ME354 Thermodynamics 2

Problem Set #4: Rankine Cycle

Problem 4: 1

A simple Rankine cycle using water as the working fluid operates between the pressure limits of 7.5 kPa and 1800 kPa. Determine: (a) the cycle thermal efficiency; (b) the steam rate (specific steam consumption);

Answer:

(a)	thermal efficiency = 30.7%
(b)	steam rate = 4.46 kg/kWh

Solution

(69.5 KBytes)

Problem 4: 2

A reheat Rankine cycle using water as the working fluid operates between the pressure limits of 7.5 kPa and 17.0 MPa. Steam is superheated to 550 oC before it is expanded to the reheat pressure of 4.0 MPa. Steam is reheated to a final temperature of 550 oC. Determine: (a) the cycle thermal efficiency; (b) the steam rate (specific steam consumption);

Answer:

(a)	thermal efficiency = 40.52%
(b)	steam rate = 2.34 kg/kWh

Solution

(80.2 KBytes)

Problem 4: 9-11

Three high pressure turbines have been submitted for testing. Each operates with an inlet state of 1000 oF, 3500 psia steam. Turbine X has an exit state of 1000 psia at 660 oF and a heat loss of 7 Btu/lbm; turbine Y's exit state is 1000 psia at 635 oF with a heat loss of 12 Btu/lbm; and turbine Z's heat loss is 2 Btu/lbm with an exit state of 1000 psia at 680 oF. Summarize the test data, calculate the work output and isentropic efficiency of each turbine, and give a purchase recommendation.

Answer:

wx= 119.9 Btu/lbm	nx= 80.7%
wy= 133.8 Btu/lbm	ny= 93.1%
wz= 109.7 Btu/lbm	nz= 75.6%

Solution

(44.9 KBytes)

Problem 4: 9-21

Calculate the thermal efficiency of a simple Rankine cycle for which steam leaves the boiler as saturated vapor at 3 x 106 N/m2 and is condensed to saturated liquid at 7000 N/m2. The pump and turbine have isentropic efficiencies of 0.6 and 0.8, respectively. The pump inlet is saturated liquid.

Answer: n_t= 26.7%

Solution

(55.9 KBytes)

Problem 4: 9-53

Air is compressed from 1 atm to 300 psia. Determine the work required for an isentropic compressor and for a highly cooled compressor in which the air undergoes an isothermal process. What is the isothermal efficiency of the isentropic compressor (nt = Wt/W)? The inlet temperature is 60 oF.

Answer: n_s= 1.59, n_t= 0.63

Solution

(57.6 KBytes)

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