Ministry of Transportation of the Republic of Indonesia has conducted a feasibility study for conversion plans with the use of 60% LNG fuel on its 3200 DWT passenger ship using LNG ISOtank type T75 size 20 feet (1 TEU), but only limited to economical study. To verify that the conversion plan is really profitable, analysis of physical exergy characteristics i.e. the rate of exergy transfer and destruction through tank wall due to heat transfer, boil-off rate and boil-off gas from stored LNG is conducted by a closed system exergy balance approach with specified shipping conditions parameters, using the empirical equations of the literature and physical model of the three tank options offered, designed using COMSOL Multiphysics 5.1. The results show a positive correlation between exergy destruction rate with BOR and BOG values, depending on the total thermal resistance value Rtot due to material variation of shell and insulation of tank wall affecting the value of heat leak on the inner and outer surface of the tank wall. Quality scale is presented to summarize the analysis parameters that can be measured by cost, i.e. the exergy cost and operating costs required by forced vaporizer to achieve the required BOR.
Keywords: dual fuel, retrofit, LNG, heat leak, physical exergy, exergy transfer. exergy destruction, boil-off gas, ISO-tank.