Question

Problem (2) (weight 40%) Figure Q2 shows a steam power system which is consisting of the following processes: Process 1-2: heat addition at constant pressure of 100 bar. Process 2-3: Expansion in a high pressure turbine to 10 bars. Process 3-4: heat addition at constant pressure of 10 bar. Process 4-5: Expansion in a low pressure turbine to 0.1 bar. Process 5-6: Heat removal in a heat exchanger at constant pressure of 0.1 bar. The different water and steam operating conditions are: • The enthalpy of water at point I equals to "hı", where hi equals to your ID number in J/kg. • Steam temperatures at point 2 and point 4 are both 500.C. Steam leaves the condenser as a saturated liquid. The isentropic efficiency of the turbines is 80 percent. Determine a) Show the cycle on a T-s diagram with respect to saturation lines. b) The total output work from the turbines. c) The total heat removed in the heat exchanger. d) The total thermal efficiency of the system. Constant pressure Vessel 1 Constant pressure Vessel 2 hi Turbine 1 Turbine 2 Heat exchanger Figure Q2

Answer 1

So, ha= hq + Xht - 762.52 + 1 X2014.6 The = 2777.12 kJ / dg Al Point 5 Sf = 1.3028 kJ/kg hp = 417,50 Scalxy heq=2257.4 KJ / deg Sf9 = 6.056] WJ/xy Also Su=55 7.7641=1-3029 +X[6.0567) x=7.7841-1.3028 = 1 6.0560 +4 (2257.4) ihs 417.50 t = 417.50+ 1x2257.4 thg = 2674.9 kJ/ Jeg Wou

for high pressure turbine : Is entropic effriency 80% ( 2 7 = ti ho he -2777.12 fz-nhs $0.80 - 3375.) - hos 3375) –478.394 = 3375.) - h = 33751-478.385 The = 2896.716 XJ/29 Work output = Wouth = hin his I Wouth = 478.384 for low presude turbine I sentropic efficiency = 80% n = hy hs 0:80 = 3479.) - hs' hy-hs 804.2 The' = 28 35.74 kJ/xg Work output = Wouth = hi ha I Woutz= 643.36 kJ/kg (6 total work output of turbines Wouth + Wouth 478.384 +464356 Wout Wout > 1121.744 Jk3] Dey

C Heat remove in heat ex exchanger Q= ho-ho 417.50 = 2835.74 Q 2418.24 kJ/ Jeg thermal efficiency total world heat added Vh = 1121.744 1121.744 che-h, ) tchur hé) (3335.) - 13391) + (3479.1 – 28%:710) 1121.744 1977 +582.384 Ith th = 1121.744 2400.438 2559.384 Thomal Efficiency of System = 43.83 %