Cooling Tower Plume Research Articles

Application of a Cloud Model to Cooling Tower Plumes and Clouds

Abstract A steady-state, one-dimensional cloud model has been modified to simulate the growth of plumes (both wet and dry) and clouds from natural and forced draft cooling towers. The modifications to the cloud model are discussed and comparisons are made between predicted height and length of plumes and observed values. A correlation coefficient of 0.78 is achieved for model predictions of plume height and a correlation coefficient of 0.49 for predicted plume length. Comparisons with Benning Road data showed 78% of the model-predicted plume heights were within 50% of the observed height, while 93% of the predicted plume lengths were within 50&percnt of the observed length. Analysis of the model predicted plumes for a year's morning and evening atmospheric soundings is presented. Comparison of plumes during winter and summer showed dramatic changes, with the longest plumes occurring during the winter. Summer plumes were much shorter with relatively small visible plume heights and tall dry extensions above...

An application of a plume rise model for multiple sources to the cooling tower plumes of john E. Amos Power Plant

A model of plume rise from multiple sources of unlike heights and emission parameters, developed by us, has been applied to a series of data regarding the wet plumes of the cooling towers of Amos Power Plant (Ohio, USA). A modification of the buoyancy parameter, in order to take into account the effects of latent heats on the buoyancy flux, has been made. This was done in two ways: by using virtual or equivalent temperatures. The comparison between data and model shows good agreement, giving a better fitting with the buoyancy calculated by means of equivalent temperatures.

Effects of industrial effluents on local cloudiness and rainfall

Industrial effluents alter both the microphysical properties that regulate the rate of production of precipitation and the location and strengths of density and velocity perturbations that regulate the dynamical development of clouds. Therefore, physical mechanisms exist through which industrial activities can modify local weather elements such as cloudiness and rainfall. Snow falling from large cooling tower plumes and the cloudiness spawned by heat rejection are the most obvious manifestations of this control. The extent to which industrial effluents exert control over local weather and climate remains controversial and difficult to quantify. As industrial activity becomes more concentrated, anomalous weather effects could become a problem that will require consideration when planning new facilities. This is particularly true for processes that modify the dynamical properties of the atmosphere by rejecting heat directly to the atmosphere.

Potential Weather Modification Caused by Waste Heat Release from Large Dry Cooling Towers

A numerical model of a cooling tower plume is employed to study the possible atmospheric effects of thermal plumes from natural draft dry cooling towers. Calculations are performed for both single and multiple towers, each of which can dissipate the waste heat from a nominal 1000 MWe power generating unit, and the results are compared with those for wet cooling towers associated with plants of the same generating capacity. Dry cooling tower plumes are found to have a higher potential for inducing convective clouds than wet cooling tower plumes, under most summertime meteorological conditions. This is due to the fact that both the sensible heat and momentum fluxes from a dry tower in summer are approximately one order of magnitude larger than those from a wet cooling tower.

Observations of Vortices in Cooling Tower Plumes

Time-lapse photography was used to estimate the speed of vortices in condensed plumes from a bank of mechanical draft cooling towers and a hyperbolic natural draft cooling tower. At a distance of about 30 m downwind from the towers, the median tangential velocity of the vortices at the edge of the plume is about 2 m s−1 in the downward direction, for ambient wind speeds of 7 to 13 m s−1. The standard deviation of turbulent fluctuations of tangential speeds of the vortices is about 1.8 m s−1 for both types of towers.

A study of production and growth of sulfate particles in plumes from a coal-fired power plant

A number of airborne plume sampling experiments designed to examine the importance of sulfate particle-generating chemical reactions within coal-burning power station plumes are described. The flights were conducted downwind of the Keystone Generating Station in western Pennsylvania, with The Penn State University research aircraft, an Aerocommander 680E. On-board aerosol sampling instrumentation included a condensation nucleus counter, an optical particle counter and an electrical aerosol analyzer. A casella cascade impactor containing electron microscope copper grids coated with carbon film was used to collect particles at varying distances from the stacks. These samples were analyzed for sulfate content and particle size distribution. Measurements of SO 2 were made with a rapid-response pulsed fluorescent analyzer. Atmospheric pressure, temperature, dewpoint, winds and aircraft position were also monitored. For each flight, a vertical spiral aircraft sounding was made upwind of the power station to determine atmospheric stability and background aerosol particle and SO 2 concentrations. Downwind, the flight pattern consisted of a series of cross wind and longitudinal plume penetrations out to distances at which SO 2 reached background levels. During the case in which cooling tower plume and stack plume merger occurred, sampling continued out to regions where the liquid plume had dissipated. It was found that when relative humidity was low, stability near-neutral and solar radiation intense, the production of new Aitken particles was the primary mechanism of SO 2 oxidation. In the case of merger between the stack plume and the cooling tower plume, the formation of sulfate on pre-existing particles predominated over the formation of new particles. During cases with intermediate meteorological conditions both processes were of equal importance.

An observation of cooling tower plume effects on total solar radiation

Measurements of total solar radiation were made on 7 March 1977. The sky was cloudless but a cooling tower plume occasionally came between the sun and the pyranometer that was used. These measurements resulted in values that were greater than those expected with a cloudless sky. It is likely that reflections from the plume, whose average position was slightly north of an imaginary sun-pyranometer line, were responsible.

An observation of cooling tower plume effects on total solar radiation

The effects of clouds (amount, type and height) on the surface UV-B radiation have been investigated at Qena, Egypt (26°17′, 32°10′, 96 m asl) using 2 years data (2004–2005) carried out by South Valley University (SVU)-meteorological research station. Thus, the characteristics of cloud's statistical property during the study period were employed to evaluate the general feature of the region of this study. However, ≈86% of all the observations were ⩽2 octas and the overcast conditions (8 octas) were very rarely over the study region (only 0.2% of all cases). These observations included 10% low-level clouds, 3.16% mid-level clouds and 7.59% high-level clouds. The dominated types of these clouds are stratocumulus (8.9%) and cirrus (5.8%).The hourly values of cloudless sky UV-B radiation (UV-B0) and consequently the cloud modification factor (CMF) were estimated. An empirical model was developed for CMF as a function of the amount of cloud at low- and mid-level and high-level clouds. The correlation coefficients were equal to 0.985 and 0.987, respectively. In addition, a general expression of the CMF for situations those are considered as the effect of different clouds was found. The efficiency of this model has been tested in combination with a cloudless sky empirical model using independent data set. For this purpose, the hourly values of UV-B at selected cloudless and cloudy days were estimated. A good agreement was observed between the measured and the predicted values of our model. The mean value of the correlation coefficients of these selected days was 0.98.In addition, the attenuation of UV-B radiation could be determined by considering low- and mid-level and high-level clouds. The reduction of UV-B radiation as a function of cloud amount was non-linear for the both cases. At cloud amount of 100%, UV-B radiation was reduced by 83% on average by the high-level clouds.

A mathematical model of drift deposition from a bifurcated cooling tower plume

Cooling tower drift deposition modeling has been extended by including the centrifugal force induced by plume bifurcation as a mechanism for droplet removal from the plume. The model is capable of predicting the trajectory of a single droplet from the stage of strong interaction with the vortex field soon after droplet emission at the tower top through the stage of droplet evaporation after breakaway from the plume. Applications showed the droplet to follow a helical trajectory within the plume, with breakaway and ground impact depending upon plume rise, ambient wind, evaporation and vortex strength.

Observations and predictions of natural draft cooling tower plumes at paradise steam plant

Observations of the time-mean plumes from the natural-draft cooling towers at the Tennessee Valley Authority's Paradise Steam Plant taken during the winter of 1973 are compared with a one-dimensional model for moist plume behaviour. A bent-over plume model based on the closed form solution to the integral form of the governing equations for plume behaviour for an atmosphere of linear stable stratification was found to adequately describe most of the observed plume trajectories and visible lengths. However, numerical integration of the equations are required to account for detailed effects of vertical wind shear and elevated inversions on plume trajectory. Plume trajectory and visible length are greatly influenced by tower downwash.

Predicted Climatology of Cooling Tower Plumes from Energy Centers

A one-dimensional plume and cloud growth model is applied to four months of radiosonde observations from Nashville, using as initial conditions the plume from single large cooling towers with waste heat outputs of 103, 104 and 105 MW, and a complex of cooling towers with a total waste heat output of 105 MW. Estimates of average annual plume rise from the four energy sources are 580,1180,2460 and 780 m, respectively. The predicted plume rise, visible plume length and cloud formation are given as functions of time of day, year and weather type. For example, a cloud forms at the top of the plume from the 103 MW tower in 65% of the morning soundings during which ground level fog was observed. A cloud is predicted to occur 95% of the time at the top of the plume from the single 105 MW tower. It is found that if the towers in an energy center are separated by a distance greater than the average plume rise from one tower, then plume merging is minimized. Observations from TVA's Paradise steam plant are used to test the predictions of visible plume length from a single 103 MW tower.

EPA’s Cooling Tower Plume Research

A comprehensive review is made of EPA's cooling tower plume research program with particular attention to plume modeling. The research began in 1969 with a modest effort to define the problem and continued through a multidisciplinary research project at a site where a single-cell salt-water cooling tower was installed to assess its impact on the local terrestrial ecosystem. The evolutionary process involving the analytical developments and advanced instrumentation techniques required for such an undertaking is examined. Plans for continued efforts are presented.

Airborne measurement of drop size distributions for drops larger than 60 μm

An airborne instrument able to collect selectively and replicate large drops (diameter greater than 60 μm) is described. The large drops reach the collector by their inertia, while the small ones moving along with the air are not collected even though their number concentration may be more than 1000 times larger than the large drops. This instrument, which can be mounted on a light aircraft, can be used either to determine the concentration of the drift drops in cooling tower plumes or precipitation elements in clouds. Data are included from flights through cooling tower plumes.

Potential weather modification from cooling tower effluents at conceptual power parks

A numerical model for multiple plumes is developed to study the enhanced convection of merged plumes from a cluster of cooling towers at a conceptual power park. The model is based on the equations of motion for a quasi incompressible fluid derived from the laws governing the change of momentum, the first law of thermodynamics, and the conservation of mass. The microphysical processes are simplified in the model by a parameterization approach similar to the work of Kessler (1969) with the assumption that the droplet size distributions in the cooling tower plume are the same as those of cooling tower drift measured near the top of cooling towers. The numerical model is employed to simulate the merged plume convection from clusters of (up to 40) natural draft cooling towers, where each tower serves to dissipate 2400 MW of waste heat. It was found that the plume rise from 40 towers is predicted to be approximately 360% and 130% of that from a single tower for an average July afternoon and average January morning sounding, respectively, taken in the Louisiana area if the towers are arranged in a near square grid and spaced at 300 m apart. However, it is not uncommon to predict an induced convective cloud developing over 4000 m in height from more than 5 towers in a group for an individual afternoon sounding in the southeastern United States. Comparison of the predicted precipitation using Kessler's microphysical parameterization with Marshall and Palmer's (1948) drop size distribution and the similar approach with available observed droplet size distribution from cooling tower drift is also made. The model predictions are in good agreement with observations at existing power plants up to 3000 MWe generating capacity.

Maximum Rise of Cooling Tower Plumes

Abstract The application of the maximum plume rise formula for bent-over industrial plumes to visible cooling tower plumes depends on the validity of two assumptions: the neglect of finite source size and the neglect of condensation effects. These produce errors which, in many cases, tend to compensate. The effect of finite source size is examined analytically and an alternative formula for maximum plume rise is derived.

Snowfall Observations from Natural-Draft Cooling Tower Plumes

During the winter of 1975-1976, snowfall from the plumes of large natural-draft cooling towers of power plants has been observed. Snow accumulations up to 2.5 centimeters have been found on the ground at extended distances from the cooling towers, and visibility has been restricted to less than 1600 meters in the tower plume near ground level.

Cooling Towers and the Environment

Measurements of natural draft cooling tower plume behavior, as well as meteorological variables, were obtained from aircraft flights near major power plants of the American Electric Power System. Persistence of the visible plume to great distances depends essentially on ambient humidity. Atmospheric stability at plume elevation was also important. Cooling tower-induced fog at ground-level was never observed in any of the tests, and aerodynamic downwash of the visible plume was absent also. The cooling towers did cause modification of natural clouds and they occasionally shadowed some local areas from the sun. Merging of the stack and cooling tower plumes was a common occurrence.

Predicted and observed cooling tower plume rise and visible plume length at the John E. Amos power plant

A one-dimensional numerical cloud growth model and several empirical models for plume rise and cloud growth are compared with twenty seven sets of observations of cooling tower plumes from the 2900 MW John E. Amos power plant in West Virginia. The three natural draft cooling towers are 200m apart. In a cross wind, the plumes begin to merge at a distance of about 500m downwind. In calm conditions, with reduced entrainment, the plumes often do not merge until heights of 1000m. The average plume rise, 750m, is predicted well by the models, but day-to-day variations are simulated with a correlation coefficient of about 0.5. Model predictions of visible plume length agree, on the average, with observations for visible plumes of short to moderate length (less than about 1 km). The prediction of longer plumes is hampered by our lack of knowledge of plume spreading after the plumes level off. Cloud water concentrations predicted by the numerical model agree with those measured in natural cumulus clouds (about 0.1–1 g kg −1).

The observed rise of visible plumes from hyperbolic natural draft cooling towers

The behavior of natural draft cooling tower plumes and related meteorological variables have been measured from aircraft near three major plants of the American Electric Power System. The rise of those plumes which persisted long enough to reach a stabilized height depended primarily upon the height of the capping inversion aloft. All such plumes rose to elevations of 425 m or more above grade. No significant relationships between plume rise and wind speed, plant load, or ambient temperature were found. We conclude that simple temperature-humidity soundings in the vicinity of the towers would serve as effective predictors of plume rise and persistence.

The effect of atmospheric conditions on the length of visible cooling tower plumes

The governing equations for the initial phase of cooling tower plume behaviour are solved numerically to illustrate the quantitative effects of atmospheric temperature, moisture content, stability and moisture gradient on visible plume lengths. Some discussion of the atmospheric turbulence dominated phase of plume behaviour is given. Decreasing relative humidity with height and/or stable conditions in the atmosphere are found to lead to decreased plume lengths. The effects are most pronounced at low temperatures and high atmospheric relative humidities. The influence of the entrainment parameter on visible plume length is examined and found to be relatively minor when compared to the influence of atmospheric conditions. The numerical results are compared with a simple graphical solution and the results show considerable disparity.