77. A 350 mm x 450 mm steam engine running at 280 rpm has a clearance steam condition of 2

MPa and 230°C and exits at 0.1 MPa. The steam consumption is 2000 kg/hr and mechanical

efficiency is 85%. If indicated mean effective pressure is 600 kPa, determine brake thermal

efficiency.

@ 2 MPa and 230°C: h1 = 2849.6 kJ/kg s1 = 6.4423 kJ/kg-K

@ 0.1 MPa: sf = 1.3026 kJ/kg-K hf = 417.46kJ/kg sfg = 6.0568 kJ/kg-K

hfg = 2258 kJ/kg hf2 = 417.46 kJ/kg

A. 23.34% B. 15.25% C. 14.16% D. 27.34%