A chiller is involved in more steps of the beer making process than you think.
Your cooling and glycol system works hard for your brewery. Show it some love.
Your cooling and glycol systems, better known as a chiller, is the most important piece of equipment in your brewery. Why? First, there is no other single piece of equipment directly or indirectly involved in so many steps in the process of making beer. While milling, mashing, lautering, and boiling are hard concepts to connect with the chiller system, the heat added during these processes is removed by the chiller. One of my favorite analogies is: “The Boiler is the gas pedal and the chiller system is the brakes."
Let's examine the steps of the beer making process to see how glycol is used along the way.
Wort Chillers and Glycol
1. Cold Liquor Tank (CLT) and a Single-Stage Wort Heat Exchanger
The CLT is typically a stainless steel water tank with cooling jackets or an external heat exchanger. The CLT is filled with water that is chilled between brewing cycles to a temperature around 35 F. This cold water is then pumped through the wort exchanger at a 1:1 ratio, cooling the wort from post boil temperature to the desired fermentation temperature. The exiting water, (now 140-160 F) is transferred to the hot liquor tank to be utilized for the next batch of beer. The CLT is often sized to hold enough cold water to service a typical 24-hour brewing cycle. For example, if you have a 15 Bbl brewhouse, and will typically brew three times per day, the CLT would be sized at 45 Bbl.
2. Two-Stage Cooling using City Water and Chilled Glycol
Two-stage wort exchanger cools the wort in two steps:
Step 1 utilizes city water at a 1:1 ratio, removing as much heat as possible. Depending on heat exchanger efficiency, wort will exit the first stage within 7-10 F of your entering water temperature.
Step 2 transfers the remaining heat to chilled glycol and exits at desired fermentation temperature.
Quick fact: this heat load is tremendous when compared to the other cooling loads the chiller system services. Often this will require the brewer to isolate their cellar from the cooling loop, so all of the available cooling capacity of the chiller system is dedicated to this single process.
3. Pre-chill the City Water Prior to Entering the Single-Stage Wort Heat Exchanger
This is a great lower cost option for breweries that experience a seasonal spike in city water temperatures, but the rest of the year are able to adequately cool the wort. A lower cost brazed plate stainless steel heat exchanger is used with the drawback that these welded heat exchangers can’t be opened up to clean and if they become fouled or plugged, often a new heat exchanger is needed.
4. The use of a Three-Section Heat Exchanger
This fourth scenario is actually a combination of options 2 and 3. The use of a three-section heat exchanger, or multiple individual heat exchangers, that use a combination of cold liquor, chilled glycol, and city water to cool the wort. These are typically found at breweries that brew a lot and have simply grown beyond the designed capacity of the brewhouse.
Deciding which option is best depends on several factors: average water supply temperature, your brew schedule, the styles of beers that you brew, and your future growth plans. I’d suggest talking to other brewers in your size range and in your region. Seek advice from your chiller supplier, they will be glad to help evaluate the options with you.
Glycol is used in many stages of beer making.
Glycol Cooling in the Cellar
Next in the process is fermentation. Wort is in the fermenter, the yeast is pitched, and the fermentation process begins. Using cooling jackets on the fermenter, chilled glycol enables the brewer to maintain ideal fermentation temperatures throughout the process.
For the most common Ale Style Beers, a majority of the heat of fermentation is generated quickly, when we estimate the cooling loads for a brewery we actually calculate the heat load using the assumption that all of the heat is generated in the first 72 hours of fermentation.
There are a number of formulas to calculate the heat of fermentation, we use a factor of 15 bricks per Bbl which is then multiplied by 280 BTU per brick. We divide the load across 72 hours to determine an estimated BTU/HR to determine what kind of capacity we will need from the chiller to service this step.
150 Bbls in Active Fermentation
X 15 Bricks per Bbl = 2250
2250 X 280 BTU (per brick) = 630,000 Total Heat of Fermentation
630,000 BTU divided by 72 hours = 8750 BTU/HR Cooling Load
Fermentation is complete, the next step and it is to crash cool the fermenters to final holding temperature.
Crash cooling, often the largest cooling load in the cellar, varies greatly depending on the size of the fermenters and the style of beer being produced. Brewers elect to bring the temperature down in steps, stretching the process out over several days, or favor bringing the temperature down as quickly as possible. For our load estimate calculations, we use 24 hours as our default crash cooling time period for smaller fermenters (up to about 60 Bbl). On larger vessels, simply due to product volume and limited surface area of the cooling jacket, it becomes a challenge to crash cool in 24 hours and this will stretch out to 36 or even 48 hours process.
Calculating the crash cooling load is pretty straight forward. A quick formula requires taking the mass of product that you are cooling in pounds, multiply by the temperature drop you require, and then divide it by the number of hours that you require this cooling to occur.
For example, if you are crash cooling a 60 Bbl fermenter from 68 F to 32 in 24 hours, we would calculate this load as follows:
60 Bbl = 1,860 GAL
1,860 GAL weighs approximately 16,500 lb. (8.85 lb. /GAL)
16,500 lb. X 36 F Temperature Drop (68 F – 32 F = 36 TD) = 594,000 BTU
594,000 BTU divided by 24 hours = 24,750 BTU/HR
After crash cooling, the beer is held allowing solids to drop, the beer to clarify, before being transferred to a conditioning vessel and then perhaps to packaging or serving vessels.
The conditioning cooling load is very small, we are simply keeping cold beer cold. To calculate we take the total square foot surface area of the vessel, use a factor that estimates the heat loss through the vessel insulation and factor total temperature difference between conditioned beer and the average cellar temperature.
1 EA 60 Bbl Conditioning Tank Holding at 32 F
Estimated Surface Area = 300 SF that we multiply by an insulation factor of .15
300 SF that we multiply by .15 = 45
Cellar Temperature is 80 F (estimating a worse case or a high average)
80 F – 32 F (Conditioning Temperature) = 48 F Temperature Difference between beer and cellar temperature.
48 F TD is then multiplied by the SF Factor of 45 = 2,160 BTU/HR Cooling Load
Glycol and Packaging
Packaging is often the next step. Because bottling and canning lines can be very finicky, a plate heat exchanger can be installed at the bottling/canning line. Any heat picked up during the transfer from the brite tank is removed, insuring a steady flow of beer at a consistent temperature.
Now that the beer is packaged, work doesn't stop here for the chiller system.
Cold room cooling with chilled glycol is becoming more common versus a traditional direct refrigerant based system. To be clear, using chilled glycol isn’t more efficient, at best this concept is equal, or even slightly less efficient. So why go this route? The benefits are reduced installation costs, simplified control and operation, and the elimination of an additional refrigeration system. Chilled glycol requires a larger coil surface because the glycol coil temperatures are higher than traditional refrigerant coil temperatures. Higher coil temperatures remove less air moisture from the room which allows a higher condensation factor- especially when warmer product is brought into room and pull down cooling is required of the product.
We use a program to estimate the cold box cooling load developed by a cold room box manufacture. To calculate, we take the dimensions of the room, including ceiling height, and factor if the load is simply “holding” product at temperature or a “pull down” of the product is required and needs to also be factored.
There’s numerous other cooling loads I’m omitting. I do want to mention centrifuges, which can cause a 3-4 F temperature rise in product exiting the centrifuge, this heat is then removed in the brite tank or the packaging heat exchanger. Often this load is overlooked.
Show Your Cooling and Glycol System Some Love
Your cooling and glycol system accepts that it is going to have a pretty thankless existence. It understands it will likely spend its life living behind the brewery, to have stuff stacked on and around it, or it might even live on the roof where it won’t see anyone for months at a time. Your chiller system loves it when it gets to see the maintenance technician monthly to have its glycol percentage tested, to have the pressures checked, and maybe a quick cleaning of the air cooled condenser. Unfortunately, sometimes it will need to see its Doctor, or Service Technician, and it is as disappointed as you are when this happens at 3:30 on a Friday afternoon- but your chiller system hopes these visits are rare and that you understand the more visits it receives from the maintenance department, the fewer doctor visits will be required.
Your chiller system never asks a day off and although it might spend much of its time patiently waiting for a cooling demand, when it’s called into action, it is ready to go to work during the heat of summer and through the extreme cold of winter.
Your chiller system is the most important piece of equipment in your brewery. Appreciate it for the big role it plays in the brewing process. Show it some love, and remind your maintenance technician to follow the manufacturer's preventative maintenance schedule.
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