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# Need Help - Cooling Flat Plate with LN2

## Need Help - Cooling Flat Plate with LN2

(OP)
I have a flat plate (~16in^2) that has enough heat input to get upwards of 500°C during processing. I have been asked to look into cooling it with LN2. I don't even know where to begin. Some of my questions are:
How do I provide a specific flow rate of LN2 at pressure to cool surface?
What kind of nozzles do I use with LN2?
We use quite a bit of LN2 in other processes, is LN2 a cost effective means of cooling in a production environment - semi-continuous process?
What are some good online resources for ideas and hardware for designing LN2 cooling processes?

"To be or not to be, that is the question" - William Shakespeare via Hamlet

### RE: Need Help - Cooling Flat Plate with LN2

What you've provided is not enough to answer the question. These two questions need to be answered to proceed:

What is temperature is the plate desired to be during production?

What is the power dissipation that's heating the plate?

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Need Help - Cooling Flat Plate with LN2

LN may let you reach colder temps, but you will not be able to remove as much heat as you can with water.
The amount of heat that you need to remove in what time period is the important info.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: Need Help - Cooling Flat Plate with LN2

Is the plate material suitable for cryogenic temperatures?

### RE: Need Help - Cooling Flat Plate with LN2

The specific answer is that it will most likely suck for any serious cooling application

Heat of vaporizations (kJ/kg):
water: 2257
nitrogen: 199

So, water is basically 11x more useful for cooling things above 100C

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Need Help - Cooling Flat Plate with LN2

IR, and you left out the heat capacity as well.
LN is only a good option if you need very low temps, and you have to vent into a controlled space.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: Need Help - Cooling Flat Plate with LN2

"you left out the heat capacity as well"

True, that, but steam isn't really that much more useful that gaseous nitrogen from a cooling perspective. Once below 100C, water is marginally better than LN2, 293 kJ/kg(70C delta temp) vs. 199 kJ/kg, but, presumably, water is much cheaper to condition for cooling.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

### RE: Need Help - Cooling Flat Plate with LN2

Earth to elfman?

COME IN elfman!

Keith Cress
kcress - http://www.flaminsystems.com

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