Exergy analysis tools for ASPEN applied to evaporative cycle design

A general two-step approach for cycle development and finding optimal cycle layouts is discussed. Tools for applying this approach with ASPEN+ are presented. The technique is applied to evaporative gas-turbine cycles with one intercooler stage, no reheat and no steam-turbine. In a first step, several evaporative cycle layouts are optimized by considering one single black box evaporative heat recovery system. The feasibility of each cycle is quantified by the exergy destruction and exergetic efficiency of the black box heat recovery system. In a second step, after cycle optimization, insights provided by a composite curve analysis of the black box are used to guide the design for a feasible evaporative heat exchanger network. All cycle simulations are performed with ASPEN+. Two recently home-made ASPEN+ subroutines are presented. One introduces the exergy concept in ASPEN+, the other generates composite curve, hence avoiding the use of ADVENT(TM). The analysis shows that optimal evaporative gas-turbine cycles yield performances similar to that of combined cycles. A new heat recovery system is disclosed (REVAP(R)), where the intercooler heal, the aftercooler heat and the turbine exhaust heat are recovered simultaneously. (C) 1997 Elsevier Science Ltd.