Numerical modeling and experimental measurements of water spray impact and transport over a cylinder

Yoon, Sam S.; DesJardin, Paul E.; Presser, Cary; Hewson, John C.; Avedisian, C. Thomas

doi:10.1016/j.ijmultiphaseflow.2005.05.007

Cited by 36 publications

(22 citation statements)

References 44 publications

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“…In their case, the spray injection velocity was not high enough to result in the 'shattering' regime. The characteristic impingement parameter was K¡57:7 that only the droplet 'rebounding' and 'sticking' occurred in the case of Yoon et al [38] while our investigation is focused on the shattering regime whose range is 0¡K¡300 for U inj = 20 m=s and 0¡K¡600 for U inj = 40 m=s.…”

Section: Modelling Spray Impingement Over a At Surfacementioning

confidence: 94%

“…Each simulation is conducted by running an unsteady RANS simulation and collecting ensemble statistics after an initial time of t = 0:5 s when the ow attained a statistical stationary state. Statistics are collected from t = 0:5 to 2.0 s at the intervals of 0.0002 s; thus, 7500 statistic collection frequency is applied during 1.5 s. The average droplet Reynolds, and Weber number for the given operating conditions are Re = U inj D 10 = = 1594, Re = 3189 and We = U Figure 10 is obtained from Reference [38]. In their case, the spray injection velocity was not high enough to result in the 'shattering' regime.…”

Section: Modelling Spray Impingement Over a At Surfacementioning

confidence: 99%

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Modelling spray impingement using linear stability theories for droplet shattering

Yoon

DesJardin

2005

Int. J. Numer. Meth. Fluids

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SUMMARYThis paper compares several linear-theory-based models for droplet shattering employed for simulations of spray impingement on at wall surface or a circular cylinder. Numerical simulations are conducted using a stochastic separated ow (SSF) technique that includes sub-models for droplet dynamics and impact. Results for spray impingement over a at wall indicate that the linear theory applicable for a single droplet impact over-predicts the number of satellite (or secondary) droplets upon shattering when compared to experimental data. The causes for the observed discrepancies are discussed. Numerical simulation results for spray impingement over a circular cylinder in cross ow are obtained and discussed.

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Section: Modelling Spray Impingement Over a At Surfacementioning

confidence: 94%

Section: Modelling Spray Impingement Over a At Surfacementioning

confidence: 99%

Modelling spray impingement using linear stability theories for droplet shattering

Yoon

DesJardin

2005

Int. J. Numer. Meth. Fluids

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“…PDPA is a well-established laser based nonintrusive measurement technique with the capability of measuring both size and three components of droplet velocity at high accuracy directly and simultaneously. PDPA provide information about the number, size and velocity classes of the spray as it measures one droplet at a time [109]. In this experiment, two-dimensional PDPA was used for drop size, velocity measurements, whereas high speed photography system was used for cone angle and breakup length measurements.…”

Section: Apparatus For Spray Characterisationmentioning

confidence: 99%

“…However, Yoon et al [109] reported that the uncertainties in the PDPA measurement of droplet size and droplet velocity were estimated at 10-15%.…”

Section: Pdpa Setupmentioning

confidence: 99%

“…Some studies used a single virtual injection back at the nozzle location. The initial spray characteristics were adjusted manually to match the predicted spray characteristics at the breakup length with measurements [44,109,120,121]. A further approach was to inject droplet at a distance where droplets become more uniform across the spray plume and move at the same speed [113].…”

Section: Nozzle Representationmentioning

confidence: 99%

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Modelling and experimental study of spray cooling systems for inlet air pre-cooling in natural draft dry cooling towers

Alkhedhair¹

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Geothermal energy is a promising renewable energy to be used for baseload electricity. Most potential sites with high geothermal temperature are mostly located in remote areas where water is limited. This is besides water scarcity and environmental protection, which made dry cooling systems a better alternative solution for heat rejection of power plants. Furthermore, natural draft cooling towers have the advantage of avoiding parasitic losses introduced by the fans at mechanical draft cooling towers. However, power plants utilizing dry cooling technologies experience a significant reduction in power generation during high ambient temperature periods. This reduction often goes along with the peak power demand which results in a great loss for the power plant owners. In certain instances, dry cooling tower performance can be enhanced during these periods by pre cooling of the inlet air by spraying atomized water into the inlet air.The present study introduces the use of spray cooling for inlet air pre-cooling in natural draft cooling towers. Spray cooling is investigated in this study due to its simplicity, low capital cost, ease of operation and maintenance, and capability of increasing power plant efficiency while consuming only a small amount of water compared to wet cooling towers or other evaporative cooling methods. Although spray cooling has found successful applications in process coolers and gas turbine inlet air cooling, the large scale applications in power industry have been limited.Several issues limit the application in power industry. The main one is the incomplete evaporation of water droplets which can cause corrosion and scaling of heat exchanger surface. Incomplete evaporation also increases operational cost due to water consumption. To the best of our knowledge, a detailed investigation of the spray cooling performance in natural draft dry cooling towers operating environment has not yet been performed. The aim of the current work is to optimise a spray cooling system for inlet air pre-cooling in natural draft dry cooling towers.In the present study, an Eulerian-Lagrangian 3-D numerical model was developed which is capable of simulating evaporating water sprays produced by real nozzles. In order to reproduce real nozzle characteristics in the simulation, a new adaptable method for hollow-cone spray representation in Eulerian-Lagrangian numerical models was developed. This allows real nozzles characterised during experiments to be included in the simulation, thereby correctly accounting for radial evolution of droplet size distribution and air/droplets momentum exchange. The CFD model was applied to calculate local droplet transport and evaporation, and spray cooling efficiency at different operating conditions for spray cooling systems optimisation under typical Natural Draft Dry Cooling Tower conditions.iii Experimental measurements from a wind tunnel test rig simulating Natural Draft Dry Cooling Tower inlet flow conditions have been performed in order to investigate droplet transport...

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Simulating spray droplet impaction outcomes: comparison with experimental data

Zabkiewicz

Pethiyagoda

Forster

et al. 2020

Pest Management Science

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BACKGROUND A suite of plant retention spray models has been developed to simulate spray retention using virtual surfaces (either single leaves or whole plants) and their outputs compared with experimental data for the equivalent spray scenarios. RESULTS The results for a single formulation (0.1% v/v lecithin mixture in water) and difficult to wet plant species Chenopodium album L (common lambsquarters) are presented. They include experimental observations with single leaves, as well as simulations of virtual impaction events, conducted to provide for the first time estimates of f (the proportion of theoretical impact drop diameter at shatter). With this factor prescribed, multi‐plant simulations using a range of nozzle types and droplet sizes (volume mean diameter (VMD) range 241 to 530 μm) are compared with equivalent experimentally determined spray retention by real plants. The simulations demonstrated that impaction resulted predominantly in shatter with the production of daughter droplets, and that retention is mainly due to re‐capture of these droplets. Overall the simulations show the same trends as experimental retention results from different nozzle applications, but at best predicted retention results were 68% to 79% of experimental percentage retention, depending on plant spacing. CONCLUSIONS Retention is the result of some primary drop capture but predominantly by recapture of shatter droplets as the modelling illustrates. The value of f affects the droplet shatter outcome and can result in fewer, more energetic daughter droplets, or more droplets but with lower energies. However, this effect alone cannot explain the discrepancy between actual and simulated results. Possible operational influences are discussed. © 2020 Society of Chemical Industry

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Numerical modeling and experimental measurements of water spray impact and transport over a cylinder

Cited by 36 publications

References 44 publications

Modelling spray impingement using linear stability theories for droplet shattering

Modelling spray impingement using linear stability theories for droplet shattering

Modelling and experimental study of spray cooling systems for inlet air pre-cooling in natural draft dry cooling towers

Simulating spray droplet impaction outcomes: comparison with experimental data

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