Autocascade: first refrigerant

[floshey]

So, i have been thinking for the last few days, and off course been watching the pioneers on the AC field, berkut, JSU, kayl, jan(did i forget someone? sorry if i did)

So you guys are using mostly R290 / R744 and with good results too, but why not try with original cascade refrigerants like R1150 as the high pressure refrigerant.

I know we have to get the HX to around -35º before the pressure isn't insane, but wouldnt that be doable?

I have been searching for a refrigerant that could act as the first stage refrigerant in an Autocascade, and for me the best choice looks like Propene C3H6, which has a boiling point of -47.8ºC, and it is a pure refrigerant. It needs around 35ºC to condense@247PSI/17Bar.

So guys, are we going to see Ethylene Autocascades in the near future, or what?

Just some thoughts from overhere, and i want to thank all you guys that are experimenting with the Autocascades and pass on your knowledge, im deeply grateful :toast:
http://www.airliquide.com/en/business/products/gases/gasdata/images/VaporPressureGraph/Propylene_Vapor_Pressure.GIF
P/T Chart of Propene.

[Russell_hq]

The reason that they are using CO2 is that they all have easy access to it. So when they build they are comparing like with like and makes for a better competition. I've always wanted to have a shot with propene on the first stage but never been able to get my hands on it. I know that bernzomatic do it in a cylinder for their blowtorches but I've never found it over here in the UK (I think they have stopped it now, I couldnt find it on their website).

[gkiing]

Just wondered.. anyone know what MAPP gas/brazing gas is?

[wr0x2]

I think MAPP is lower pressure than R290, so it probably wouldn't be as good a refrigerant. (R290 is C3H8 btw, not C3H6.)

[Pandrone]

Just wondered.. anyone know what MAPP gas/brazing gas is?


Check here :http://www.corpbrothers.com/productcgc/mapp.htm

[gkiing]

I think MAPP is lower pressure than R290, so it probably wouldn't be as good a refrigerant. (R290 is C3H8 btw, not C3H6.)

They were referring to propene not propane

[floshey]

And just for the record, when analyzing R290 vs R22, i can't think of a reason to use R22 over R290 (besides flammability). Or what? Am i looking at the wrong data?

R22
boiling point -40.8º
Latent heat of vaporization 233.95 kJ/kg
Critical temperature : 96 °C
Critical pressure : 49.36 bar

R290
boiling point -42.1º
Latent heat of vaporization 425.31 kJ/kg
Critical temperature : 96.6 °C
Critical pressure : 42.5 bar

[pythagoras]

Your just missing a small factor ;) R22 has a greater capacity than R290. The latent heat of evaporation is what is throwing you off here. R290 appears much greater until you factor in the density difference between R22 and R290. Molar weight of R22 is 86.48 R290 is 44.096. Therefore for a given time period R22 will remove (86.48/44.096)*233.95Kj=458.82Kj whilst

R290 will remove 425Kj.

I think :confused: :confused:

Regards

John.

[gkiing]

I'm not sure about heat capacity but I know R22 will run colder in these small systems.

[Russell_hq]

I would rather go on latent heat per m3
At 1 atm saturated conditions.

R290 = 92,930 kJ/m3
R22 = 122,522 kJ/m3

this gives it approx. 32% more capacity at atm. pressure

[pythagoras]

Thanks Russell ;)

I hope your going to get back into the phase change seen, missed your research mate.

BTW got any of that r23 left?

Regards

John.

[Russell_hq]

Nope, I had to give it back to dean & wood. Plus im out my flat till atleast christmas. Im staying in rented accomdation atm because of a fire in the building i was staying in so no fun for me at the moment. Take a look if you want.
http://news.bbc.co.uk/go/em/fr/-/2/hi/uk_news/scotland/3588806.stm

Would have liked to get into this autocascade action though :(

[saratoga]

Just wondered.. anyone know what MAPP gas/brazing gas is?

Propadiene and Methylacetylene. I looked them up a while ago, and neither was all that interesting. A lot like propane, except a little higher temp as I recall.

[Russell_hq]

And also the acetylene in it can explode spontaneously without the presence of oxygen. I believe it decomposes under high heat and rappidly expands! Making it far more dangerous that propane as it aleast needs O2 for it to explode.

[floshey]

I would rather go on latent heat per m3
At 1 atm saturated conditions.

R290 = 92,930 kJ/m3
R22 = 122,522 kJ/m3

this gives it approx. 32% more capacity at atm. pressure

How do you come up with these numbers? Or how to calculate them, cause none of the mentioned info can be found @ AirLiquide :confused:

[Russell_hq]

density * specific heat of vaporisation i.e kg/m3 * kJ/kg = kJ/m3

[Russell_hq]

I thought about this again and think I should have used the vapour density instead of the liquid :(

As the compressor is moving volumes of gas and not liquid I think the volume of gas produced relative to how much heat it takes off is what counts. If we do that then we get the following figures

R22 = 1099.5 kJ/m3
R290 = 1029.3 kJ/m3 (Energy removed per volume of gas produced)

This give R22 a slight advantage at atmospheric pressure of 6.8%
Compare this to pythagoras's figure of 8%, we can see that using pythagoras's approximation using m.w. gave a good comparison with what I believe is the true figure. :)

On a side note, at around -46ºC R22's advantage is gone and below that temp, R290 starts to take over :)

[kayl]

hmmmm that is good to hear russell hq, I like propane

you got some good math happen there i like that.
how does r290 compare to say r404a and r507.
i have always wanted to know about this stuff.

its a real pitty about your house hey. you would have done such a nice revision 2 autocascade and done some cool benches.

[Russell_hq]

Ask and you shall recieve.

http://www.russellpetrie.plus.com/images/autocascade/GasComparison.gif

[kayl]

:shrug:
what can i say and so quick. :toast:
r290 lowest HMM.
i want 410a.
thats what the new inverter split system airconditioners run standard in australia

[Russell_hq]

Have a look at this before u think about using R410a. Some high pressures there.

http://www.russellpetrie.plus.com/images/autocascade/GasComparisonPT.gif

[Epsilon]

offtopic:

I like all the temps in the avatars :D

only fluke and uei tempmeters :D