Question

A gas turbine receives air at temperature T1 = 827 °C and specific volume v, -0.1 m®/kg. Air exits the turbine at P2 = 3 bar and T2 = 450 °C. The volumetric flow rate of air at the inlet is 0.5 m/s. The power output on the shaft is 1900 kW. Determine: The pressure of air at the inlet (pa) in kPa [2 marks] b) The mass flow rate in kg/s [1 mark] c) Find the rate of heat transfer from the turbine to the surroundings in kW.[4 marks] d) If the heat transfer occurs at an average temperature of 500°C, what is the rate of entropy production, in kW/K of the turbine process? For air, Cv=0.72 kJ/kgK, and R=0.286kJ/kgK. (5 marks] You can assume that Potential energy change and kinetic energy change can be neglected. • Air is an ideal gas. • The turbine can be modelled as a control volume at steady state. Ti = 827 °C vi 0.1 m/kg Turbine w=1900 kW p2=3 bar T2=450°C Figure 1. Air turbine running at steady state

Answer 1

u 0.5m3's 0.5 5kg/s w=1900 kwall S=1 L 0.1 C To 773K Soln Volume flow rate 0.1 mi 2/16g b) mass flow rale m from gass egn P = SRT P = L x 286 X 1100 0.1 T,= 827c ,12-450°C P = 3.146 MPa = look inlet Pressure. Cv = 0.72 KB/igic 0.286 KB Rate of heat Transfer To = 5000 Kallegmal nice (Ti-T2)-&=W 5X1.008 (827-450) = 1900 0.08 kwatt Q = sowatt) = Entropy generation O seus + Oscys = Sgen To do + micple (3) -eleme)] 773 +5x{1.008 loodxle (723) -0.286 luſ lloo Sgen Sgen = 1.349 KJ llege Q -asun Sgen ( 31.4.6 80 773 1.46) csscanned with CamScanner