Calculation Check

[eskimobob]

Hi PoP,

That's what I have done in the spreadsheet (at least it is now I have corrected the equation - you probably need to download it again)

You specify your final wort volume required at the top as well as your evaporation rate and boil length then it works out the dough-in liquor quantity and sparge quantity.

If you wanted 22.73 litres finished volume then you would do:

Initial quantity in the boiler = wanted final volume + evaporation amount

where evaporation amount is:

evap = initial quantity * (% / 100) * (boil time / 60)

so rearranging: initial quantity in the boiler = 22.73 / (1 - ((% / 100) * (boil time / 60)))

so for 10% evap/hour and 90 min boil time you need to start with 26.74 litres in the boiler.

:stun

[PieOPah]

Thanks for the help EB.

I have made a few changes to my spreadsheet based on your workings. This lets me include the evap rate so now I just specifiy how much I want at the end.

I have kept the 'top up' water for adding to the dough-in. I have also included the Dead Space to the initial dough-in water since this will never be part of the absorbed wort. Because of this it won't be part of the absorbed water so to ignore it would mean I would unlikely have enough water so a lot of the grain would be dry!

As I am writing this I have realized that about half of this dead space will still be collected so I need to faction that into the equation Currently none of the dead space is being collected!!!!

Will get the calc sorted soon enough

[tribs]

I think you are correct to keep the "top up". I do the same. It enables you to keep the correct water/grain ratio and to have two equal run-offs which provides optimum efficiency when batch sparging.