Cooling Tower Plume Research Articles

Multi-Modal Machine Learning to Predict the Energy Discharge Levels from a Multi-Cell Mechanical Draft Cooling Tower

An artificial neural network was developed to augment the accuracy of a physically based computer model in relating heat discharge to visible plume volume of a 12-cell mechanical draft cooling tower. In a previous study, Savannah River National Laboratory developed a 1D model to capture the average power plant discharge levels via analysis of a series of visual images but was unable to accurately predict individual cases, resulting in an overall average error of about 5%, but individual comparisons resulted in an R2 of 0.36. Three optimization algorithms were applied to better fit the entrainment coefficients, and the artificial neural network model was applied to 289 cases of a 12-cell mechanical draft cooling tower power generation facility. Two artificial neural networks configurations consisted of 10 and 47 nodes that used as input readily available plant data, observed cooling tower plume conditions, observed operational conditions, local and regional weather, and the predicted plume volume from the physical model; the individual predictions’ accuracy improved to R2>0.95. This article concludes the sensitivities for the 1D model and additional actions to progress this field of study as well as applications for cooling tower monitoring. This strategy demonstrated an encouraging first step towards using multi-modal artificial neural network machine learning technology for information fusion to estimate power levels from external observations.

Development and evaluation of a hybrid membrane condenser for water recovery from cooling tower plume

Cooling towers discharge a tremendous amount of water vapor from industries into the atmosphere. Recovering this water will increase efficiency, contribute to water security and industrial sustainability. Thus, suitable technology is needed. This study investigates the feasibility of a microporous hydrophobic propylene membrane to recover water from an artificial humid gas, representing water vapor from a cooling tower. Water was used as a cooling medium in the permeate side of the membrane module. Experimental results showed that water vapor condensed on the surface of the membrane on the feed and the permeate sides. Thus, the membrane module worked as a conventional membrane condenser (MCo) and a transport membrane condenser (TMC) simultaneously, resulting in high water recovery, reaching up to four times that of the TMC mode alone. Key factors influencing rate of condensation and water recovery, such as feed velocity and cooling water temperature, are thoroughly investigated. As feed velocity increased, the rate of condensation also increased, but the water recovery decreased. Lowering the cooling water temperature increased the rate of condensation as well as the water recovery. The results show a maximum water recovery of 75 % under optimal conditions, highlighting the novel and improved performance of the proposed configuration for water vapor recovery from cooling tower plumes compared to previous MCo studies.

Cooling Tower Plume and Drift Concentration in presence of Urban Canyon

This paper presents a computational analysis of the cooling tower plume and drift emitted by mechanical draught cooling towers situated in urban areas. The data from the Wang X (2019) and Briggs plume lift height formula are used to prove results obtained from computational Modeling of cooling tower drift and it was found to be effective. The simulation setup uses a multiphase mixture model for plume analysis and DPM for analysis of drift in the Ansys fluent. The CFD simulation results are accurate within 50 to 100 m with the Briggs plume lift height formula. The effect of wind coming from urban canyons on the cooling tower results in decreased plume lift height and increase drift concentration and deposition rate on the ground.

A hybrid cooling tower model for plume abatement and performance analysis

A one-dimensional model of a hybrid cooling tower and its atmospheric plume is presented with the aim of studying plume abatement, water consumption and cooling performance. To achieve this goal, a counter-flow wet cooling tower model is integrated with an effectiveness-NTU model for the dry cooling section, and, a turbulent plume model. To estimate fan power requirements, a draft equation is also included to predict the pressure drop and damper requirements in the dry and wet sections. The proposed model is used to study the effect of environmental and operating conditions on hybrid cooling tower plume visibility and cooling performance. In particular, and for the hybrid cooling tower examined in this study, a visible plume can be suppressed by approximately 10%–40% and 80%–90% hybridization, i.e., dry section to total air flow rate ratio, when the ambient air temperature is 5°C and −20°C, respectively. Results highlight the inherent trade-offs between cooling capacity, plume abatement, water consumption and fan power. Parametric studies identify the range of operating conditions for which satisfying outlet water temperature and plume abatement requirements may prove especially challenging.

CFD modelling of the condensation, evaporation, coagulation and crystallization processes in the cooling tower emissions

The aim of the paper is to develop the CFD model for the environmental impact assessment of the cooling tower. The methods applied for this problem are the single-phase turbulent multispecies flow modelling with the DPM Lagrangian particle tracking. The simulations have been carried out in the steady state SIMPLE solver using the ANSYS Fluent software. User Defined Functions have been defined to enhance the accuracy and versatility of the modelling approach in terms of turbulence, fog formation, evaporation, coagulation and crystallization modelling. The Chalk Point cooling tower experiment, laboratory tests with freezing droplets and analytical correlations are used to verify the customized parts of the new CFD model. The arbitrary small-town geometry is used to demonstrate the simulation capabilities of the fog and drift deposition as well as the temperature and relative humidity values near ground and buildings. The results indicate that the new CFD model is able to predict the cooling tower plume parameters, icing and salt contamination risks as well as drift deposition.

Membrane Condenser for Particulate Abatement from Waste-Gaseous Streams

Membrane Condenser (MC) is a novel membrane contactor operation recently investigated for the valorization of industrial waste gaseous streams. In particular, until now, it was applied for water recovery from flue gas, cooling tower plumes, etc. More recently, its effectiveness and flexibility in contaminants (such as, NH3 , HF, SO2 ) removal and control from waste gaseous streams was also proved. In the present work, the application of membrane condenser for water recovery as well as microparticles removal from gaseous streams are presented. Experimental tests showed that microparticles did not affect membrane condenser performance, neither in terms of water recovery nor in term of fouling. Moreover, the carried-out tests revealed also that the complete retention of particles can be achieved only through the proper choice of the membrane, with pore size lower than particles diameter.

On the reliability of CALPUFF and AUSTAL 2000 modeling systems regarding smoke and vapor plume mergence

Observations at power plants have shown that smoke plumes from stacks frequently merge with vapor plumes from cooling towers. Wind speed and direction play a key role in merging vapor and smoke plume. Mergence of stack and cooling tower plume leads to formation of undesirable substances such as sulfuric acid aerosols, acid mist, and acid fly ash. The present study shows that smoke and vapor plume mergence is a common phenomenon in Matra power plant in Hungary; however more studies must be conducted in the future to reveal the type and number of plume mergence in the mentioned plant. The present work also indicates that the CALPUFF and AUSTAL 2000 modeling systems cannot provide enough information with regard to vapor and smoke plume mergence.

Fog harvesting from cooling towers using metal mesh: Effects of aerodynamic, deposition, and drainage efficiencies

Fog harvesting is recognized as an important alternate source of fresh water. Industrial fog can supplement water for industrial requirement. Collection of fog (drift droplets) from cooling tower plumes is a viable mode of industrial fog harvesting. The present study delves deeper into the findings of our earlier pilot investigation, on cooling tower fog harvesting and unravels how the collection efficiency depends on interaction of the mesh with the oncoming flow and the deposited fog droplets. Herein, we quantify the fog collection and explain the rationale of the individual contributions of aerodynamic, deposition, and drainage efficiencies on the overall collection efficiency. The effect of the mesh orientations and the tangential velocity component of the cooling tower plume (arising out of the cooling tower-fan rotation) are considered. Aerodynamic efficiency of the mesh and pressure drop across is estimated through computational fluid dynamic analysis. Also, an analysis of the force interaction between the mesh wires, deposited droplet, and the fog stream is carried out to identify the salient deterring factors like re-entrainment, clogging, and premature dripping of collected water droplets, based on which the regime of collection is mapped. The best collection configuration is found at an inclination of 15° with the vertical, with an overall collection efficiency of about 16%. The best configuration would allow recovery of re-usable fresh water at a nominal energy penalty of ∼3.9 kWh/m3. Our results offer the design bases for developing full-scale fog harvesting setups for industrial cooling towers.

Recovery of water and contaminants from cooling tower plume

Recovery of water and contaminants from cooling tower plume

Cooling tower plume abatement using a coaxial plume structure

The traditional approach of cooling tower plume abatement is supposed to result in an unsaturated, well-mixed plume with a “top-hat” structure in the radial structure, but this is an idealization that is rarely achieved in practice. Meanwhile, previous analyses have shown that there may be an advantage in specifically separating the wet and dry air streams whereby the corresponding plume is of the coaxial variety with dry air enveloping (and thereby shielding) an inner core of wet air. Given that a detailed understanding of the evolution of coaxial plumes is presently lacking, we derive an analytical model of coaxial plumes in the atmosphere, which includes the effects of possible condensation. Of particular concern is to properly parameterize the entrainment (by turbulent engulfment) of fluid from the inner to the outer plume and vice versa. We also present and discuss the two different body force formulations that apply in describing the dynamics of the inner plume. Based on the resulting model predictions, we introduce a so-called resistance factor, which is defined as the ratio of the average non-dimensional velocity to the average relative humidity. In the context of visible plume abatement, the resistance factor so defined specifies the likelihood of fog formation and/or a recirculation of moist air into the plenum chamber. On the basis of this analysis, we can identify the region of the operating-environmental condition parameter space where a coaxial plume might offer advantages over its uniform counterpart.

THEORETICAL ANALYSIS OF A WET COOLING TOWER FOR FRESH WATER FROM PLUME AND ANALYZING AN INDUSTRIAL COOLING TOWER BASED ON RESULTS

A cooling tower is a heat rejection device which rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature. The stream of saturated exhaust air leaving the cooling tower called the plume is visible when water vapor it contains condenses in contact with cooler ambient air, like the saturated air in one's breath fogs on a cold day. Under certain conditions, the cooling tower plume may present fogging or icing hazards to its surroundings and gives some environmental problems. To find the solution for this problem a cooling tower has been analysed based on air flow rate through the tower and the cooling load to obtain fresh water yield by utilising plume from cooling tower top. The theoretical analysis gives the values of important parameters Theoretical analysis has been done on wet cooling tower by varying the water flow rate through which affect the performance of a cooling tower such as the cooling range, effectiveness, approach, fresh water yield etc. Then with the conditions of a trials from the analysis, the mass flow rate of water in the cooling tower was scaled up to match the mass flow rate of water in an industrial cooling tower. This helps in obtaining the mass flow rate of the air and fresh water yield through the industrial cooling tower.

Droplet ejection and sliding on a flapping film

Water recovery and subsequent reuse are required for human consumption as well as industrial, and agriculture applications. Moist air streams, such as cooling tower plumes and fog, represent opportunities for water harvesting. In this work, we investigate a flapping mechanism to increase droplet shedding on thin, hydrophobic films for two vibrational cases (e.g., ± 9 mm and 11 Hz; ± 2 mm and 100 Hz). Two main mechanisms removed water droplets from the flapping film: vibrational-induced coalescence/sliding and droplet ejection from the surface. Vibrations mobilized droplets on the flapping film, increasing the probability of coalescence with neighboring droplets leading to faster droplet growth. Droplet departure sizes of 1–2 mm were observed for flapping films, compared to 3–4 mm on stationary films, which solely relied on gravity for droplet removal. Additionally, flapping films exhibited lower percentage area coverage by water after a few seconds. The second removal mechanism, droplet ejection was analyzed with respect to surface wave formation and inertia. Smaller droplets (e.g., 1-mm diameter) were ejected at a higher frequency which is associated with a higher acceleration. Kinetic energy of the water was the largest contributor to energy required to flap the film, and low energy inputs (i.e., 3.3 W/m2) were possible. Additionally, self-flapping films could enable novel water collection and condensation with minimal energy input.

Cooling tower plume - model and experiment

The paper discusses the description of the simple model of the, so-called, steam plume, which in many cases forms during the operation of the evaporative cooling systems of the power plants, or large technological units. The model is based on semi-empirical equations that describe the behaviour of a mixture of two gases in case of the free jet stream. In the conclusion of the paper, a simple experiment is presented through which the results of the designed model shall be validated in the subsequent period.

Effect of Different Heat Rejection Scenarios on Cooling Tower Plume Dispersion

This impact of heat rejection on cooling tower plume dispersion was studied in this paper by applied SACTI (Seasonal Annual Cooling Tower Impact) model. In order to analyze the impact of heat rejection (HR), we set five scenarios including observed, HR decrease 5% (HR-5) and 10% (HR-10), and increase 5% (HR+5) and 10% (HR+10). Results showed that plume length frequency, plume height frequency and plume radius frequency will present different variation trend when heat rejection increase and decrease scenarios. On the whole, the plume character parameter will decrease as heat rejection decrease, but will increase as heat rejection increasing.

Impact of Relative Humidity on Cooling Tower Plume Dispersion

The SACTI model (Seasonal Annual Cooling Tower Impact) as the environmental impact assessment of cooling tower was applied in this paper, which was used to simulate the plume characters under different kinds of relative humidity. The three kinds of relative humidity were 70%, 80% and 90% and it was analyzed that the plume character under these three kinds of relative humidity. Results showed that the plume length, plume height and plume radius will present different change trend when relative humidity changed. Additionally, the plume dispersion character in different seasons presented obviously variations and the different wind direction also play important role in prediction of cooling tower plume dispersion.

Analysis of Environmental Impact Factors of Natural Draft Cooling Towers in Power Plant

Based on the requirements of Air Clean guidelines (VDI3784 and VDI3945) in German for cooling tower plume rise and dispersion model, a comparative analysis of atmospheric environmental impact of the cooling tower exhaust for different parameters. Parameters includes different source emission parameters and ambient humidity parameters. Then, analysis of the impact factors of plume rising height and the ground concentration according to the emission parameters. The results show that the most influential parameters are temperature and gas flow rate, relatively, the flue gas relative humidity and liquid water content has less influence in the rising height. Therefore, the increase of flue gas flow rate will significantly strengthen the dispersion of pollutants in the air. The flue gas humidity and liquid water have a certain influence on the dispersion of pollutants, but the effect is not so significant. The increase of flue gas humidity and liquid water content is not conducive to the dispersion of pollutants, therefore the surface concentration will only increase slightly.

The Effect of Wind Speed on Cooling Tower Plume Dispersion

Wind speed was an important impact factor when simulating the cooling tower plume dispersion. The SACTI model was selected in this paper and this model was used to predict the plume dispersion character discharging from cooling tower under normal operation and three different kinds of wind speeds. The three kinds of wind speeds were 2 m/s, 4 m/s and 6 m/s and it was analyzed that the plume character under these three wind speeds. Results showed that the plume length, plume height and plume radius will present different change trend when wind speed changed.

Response Analysis of Cooling Tower Plume Dispersion to the Release Height

The SACTI model (Seasonal Annual Cooling Tower Impact) as the environmental impact assessment of cooling tower was applied in this paper, which was used to simulate the plume characters under different cooling tower heights. The results showed that the plume length, plume height and plume radius presented noticeable differences with variances of different distances and wind directions under different cooling tower heights. The comparisons of differences of plume characters indicated that the relative change of plume length frequency displayed obvious decreased trend with increased distance when distance was greater than 500m, and that of plume height frequency appeared parabolic curve with increased distance. The relative change of plume radius frequency expressed totally descended trend.

Application of a semi-spectral cloud water parameterization to cooling tower plumes simulations

In order to simulate the plume produced by large natural draft cooling towers, a semi-spectral warm cloud parameterization has been implemented in an anelastic and non-hydrostatic 3D micro-scale meteorological code. The model results are compared to observations from a detailed field experiment carried out in 1980 at Bugey (location of an electrical nuclear power plant in the Rhône valley in East Central France) including airborne dynamical and microphysical measurements. Although we observe a slight overestimation of the liquid-water content, the results are satisfactory for all the 15 different cases simulated, which include different meteorological conditions ranging from low wind speed and convective conditions in clear sky to high wind and very cloudy. Such parameterization, which includes semi-spectral determination for droplet spectra, seems to be promising to describe plume interaction with atmosphere especially for aerosols and cloud droplets.

Integral Model for Turbulent Buoyant Jets in Unbounded Stratified Flows Part 2: Plane Jet Dynamics Resulting from Multiport Diffuser Jets

An integral model for the plane buoyant jet dynamics resulting from the interaction of multiple buoyant jet effluxes spaced along a diffuser line is considered as an extension of the round jet formulation that was proposed in Part I. The receiving fluid is given by an unbounded ambient environment with uniform density or stable density stratification and under stagnant or steady sheared current conditions. Applications for this situation are primarily for submerged multiport diffusers for discharges of liquid effluents into ambient water bodies, but also for multiple cooling tower plumes and building air-conditioning. The CorJet model formulation describes the conservation of mass, momentum, buoyancy and scalar quantities in the turbulent jet flow in the plane jet geometry. It employs an entrainment closure approach that distinguishes between the separate contributions of transverse shear and of internal instability mechanisms, and contains a quadratic law turbulent pressure force mechanism. But the model formulation also includes several significant three-dimensional effects that distinguish actual diffuser installations in the water environment. These relate to local merging processes from the individual multiple jets, to overall finite length effects affecting the plume geometry, and to bottom proximity effects given by a “leakage factor” that measures the combined affect of port height and spacing in allowing the ambient flow to pass through the diffuser line in order to provide sufficient entrainment flow for the mixing downstream from the diffuser. The model is validated in several stages: First, comparison with experimental data for the asymptotic, self-similar stages of plane buoyant jet flows, i.e. the plane pure jet, the pure plume, the pure wake, the advected line puff, and the advected line thermal, support the choice of the turbulent closure coefficients contained in the entrainment formulation. Second, comparison with data for many types of non-equilibrium flows with a plane geometry support the proposed functional form of the entrainment relationship, and also the role of the pressure force in the jet deflection dynamics. Third, the observed behavior of the merging process from different types of multiport diffuser discharges in both stagnant and flowing ambient conditions and with stratification appears well predicted with the CorJet formulation. Fourth, a number of spatial limits of applicability, relating to terminal layer formation in stratification or transition to passive diffusion in a turbulent ambient shear flow, have been proposed. In sum, the CorJet integral model appears to provide a mechanistically sound, accurate and reliable representation of complex buoyant jet mixing processes, provided the condition of an unbounded receiving fluid is satisfied.