Answer Happy

2.14 A pass-out two-stage turbine receives steam at 50 bar, 350 "C. At 1.5 bar, the hp steam exhausts and 12,000 kg of steam per hour are taken at this stage for process purposes. The remainder is reheated at 1.5 bar to 250 "Cand then Copyrighted materia 100 Power Plant Engineering expanded through the l.p. turbine to a condenser pressure of 0.05 bar. The power output from the turbine unit is 3750 kW. Take isentropic efficiency for hpandip. stages as 0.84 and 0.81 respectively. Calculate the boiler capacity required Lates. 18.5th) 2.15 A 850 MW steam power plant operates with turbine inlet at 100 bar, 550 °C and condenser pressure at 0.05 bar. There are three feedwater heaters placed optimally as follows: (i) the hp.heater is of the closed type with drains cascaded backward. (ii) the i.p heater is of the open type, and (ii) the l.p. heater is of the closed type with drains pumped forward. Each of the turbine sections has the same isentropic efficiency of 90%. The pumps have isentropic efficiencies of 80%. Calculate (a) the mass flow rate of steam at turbine inlet, (b) the mass flow rate of cooling water in the condenser, if it undergoes a 10 °C temperature rise. (c) the cycle efficiency, and (c) the cycle heat rate 2.16 A coal-fired power plant has a turbine generator rated at 1000 MW gross. The plant requires 9% of this power for its internal operations. It uses 9800 tonnes of coal of heating value 26 MJ/kg per day. The steam generator efficiency is 86%. Calculate the gross and net station heat rates and efficiencies. [Ans. 10.616 MJ/kWh, 11.667 MJ/kWh, 33.9%, 30.86%) 2.17 Steam is supplied to a pass-out turbine at 40 bar, 400 °C and dry saturated process steam is required at 4 bar. The l.p. stage exhausts at 0.1 bar and the condition line for the turbine expansion may be assumed to be straight. If the power load is 1000 kW and the maximum process load is 1.4 kW, estimate the maximum steam flow through the high and low pressure stages. Assume that the steam just condenses in the process plant. Ans. 3837.6 kg/h, 36353 kg/h] 2.18 A steam power plant has the boiler efficiency of 92%, turbine (mechanical) efficiency of 96%, and electric generator efficiency of 97%. If 7% of the power genc consumed in running auxiliaries of the plant and the overall plant efficiency is 34%, find the percentage of energy lost in the condenser [Ares37.4%) 2.19 An ideal steam power plant operates between 150 bar, 550 °C and 0.075 bar. It has seven feedwater heaters. Find the optimum pressures and temperatures at which the heaters operate 2.20 In a cogeneration plant, 10 kgh of steam at 80 bar, 480°C expands in the hp, turbine to 10 bar. From the exhaust 4 x 10 kgh of steam is extracted for process heating. The remaining steam expands in the l.p. turbine to 0.08 bar. Saturated liquid at 0.08 bar leaving the condenser is pumped to 9.5 bar where it mixes with the condensate from the process heater leaving at 9.5 bar, 120°C. The entire flow is then pumped to 80 bar. The isentropic efficiencies of the turbines and the pumps are 80% and 80%, respectively. Determine (a) Copyrighted materia Analysis of Steam Cycles 101 the heating load, in kJ/h, (b) the power developed by the turbines, in kW, and (c) the rate of heat transfer in the steam generator, in kJ/h. [Ans.(a) 9.53 kJ/h. (b) 236500 kW. (e)3.032 x 10 kJ/h)