Let’s say, bring 1 liter of water from 0 to 100 degrees C in the same +- closed vessel. (Gas, electricity, it doesn’t matter. I guess) With high power in short duration or at low power for long duration? My gut feeling is that it is best done gradually. On a low fire, which goes higher and higher in function of the energy that the water has already absorbed. But what is the right solution, and why?
Answer
Hi Hugo,
Heating 1l of water from 0 to 100 degrees in an insulated system at atmospheric pressure always costs you the same amount of energy, namely 418.6 kJ or 0.12 kWh.
If you heated water very slowly in an open pan, the water would also cool slightly at the top during the heating. If you take that into account, it is best to heat it up as quickly as possible, for example in a kettle.
The conclusion is that to heat water from 0 to 100 degrees, the water must absorb a fixed amount of energy. It is important to lose as little energy as possible to the environment during heating itself.
regards,
Joachim
Answered by
ir. Joachim Druant
Electrical energy, systems and automation
http://www.ugent.be
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