How Can I Correctly Calculate Wall Temperature in an 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.

 

[nbryan5]

To calculate the wall temperature, you need to use a combination of thermal resistances in parallel and series. The thermal resistances in series are the resistance due to conduction through the tube wall, the resistance due to conduction through the fin material, and the resistance due to convection between the outside surface of the fin and the air. The thermal resistances in parallel are the resistance due to conduction through the fin material and the resistance due to convection between the outside surface of the fin and the air. Combining all of these resistances together will give you the total thermal resistance from the steam side to the air side. You can then use the known values of the steam side temperature and the air side temperature to calculate the wall temperature using the equation: Wall temperature = (Steam side temperature + Air side temperature) / 2 Once you have the wall temperature, you can calculate the condensation heat transfer coefficient using the Nusselt equation.