Understanding Temperature Stratification in Brewery Tanks

Temperature stratification in brewery tanks can occur in tanks of all sizes, but larger tanks are more prone to this problem. Stratification is more likely to happen in tanks with low turbulence, such as bright tanks without a carb stone. The process of stratification is most significant when the tank is being cooled and approaching temperatures around 0C or 22F. As the cold liquid rises in the tank, it disrupts the stratification. Fermenters, with their CO2 evolution during active fermentation, are less prone to stratification. Understanding the relationship between temperature and density is crucial to managing temperature stratification in brewery tanks, as water behaves differently than most molecules. Water becomes denser when it starts getting colder, with its maximum density at around 4C or 39F. As the water cools beyond that point, it becomes less dense until it freezes. Cold stratification occurs due to this changing density of water, creating challenges for brewers trying to cool their beer to low temperatures. Factors that can promote temperature stratification include lack of CO2 evolution, high coolant flow or colder glycol, long storage time, and aggressive cooling rates. To mitigate or avoid temperature stratification, brewers can consider controlling cooling rates, using analog valves instead of discrete cooling valves, cooling tanks with only the cone when reaching low temperatures, maintaining the right jacket surface area to volume ratio, considering warmer glycol temperatures, and using reverse return glycol piping systems or pressure independent control valves (PICV). In cases where poorly engineered equipment or installation causes stratification, options such as bubbling CO2 gently into the tank, using a mixing device, lowering process temperatures, or adjusting the temperature to the next process step could be considered.