Chiller Systems There are several steps or unit operations within the brewing process and beer storage/dispense process in which having a source of cooling is important Process Step Purpose Where it Happens Wort Chilling To rapidly cool boiling wort to proper yeast pitching temperature Heat Exchanger Fermentation Temperature Control To maintain optimal temperature conditions for yeast to metabolize wort sugars (yeast generate heat as a by-product of fermentation) Fermentation Vessels Cold Liquor Generation To cool water for use in mash temperature management Cold Liquor Tank Beer storage Keep finished product at low temperature Storage Room Beer dispense Ensure beer lines from serving tanks/kegs are kept at proper beer serving temperature Beer dispense lines Fluid Dynamics Lecture XXX - P 1

Chiller Systems In breweries, this cooling capacity is usually provided by using a chiller system that cools a propylene glycol and water mixture that is then circulated through a cooling loop to the locations where cooling is needed. The chiller system is essentially a refrigerator that cools liquid, that then cools other stuff in the brewery Propylene glycol is a food-grade antifreeze (food grade antifreeze is required when a food product (e.g. wort/beer) is being cooled). The glycol cooling loop for a brewery typically operates in a temperature range of 25-27°F Here’s a schematic showing a typical glycol chiller cooling loop used in a brewing application: Fluid Dynamics Lecture XXX - P 2

Chiller Systems xxxx Fluid Dynamics Lecture XXX - P 3

Chiller Systems In order to have the glycol/water solution at such a cold (25-27°F) temperature, it is important to have the correct concentration of glycol in the cooling loop solution Fluid Dynamics Lecture XXX - P 4

Chiller Systems Chart showing effect of glycol concentration on freezing point Fluid Dynamics Lecture XXX - P 5

Chiller Systems Question: Why does the freezing point of the cooling loop liquid need to be so cold (in the range of -6 to +5°F) if we only need to operate at 25-27°F ? Your thoughts………..? Fluid Dynamics Lecture XXX - P 6

Chiller Systems The temperature of the refrigerant that is cooling the glycol/water mixture will be operating at a temperature that is about 10-15°F colder that the set point of the temperature of the glycol/water loop. If the glycol/water cooling liquid loop setpoint is 27°F, the temperature of the refrigerant loop will likely be around 12-17°F The glycol/water solution needs to be able to remain a liquid at the coldest temperature that it will encounter at the heat transfer surface of the refrigerant. It is good practice to have the freezing point of the glycol/water solution be 20-25°F lower than the chiller system set point. Example: CHILLER SETPOINT: +27° FAHRENHEIT GLYCOL FREEZE LEVEL: + 7° to +2° FAHRENHEIT Fluid Dynamics Lecture XXX - P 7

Chiller Systems In colder climates, it is important to be sure that the glycol/water freezing point is below any anticipated extreme low-temperature ambient condition. A reasonable glycol/water solution for use in a brewery chiller application may consist of a by-weight mixture of 36% glycol and 64% water. This will ensure protection from freeze up down to a temperature of about 1°F Fluid Dynamics Lecture XXX - P 8

Chiller Systems !!WARNING!! It is very important to use the proper blend of glycol/water in the chiller system ! Using too little glycol could lead to system freeze-up and could cause severe damage to the system internal rupture of the chiller evaporator rupture of cooling lines Using too much glycol will drastically reduce the efficiency of the chiller system If you don’t have a chiller, you can’t make beer………so operate it correctly ! Fluid Dynamics Lecture XXX - P 9

Chiller Systems A chiller system for a brewery is sized to meet the anticipated maximum instantaneous demand for cooling, plus a “safety factor” to account for unanticipated deviations from the assumptions used in the calculations. Maximum instantaneous demand would occur when all of the below are happening simultaneously: Wort chiller is in use All fermenters are in active fermentation situation Storage room cooling unit is operating Water is being chilled in the cold liquor tanks Assumptions used in sizing chiller systems include Maximum instantaneous cooling demand Glycol/water solution concentration Ambient temperature conditions System efficiency Insulation properties of cooling loop Etc….. Fluid Dynamics Lecture XXX - P 10

BTU/hr heat removal assuming 27°F glycol @ 90°F ambient Chiller Systems Chiller sizes are often stated in units of horsepower (HP) How this converts to energy transfer units depends on the specific system configuration and operating situation One vendor (Chilstar) provides the following data for conversion between HP and BTU/hr heat removal capacity: System HP BTU/hr heat removal assuming 27°F glycol @ 90°F ambient 2 15,000 3 20,000 5 35,000 7.5 56,000 Fluid Dynamics Lecture XXX - P 11