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Saturday, December 17, 2011

CryoBUG's first test run

Yep it's time to take this puppy from concept to reality. Luckily I didn't run into too much trouble assembling all the pieces, and in the next series of pictures you can see how it turned out (please keep in mind that this is essentially a bread board prototype).

Original AC Evaporator being used as Air-Cooled Condenser

Insulation of HX Stack Nearing Completion


Insulation Completed and Vapor Barrier Sealed

Side View showing Fred Flintstone style fan shroud

For the initial charge I decided to mimic what Fuderer had done with R-12 and R-14, only in my case I used R-134a in place of the R-12 (gotta keep it environmentally friendly). The proportions were 50/50 at approximately 100 grams per refrigerant. Static balance pressure = 205 psig. Start-up peak pressures = 14/307 psig (suction/discharge).

Air cooling of the condenser is being handled by two fans I had in my junk box, so I'm not exactly sure of the CFM, but I do believe they are close to 100 CFM each.

In about an hour the unit had achieved -100°C average temperature across the evaporator. After two hours the unit seemed to be fairly stable and was roughly about -109°C, with pressures of 25/223 psig.

Stabilized Evap-Out (green) and Evap-In (blue) after 2 hours (both readings are in celsius -- label incorrect)

The compressor appeared to be quite comfortable, with a discharge temperature of +57°C, and although a bit warm, I could rest my hand on top without too much screaming (actually no screaming). Current draw for 115 VAC operation = 2.5 amps (this includes the fans).

Based on some of the other inter-stage temperatures I was seeing, I do believe that I would do better with more R-134a, and less R-14. Perhaps a 60/40, or even 70/30 ratio might work out better. This will have to be investigated in additional tests before I start getting into adding any Argon to the charge. but no matter what, it really is quite impressive that such a simple system with only two refrigerants can produce these results. Fuderer really knew his stuff back in 1965.

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