Heat Transfer of a Dewar Nitrogen Container

In summary, the conversation discusses the attempt to calculate the heat transfer and boil off rate of LN2 in a Dewar container. The speaker has used the heat conduction formula for a cylindrical object and the heat conduction coefficient, as well as the latent heat and density of LN2. However, despite plugging in the numbers, the calculated boil off rates are too low. The speaker is seeking help to determine what they may have done wrong or forgotten in their calculations.
  • #1
rikku95
1
0
TL;DR Summary
Heat Transfer of an Deware Nitrogen Container
Hello guys, :smile:

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.

Unbenannt.png
1565890522802.png


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

1565892075765.png


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

1565892009981.png
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
1565892134434.png


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 :cry:
 
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  • #2
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.
 

1. What is a Dewar nitrogen container?

A Dewar nitrogen container is a type of insulated container used to store and transport liquid nitrogen. It is designed to keep the nitrogen at a very low temperature for extended periods of time.

2. How does heat transfer occur in a Dewar nitrogen container?

Heat transfer in a Dewar nitrogen container occurs through three main mechanisms: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between two materials. Convection is the transfer of heat through the movement of a fluid, such as air or liquid nitrogen. Radiation is the transfer of heat through electromagnetic waves.

3. What is the purpose of the insulation in a Dewar nitrogen container?

The insulation in a Dewar nitrogen container serves to minimize heat transfer between the liquid nitrogen and the outside environment. This helps to maintain the low temperature of the nitrogen for longer periods of time.

4. How does the design of a Dewar nitrogen container affect heat transfer?

The design of a Dewar nitrogen container plays a crucial role in controlling heat transfer. The container is typically made of multiple layers of materials, with a vacuum between the layers to prevent conduction and convection. The innermost layer is usually made of a reflective material to minimize radiation heat transfer.

5. How can I maximize the heat transfer efficiency of a Dewar nitrogen container?

To maximize the heat transfer efficiency of a Dewar nitrogen container, it is important to handle and store the container properly. This includes minimizing the amount of time the container is left open and ensuring it is not exposed to direct sunlight or other heat sources. It is also important to regularly check and replace any damaged insulation to maintain its effectiveness.

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