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I'm reconfiguring my setup so I decided to finally try to calculate my boil off rate.

Does ~10L/hr sound right?
I have a 5500w element and ran it full tilt

Wow! 10L per hour?! That's at least double what I experience.

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5500W * 1 hr = 19800 kJ

Enthalpy of vaporization of water = 2257 kJ kg−1

19800/2257 = 8.77 kg = 8.77 L

My chemistry/thermodynamics are pretty rusty, but it seems like the maximum from a physics standpoint is 8.77 litres. And that doesn't account for any other sources of heat loss (i.e. wasted heat out the sides and bottom of your pot). I'd guess something like 7-8 L/hr would be the more reasonable range of possibility.

We'll, I was standing next to it for most of the time... Maybe my hotness helped accelerate it.

More experimenting required it seems

my 20gal pot and darkstar burner boils off 10L an hour.

You need to take into account the surface area I think. Wider pot will boil off more then a slim one IIRC.

My 19G pot with Blichman burner evaporates 6.67L per hour ...

Measure it. I know we should be able to calculate but experience is better IMHO.

S

GAM wrote: ↑

Tue Apr 11, 2017 1:31 pm

Measure it. I know we should be able to calculate but experience is better IMHO.

S

Werd Dawg... I did, but I noticed that 10 litres from my garden flow meter rose to the 14 litre line on my bucket. So I called it 14 units and converted it back at a rate of 14 units being = 10 liters

All that to say I need to remeasure

Can't remember how much water changes its volume with temperature but the most accurate way to measure the evaporation rate should be by weight. Weigh the pot and water. Boil and then re-measure.

Broob wrote: ↑

Tue Apr 11, 2017 2:26 pm

Can't remember how much water changes its volume with temperature but the most accurate way to measure the evaporation rate should be by weight. Weigh the pot and water. Boil and then re-measure.

I allowed it to cool back to room temperature

Broob wrote: ↑

Tue Apr 11, 2017 2:26 pm

Can't remember how much water changes its volume with temperature but the most accurate way to measure the evaporation rate should be by weight. Weigh the pot and water. Boil and then re-measure.

I believe it expands by 4%

bluenose wrote: ↑

Tue Apr 11, 2017 2:44 pm

Broob wrote: ↑

Tue Apr 11, 2017 2:26 pm

Can't remember how much water changes its volume with temperature but the most accurate way to measure the evaporation rate should be by weight. Weigh the pot and water. Boil and then re-measure.

I allowed it to cool back to room temperature

Did you chill it quickly, or just let it rest? There would be more evaporation if it sat for hours to reach room temp vs using an immersion/counter-flow chiller. I assume you'll be using a chiller with a real batch.

weighing your pot + water is definitely the most accurate way to measure it. it would give you a sanity check on the output from your flow meter too.