Re: shock wave as pressure builds in a vacuum?

[Brian Whatcott <betwys@SBCGLOBAL.NET>]

Roger,

Looking at the possibility of summarizing the cited text
pages 707,8,9 sensibly,  I realize it is beyond my modest powers.
So I will offer just a  paragraph or two, for the flavor:

"The entering and leaving flow must do work against the resisting
pressure of the adjoining fluid, which results in an extra energy
term pv, called the "flow work"  or transmitted energy.
The flow-work term is conveniently added to the  internal
 energy to form the property called enthalpy, h = u + pv."
....
"The internal energy of the tank after filling is equal to the enthalpy
of the atmospheric air; the flow-work of the entering air has been
converted to internal energy.   Since air at atmospheric conditions
acts as an ideal gas with constant specific heats,

.....
T = gamma  x Tinlet

Tinlet  = 70 degF = 530 degR so
T = 1.4 (530 degR) = 742 degR = 282 degF

I hope this makes at least as much sense to you as it does to me.

:-)

Brian Whatcott


At 11:58 AM 5/29/2003 -0500, I wrote this briefly, promising more:

> This is worked problem 12-12 in compressible flow:
>
> "Atmospheric air is allowed to fill an initially evacuated
> insulated bottle. What is the temperature of the air in
> the bottle when it is full?
> Assume air is at 70degF and gamma equals 1.4"
> (Answer: 282 degF)
>
> from p707-    Fluid Mechanics
> REA Problem Solvers  "A Complete Solution Guide"
> Fogiel/Cimbala ISBN 0-87891-547-8 LOC 95-70958
>
> I'll try to put some flesh on this note later this evening....
>
> Brian Whatcott    Altus OK
>
> At 09:10 AM 5/29/2003 -0700, you wrote:
> >Brian,
> >         Could you give a brief overview of the rapid
> >inrush of air into a vacuum that gives  the
> >temperature of 100K.

/snip/

> >Thanks
> >Roger Haar
> >
> >
> >Brian Whatcott wrote:
> > >
> > > At 03:52 PM 5/28/2003 -0400, Stefan Jeglinski , you wrote:
> > >
> > > Likening Stefan's situation to the classical problem of rapid inrush of
> > > room temperature air into an insulated vacuum bottle, where a temperature
> > > rise of more than 100K is expected

/snip/