I was doing some mental math about our home made chiller. We have a 120 watt laser. At most it could generate 120 watts of heat. It seems overkill to use an 1100 watt air conditioner to cool it. I’m thinking that an ordinary water cooler would have enough power. Does anyone have one handy?
Thermodynamics is a bitch.
We have a 120 Watt output laser. If it were 100% efficient, there would be no heat to remove with the chiller. We need to remove ((watts out from the power supply) - (watts out from the cutting end of the laser)) as heat. 1100 Watts is the input wattage of the air conditioner. Figure it is about 40% efficient, after we mod it to act as a chiller…
Estimate that it’ll couple 500ish watts of cooling power into the water bath. Power supply is putting out about 20kv, and we are not letting it go above 26mA = 520 watts going into the laser. 520 watts going in - 120 watts coming out = 400 watts needing to get removed by the chiller…
For short burns, you could rely on thermal mass of your water reservoir. It takes one thousand calories to raise the temperature of 1l of water by 1 degree C. So if your chiller is underpowered, you could rely on the difference between the safe maximum temperature of your water and the starting temperature to compensate. For a while… But I don’t feel like trying it for 10+ hour scans and huge living hinges.
This project uses two 92 watt chillers. I just think an electronic cooler would bring the noise level down
In keeping with my earlier estimates… he’s putting almost 200 watts of cooling power into chilling a 40 watt output laser, and barely keeping up with it from the numbers I’m getting by skimming the article. There Ain’t No Such Thing As A Free Lunch.
He could gain much by realizing that the TEC series couplers are designed to run as constant current devices, and really work better closer to 15 volts than 12 if you are blindly driving them with constant voltage. A CC power supply is the correct way to do it. People tend to run them at 12 because portable picnic coolers are designed to plug into vehicles and use the same modules (at a fraction of their designed efficiency) I’m planning on sourcing some modules to do cold-suits, coolers, dog-beds etc… but I had not planned to have any in hand until next summer.
If we wanted to work on noise levels, we’d concentrate on the air filtration unit. That thing is good and loud. Well at least loud. It could stand to be gooder. Unfortunately, I think it needs moar powar not more quiet… we still get smoke back into the building when we do long cuts, and could probably stand to have better compressed air flow to the cutting end (thicker acrylic still tends to weld closed on the cut). I turn off the blower as soon as the smoke clears to make the room less noisy, but I’ve never bothered to cycle the chiller on and off… I slept with a unit like that next to my head for years and it never really bothered me noise wise (or at least bothered me less than trying to sleep in the heat would have!)
On the laser filter end of things I was wondering about making a swamp cooler on the output. Instead of a dry hepa filter we could make a stack with a reservoir at the bottom, 4 course washable filters in the middle, and a pump to bring water to the top.
The control panel for the spare air conditioner in the metal shop is missing. It became separated from the main unit. If you know where it is please let me know. If you don’t know what something is for, please don’t toss it out willy-nilly
I found another window-rattler at home. (Previous owners of the house left it…) We might see if it is adaptable to our needs.
I just pulled the front panel off the potential donor-chiller here. I don’t know if the damn thing works, but the control panel is just 16 wires on two connectors. Super easy to extend and modify. The control board itself is pretty simple too. Might be able to hook it up to a simple interlock system by splicing in a relay or two. Has nice clicky through-hole momentary switches soldered to the board, and I’m pretty sure the momentary switches just short pairs of wires in the harness. There really is not much logic in the control board, mostly some buttons, leds and two 7-segment LED displays for temperature setting.
Power supply is putting out about 20kv, and we are not letting it go above 26mA = 520 watts going into the laser.
I looked up the MYJG100W power supply that we have in there right now… It maxes out at 28mA, and constant output voltag is 40kv… Yep, 1040 watts go into the tube. 119 comes out as a laser. 921 is removed as heat by the chiller.
That makes the laser tube 11.4% efficient at converting electricity to coherent light. Pretty impressive for a hand-blown glass tube, with a bit of vacuum, some gas and some IR-reflective surfaces. Back in the '70’s Bob Iannini described how to build a similar tube yourself and build and troubleshoot the power supply for it, but he implied that it would be closer to 2% efficient.