Natural Draft Cooling Tower Research Articles

SACTI model in prediction and assessment of large scale natural draft cooling tower environmental impact of nuclear power plant

Large Scale Natural Draft Cooling Tower has become a hot topic in China because it is an important part of the nuclear power plant, and its environmental impacts include shading, solar energy loss, water deposition and salt deposition. In China, there is no built large-scale natural draft cooling tower of nuclear power plant. Therefore, model prediction becomes an effective way to solve this problem. This paper introduces the basic principles and structure of SACTI (Seasonal and Annual Cooling Tower Impact) model. SACTI is a cooling tower assessment model developed by Argonne National Laboratory, USA. A comparative case study between China's Pengze Nuclear Power Plant and the US Amos Power Plant is also presented. Calculations were carried out for the Pengze and Amos power plants, and the results showed that the maximum value of salt deposition at the Pengze plant was about 166.5 kg/(km2-month) at a distance of 800 m from the cooling tower. The maximum value of salt deposition at the Amos plant was about 92.85 kg/(km2-month) at a distance of 600 m from the cooling tower. Conclusions show that the research work can provide a useful solution in future work, the simulation results of the SACTI model have a potential mean in the absence of monitoring data. This research provides a way to generate simulation data through SACTI program in the design process of nuclear power plant cooling tower, and designers can use these data to determine how the cooling tower will affect the natural environment and manage within an appropriate range to reduce the impact on the environment.

Numerical Study on V Shaped Natural Draft Cooling Tower Supporting System

Cooling towers generally used to extract waste heat to the atmosphere from cooling water stream to a lower temperature and hence it rejects heat from water. The size of the cooling tower is large, with thin wall and complex geometry. Wind load plays a dominant role in the design of cooling tower. These cooling towers are subjected to self-weight and dynamic loads such as wind and earthquake. This paper presents the study of cooling tower of height 200m above the ground level. The Analysis of a cooling tower is done for a wind load using a finite element analysis considering V frame shell base supporting system. The analysis is performed in Commercial software STAAD PRO and the results obtained are presented in this paper.

A Study on Dynamic Behavior of Natural Draft Cooling Tower Considering the Effect of Soil-Structure Interaction

In this present era, the technology in advanced construction has developed to a very large extent. Some parts of the constructions are still in the improving stage which includes Cooling tower Construction. Hyperbolic cooling towers are large, thin shell reinforced concrete structures which Contribute to power generation efficiency, reliability, and to environmental protection. Cooling towers use evaporation of water to eject heat from processes such as cooling the circulating water used in oil refineries and in power plants. Nowadays in many thermal power plants, we can see the Cooling tower. So, preserving this industrial structure is an effort to save the cooling tower from dangerous earthquakes. The present-day cooling towers are exceptional structures in view of their sheer size and complexities. Present paper deals with the study of dynamic response that is modal analysis, seismic analysis of the two different cooling towers varying the H/t ratio and thicknesses with fixity at the base boundary condition, and the soil is modelled as raft for the effect of soil-structure interaction using the direct approach. In this paper, hyperbolic cooling towers are modelled using Ansys software, which is a Finite element Software. Results show that the soil-structure interaction effect significantly modifies the earthquake behavior of Hyperbolic Cooling towers.

Analysis of the Working Characteristics of the Natural Draft Cooling Tower on the Laboratory Model

Analysis of the Working Characteristics of the Natural Draft Cooling Tower on the Laboratory Model

Analysis of the Controllability of the Natural Draft Cooling Tower

Analysis of the Controllability of the Natural Draft Cooling Tower

Numerical Study on Smoke Plume for Natural Draft Cooling Tower with Flue Gas Injection

The new exhaust mode of natural draft cooling towers (NDCT) with flue gas injection is investigated. The three-dimensional model for NDCT with flue gas injection and the boundary conditions are established via the Gambit 2.3. The cross-section of drift eliminator is set the velocity entrance for thermo-hygro air (velocity-inlet). The flue entrance is set admission velocity (velocity-inlet), the exit of NDCT with flue gas injection is set free gas export (outflow), and the emission of net flue gas to the cooling tower is a source of buoyant jets. The N-S equations are solved with the standard k- turbulence model by the Fluent 6.3. The improved NDCT with flue gas injection avoids air disturbance low-pressure zone compared with the conventional NDCT with flue gas injection. The corrosion of NDCT with flue gas injection in throat is reduced because net flue gas is wrapped in thermo-hygro air. Temperature gradient of net flue gas was distinct, the high-temperature zone is concentrated, and the uplifting performance is improved.

An empirical study on environmental impact of natural draft cooling tower with flue gas injection

AbstractIn order to understand the influences of natural draft cooling tower (NDCT) with flue gas injection on pollutant concentrations of the theoretical plume downwash area, an automatic air quality monitoring station was set in the theoretical plume downwash area of NDCT in Qinling power plant to get hourly SO2 and NO2 concentrations over a year. The results show that: 100% 1h average concentrations of SO2 and 99.64% NO2 observations satisfied the requirements of Chinese ambient air quality standard. High pollutant concentrations caused by plume downwash of NDCT with flue gas injection are not observed during the monitoring period, and there are no significant differences (P > 0.05) between pollutant concentrations in the theoretical plume downwash area under the prevailing westerly wind conditions (37.2 ± 24.8 μg/m3) and easterly wind conditions (36.9 ± 22.3 μg/m3), while the concentrations under conditions of west wind speed > 5m/s are significantly lower (P < 0.01) than those under conditions of wes...

Development of Modified Incompressible Ideal Gas Model for Natural Draft Cooling Tower Flow Simulation

The article deals with the development of incompressible ideal gas like model, which can be used as a part of mathematical model describing natural draft wet-cooling tower flow, heat and mass transfer. It is shown, based on the results of a complex mathematical model of natural draft wet-cooling tower flow, that behaviour of pressure, temperature and density is very similar to the case of hydrostatics of moist air, where heat and mass transfer in the fill zone must be taken into account. The behaviour inside the cooling tower is documented using density, pressure and temperature distributions. The proposed equation for the density is based on the same idea like the incompressible ideal gas model, which is only dependent on temperature, specific humidity and in this case on elevation. It is shown that normalized density difference of the density based on proposed model and density based on the nonsimplified model is in the order of 10-4. The classical incompressible ideal gas model, Boussinesq model and generalised Boussinesq model are also tested. These models show deviation in percentages.

Factors Analysis for the Performance of Natural Draft Cooling Tower Based on Enthalpy Difference Method

Factors Analysis for the Performance of Natural Draft Cooling Tower Based on Enthalpy Difference Method

Investigation of Natural Draft Cooling Tower in China

ABSTRACTThe natural draft cooling tower has been widely used in thermal power plants because of its stable operation, lower maintenance cost, and smaller environmental impact. Hundreds of natural draft cooling towers have been built in China, including different types and various capacities of conventional cooling towers, seawater cooling towers, flue gas injection cooling towers, cooling towers with water collecting device, dry cooling towers, and others. A wide range of investigation for natural draft cooling towers was carried out for the first time by the Electric Power Planning & Engineering Institute in 2013 in China. Based on the collected data and summarized information, the statistical results and conclusive opinions are analyzed. The development trend of natural draft cooling tower technology is also explored in this paper. The investigation results are expected to be a reference for designing and operating natural draft cooling towers in thermal power plants.

Numerical Study on the Performance of a Natural Draft Cooling Tower With Water-Cooled Collectors

ABSTRACTThe natural draft cooling tower with water-cooled collectors has advantages including pump lift saving, being a type of energy-saving tower, and being suitable for application in huge capacity nuclear power plants. The height of the rain zone is reduced due to the existence of water-cooled collectors under the fill, which leads to a change of the tower's performance. In this paper, a three-dimensional mathematical model of the thermal and aerodynamic field of the tower is established. The thermal and resistance characteristics of the tower have been studied by a numerical simulation method. The study results include: (1) Owing to the existence of water-cooled collectors, the resistance of the rain zone is decreased and the total resistance of the tower is also decreased; (2) as the height of the rain zone for the natural draft cooling tower with water-cooled collectors is lower, the air velocity distribution in the fill section is more uniform than that of the natural draft cooling tower; and (3) the cooling efficiency of the tower with water-cooled collectors is superior to that of the natural draft cooling tower.

Effect of Inlet Window Deflectors on the Performance of a Natural-Draft Cooling Tower Subjected to Crosswinds

The effect of inlet window deflectors on the performance of a natural draft cooling tower subjected to a crosswind was studied numerically. Three patterns of the inlet window deflectors with different setting angles (62, 72, and 82 degrees) were tested under various crosswind velocities. The assumption of heat and mass transfer equivalence was adopted for simulation. A numerical model was developed and verified by comparison with experimental data. The simulations show that the 72-degree inlet window deflectors are efficient in a wide range of crosswind velocities. The effect of the number of deflectors was also investigated and the link between the velocity profile and the critical wind velocity was clarified. It was shown that the use of deflectors in the inlet window increases the thermal efficiency of a cooling tower up to 8.6% at wind velocities greater than 2 m/s and does not exhibit any effect at the wind velocities close to critical wind velocity. The investigation may be helpful in optimal design of natural draft and “hybrid” cooling towers.

Water spray for pre-cooling of inlet air for Natural Draft Dry Cooling Towers – Experimental study

This paper deals with an experimental investigation of inlet air pre-cooling with water sprays aimed to enhance the performance of Natural Draft Dry Cooling Towers during high ambient temperature periods. An open-circuit wind tunnel with a test section of 1 × 1 m2 cross section and length of 5.2 m was employed to represent an inlet flow area section in a Natural Draft Cooling Tower. Experimental measurements of droplet evaporation and air cooling are presented. Nine high pressure, hollow cone nozzles were tested at various droplet sizes, air velocities (1, 2, 3 m/s), and injection rates under different ambient conditions. The water spray was characterized using a Phase Doppler Particle Analyser (PDPA). The effects of drop size distribution and air velocity on droplet evaporation, cooling effectiveness, and coverage area were investigated. The data shows clear trends of cooling enhancement with low air velocity or small droplet size distribution. It was found that the spray cooling efficiency, to a large extent, is dependent on spray coverage area. The experimental findings will benefit optimizing spray cooling performance in Natural Draft Dry Cooling Towers and nozzle arrangement.

Influence of Flow Rotation Within a Cooling Tower on the Aerodynamic Interaction with Crosswind Flow

Environmental crosswind changes the aerodynamic pattern inside a cooling tower, destroys uniform and axisymmetric distribution of flow at its inlet and outlet, and may degrade fill zone performance. In this paper, the effect of flow rotation in the over-shower zone of a natural draft cooling tower (NDCT) on the aerodynamic interaction with crosswind is studied numerically. The 3D geometry of an actual NDCT and three models of induced rotation velocity fields are utilized for simulation. It is demonstrated that flow rotation results in homogenization of the aerodynamic field in the over-shower zone. The inhomogeneity of the velocity field in the outlet cross section decreases linearly with rotation intensification. The effect of main stream switching under strong wind conditions is found. It is shown that even moderate flow rotation eliminates this effect.

Construction Simulation and Construction Speed Analysis of Natural Draft Cooling Towers

Using the finite element code ABAQUS and taking account of the wind load reduction, this paper presents a set of construction simulation methods of concrete cooling towers. A natural draft cooling tower at Taishan nuclear power station in Guangdong province, China, under three speeds of construction is simulated. Displacement and stress distributions of the cooling tower in the different construction stages are obtained. Some interested parts of the cooling tower are analyzed in detail and the variations of displacements and stresses of these parts with the construction are concluded. A comparative study of the influence of construction speed on displacements and stresses is performed as well. The analyses and proposals of this paper may be used as reference to the cooling tower design and construction.

Finite Element Analysis of Glass Fiber Reinforced Plastic Hyperbolic Natural Draft Cooling Tower

Applicating the finite element analysis software Ansys to do finite element analysis of a glass fiber reinforced plastic hyperbolic natural draft cooling tower .Under the working condition of gravity and wind load, to contrast the two models of the presence or absence of abdominal rod displacement, stress and unit axial force, and check the stability of compressive bar, and structural optimization. Analysis results can provide reference for the structural design of hyperbolic cooling tower.

Performance Analysis of the Natural Draft Cooling Tower in Different Seasons

Cooling towers are the biggest heat and mass transfer devices that are in widespread use. In this paper we use a natural draft counter flow cooling tower in investigating the performance of cooling tower in different seasons. The humidity is defined as water particles present in air. The humidity is the major factor in the atmosphere, it depends upon ambient temperature. Humidity is high in winter season and low in summer season. The performance of the natural draft cooling tower is dominated by wind speed, ambient air temperatures and humidity in the atmospheric conditions. When the humidity is high in atmosphere, large quantity of water is required for cooling condensate. When humidity is low in atmosphere, small quantity of water is required for cooling condensate. The value of relative humidity in the atmosphere varies from place to place and season. The different losses in the cooling tower such as drift losses, evaporation losses and blow down losses can be calculated. The maintenance of cooling tower in the form of removal of scale or corrosion plays important role in the performance of the tower. The performance of the natural draft cooling tower of 500 MW is evaluated.

The Influence of Airflow Inlet Region Modifications on the Local Efficiency of Natural Draft Cooling Tower Operation

We present the influence of the cooling tower airflow inlet region modifications at the Sostanj 4 thermal power plant on cooling tower local efficiency. Local efficiency change was estimated based on temperature fields of drift eliminators before and after the reconstruction of the cooling tower. Temperature fields were measured with thermal vision method. The local reduction of cooling tower efficiency was analyzed based on phenomenological relations of heat transfer obtained from the selected vertical segment of the cooling tower. The characteristic influence that the reconstruction had on the temperature field was detected on the circumference of the cooling tower. The efficiency reduction was the highest on the periphery of the cooling tower and in particular section it peaked at 2%, while in most part of the area it was below 0.5%. The presented measurement and analysis method enables the estimation of changes in the local efficiency of heat transfer in cooling towers.

CFD Two-Scale Model of a Wet Natural Draft Cooling Tower

A 2-D axisymmetric model of multiphase heat, mass, and momentum transfer phenomena in natural draft cooling tower is developed using a CFD code Fluent. The fill of the tower is modeled as a porous medium. The energy and mass sources in this zone are evaluated solving a separate 1-D model of mass and heat exchange. The spatial dependence of the sources is accounted for by dividing the fill into a set of vertical channels. The CFD solver produces boundary conditions for each channel, while the model of the channel exports the heat and mass sources to the CFD solver. To accelerate the calculations, an original technique known as the proper orthogonal decomposition (POD) is applied. This approach produces a reduced dimensionality model resulting in significant time economy and accuracy loss lower than 2%. The Euler-Euler multiphase model is used in the rain zone. The simulation results have been validated against experimental data coming from field measurements of a large industrial installation.

Modeling of a Spray Assisted Natural Draft Cooling Tower

Cooling towers are one of the largest heat and mass transfer devices that are in common use. A novel type of cooling tower has been proposed in which air flow rate into the tower is drawn by ejector action of sprays instead of fans as is done in conventional mechanical forced or induced draft cooling towers. This novel design offers the potential of savingthe energy cost for driving the fan. The paper presents mathematical models for momentum transfer which is the driving force causing the entrainment of air. Also the heat transfer model for co-current flow of liquid and gas in the tower has been presented. The liquid to gas ratio tend to decrease as liquid rate increases. The ratio attained in the experimentallaboratory tower was 3.3, correspondingly the Momentum transfer efficiency for the tower was 60% and was the highest. Experiments for cooling water initially at 45 o C to final water temperature 27 o C showed that the cooling tower efficiency was 54% and number of transfer unit 0.8.