One kilogram of boiling water is vaporized to steam at 100 kPa in a frictionless piston-and-cylinder device. Using the Steam Tables, answer the following:

(a) Is the heat needed to vaporize the water to steam equal to the change in enthalpy? Or TdeltaS?

(b) To calculate the work done by the steam, is the first law of thermodynamics equation or the general equation for work applicable?

(c) Is the entropy generation equal to the change in entropy of the water?

(d) Does the heat required for the vaporization of boiling water greater than the work done?

Support your answers with calculations and explanations.

Open System

Superheated steam at 3.0 MPa and 500^oCenters a desuperheater at a rate of 500 kg/hr. At what rate should liquid water at 2.5 MPa and 25^oC (H=129.327 kJ/kg) be added to the desuperheater to produce saturated steam at 2.2 MPa? Assume there is no heat exchange between the system and the surroundings. Determine the entropy generation of steam.