Heat Transfer in Soil
Heat Transfer in Soil
(OP)
Need help finding a simple equation to calculate the cover for a pipeline to not being impacted by a forest fire aboveground.
I am assuming homogeneous soil and only 1 direction for the heat wave to travel (down).
So far I've found this one based on Fourier's law, but not sure if it can be used.
h/kA = T1-T2/Q
where:
h: depth
k: thermal coef. of soil
A: area of impact (assuming 1 square unit)
T1: Temp. above ground
T2: Temp. at the pipeline (unchanged)
Q: Thermal energy of fire
I am assuming homogeneous soil and only 1 direction for the heat wave to travel (down).
So far I've found this one based on Fourier's law, but not sure if it can be used.
h/kA = T1-T2/Q
where:
h: depth
k: thermal coef. of soil
A: area of impact (assuming 1 square unit)
T1: Temp. above ground
T2: Temp. at the pipeline (unchanged)
Q: Thermal energy of fire





RE: Heat Transfer in Soil
RE: Heat Transfer in Soil
Any other equation you may know of?
RE: Heat Transfer in Soil
But if you want to do it, look at the "overall heat transfer coefficient" equation to get the units correct.
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Heat Transfer in Soil
Back at the site after the fuel was exhausted we went back to look at the dfamage. A metal barbwire post used as a pole for an API pipeline marker that was within a few feet of the rupture was laying down and was just a melted line of metal in the hardened clay. The 11" diameter aluminum sign was just an eery silver shawdow in the clay.
The clay was solid "rock" not the stuff you normally expect. For a 100 foot radius around the fire, the ground looked like the moon. There were little mountains that stuck up about 4 inches and were about a foot in diameter. they were scattered every 8 to 10 feet. I kick one of those moun ds and a 1 to 1 1/2 " of fired clay broke off. Then the ground started to crawl as the fire ants came running out to defend their turf.
RE: Heat Transfer in Soil
THAT'S WHY THEY CALL THEM FIRE ANTS !!!
Since the hottest part of the fire is not at the bottom of the flame and the gasous interface between the fire atmosphere and soil prevents effective conduction into the ground, little heat is transferred to the soil. Even if you throw gasoline on it. The only real means of heat transfer available is radiation, which is not nearly as effective as conduction. Most of the fireball and the heat it has within it goes up. Relatively little heat goes down. As decasto says, radiation can be effective and will warm the upper 1" of soil, but not really that much. Its even common for pine cones, either still in the tree or lying on the ground, not to be burned by a typically fast travelling forest fire. The pine cones open at first rain and release seeds to get the forest restarted straight away.
There are a lot of ranchers that would gladly burn their grasses using gasoline, if only the fire would get rid of those ants. The liquid gasoline itself would probably only kill a handfull of them by chemical contact.
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Heat Transfer in Soil
A shape factor for a long isothermal pipe buried beneath an isothermal surface is given in:
See table 1 of
http:
RE: Heat Transfer in Soil
Pipeliner- as mentioned, Q is heat transfer rate, not thermal energy, its units are Btu/hr. Use h in ft, k in Btu/(hr*ft*F) A in ft^2 T in (F). In these units the equation balances.
I am assuming you need to convince or prove to someone that your cover depth is adequate to withstand a forest fire. I would do that by estimating what the heat transfer rate would be at your standard depth, for an estimated duration of a fire event and making some assumptions on where that heat will go once it reaches the pipe.
RE: Heat Transfer in Soil
(1.5W/m-K)*1200°C/2ft = 2952 W/m^2
diatomaceous earth is listed as 0.06055 W/m-K
TTFN
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RE: Heat Transfer in Soil
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Heat Transfer in Soil
RE: Heat Transfer in Soil
OK. Have fun. Watch them rat'lers.
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Heat Transfer in Soil
and of course the ...
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/