Transcritical CO2

[Wynand]

Has anyone done pipe sizing for transcritical CO2 refrigeration system? Looking more at the high Temp side when in transcritical state..?

[desA]

Would Coolpack be useful to you? It has line sizing calculations.

[Wynand]

Coolpack does not give me CO2 at the pipe sizing...it only has CO2 in a DX cycle system, not pipe sizing. The other program I tried was Linesize, but it allows you only to do sub-critical CO2 and not transcritical.
So I have done the calculations by hand, so would just like to confirm it maybe against something...the change of density at certain outlet tempertures and pressures make the velocity change great accross a range of operating compressor capacity.

[desA]

Are you sure about Coolpack not doing line-sizing. Check on the Auxiliary calcs page.

You are correct about the velocity changes across the transcritical line - oh yes, indeed.

[Wynand]

Yes I checked again. It does not give R744 as an option under gas pipes or liquid pipes. I've got the 1.64 version...is that an outdated version?
Have you done any pipe sizing for transcritical piping? My calculations makes sense, Sergio (enex) did confirm more or less what I found. Just want to make sure...

[desA]

Yes I checked again. It does not give R744 as an option under gas pipes or liquid pipes. I've got the 1.64 version...is that an outdated version?

Well, considering the latest version seems to be 1.48, you're doing very well. :D


Have you done any pipe sizing for transcritical piping? My calculations makes sense, Sergio (enex) did confirm more or less what I found. Just want to make sure...

Say hello to Sergio for me. Nothing wrong with doing hand calcs, although I typically use Chemstations as a back-check for the properties. Properties like density, viscosity, conductiviy generally decrease substantially across the critical line - this will send your velocity calcs ballistic, if you are not ready for it.

Are you building a refrigeration system, or heat-pump? If it's a heat-pump watch the LP calcs as they approach critical as well.

Also, if it's a heat-pump, I'd be interested in collaborating as I'm heading back to SA in mid August, after my heat-pump trials are settled in SE Asia.

[desA]

TRANSCRITICAL ONE-STAGE CYCLES:
DX evaporator with CO2 as refrigerant

TRANSCRITICAL TWO-STAGE CYCLES:
DX evaporator with CO2 as refrigerant, no intermediate load

These are the CO2 options in Coolpack 1.48 The pipe calcs are in the 'Auxiliary' page.

[Wynand]

Sorry, got that wrong, I have the 1.46 version.
We are looking at a refrigeration system. Not too big, but will give us a good indication of what the results could be when using a transcritical system. But I have done my masters degree on CO2 heat pumps in Potchefstroom..."A techno-economical analysis of a CO2 heat pump". Have worked for M-Tech Indstrial as well where we built and designed R-22 and R407C heat pumps. If you like you must let me know when you are back in South Africa, would be nice to have a talk with you and see where the technology is going...I am situated in Jhb at the moment...

At this stage I am happy with doing hand calculations since the properties change so much in the transcritical state... Using EES you could verify from the PH diagram on what youre calcs will look like on the diagram...
Thanks for the input, is appreciated.

[desA]

Super Wynand.

By-the-way, some of the M-Tech heat-pump designs don't have filter-driers - capillary tube with no strainer. Perhaps those are the ones imported from China. Going to cook their compressors, I'll be willing to bet. :D

Send me your contact details per pm on RE & I'll contact you when I get back. I'm keen to develop a CO2 heat-pump system in SA.

[Wynand]

Hehe...I think those are the imported household heat pumps, I were not to keen on them....a few reasons why I needed to leave M-Tech, one of them was to work on CO2.
I will send you my details and is looking forward to meet you.

[desA]

Thanks for that. You can e-mail me any time - look forward to meeting you. Sounds like we may have a lot in common on the CO2 heat-pump side. :D

My e-mail address is listed on my website. Look forward to hearing from you.