Power Plant Engineering

NON-CONVENTIONAL ENERGY RESOURCES AND UTILISATION 115

h 6 = hg at 28 bar = 2801.7 kJ/kg

hl at 5.5 bar = 2801.7 kJ/kg

t 1 = 176°C (20°C superheat)

s 1 = 6.897 kJ/kg-K

v 1 = 0.356 m^3 /kg

s 2 s at 0.15 bar = s 1 = 6.897 = 0.7327 + x 4 s (7.306)

x 2 s = 0.8437

h 2 s = 218.7 + 0.8437 (2377.24)

= 2224.38 kJ/kg

Isentropic work = h 1 – h 2 , s

= 2801.7 – 2224.38 = 577.32 kJ/kg

Actual turbine work = 0.82 × 577.32 = 473.4 kJ/kg.

h 2 = h 1 – WT

= 2801.7 – 473.4 = 2328.3 kJ/kg

Ignoring pump work

h 3 = h 4 = 218.7 kJ/kg

h 5 = hf at 20°C = 88.5 kJ/kg

Turbine steam flow =

100 10^3

(473.4 0.9)

×

×

= 234.7 kg/s

= 0.845 × 10^6 kg/hr

Turbine volume flow = (0.845 × 10^6 × v 1 ) /60

= (0.845 × 10^6 × 0.356)/60

= 5013.4 m^3 /min

Cooling water flow to condenser, m 5

m 5 (h 3 – h 5 ) = m 2 (h 2 – h 3 )

m 5 = (2328.3 – 218.7) m^2 /(218.7 – 88.5)

= 2109.6 × 0.845 ×

106

130.2

= 13.7 × 10^6 kg/hr

Heat added = h 6 – h 4

= 2801.7 – 218.7 = 2583 kJ/kg

Plant efficiency = WT × 0.9 / (h 6 – h 4 ) = (473.4 × 0.9)/2583 = 16.49%

Plant heat rate =

3600

0.1649

= 21831.4 kJ/kWh.