2 replies to this topic

[Supriyo Mukherjee]

Dear All respected members,

I am designing a bath vaporiser for cyogenic fluids namely liquid oxygen and liquid nitrogen.
Here we have around 6000 NM3/HR Liq. nitrogen at 10 bar A pressure. to be vaporised in a vaporiser bath.
we have liquid nitrogen tubes coiled in the bath of water, which is maintained at an temperature of around 60-70 degree celcius in my calculations.

When we are calculating the heat transfer coefficients of this type of bath vaporiser, I am using the shell and tube methodologies in Kern considering water temperature entering at 70 leaving at around 60 degree celcius.
But on the water side coefficient calculation i have calculated using natural convection methodology.

What i am concerned about is the area of heat transfer coming from the methodology is sufficient or not.
At present I m using an extra 20% margin.

Also as I m using the methodology of kern which is for shell and tube considering counterflow, I am not pretty much sure wheather these method is correct or not.

I would like to have some guidance regarding this from you.

Please let me know if any other information is required.

Regards,

supnit

[Bobby Strain]

So, why are you designing these vaporizers rather than buying them from a reputable vendor?


Bobby

[Art Montemayor]

supnit:

Bobby Strain brings up a very sound point in the way of a question.

If you have no experience in designing and fabricating a cryogenic vaporizer using water as the heat source, you are headed for a lot of trouble and failure.

The possibility that the end product of your work effort becoming a large chunk of super-cooled ice is rather high. You intend to introduce liquid nitrogen (LIN) at -273 ^oF into a water bath that is at +70 ^oC (a driving force of 431 ^oF) and “maintaining” the water at +70 ^oC. I can’t imagine how you intend to control the water temperature using natural convection. The moment the water touches the coils, it will freeze into solid ice and only the “natural” convection currents in the water will try to melt the ice that will start to sub-freeze and add more layers of solid to the base ice. I believe that unless you use a pump and circulate sufficient water around the coil, you will wind up with a solid block of ice.

Additionally, the flow rate of 6,000 Nm3/hr is a huge amount of LIN. Is this correct? --or a typo error?