Question

Water at 100 kPa, 150°C receives 75 kJ/kg in a reversible process by heat transfer. Which process changes * the most: constant T, constant v or constant P?

ds = dq/T

Answer 1

The constant v line has a higher slope than the constant P line also at positive slope. Thus both the constant P and v processes have an increase in T. As T goes up the change in * is smaller.

The constant T (isothermal) process therefore changes * the most.