Herr Ortel,

During a transient flow the waves goes through the heat exchanger.

If you are using the characteristics method for water hammer calculation, depending on the type of heat exchanger, it can be replaced by an equivalent pipe having a crosssectional equivalent area and the head loss in the equivalent pipe is assumed equal to the head loss in the heat exchanger.

Commercial water hammer software includes heat exchanger modelation.

Regards,

R. Kühn