Comparison of solutions of LNG heat exchangers used on LNG powered ships

doi:10.11949/j.issn.0438-1157.20181128

Abstract

Abstract:

For the gas supply system used on LNG (liquefied natural gas) powered ships, propane and 50% aqueous solution of ethylene glycol are used as the intermediate heat exchange medium at the given low pressure condition. Choose the heat transfer correlation of spiral tubes and shell side heat transfer correlation for the heat exchanger. Then calculate the heat transfer area and the length of the coiled tubes of the spiral wound LNG heat exchanger (SWHE) with MATLAB programming software. Combined with engineering practice, the distribution of the tube length and heat transfer area when using two-stage heat exchangers are discussed. The HYSYS simulation results show that when the flow and the heat exchange state of the LNG in the pipe are the same, the mass flow rate of the required water glycol is 10 times that of the mass flow rate of propane. Due to the phase change of propane, the flow rate of gaseous propane on the shell-side of the heat exchanger that varies greatly, which can reach 1.7 m/s at the exit. So it requires the heat exchanger to have a higher resistance to pressure. The flow rate of water glycol in the shell side is only about 0.2 m/s. When it is divided into two-stage heat exchangers, the heat exchange area and the length of the tubes of the gasification stage are less than 12.7% of that of the heating stage. When the two stages are the same size, at least 80% of the heat exchange area is wasted. The selected heat exchanger is used on the LNG powered ship. Both space utilization and safety are required. After the calculation, it is believed that although propane changes phase, the heat transfer advantage is not obvious and the safety advantage is not as good as water glycol.

摘要：

针对用在LNG动力船上的供气系统，在给定的低压供气条件下，分别以丙烷和50%浓度的乙二醇水溶液作为中间换热介质，整理适合绕管式换热器的螺旋管传热关联式和壳程传热关联式，使用MATLAB编程计算绕管式LNG气化器的换热面积和换热管长，结合工程实践，讨论使用两级换热器时管长和换热面积的分配情况。HYSYS模拟结果表明，当管内LNG的流动换热状态一样时，所需水乙二醇的质量流量是丙烷的10倍。丙烷发生相变，气态丙烷在绕管式换热器管外的流速变化很大，在出口达到1.7 m/s，换热器所需承压能力较高，水乙二醇在壳程流速仅0.2 m/s左右。分为两级换热器时，气化级换热器的换热面积和换热管长小于加热级的12.7%，当选择两级尺寸相同时，会浪费至少80%的换热面积。

CLC Number:

TQ051.5

TIAN Yajie, LIN Wensheng. Comparison of solutions of LNG heat exchangers used on LNG powered ships[J]. CIESC Journal, 2018, 69(S2): 141-146.

田雅洁, 林文胜. 船用绕管式LNG气化器方案对比[J]. 化工学报, 2018, 69(S2): 141-146.

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