Originally Posted by Gray Mole
Well by popular demand, I figured I'd get some pics of the triple evap system I've been testing out. I doubt I'll be building it for real, but I did get some interesting results from it.
The system is a 3/4HP rotary compressor like this one
And the rest is 3 Mach2 heads I got from some evap changes, which I redid with new captube and bored out for 3/8" suction.
The 'CPU' evap got 2.5m of .031" captube, and the other 2 got 3m of .031" captube.
The suction, as shown in the pics, is 'biased' for the cpu evap. Suction pulls on the cpu first, with a slightly shorter suction on the cpu as the 2 GPU evaps, about 6" shorter.
Gas was R290 initially, then I used 402a, with just a little R290.
The final testing for temps is what I'll show, as it reflects closer to what it would really do if it were done. I think I would need to do something with valving if it were going to be built properly, as the cpu evap couldn't work without load on the gpu evaps due to low pressure in those 2 not allowing for decent refrigerant flow in the CPU evap.
That was how the duallie was set up.
And that's with the third head attached. I then partially insulated it. I'ts just solid suctions for testing things out. When I build the Duallies for real I'll be using flexi's and the compressor will likely be mounted sideways to try to make it fit a narrower box.
That's the mess with some insulation, and the 150w tester on the cpu, and the 275w tester with the 2 GPU evaps on that one sharing it. Not pretty, but pretty effective. That makes for a total of 425w or so on the system. Should be a good test of how well the rotary will carry such a load.
That's GPU1
and GPU2
I think that one of those 2 is a little blocked. I noticed from the start that after I put the third head on and redid the captube that one of the captubes seemed a little squashed against the side, so I think I'm just not getting the flow that I need to it. They both hold the load, just with dual head I had a much better balance. Still 3 degrees wasn't bad.
And the CPU evap.
Yeah, I could really use a 4 channel temp probe, or at least another 2 channel as switching is really getting annoying, but not a big deal.
Naturally I forgot to take some pics before I got the no load temps, but that's after I'd taken the insulation off to get better pics of the layout. Befroe I stripped it I was seeing about -55 or so at no load, but the lack if insulation brought that up. That was the cpu evap, but the temps were about -53 on the cpu and GPU2 and -52 or so on the GPU1 evap. As I said, there was something making the one GPU evap sit a little higher in temp than the other.
I didn't get the GPU's to work without the cpu loaded and vice versa. Just not enough pressure to keep them flooded as the refrigerant didn't want to go to the higher pressure area, and just snuck out the low, but with them all loaded it worked ok.
Pressures were high to keep it working though. I was seeing about 230psi or so on the high, and about 7psi low under load, and 190psi high, and around 2inHG low at no load.
So not bad anyways, and that was tuning it for 10c superheat at the suction accumulator bottom before the short return pipe. So the capacity was all there. I could have tuned it leaner, but the compressor was very cool even under load for a Rotary. After it was all tuned and running, it wasn't quite at 100c on the compressor body, about 97c or so.
So as a test it really helped me get around working on the multiple evap systems. Gave me insight in to how they work, and what changes it would take to make it a viable option.
Working fully I'd have expected about -38 on each head. Nearly -40 on a triple evap system running full load. And at over 400w, I was seriously impressed with the capacity of the rotary too.
So that's the project all done for now until I get some proper evaps and suction lines, and then I'll be making a few dual head units out of it. I was able to run the dual evap independantly, which was quite cool as I'm making them with the option of either dual GPU, or CPU/GPU, so with a high load on one and a low load on hte other I need to know that there's not goin to be any problems with the capacity falling off on either one, and the dual tests indicated there was no problem at all with that.
So basically, triple evaps are a pain, but are really cool when they work. And Rotaries are :woot:
:toast:
Gray
