Thread: One for the fridgies

Originally Posted by 4bee

TINY! You ain't kidding Rick, it looks like they were meant for a Display case.

I know diddly **** about C02 systems, WAY before my time. But the following makes a couple of relevant comments:

7) CO

₂

has a greater volumetric cooling capacity as compared to commonly used HFCs. For example, in a -20F application, R-404A has a latent heat of vaporization of 81 Btu/lb-min. As a comparison, in the same application CO

₂

has a latent heat of vaporization of 130 Btu/lb-min. The resulting mass flow requirement for CO

₂

will be approximately 38 per cent less, with the benefit of smaller compressor displacement and smaller pipe sizes.

CO2 supermarket refrigeration systems become more common

I know diddly **** about C02 systems, WAY before my time.

Me too OF, only what I gleaned from a Scottish Ships Engineer that became our Works Manager way back. That was also a challenge due to his accent.

As it never had a place in my training I didn't pay much attention especially to all the physics etc of it all. Whoever thought then, it would be used in a Supermarket system near you in 2019 & earlier?

It was just for Cargo ships wasn't it?

And IIRC R404ª has similar % advantages over 134a in volumetric efficiency, which is why a lot of us went that way on introduction.
The downside with CO2 is that the pressures are freaking scary!

I've also been warned not to use hot water during an evaporator defrost, the resultant BOOM gets your attention, but then someone else said used intelligently it isn't an issue, just make sure you pump the coil down first.
I'm a wuss, I still use room temp water

And you need to observe a minimum charging pressure or it freezes in the lines.

Originally Posted by Old Farang

I know diddly **** about C02 systems, WAY before my time. But the following makes a couple of relevant comments:

7) CO

₂

has a greater volumetric cooling capacity as compared to commonly used HFCs. For example, in a -20F application, R-404A has a latent heat of vaporization of 81 Btu/lb-min. As a comparison, in the same application CO

₂

has a latent heat of vaporization of 130 Btu/lb-min. The resulting mass flow requirement for CO

₂

will be approximately 38 per cent less, with the benefit of smaller compressor displacement and smaller pipe sizes.

CO2 supermarket refrigeration systems become more common

The big advantages of CO2 are;

a) it's cheap
b) it's efficient
c) low GWP which earns the Supermarket environmental kudos.
Which they then **** away by giving away tonnes of plastic toys that go straight into landfill....

Originally Posted by 4bee

Me too OF, only what I gleaned from a Scottish Ships Engineer that became our Works Manager way back. That was also a challenge due to his accent.

As it never had a place in my training I didn't pay much attention especially to all the physics etc of it all. Whoever thought then, it would be used in a Supermarket system near you in 2019 & earlier?
It was just for Cargo ships wasn't it?

Actually, I have been both chief engineer and chief electrician on ships / oil rigs. I originally trained as an electrical fitter / armature winder, and later spent years studying marine engineering. The first ship that I worked on had a brine circulating system, but I'm damned if I can recall what the primary side was. All the rest of the drillships and rigs that I worked on just had direct expansion Freon type systems for accommodation and ships stores.

CO2 is now widely used in ships fire suppressant systems since the banning of Halon.

Which they then **** away by giving away tonnes of plastic toys that go straight into landfill...

Yep Rick, I wondered about that. Get shot of plastic carry bags & replace them with plastic grocery items for kids. Like they will look after them? I also wonder how many are swallowed by kids & need Emergency hospital care.

We used to call them "The Wise Men of the East" as all decisions seemed to made in the East by Coles & Woolies.

OF. That sounds like an interesting career you have/had. Do you drive a Land Rover around the decks?

Actually I sort of had a temp job lined up as Electrician on board MV Woolhara (now scrapped) of a Swedish line whose name escapes me for a mo. Trans Austral or some such.

First Clipon Refrigerated Container (Luke) out of Adelaide & taken back to Sweden for trials & testing.

I still don't know why the then current Aussie Sparky thought I'd be right for the job, I mean c'mon. WTF did I know about Ships Electrical systems? Zilch is what.

Anyhow my boss at the time put the mockers on it & said I was needed for a job that was coming up, but truth be known he probably thought I wouldn't come back. He may have been right for all I knew. Anyhow it didn't happen.

Ed. As it happened the young bloke from Queensland who did take the job didn't come back & liked the life at sea & stayed on permanently. My Boss must have known something I didn't.

Walked out out here at 4:00am.
This is less than six months old
Partial ice up on 4 modules.

In keeping with the posts concerning CO2, it has been in use as a fire suppressant for many years, both in small portable extinguishers, and fixed storage flooding systems. For years the practice has been HP storage cylinders at around 60 Bar / 800 psi stored at ambient temperature.

The modern trend, particularly with bigger flooding systems, is an LP system using an insulated refrigerated bulk storage tank at around 20 Bar / 300 psi, kept at -17 degrees C. Usually two small common type direct expansion refrigerating units with the evaporator inside the tank are employed to cool the CO2.

I guess that most fridgies on here are unlikely to run across one of these, as CO2 cannot be used where any protected spaces are occupied, or likely to be occupied most of the time. However, you could find such a system in a big factory or similar, where individual sections, such as big transformer rooms, are normally sealed.

http://www.incontrolsystems.net/low-pressure-co2