[conversionlab]

Hi, I'm very new here, and as you'll likely see, know nearly nothing about what I'm talking about.  So, if I say something stupid, I apologize.  I welcome all comments, questions, and any assistance you can provide.

I am interested in developing a relatively small cooling device, using liquid nitrogen as the coolant.  From my very minimal research (Wikipedia) I have learned that liquid nitrogen has a boiling temperature far below regularly attainable cold temperatures, and that it insulates itself with its own gases when it comes in contact with a warmer object - so likely any object.

What I'm interested in learning is, how can I:

• passively (i.e. without interaction or electricity) keep nitrogen at a warmer (room) temperature?
• lower its temperature to below zero celsius on demand
• keep it properly insulated to prevent condensation when it reaches the lower temperature

Any help, or a fingers pointed in the direction of resources that I can hopefully understand, would be greatly appreciated.

Thanks 

[curiouscat]

passively (i.e. without interaction or electricity) keep nitrogen at a warmer (room) temperature?

A Dewar flask?

keep it properly insulated to prevent condensation when it reaches the lower temperature

If that T,P says liq. on a phase diagram you can't prevent it.

[conversionlab]

A Dewar flask?

Thanks curiouscat, I'll look into the materials used to make the Dewar flask.

If that T,P says liq. on a phase diagram you can't prevent it.

I'm sorry, this means nothing to me.  I'm chemically illiterate.  What is T,P and liq and phase diagram in this context?

Thanks.

[billnotgatez]

This forum tries to help people by teaching them now to derive answers for themselves.

WIKI and GOOGLE are good resources

http://en.wikipedia.org/wiki/Phase_diagram

is one example

T.P. is triple point and the above link talks about that
liq means liquid as in liquid phase

It is probably better to purchase a Dewar flask than make one

Also remember that there are dangers when using liquid Nitrogen

you might GOOGLE liquid nitrogen dangers
http://webs.wichita.edu/facsme/nitro/safe.htm

[Arkcon]

They sell these sorts of thing for people who overclock their computer CPUs to a great degree.  If that is your application, or your application would fit in a similar sort of physical space, you might just want to Google for those, and consider buying it.  It really does make more sense than researching how a Dewar flask is made, considering a Dewar flask is simply a high tech, more efficient, Thermos bottle.

[conversionlab]

@billnotgatez and @Arkcon

Thanks, I have been googling and researching, and have checked out those links and learned alot, so thank you for taking the time.

Unfortunately, there is no solution for my requirement that is purchase-able, which is why I am setting out to create the solution.  I'm well versed in cooling for computers, as both my systems are currently watercooled.  However, these cooling systems are bulky at best, and highly dependent.  I am trying to create a very portable, very efficient system that can occupy minimal space, yet provide a very safe yet very cold temperature.  I have looked into all types of cooling systems, including refrigeration, CPU cooling, and even systems like those built into portable coolers.  From this research I have realized I need to start earlier in the development stage as none of those products are nearly small enough.

So, now I'm here.  I have no problem researching, and it is not only absolute answers I seek outright, but also assistance.  If the answers I receive are links to resources, I am as grateful for those as I am for answers that would lead me to a direct solution.

So again, thank you for your time and assistance.  It's greatly appreciated.

P.s.  Arkcon, yes I had already taken in much on the dangers of liquid nitrogen, including the link you provided.  But, thanks for reiterating it.

[vmelkon]

There is a small device called a thermo electric cooler, also called Peltier cooler
http://www.ebay.com/itm/New-2-PCS-TEC1-12715-TEC-Thermoelectric-Cooler-Peltier-12V-40mm-/160654915658?pt=LH_DefaultDomain_0&hash=item2567c7784a

It runs on electricity. They tend to drop the temperature by about 25 °C relative to room temperature.
The down side is that they consume a lot of current.