how many litres of honey are there in a flow frame?
Hello and welcome to the Flow forum!
The answer is that it depends… 
The volume is quite variable, depending on how much the bees have waxed and drawn out the plastic frames. I would say maximum around 2 liters, often around 1.5 liters. Also, if you only harvest for 1 hour, you will get a lot less than if you leave the frame open for 6 hours+