فهرست مطالب b. khorsandi

With the reduction of natural sources of fresh water, the activity of desalination factories is increasing. The effluent of these factories is returned to the sea environment. The effluent contains a lot of chemicals and salt, which in case of improper discharge will disturb the balance of the sea environment. Using numerical models to check different discharge methods is one of the cheapest methods. In this research, the results of CORJET, VISJET and RNG (k-ε) models are validated for the discharge of concentrated wastewater. For this purpose, the simulation results of these models in static and dynamic environments are compared with the results of various laboratory studies. According to the results, the RNG model estimates the axial velocity of the jet well and with a small error compared to the integral and laboratory models. All three models estimate most of the parameters related to the discharge of concentrated wastewater in comparison with the laboratory studies. CORJET and VISJET models estimate the amount of effluent dilution with a high error, but the RNG model estimates the amount of effluent dilution with an acceptable error due to the consideration of flow turbulence. The most important advantage of CORJET and VISJET integral models is easy modeling and very low calculation time compared to RNG turbulence model. According to the presented results, it can be concluded that the RNG model is suitable for carrying out studies related to the discharge of concentrated wastewater from desalination plants due to considering the flow turbulence and providing accurate results.

In recent decades, the increase in desalination plant construction along coastlines due to climate change and fresh water resource depletion has been a major concern. The discharge of concentrated wastewater directly into the sea has been shown to cause irreversible damage to the environment. Therefore, the use of appropriate dischargers is crucial in reducing the negative environmental effects of this waste. In this study, ANSYS-FLUENT software was used to simulate the behavior of condensed effluent discharged from circular, triangular, and diamond nozzles. To investigate the effect of nozzle geometry, diamond and triangle nozzles with different dimensions (triangle 1, triangle 2, diamond 1, and diamond 2) were modeled. The effluent was discharged obliquely at a discharge angle of 60 degrees to the horizon in both static and dynamic water environments. The K-ε turbulence model (RNG) was employed for modeling, and the results were validated by comparison with experimental data. The results showed that the height of the maximum jet ascent and the horizontal distance of the point of impact of the effluent with the ground decrease, while the dilution rate of the effluent increases as it leaves the nozzle in a sheet. Moreover, the results indicated that the spreading rate at the inner edge of the jet is lower than that at the outer edge of the jet due to the presence of the bed and the Coanda effect. However, the nozzle geometry was found to have no effect on the reduction of concentration in the center line of the jet. The use of diamond 2 and triangle 2 nozzles for the discharge of concentrated wastewater was found to reduce environmental damage. The findings of this study provide insight into the design of appropriate dischargers for desalination plants and highlight the importance of considering environmental impacts when discharging waste water.