Given: a building with 20 mm thick Radiata Pine siding exposed to a heat flux of 20 kW/m 2 from an adjacent pool fire.
Calculate the time to ignition using:
Mikkola and Wichman
Tewarson
Quintiere and Harkleroad
Janssens
Toal, Silcock, and Shields
Calculation Procedure
The data used in this example are taken from the discussion above for each method.
(A) MIKKOLA AND WICHMAN (THERMALLY THICK)
| k ? c | = 0.221 kW 2 s/m 4 K 2 |
| T ig | = 340 C |
| | = 9.1 kW/m 2 |
(B) TEWARSON
| TRP | = 121 kW s 1/2 |
| | = 13.5 kW/m 2 |
(C) QUINTIERE AND HARKLEROAD
| | = 13.5 kW/m 2 |
| b | = 0.064 s 1/2 |
(D) JANSSENS
| k ? c | = 0.189 kW 2 s/m 4 K 2 |
| h ig | = 0.0275 kW/m 2 C |
| | = 10 kW/m 2 |
(E) SILCOCK AND SHIELDS
| FTP | = 2920 |
| | = 12.0 kW/m 2 |
| n | = 1.5 |
| Time to Ignition Calculation Method | Time to Ignition (s) |
|---|---|
| Experiment | 134 |
| Mikkola and Wichman | 150 |
| Tewarson | 272 |
| Quintiere and Harkleroad | 103 |
| Janssens | 141 |
| Toal, Silcock, and Shields | 129 |
The results show good agreement with the exception of Tewarson's correlation. Tewarson's method has trouble with this particular data set because his correlation requires that the linear regression pass through the origin, i.e., as 
then t ig ?1/2 ? 0. For this fuel, Tewarson's technique causes significant overprediction as 
. The factor of 2 overprediction is not unexpected for...
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