Heat Transfer of a Dewar Nitrogen Container

[rikku95]

TL;DR

Heat Transfer of an Deware Nitrogen Container

Hello guys,

So like the Titels says I am Trying to get an Approximation of the Heat Transfer which ocours in a Deware container. Unfortunately all my calculations so far seem to suggest way to low Boil off rates for my Container its just to efficient, here is a summary of my Attempts.

First of all I got myself the Heat Conduction formula for an Cylindrical Objekt and for a Circle and my heat conduction coefficient.

After i calculated the Heat Conduction in Watts,the next step was the Latent Heat of LN2 And the Density of LN2 which is it ;

So the Boil off of LN2 form -196 to 21C° in watts is

So that´´ s it, after i plug my numbers in i always get way too low Boil off rates for my containers.What did i do wrong?What did I forget?

Heres an Example

These are Meters yes, so at an outer radius of 1,05 m and an height of 2 meters only Produces 1,8L/day, i don't think so.

Please help me i am in Great pain

 

[JBA]

During boil off your vessel Ti will remain constant at -196C because your relief valve pressure setting will keep the vessel pressure constant during that process, so your calculated heat transfer rate into the vessel will also remain constant at that Ti - Ta value.