Objectives  With LNG refueling ships becoming a trend, the development of LNG bunker vessels can make up for the shortage of LNG refueling efficiency in ports. The design success or failure of the LNG refueling tank will directly affect a ship's performance, economy and safety.

  Methods  First, parametric modeling is carried out for the type C tank. Taking a double-type C tank as an example and combining the features and functions of the LNG refueling ship, an evaluation system consisting of four indexes is established for the tank. On this basis, the analytic hierarchy process (AHP) and fuzzy theory are adopted to obtain the weight of the indicators. We then construct a function with the size and shape of a type C tank as the optimization objectives, and calculate the optimal solution of the type C tank. Taking an LNG refueling ship as an example, the optimized size is compared with the real type C tank.

  Results  The results show that the optimization degree is positive at about 0.53%, which illustrates that the optimized size improves the evaluation value and design.

  Conclusions  This study shows that it is feasible to adopt this evaluation method into the optimal design, which can be used to quickly and accurately obtain the size and shape of a type C tank in the concept design stage, thereby saving the design cost and improving design efficiency.