半冷半压式液化石油气船再液化系统热力研究

Cold Half Pressure Type of LPG Ships and Thermodynamic Study of Its Reliquefaction System

随着液化石油气(LPG)使用量的日益增长,海上液化气运输得到了飞速的发展,使得国内外对LPG船的需求量急剧增加.其中半冷半压式LPG船是国内制造较多的船型,再液化系统是该型船的关键设备.从半冷半压式LPG船可以运输的液货工质种类入手,为再液化系统选择合适的制冷循环类型,在不同的设计压力和制冷量下,经过热力计算得出循环中各点的热力参数,进而得出高低压级压缩机排量比、功率和单级压缩机功率.通过分析比较,给出了再液化系统中液货罐设计压力、两级压缩系统的选择方法,以及单级和两级压缩系统的选择和切换方法,以期为再液化系统的设计提供参考.

With the increasing application of liquefied petroleum gas （LPG）,the tranapartation of offshore liquefied petroleum gas has been developed rapidly,which makes the demand for LPG ships increase sharply at home and abroad.The cold type of LPG ships is the type mostly manufactured in our country and its key equipment is a reliquefaction system.Considering the different species of liquid materials which could be transported by this type of LPG ships,the most adaptive refrigeration cycle was selected.Under different designed pressures and different amount of refrigeration,the thermodynamic parameters at various points of the cycle were calculated.The displacement ratio of the high to low stages of the compressor,the power consumption of the comperssor and the power consumption of the single stage of the compressor were further obtained.Through analysis and comparison,the design pressure in the liquid cargo tank,the selection method for the two stages of compression system and the switching method between the two stages were provided.The results give reference to the design of reliquefaction systems.