NEM Type can not be designed in PV ELite as single model.You have to Design as below
1) Model Tubesheet with confirguration as " Both side integral, TEMA -N"
Run the file & get tubersheet thickness.
2) Save the same model & change the Tubesheet type as " Integral channel side , TEMA-M" Get the thichness.
While submitting design report , Combing both tubesheet report.
Regards
Sajit Patel