Study Of Flow And Heat Transfer Characteristics For Transcritical LNG Inner Tube

Natural gas consumption in China is ever-growing, but the studies of the related equipment technology are relatively backward, seriously hindered the development of China’s natural gas industry. SCV is the key equipment of LNG receiving terminal, but there were little researches on it. This paper uses the CFD method, to study the flow and heat transfer characteristics for transcritical LNG in SCV tube.1) Comparing the properties of LNG and CH4 under different pressure, it can conclude that it is suitable for using CH4 to replace LNG to perform the numerical simulation when the pressure is much higher.2) Using a 2-D axisymmetric model to simulate the flow field of supercritical CH4 and heat transfer characteristics in the whole pipe. Meanwhile, the effects of the pressure, water bath temperature and mass flux on the flow field and heat transfer are analyzed. The results show that local heat transhfer coefficient h reaches peak under critical temperature and it can be improved the heat transfer. Also, h increases with the increasing of pressure and decreases with the increasing of water bath temperature. What’s more, the mass flux has a great influence on the h, in other words, the h increases greatly with the increasing of mass flux.3) Establishing a 3-D model of the straight pipe to study the effect of gravity on supercritical CH4 flow and heat transfer. Under the action of gravity, the flow and heat transfer along the circumferential direction of the pipe are distorted because of nonuniform density field. It also shows that gravity can enhance the heat transfer of supercritical CH4, especially in the vivinity of pseudo-critical point. Plus, with the increase of the mass flux, Ri decreases and the effects of free convection become weak.4) Using the 3-D model, the paper studies the effects of secondary flow on supercritical CH4 flow and heat transfer in the U tube. Under the action of centrifugal force, the distributions of flow and heat transfer along the circumferential direction of the U tube are nonuniform. Secondary flow can enhance the heat transfer, and h is much greater in a U tube than in a straight one. Meanwhile, secondary flow can be enhanced by improving the mass flux. The free convection because of gravity can be neglected in the U tube. Secondary flow affects the flow and heat transfer in the follow-up straight pipe; within that range, heat transfer can be enhanced.