Air Cooled Two-Stage Rankine Cycles for Large Power Plants Operating With Different Working Fluids: Performance, Size and Cost

A two stage Rankine cycle for power generation is presented in this paper. It is made of a water steam Rankine cycle and an Organic Rankine bottoming Cycle. By using an organic working fluid with higher density than water, it is possible to reduce the installation size and to use an air-cooled condenser. Following our previous studies, 3 high critical temperature organic fluids, R245fa, R365mfc, isopentane (iC5) and ammonia are tested as potential candidates for this application. The performances of the two stage Rankine cycle operating with those different working fluids are evaluated for a nuclear plant case. The size of system components (heat exchangers and turbine) is estimated for each tested fluid. The influences of their thermodynamic and transport properties are analyzed. In addition, an estimation of the installation cost is done by introducing cost functions.