At a particular location in the ocean the temperature near the surface is 80oF, and the temperature at the depth of 1500 ft is 46oF. See the schematic below proposing a power plant that will utilize this naturally occurring temperature gradient to produce electrical power. The proposed power plant is based on the Rankine cycle, with ammonia as the working fluid. The power to be developed by the turbine is 8.2×108 Btu/hr. For simplicity, the properties of seawater can be taken as those of pure water. Note the temperature of the ammonia when leaving the boiler is 75oF and when entering the condenser is 50oF.

a) Calculate the thermal efficiency of the proposed cycle and compare to the efficiency of a reversible power cycle operating between thermal reservoirs at those temperatures.
b) Calculate the net power output of the plant, in Btu/hr, if the pumps used to circulate the seawater through the boiler and condenser require a total combined power input of 2.55×108 Btu/hr.
c) Determine the seawater flow rates through the condenser, in lb/hr.
d) If the isentropic efficiencies ηt = ηc = 0.9 are taken into account, what would be the net power out?