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Homework Help: Question about Multiple Stream Mixings into Units

  1. Apr 23, 2012 #1
    1. The problem statement, all variables and given/known data

    I'm currently doing some thermodynamic analysis. I don't know where to put this question, but here goes:

    I have a system that has two streams entering a condenser, and one leaving. I don't know mostly anything about two of the streams.

    One stream I have fully defined via other unit balances. I am making an assumption: all streams entering the condenser must be the same pressure, and as a result, so too must the exit stream. The exit stream is a saturated liquid, from the question.

    I am making this same assumption on a feed-water heater, which has two streams in, and two streams out. One of the streams leaves as a saturated liquid to a throttler, whose exit stream goes back to the condenser.

    The feed-water heater's other outlet stream goes to a boiler, and then to a two turbine system, where between the two turbines, one stream goes to the feed-water heater. The second turbine's outlet goes to the condenser.

    I'm having a real tough time trying to balance the multi-stream units. This is an intro to thermodynamics class with one of the worst lecturers in history. We have learned how to balance units when one stream enters and then exits. We have not learned anything about units that have multiple streams entering.

    So far, we have learned that mixing points are adiabatic with equal pressure inlets. We also know that heat exchangers (which I assume the condenser and feed-water heater are) do no work, and the enthalpy is equal to Q.

    Could I just get a few tips/facts about how to go about this unit balance?

    Here's a picture. See attached:

    Attached Files:

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  2. jcsd
  3. Apr 25, 2012 #2
    I have solved the question after clarifying some assumptions that were not given to us.
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