression effects in all regimes but particularly for very small droplet characteristic of high pressure fog equipment. The report also shows that the temperature-time histories and quantities of water predicted by the modified model compare favorably with the experimental results. Finally an analysis using the modified model shows significant sensitivities to the water spray parameters, temperature control criteria, and water-exposed fuel fraction. Recommendations for further model development are also provided.