HP 42S/DM42: Height of a Fire, Time to Clear a Corridor
HP 42S/DM42/Free42 Program: FIREHGT
The program FHGT approximates the height of a fire in three scenarios:
* A relatively large fire
* A fire with a base area of approximately 0.5 meter
* A fire set in a corner
The general equation is:
H = factor * Q^0.4
H = height of a fire in meters, including the tip
factor = constant depending on the scenario the fire is set in
Q = energy release rate in kilowatts
00 {119-Byte Prgm}
01 LBL "FIREHGT"
02 "ENERGY? (kW)"
03 PROMPT
04 STO 01
05 LBL 00
06 "TYPE?"
07 AVIEW
08 "LARGE"
09 KEY 1 GTO 01
10 "0.5 M"
11 KEY 2 GTO 02
12 "CORNER"
13 KEY 3 GTO 03
14 MENU
15 LBL 10
16 STOP
17 GTO 10
18 LBL 01
19 0.23
20 GTO 04
21 LBL 02
22 0.21
23 GTO 04
24 LBL 03
25 0.075
26 GTO 04
27 LBL 04
28 CLMENU
29 EXITALL
30 RCL 01
31 0.4
32 Y↑X
33 ×
34 "HEIGHT="
35 ARCL ST X
36 AVIEW
37 END
Example:
Q = 2650 kW
large fire: H = 5.38302238231 m
0.5 m fire: H = 4.9149334795 m
corner fire: H = 1.7553338554 m
HP 42S/DM42/Free42 Program: SMOKE
The program SMOKE estimates:
* The front velocity of the smoke, or how quickly the smoke fills a corridor
* The time it takes for front velocity to fill the corridor.
Equations used:
V ≈ 0.5 * √(g * (1 - Ta/T) * H)
tf = L / Vf
g = acceleration of gravity, for Earth, g = 9.80665 m/s
Ta = ambient temperature
T = gas temperature (Ta ≤ T)
H = height of the corridor in meters
L = length of the corridor in meters
Note 1 - Ta/T = (Da - Dc) / Da
Da = density of the corridor of the ambient air
Dc = density of the fire fluid
00 {99-Byte Prgm}
01 LBL "SMOKE"
02 1
03 "AMB. TEMP?"
04 PROMPT
05 "GAS TEMP?"
06 PROMPT
07 ÷
08 -
09 9.80665
10 ×
11 "HEIGHT? (M)"
12 PROMPT
13 ×
14 SQRT
15 2
16 ÷
17 ENTER
18 "VEL= "
19 ARCL ST X
20 AVIEW
21 STOP
22 R↓
23 1/X
24 "LENGTH? (M)"
25 PROMPT
26 ×
27 "TIME="
28 ARCL ST X
29 AVIEW
30 END
Example:
Amb. Temp: 78 °F = 25.555555556 °C
Gas Temp: 103 °F = 39.44444444 °C
Height: 3.048 m
Length: 3.6576 m
Results:
Velocity: 1.622103844 m/s
Time: 2.254849474 s
Source:
Lawson, J.R. and Quintiere, J.G.. "Slide Rule Estimates of Fire Growth". Fire Technology, Vol. 21., No. 4, November 1985, pg. 267
Eddie
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