Temperature drop of the system simulation
 

Hello,

I am working on one problem where i have to find the system temperature drop(inet-outlet). i am considering conduction, natural convection and radiation for my problem. I ran this case for 3 diffrent conditions, i.e. say at inlet mass flow rate 12 kg/min and flow temp. 565 K , 8 kg/min at 419K and 5kg/min at 364K.

After my analysis is over i found that the temperature drop in all the 3 cases is almost same. so i am not able to figure it out how its happening. the ambient temperature for all the 3 cases is same,i.e 25deg. C.
According to my understanding first case should have the highest temperature drop.
Please someone explain it to me.
Thank in advance.
regards,
Sonu.