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BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE, PILANI

HYDERABAD CAMPUS

SECOND SEMESTER 2010-2011

APPLIED THERMODYNAMICS (ME C211)

Feb. 07, 2011 (Monday) TEST - 1 (Open Book)

11:00 – 11:50 AM Max. Marks: 60

1. 

A binary vapour cycle operates with potassium cycle and reheat-regenerative steam cycle. Potassium enters

 potassium turbine at 6 atm and 1325 K and leaves the potassium condenser at 950 K. The heat rejected in the

condenser of the potassium cycle is used only for the latent heat gain in the boiler  of the steam cycle. Steam at 6

MPa and 5500

C enters the high pressure steam turbine and expands to 500 KPa where a fraction of steam is

extracted to heat the feed water in an open feed water heater and the remainder is supplied to the reheater. The

reheated steam enters the low pressure steam turbine at 500 KPa and 5000

C and expands to the condenser

 pressure of 7.5 KPa. For all calculation purposes, all pump works can be assumed negligible and hence equal to

zero. (Note: 1 atm = 101.325 KPa). (Total = 35 M)

a) 

Draw the T-s diagram (7 M)

 b) 

Calculate heat added in potassium cycle (QP1) (2 M)c)  Heat rejected in potassium cycle (QP2) (2 M)

d)  Work output in potassium cycle (W P) (2 M)

e) 

Work output of HP turbine (W S1) (3 M)

f) 

Work output in LP turbine (W S2) (3 M)

g) 

Heat input in Economizer (QS1) (2 M)

h) 

Heat input in Super heater (QS2)  (2 M)

i) 

Heat input in Reheater (QS3) (2 M)

 j) 

Mass of potassium circulated per kg of steam (m p) (2 M)

k)  Mass fraction bled off in feed water heater (m1) (3 M)

l) 

 Net work output (W ) (2 M)

m) 

 Net heat input (Q) (2 M)n)

 

Efficiency of the binary cycle (1 M)

From superheated potassium table at 6 atm and 1325 K

v = 0.000411 m3/kg h = 2873.7 kJ/kg s = 4.4162 kJ/kg.K

From saturated potassium tables

T  (K) P (atm) v f  (m3/kg) h f  (kJ/kg) h fg (kJ/kg)   hg (kJ/kg) s f (kJ/kg.K)   s fg (kJ/kg.K) sg (kJ/kg.K)

950 0.447 0.001462 771.4 1979 2750.4 2.7313 2.0816 4.8129

2. 

Consider a cogeneration plant where steam enters the turbine at 7 MPa and 500 0 C. Some steam is extracted from

the turbine at 500 kPa for process heating. The remaining steam continues to expand to 5 kPa. Steam is then

condensed at constant pressure and pumped to the boiler pressure of 7 MPa. At times of high demand for process

heat, some steam leaving the boiler is throttled to 500 kPa and is routed to the process heater. The extractionfractions are adjusted so that the steam leaves the process heater as a saturated liquid at 500 kPa. It is

subsequently pumped to 7 MPa and mixed with the remaining steam before being supplied to the boiler. Draw the

appropriate T-s and schematic diagrams for the cogeneration plant. (5+5 = 10 M)

3.  A refrigerator using R-22 operates on an ideal vapour compression cycle between –250 C and 40

0 C. The mass

flow rate of refrigerant is 0.05 kg/s. Draw the suitable T-s  and  p-h  diagrams. Determine (a) the rate of heat

removal from the refrigerated space, (b) the isentropic discharge temperature using R-22 superheated tables, (c)

the power input to the compressor, (d) the heat rejection to the environment and (e) the COP. (2+4*3+1= 15 M)

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