convection heat transfer coefficient
 

There is an expert parameter so the h is referenced to a bulk temperature you define. Search the forum to find it.

Alternately you can use the wall heat flux variable available in the post processor and your own reference temperature and work it out. You could define it as a variable and have it available for post processing.

Glenn's second suggestion is often much more useful. The problem with the expert parameter is that the bulk temperature has to be constant (not an expression as to pull a different bulk from different locations). Using his latter suggest allows bulk temperature to be pulled from CFX in a manner consistent with text books.

Thanks for your reply
Please explain more

h=q''/(Twall-Tbulk),

Tbulk will vary along the channel length

You can define Tbulk to be anything you like, and it does not need to constant. If you want it to vary along the channel length then make Tbulk a function of position and calculate h from that.

Define a new variable in CFD-Post, defined as CEL expression Wall Heat Transfer/(T-Tbulk). Then you can define Tbulk as a constant (eg 280[K]), or as a function of distance (Tbulk = 300[K] + 10[K/m]*x).

If you do not know how to do CFD-Post variables have a look in the CFX tutorials.