Ambient Vaporizer - Capacity flow Estimation

[VPbris]

Hi,

Ambient Vaporizers are equipment used to vaporize liquified gases. (Figure:

https://www.praxairdirect.com/Indus...anks-and-gas-systems/Ambient-Vaporizers.png).

(Input temperature is about -180C)

I have some design examples and am trying to estimate flow capacity of each in terms of Nm³/hr. Of course this value will change depending on the enviroment which it is installed. Also, there will be some ice formation due to gas expansion which will decrease heat transfer.

Does anyone know a good method I can use to aproximate the flow values?

I also have another question. I've seen two types of design.
1- Flow is divided into N segments of X thin pipes and then collected into a single output
2 - All the flow passes through the N*X thin pipes
Which one is more desirable and why?

 

[Caloooomi]

Best bet would be to get a brochure and scale based from that. Most ratings I have seen is based on empirical knowledge and more experienced people in IG will just know roughly if the vaporiser is suitable or not...

You would usually rate based on number of continuous operating hours, say 1, 2, 4, 8, 16, 24 hours etc, and you would gradually decrease the rated capacity of the unit. You may have 1000 Nm3/hr for 1 hour run time OR 700 Nm3/hr for 8 hours, for example. 8 hours is standard for switching between banks of ambient vaporisers.

As for which type is more desirable, it really depends on what is needed by the process. High flowrate and low pressure drop, a single pass would be better. They won't be as resilient to ice growth though as it will collect in one place - at the bottom of the unit.

 

[victorpbr]

Hi Caloooomi,

Yes, I agree with on that. That's how I design them, I got some proven designs and calculated the FlowRating/FinArea for some different models, not a linear relation though. Changes considerably depending on the flow rate, that why I am interest on understanding the method to at least estimate these values. Thank you for your inputs.

 

[chicopee]

Get brochures from the supplier since the supplier will be submitting the size of the vaporizer based on your flow rate consumption.

 

[Caloooomi]

Well it's tricky as each vendor's rating will be different due to how they construct them. You could have a piece of 8 fin extrusion from several vendors and the SA / length ratio will be different for all of them.

Look for the older Thermax vaporiser brochures as they would have standard ratings on them in SCFH/ft2.