Heat exchangers represent equipment that is widely used in industry to lower, raise the temperature of a fluid. The problems related to thermo hydraulics concern above all the thermal dimensioning of the devices. In this work, we validate the results obtained with the use of the Comsol-Multiphysics software and that of the experimental and fluent code of a turbulent flow in forced convection for two hot and cold fluids to see the thermal behavior of the water in the coaxial exchanger. The numerical results obtained clearly show that the thermal performances are dependent on the value of the turbulence intensity and of the fluid used.