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A question about condensing turbines

  1. Apr 16, 2017 #1
    I want to know that whether in case of condensing turbines, the Latent heat of the steam part that will be condensed will be converted into power or not. In that case, condensing turbines can produce more power with the same temperature and pressure difference.
  2. jcsd
  3. Apr 17, 2017 #2


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    Staff: Mentor

  4. Apr 17, 2017 #3
    I really like the short answer of Russ. Yes is to the point.
    It would be quite rare that one found a condensing turbine in any other configuration than a compound reduction power plant. In this sort of train there is a higher power turbine (or more than one) that mostly utilizes the heat energy available. As the heat is reduced to close to transitional phase it passes the last turbine which has a condenser following. Remember that that there is also a large volume change accompanying the state transition between vapor and liquid. This creates a low pressure region causing the "low pressure turbine" to operate at a usable differential. In this way there is a very large conversion of energy.
  5. Apr 18, 2017 #4


    Staff: Mentor

    We need some clarification to avoid misleading the OP @pranj5 . @russ_watters answer is correct to the extent that gas is condensed in the turbine. But typically, steam exits the turbine saturated with maybe 10-15% moisture. The lion's share of the condensing happens in the condenser, and that latent heat is lost

    In a typical steam power plant using very rough numbers, 1/3 of the energy is extracted by the turbine and 2/3 of the energy is lost in the condenser.

    The problem is the very misleading, but standard, terminology "condensing turbine" as opposed to "back pressure turbine." The words make is sound like it is the turbine that does the condensing, not the condenser. http://www.turbinesinfo.com/types-of-steam-turbines/ [Broken]
    Last edited by a moderator: May 8, 2017
  6. Apr 18, 2017 #5
    It can be easily understood that turbines convert a part of the gross enthalpy of steam. What I specifically want to know is that whether "condensing turbines" can convert a part of the Latent Heat of the input steam into power or not. As a part of the steam is condensed inside the turbine, that means they release the LHV. If that's not converted into power, where can it go?
    Seems that all here agree to the fact that condensing turbines can convert the LHV of the condensed steam into usable work. By this standard, they can produce more power in comparison to back pressure turbines with the same temperature difference, right?
  7. Apr 18, 2017 #6


    Staff: Mentor

    Yes. You were not mislead. You got it right.

    Energy is conserved, so if you do a balance between the energy of the flows coming in and the energy of the flows coming out that is the energy extracted by the turbine. But to be precise, you must account for all the extraction flows, steam seals, and moisture removed from the steam path and drained away without going all the way through the turbine. On a large steam turbine, there are hundreds of "out flows" to account for.

    I don't know how precise you need to be.

    Sometimes low pressure turbine blades have grooves specifically to extract moisture, because water droplets are bad aerodynamically. They cause erosion and loss of efficiency.
  8. Apr 18, 2017 #7
    I just want to be assured that condensation turbines can produce more power with same temperature difference as they can extract the LHV of portion of input steam that has been condensed. What you are saying can be easily calculated if the consider the mass of steam input and output to be the same. Drainage of droplets have to be added to the output in that case to keep the input and output mass to be the same.
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