Air cooled steam condenser

ank59

Hey my problem is related to air cooled condenser

The condenser is for removing 5MW thermal power from steam at 350 C, the pressure is 170 kg/cm2. The average temperature of outside air is 95 C(inlet at 45 C and outlet at 145 C).
the data is as follows:

no of tubes : 182
tube od =25.4 mm
tube id= 20.58mm
no of fins= 196.5 /m
effective length of one tube = 6.074m
fin tip diameter=57.15 mm
material conductivity = 26.57 W/mK

I want to calculate the wall temperature so that condensation heat transfer coefficient can be obtained by Nusselt equation but I am getting a wrong answer again and again, can anybody please help me in this problem. The correct answer is 197.5 C.

Generally the film resistance of steam is takes as negligible so can anybody comment on this, and is there any separate formula for finned tube to calculate the wall temperature.