At a particular location in the ocean, the temperature near the surface is 80oF, and the temperature at a depth of 1500 ft is 46oF. A power plant based on the Rankine cycle, with ammonia as the working fluid, has been proposed to utilize this naturally occurring temperature gradient to produce electrical power. The power to be developed by the turbine is 8.2 X 108 Btu/h. A schematic diagram is shown. For simplicity, the properties of seawater can be taken as those of pure water.Assume the isentropic efficiency of the turbine is 80% and the isentropic efficiency of the pump is 70%. Assume that the ammonia leaving the boiler is saturated vapor and that the ammonia leaving the condenser is saturated liquid.
a.) Estimate the net power output of the plant, in Btu/h if the pumps used to circulate seawater through the evaporator and condenser heat exchangers require a total power input of 2.55 X 108 Btu/h.
b.) Determine the seawater flow rates through the boiler and condenser, in lb/h.
c.) Estimate the thermal efficiency of the proposed cycle and compare it to the thermal efficiency of a reversible power cycle operating between thermal reservoirs at 80 and 46oF.