Binary Geothermal Plant: Evaporator Pinch Point (2D T-Q Diagram)

This is the engineer's-eye-view companion to the 3D binary geothermal plant simulator: instead of watching particles flow through a loop, you watch the actual temperature vs. cumulative heat (T-Q) diagram that ORC evaporators are designed from. Brine cools along a straight line as heat leaves it; the working fluid heats along a steeper line until it starts boiling, then holds flat at its saturation temperature. The gap between those two curves is the driving temperature difference the heat exchanger's metal has to work across — and real designs cap the tightest point of that gap (the "pinch") at a minimum, typically 3–10 °C, because a vanishing gap would need infinite heat-exchanger area to move the required heat. Push the requested working-fluid flow rate up and watch a live bisection solver clip the achievable heat duty — and therefore the achievable net power — the moment the pinch constraint would be broken, exactly the calculation a plant designer runs by hand.