DIY 5289 Btu/h chiller
Posted: Mon Jul 06, 2020
Was doing some very heavy cutting a few weeks back and glanced over to see my "fish pump" water reservoir heading towards 40 degrees C. As the temperature was rising, I noticed my power was not cutting the material as effectively as at the beginning of my laser work. This while the tube still drawing 22ma. I was told that I should keep the tube between 20 - 25 degrees C. during laser tube operation for optimal results.
Decided to kluge together a laser chiller from a used 5000 Btu window AC unit in the local classifieds. The unit selected was within a year old, made for a small room and is dimensionally small as possible while maintaining the minimum 5000Btu/h cooling rate.
Bought the AC unit, stripped it apart, removed the evaporator fan and ran the unit. I wanted to see how cold the evaporator would get sitting there. When the compressor kicked in, frost formed on the evaporator within 45 seconds. So decided to get to work on my chiller initially as a "proof of concept" build. Built a box out of 1/4" plywood, fiberglassed the inside and built acrylic divider to isolate the evaporator in the lower half. The return line would have to flow through the evaporator coils before returning to the fish pump to pump the now cooled water back to the tube. Closed system. First test was encouraging as I could easily drive the water reservoir down to 5 degrees C from 26 degrees C ambient start within 6 minutes.
Here's the system in action during a cooling cycle. I'm still experimenting with the best placement for the thermal sensor, condenser cycling, calibrations, etc. The AC unit had a mechanical "cooling" thermostat unit that I replaced with a W3230 digital thermostat unit. These are cheap and can be had everywhere on eBay. I happened to have one that I had used previously on my plating tanks.
Here's the final schematics and diagrams of my build. What I like about doing this is if it came down to a large or high power tube in the future, I could always scale up to a large AC unit.
Decided to kluge together a laser chiller from a used 5000 Btu window AC unit in the local classifieds. The unit selected was within a year old, made for a small room and is dimensionally small as possible while maintaining the minimum 5000Btu/h cooling rate.
Bought the AC unit, stripped it apart, removed the evaporator fan and ran the unit. I wanted to see how cold the evaporator would get sitting there. When the compressor kicked in, frost formed on the evaporator within 45 seconds. So decided to get to work on my chiller initially as a "proof of concept" build. Built a box out of 1/4" plywood, fiberglassed the inside and built acrylic divider to isolate the evaporator in the lower half. The return line would have to flow through the evaporator coils before returning to the fish pump to pump the now cooled water back to the tube. Closed system. First test was encouraging as I could easily drive the water reservoir down to 5 degrees C from 26 degrees C ambient start within 6 minutes.
Here's the system in action during a cooling cycle. I'm still experimenting with the best placement for the thermal sensor, condenser cycling, calibrations, etc. The AC unit had a mechanical "cooling" thermostat unit that I replaced with a W3230 digital thermostat unit. These are cheap and can be had everywhere on eBay. I happened to have one that I had used previously on my plating tanks.
Here's the final schematics and diagrams of my build. What I like about doing this is if it came down to a large or high power tube in the future, I could always scale up to a large AC unit.
