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Recirculation Ratio In A Cryogenic Reboiler Condenser


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#1 Supriyo Mukherjee

Supriyo Mukherjee

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Posted 12 March 2015 - 03:40 AM

This Topic I am writing in continuation of the topic which had been archived.
http://www.cheresour...iler-condenser/

 

The topic was ended there.
Going through the topic I found similar example which I would like to put it here so that some people can enlighten with knowledge on this thing.

 

The reboiler condenser vendor gives a recirculation ratio for a bath type reboiler condenser.

 

Which is provided to reduce the risk of hydrocarbon accumulation on condenser core.

The higher the recirculation ratio, it is better. 

I have provided an example of such reboiler in attached excel sheet with all the data's that are available. 

 

So on the safety point of view it is quite clear to me as much higher recirculation ratio would be there lesser would be the chance of hydrocarbon deposition.

 

So here in the example where the recirculation rate in the bath is 10 times the liquid actually evaporated.

 

The thing that still remains uncertain is how we arrive at this recirculation rate or recirculation ratio, like 10:1 in this case. In some cases I have seen this 20:1 or 6:1 in some instances.

This bath reboiling is occurring on the basis of natural convection for sure. So the density diffference is causing the recirculating flow. i.e. density difference is the driving force for the recirculating flow.

 

But still I am not able to understand/figure out the process in which the vendors are calculating/fixing the recirculation flow in these type of exchangers.
I would like to know if someone could enlighten us about the procedure of this design of these bath type exchangers w.r.t the recirculation ratio.

If any data's are required in this case please feel free toa sk I ll provide if I have the data.

 

Thanks and regards,

 

Supriyo Mukherjee

Attached Files



#2 Pilesar

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Posted 12 March 2015 - 10:06 AM

Natural convection circulation results from a balance of forces. Density difference is the driving force because it causes a pressure difference, but the counteracting force to consider is frictional pressure drop. As the bubbles become a larger portion of the stream, the density is lowered, but less mass is contained in the same volume. The flow rate depends on the balance point between the driving force and the resistance. Also consider that the heat transfer is best in the boiling region and not as good in the subcooled or vapor region. The entire system will satisfy the heat flux, flow rate, and pressure drop relationships simultaneously.



#3 Zauberberg

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Posted 12 March 2015 - 11:25 AM

See attached materials and some of the links below.

 

http://tx.technion.a.../LECTURE_08.pdf

http://chem.engr.utc...llation-ch4.pdf

 

Attached Files






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