Experimental Study on the Resistance and Splash Performances of Water Collecting Devices for Mechanical Draft Cooling Towers

In recent years,water collecting systems,with the associated advantages of energy saving and noise reduction,have become the foundation for the development of a scheme to optimize the structure of cooling towers.To explore the feasibility of this approach for mechanical draft cooling towers,a small-scale experimental device has been built to study the resistance and splash performances of three U-type water collecting devices(WCDs)for different water flow rates and wind speeds.The experimental results show that within the considered ranges of wind speed and water flow rate,the pressure drop of the different WCDs can vary significantly.The resistance and local splash performances can also be remarkably different.Some recommendations about the most suitable system are provided.Moreover,a regression analysis of the experimental data is conducted,and the resulting fitting formulas for resistance and splash performance of WCD are reported.

WEAKLY SWIRLING TURBULENT FLOW IN TURBID WATER HYDRAULIC SEPARATION DEVICE

This article deals with the characteristics of weakly swirling turbulent flow field in a Turbid Water Hydraulic Separation Device （TWHSD） through experimental and numerical researches. The flow field was measured by PIV, which provided streamlines, vortex structure, vorticity and velocity distribution in different test planes in the TWHSD. On the basis of the experimental results, the tangential and radial velocity distributions of the swirling flow field were obtained. Meanwhile, the numerical simulations were conducted with the RNG κ-ε and RSM turbulence models, respectively. According to the experimental and numerical results, the characteristics of the clear water flow field inside the TWHSD were determined. In view of simulation accuracy and time consumption, it is suggested to apply the RNG κ-ε model instead of the RSM model, which is more time consuming, to make further study on two-phases flow fields in the device.

Hydraulic performance characteristics of impact sprinkler with a fixed water dispersion device

One way to adapt to the trend towards low-energy and to improve the hydraulic performance of the impact sprinkler under a low pressure condition is by means of a fixed water dispersion device.A fixed dispersion device disperses jet flow from the nozzle continuously.The shape of the tip,impact angle(θ),diameter(D),and depth in the jet flow(d)have significant influence on the hydraulic performance.In this study,the hydraulic performance characteristics of impact sprinkler as affected by the fixed water dispersion device were studied under indoor conditions.Radial water distributions from the sprinkler were obtained by experiments for the fixed water dispersion devices.MATLAB was used to transform the radial data into net data,and the uniformities were simulated in a square layout from 1 to 2 times the range(R).The droplet size distributions from the fixed water dispersion devices were measured by a laser precipitation monitor(LPM).Results showed that the range increased with the increase of pressure,and the sprinkler with type C_(2) produced a rectangular-shaped water distribution pattern,while the range was maintained.A maximum uniformity of 71.56%,75.56%,77.23%,73.32%,78.88%and 86.67%was found for types A1,B1,C1,A2,B2,and C_(2),respectively under a pressure of 200 kPa.The uniformity from the sprinkler using type C_(2) surpassed 80%,while type C1 fell below.Droplet sizes from type C_(2) was best,and the mean droplet diameter decreased with the increase of pressure.Hence,type C_(2) can be selected for further optimization of the design features to improve the hydraulic performance of the impact sprinkler under low pressure conditions.