new_at_this 
October 26, 2011 17:35 
nusselt number calculation
I'm stuck calculating nusselt number and I don't know what I'm doing wrong.
I have a fully developed flow passing between infinite parallel plates. The flow is then heated by constant temperature plates. I have calculated a nondimensional temperature field theta.
Theta = (TT_w)/(T_inT_w) where T_w is the wall temperature and T_in is the inlet temp.
To find nusselt number I am using the equation Nu=(dtheta/dy)/theta_avg
dtheta/dy is (theta(boundary)theta(interior))/dy
thetavg = theta u* dy
this is giving me all sorts of strange results even for the graetz problem. any ideas
