Project 173K: -109C first testrun

[DaBit]

The first testrun without any optimizations. High stage has not enough refrigerant (superheat almost 15K). The low stage has certainly not enough refrigerant; I just gave it a shot. Superheat at the compressor is more than 70K. But I admit that I must do accurate measurements. But that's something for the next session.



Interstage is -35C. This is measured at the TEV bulb, so it is heated a bit by the incoming hot ethylene. 'real' temp is probably lower. I cannot measure pressures at the moment since I have only one meterset.

Evaporator (unloaded) runs at -109C. This was 5 seconds before I pulled the plug. But as I said: it's a testrun.

Low stage pressures. Discharge pressure is a bit low IMHO. But, this is with too little refrigerant.



Next thing on the list is finishing the electrical interconnections (currently only the high pressure switch is connected, the rest is plugged directly in the wall outlets). Then, optimization of the high stage. And finally, optimization of the low stage, with load.

edit: a system overview of a few days ago. I promise I will shoot more detailed pictures and finish the article on my website. But burning copper is more fun than writing

[Charles Wirth]

Sweeet, nice job

[nas]

thats what im talking about baby ... great work once again

[DaBit]

Static pressure was only 6 bar after equalisation. Thus, very little ethylene. No expansion tank mounted yet. The weakest low stage component has a maximum working pressure of 22 bar (and a much higher burst pressure), so I can go a long way when adding refrigerant. Still, I think I will add an expansion tank just to lower the compressor motor startup torque required.

The only problem is where to leave it. It's already crowded on the baseplate, and it will be even more crowded when I fitted the electrics.

I might consider putting 3-8 meters (9-24ft) of 22mm (7/8") capped copper pipe in a zig-zag pattern, and mounting that below the baseplate. The cascade is high on it's wheels, so that would not be a bad spot after all. Of course I would add a steel plate to protect the pipes.

An old receiver is easier, but I don't have any spare ones left.

But I have plenty of time; the high stage needs attention first.

[Sphinx]

DaBit WOW! -109 at first run ! Very nice, nice and nice again !

[LardArse]

Very nice. I'm thinking of getting some ethylene as well as the price is about $300 for 12kg, very good pricing.

[DaBit]

Very true. I paid about EUR 70,- for 3kg, excluding bottle rent and dropoff cost etc.

But keep in mind that pressures are insane. My pressure gages only show low pressures because there is not nearly enough ethylene in the low stage.

Make sure you can maintain -30C SCT or lower, or don't even think about using ethylene but consider ethane instead.

[captaincascade]

Aggghhh Bar!!!

Big time congrats, you are a sick man. you are now in the top 5% of my trade, lol. you need to stop im starting to feel stupid over here..... That controler has never been happier. good job!!!! Very very impressive!!!


you people are going to be the death of me.

[Gary Lloyd]

Looks like all of your research is paying off, DaBit. Congrats.

Don't worry about not having a second set of gauges. Interstage TD is about the same as TEV superheat, so once the high stage is set up, down to temp, and has the right superheat setting, then the low stage SCT should be about the same as TEV bulb temp on the high stage.

Hope that makes sense.

[DaBit]

Originally posted by captaincascade
Big time congrats, you are a sick man. you are now in the top 5% of my trade, lol. you need to stop im starting to feel stupid over here.....

No need to, yet
I still haven't passed your loaded temps..

That controler has never been happier. good job!!!! Very very impressive!!!

and I haven't been happier with any other controller. The thing reacts damn quick on temp changes, and it seems accurate too.

you people are going to be the death of me.

Next idea is already brewing in my mind. I've passed the -100C mark, but not yet the 100K mark

[DaBit]

Originally posted by Gary Lloyd
Looks like all of your research is paying off, DaBit. Congrats.

Thanks
Research is done, finetuning begins. I bet I will need your help in the near future

Don't worry about not having a second set of gauges. Interstage TD is about the same as TEV superheat, so once the high stage is set up, down to temp, and has the right superheat setting, then the low stage SCT should be about the same as TEV bulb temp on the high stage.

Hope that makes sense.

It makes sense, but I will measure this once to be sure of that.
I expect a small difference (in the order of 2-4K) between temp @ TEV bulb and low stage SCT. With ethylene, this increases pressure quite a lot.