A thermodynamic review of cryogenic refrigeration cycles for liquefaction of natural gas

•Cryogenic refrigeration cycles are investigated for the liquefaction of natural gas.•The cycles are classified from a thermodynamic viewpoint and with new nomenclature.•Sixteen different cycles are selected and their optimal conditions are presented.•This review can be a thermodynamic basis for designing an efficient LNG process. A thermodynamic review is presented on cryogenic refrigeration cycles for the liquefaction process of natural gas. The main purpose of this review is to examine the thermodynamic structure of various cycles and provide a theoretical basis for selecting a cycle in accordance with different needs and design criteria. Based on existing or proposed liquefaction processes, sixteen ideal cycles are selected and the optimal conditions to achieve their best thermodynamic performance are investigated. The selected cycles include standard and modified versions of Joule–Thomson (JT) cycle, Brayton cycle, and their combined cycle with pure refrigerants (PR) or mixed refrigerants (MR). Full details of the cycles are presented and discussed in terms of FOM (figure of merit) and thermodynamic irreversibility. In addition, a new method of nomenclature is proposed to clearly identify the structure of cycles by abbreviation.