An integrated analysis of the kalina cycle in combined cycles

The Kalina cycle, which uses a varying composition ammonia-water mixture as the working fluid, is an efficient bottoming cycle for a gas turbine. This paper presents comparisons between Rankine and Kalina bottoming cycles under different gas turbine cycles. We present a new graphically based and interactive thermal cycle analysis program. We vary the ratio of bottoming cycle power to gas turbine power (the power fraction) and present First and Second law efficiency results. For the combined cycles we modeled, when the power fraction is between 0.25 and 0.5, the gas turbine- Kalina cycle is more efficient than the gas turbine-Rankine cycle. Below 0.25, they are nearly equal; above 0.5 the Rankine efficiency is higher. Up to a certain power fraction the gas turbine exhaust heats the bottoming cycle fluid to the specified temperature. For the Kalina cycle this power fraction is 0.34 and for the Rankine cycle it is 0.24. For high power fractions the Kalina requires less supplementary heat than the Rankine cycle. We calculate irreversibility rates for each component and determine the fraction contributed by each component.