Entropy generation analysis for printed circuit heat exchanger used in small-scale nitrogen expansion natural gas liquefaction refineries: Numerical approach

Abstract

Natural gas liquefaction assisted by the nitrogen expansion process is a growing option for small-scale refineries. The liquefaction process is an energy-intensive process, so choosing a cost-effective main heat exchanger is vital. With the ever-increasing expansion of small-scale liquefaction refineries, printed circuit heat exchangers (PCHEs) are promising candidates with great efficiency due to their small dimensions and high pressure and temperature difference tolerance. In this study, to reduce the LNG temperature, curved channels with fillet corners have been replaced by straight channels. The effects of operation pressure, inclined angle (α), and pitch number (N) on thermohydraulic performance and entropy generation in methane and nitrogen channels were studied. With an increasing inclined angle, a 24.11 % reduction in total entropy generation in the methane channel and a 10.27 % decrease in the nitrogen channel occur at α=45^°and N=10. The closeness of Bijan number to 1 in the methane channel reveals the greater contribution of entropy generation due to heat transfer. For curvy channels, the performance evaluation criterion is greater than 1, which indicates that the structural change of the channel can reduce the negative effects of pressure drop. This research can make suitable steps for optimizing PCHEs in the natural gas liquefaction industry.