LN2 cooling - Was:(Re: [rescue] SCRAPPLE)

[George Adkins]

On Tuesday 13 November 2001 11:29 pm, you wrote:
> On Tuesday 13 November 2001 09:48 pm, you wrote:
> > On November 13, George Adkins wrote:
> > > > > How 'bout a LN2-based backup system?  :-)
> > > >
> > > >   Nah...won't absorb enough heat. :-(
> > >
> > > Obviously you haven't played with enough LN2... heh heh..
> >
> >   I've played with TONS of LN2...and that's about how much it would take
> > to cool a computer room. :-(
>
> Hmm, what's the heat of vaporization of N?
assuming:
-195C is the boiling point of LN2.
15C is a suitable Server Room Atmospheric temperature
5580 J/mol is the heat of vaporization of LN2

the rough mass of LN2:
28g/mol divided by 0.8 g/cm3 = 35 cm3/mol

so,
5580 J/mol divided by 35 cm3/mol = 159 J/cm3 heat of vaporization per cm3
add in:
0.8 g/cm3 times (195 + 15) degreesC = 168 J/cm3 (1J = 1 g/degreeC)

the Sum:
159 J + 168 J = 327 J/cm3 OR 408 J/gram

Hence, 1liter of Ln2 would absorb .33 Megajoules of heat before reaching 15C.