Development and use of exergy efficiency for complex cryogenic processes

Abstract

In this paper, exergy efficiencies, which are effective performance parameters for cryogenic processes, are categorized based on their exergy decomposition levels. However, the existing efficiencies are not standardized for a variety of unit operations. Thus, the extension of the exergy transfer effectiveness (ETE) has been suggested with a general mathematical expression. The extended ETE is defined by decomposing both thermo-mechanical and chemical exergy to the chemical component level. A case study with a complex natural gas liquefaction process and its optimization has also been performed. The results indicate that the extended ETE brings consistent and accurate results for all types of units, also properly reflecting the changes in process performance after optimization. Other efficiencies, however, struggle to measure the performance improvement for some equipment, even showing decreases in their efficiency values.

Optimal Utilization of Compression Heat in Liquid Air Energy Storage

“…This is done by a careful identification of exergy sources and sinks, and the definition of ETE is the ratio between the exergy sinks (exergy increases) and the exergy sources (exergy reductions) in a process, as is given by eq . While the original ETE only considered thermo-mechanical exergy, the concept of ETE was further extended by Kim and Gundersen , to also consider chemical exergy. η Ė = E T E = ∑ Exergy Sinks ∑ Exergy Sources …”