Quote:
Originally Posted by nolonger 
Doesn't a lower W/mK mean it takes less heat to produce a temperature difference? That would mean silver is less resistant to temperature changes, therefore being a better heat conductor.
Quote:
Originally Posted by K404
Here is a chart showing thermal conductivity Vs (cryogenic) temperature for aluminium
http://reference.lowtemp.org/alkappa.html
Yea, it's a different metal but the important bit is to know that thermal conductivity changes as a function of temperature. Different metals have different curves. Very few charts are linear, some appear VERY random.
Just because silver is better than copper at +50c or similar, means truely NOTHING for LN2 or LHe.
Somewhere out there (i'm looking) there are charts for different grades of silver and copper.
I am *reasonably* sure that the charts will show that the performance between the two is close enough that there is absolutely no reason to make a silver LN2 pot.
So... to answer your question, no-one has made one because of money
EDIT: GOT IT!
Chart for copper:
http://www.efunda.com/materials/elements/TC_Table.cfm?Element_ID=Cu
Chart for silver:
http://www.efunda.com/materials/elements/TC_Table.cfm?Element_ID=Ag
At -196c (77K) (the charts have an entry for 80K so i'll use that)
Silver: conductivity of 471W/mK
Copper: conductivity of 557W/mK
So.... with LN2 silver is performing WORSE and costs a lot more. If we were to use LHe, silver is pretty terrible.
Here is a chart showing thermal conductivity Vs (cryogenic) temperature for aluminium
http://reference.lowtemp.org/alkappa.html
Yea, it's a different metal but the important bit is to know that thermal conductivity changes as a function of temperature. Different metals have different curves. Very few charts are linear, some appear VERY random.
Just because silver is better than copper at +50c or similar, means truely NOTHING for LN2 or LHe.
Somewhere out there (i'm looking) there are charts for different grades of silver and copper.
I am *reasonably* sure that the charts will show that the performance between the two is close enough that there is absolutely no reason to make a silver LN2 pot.
So... to answer your question, no-one has made one because of money
EDIT: GOT IT!
Chart for copper:
http://www.efunda.com/materials/elements/TC_Table.cfm?Element_ID=Cu
Chart for silver:
http://www.efunda.com/materials/elements/TC_Table.cfm?Element_ID=Ag
At -196c (77K) (the charts have an entry for 80K so i'll use that)
Silver: conductivity of 471W/mK
Copper: conductivity of 557W/mK
So.... with LN2 silver is performing WORSE and costs a lot more. If we were to use LHe, silver is pretty terrible.
Doesn't a lower W/mK mean it takes less heat to produce a temperature difference? That would mean silver is less resistant to temperature changes, therefore being a better heat conductor.
Air has a Thermal Conductivity of 0.024 W/mK at 25C. By your logic we should OC without any heatsink.
