My ale brewing evolved from three gallon extract batches in the kitchen to 11 gallon all grain batches in the garage. The process has been kept simple so I can enjoy it. Wort and beer movements are minimized and are mostly powered by gravity or CO2. Cold side temperature control does have room for improvement as some styles can only be brewed well in cool weather.
Last year, I did the taste workshop for some Fear No Beer members who were preparing for the BJCP exam. We met in Mark Cherney’s Mission Viejo garage which houses more beer stuff than mine does. I spotted a small blue cube connected by two hoses to a water filled tub. Mark explained that the blue cube was an aquarium chiller used for fermentation temperature control (FTC). Wow! That’s pretty clever and the light over my head switched on.
We have dogs and I’d never heard of aquarium chillers. They are small refrigerators that cool water to keep fish or yeast happy. Some can multitask by also controlling a heater if the water gets too cold. Mark’s is a 1500 BTU/hour unit he found on EBay for $200, which was about half retail.
I spooled up on FTC by studying the usual suspects; water baths with and without aquarium chillers, foam boxes like Ken Swartz’s Son of Fermentation Chiller, refrigerators, Peltier devices and the latest homebrew toy - a glycol cooler powered by the guts of a window air conditioner.
My effort screeched to a halt when I recalled that most of the tasty fermentation products (esters, phenols and higher alcohols) are created the first day or two after pitching. To manage these compounds, I needed to be able to pitch at lower temperatures. Then, FTC could be meaningful.
There are some primitive wort cooling methods; do nothing, water or ice baths, snow banks (probably not at the beach), dilution water and sanitized ice but none can quickly cool a large volume of boiling wort. If you brew extract or small all grain batches, one of these methods might work for you.
Dave Cordrey wrote an excellent article that reviewed wort cooling basics. It’s in the Technical Information section of the club website. He discussed immersion coolers (IC) with water flowing inside copper tubing and counter flow coolers (CFC) where wort and water exchange heat inside the device. My story builds on Dave’s.
Before this project, my wort was cooled with tap water once through a small IC. After it reached 80-90°F, chilled water from a cold plate finished the job. This setup, a holdover from my five gallon batch days, couldn’t achieve low enough temperatures for 11 gal batches year round and cooled too slowly.
I learned more about cooling systems and found that each one has its own downside. Here are the big ones in my eyes:
Commercial brewers do find that CFCs meet their production needs. One benefit is that they can be used in a contained system which lowers infection risk as long as good sanitation is practiced. Even then, there’s a downside. If you ever wondered why the Randall and Torpedo had to be invented, loss of hop flavor and aroma is your answer.
For almost 90 years, commercial brewers have specified plate CFCs more often than not. These are amazingly efficient but there’s no free lunch, as discussed on a Wiki. “In HVAC and brewing applications, heat exchangers of this type are called plate and frame; when used in open loops, or with fluids that transport solids, these heat exchangers are normally gasketed to allow periodic disassembly, cleaning and inspection. There are many types of permanently bonded plate heat exchangers, such as dip-brazed and vacuum-brazed varieties, that are often specified for closed loop applications.”
Hose and tubing CFCs have been available to home brewers for at least 30 years. Therminator and Shirron plate coolers have been marketed for the last five along with others that can be found online. None of these coolers can be disassembled for cleaning and sanitizing. CFCs have some attractive features, but I’ve heard and read about too many infected batches when sealed ones are used. I think no CFC can be reliably sanitized unless it can be completely taken apart and visually inspected.
Even though cleaning and sanitizing an IC is easy, some home brewers still worry about their limitations. Recently, Jamil Zainasheff published his version of a wort recirculation/IC scheme that rivals CFCs for speed and low temperatures (ed. we have Mylo's build of Jamil's chiller right here). This is intriguing, but the possibility of HSA from energetic mixing bothers me. Perhaps a look at the science of heat transfer can lead us to quick cooling with a minimum of complications.
Boiling wort’s excess heat can be calculated with
H = M*Cp*ΔT
H equals the product of M, the wort’s mass, Cp, its specific heat and ΔT, its temperature change. My worst case is 11 gallons of 1.080 wort that weighs 100#, has a Cp of 1.05 and a ΔT of 150°F. Allowing for the heat retained by the kettle and IC, the total is 17,000 BTU in round numbers. Removing this heat in less than an hour will allow the yeasty beasties to start dining and repel unwanted guests.
The rate of heat transfer can be calculated with Q=U·A·ΔT. Q equals the product of U, the overall heat transfer coefficient, A, the area of the coil and ΔT, in this case, the average difference between the wort and coolant temperatures during the entire process. Engineers deal with this ΔT using the Log Mean Temperature Difference concept but we don’t have to go there. For our purpose, clues to quick cooling can be teased out of the terms on the right hand side of the equation.
My local tap water varies between 57 and 72°F from winter to summer. Because a ΔT is required to push heat from the wort to the coolant, some chilled water is necessary to even reach 62°F wort year round.
Changes that can speed wort cooling the most without bad compromises are:
To the right is a photo of my new coil. Some are prettier and some are uglier but coils with the same immersed area all work about the same.
I have better things to do than stir wort. Machines to do this can be found on forums like Home Brew Talk. I found a low speed gear motor, a Molon EM5R-63-1, for $25 online and assembled a stirrer from workshop scraps. The grey can in the middle of the photos is the motor and below it is the gearbox. The black box on the left holds the motor’s start/run capacitor.
One quart yeast starters and complete wort aeration allow my fermentations to show activity in 2-3 hours. I’ve rarely (knock on wood) suffered unwanted infections. Because of those experiences I mounted the stirrer on a piece of stainless that leaves the kettle top open. This allows DMS a chance to evaporate and the wort to cool a bit faster.
Other stirrer drivers that might work are:
Chilled water recirculation pump:
Jim Hilbing uses a Little Giant 5-MSPR-WG submersible pump to recirculate chilled water through the second of two CFCs in his brewery. This reliable pump has a maximum discharge of 20 gpm, a shut off head of 26 feet and retails for about $100. I shopped around to look at the competition. All the big box and hardware stores carry submersible (they are also called utility, pond or sump) pumps with similar specs. Harbor Freight was the cheapest at $40 for their Pacific Hydrostar model 98342. Most of Harbor Freight’s stuff is crap in my eyes but I’ll roll the dice on a pump that may only run 12 hours a year. Here’s a photo of the 98342.
I think I’m on the right track. The real test will come next summer when tap water temperatures peak again. I’ll buy plenty of ice and update test results then.
When I reported on my new wort cooling build in the Strand Brewers' Club newsletter, The Dregs, I promised an update when the weather and tap water warmed up. On July 5, I brewed 11 gallons of Saison and cooled it from boiling to 68F in 35 minutes. 80F was reached with 72F tap water in 25 minutes and recirculated ice water did the rest of the work. This compares to a cooling time of 28 minutes for the same length brew in January when the tap water temperature was 57F.
An IC can cool 11 gallon ale batches to optimum pitching temperatures in much less than an hour. Key points are:
Brewery upgrades are never finished. Even faster cooling is possible by:
Improved FTC is my next project.
Thanks to Ron Cooper and Jim Hilbing for sharing their expertise and historical tap water temperature data.