Why do I observe ice formation on the exterior of this pipeline?

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Discussion Overview

The discussion revolves around the phenomenon of ice formation on the exterior of a pipeline connecting a compressor to a reactor, particularly in the absence of flow. Participants explore potential explanations involving thermodynamic principles and pressure dynamics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the ice formation could be related to the small opening of the pressure control valve, which may create a pressure differential leading to a temperature drop.
  • Another participant argues that there should be no opening at all, proposing that inserting a regular valve would eliminate the phenomenon, while agreeing that adiabatic expansion is relevant.
  • A different participant clarifies that there is indeed a small opening in the form of a bypass line, which allows for continuous supply to maintain pressure in the reactor, complicating the application of adiabatic expansion due to ongoing mass transfer.
  • One participant reiterates that adiabatic expansion involves no heat transfer, emphasizing the flow of mass from high to low pressure and its expansion.

Areas of Agreement / Disagreement

Participants express differing views on the role of the pressure control valve and the applicability of adiabatic expansion, indicating that multiple competing explanations remain without consensus.

Contextual Notes

There are unresolved assumptions regarding the specifics of the pressure control valve's operation and the conditions under which adiabatic processes apply, as well as the implications of mass transfer in this context.

Boon Jie
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Hi all,

1579164290780.png

I would like to ask why is there ice formation on the exterior of the pipes between compressor to reactor when there is no flow passing through
or what kind of phenomenon is this?

My colleagues have suggested PV=nRT and adiabatic process as the possible reasons but I still feel that something is amiss

It could be the small opening of the pressure control valve that let's pressure sip from buffer vessel into reactor that causes the pressure differential and maybe temperature drop(?)

Else, I'm not sure how this freezing outside pipeline occurs

Please advise,
Thank you
 
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Boon Jie said:
It could be the small opening of the pressure control valve
There should be no opening at all. Insert a regular valve to close off the supply altogether and the phenomenon should disappear.

Colleagues are correct about this adiabatic expansion issue.
 
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Apparently they do have a small opening the valve in the form of a bypass line, as a sort of pressure regulation using the small opening...because the reactor pressure will drop because of reaction, the small opening acts as continual supply of C2H4 as to maintain/ increase pressure in the reactor

But adiabatic expansion only applies to no heat / mass transfer, which in this case there is continual mass transfer across the valve/ pipeline from buffer vessel to the reactor
 
Adiabatic expansion means no heat transfer; the mass flows from high p to low p and expands.
 

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