Numerical investigation of the effect of hot-water outlet inclination angle on the temperature dilution in open channel flow

Abstract

In this study, the authors investigated the environmental impact of discharging hot water from a thermal power plant into a water source for cooling. Three hundred forty-three runs using two-dimensional numerical ANSYS Fluent simulation model with (k- ε) turbulence model and open channel flow characteristics was applied in this research. The single port submerged discharge inclination angle was studied with different scenarios for the hot-water outlet (velocity and temperature) to determine the optimum inclination angle to increase cooling system efficiency and reduce hot water's environmental impact. It was discovered that by increasing the inclination angle and velocity of the hot-water outlet, the efficiency of cooling system is increased, as it increased the dilution of the hot water and reduced its environmental impact. Specifically, inclination angle of 15° increased the dilution by 80% and 86% in x and y directions, respectively compared to angle 90°. Additionally, the temperature variation in water body induced by hot-water outlet was reduced by counter flow at angle −15°. The velocity profile showed a recirculation region at the right side of the hot-water outlet, which was reduced at higher inclinations. A mathematical equation was developed to estimate the temperature value in the open channel water body based on the study parameters. Overall, the study found that increasing the inclination angle of the hot-water outlet can significantly improve the cooling system's efficiency and reduce the environmental impact of the hot water discharge. Counter flow conditions were unsuitable because they have less dilution than the normal flow conditions.