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Water Temperature gain calculation

  1. Sep 2, 2010 #1
    Water is being pumped into a tank on a ready mix concrete plant in Palm Springs CA

    Water is chilled to 45 degrees into a 18' x 3' tank with 1/4 inch steel walls.

    Depending on ambient air temperature, how long will the water take to warm from 45 degrees to 65 degrees.

    Is there a calculation where I can input the daily temperature forecast and know how long the water temperature will be adequate for our production schedule.

    Hope I got all the facts up front, thanks in advance.
     
  2. jcsd
  3. Sep 2, 2010 #2

    berkeman

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    What is the steel tank sitting on? You might lose a lot of heat out the bottom, as opposed to the air.

    Can you post a picture of the setup?
     
  4. Sep 2, 2010 #3
    The tank is welded to the frame of the plant itself, no support legs or anything like that.
    I am working on locating a picture for you, will I be able to attach it or paste in a reply on this forum???
     
  5. Sep 2, 2010 #4

    berkeman

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    As long as it's not too big of a JPG file, you should be able to attach it.
     
  6. Sep 2, 2010 #5
    Hope the pics made it through
    The top of the tank is just visible in pic # 1242, I believe the whole tank is visible in pic # 1239
     

    Attached Files:

  7. Sep 2, 2010 #6

    QuantumPion

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    There are four methods of heat transfer you have to consider:
    a) natural convection on the outside of the tank (assuming no wind/forced convection). This depends on the size of the tank, its surface temperature, and the ambient atmospheric conditions.
    b) radiation on tank, which depends on the material and coating of the tank exterior, as well as whether it is placed in the shade or direct sunlight.
    c) internal natural convection of the tank - to determine the surface temperature of the tank.
    d) conduction through the bottom of the tank - this depends on the structure that the tank is located on, and the surface temperature.

    I think you would probably need a computer model of some sort to analyze this problem exactly, although maybe this is a class of problems/correlations you can find in an engineering handbook.
     
  8. Sep 2, 2010 #7
    I do know the tank has full sun on it in the morning, there is no insulation of any sort.
    It is depleted about 300 gallons per truck that is batched with a ready mix of concrete, the pump will fill the tank at 250 gpm. I do know that the pace of batching can be quite rapid or sometimes be up to 15-30 minutes between batches.
    I am lost with this kind of calculation, any idea how to narrow down where to go for a solution?
     
  9. Sep 2, 2010 #8

    QuantumPion

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    I think analyzing this problem would require modeling it in matlab or something. Is there some reason why you can't just stick a temperature probe in the tank and measure it? :p
     
  10. Sep 2, 2010 #9
    We didn't think it be that involved to do the calculations. We have to chill the water according to our production schedule and knowing how much we might need as the forecast changes would help.
    We could certainly start taking readings from a probe and build our own tables, but, we thought a calculation would be quicker and easier is all.
     
  11. Sep 2, 2010 #10

    QuantumPion

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    I'm not a mechanical engineer or deal with this sort of problem at work so don't take my word for it, I'm just remembering my college heat transfer class :p

    I'm sure this type of problem comes up all the time in different industrial situations, there probably is a simpler way to calculate it that I'm not aware of.
     
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