Chapter 8, Problem 8.49P

Question # 1 The networkoutput and the thermal efficiency for the Carnot and the simple ideal Rankine cycles with steam as the working fluid are to be calculated and compared. Steam enters the turbine in both cases at 5 MPa as a saturated vapor, and the condenser pressure is 50 kPa. In the Rankine cycle, the condenser exit state is saturated liquid and in the Carnot cycle, the boiler inlet state is saturated liquid. Draw the T-s diagrams for both cycles.

1. In a regenerative steam cycle employing three closed feed heaters the steam is supplied to the turbine at 42 bar and 500 0C and is exhausted to the condenser at 0.035 bar. The bleed steam for the feed heating is taken at pressure of 15,4 and 0.5 bar. Assuming ideal processes and neglecting pump work. Calculate(i) The fraction of the boiler steam bled at each stage(ii) The power output of the plant per unit mass flow rate of boiler steam (iii) The cycle efficiency2. In a gas turbine generating station the overall compression ratio is 12/1, performed in three stages with pressure ratio of 2.5/1,2.4/1 and 2/1 respectively. The air inlet temperature to the plant is 250C and intercooling between stages reduces the temperature of 400C. The HP turbine drives the HP and intermediate-pressure compressor stages, the LP turbine drives the LP compressor and the generator. The gases leaving the LP turbine are passed through a heat exchanger which heats the air leaving the HP compressor. The…

In a reheat cycle steam at 15 MPa, 540°C enters the engine and expands to 1.95 MPa. At this point the steam is withdrawn and passed through a reheater. It reenters the engine at 540°C. Expansion now occurs to the condenser pressure of 0.0035 MPa. (a) For the ideal cycle, find e. (b) A 60,000 kw turbine operates between the same state points except that the steam enters the reheater at 1.95 MPa and 260°C, departs at 1.8 MPa and 540°C. The steam flow is 147,000 kg/hr, generator efficiency is 96%. For actual engine, finde, m,, and m, (c) Determine the approximate enthalpy of the exhaust steam if the heat lost through the turbine casing is 2% of the combined work. Ans.: (a) 46.1%, (b) 37.3%, 2.45 kg/kwh, 79.3%, (c) 2489.6 kJ/kg

2.) A steam power plant uses the ideal Regenerative Rankine cycle with single open feedwater heater where the steam enters the high-pressure turbine at 4 MPa and 300C. It partially expands to 600 kPa then some steam is extracted at this point. The remaining steam expands and enters the condenser at 10 kPa. Sketch the schematic diagram and the TS diagram with labeled points, and solve for mass taken for feedwater heating, Qa, Qr, Wt, Wp, Wnet, thermal efficiency, and Steam rate. Neglect the condensate pump work. kJ kg 20.01%, 2286.801457.51,832.54 3.34,829.2936.26%, 4.34. ) kg kWh

2. In a reheat cycle steam enters the high pressure turbine at 40 bar and 400°C. It expands isentropic ally to 6 bar and is reheated at constant pressure to 400°C. This steam is expanded isentropic ally in the low pressure turbine to the condenser pressure of 0.1 bar. Calculate the thermal efficiency and steam consumption for 10 MW output.

a. Calculate the thermal efficiency and turbine-exit quality for an Ideal Rankine Cycle where the steam exits boiler at 5MPa, 450C and the condenser pressure is 15 kPa. Draw the systems and the Ts diagram for the process. b. Calculate also the thermal efficiency and turbine-exit quality if the system is modified to an Ideal Reheat Rankine Cycle where the reheat takes place at 1 MPa and the steam leaves the reheater at 500C. Draw the systems and the Ts diagram for the process and discuss your findings of these two systems.

A regenerative steam power cycle with an open regenerator is used to produce a net power of 330 MW. The steam enters the first expansion stage at 12 MPa, 560°C and expands to 1 MPa, where part of the steam is extracted for regeneration. The rest of the steam continues to expand to 6 kPa. The feed water leaves the regenerator as a saturated liquid at 1 MPa. If the turbines and pumps are isentropic, calculate the following: (a) The thermal efficiency of the cycle. (b) The mass flow through the first stage of the turbine.

Please use property tables. Thank you Steam enters the high-pressure turbine of an ideal reheat Rankine cycle at 10 MPa and 500°C. The low-pressure turbine inlet admits steam at 1 Mpa. Assume that the pump inlet is a saturated liquid at 10 kPa and that 80 MW of power is produced overall. 1. Report the amount of heat added in the reheat process, in kJ/kg, to one decimal place using rounding. 2. Report the amount of work produced in the low-pressure turbine, in kJ/kg, to one decimal place using rounding.

Water is the working fluid in an ideal Rankine cycle. Superheated vapor enters the turbine at 10 MPa, 550 degree Celsius. The condenser pressure is 10 kPa. The cycle is modified to include one open feedwater heater operating at 0.7 MPa. Saturated liquid exits the feedwater heater at 0.7 MPa. The new power output of the cycle is 150 MW. Determine for the cycle the rate of heat transfer to the working fluid passing through the steam generator, in kW, (b) the thermal efficiency.