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 Home Brew Forums > 5500w ULD element taking too long to heat

11-28-2012, 04:37 PM   #141
jeffmeh
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Quote:
 Originally Posted by ajdelange Your belief flies in the face of physics as it does not include the amount of energy being delivered to the water/wort. If, in a boiling kettle, you double the energy per unit time (power) delivered to the kettle by switching on a second element, increasing the gas flow to a burner, increasing the amount of steam delivered to a jacket or whatever where can that energy go? It cannot go into increasing the temperature or pressure in a vessel open to the atmosphere (though it can in an enclosed boiler e.g. a pressure cooker). It cannot be lost through the sides of the vessel as the heat loss there is proportional to temperature and the temperature is fixed (though in an improperly skirted gas system some of the heat from the bigger flame would be lost). It can't go into the creation of mass. The only place that energy can go is to increased rate of vaporization. I don't see how you could have failed to observe that if you put a pot on the stove it boils more vigorously when you turn up the heat. Same surface area - more steam production.
If that was directed at me, of course you are correct. I was trying to point out that with everything else held constant, the boil-off rate is a function of the open surface area. I failed to explicitly point out that the heat applied must also be held constant. Holding that constant is much easier with electric than propane, lol. I will edit the post accordingly.
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11-28-2012, 05:41 PM   #142
Yambor44
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Quote:
 Originally Posted by NiteOwlBrewing Thanks fellas for the input. My question on boil off rate centers more around whether it is a % of volume of the liquid in the kettle or more an absolute volume. In my test with 18 gallons I boiled off ~2 gallons in 60 minutes of boiling. This is around 11%. So, if I'm boiling 21 gallons would my boil off be the 11% of the 21 gallons (~2.3g) or the 2 gallons (~9.5% of the 21 gallons)? Seems to me the surface area of the liquid is the same, so the evaporation amount in gallons would be roughly the same as well. Also of note, I'm not sure I see a reason to dial back the 5500 with boil sizes in the range of 15-21 gallons. It may be the shape of my pot driving this mostly though. Are other people getting violent boils with a 5500 ULWD? I may try another 10 gallon batch to see if the boil seems to vigorous.
See video in post #122 above. I have a 550W ULD and that is 75% power to the element. I later turned it down to 70% and finished boiling off about 2.25 gallons if I recall correctly starting with 13.25 gallons.
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