Burner output

[gunner]

I have recently aquired a bitumen burner from my mate who's in the roofing game.He couldnt remember what the output was,so my questions are:-

1.How or where would i be able to the find the output of the burner.(I'm presuming its pretty high for the sort of job its been doing)

2.What sort of output would you need to comfortably boil 40-50L batches.

Any advice guys.

Regards Graham.

[mbt22]

As a first guess, assume that the wort is all water. Decide how long you want to wait to bring it to the boil, say 20 minutes. Start the wort at 10 deg C and take it up to 100 (so actually total time to heat water up to mash temp, then bring wort to the boil).

Power = Mass liquid * heat capacity * temp change / time
Power = 50 kg * 4200 J/kg/K * 90 deg C / (20 min * 60 s/min) = 15750 J/s = 15.75 kW

Add on a chunk for heat losses (say 50%?), and there you go.

Personally, I'd just "calibrate" it by trying to boil some water.

At 15.75 kW heat input, you'd be boiling off about 25 litres of wort per hour! If your burner can heat the water in a sensible time, it feels like you'd be OK maintaining the boil!

[gunner]

Cheers mbt22.

When you say boiling off 25L,is that to mean a rolling boil for 60min? If it does mean this would i need to double the output for the burner to double the brewlength from 25L. I'm a little confused.

Regards Graham.

[mbt22]

15.75 kW is actually enough to evaporate 25 litres per hour. In other words, if the burner's big enough to boil the wort that quickly, it needs turning down to maintain a boil without evaporating all your wort.

[gunner]

Many thanks.

Graham.