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Pressure calculation

  1. Aug 18, 2015 #1
    Hello guys,

    I have problem to calculation pressure due to heated water in a closed tank.
    1. Tank with full of water.
    2. Tank with half of water.

    Does anyone has idea?
    Thanks a million.
  2. jcsd
  3. Aug 18, 2015 #2


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    Gold Member

    Is this homework? Did you attempt a solution?
  4. Aug 19, 2015 #3
    It is part of study that has been carried out
  5. Aug 19, 2015 #4


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    Staff: Mentor

    You didn't provide anywhere close to enough information for us to be able to help you. Heck, other than asking for help, you didn't even ask any questions about the issue you are trying to investigate!
  6. Aug 21, 2015 #5


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    Welcome to PF.
    Can we assume external pressure is atmospheric and that water temperature = tank temperature.
    Assume water temperature is liquid and between 0°C and 100°C, or you could have an ice burst or a steam explosion.

    Consider case 1.
    Assume tank contains no gas bubbles.
    What material is the tank made from? Tank expands in three dimensions as it gets hotter. What is expansion coefficient and Young's modulus of tank and of water?
    Water in tank expands as it gets hotter. If the water volume expands faster than the tank volume then the water will be compressed and the tank stretched. There will be a pressure in the tank due to those relative expansions and pressures. At some point the tank will burst.

    Consider case 2.
    Half full of water and half full of what else, air, water vapour or another liquid such as oil?
    If other half is a gas then the gas will be compressed or rarefied to make up for the differential expansion of tank and liquid. The solubility of gas in water may be important.

    Ullage is not always bad, it is essential to safety. Look up the word ullage.
    See also; https://en.wikipedia.org/wiki/Ullage#Industrial_use
  7. Aug 24, 2015 #6
    In case 1, I think they want you to assume that the tank volume does not change. You are starting with pure liquid. Are you familiar with the concepts of coefficient of volumetric expansion and bulk modulus?

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