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

[Boon Jie]

Hi all,

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

 

[BvU]

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.

 

[Boon Jie]

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

 

[BvU]

Adiabatic expansion means no heat transfer; the mass flows from high p to low p and expands.