Integration of exergy analysis and pinch technology
Abstract
Exergy analysis is widely used in energy system analysis for more efficient energy use. It identifies the locations, types, and magnitudes of exergy loss and can be used to guide steps taken to reduce inefficiencies. In the late seventies and early eighties, a new method, pinch technology appeared, addressing the optimization of heat exchanger networks. Subsequently, pinch analysis has been adapted for application to systems including power equipment. Both exergy analysis and pinch technology have been studied and applied effectively to energy system separately for many years. Although some comparisons and case studies have been made with results obtained from both methods, systematic work has not been done to compare and integrate the principles of the two methods. The objective of this dissertation is to find effective means for integrating the two methods, taking advantage of both. The integration of two methods enhances optimization procedures for energy systems that include power equipment. For example, in addition to the size of heat exchangers, the placement, capacity and parameters of power equipment can also be adjusted to optimize the entire system. Until now, applications of pinch technology's "supertargeting", in order to determine optimal pinch temperature differences, has been limited to heat exchangers. Supertargeting is extended here, accounting for the cost of both heat exchange and power equipment. This dissertation extends the concept of pinch temperature to heat pump applications, where effectively a negative value of the pinch temperature difference occurs. Furthermore, it is shown that, in contrast to the contention that a heat pump should be installed only across the pinch of a heat exchange network, there are other circumstances when a heat pump is appropriate. The application of pinch analysis requires choices to be made, among possible selections and arrangements of process and utility streams. In this dissertation, it is also shown how exergy analysis can, and should, be used to make the choices judiciously, and to avoid choices which would put undue limits on the overall efficiency of a system which incorporates power conversion.
This paper has been withdrawn.