- Its required to study the ability for heat transfer enhancement in a counter flow heat exchanger operating for hot water cooling (water inside the tubes while the air is outside), that is by increasing the value of the forced convection Nusselt Number. Suggest the parameters which must be considered during the experimental investigation. Explain how you are going to build the experimental test rig to get the reading from it. Write all assumptions and approximations. Describe the instruments used in details then show how will report your results.