you know the more velocity in pipe in a heat exchanger gives the more Reynolds and then more nusselt number that is mean more H(convective heat transfer coef.) there for we expect to have more loss in hot water that is in pipe( after increasing velocity) but in experiment we are seeing less loss in temperature..why by increasing velocity (debye) we dont see more heat transfer?
You need to do a heat and material balance around the complete exchanger to determine if there is in fact more heat being exchanged even if the hot water is not getting cooler. Remember, there is more mass of hot water passing through the exchanger so more heat could be exchanged without the temperature going down.
