This study analyzes the thermodynamic, economic, and regulatory aspects of boil-off hydrogen (BOH) in liquid hydrogen (LH₂) carriers that can be re-liquefied using a proposed re-liquefaction system or used as fuel in a fuel cell stack. Five LH₂ carriers sailing between two designated ports are considered in a case study. The specific energy consumption of the proposed re-liquefaction system varies from 8.22 to 10.80 kWh/kg as the re-liquefaction-to-generation fraction (R/G fraction) is varied. The economic evaluation results show that the cost of re-liquefaction decreases as the re-liquefied flow rate increases and converges to 1.5 $/kg at an adequately large flow rate. Three energy efficient design index (EEDI) candidates are proposed to determine feasible R/G fractions: an EEDI equivalent to that of LNG carriers, an EEDI that considers the energy density of LH₂, and no EEDI restrictions. The first EEDI candidate is so strict that the majority of the BOH should be used as fuel. In the case of the second EEDI candidate, the permittable R/G fraction is between 25% and 33%. If the EEDI is not applied for LH₂ carriers, as in the third candidate, the specific life-cycle cost decreases to 67% compared with the first EEDI regulation.

CFD Simulations and Experimental Tests for Three Different Ducted Propellers Propeller Open Water Test;Computational Fluid Dynamics (CFD);Ducted Propeller;Propeller Efficiency;Autonomous Underwater Vehicle (AUV); In this study, propeller open water characteristics ($K_P$, $K_T$ and ${\eta}_o$) were compared for three different ducted propellers using a Computational Fluid Dynamics (CFD) analysis, as well as an experimental test at a basin. The best shape of the duct was selected from the three types of specially designed ducts based on the CFD analysis results. The same propeller model (Kaplan type propeller) was used inside all three duct models, and the propeller open water characteristics were compared, predominantly at the design speed for an underwater vehicle. Finally, the results of the CFD test simulations for the selected duct case were verified by experimental open water tests in a towing tank.

In this paper, the discussion trend on Underwater Radiated Noise (URN) from Ships being discussed at the International Maritime Organization (IMO) meeting was shared. In some countries, such as Canada and United States, marine mammals such as whales are severely affected by URN from Ships and Offshore plant facilities. In relation to the regulation of URN, internationally agreed regulations such as greenhouse gas reduction from Ships have not been developed, but awareness of seriousness of the URN is gradually increasing. Accordingly, international policy trends and technology trends for URN from Shipping, which are being dealt with in the IMO meeting, were reviewed. The technology for the URN is divided into measurement and reduction, and the reduction of propeller cavitation is being dealt with as a major technical element. Currently, the actual regulation to reduce the URN from ships is the “restriction on the speed of a ship” implemented at the individual national level. In order to develop coherent international rules and regulations, methods for measuring URN and technologies for URN reduction should be continuously developed.

When an offshore platform topside is constructed in a yard, it should be loaded-out onto a transportation vessel. The load-out operations, however, involves many uncertainties, such as changing the load (weight of the topside platform) on the LSF or possible structural failures. The load on the LSF should be evaluated, as even a small failure in a structural member or a welding connection can lead to structural instability, or even catastrophic structural collapse. This study presents a newly developed method for analyzing the structural reliability of the LSF. The probability of failure is calculated by using AFOSM method assessment along with response surface methods. This proposed approach can provide a better understanding of safety requirements, so that the over-design of structures can be avoided. Furthermore, it can provide the coordinators of load-out operations with a better set of guidelines for determining the probability of failure during the load-out process.