Saturdated water vapor (steam) is commonly used as a heat source
in heat exchanger applications. Why saturated vapor? Why
saturated water vapor? In a plant of any reasonable size,
several varieties of saturated steam are commonly available; for
example, saturated steam at 4.5,9,17, and 33 bar. But the higher
the pressure the lower the useful energy content (why?), and the
greater the unit cost. Why then is higher-pressure steam used?