Re: CO2 evaporator or vaporizer

On Fri, 06 Apr 2007 17:34:16 -0500, Richard J Kinch <kinch@xxxxxxxxxxx> wrote:
Let's say you had 20 feet of 1/2" refrigeration copper tubing coiled in a
barrel of warm water for a vaporizer. Tubing volume is all of 0.018 cu ft.
Liquid to vapor expansion is about 500-to-1, so you need an initial
"spurt" of 0.000035 cu ft, or about 1 cc.

Now tell me, when you crack that valve with 300 psi liquid behind it,
feeding into 20 ft of empty tube, do you really think that 1 cc of liquid
is all that is going in?

Yes.

why? Because as evap increases the pressure, it will push back any
liquid trying to enter. It tries to push both ways, but the gaseous
regulator on the output prevents pushing that direction.

BUT, if your liquid is CO2, and your evap maintains 70F to 80F, your
system is going to be operating at 800-900psi (rough numbers, I don't
recall offhand the exact vapor pressure of CO2 at near room
temperature). That is likely a significant problem given your spec to
operate the bulk liquid CO2 tank at 300psi.

I'm thinking tiny orifice followed by a check valve. Orifice sized to pass
the liquid at 20 lbs/hour from a differential pressure of 50 or 100 psi.

Forget the tiny orifice. It is neither required nor helpful. You just
need that check valve, and it must be able to handle liquid CO2
temperature at 1200+psi operating pressure. Note that everything on the
vapor side of that check valve needs the the same or better rating.
Then for safety you also need an overpressure relief valve at under
1200psi on the vapor side. With that setup the vapor side will operate
between just under 300psi (input pressure) as a lower limit and an upper
limit of the CO2 vapor pressure at your vaporizer temperature (I'd go
for 75f and lower, can probably use the waste heat from the
refridgeration unit). Your output regulator at 100psi will be happy
with that range of input pressures and maintain your 100psi output. I
have no idea where to get a check valve with that rating.

sdb

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