Two-pass shell configuration

This would make it seem that the two-pass shell configuration is inherently more efficient than the ordinary single-pass shell exchanger. And it is, in theory. Then why do we see so few of these exchangers in service ... 

This would make it seem that the two-pass shell configuration is inherently more efficient than the ordinary single-pass shell exchanger. 

I have seen new exchangers of "two-pass shell" configurations work well when new. However, with time and typically after a turnaround, performance has been degraded, due to leakage around the cross-flow (longitudinal) baffle. 

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See also in sourсe #XX -- [ ]

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