Heatsink Cooled In Liquid Nitrogen
Heatsink Cooled In Liquid Nitrogen
(OP)
Hello,
Can anyone offer advice on the design of a finned heatsink that will be submerged in liquid nitrogen to cool an analytical instrument? I am a mechanical engineer with minimal thermal experience and I am designing a coldfinger or heatsink that is attached to a heat source. The coldfinger must bring the heat source (block) temperature from ambient to minus 170 degrees Celsius and then 60 watts will be applied to the heat source in order to bring the temperature up to 200 degrees Celsius.
Can you recommend equations, values for heat transfer coefficient of liquid nitrogen or a design approach? Do I simply use the convection heat transfer equation Q=hA(delta-T)? Where A is the surface area of the coldfinger exposed to liquid nitrogen?
Thanks,
Bob
Can anyone offer advice on the design of a finned heatsink that will be submerged in liquid nitrogen to cool an analytical instrument? I am a mechanical engineer with minimal thermal experience and I am designing a coldfinger or heatsink that is attached to a heat source. The coldfinger must bring the heat source (block) temperature from ambient to minus 170 degrees Celsius and then 60 watts will be applied to the heat source in order to bring the temperature up to 200 degrees Celsius.
Can you recommend equations, values for heat transfer coefficient of liquid nitrogen or a design approach? Do I simply use the convection heat transfer equation Q=hA(delta-T)? Where A is the surface area of the coldfinger exposed to liquid nitrogen?
Thanks,
Bob





RE: Heatsink Cooled In Liquid Nitrogen
Here's an excellent article on how to do that, at least for air cooling. Maybe you can apply it to liquid nitrogen. It also has a good list of references:
http:/
Or, if you have access to CFD software you can model it fairly easily.
ko (www.ecooling.biz)
RE: Heatsink Cooled In Liquid Nitrogen
A large number of very fine Cu fins is the most effective approach. Soem of the ones available for aftermarket computer use use skived fins, they are literally shaved from a block of Cu.
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RE: Heatsink Cooled In Liquid Nitrogen
Should I be calling it a coldfingeras opposed to a heatsink?
Anyways.....Is there any advantage to maximizing the mass of the heatsink so it will store/maintain a cool temperature to help increase cooling rates when energy is applied?
~Bob
RE: Heatsink Cooled In Liquid Nitrogen
Greater mass will slow the temperature change, if that's what you're after. Once at steady state, the mass doesn't matter.
ko (www.ecooling.biz)
RE: Heatsink Cooled In Liquid Nitrogen
TTFN