Vaporization rate

[Fyreaway]

For those of us cooking with gas or oil is there any real return on investment of more fuel once the boiling point is reached? In my quite unscientific method of measuring, I'm not seeing a real increase in evaporation rate in adding more BTUs to the boiling pot. I am adding raw sap to the evaporator through a siphon with a needle valve to control the flow rate. When I reach that point where I can maintain boiling temperature and keep a constant input I gain almost nothing when I add more heat. I read about the wood burners adding blowers to increase the temps of the fire so there must be something to the theory of more BTU meaning faster vaporization. Is there really any practical gain in using more fuel than is necessary to keep the system at the boiling point?

[PerryW]

I believe there is an advantage to adding more head after the boiling point is reached. If you are cooking food in the water (like Pasta) there is no advantage to adding more heat to the pot once you have reached boiling, since the cooking water will never get any hotter that 212.

But for making syrup, adding more heat to an already boiling pot increases the evaporation rate. In other words a full raging boil evaporates quicker than a slow rolling boil.