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According to this link (along with many other PWR papers), the inlet temperature of the secondary into the steam generator is around 450-500K, with a pressure of 5-8MPA. How does the temperature of the secondary get this high? I understand the high pressure component - that's simply the Rankine cycle - but where is the secondary heated to hundreds of K above ambient temperatures?

EDIT: When steam is put through a turbine, it is eventually condensed and cooled to ambient temperature. My question is basically: at what point is this room temperature water heated to 450K?

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    $\begingroup$ I'm not sure I understand the question "How does the temperature of the secondary get this high?". The primary water circulation is hotter than the secondary water circulation, and both are under a LOT of pressure. $\endgroup$
    – David White
    Commented Aug 27, 2019 at 23:47
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    $\begingroup$ "About 25% of the secondary coolant is converted to steam on each pass through the generator, and the remainder is recirculated." So the ~75% of water that is not evaporated retains much of the heat. $\endgroup$
    – BowlOfRed
    Commented Aug 28, 2019 at 2:33
  • $\begingroup$ The question is how the water from the condenser that is sent to the steam generator enters the steam generator at such a much higher temperature than the temperature from the condenser. The answer is internal feedwater heating is used to increase the thermal efficiency of the cycle. Please see my answer. $\endgroup$
    – John Darby
    Commented Nov 9, 2020 at 3:37

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I think your confusion is that a condenser does not cool to ambient temperature, it cools to saturated conditions. The water needs to be subcooled before it enters the pump, but it is still at relatively high temperature and pressure.

There is another loop that cools the condensor. This third loop is usually connected to a cooling tower, lake, or river. The exit of the third loop is ambient.

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This is a very good question. I think other responses did not understand your question. I believe your question is how the inlet water to the steam generator is raised to such a high temperature, higher than the temperature of the water from the condenser that sends water to the steam generator. The answer is the secondary system has many stages of moisture separators and feedwater heaters to pre-heat the water before it enters the steam generator. This is to increase the thermal efficiency of the cycle. A good engineering text on thermodynamics, such as one by Sonntag and Van Wylen explain this.

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