I need help ,Fluid mechanics.?

Question

How to calculate the hidraulic diameter and reynolds number, on a heat exchanger?

we must think that a heat exchanger is like a tube with obstacles that have sharp edges and is not constant section. (pictures look before responding), (the heat exchanger type is shell ant tube).

Answer 1

I am having trouble understanding your question.  General rule is to start out looking at where you would have the greatest head loss in the tubes.  I.e., the narrowest sections.  The sharp edged inlets should have a relatively small impact if the tubes are long and narrow.  The lack of constant section is troubling, but again, just look at some same points.