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How to size the circulating pump for open cooling tower?

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More specifically: 

  • How to calculate the pump's head?
  • How to calculate the pump's flow?
asked Aug 28, 2014 by Mepanet

1 Answer

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                  ht = hf + hch + hct

   ht = Total pump’s head (ft)

   hf = Friction loss in developed length of longest pipe run in system per 4’/100’ friction loss (ft)
   *Developed length is total length of supply and return including equivalent length for fittings         (rule of thumb: 3 times of supply pipe)

   hch = Pressure loss in chiller’s condenser

   hct = Pressure loss in cooling tower


                  gpm = Q/500∆T


   Q = Total chiller’s load (Btuh)
   500 = Factor for converting lb of water to gpm – Btuh

   ∆T = The temperature difference between condenser water supply and return (℉)

answered Aug 28, 2014 by Mepanet

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