The Performance of Low-Pressure Seawater as a CO2 Solvent in Underwater Air-Independent Propulsion Systems

Abstract

Air-independent propulsion systems have improved the performance and decreased the vulnerability of underwater weapon systems. Reforming systems, however, generates large amounts of water and CO2. The recovery or separation of CO2, a residual gas component generated in vessels, entails considerable cost and energy consumption. It is necessary to understand the characteristics of the interaction between CO2 and seawater under the conditions experienced by underwater weapon systems to design and optimize a CO2 treatment process for dissolving CO2 in seawater. In this study, numerical analysis was conducted using the derived experimental concentration and MATLAB. The diffusion coefficient was derived as a function of temperature according to the CO2 dissolution time. Experiments on CO2 dissolution in seawater were conducted. The concentration of CO2 according to the reaction pressure and experimental temperature was obtained. The diffusion coefficient between CO2 and seawater was found to be 6.3 × 10−5 cm2/s at 25 °C and 7.24 × 10−5 cm2/s at 32 °C. CO2 concentration could be estimated accurately under vessel operating conditions using the derived CO2 diffusion coefficients. Optimal design of the residual gas treatment process will be possible using the derived seawater–CO2 diffusion coefficients under the actual operating conditions experienced by underwater weapon systems.

The Ocean’s Elevator: Evolution of the Air-Seawater Interface During a Small-Scale Algal Bloom

“…84 Representative diffusion coefficients ranging from 7 × 10 -5 cm 2 s -1 to 1 × 10 -5 cm 2 s -1 demonstrate the lower and upper bounds for several atmospheric gases in a range of ocean relevant temperatures. [85][86][87][88][89] Seemingly, as the film becomes more concentrated throughout the bloom and the film thickness increases, the film permeability decreases. Interestingly, gases with larger diffusion coefficients show a more apparent exponential decrease in their permeability concurrent with film thickness, and are more greatly impeded by film thickness possibly due to the longer elapse of time required to permeate the film and the abrupt nature of physical aging resulting from the inherent kinetic nature of transitioning through the film.…”