Help

Sastry Gunturi

I am modelling a cross-flow heat exchanger.....which can thought of 2 blocks (with a common face)....and a bunch of tubes pass through 2blocks.Water flows over the tubes in one block and air in the other.The temperature of Water and Air are 75 C and 25 C while the velocities are 0.05m/s and 5m/s. The rods should carry away heat from water and transfer to air....So there would be a varition in the temperature of rods.But in my model Iam able to see heat transfer and no temperature variation is seen.How could I do that???? Can anyone plz help me in this regards....Waiting for you guys response.....Thank you....