6 replies to this topic

[Araboni]

 Dear friends,

I am calculating the actual temperature of the flaring gas from our Vacuum Distillation Tower where a stream of gas (C11H24) at a temperature of 400 C, a pressure of 4.5 barg, enters a flare header with a diameter of 32 inches and a length of 600 meters. Given that the ambient temperature is 48 C, according to heat transfer calculations, on average, the gas temperature drops to 340 degrees at the end of pipe. But this temperature for stress analysis calculations has led to the addition of several loops in the design. Does anyone have any experience in this regard? Isn't the temperature of the pipe wall much lower in practice due to the actual heat transfer with the environment as well as radiation, for example, below 200 degrees? If the temperature drops more in practice , the number of loops caused by the stress analysis calculations will really decrease. I would like to thank you for helping me.

Araboni

Edited by Araboni, Yesterday, 02:29 PM.

[breizh]

Hi,

You may find pointers in the document attached. Probably more in the relevant API>

Breizh 

Attached Files

•  flare.pdf   1.29MB   1 downloads

[Araboni]

Hi Breizh

Thank you for your prompt reply. But this document you attached is saying about the Flare stack radiation. What I need is just confined with the real heat transfer between Flare Header and ambient.

regards

Araboni

[breizh]

Hi,

Check messenger in this forum. 

BTW for better accuracy you should divide your 600 m pipe in multiple segments, not less than 20!

Physical properties of the gas are much affected by temperature and pressure. 

You should perform at the same time heat balance and hydraulic calculation on each segment to calculate (P,T) thus all the corresponding properties.

Note: You did not give much info about the pipe (material), is it insulated or not?

Nothing about the air! velocity?

Good luck

Breizh

Attached Files

•  heat transfer model for above or underground insulated pipe.pdf   718.49KB   1 downloads

[Araboni]

The line material is SA-106 and without any insulation. The Refinery is adjacent to Persian gulf with the max wind speed of 1-5 m/s. 

[breizh]

What about the flow rate of undecane? 

You should submit a excel sheet with relevant information and calculation for review.

We cannot read your mind.

Breizh

[latexman]

What are your objectives?  Will you look at winter conditions too, so you know the entire operating window?  Persian gulf (Bahrain) has got as low as -5^oC.  What about while raining?  It's not frequent, but February and March on average can get 10-15 mm of rainfall.  Are you using commercial software, or calculating yourself?  The inside and outside metal temperatures should be calculable and shown.  I have no idea about your pressure profile.  Is it 4.5 bar_g for a long distance, and you are worried about condensation?  The boiling point of undecane at 4.5 bar gauge pressure is roughly 281^o C. Or, is the 4.5 bar_g short lived?  Good luck to you!