# Evaporation of Bourbon from a Wooden Barrel

by potus77
Tags: barrel, bourbon, evaporation, wooden
 Sci Advisor P: 5,508 Flow through the wall of a permeable cylindrical object can be modeled as: $$v_{R}=\frac{K}{\mu} \frac{\Delta p}{d}$$ Where v is the velocity of the radial flow (i.e. out of the container), K the permeability, μ the viscosity of the fluid, and Δp/d the pressure gradient between inside and outside. Using the vapor pressure of EtOH (6 kPa), a wall thickness of 2 cm, and a permeability of wood of 0.1 milliDarcy (a crude estimate based on http://eng.med.wanfangdata.com.cn/Pa...=zwxb200102002 and http://en.wikipedia.org/wiki/Darcy). Then, convert v to a volume flow Q = v* area of barrel- I estimated 0.3 liters/hr, which is *way* too high. Alternatively, you can use the measured losses as a measurement of K. A barrel holds about 180 liters and is aged for (say) 7 years- a 30% loss is 9*10^-4 liters/hr, so the permeability is likely closer to 0.1 microDarcy.