Research On Fluid Flow And Heat Transfer In LNG Submerged Combustion Vaporizer

As the national energy structure adjustment, liquefied natural gas imports increase sharply, more and more LNG terminal have been built at Ports. The submerged combustion vaporizer as main gasification equipment starts quickly and has high thermal efficiency attracted high attention recently, which is a combination of submerged combustion and two-phase flow heat transfer technique. This paper studies the fluid flow and heat transfer in SCV by means of experiment and numerical simulation. Analyzed the tube-side supercritical LNG and shell-side two-phase flow heat transfer process and regressed the heat transfer correlation. Proposed a design thought benefit the localization of SCV.The main work and conclusion are as follows:(1) An experimental apparatus is built up to the flow and heat transfer characterristic of submerged combustion vaporizer. Analyzed the pressure temperature distribution shell hold-up two-phase flow pattern and convective heat-transfer coefficient in experimental result. Provide comparison validation to numerical simulation research.(2) Build numerical model of tube-side supercritical LNG and shell-side two-phase flow heat transfer process, and use actual operation data to prove the reliability of numerical simulation. Tube-side use UDF to handle supercritical LNG physical property. Shell-side use VOF model to deal with two-phase flow heat transfer process.(3) The tube-side supercritical fluid heat transfer numerical simulation study the influent of temperature and flow field operating parameter and secondary flow to heat transfer. Results indicate that, the supercritical fluid physical property variation cause the complexity of tube-side heat transfer. Closer to the critical pressure the higher convective heat transfer coefficient is, and rise wall temperature is the way to get high heat transfer coefficient. Secondary flow lead to the wave of heat transfer coefficient in bend, and the radius of curvature is in inverse proportion to Dean number and heat transfer coefficient. Based on these research, revising the Dittus-Boelter correlation to suit experimental operating conditions.(4) The shell-side gas-liquid two-phase flow heat transfer numerical simulation study the influent of structure and operating parameter to the flow field gas hold-up and heat transfer. Results indicate that, the gas hold-up and interphase contact area are in direct proportion to gas inlet velocity, and in inverse proportion to the initial water level after overflow. The ninety degrees staggered 25x25 tube arrays and 6mm distributor exhaust vent radius have best heat transfer effectiveness. After overflow smaller difference in temperature lead to better heat transfer effectiveness, and with increase of inlet velocity, heat transfer coefficient increases first and then decreases. Based on these research, revising the Zhukauskas correlation to suit two-phase experimental operating conditions.(5) Based on the research both of tube-side and shell-side heat transfer correlation, proposed a thought of SCV design.