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Pressure drop problem (using the darcy law)

  1. Jul 24, 2012 #1
    1. The problem statement, all variables and given/known data

    Estimate the pressure drop in a tower packed with porous support. This tower is an integral part of a water oxygenation system and will need to operate over extended periods without cleaning.

    From the following data estimate the pressure drop you expect to see on start-up

    Diamter = 1.5m
    Height = 3m
    Support size = 0.004m

    2. Relevant equations

    Δp = (uμh)/β

    u is liquid velocity
    μ is liquid viscosity (I.e. water)
    β is bead permitivitty (I.e the support)

    3. The attempt at a solution

    I have had no problem calculating β and got 4.9 x 10^-9m
    Where I get stuck is finding 'u'

    for these problems I usually use the formula u = Q/A
    Volumetric flow rate over cross sectional area - however in this instance there is no information about the volumetric flow rate

    Should I assume a volumetric flow rate? Or is there a way to calculate it from the above information? (sometimes they give something away in the wording such as 'start up' - not sure what I should take from that)

    Are there any other equations I can use? This is a 15 mark question so I'm assuming there's a bit of calculation that needs to go into it.
     
  2. jcsd
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