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dom253 (Mechanical) (OP)
29 Nov 11 14:00
Can anybody enlighten me please!!!!!!   How much air cooling is possible through a convergence divergence nozzle.  I am trying to cool compressed air from 35 Deg C to around 5 Deg C. Is this possible through a CD nozzle with an air flow of around 50 LPM and a pressure of 5 barg.  I have a pressure reduction of around 0.5 barg.  I realise adiabatic expansion will give me a temp reduction, but would this be enough, given my conditions.  Are there more efficient ways of cooling air.  I have heard of the vortex tube but I have too much back pressure for that to work.  I have no power to run cooling fans or utilise heat pipes etc.   
MiketheEngineer (Structural)
29 Nov 11 15:17
There are companies that sell these.  Call them
dom253 (Mechanical) (OP)
30 Nov 11 2:47
My apologies for double posting.  I didn't realise it was a no no.  So btrueblood you think its possible to cool to 5 deg c with a CD nozzle then.  That is interesting.  That seems a lot of cooling with a dp of only 0.5 barg.  Time to get one in and run some test then I feel
Latexman (Chemical)
30 Nov 11 7:43
If you assume an isentropic flow process and pull out your old Thermo book, I think you'll find this small pressure reduction will not get the air to 5o C.  I calculate 27.4o C.

Good luck,
Latexman

dom253 (Mechanical) (OP)
30 Nov 11 7:48
Thanks Latexman.  I don't have a thermo book.  What formulae did you use to give you 27.4 Deg?   
Latexman (Chemical)
30 Nov 11 8:23
At http://en.wikipedia.org/wiki/Isentropic_process the second formula under the section titled "Table of isentropic relations for an ideal gas".

Good luck,
Latexman

dom253 (Mechanical) (OP)
30 Nov 11 12:32
Great input guys thanks.  I'm going to look into CD nozzles a bit more, and think about maintaining the temp drop as much as possible.  I'm thinking of combining two or more techniques to try and reduce the air temperature.  I'm hoping strategic use of cooling fins might yield positive resuls.  I might be able to utilise a small amount of convection if i'm clever!!   

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