hi

hysys, for sure, is not capable of designing a heat exchanger, but it can help you certainly when you have an already designed exchanger and you wish to see that actual exchanger geometry result on simulation i.e. pressure drop.
as camiqmex pointed, Aspen EDR is good to start with. But HTRI is used industrially for designing/rating heat exchangers of all type.
What these software's do? they just reduce the time of calculation. You just need to mix your knowledge with software input and you will have your results.

Regards

Ammad Khan