Physical and Numerical Modeling of the External Fluid Mechanics of OTEC Pilot Plants

摘要

This study examined the near field external fluid mechanics of symmetrical OTEC pilot plant designs (20 to 80 MWe) under realistic deep water conditions. The objective was to assess the environmental impact of different plant configurations and to determine if pilot plants can be expected to operate without degrading the thermal resource available for power production. Physical modeling studies were conducted to investigate the variation of near field plume dynamics and the sensitivity of recirculation to different pilot plant designs. Experiments were conducted in a thermally stratified 12m x 18m x 0.6m basin, at an undistorted length scale ratio of 1:300, which allowed the upper 170m of the ocean to be studied. Measurements included temperature, dye concentration and visual observation from photographs. Both mixed and non-mixed discharge concepts were investigated. Discharge port design included two, four or eight discrete circular ports, with significant variations in the MWe/port ratio, issuing either horizontally or vertically. A range of ambient uniform current speeds was investigated while an ambient density profile, representative of potential sites off of Hawaii and Pureto Rico, was chosen. A previously calibrated integral jet model was tested against experimental observation to develop a valid, predictive tool that would facilitate study of conditions that were not modeled with the present experimental set-up. The model was modified to more accurately represent the dynamics of the OTEC discharge in the near field. The potential environmental impact of the discharge plume from an OTEC plant over a broad range of realistic conditions was assessed through additional sensitivity simulations. Results indicate that little recirculation occurs for the designs considered in this study. The recirculation that does occur appears to be the result of plume upwash in the lee of the plant and, possibly, internal wake effects on the plant bow. (ERA citation 08:014406)