Experiments on Oxygen Desorption from Surface Warm Seawater under Open-Cycle Ocean Thermal Energy Conversion (OC-OTEC) Conditions

This paper reports the results of scoping deaeration experiments conducted with warm surface seawater under open-cycle ocean thermal energy conversion (OC-OTEC). Concentrations of dissolved oxygen in seawater at three locations (in the supply water, water leaving a predeaerator, and discharge water from an evaporator) were measured and used to estimate oxygen desorption levels. The resultssuggest that 796 to 6096 of dissolved oxygen in the supply water was desorbed from seawater in the predeaerator for pressures ranging from 9 to 3.5 kPa. Bubble injection in the upcomer increased the oxygen desorption rate by 2096 to 6096. The dependence of oxygen desorption with flow rate could not be determined. The data also indicated that at typical OC-OTEC evaporator pressures when flashingoccurred, 7.596 to 9.596 of dissolved oxygen was desorbed overall from the warm seawater. The uncertainty in results is larger than one would desire. These uncertainties are attributed to the uncertainties and difficulties in the dissolved oxygen measurements. Methods to improve the measurements for future gas desorption studies for warm surface and cold deep seawater under OC-OTEC conditionsare recommended.