Numerical Investigation On The Heating Of Supercritical Methane In A Printed Circuited Heat Exchanger

Nowadays,with the increasing demand of LNG in China,LNG terminals and floating storage regasification unit(FRSU)have developed rapidly in coastal areas.As a common type of LNG regasifier,the intermediate fluid vaporizer(IFV)serves well in many LNG terminals,and the most widely used heat exchanger for IFV is shell-and-tube heat exchanger.However,recent decades have witnessed the birth of a newly developed heat exchanger,namely,printed circuit heat exchanger(PCHE).With the advantages of higher heat transfer coefficient and better compactness,PCHE may be a promising candidate for IFV's heat exchanger.This paper numerically investigates the thermal hydraulic performance of supercritical methane in different types of PCHEs,by CFD code ANSYS FLUENT.First,the heating process of supercritical methane in a single horizontal tube is investigated numerically.Since the properties of supercritical fluid have drastic changes with during the heating and an extreme value may occur at its pseudo-critical point,the FLUENT database could not evaluate the accurate property value during the calculation.Thus the author set the value of supercritical methane's properties as functions of its temperature.Mass flux,inlet pressure,heat flux and the convection coefficient of intermediate fluid are set as variables.As a result,the semi-circular channel has a better performance than circular tunnel in terms of heat transfer coefficient.The results show that the surface heat transfer coefficient peaks at the pseudo-critical point.Besides,it increases with the increase of mass flux and heat flux.It seems that the inlet pressure and the convection coefficient of intermediate fluid have very little effect on the surface heat transfer coefficient.Second,the heat transfer performance of supercritical methane and water in straight and zigzag PCHE is studied numerically.The effects of geometrical parameters on the Nusselt number and the Fanning factors are analyzed by CFD code and the results of numerical simulations are compared to eTistent correlations.For straight PCHE,the most influential geometrical parameters are t_b and d.And for zigzag PCHE,the inclined angle?has impact on both heat transfer coefficient and pressure drop while the pitch number P only influences the pressure drop.Taking the geometrical factors,t_b and d,into consideration,we developed new correlations of Nu and f for straight PCHE by modifying the empirical correlations.The RMS errors of the straight PCHE correlations are 6.73%for Nusselt number and 9.56%for Fanning factor.Moreover,the new correlations for zigzag PCHE are modifications of straight PCHE correlations.And the RMS errors of the zigzag PCHE correlations are7.88%for Nusselt number and 10.86%for Fanning factor.Third,the heat transfer performance of supercritical methane and other intermediate fluids(propane,glycol solution)in straight PCHE is investigated.The effects of propane's temperature and mass flux,glycol solution's concentration and inlet temperature are analyzed by Nusselt number and Fanning factor and the results are compared to the correlation generated from the second part.At last,two experimental schemes regarding to the gasification of LNG and the liquefaction of methane in three types of PCHEs are proposed.Although the experiments are not carried out yet,there may be some useful information for other researchers in the experimental proposals.