Wall boundary condition.
 

i have a cylinder with a u-shape extrude cut through which hot water flows through the inlet and outlet ports.

INLET IS A VELOCITY INLET where I have defined velocity and temperature. Outlet is outflow.

Ansys 14.5 creates 2 contact surface b/w water and cylinder. What boundary condition should I give on these walls.
The conditions I am giving now does not change the temperature of water i.e. water comes out at its inlet temperature only.