Question

3. A cogeneration system works with a water cycle and a refrigerant (ammonia) cycle combined. Superheated water vapor enters turbine 1 (efficiency of 85%) at a flow rate of 5 kg/sec, 50 bar and 500°C and expands to 1.5 bar. Half of the flow is extracted for industrial heating and the rest enters a heat exchanger. The condensate leaves the heat exchanger as saturated liquid at 1 bar and combines with the return flow from the industrial process, which comes back at 60oC and 1 bar. The combined flow is pumped (efficiency of 85%) to the boiler pressure. The refrigerant cycle is an ideal Rankine cycle. The ammonia enters turbine 2 at a pressure of 14 bar and a temperature of 100°C and leaves the condenser at 3 bar. Calculate: a) The amount of heat required by the boiler, in kW. b) The net power output of the cogeneration system, in kW. c) The heat transfer provided to the industrial process.

Answer 1

2 T Tz IT co 2b Boiler 20 Condesser Industrial heading 6 14 9 3 10 Pump Pump Miner 5 2 na 5 rols 0.85 P = 50 bar 34434. Koling and 50bar? z bi Ti = 500c Si 6-97881 Kollega np. 0.85 P2 = 1.5 bar 125=526-Sf =1.4336 + 6.9.781 0.96 P2 = 1.5bar2 Sia Sie Syg 5.7899 ning 2 by nas x bdg 2599.31 Kolkg My = 0.85 ba b=2724.62 46 3434.7 3434.7-2599.31 z kg birha hi-his 417.46 Kolig 251 13 loolky h₂ bs at Ibar hy [Ibar, boc miza by + my ha a manis (2.5 x 251.43) + Q.5 5*417.46] (2.5+2. 5) xbs ho 334.295 kolky no hot Us CP6-Ps 340.23 Koling Wap ap, ho-hs 5.932 kol kg hi-hz 3434.7 2724.62 = 710.08 Kollig Roperties hom Ammonia table Py = lebar Abar 2 ha ha = 1651.2 Kulty Tag = 100°c Sy = 5.4433 Kollig k PE 3 bar ? Se - Sf 0.99 Sy=se <big ono Sfg be a be t ng 1428.28 Kolking

137.42 ho Wpg 1.69 Kolting 1651.2 1428.28 . ha= bg at 3 bar Kulky ha + la CPo – 12) - 139.11 139.11 kuling ho-ba Wy2 = bebe 222.92 kaltig By energy balance, high Ch 26 kg] the) a my Chy-bio) 2.5x (2724.62 417.46 max (1651.2 139.11) Kgls a) heat transfer in Boiles mix Chi-bo 5x[3434.7 – 340.23] b) Net Power out a in [wp-wp.) + m [hoz - WP2) 5x (710.08 – 5-932 (222 222.92 436406² 3.81 min = 15 472.35 kW 3.81 -lo + ku 은 ol ) heat used for Industrial heahng ma [bab-by) 2.5 *[2724.62 417.46] =5767.9 km