Okay, I went to the gas distibutor and refilled my CO2 bottle. Now I'm going to build a block to run CO2 through, and see if I can get the -78F. :)
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Okay, I went to the gas distibutor and refilled my CO2 bottle. Now I'm going to build a block to run CO2 through, and see if I can get the -78F. :)
First it went great.. I had a minus78F to a minus 80F block (evaporator)... but then the ice (dry ice) started to build up in the evaporator, and as the evap pressure rose, so did the temp :(
I tried restricting the outlet to reduce the formation of the ice (increase evap press.), but as I did so, the realized temperature increased also... at least I tried it :rolleyes:
Maybe I need a CO2 TEV :D
Nice idea.... poor results.... I'll get some nitrogen, next. :D
PS: Now I'm driving the overclockers crazy.
It just may happen some day... :) Perhaps fortunately for us valve manufacturers, there aren't too many engineers excited about designing trans-critical refrigeration systems. :)Quote:
Maybe I need a CO2 TEV :D
BTW, triple point for CO2, according to the ASHRAE Fundamentals Handbook, is -69.8°F (60.4 psig). You'll have to keep your evap pressure/temperature above this point to prevent dry ice formation... :)
Liquid nitrogen would really open up things up to low temp refrigeration... :) Its triple point is -346°F (1.82 psia) according to the ASHRAE Fundamentals Handbook.
If you're really going to get serious, try liquid helium. -455.75°F (0.704 psia) triple point. This ought to turn an Intel 8088 into a Cray computer... :D
Cray computer LOL
Quote:
Originally posted by Prof Sporlan
BTW, triple point for CO2, according to the ASHRAE Fundamentals Handbook, is -69.8°F (60.4 psig). You'll have to keep your evap pressure/temperature above this point to prevent dry ice formation... :)
Hmmmmm, perhaps an EPR? :rolleyes:
Simple CO2 phase diagram
I am also tinkering with the idea of using CO2 in a cascade. The main problem is it's triple point of -56C/-78F. Staying above this point doesn't make sense; a cascade using R134a in the high stage and R507 (or maybe R410A) in the low stage should be able to reach those temperatures also.
Thus, the question is: how to expand CO2 into an evaporator at 1-2 bara (15-30psia), without the dry ice blocking the expansion device? And then the second big problem: how to efficiently transfer the heat to the metal walls of the evaporator?
Absolutely! Keep evaporator pressures on a CO2 system a comfortable distance above 60 psig, and you won't make dry ice. Not sure you will find many epr manufacturers who will readily warrant their products on such a system, though... :)Quote:
Hmmmmm, perhaps an EPR?
Unfortunately, when you expand liquid CO2 below triple point pressure (60.4 psig), you will make dry ice.Quote:
Thus, the question is: how to expand CO2 into an evaporator at 1-2 bara (15-30psia), without the dry ice blocking the expansion device?
The Prof isn't an expert on CO2 refrigeration, but he sees significant problems attempting to evaporate CO2 in a refrigeration system below -70°F. In his humble opinion, there are easier ways to design low temp cascade systems. :)Quote:
And then the second big problem: how to efficiently transfer the heat to the metal walls of the evaporator?
Prof., should you know that I would never make such a claim (warranty)? If you wonder... NOT. :pQuote:
Originally posted by Prof Sporlan
Not sure you will find many epr manufacturers who will readily warrant their products on such a system, though... :)
Mind you, that I am merely expelling the CO2 to atmosphere. "Triple Point" is an interesting term, which I have never encountered before, though I believe the diagram submitted by DaBit explains it! :)
Thanks, gentlemen.... I learned something (and I don't say that like I know anything) :p
I'm considering the capability of the R-404a to reach near -60F, and the potential for the -67F of the CO2, in consideration of, I guess the enthalpy, and the amount of CO2 expended to handle the 120W +/- load. I will reference the appropriate information to to determine the difference in btu/lb of the CO2 vs. R-404A. I may actually be in the process of demonstrating the efficiency of mechanical compression cycle refrigeration?
:)
There are two saturated states that are noteworthy. One is the critical point. Here, the liquid and vapor phases become indistiguishable. This is the point on top of the P-H dome.
The triple point is the saturated state where the solid, liquid and vapor phases are in equilibrium. This is the "bottom" of the P-H dome.
The bottom of the P-H dome for most substances used as refrigerants is at a very low pressure, and not even a concern for those designing vapor compression refrigeration units. CO2 is an exception. :rolleyes:
Quote:
Originally posted by Prof Sporlan
[B]Unfortunately, when you expand liquid CO2 below triple point pressure (60.4 psig), you will make dry ice.
I already was afraid of that. Physical laws cannot be broken.
Well, there are only a few reasons why 'we overclockers' consider using CO2: it is available to us, it is affordable, and it is doable to build a 2-stage cascade with it. Stuff like R508B is both not available and even if we could get it, it is extremely expensive.Quote:
The Prof isn't an expert on CO2 refrigeration, but he sees significant problems attempting to evaporate CO2 in a refrigeration system below -70°F. In his humble opinion, there are easier ways to design low temp cascade systems. :)
My preferred low-temp refrigerant for overclocking purposes is ethane. But I had a price quote of $185 excluding VAT, safety fees and transport fees for only 50g (~ 2oz) in a lecture bottle. But still, ethane has some nice properties.
Sorr I'm new.
i need information on how to calculate a evaporator coil for a block ice machine
Regards
Jose
If you use Helium remember to nail the compressor down,. :DQuote:
Originally Posted by Prof Sporlan