Simulation of Liquefied Natural Gas (LNG) Fluid Flow on Ambient Air Vaporizer

Abstract

An ambient air vaporizer (AAV) is an industrial heat exchanger equipment used in the vaporization process of liquefied gases before supplying to consumers. AAV utilizes the simple heat transfer principle that uses surrounding ambient air to vaporize the liquefied gases. Liquefied Natural Gas (LNG) is one of the liquefied gases commonly associated with AAV applications. Due to a significant temperature difference between cryogenic fluid of LNG and ambient air, frost formation is inevitable to reduce the heat transfer rate. Fins geometry contributes a substantial impact on the performance of AAV and is the main element of heat transfer for AAV. This study aims to design a model of an AAV with a star 6-finned tube vaporizer with hexagon shape and to simulate the fluid flow on the vaporizer model to demonstrate the LNG vaporization process. The hexagon vaporizer model is designed using Solidworks, and heat transfer model is simulated using computational fluid dynamics (CFD) tool, Ansys Fluent solver. Parameters such as fin geometry, LNG flowrate and wind speed were referred from previous studies. Methane and air are assumed as working fluids inside and outside of the vaporizer model. Wind temperatures of 300K (27°C), 303K (30°C), and 306K (33°C) are utilized in the simulation process based on geometrical weather in Malaysia. In the simulation model, methane entered from the bottom of the tube, while air entered horizontally at x-direction from the right side. The temperature contour shows that as the temperature of methane that flowed inside the tube increased as it entered the tube, the air temperature reduced as it entered and flowed passes through the finned tube. The analysis from the simulation model shows that higher air temperature with substantial wind speed can increase the outlet temperature of methane (LNG), thus improving the performance of AAV.