ME 301 Homework 11

ME 301 Homework 11
1. Air is compressed in an isentropic process from an initial pressure and temperature of P 1 = 90 kPa
and T1 = 22 oC to a final pressure of P2 = 900 kPa. Determine:
a.The final temperature of the air.
b. The work done per kg of air during the process.

2. What four processes make up the ideal Otto Cycle? What is happening in an actual engine during
the real processes that are approximated by these idealized processes?

3. An air standard Otto cycle has a compression ratio of 9.5. At the beginning of the isentropic
compression the working fluid, air, is at an initial pressure, temperature and volume of P 1 = 100 kPa,
T1 = 35 oC and V1 = 600 cm3. The temperature at the end of the isentropic expansion is T4 = 527 oC.
Assume Cp = 1.005 kJ/kgK & Cv = 0.718 kJ/kgK , R = 0.287 kJ/kg K and k = 1.4 for the air. Sketch
the Pv and Ts diagrams for the cycle and determine:

a. The temperature and pressure, at the beginning of the isentropic expansion: P 3 & T3
b. The heat transferred into the working fluid during the heat addition process: Q 2-3
c. The work done by the air during the isentropic expansion: W 3-4
d. The work done on the air during the isentropic compression: W1-2
e. The thermal efficiency of the engine: 

4. What four processes make up the ideal Rankine Cycle? What is happening in an actual power plant
during the real processes that are approximated by these idealized processes?

5. A power plant is analyzed as a simple ideal Rankine cycle, with a boiler operating at 300 oC. Steam
leaves the boiler and enters the turbine as a saturated vapor. The condenser operates at 40 oC.
Sketch the cycle on a Pv and a Ts diagram and then determine:

a. The pressure in the boiler: P2 = P3
b. The pressure in the condenser: P1 = P4
c. The heat added in the boiler, per kg of steam: q2-3
d. The work done by the turbine, per kg of steam: w3-4
e. The work done by the pump, per kg of steam: w 1-2
f.

The thermal efficiency of the power plant: 

6. A power plant is analyzed as a simple Rankine cycle with a boiler operating at a pressure of 7 MPa.
Steam leaves the boiler and enters the turbine as a superheated vapor at a temperature of 500 oC.
The condenser operates at a pressure of 10 kPa. Sketch the cycle on a Pv and a Ts diagram and
then determine:

a. The temperature in the condenser: T1 = T4
b. The heat added in the boiler, per kg of steam: q2-3
c. The work done by the turbine, per kg of steam: w3-4
d. The work done by the pump, per kg of steam: w1-2
e. The thermal efficiency of the power plant: 