A 3E (Energy, Exergy, and Economic) comparative analysis for a novel methane-nitrogen finned channel printed circuit heat exchanger at supercritical pressures in small-scale natural gas liquefaction refineries

• New longitudinal finned channel structures were proposed. • The influence of operating pressure on heat transfer and flow was investigated. • The influence of finned channels on PCHE’s effectiveness was investigated. • The influence of variable cross-section channel on thermoeconomic cost was studied. • New Nusselt number correlations for methane at supercritical pressures were proposed. Printed circuit heat exchangers (PCHEs) using nitrogen as a renewable coolant are a progressive candidate in small-scale natural gas liquefaction refineries. In response to the increasing global focus on LNG production due to the global warming challenges, this study provides a 3E analysis of the effect of longitudinal fins on the cooling process of methane at supercritical pressures. An economic evaluation based on the second law of thermodynamics applies to a counter-flow PCHE. Parameters such as Nusselt number, Richardson number, PCHE effectiveness, performance evaluation criterion, rational efficiency, and thermodynamic-economic cost are analyzed. The capital cost and the irreversibility penalty cost make the total cost of the PCHE. The results predict that the irreversibility cost can be 20 times the capital cost. The comparative results reveal that by sinusoidalizing and applying one longitudinal rectangular fin, the PCHE effectiveness increases by 6.34 %, the total entropy generation decreases by 9.1 %, the methane outlet temperature decreases by 7.57 %, the rational efficiency rises by 2.68 %, and 9.77 % reduction in thermodynamic-economic cost are obtained compared to the fin-less straight channel. This study proposes new Nusselt number correlations for methane at supercritical pressures. This study can expand the feasibility of small-scale natural gas liquefaction units to use this clean fossil fuel.