Numerical Investigation On Heat Transfer Characteristics Of A Printed Circuit LNG Vaporizer Under Supercritical Pressure

Liquid natural gas(LNG)plays a vital role in alleviating the energy crisis,optimizing energy structure and reducing environmental pollution.With the rapid development of the offshore LNG industry,floating storage and regasification unit(FSRU)has attracted more and more attention.Printed circuit heat exchanger(PCHE)as a typical micro-channel heat exchanger,with the advantages of high temperature resistance,high pressure resistance,safety and reliability,and the heat transfer efficiency is not easily affected by sloshing,is widely used in LNG-FSRU.In this paper,the flow and heat transfer characteristics of printed circuit LNG vaporizer are studied by numerical simulation.The three-dimensional numerical models of straight and zigzag channeled printed circuit LNG vaporizer are established.The condensation heat transfer mechanism and coupled heat transfer mechanism of supercritical LNG/propane in cold/hot channels are revealed.The flow and heat transfer of printed circuit LNG vaporizer under different structural and operating parameters are compared,and the effects of structural and operating parameters on thermal-hydraulic performance are studied.The results show that the temperature distribution of the fluids is mainly determined by the velocity distribution in printed circuit LNG vaporizer,and the condensation process of propane first occurs near the wall of the channel,and then gradually expands to the inside.The channel bending causes the accelerating core of cold and hot fluids close to the inner wall of the corner,thinning or even destructing the boundary layer,which is conducive to convective heat transfer,although causes greater flow resistance.The larger the channel bending angle,the better the heat transfer and the greater the pressure drop.A comprehensive evaluation index is used to investigate the thermal-hydraulic performance of the printed circuit LNG vaporizer,and it shows that the channel bending angle 15° offers the best comprehensive performance.The inlet temperature has little effect on the flow and heat transfer characteristics of the printed circuit LNG vaporizer,while the inlet mass flow rate has a greater effect.An appropriate increase in LNG inlet temperature or an appropriate increase in LNG inlet mass flow rate is conducive to the comprehensive performance of the printed circuit LNG vaporizer,while an excessive mass flow rate of propane causes the decline of the comprehensive performance of printed circuit LNG vaporizer.The research clarifies the flow and heat transfer characteristics of the printed circuit LNG vaporizer,and provides a theoretical basis for the engineering design and efficient operation of the printed circuit LNG vaporizer.