Numerical Simulation Of Icing And Heat Transfer On The Surface Of ORV

Using seawater as heat medium, Open Rack Vaporizer was used in LNG terminals around the coastal areas widely. Once seawater is exposed to a cold surface of heat transfer tube whose temperature is below the icing point, ice will occur on the heat transfer tube, especially the bottom of heat transfer tubes and the collector tubes. Due to the heat resistance of ice, the heat transfer and gasification efficiency of ORV will be decreased rapidly. Therefore it is greatly significant to study the influence of icing on the heat transfer character of ORV, explore the law of icing, energy conversation as well as cost saving.With massive literature review, the heat transfer characteristics and icing on the heat transfer tube of ORV were studied based on heat transfer theory and FLUENT. The main contents and conclusions are as follows:(1)The structure, principle, process and main factors affecting vaporization of ORV were introduced, and the feature and use-condition of ORV were further analyzed comparing with other kinds of vaporizers. According to the different fluid patterns in tube, the total heat transfer process was divided into pure-liquid section, gas-liquid two-phase section and pure-gas section. Aiming at the conditions of icing and no icing on the tube, the heat transfer calculation models were devised respectively for the three heat transfer sections. Finally, the total heat transfer coefficient K was obtained.(2)The heat transfer calculation of fluid-structure interaction for 4 sets of heat transfer tubes were done based on the Realizable k-ε model of FLUENT, and the effects of different film thickness, different inflow velocity of seawater on the heat transfer characters of tube were obtained. The results showed the temperature changing rate and the velocity gradient of LNG in the heat transfer tube and seawater outside the tube all increase with the increasing of the film thickness, and the temperature changing rate and the velocity gradient of LNG and seawater all increase with the increasing of the inflow velocity.(3)The effects of different film thickness and different inflow velocity of seawater on icinging on the heat transfer tubes were numerically analyzed based on the Solidification & Melting model. When the inflow velocity is 0.5m/s, and the film thickness is 1mm, the maximum icing length is 454 mm. The icing of seawater is greatly influenced by the inflow velocity and the film thickness. In the process of seawater falling, the volume fraction of ice increased, the ice layer became thicker gradually, and the obvious areas of icing lay in the bottom of the tubes. In order to prevent the icing of heat transfer tubes, the seawater distributor should be properly placed in the actual running of ORV, as well as the structure of tubes should be designed optimally, which can enhance the heat transfer efficiency of ORV.