Problems Special for ME 200 Fall 2010
Special Problems 24 and 25
Due Friday, October 29, 2010
SP24:
Consider a steam power cycle in which saturated water vapor at 25 bar (state 1) at the
exit of the boiler enters a turbine and expands to 0.1 bar and 80% quality (state 2). Heat
is rejected such that saturated liquid at 0.1 bar (state 3) exits the condenser. Water
leaving the condenser is pumped to 25 bar and 46C (state 4) at the inlet of the boiler.
(a) Draw a diagram showing all the components of the steam power cycle labeling the
relevant states described above.
(b) Is the Clausius inequality satisfied? Provide quantitative support for your answer.
(c) Are the Carnot principles satisfied? Provide quantitative support for your answer.
SP25:
Consider a Carnot refrigeration cycle operating within the vapor dome. The cycle is
executed in a steady-flow system using R-134a. The values of maximum and minimum
temperatures in the cycle are 20C and -8C, respectively. enters R-134a as saturated
vapor (state 3) and leaves as saturated liquid (state 4) in the reversible heat rejection
process in the condenser; state 1 and state 2 correspond to the inlet and exit of the
reversible heat addition process in the evaporator of the cycle. There is reversible,
adiabatic compression from state 2 to state 3 and reversible, adiabatic expansion from
state 4 to state 1. The quality of R-134 at state 1 is 17.5%.
(a) Show the refrigeration cycle on T-s diagram. You must label states, show values of
temperature and specific entropy, and indicate lines of constant pressure.
(b) Calculate the heat addition (kJ/kg) in the cycle.
(c) What is the quality (%) of R-134a at the exit (state 2) of the reversible heat addition
process in the evaporator?
(d) Determine the COP of the refrigeration cycle considering the relevant work and heat
interactions. Find the COP of the refrigeration cycle considering that the cycle is Carnot
(reversible) cycle.