A tank with a 25.5 litre capacity contains air compressed into 355 atmospheres used to drive a torpedo by expansion into an engine via a pipe of diameter 0.08cm. A mechanism ensures that the gas flows to the engine at a constant rate and any cooling of the air during expansion to the 1 atmosphere pressure in the pipe can be neglected.
If the engine is driven by the air for 12.0 minutes until the tank is empty, at what speed does the air flow in the pipe?
P1/p = P2/p + V"/2 which produces V"2 = square root of ((P1 - P2)/p x 2
The Attempt at a Solution
I'm not sure whether it's a mixture of thermal dynamics and thermal effects in gases. I don't know whether to bring in Pascals law or the pressure / temperature / density relationship and gas properties / heat capacities? I did alot of reading into Intro to fluid dynamics by Stanley Middleman - that's where I also worked out a mach number of 1.4 from for the air.
My scenario is abit different than the ones I've read on here / in the books. The Stanley Middleman book at pg 479 doesn't actually give an answer to the air speed - it starts talking about entropy and all sorts of other things I'm not sure are relevant?
I just want to know the airflow speed for 25.5litres of compressed air to 355 atmospheres which takes 12 minutes to empty through a 0.08cm diameter pipe?! Why is it so hard to relate it all?
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