Saturday, July 21, 2012

CryoBUG Totally Stable at -156°C

Today I retested the CryoBUG unit with the following refrigerants in the charge.

R-600a (Iso-Butane)
R-170 (Ethane)
R-14 (Tetrafluoromethane)

Note: This would be the first time utilizing Iso-Butane instead of N-Butane.

The results were better then expected, allowing the unit to get down to -156°C, while still exhibiting stable temperatures and pressures.

TC Meter connected to Evaporator Feed

Test Data

In order to get a better feel for what the unit was doing at various points across the system, I have included a diagram that hopefully makes this a bit easier to see.

As can be seen, there is a very small temperature spread across the evaporator, being on the order of 4 degrees. The estimated evaporator load should be approximately 10 watts, which is primarily due to insulation losses.

The proposed oil control system shown may not be necessary, since I haven't seen any signs of oil freeze-out problems, which is most likely the result of utilizing two hydrocarbon based refrigerants in the charge, thus having better oil solubility than freons.

Switching to the Iso-Butane has also apparently cured my refrigerant freeze-out problem as I had expected.

During this test I took the opportunity to incorporate smaller cooling fans, going from two 100 CFM models down to a couple of smaller 41 CFM types. This allowed me to better gauge what will be needed for air flow when I build the more finalized version of this unit. As can be seen by the liquid line and discharge temperatures, the smaller fans still did the job (ambient air temperature in the room was about 22°C).

Technology Update

My experiments have shown that a very simple single-stage autocascade refrigeration system can reliably achieve temperatures in the cryogenic range. And furthermore that this can be accomplished with the use of open technology, no longer under the restrictions of patent protection or patent pending. Although obviously there are some trade secrets involved, such as HX and cap tube sizing, and of course the exact formula for the mixed refrigerant charge. Trade secrets that are currently held by Mytek Controls (aka; Michael St. Pierre). But none the less, this does not present any legal obstacle for anyone else wishing to exploit this technology on their own. And I encourage others to do so in the spirit of competition.

I say all this to discourage what I will call the practice of filing BS Patents. These would be patents that should have never been issued, which are nothing more then taking what would be common sense derivatives of previous inventions, and trying to monopolize on their use.

I would also like to acknowledge Andrija Fuderer for his great contribution and inspiration, as well as for providing the foundation that CryoBUG is based upon.

Posted by: Leonard Barden, 

"Andrija Fuderer, who died aged 80 last month, was an eminent chemical engineer and inventor with more than 50 patents to his name."

Link to Full Article: 
Andrija Fuderer, a gifted player and all-round talent, has died aged 80...


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