How can one quickly estimate the additional pressure drop to be introduced with more tube passes?

How can one quickly estimate the additional pressure drop to be introduced with more tube  passes?
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1 Answer

Answer :

When the calculated pressure drop inside the tubes is underutilized, the estimated pressure drop with  increased number of tube passes is new tube DP = DP x (NPASS/OPASS)3 Where NPASS = New number  of tube passes. OPASS = Old number of tube passes this would be a good estimate if advantage is not  taken of the increase in heat transfer. Since the increased number of tube passes gives a higher velocity  and increases the calculated heat transfer coefficient, the number of tubes to be used will decrease.  Fewer tubes increase the new pressure drop. For a better estimate of the new pressure drop, add 25% if  the heat transfer is all sensible heat. Source: Gulley Computer Associates
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