Thermal hydraulic characteristics of trans-critical natural gas flowing through staggered S-shaped fin microchannel

Abstract

As a newly-developed microchannel heat exchanger, printed circuit heat exchanger (PCHE) is employed as the primary LNG vaporizer in floating storage and re-gasification unit for high efficiency and compactness. In this paper, thermal–hydraulic characteristics of trans-critical NG through the improved staggered S-shaped fin channels were numerically investigated. Variation tendencies of fin performance under different operating pressures and a wide range of Reynolds numbers were analyzed. Sensitivity analyses on the effect of various thermophysical properties on heat transfer around pseudo-critical temperature revealed that heat transfer capacity were deeply affected by specific heat, and effects of thermal conductivity and viscosity could be canceled each other. Additionally, to further estimate forced convective heat transfer mechanism, common features of HTC and f factor distributions were analyzed and some reasonable criteria were also discussed. The results showed that except for a few data points across critical temperature affected by entrance effect, the peak HTC always appeared in the vicinity of the pseudo-critical points. Furthermore, the Bo of 10-5 and q+ of 5×10- 4 could be adopted to analyze buoyancy and flow acceleration influences qualitatively. The simulated results agreed with the predictions from Ngo Correlation within 16.32% and 12.36% errors respectively for HTC and f factors, which implied that though the drastic local changes of performance tendency could not be predicted well, suitable correlations were sufficiently accurate for engineering applications.