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Cooling of a tunnel

  1. Oct 21, 2005 #1
    A cooling system that pumps 177,21 kg/s of water in a tunnel warmed by trains with an average thermal output of 37,125 mega watts. I have to estimate the energy which is necessary to run the system in order to cool down water with the mass M. Both in the general case and on the assumption that the new water temperature is nearly the same.

    I have never made an estimation in physics before. Do I have to calculate? Is there a difference between both cases?

    Normally the formula for thermal power is p=(m*c*dT)/t. Can I apply it?

    Thank you for your support.
  2. jcsd
  3. Oct 22, 2005 #2


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    Staff: Mentor

    You have a mass flow rate [itex]\dot{m}[/itex]=177,21 kg/s multiplied by the specific heat and temperature difference should equal the power. But what it the temperature difference.

    Also, one is asking for the "energy which is necessary to run the system", which sounds like a fluid mechanics or hydraulics problem, and one would need more information.

    What is mass M?
  4. Oct 27, 2005 #3
    M is a parameter.
    I know the formula you mean but I think something about the Carnot heat engine is demanded:

    But I can't apply the equations to my questions because I want to calculate the necessary power.

    Can anybody help me?
    Thank you
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