An engineer proposes to eliminate the condenser in an ideal Rankine cycle in order to form an open cycle. Lake water is available at 16° C. The lake water is pumped to 5 MPa and then heated at constant pressure to 400° C. The “spent” steam is rejected back into the lake. Determine the first-law thermal efficiency of this process and compare it with that of Problem 9.9. What are some of the practical problems with this proposed cycle?

Problem 9.9

In a Rankine cycle, steam leaves the boiler at 400° C and 5 MPa. The condenser pressure is 0.01 MPa. The water entering the pump is saturated. Determine the first-law thermal efficiency and compare it to that of a Carnot cycle operating between the same temperature extremes.