In a binary vapour cycle the mercury vapour entering the turbine is dry and saturated at 12.5 bar pressure. The condenser pressure of mercury cycle is 0.07 bar. The steam cycle operates between the pressure 30 bar and 0.07 bar. The steam is superheated to 350° C. Find the efficiency of combined cycle
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A binary-vapour cycle operates on mercury and steam. Saturated mercury vapour at 4.5 bar is supplied to the mercury turbine, from which it exhaust at 0.04 bar. The mercury condenser generates saturated 8. steam at 15 bar which is expanded in a steam turbine to 0.04 bar. (i) Find the overall efficiency of the cycle. (ii) If 50000 kg/h of steam flows through the steam turbine, what is the flow through the mercury turbine? (iii) Assuming that all processes are reversible, what is the useful work done in the binary vapour cycle for the specified steam flow? (iv) If the steam leaving the mercury condenser is superheated to a temperature of 300°C in a super heater located in the mercury boiler, and if the internal efficiencies of the mercury and steam tur- bines are 0.85 and 0.87 respectively, calculate the overall efficiency of the cycle. The properties of saturated mercury are given below: p (bar) t(C) (keJI kg) (hJ I kg K) (m3/kg) 4.5 0.04 450 216.9 63.93 29.98 355.98 329.85 0.1352 0.0808 0.5397 0.6925 79.9 x106 76.5 x 10-3 0.068 5.178 [Ans. (i) 52.94%, (ii) 59.35 10° kg/h, (iii) 28.49 MW, (iv) 46.2%)