Exergy analysis of helium liquefaction systems based on modified Claude cycle with two-expanders

Large-scale helium liquefaction systems, being energy-intensive, demand judicious selection of process parameters. An effective tool for design and analysis of thermodynamic cycles for these systems is exergy analysis, which is used to study the behavior of a helium liquefaction system based on modified Claude cycle. Parametric evaluation using process simulator Aspen HYSYS® helps to identify the effects of cycle pressure ratio and expander flow fraction on the exergetic efficiency of the liquefaction cycle. The study computes the distribution of losses at different refrigeration stages of the cycle and helps in selecting optimum cycle pressures, operating temperature levels of expanders and mass flow rates through them. Results from the analysis may help evolving guidelines for designing appropriate thermodynamic cycles for practical helium liquefaction systems.

Research highlights
► Scope of exergy analysis as a design tool for large-scale helium liquefier explored.
► Optimum compressor flow diversion to the expanders determined by exergy analysis.
► Computed the distribution of loss in the components of cycle at various conditions.
► Suggested addition of more stages to basic cycle to increase its exergy efficiency.
► Suggested a way to decrease the loss in the lowest temperature heat exchanger.