I don't know the precise number of joules per se, but the tanks would've contained vapor emissions from the fuel itself, particularly as one of the tanks was said to be leaking before the event. An increase in pressure would've excited the already-volatile contents within, resulting in the blast.

Coincidentally, this is the same principle of science that helped N.C. Wyeth, Jr. play a major role in the beverage industry.

no, i'm not interested in the enthalpy, just the temperature and pressure. i can use those to calculate whether or not a jet through a pinhole leak would increase in temperature or decrease in temperature. the effect depends on the initial state of the gas. punctures in cold hydrogen tanks, for example, can be very dangerous because the throttling through a pinhole will increase the gas temperature above its flash point and cause an explosion. i wondered what the conditions would need to be for a similar effect to occur with the gas-phase portion of these stored fuels. i highly doubt this is what caused the explosion, but i'm interested in doing some analysis anyway, just to sort of rule that out.

petrol go boom. what more do you need to know?

If the tank(s) were leaking, the fire/explosion started outside. Normal vapor fire. Get the tank hot enough and you get a BLVE - Boiling Liquid Vapor Explosion. As the exterior fire heated the tank, the heat transfer (mostly by infrared radiation) would increase the pressure in the tank, speeding up the leak, heating the tank faster, until the tank ruptured and the expanding cloud of vapor mixed with the atmosphere and burst into flame. Throw a can of spray laquer into the fire and try it for yourself. Spectacular, but not related to heat transfer by expansion.

BTW, liquid hydrogen leaks usually explode not because the gas heats itself to the ignition point but because it generates a static charge that causes a spark and hydrogen is (oh the huge man titty!) pretty damn flammable and easy to ignite. It's not the depressurization, it's the charge separation as each droplet detaches from the vessel that creates the charged cloud. Like in the Kelvin water-dropper electrostatic generator.

≡ Click to see image ≡ ≡ Click to see image ≡
Kelvin and Hobbes

warbaby, that's right but wrong. a discharge is not necessary to cause a fire in such circumstances, because the inversion temperature of H2 is very low, such that under liquified conditions, the free expansion will cause the temperature to rise above the flash point. please consider:

(1) free expansion takes place at constant enthalpy
(2) we construct a hypothetical reversible path to derscribe the expansion. along that path,

[dH]=0=TdS +VdP

so increase in entropy due to throttling is accompanied by the decrease in pressure. Use temp and pressure as the dependent variables. We write
[dS] = (dS/dT)@P x dT+ (dS/dP)@T x dP,
where the quantities in parentheses are partials, and the at sign indicates holding the following variable constant during the differentiation.
So,
(3)
[dH]=0=C@P x dT +(V-T(dV/dT)@P) x dP,
where C@P is the heat capacity at constant pressure (and number. all of this should be implicity w/ number held constant).

this is succinctly expressed as

(4)
dT = (dT/dP)@H dP

where the quantity (dT/dP)@H is the Joule Kelvin coefficient, defined as

(1/C@P) x (T (dV/dT)@P -V)


(5) For a Van der Waals equation of state, this obtains

(dT/dP)@H = (1/R) [(2a/RT)(v-b)^2(1/v)^2 - b]/ [(5/2) - (3a/RTv) (v-b)^2/v^2]

So I want to know the tempearture of the vapor phase in these storage temperatures so I can figure out if the damn thing will explode due to the J-K effect.

I agree that ignition of the hydrogen gas escaping from a liquid tank can often be caused by an electrostatic discharge. But given certain initial circumstances, that is not necessary to cause an explosion.


what's the water dropper generator?

also
"
the heat transfer (mostly by infrared radiation)
"

what the donics? dude this is totally going to be a situation where the heat flow from outside a big tank into a big tank is principally via conduction and convection. metal tanks are mostly opaque to infrared, i think. shit, glass is*. am i missing something here?

*the reason your car gets hot in the sun is because it's an infrared oven. optical wavelength light passes through glass, which is transparent to those wavelengths. it hits the materials inside the car and is partly reflected (w/ corresponding Brillouin and Rayleigh shifting, I believe) and partly absorbed. Spontaneous emission will cause re-radiation at a different wavelength. The car materials will eventually reach a steady state where they emit as much energy as they absorb. The temperature at which they do so will determine the peak of the Planck distribution. Most of the re-radiated light will be in the infra-red regime, and most optical glass is reflective to long-wavelength infrared. Thus, those long wavelength photons will be trapped in the car, which will heat up as it has basically become an infrared boltzman/planck type oven thingy.

≡ Click to see image ≡
Kelvin water dropper

Heat transfer in fire is mostly by radiation. The flame is the hot thing and air is not a good conductor; the heated surface is not in contact with hot gasses, so neither conduction nor convection are large compared to radiation. Inside the tank is another thing, but the fire isn't inside the tank.

This is why areas in refineries that pose huge BLVE risks have water monitors to cool down the tanks during a fire.

I don't think you are using "flash point" in the correct sense. The phrase you are looking for is "ignition point" and that's a totally different thing.

The hydrogen in refineries is gaseous, not liquid anyway. The hydrogen lines are very scary because they always leak and the leaks are surrounded by blue flames. I was told the hydrogen fires are ignited by some sort of catalytic reaction, but what do refinery engineers know?

The place that exploded was not a refinery, it was a storage facility, so I'm way off topic anyway.

Most of my experience was in butane unloading and propane loading (I did a six month analysis of a loading facility during a debottlenecking.) The propane cars experience an initial cooling during loading due to expansion/evaporation, but it is minor and transitory. As soon as the car pressurizes, the temperature equalizes. Oddly, most of the operators didn't think this happened, but none of them ever checked the thermometers except before loading and at the end when the cars were full (they had to write these temperatures down.)

car = railroad tank car

So I want to know the tempearture of the vapor phase in these storage temperatures so I can figure out if the damn thing will explode due to the J-K effect.

The short answer is no. The J-K effect only produces cooling. Compressive heating is something entirely different. But neither applies to this situation. Why is left as an exercise for the reader.

The long answer can be found above.

that's not right. on the other side of the inversion temp, jk effect heats free expanding gases. cf proof above. you're definitely right about the vocab, though; it's ignition point that i'm lookin for.

I'll be damned. I didn't know about the J-T coefficient. That would explain the hydrogen flames around the flanges in the hydrogen lines.

Its critical coefficient is really the Heat Capacity of the gas (I'm not sure if vapors act as gasses in this situation); so rather than strutting your differential calculus (which I don't think you understand fully or this question wouldn't have arisen) without defining the terms (naughty), you should probably consider the relationship between Heat Capacity and molecular weights (which is not linear, but is approximately monotonic increasing with the rare exception).

Higher molecular weights, higher heat capacity, more energy needed to change the temperature (all other things being equal.) Big molecules don't heat up on expansion: It obviously doesn't apply to petroleum distillates or their vapors (which suggests their coefficient is postitive), so the short answer is still no.

Furthermore, the pressure differential across the orifice has to be higher than the static pressure of a few tens of feet of liquid, eh? So the short answer is still no.

As an aside to damn near everybody else who has wandered into this otherwise boring thread, the whole purpose of scientific knowledge is to make the laws of nature comprehensible. That's obviously not happening here...

The best illustration of making Nature's laws manifest I ever had was an off-hand comment by Dick Davidson, a physics lecturer at the U of Washington and old Manhatten Project hand (he did most of the instrumentation for Seth Nedermyer's implosion group and was one of the critical people who made plutonium implosion possible.) Hardcore pacifist (like many of the people who came out of the Project) and one of the smartest and most wonderful people I've ever know.

Dick and I were working on an exhibit on magnetism. The only ground rule was that we had to teach principles of magnetism by demonstration apparatus that was safe for children to operate and had no text -- the machine taught the physical principle directly through exploration and manipulation.

One day, Dick made the casual comment "All other things being equal, the strength of an electromagnet is directly proportional to the mass of the copper in the windings." It was like getting hit on the head by a Zen master or struck by lightning or falling in love at first sight.

Ampere-turns, wire gauges, voltages, everything else fell away like scales from my eyes. One turn of fat wire was exactly the same as a bazillion turns of skinny wire. The wire gauge only determined the operating voltage and did so in a simple and straightforward linear relationship. The critical distinction, the difference that made a difference was the dance of electrons through the mass of copper -- it's all about the number of atoms! Get it? Kazam!

Reproducing that AHA! moment is the essence of making the wonder of Nature manifest. That's what it's all about.

All the math, all the theoretical language, all the complexity -- that only gets in the way. The real essence of scientific knowledge can be passed on in extremely simple terms, if you do it right.

A light comes on, doors open, you get a little closer to the Creation (whatever the fuck that was.)

So endeth the lesson.

"
(I'm not sure if vapors act as gasses in this situation); so rather than strutting your differential calculus (which I don't think you understand fully or this question wouldn't have arisen) without defining the terms (naughty), you should probably consider the relationship between Heat Capacity and molecular weights (which is not linear, but is approximately monotonic increasing with the rare exception).
"

holy shit. do you know that you're being condescending? you must be a Very Important Professor.
you'll find the heat capacity at constant pressure in my definition point (4), thank you. The actual J_K coefficient is simply the heat capacity at constant enthalpy, since, if you want a simple, straightfoward pov, we're considering a free expansion at constant enthalpy. and we want to know what happens to the entropy. the end!

"

So endeth the lesson.
"

indeed. you're welcome.

Nah, I'm being a snide / snarky old fart who can't sleep at night. Older than Quansar, so have a little respect for my grey hairs and approaching senility. No offense, you callow youth.

But it took me a while to decode the calc (it's been nearly 40 years since I took undergrad physics) and I'm pretty sure it left darn near everybody else in the dust, as seen from the numerous comments.

H = -Sigma(p sub i log p sub i)

It's an old saying among my people.

I'm quite sincere about these comments. The universe is a book the Creator wrote for us to read. The language may be obsure, but nothing is truely hidden.

/Unitarian philosophy

Which leaves us with the question: what the hell provided the initial ignition source at the storage facility?

Leaks are common at petroleum facilities, I've seen flare towers go out and shower distillate all over the place. I spent a fair amount of time analyzing flare lines at two refineries and found some major design problems management wouldn't fix because they didn't want to spend the money. The flare lines at Tesaro Anacortes can't handle gasses lighter than air because the compressor water traps work backwards when the flare density falls below atmospheric. The problem has existed since the flare compressors were built and has never been corrected.

Refineries are big bombs just waiting to go off.

If the J-T coefficent was such that any leak would spontaneously ignite, there wouldn't be a single operating refinery on the planet, just a bunch of big smoking holes in the ground.

Ignition sources are rare - but present - and the facilities are built to keep them isolated. So what did happen?