TEMA Shell Entrance Area Calc with Impingement Plate

[lizking]

Does anyone know how the TEMA shell entrance area calc (RGP-RCB-4.621, 4.622) is done when the impingement plate is located inside of the inlet nozzle (i.e. a circular disc supported by cross-braces in the nozzle I.D. just outside of the shell I.D.)?? This arrangement is not represented in the diagrams. Would you assume that there is no impingement plate?

 

[Christine74]

TEMA doesn't address this design so I'm not sure how to answer your question, but some manufacturers install impingement plates inside of the shell nozzle is so that they don't have to eliminate any tubes. See Fig. 2 here:

http://www.process-heating.com/CDA/Archives/3864ec343a268010VgnVCM100000f932a8c0____

I generally consider this a poor design because of the high localized velocities (vibration potential) and poor use of pressure drop.

-Christine

 

[lizking]

Christine, my thoughts exactly; I believe the annular flow characteristics actually reduce the "shell entrance" area as TEMA defines it. But tough to quantify. Thanks

 

[srfish]

The impingement plate is located inside the large end of a piping reducer. The plate is at least as large as the small end of the reducer. The flow area around the plate is usually larger than the flow area of the small end. A typical impingement protector is a 6x10 size.

For lack of any method of calculation, you could calculated the area around the plate and then calculate from this an equivalent nozzle diameter to use in the TEMA equation.