3-D Numerical Simulation On The Thermal Discharge Into Unsteady Fresh And Salt Receiving Water Area

Surface cooling pattern, which cools the units using natural water, is often applied to the power plant cooling engineering in coastal region, cooling water containing a large number of waste heat is discharged into nearby waters by this cooling way, the distribution of heat in receiving waterbody not only get involved with the environment pollution but also take a direct impact on the layout of the drainage projects. Two-dimensional mathematical model is often adopted to forecast temperature distribution in engineering. However, the stratification of cold and hot flow appears near the drainage outlet, owing to the buoyancy effect generated by temperature difference, this situation will be more complicated in fresh and salt water in the estuary area. It not only has important academic value but also has certain engineering application prospects to study the momentum, heat and salinity changing regularity of power plant thermal discharge after injecting into fresh-salt water and analysis the effect of fresh-salt water layered to thermal discharge.In this paper, aiming at the cooling project layout which is of surface drainage and deep intaking, combined with the physical model test on the thermal discharge into the unsteady fresh-salt water mixing area,a numerical simulation about the thermo-hydraulic behaviors in unsteady fresh-salt water mixing area has been conducted using the ECOMSED numerical model The main contents as follows:(1) On the basis of extensive literature consulting, a more comprehensive understanding of the research methods and research status of the numerical simulation about thermal discharge in the cooling project.(2) Combining with the physical model test on the thermal discharge into unsteady fresh-salt water mixing area, the test result from the selecting experiment conditions(upstream runoff:11/s-21/s, water depth:10cm-13cm, salinity:8‰-19.2‰)has provided a lot of experimental data and showed the influence of upstream flow,water depth and salinity on the temperature field.(3) Using the ECOMSED model, three-dimensional hydrodynamic numerical model on the thermo-hydraulic behaviors in unsteady fresh-salt water mixing area is established. The model adopted mode splitting technique. Firstly, with a two-dimensional model to solute the surface elevation and vertical-integration velocity. Secondly, with a three-dimensional model, via sigma coordinate system transformed, to solute the flow field, temperature field and salinity field.(4) The mathematical model has been tested by selecting the experiment conditions with 11/s (upstream runoff),12‰(salinity) and 13cm (water depth),and the numerical simulation results of the tide,velocity,salinity temperature have been compared with the data from the experiment. Analysis results show the numerical model set up in the paper can better reflect transport rule of heat and salinity in unsteady fresh-salt water area.(5) On the basis of model validation, the numerical simulation to the thermal discharge in the fresh-salt water mixing area has been carried out by selecting different experiment conditions(upstream runoff:11/s or 21/s, tidal level:10cm or 13cm, salinity:8‰or 12‰,altogether four groups).(6) Results show that:in the associated parameters variable range, the transport regularity of thermal discharge is different from the homogeneous water. Due to the influence of the stratification, the maximum temperature layer lie in underwater 5cm, and the greater water depth and salinity, the smaller upstream flow, the more obvious stratification in the drainage outlet.