Re: PBS Series: "The Carrier"

Peter Skelton wrote:
On Sat, 3 May 2008 19:29:15 -0700 (PDT), mike
<marathag@xxxxxxxxx> wrote:

On May 3, 10:23 am, "Jeff Crowell" <jeffDOTcrow...@xxxxxx> wrote:

Subjectively, it feels like the acceleration is pretty constant.
If you guesstimate track length as 300 feet (by eye, the flight deck
of the Nimitz class is about 3.5 'cat tracks' long) and endspeed of
145 knots, stroke time of 2 seconds, that comes out to 10.8Gs.
It does cage your eyeballs pretty well!

Given the volume of steam that's passing through one or two valves,
I suspect acceleration may drop off with distance traveled. Only
way I can see to avoid that would be to have more valves open
along the track as the piston proceeds on its merry way, that
way you could hold pressure nearly constant..
Thats one of the neat things about high pressure steam.

It keeps expanding-- something that multi-stage turbines
(and old compound cylinder engines) take well advantage of.
Its also why its so dangerous when its vented. A 60psi boiler
popping is far,far worse than a same size airtank pressurized
to 250psi. Even a home waterheater with a bad relief valve
can do amazing amounts of damage

A 60 psi boiler generally contains more water by mass than steam.
The water is heated above its boiling point at standard pressure,
so much of it flashes to steam greatly increasing the volume of
gas if the boiler ruptures.
Don't think so

There is not enough energy to vaporize much of it


Energy Requirements

The energy required to heat water is significantly lower than that needed to vaporize it, for example for steam distillation^[10] <http://en.wikipedia.org/wiki/Superheated_water#cite_note-9> and the energy is easier to recycle using heat exchangers. The energy requirements can be calculated from steam tables. For example, to heat water from 25°C to steam at 250°C at 1 atm requires 2869 kJ / kg. To heat water at 25°C to liquid water at 250°C at 5 MPa requires only 976 kJ / kg. It is also possible to recover much of the heat (say 75%) from superheated water, and therefore the energy use for superheated water extraction is less than one sixth needed for steam distillation. This also means that the energy contained in the superheated water is insufficient to vaporise the water on decompression. In the above example, only 30% of the water would be converted to vapour on decompression from 5 MPa to atmospheric pressure.^[2] <http://en.wikipedia.org/wiki/Superheated_water#cite_note-superheatedwater-1>


http://en.wikipedia.org/wiki/Superheated_water

Yes I know 5 Mp is about 700 psi but the principle is the same

Vince



A pressure vessel full of steam is not much more dangerous than
one full of compressed air at the same pressure, except for
thermal effects.


Peter Skelton
.

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