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Andrew  L.  Banka,  P.E.  Airflow  Sciences  Corpora1on  abanka@airflowsciences.com  D.  Sco4  MacKenzie,  PhD,  FASM  Houghton  Interna1onal,  Inc  smackenzie@houghtonintl.com  

Parameters  Effec?ng  Submerged  Plumes  in  Quench  Systems  

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Agenda  

•  Introduc1on  ▲ Background  ▲ Overview  

•  Simula1on  Study  ▲  System  Descrip1on  ▲ CFD  Model  

•  Results  •  Discussion  •  Conclusions  

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Introduc1on  -­‐  Background  

•  Agita1on  is  cri1cal  ▲ Purpose  is  uniform  heat  transfer  

▲  Low  distor1on  ▲ Reduce  thermal  gradients  

•  Agita1on  achieved    ▲  Impellers  ▲ Pumps  and  Nozzles  ▲ Both  commonly  used  

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Introduc1on  -­‐  Background  

•  Impellers  •  Pumps  

▲ OMen  used  ♦  Centrifugal  pumps  

■  Low  ini1al  cost  ■  Low  wear  

▲ Applica1ons  ♦  Quench  Chutes  ♦  Open  tanks  

•  Lack  of  significant  literature  on  nozzles  for  quenching  applica1ons  

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Introduc1on  -­‐  Overview  

•  Goal  ▲ Objec1ve  assessment  of  quench  tank  parameters  and  nozzle  performance  ♦  Nozzle  size  (diameter)  

♦  Nozzle  length  

▲ Performance  characterized  using  CFD  

▲ Water  as  quenching  medium  

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Simula1on  Study  –  System  Descrip1on  

•  Typical  Quench  Tank  ▲  Size  3.65m  x  1.83m  x  2.44m  

(L  x  W  x  D)  

▲  Single  nozzle  header  along  tank  centerline  300mm  above  tank  boaom.  

▲  Header  is  100mm  OD  pipe  

▲  5  nozzles  on  600mm  centers  

▲  Two  return  openings  for  return  flow  to  the  pump  

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Simula1on  Study  –  System  Descrip1on  

•  Nozzles  ▲  Diameter  

♦  25.40,  23.86,  20.32  mm  ▲  Extensions  

♦  1”  Schedule  40  pipe  (1.315”  OD)  

♦  0,  25.4,  50.8  and  76.2  mm  long  

▲  Five  nozzles  ▲  Flow  

♦  31.5  Liters  per  second  total  flow  (500  GPM)  

♦  6.3  Liters  per  second  each  nozzle  (100  GPM)  

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Simula1on  Study  –  CFD  Model  

•  Assumed  ▲ Standard  water  proper1es  at  ambient  (25°C) ▲ All surfaces hydraulically smooth (except

upper liquid surface) ▲ Upper surface had symmetry boundary

condition to approximate a free surface ▲ Flow into nozzle header specified as

uniform velocity profile ▲ Water returns at constant pressure

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Simula1on  Study  –  CFD  Model  

•  Computa1onal  Grid  ▲ Used  GAMBIT  for  gridding  

▲ Hexahedral  cells  –  interior  of  header  and  direct  vicinity  of  nozzles  ♦  Smaller  cells  near  nozzle  exits  to  provide  greater  resolu1on  

▲ Balance  of  grid  is  polyhedral  cells  ▲ Total  of  8.5  million  cells  

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Simula1on  Study  –  Computa1onal  Domain  

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Results  

•  CFD  simula1ons  using  AZORE®  

▲ 12  cases  ♦  3  nozzle  diameters  ♦  4  extension  lengths  

▲ Due  to  symmetry,  plumes  lie  on  centerline  

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Results  0”  

1”  

2”  

3”  

1.0”   0.9”   0.8”  

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Results  –  Mass  Flow  Balance  

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Results  –  Devia1on  of  Jet  Angle  

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Results  –  Header  Sta1c  Pressure  

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Results  –  Header  Sta1c  Pressure  

•  Nozzle  Size  ▲  Pressure  loss  strongly  affected  

by  nozzle  diameter  ▲  Longer  extension  length  

resulted  in  lower  pressure  loses  

•  Extensions  ▲  Provide  more  ver1cal  flow  ▲  More  even  mass  flow  split  ▲  Lower  overall  system  pressure  

loss  

•  Predominate  pressure  losses  occur  at  header  nozzle  interface  

Bulk  of  Pressure  losses  occur  at  the  nozzles  

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Results  –  Jet  Core  Velocity  Drop  

•  Velocity  Decay  ▲  75%  decay  corresponds  to  

14  nozzles  diameters  

▲  Can  be  used  to  design  effec1ve  “throw”  

▲  Directed  flow  range  is  limited  but  can  be  used  to  bulk  fluid  movement.  

•  Nozzle  Diameters  ▲  Smaller  nozzle  diameters  

exhibit  greater  penetra1on  

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Results  –  Ver1cal  Velocity  

•  Upwards  flow  shows  similar  results    ▲  2%  difference  between  cases  ▲  No  systemic  varia1on  ▲  Integra1on  shows  average  

mass  flows  of  705  kg/s  •  22X  amplifica1on  in  flow  rate  •  Velocity  spread  

▲  Width  of  nozzle  flow  achieving  1  m/s  velocity  is  about  190  mm    (all  cases)  

▲  Suggests  smaller  spacing  should  be  used    ♦  Assuming  used  to  direct  flow  ♦  Not  bulk  fluid  mo1on  

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Conclusions  

•  From  the  results  of  the  analysis,  the  following  can  be  concluded:  ▲  Open  holes  in  the  header  show  momentum  effects  reducing  the  

overall  width  of  the  flow  field.  ▲  Nozzle  extensions,  straighten  the  flow,  and  provide  a  more  even  

mass  flow  split  between  nozzles  at  a  lower  total  supply  pressure.    ▲  Nozzle  extensions  provide  for  more  even  flow  between  the  

nozzles.  ▲  The  effec1ve  “throw”  at  75%  of  maximum  velocity  of  nozzles  is  

approximately  14  nozzle  diameters.  ▲  Within  the  range  of  nozzle  sizes  tested,  smaller  nozzles  with  

higher  exit  veloci1es  did  not  appear  to  have  any  advantages  •  Results  apply  to  an  empty  quench  tank  and  could  vary  

significantly  for  cases  where  a  load  is  present  

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Acknowledgments  

 The  authors  would  like  to  thank  the  management  of  Airflow  Sciences  and  Houghton  Interna1onal  for  allowing  us  to  present  this  work.