Whirlpool vs. flameout

Greetings,

I was looking to take my flameout addition and whirlpool it at 140 for 30 minutes.  When I did this in BeerSmith, it upped my IBUs 15. It says the hop utilization factor should be set to 50% for 194 F.  So I guess my question is, what should the utilization factor be for 140?

It depends on which source you want to believe. There's nothing scientific about predicting isomerization after the boil.

I could go on about perceived vs measured bitterness findings (you often perceive more bitterness than is measured) and various brewery experiments in whirlpool time (very long contact time enhances hop flavor and aroma), but it'd still come to the same point.

Feel free to adjust the IBU utilization down to 10% or zero for 140oF. Just don't let an IBU number change how much you'd add for flavor and aroma. IBUs don't correlate to bittering perception and if you're above 55, then it's basically moot, since that's the limit of perception for nearly everyone.