While I was working on the quad headed gpu cooler, I chipped away at a couple of small cascades. This one's done now, figured I'd post it. Ended up being pretty good, slightly colder than the other small ones I've been making for some reason.
The specs...
Stage 1
Rotary compressor 10cc/30LRA
404a Refrigerant
20 plate heat exchanger
7' .036" Captube Brazed to return
10k btu condensor/fan
Stage 2
Rotary compressor 7.5cc/25LRA
1150 Refrigerant
Temprite oilsep/handvalve
1m Braided Flex
Duniek (I think) evaporator 40mm
Universal Chilly1 mount (modded to fit) with ALU plates
7.2' of .031" captube brazed to return + SLHX mod
It's installed in a medium size window AC case I modded to fit. Had to make panels and stuff close it up and fit displays as well as the venting to cool the compressors but it worked out pretty good. I couldn't focus on it totally since I have the other project I'm trying to finish, but I spent a few weeks slowly chipping away.
I've made another one even smaller but with basically the same setup, a few pics of this one, since it looks close to the same. The actual cascade doesn't take that long to make anymore after building quite a few I guess, but the finishing stuff like wiring and the case can be real time consumers.
So pics of how it's put together...
It's uninsulated on a few spots, makes it easier to see where the 'cold' goes I guess. The brazed captube is shown on the 1st stage but the second stage cap and flex are insulated. I got a pic of the brazed pipe that makes the very basic SLHX setup. I don't really want more heat exchange on the suction line for the second stage, since it could lead to overheat on the compressor. Just a bit helps precool the gas into the HX as well as helping vaporize the refrigerant on the way back to the compressor.
So the one I'm actually talking about is this one...
Didn't let it cool that long, usually sits around -35 to -37c or so on the display for the HX (-40ish in real temps) and about -110 to -115c showing on the Evap display when it's warmed up (so around -105 to -110c) with the displays being off. I'll get to that.
Finished it in white since it was already a white case, easier to repaint that way.
Handvalve is on top, easy to get at and only needs to be opened every few hours of running. Looks like a flower up there :p
The temps are pretty amazing on it, though when it warms up it runs at 'normal' cascade temps for a smaller one.
The displays are off but the red display (evap) shows 5 degrees too cold, and the blue one (the heat exchanger) shows 5 degrees too warm. Knowing that makes it more or less unimportant though. They're consistently 'off' so if you know how and how much, then working with them is fine.
Seems like every one of these displays (both types) are out by a bit, sometimes too warm and sometimes too cold. I buy quite a few since they're inexpensive compared to the brand name ones from the fridge shops. I'm going to see if I can get the suppliers in Hong Kong to get me a way to calibrate them myself. It shouldn't be a huge issue, but it's all in the price I guess. If it's 50 bucks more for that, then it's just not worth it. I try to make them as inexpensively as I can, since a cascade is already kind of a pricey toy, so whatever you can save you don't have to charge for.
When the compressors are still cold, they actually help it cool the gas, as well as the garage where the workshop is was only about 12c or so, so the unit was running unloaded about as cold as it could ever get. Unloaded temps don't mean a lot, but it's a cool number. The -130c or so temp is actually only -125c. But that 'colder' effect works throughout the range until the compressors start to dump heat into the system.
Actual working results are -110 to -115c unloaded when warm and 20c to 25c ambient temp. -100 to -105 at 200w. -85c when hot and 350w load after about 1hr of load. When totally cold and the first 10min of load it held around -95c at 350w, slowly rising to -85c and holding there. That's all measured on the Fluke, temps showed 5c colder on the display.
for such a small cascade it works really well. The amps are running around 6-7 at full load, 4-5 average. So around 500-600w of power usage. Not bad for the temps. The small Rotaries are pretty good that way.
Measurements of the case are around 18"x15"x15" so it ends up a really small cooler, not a lot bigger than a larger single stage. Using the tweaks and simplifying the slhx setup helps keep the internal size smaller, and it allows for a larger 20 plate HX. The HE condensor really helps too.
This is definitely the best result I've had on the small cascades though. I've been seeing around -100/-80c load on the small ones so far. This one just seemed to work better than the others, but getting the charge and captube just right isn't easy, and it doesn't always happen as well as you'd like.
Since I'm working on another cooler, figured I'd let this one run the tester through an hour or so of load cycling.
I tried to get the timer in there, so you could see the length of time on the increases in load, then the decreases with recovery times.
Basically, I ran it for around 10 minutes to get the compressors just a bit warmed up, so it wasn't showing that silly -130c number. Still not totally warmed up but close where it's starting.
Then, running a few minutes apiece at increasing load in 50w increments.
First pic shows recovery after the short 400w test.
After that, decreasing the load by the same, giving it 5 minutes or so for each setting to recover.
Last, I went straight for 350w for a bit to show the fully hot running temps (if you bench for longer periods then that's what to expect on a serious cpu at full load/high oc and vcore)
back to fully unloaded temp with the compressors heated up.
Basic results can be seen in pics, but you do have to allow for the 5 degree issue. Fully hot it runs -110c unloaded and at 350w it'll do about -90c taking that into account. Shows -115c/-95c unloaded/350w on the display.
Showed a pic of the resistor probe compared to the display. Like I said, around 5 degrees off.
It'll do 400w at a push but the HX does get warmer than I like. Have to add 5 degrees colder for it :p and that means it's getting under the -30c HX temp. I like it under that if possible.
Nice to see it push that high though. In cases with 6 core/12 thread intel stuff you can see some pretty insane wattage. Should handle most things.
So that's the works as far as a basic load test goes. Easier to do than to get pics that make sense and since I'm terrible at taking pics...
But yeah, if you follow along the timer on the power meter, you can see the basic idea of times, recovery etc.
Edit: I found a pot adjustment on the larger display Had to drill a small hole in the plastic housing but it's now calibrated to the fluke. Not going to take all the load test pics again though But it's reading the 5c warmer now, matching up with the Fluke's readings.
This is all copied and pasted from a couple posts I made elsewhere while XS has been down, sorry if it's a bit cluttered
Thanks
Gray
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