TWO - PHASE LINE SIZING 1

[Buchi]

Hi guys,

i am performing a two phase line sizing using a specialized software. I discovered that the software used "no-slip mixture density" instead "mixture density" for calculating the erosional velocity. can somebody tell me the rationale for this and the difference between both densities.




Buchi

 

[EGT01]

I think the only way to know why your software used the no-slip mixture density is to review your software documentation. But I suspect either your software is limited to using a no-slip model only or it determined that a no-slip model was appropriate.

The no-slip model used in two phase flow calculations assumes that the liquid and vapor are traveling at the same velocity. The no-slip mixture density then is basically the density of the mixture as if it were a homogeneous mixture of the vapor and liquid fractions.

 

[25362]

As an aside, return pipes from thermo-syphon reboilers are generally sized to achieve linear velocities of about 15 fps i/o to carry over liquid drops as a mist, avoiding slug flow, whilst return pipes from kettle-type reboilers are designed so as to keep the linear velocities below 1 fps i/o to attain just the opposite, namely, minimum liquid entrainment.