Heat Transfer in rectangular duct
 

hello everyone,

I have calculated heat transfer coefficient (61 w/m^2k) for rectangular duct with the air flow 13 m/s.Flow is vertically downward.

Duct size : Width : 8 mm
Height :125 mm
Length:246 mm
I am using fluent solver for this.
I have given Velocity inlet boundary condition at inlet with 13 m/s & 25 degree temperature and heat transfer coefficient (61 w/m^2 K) to both the wall.

It gives only 5 degree temperature rise but my analytical calculation shows 15 degree temperature rise.

I have also used reference values for this.

I am attaching image for the reference.

Please help me anyone.:confused::confused::confused::confused::