Air source heat pumps....

[Tim Streater]

Only with about 70 bar of pressure, if you want it to be liquid at 0C.

[Ghostrecon]

not Boyles law - that relates P and V noT involved lol

[Matty F]

In that case CO2 would appear to be a much better choice for a refrigerant than air. I'd better recycle the CO2 then. Can't have that nasty CO2 escaping and causing Catastrophic Global Warming can we :)

[dennis]

So which one is PV/T = constant then?

[dennis]

Would that be natural CO2 or the nasty manmade stuff. Then there is the in between stuff I have been making by burning that nasty natural methane to make CO2 which is a much less powerful greenhouse gas.

[Tim Streater]

I doubt it. Above about 27C, CO2 is a gas whatever pressure you apply to it.

[The Natural Philosopher]

Dont worry dennis' pretty little head over actual facts.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Matty F saying something like:

By arranging a bank of fridge/freezer guts to do the job.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember harry saying something like:

Not a single system- several unmolested systems arranged in parallel. I've observed that many fridge and/or freezer systems can be removed from the cabinets in one piece and pressed to another use; either as an air/air exchanger or even heating a water trough.

[Matty F]

I'm concerned only about heating my house in winter.

27C would be uncomfortably hot so my CO2 would never reach that temperature.

[Matty F]

I had thought of using old fridge units. But I think I would need about ten of them to heat my house. That's getting a bit clumsy.

[Matty F]

You mentioned 27C. At what point in the cycle would the refrigerant reach 27C?

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember harry saying something like:

If it's enclosed neatly and I have room (which I have plenty of), no problem.

[Nick Leverton]

Not rubbish, even if not exactly true either. Above the critical temperature (31.1C in fact), CO2 will never liquify, it will at best be a supercritical fluid, neither liquid nor gas. Fire extinguishers have to be pressure rated to cope with supercritical CO2 at - judging from the following diagram - up to about 50 Celcius:

less legibly, from