MECH 3805 Soln Q7
MECH3805 – Winter 2015 Quiz #7.A If you wish, you can do this quiz in groups of two. Time allocation: 30 minutes - YOU MUST USE A PENCIL! Name: ____________________________ Student No: ____________________ Name: ____________________________ Student No: ____________________ NOTE: In the problem below subscript “s” refers to “isentropic”, and subscript “a” refers to “actual”. A regenerative Rankine cycle power plant with one open FWH has water as the working fluid. The turbine and the pump have an isentropic efficiency of 85%. Superheated vapor enters the turbine (State 1) at 16 MPa and 560°C (h1=3465.4 kJ/kg). Some steam (fraction y) is extracted from the turbine (State 2) at 1 MPa (h2s=2745.1 kJ/kg, s2a=6.7451 kJ/kg.K) and sent to the open FWH. The rest of the steam is expanded in the turbine to 8 kPa (State 3) and delivered to the condenser. Saturated liquid at 8 kPa leaves the condenser (State 4) (h4=173.88 kJ/kg) and enters Pump#1. At the exit of Pump #1 (State 5) the enthalpy is: h5=175.06 kJ/kg. Saturated liquid at 1 MPa exits the FWH (State 6) (h6=762.81 kJ/kg). Water enters the boiler (State 7) with an enthalpy of h7a=782.7 kJ/kg. The flow rate through the boiler is 120 kg/s. 1. 2. 3. 4. 5. 6. Draw the cycle schematic, and mark the states. Draw the T-s diagram and mark the states. Find fraction y. Find the total work of the turbine. Find the heat input in the boiler. Find the cycle efficiency if the total pump work is 2497 kW. MECH3805 – Winter 2015 Quiz #7.B If you wish, you can do this quiz in groups of two. Time allocation: 30 minutes - YOU MUST USE A PENCIL! Name: ____________________________ Student No: ____________________ Name: ____________________________ Student No: ____________________ NOTE: In the problem below subscript “s” refers to “isentropic”, and subscript “a” refers to “actual”. A regenerative Rankine cycle power plant with one open FWH has water as the working fluid. The turbine and the pump have an isentropic efficiency of 85%. Superheated vapor enters the turbine (State 1) at 16 MPa and 560°C (h1=3465.4 kJ/kg). Some steam (fraction y) is extracted from the turbine (State 2) at 1 MPa (h2s=2745.1 kJ/kg, s2a=6.7451 kJ/kg.K) and sent to the open FWH. The rest of the steam is expanded in the turbine to 8 kPa (State 3) and delivered to the condenser. Saturated liquid at 8 kPa leaves the condenser (State 4) (h4=173.88 kJ/kg) and enters Pump#1. At the exit of Pump #1 (State 5) the enthalpy is: h5=175.06 kJ/kg. Saturated liquid at 1 MPa exits the FWH (State 6) (h6=762.81 kJ/kg). Water enters the boiler (State 7) with an enthalpy of h7a=782.7 kJ/kg. The flow rate through the boiler is 60 kg/s. 1. 2. 3. 4. 5. 6. Draw the cycle schematic, and mark the states. Draw the T-s diagram and mark the states. Find fraction y. Find the total work of the turbine. Find the heat input in the boiler. Find the cycle efficiency if the total pump work is 1248 kW.
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