American Chillers and Cooling Tower Systems

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How To Size A Brewery Chiller

Wondering how to size a brewery chiller? Here is a step by step guide. Read every word or just follow the examples. If you need help, our sales engineers will be happy to assist you.

Calculate The Pull Down Loads (Crashing)
Pull down occurs when you are dropping the temperature (i.e. pulling down the temperature) of your vessel and (other than wort cold crash) is typically the largest influence on the sizing of the chiller. You will need to know the size of your tanks, temperature differential and how long you have to achieve your desired temperature.

1. Calculate the volume in gallons of your tanks
A. 1 bbl = 31 gallons so a 7 bbl tank = 217 gallons

Example: Let’s assume we have three, 7 bbl tanks.
217 x 3 = 651 gallons

2. Multiply the total gallons by 8.33 to get total pounds
Example: 651 gallons x 8.33 = 5,422.83 pounds

3. Multiply the total pounds by your temperature difference
A. Commonly that is 75F degrees minus 34F degrees or 41F degrees
Example: 5,422.83 pounds x 41 = 222,336.03 total Btu

4. Divide by the hours of your pull down (crash).
Example: 222,336 / 24 hours = 9,347.33 Btu/hr
If your pull down time is 12 hours, you would need 18,528 Btu/hr.
222,336 / 12 = 18,528 Btu/hr

This is the Btu/hr required for your pull down process. Many brewers will
add 10% or 15% to this number to compensate for extra heat being added
by the pumps, heat loss and inefficiencies of their systems.

II. Calculate heat load for active fermentation

1. Multiply the total bbl’s by 15 bricks.
Example: 21 Bbls x 15 = 315

2. Multiply by 280 Btu / brick
Example: 315 bricks x 280 Btu = 88,200 Btu

3. Divide by 70 hours
A. 70 hours is the typical time frame that most of the heat gain from the yeast occurs, even if/when the fermentation period is more than 75 hours.
Example: 88,200 / 70 = 1,260 Btu/hr.

III.  Add the pull down load and the active fermentation load together for your total Btu/hr load

Example: 18,258 Btu/hr plus 1,260 Btu/hr = 19,518 Btu/hr

IV. Apples VS Apples
In the above example you will need a chiller capable of providing a minimum of 19,518 Btu/hr @ 28F Leaving Glycol Temp.

1. Make sure that the chiller your are purchasing is sized properly. In our example, our chiller needs to be able to provide 19,518 Btu/hr @ 28F Leaving Glycol Temp. Chillers in the US are sized by either tonnage or horsepower. In either case, you want to make sure that the chiller also factors in your glycol percentage. Typical glycol percentages are 30% to 40% glycol to water depending on your lowest outdoor air temperature where you live or 28F degrees (whichever is lowest). Propylene glycol will require more surface area in the heat exchanger than will water.

NOT ALL CHILLERS ARE CREATED EQUAL
You don’t need to know all of the details that are explained in this paragraph, if you remember that all chillers are not equal and know to ask for a chiller that is capable of cooling your Btu/hr load down to 28F leaving glycol temp. or whatever your coldest chilled fluid temperature that you will need for your process. If you are a detail person and want to know more, please read on!

Chiller capacities are based upon many factors. The major factors are fluid temperatures, ambient air conditions, fluid being cooled and compressor performance data. A refrigeration ton = 12,000 Btu/hr. Many chillers are rated for air-conditioning standards, which are 44F leaving fluid temp. / 54F entering temp. and 2.4 gallons per minute per ton. A brewery chiller will need more horsepower than an air-conditioning chiller. In fact, an air-conditioning chiller may not operate properly or may not operate for very long due for a brewery due to the lower temperature required for a brewery. Operating at lower temperatures than what the chiller is designed for can also cause the compressor to fail prematurely. American Chillers engineers its brewery chillers to perform at brewery conditions. When ordering, we ask for your conditions to make sure the chillers are sized and engineered accordingly.

In our sizing example above, at a quick glance, it would appear that a 2 ton chiller would be sufficient (2 x 12,000 Btu/hr = 24,000 Btu/hr). BUT, we need to know the design standards of the chiller. The cooler the fluid, the more compressor horsepower and the larger the evaporator (heat exchanger) required. The evaporator will also need to be larger when cooling glycol VS cooling water. In air-conditioning, where 44F is the desired fluid temperature, glycol may not be needed (especially if the air-conditioning chiller is being installed in a warm climate).

Make sure that you are calculating your worse case scenario based on the amount of brewing that will take place simultaneously. This is the time to consider any plans for future growth. If that growth is in the near future, it may be beneficial to oversize the chiller now so that you aren’t forced to purchase additional equipment later. Of course, if your planned growth is substantial or you are over sizing the chiller by a great amount, you could have adverse results if some sort of capacity control isn’t built into the chiller. If your growth is more than 2 years out, you may be better off to purchase a smaller chiller now and add additional modules later.

As you can see, there are many factors to consider when purchasing a chiller, but with the proper engineering of your system, your brewery chiller should last for many years. If you need help sizing your brewery chiller, please contact a sales representative at American Chillers & Cooling Tower Systems, Inc. We are happy to assist you.

Cheers & Happy Brewing!