Simulation of performance of intermediate fluid vaporizer under wide operation conditions
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RESEARCH ARTICLE
Bojie WANG, Wen WANG, Chao QI, Yiwu KUANG, Jiawei XU
Simulation of performance of intermediate fluid vaporizer under wide operation conditions
© Higher Education Press 2020
Abstract The intermediate fluid vaporizer (IFV) is a typical vaporizer of liquefied natural gas (LNG), which in general consists of three shell-and-tube heat exchangers (an evaporator, a condenser, and a thermolator). LNG is heated by seawater and the intermediate fluid in these heat exchangers. A one-dimensional heat transfer model for IFV is established in this paper in order to investigate the influences of structure and operation parameters on the heat transfer performance. In the rated condition, it is suggested to reduce tube diameters appropriately to get a large total heat transfer coefficient and increase the tube number to ensure the sufficient heat transfer area. According to simulation results, although the IFV capacity is much larger than the simplified-IFV (SIFV) capacity, the mode of SIFV could be recommended in some low-load cases as well. In some cases at high loads exceeding the capacity of a single IFV, it is better to add an AAV or an SCV operating to the IFV than just to increase the mass flow rate of seawater in the IFV in LNG receiving terminals. Keywords liquefied natural gas, intermediate fluid vaporizer, heat transfer performance, numerical simulation, extreme condition
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Introduction
At present, natural gas (NG) has become one of the most popular energy sources because of its advantages of cleanness and safety. Liquefied natural gas (LNG) is Received Jul. 24, 2019; accepted Mar. 14, 2020; online Jul. 10, 2020
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Bojie WANG, Wen WANG ( ), Chao QI, Yiwu KUANG Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200240, China E-mail: [email protected] Jiawei XU CNOOC Gas and Power Group, Beijing 100027, China
convenient for transportation. However, LNG should be vaporized and heated before it is conducted into the public domain network. There are several types of vaporizers and heat exchangers employed in LNG receiving terminals, for example, ambient air vaporizer (AAV), open-rack vaporizer (ORV), submerged-combustion vaporizer (SCV), and intermediate fluid vaporizer (IFV), etc. IFV is of complicated structure, but has some advantages as well, i.e., compact volume, no icing, low requirement for seawater, and low operation cost [1]. Therefore, IFVs have been increasingly employed in LNG receiving terminals at present. An IFV usually consists of three shell-and-tube heat exchangers, namely, the evaporator, the condenser, and the thermolator respectively [2,3]; the LNG is heated by intermediate fluid rather than by seawater directly, as shown in Fig. 1. In actuality, warm water or air [4] can be used as the alternative heat source in some cases where seawater is used restrictedly due to environmental consideration. Intermediate fluid plays an important part in IFVs. Xu et al. [5] discussed several refrigerants as intermediate fluids and compared the required heat transfer areas of IF
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