- Author
-
Persson, B.
|
Tuovinen, H.
|
Holmstedt, G.
- Title
- CFD Simulations With Reference to Smoke Detector Response.
- Coporate
- Swedish National Testing Institute, Boras, Sweden
Lund Univ., Sweden
- Report
-
SP REPORT 1995:46; BRANDFORSK Project 622-921,
1995,
28 p.
- Keywords
-
smoke detectors
|
detector response
|
simulation
|
optical density
|
smoke movement
|
ceilings
|
response time
|
smoke spread
|
xylene
|
mass optical density
- Identifiers
- Computational Fluid Dynamics (CFD); JASMINE; boundary conditions; influence of a suspended ceiling on the response times; smoke spread in a narrow corridor
- Abstract
- CFD simulations have been carried out to investigate the effect of a porous suspended ceiling on the response of smoke detectors. The problem has bearing on the optimum location of detectors in a large industrial hall. For the examined porosities the results show that the best overall location of detectors is above the suspended ceiling although the suspended ceiling deflects the smoke at low porosities and delays the response in an area close to the fire source. It is also found that the porous ceiling acts like a smoke trap. Once the smoke has entered the space above the suspended ceiling, the whole space must be filled up before the smoke can re-enter through the ceiling. Simulations have also been performed of smoke spread in a long corridor to investigate the possibility of predicting the optical density based on simple engineering models. In the model investigated it is assumed that the optical density is directly proportional to the local mass franction of combustion products. By comparing the calculations with experimental results the proportionality constant has been determined for three different fuels, methanol, heptane and xylene. Although the constants show a variation that is qualitatively correct between the different fuels it seems difficult to correlate the results with handbook data of measured mass optical density or smoke yield. It is concluded that CFD can very well be used in investigating optimal locations of smoke detectors although more work is needed in devloping suitable theoretical models for detector response and for models predicting smoke properties such as optical density.