# rankine_units.py (Source)

```"""
Calculate the efficiency of a Rankine vapor power cycle using a pure fluid model
for water. Includes the units of quantities in the calculations.

Requires: Cantera >= 3.0.0, pint
Keywords: thermodynamics, thermodynamic cycle, non-ideal fluid, units
"""

import cantera.with_units as ctu

# parameters
eta_pump = 0.6 * ctu.units.dimensionless  # pump isentropic efficiency
eta_turbine = 0.8 * ctu.units.dimensionless # turbine isentropic efficiency
p_max = 116.03 * ctu.units.psi  # maximum pressure

def pump(fluid, p_final, eta):
"""Adiabatically pump a fluid to pressure p_final, using
a pump with isentropic efficiency eta."""
h0 = fluid.h
s0 = fluid.s
fluid.SP = s0, p_final
h1s = fluid.h
isentropic_work = h1s - h0
actual_work = isentropic_work / eta
h1 = h0 + actual_work
fluid.HP = h1, p_final
return actual_work

def expand(fluid, p_final, eta):
"""Adiabatically expand a fluid to pressure p_final, using
a turbine with isentropic efficiency eta."""
h0 = fluid.h
s0 = fluid.s
fluid.SP =s0, p_final
h1s = fluid.h
isentropic_work = h0 - h1s
actual_work = isentropic_work * eta
h1 = h0 - actual_work
fluid.HP = h1, p_final
return actual_work

def print_state(n, fluid):
print('\n***************** State {0} ******************'.format(n))
print(fluid.report())

if __name__ == '__main__':
# create an object representing water
w = ctu.Water()

w.TQ = ctu.Q_(80.33, "degF"), 0.0 * ctu.units.dimensionless
h1 = w.h
p1 = w.P
print_state(1, w)

# pump it adiabatically to p_max
pump_work = pump(w, p_max, eta_pump)
h2 = w.h
print_state(2, w)

# heat it at constant pressure until it reaches the saturated vapor state
# at this pressure
w.PQ = p_max, 1.0 * ctu.units.dimensionless
h3 = w.h