whirlpool

Can someone explain to me the process of whirlpooling and whirlpool hop additions, also how do you calculate ibus in whirlpool additions.
In my system i chill my wort with an inmertion chiller.

Thanks

Whirlpooling causes the solids in the wort to collect in the center of the brew kettle so that less trub/hop particles make their way into the fermentor when you transfer via ball valve or siphon. You stir the wort to create and whirlpool and wait 20-30 minutes for everything to settle out before the transfer.

Adding hops at this time is done to retain more of their essential oils (aromas) compared to a boil addition. As long as the temperature of the wort remains above 185 degrees or so, you'll also continue to isomerize alpha acids, meaning the bitterness of the beer increases. Unfortunately, the formulas for calculating bitterness do not take post-boil isomerization into account. Some people get around this by simply adjusting the timing of the additions in their brewing software. For example, if you boil for 60 minutes and whirlpool/rest for 20 before chilling, your 60' boil addition is treated like a 70 or 80 minute addition in the software. Your flameout/whirlpool addition then becomes a 10 to 20 minute addition.

Skip flameout additions altogether and focus on a warm-whirlpool-aroma-steep at about 165 F or lower. So essentially, quick cool your wort from 212 F down to 165 F, then stir in your whirlpool hops, and now slow-chill your wort down to 65 F over the course of 20-30 minutes or longer with no worry of putting your IBU count off whack... You basically just get tons of aroma/flavor.