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Another heat engine efficiency problem

  1. Feb 14, 2007 #1
    A reversible heat engine has an efficiency of 34.2%, removing heat from a hot reservoir and rejecting heat to a cold reservoir at 0°C. If the engine now operates in reverse, how long would it take to freeze 1.10 kg of water at 0°C, if it operates on a power of 183 W?

    I am getting stuck on how I can incorporate the kg of water and the power.
    I don't know which equation to use that will let me use those constants and allow me to find time.
  2. jcsd
  3. Feb 14, 2007 #2


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    Homework Helper

    Well, to freeze water, you have to remove thermal energy from it. How do you find the amount of energy needed to be removed for a phase change of the water at 0°C to ice at 0°C?
    It gives you the power the engine is operating at. What is the definition of power?
    I'd think about those things to start.
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