I calculated tube pressure drop using kern method and found the value is 49 kPa, shell pressure drop using bell delaware method with value 989 Pa.

But when I use CFD simulation (in my case Fluent), it showed very different pressure drop between upstream and downstream (not in the nozzle because my calculation doesn't include effect of nozzle, so it's under the nozzle). From CFD it shows pressure drop of 15 kPa and 351 kPa respectively for shell side and tube side.

Is there any wrong in my simulation method or maybe Kern Method and Bell Delaware is not good enough to calculate pressure drop ?

When I compare temperature of my calculation and simulation, it showed almost same value.

Here is my setting :

Boundary Condition : inlet -> mass flow inlet (input mass flow, temperature and normal to boundary), outlet -> pressure outlet (didn;t change anything, just ok), wall-tube -> coupling.

Model : k-epsilon realizable, standard wall, energy on

Method : SIMPLE, Presto!, Green Gauss node based and other than that is first order scheme