I am trying to calculate the amount of energy required to bring 1 litre of water up to boil (from 20 degrees C to 100 degrees C) and to maintain the water temperature at 100 degrees C for a period of 5 mins.
The end goal is to translate this into the theoretical amount of wood required to do so over an open fire using the default net calorific value of wood (0.0156 Tj/ton), and assumed 10% efficiency of an open fire.
So far - using the Specific Heat of Water as 4.186 kJ/L I have calculated that the energy required to bring the water up to the boil would be:
1 x 4.186 x (100-20) = 334.88 kJ
My question is: how do you calculate the amount of energy required to maintain a water temperature of 100 degrees C over a period of 5 mins.
I have looked into using the Latent Heat of Water Evaporation value of 2260kJ/L multiplied by the % of water that is vaporised over that period. However- I do not have a figure for rate of vaporisation.
Secondary question: how do you calculate the rate of vaporisation assuming the power being applied by the heat source is constant?