Exergy Based Analysis of Gas Liquefaction Cycles

Abstract: Cryogenic liquefaction systems has greater importance in recent years due to the application of cryogenic fluids in engineering and other scientific researches on different parts of worlds. The main scope of this systems includes the design, development and improvement of various components in order to provide the best working conditions. A designer has to fix parameters such as number of heat exchangers, working pressures and flow diversions etc. as they play important role in heat transfer. Exergy analysis considered as a useful method to analyse and optimize the design and operation of these liquefaction systems. This study concentrates on exergy analysis of cycles commonly used for the liquefaction of gases in order to evaluate and compare their performance under given working conditions and system component efficiencies. The cycles considered are simple Linde-Hampson cycle, Claude cycle and Collins cycle respectively. Systematic evaluation of important operating parameters has been done to determine the exergy destructions in components as well as in the entire cycles. Compressor pressure, expander flow rates are some of the parameters considered during the analysis. The process flow diagrams, simulations of these cryogenic cycles are done with the help of the simulation tool Aspen HYSYSTM. All calculations are done at steady state and the results hence obtained. Detailed exergy-based analyses are performed upon the various processes and the exergy destruction in each component also found.

Keywords: Exergy, Liquefaction, Heat Exchanger, Expander, Compressor, Pressure.