Fundamental research on the condensation heat transfer of the hydrocarbon-mixture energy in a spiral tube described by a universal model using flow pattern based and general modes

The transportation of liquefied natural gas (LNG) is a crucial aspect of global energy application and security. However, there are still some challenges in liquefaction. This study establishes systematic experiments to investigate the condensation two-phase flow and heat transfer process of hydrocarbon-mixture energy (methane/ethane/propane/isobutane) in a spiral tube. The main influencing parameters, including mass flux (200–560 kg/(m²·s)), operating pressure (2–4 MPa), and vapor quality (0–1) on the heat transfer intensity and frictional pressure drop were analyzed. Different two-phase flow patterns were observed and categorized them as bubble flow, intermittent flow, stratified-wavy flow, and annular flow. For bubble flow and intermittent flow, vapor quality is found to remarkably affect the heat transfer; regarding stratified-wavy flow and annular flow, gravitational force and inertia force are found to prominently influence the heat transfer, respectively. Additionally, a newly universal model includes split flow patterns mode (SFPM) and the general mode (GM) has been proposed, which is with high-precision for describing the condensation heat transfer coefficients of different flow patterns. Furthermore, the analytical results show the SFPM's root mean square error and mean absolute relative deviation are 97.35 W/(m²·K) and 0.036.