Heat Exchanger Bank PRV Losses

[RVAmeche]

Hi All,

I'm trying to find some source that discusses how to handle manifolded heat exchangers protected by a single relief valve. We currently have 2 pairs of heat exchangers mounted nozzle to nozzle, with a short section of pipe connecting the pairs. The PRV is located off this connecting pipe.

When trying to analyze the PRV inlet loss, does one have to consider the loss of the 1st exchanger's relief rate through the flow of the 2nd heat exchanger towards the relief valve? If not, why? I've attached a quick sketch showing my thought. The only reference I can find is a page excerpt from a book on Google saying you start at the closest equipment.

 

[EmmanuelTop]

"Inlet losses" = pressure loss between the system and the PSV. This does not include the system itself.

The system of exchangers and the manifold is hydraulically connected and hence behaves as a single containment/system. "Inlet losses" refer to head loss between the system discharge flange (at the exchanger manifold) and the PSV inlet flange. The manifold is a part of the system and no friction losses should be accounted for within the system.

A similar example could be e.g. relief from the overhead line of a distillation column. In the moment of relief, the overhead line pressure can be quite lower than the tower bottoms pressure (depending on the relief flow), but that does not mean that inlet losses should be calculated all the way down to the tower bottom section.


Dejan IVANOVIC
Process Engineer, MSChE