[ale] [WAY OT] WARNING - diy car ac recharge kits can be dangerous

[Phil Turmel]

On 08/16/2013 11:41 AM, Ron Frazier (ALE) wrote:
> Phil,
> 
> That's some cool information you posted.  Nice website.
> 
> So, if you wanted to top off a system without vacuuming it down, for a
> given car and a given outdoor temperature, how would one determine what
> the high side and low side pressures are supposed to be?  The can I was
> using has an adjustable gauge for low side pressure correlated to
> ambient temperature, which seems fairly accurate.  But, apparently, that
> means little in regard to the level of refrigerant in the system.

See my reply to Jim.  If it was too simple, everyone would do their own.
 All the engineers I know had to take thermo in college, though.  If you
can handle that, you can handle refrigerant.

> You said r134a was unregulated for personal use.  That's not totally
> true.  The following epa faq says it's illegal to knowingly vent r134a
> to the atmosphere.
> 
> http://www.epa.gov/ozone/title6/608/faq.html

Yes, I know.  I meant "unregulated" in the sense that the government
doesn't burden the DIYer with licensing and taxes.

> I find this fascinating from a scientific point of view whether I ever
> work on my car or not.  I have had an interest in alternate energy for a
> long time.  When I get time, space, and money ... someday ... I want to
> do experiments with low temperature heat engines to use solar power or
> even ambient heat in my attic (which is, in effect, solar) or geothermal
> energy.  I would really love to be able to run an engine on a 100 degree
> F temperature delta.
> 
> http://en.wikipedia.org/wiki/Minto_wheel
> http://en.wikipedia.org/wiki/Drinking_bird
> http://en.wikipedia.org/wiki/Stirling_engine
> http://en.wikipedia.org/wiki/Ocean_Thermal_Energy_Conversion

The higher the delta T, the higher the efficiency (referenced to 0K).
Basic thermo--rankine IIRC.  100F deltaT just isn't that much.  Not that
you can't make it work, just will be relatively expensive.

Phil