Heating and chilling methods for the 5BBL BIAC
The BREWHA BIAC system is an advanced, innovative brewing system that combines boiling and fermenting into one single vessel. Brew days are therefore simpler and more enjoyable, and the heat of the boil sanitizes the fermenter, giving peace of mind that a microbial infection or residual chemical sanitizers won’t spoil the beer.
When brewing, once the boil is complete, wort is chilled before the yeast is pitched. While yeast won’t be killed unless pitched above 60°C/140°F, if the temperature of the yeast prior to pitching is significantly different from the temperature in the fermenter it can be shocked, resulting in less than optimal fermentation rates.
While other methods can be employed, in the BIAC brewing system, hot wort is normally chilled by chillant (ie. water or a water/refrigerant mix) being fed into the wall cavity/jacket of the fermenter. As the chillant rises up through the jacket, it removes heat from the wort through the fermenter wall. This makes it a very sanitary chilling system as the vessel has been completely sanitized by the boil and the wort never leaves the vessel it was boiled in. There is virtually ZERO RISK of contamination from hoses, connections, valves, plate chillers, incompletely sanitized fermenters etc. like in traditional systems where the wort passes from the boil kettle through the chilling apparatus on its way to the fermenter.
There has been some discussion online about the benefit of circulating wort inside the BIAC fermenter during chilling to reduce the chill time so we put it to the test in our largest system, the 5BBL BIAC. We tested on the 5BBL, since being the largest system we currently offer, it has the lowest chilling surface area to wort ratio and therefore (all other factors being equal) the longest chill time of the BIAC systems.
The 5BBL fermenter was filled with 600L of water, heated to boiling, and the time recorded to see how quickly it would chill down to 27°C/80°F using Vancouver’s municipal water (which on that particular day was 7°C/45°F). The chilling water for the test had a constant flow rate, consistent temperature and the only thing changed was whether or not the pump was circulating water internally during the chill. The temperature was measured both at the top of the fermenter with a probe hung over the top, and at the fermenter sensor port near the bottom of the fermenter.
The first chart ('Chart 1') shows the chill curve with the pump circulating, and the second chart ('Chart 2') shows it without. The test demonstrated a few things. First, the actual rate of chilling was almost neglible between the two, suggesting that the fermenter is a relatively efficient chiller as is, and circulating the wort during chill does not reduce chilling time significantly. Second, if the wort is not circulated during the chill, there is a significant temperature stratification inside the fermenter, with the water/wort at the top of the fermenter being much warmer than the bottom. However, when gas (air) was introduced into the bottom of the fermenter for less than a minute (at 90 minutes, much the same as would occur through aeration prior to pitching yeast) the bubbling action inside the fermenter caused by the rising gas bubbles, broke the temperature stratification and neutralized the temperature difference almost immediately.
One conclusion from this study, is that if a brewer chooses to not circulate during the boil, they should aerate prior to pitching yeast, to agitate the wort and ensure that the temperature sensor shows a true averaged temperature inside the fermenter, not just the temperature of the wort near the bottom. (Choosing not to circulate during chill can be beneficial in that it allows the wort proteins to settle to the bottom of the fermenter where it can be removed prior to aeration.)
While a chill period under an hour is generally preferred, many brewers attest that a slightly longer period does not have negative effects, as long as sanitary conditions are maintained. If desired, chilling time can be reduced by reducing the chillant temperature. Since an increased temperature differential reduces chill times, colder chillant reduces chill times (which is why glycol, which freezes at temperatures much below that of water, is often mixed with water to reduce its freezing point). Chill times can also be reduced by increasing the rate of flow of chillant (this is really just a corollary of the first method, as by increasing the rate of flow, the chillant has less residence time and therefore prevented from heated as much and has a lower temperature).
To prove this, we ran a third test, identical to the first test, with the only variable changed was increasing the flow volume of water from 25L/minute to 35L/minute. As expected, the increased flow rate chilled the water quicker, about 10% faster (see 'Chart 3'). We would expect that this increase follows the law of diminishing returns (increasing the flow rate even further, would not see the same time reduction ratio), just as a reduction of flow volume below 25L/min would not see a linear increase in chill period. From this result we would predict that a lower chillant temperature would show a similar reduction in chill time, so with a reduced but sufficient flow rate, and sub zero chillant temperature, chill times under an hour could be achieved.
Note: Some customers are reporting that they are using a plate chiller to help reduce chilling time. They are cycling boiling wort through the plate chiller (out the fermenter, through plate chiller and back into the fermenter) during the boil to sanitize it, then using it to help chill the wort (in addition to using the jacket) after boiling is complete.