2 replies to this topic

[Pilesar]

I am looking for guidelines to design annular distributors for shell and tube heat exchangers. I reviewed the recommendations supplied in the HTRI Design Manual (C3.3.4) and the confidential HTRI paper by Niederer (Annular Distributors, 1999.) Is there any annular distributor design method in the open literature published in the last 20 years? It is not that I don't trust HTRI, but I tend to be hard headed when my pre-conceived notions are contradicted. What is the source for the design methodology you use? Does it give similar results to the HTRI recommendations? Have you found the HTRI recommendations too conservative? I am really just wanting more evidence before I settle on my own design method that I feel like I can adequately defend. Thanks!

 

[Bobby Strain]

I don't know what an annular distributor is. Maybe you can give us a sketch?

[Pilesar]

An annular distributor is used to reduce momentum of the inlet fluid on shell side of heat exchanger instead of an impingement plate or impingement rods. They are common on condensers especially. The purpose is to avoid excessive tube vibration caused by the mass flow of inlet fluid concentrated on a small area of the tube bundle. Where momentum is less than 500 lb/ft-s2 at the inlet nozzle, you normally don't need to worry about impingement protection. So it might seem that a properly designed slot area of the distributor would result in a calculated rho v squared of a little less than 500 lb/ft-s2. But because the fluid does not have uniform velocity through all of the slots, some design methods result in large slot areas with the calculated rho v squared an order of magnitude lower. When the required slot area becomes too large, you may have to change other dimensions of the exchanger (e.g. length, diameter, baffle spacing, etc) to properly fit the annular distributor. It bothers me to have to change my exchanger design just because of an annular distributor design method that I don't fully understand. I am not above 'bending' design requirements when expedient, but I will only do so when I think I understand the rationale and the underlying calcs behind the 'rules' and can justify an exception to standard practice on logical and reasonable terms.