Parameter study and multi-objective optimization analysis on gasification characteristics of supercritical methane in a submerged combustion vaporizer

Submerged combustion vaporizer (SCV) is widely utilized in the field of low-temperature thermal engineering. The tube bundles of SCV typically behave straight sections and bend. However, the design of such serpentine tube for supercritical methane (S-CH4) gasification remains challenging. A relatively comprehensive parameter study and multi-objective optimization analysis considering main operating conditions and geometric parameters are also needed. This paper presents a numerical simulation on gasification heat transfer performance of S-CH4 in a serpentine tube, analyzing coupled effects of buoyancy, flow acceleration and centrifugal force. The parameter study reveals that the performance evaluation criterion of S-CH4 is mainly dominated by inlet velocity and pressure, yet the geometric parameters have limited influence. Small-curvature bend shows more uniform thermos-physical properties distribution within the boundary layer. The evolution of Morton and Dean vortices related to gasification performance exhibits a non-linear behavior characterized by initial expansion, followed by contraction and breakdown. Whereupon, a multi-objective optimization analysis through 54 specifical-design numerical cases is performed utilizing Response Surface Methodology. The second-order polynomial regression models for Nusselt number and pressure drop of S-CH4 are ultimately traced. These findings serve as a foundation for improving the thermal design of SCV and other supercritical heat exchangers.