In any ORC design, we set two temperatures depending on the optimization method: the ORC boiling temperature and the heat exchanger pinch temperature difference. The boiling temperature is the temperature where the fluid phase changes from liquid to vapor (States 3 to 4 in Figure ). The boiling temperature is set by controlling the pump outlet pressure. The heat exchanger pinch temperature difference is the smallest temperature difference in the heat exchanger between the primary and secondary fluids (sometimes called the "pinch point"). In Figure , the temperature difference between the water (blue line) and R245fa (orange line) is smallest at State 3, thus the pinch temperature difference is 5°C in that example.