First black friday in my life I had 1/2 a million dollars to drop!

[Fridge Repairer]

Putting trans-critical CO2 system into its new home! Works not suppose to be so much fun!

[hotntired]

needs moar details.....and pics of the system in place and doin it's thang......

without the details, I'm lost, because I have no idea what a trans-critical CO2 system is.

[absoair]

Google? youtube?

[hotntired]

But, it's his post with his system. I can educate myself all day long on all types of things, but I like the conversational approach.

[Fridge Repairer]

This is the first Trans-Critical CO2 store going in within the United States. CO2 means extremely high pressure. Yesterday I met with the engineers from Hill Phoenix. We unwrapped one of the 4 rack systems going in. I myself do not know anything about this CO2 system but I am amped up to be running this project! The guys from Hill Phoenix gave me a brief synopsis of all the components and their operating pressures. Discharge pressures run about 1780 PSI. That is no joke there. I plan on erecting a blast chamber where I can stand while doing my pressure testing. We are having a training class next week. And Ill be able to share more then. Here is some eye candy for you in the mean time.

[hvacguy99]

That looks really awesome. Keep us posted on it.

[Fridge Repairer]

Tomorrow I have a 10,000# Lull coming in so we can lift the heaviest rack into the room. The first one they sent could not lift rack DT3. Walkin freezers and coolers are being built. Underground plumbing is going in and probably next week we will be doing a helicopter lift to put the 5 condensers, oops I mean GAS COOLERS on the roof. Work aint suppose to be so much fun!

[hotntired]

Wow. That's a big deal. I take it from the pic's that this is an existing building being renovated into a supermarket? Are all the piping systems dropped down to the cases from overhead? Thanks for the info. Great pics.

[koolkahuna]

[QUOTE=Fridge Repairer;14686151] "Tomorrow I have a 10,000# Lull coming in so we can lift the heaviest rack into the room. The first one they sent could not lift rack DT3."

Did the lift operator try to lift it and couldn't?
I wouldn't let ANYBODY near any equipment without assurance on paper of lifting capacity and insurance. I have seen lifts where a machine got it off the ground and one small factor caused the load to drop.

Even showing up on site then checking capacities and load weights is kinda too late...

The lift operator is ultimately responsible but if your equip gets damaged there is probably a shortage of replacement units on the shelf.


Not trying to grind your gears but hoping to save you some grief!

I too am looking forward to further pics of this cool job.
Hope it goes perfectly for you!

[pherman]

Nice Pics.

[zartangreen]

20120198674 That patent paying off,, would love to pick your brain,, congrats

[jpsmith1cm]

Neat stuff.

I've been kind of struggling to wrap my head entirely around trans-critical CO2 refrigeration.

It's a weird system.

[blitz]

and all the piping will be brazed with sil-fos? will it hold? or do you have to use special jointing method? That's a lot of PSI

gas cooler, eh? does it condense it to liquid? or just take some temp off? never even looked into CO2 application. do they use the same refrigerant cycle?

[koolkahuna]

JPSmithcm1 -
"Neat stuff.

I've been kind of struggling to wrap my head entirely around trans-critical CO2 refrigeration.

It's a weird system."

Maybe this will help JP - These three articles are from ACHR News back in 2003 - 2004 on Transcritical and Subcritical refrigeration that explains it pretty well.

The first one explains the cycle and the last two are examples of installations in a supermarket in Copenhagen, Denmark in the first one(pretty interesting), and system compatibility and safety in the second one.


http://www.achrnews.com/articles/co2...critical-cycle


http://www.achrnews.com/articles/co2...ermarkets-cool


http://www.achrnews.com/articles/co2...-refrigeration

[jpsmith1cm]

Alright.

I knew all that, already.

Here's what has been kicking my a$$ as far as grasping this system.

How is any refrigeration being done? Since the CO2 is hitting the HPEV as a supercritical fluid, it isn't truly a liquid and, thus, isn't changing state as we're accustomed to seeing.

Without a change of state, you're not going to be absorbing heat and, therefore, you can't be refrigerating.

[barbar]

Alright.

I knew all that, already.

Here's what has been kicking my a$$ as far as grasping this system.

How is any refrigeration being done? Since the CO2 is hitting the HPEV as a supercritical fluid, it isn't truly a liquid and, thus, isn't changing state as we're accustomed to seeing.

Without a change of state, you're not going to be absorbing heat and, therefore, you can't be refrigerating.

Start at the beginning, the gas cooler (or just think of it as a condenser), is still giving its energy away. Because the gas is trans-critical, the molecules are just not sticking together as in a liquid. Even though it has the energy as if it were a liquid.

When the trans-critical fluid (i use fluid, not the word liquid), hits the expansion device (pressure drops, below the trans- critical point. As with a normal refrigerant, part of the fluid reverts to liquid and the remainder reverts to a vapour. The colder the cooled trans-critical fluid (like sub cooling), the less flash gas you have after the expansion device, and the greater the liquid and more net refrigeration effect.

You may find, that the CO2 which is delivered to the cases, is not trans-critical, (as change as happened at a the second stage of compression)

Have you ever seen cold after your nitrogen valve, when purging, another trans-critical fluid. Look up Joule Thompson.

[koolkahuna]

Read it again JP. Halfway down the page on the first link.

"Figure 3 represents a transcritical cycle with CO2. The cycle diagram looks the same; the only difference is that the heat rejection process occurs above the critical point. Unlike the subcritical condensing process, where temperature stays constant, temperature decreases during the entire transcritical heat rejection process. There is no condensation in a transcritical cycle, and we call the process gas cooling. In low ambient conditions, the process might occur below the critical point, and condensation, rather than gas cooling, would occur. This is the fundamental difference between subcritical and transcritical cycles"

[barbar]

Hope this helps

Wiggly line, not part of the process, but just my shaky hand!

[jpsmith1cm]

Read it again JP. Halfway down the page on the first link.

"Figure 3 represents a transcritical cycle with CO2. The cycle diagram looks the same; the only difference is that the heat rejection process occurs above the critical point. Unlike the subcritical condensing process, where temperature stays constant, temperature decreases during the entire transcritical heat rejection process. There is no condensation in a transcritical cycle, and we call the process gas cooling. In low ambient conditions, the process might occur below the critical point, and condensation, rather than gas cooling, would occur. This is the fundamental difference between subcritical and transcritical cycles"

I had understood that the heat rejection took place above the critical point, meaning that the fluid didn't truly condenser. Heat rejection wasn't the problem for me.

Start at the beginning, the gas cooler (or just think of it as a condenser), is still giving its energy away. Because the gas is trans-critical, the molecules are just not sticking together as in a liquid. Even though it has the energy as if it were a liquid.

When the trans-critical fluid (i use fluid, not the word liquid), hits the expansion device (pressure drops, below the trans- critical point. As with a normal refrigerant, part of the fluid reverts to liquid and the remainder reverts to a vapour. The colder the cooled trans-critical fluid (like sub cooling), the less flash gas you have after the expansion device, and the greater the liquid and more net refrigeration effect.

You may find, that the CO2 which is delivered to the cases, is not trans-critical, (as change as happened at a the second stage of compression)

Have you ever seen cold after your nitrogen valve, when purging, another trans-critical fluid. Look up Joule Thompson.

I think that was the thing that I was missing, somehow. That the supercritical fluid essentially had the same properties as a liquid is so far as the refrigeration system was concerned.

I couldn't quite wrap my head around refrigeration happening without liquid hitting the metering device.

[koolkahuna]

Barbar, you actually brought up a good example, your nitrogen tank gets cold as you release vapor from the regulator. That nitrogen starts as a high pressure gas (not a liquid) and absorbs heat as it drops in pressure to low pressure gas exiting the reg. I think that is a perfect example of the Joule Thomson effect.