Dear Friends
As we are, at the CAU stoves conference, talking about thermal efficiency tomorrow, here is something to think about. ++++++++ Efficiency is a ratio, but of what to what? Let us follow the heat and decide which 'efficiency' we want to report. 1. Heat available in the raw fuel if it was to be burned completely 2. Heat available in the dry portion of the raw fuel 3. Heat available from the fire considering incomplete combustion 4. Heat available to the pot, at the pot in the hot gas stream passing by 5. Heat transferred to the pot - all of it 6. Heat transferred to the pot and subsequently lost from the pot into the surrounding environment 7. Heat absorbed the pot material changing its temperature 8. Heat absorbed by the water - all of it 9. Heat absorbed by the water changing its temperature 10. Heat absorbed by the water and evaporating water (whether the water is hot or not) 11. Heat absorbed by the water and lost from the water (by radiation, not by evaporation) 12. Heat absorbed into the food and being absorbed chemically (transforming it into cooked food) System efficiency [Overall thermal efficiency] is (7+9+10+12)/1. [When boiling water only #12=0] Heat transfer efficiency is .. ? Which one is the one you were thinking of when asked about 'thermal efficiency'? +++++++++ Regards Crispin
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