Chill Out!

Part 1 - Terminology

Reprinted by permission from Norm Pyle, Rob Brown, and Tom Williams

Several postings have been made on the Home Brewers’ Digest about heat exchangers. This is a compilation of postings covering quirks of terminology. Part 2 will deal with thermodynamics.

Norm Pyle of Longmont, Colorado writes, "I've wondered about our terminology of chillers for a while. I believe we're limiting ourselves quite a bit by classifying chillers as "immersion" or "counter-flow". It seems they are being classified by what happens to the coolant, rather than what happens to the wort (the coil containing coolant is immersed, or the coolant is pushed in a counter-flow around the wort). Isn't what happens to the wort the most important?

There are many chiller. I think it is more important from a brewer's point of view to talk about what happens to the wort, and maybe use names like "bulk" and "incremental" chillers. The distinction is that the former cools the entire wort at once, while the latter cools only small increments at a time.

For example, a friend of mine uses an immersion chiller, but the chiller is immersed in ice-water, not wort, and the coolant is only moved around by stirring every once in a while. The wort flows through the chiller, but it is in no way a "counter-flow" (CF) chiller. This is an incremental chiller immersed in ice-water. It has much more in common with a CF chiller than an immersion chiller, but its construction and use is more akin to the immersion. It is most definitely an incremental chiller though, as the wort is cooled a little bit at a time.

What might be more important is whether or not the chiller is "off-line" or "in-line" with the wort flow. The distinction I'm trying to make is that in one case, the cold-break is left behind in the kettle and in the other it is carried into the fermenter. Subsequent process steps (another racking, for example) can remove this cold-break of course, but the chiller doesn't.

For those of you who are considering building or buying chillers, you should consider a few trade-offs. Bulk (off-line) chillers are good for leaving cold break behind in the kettle (both chillers leave hot-break behind). I believe the literature is clear that leaving hot-break behind is desirable, but there is considerable debate over whether cold-break removal is necessary or desirable. Bulk chillers are easier to clean, as only the outside is exposed to wort. They are easy to sanitize as well - just dunking them in the boiling wort for a few minutes prior to chilling is sufficient.

Incremental (in-line) chillers have the advantage of quick chilling without the necessity of stirring the wort to help their efficiency. They allow the use of a hop-back to pass hot wort across fresh hops just before it is chilled. This gives the ultimate finish hopping effect, as the hop compounds are at elevated temperature for only a short time and then are returned to room temperature. Bulk chillers don't allow this, as the wort is already cooled before leaving the kettle. Cleaning and sanitizing in-line chillers must be done with chemicals, as they cannot be scrubbed on the inside where the wort passes. Since they cool only a small portion of the wort at once, the chilling is quicker, and better cold-break is said to be achieved. They are also more difficult to construct."

Rob Brown of Guelph, Ontario, Canada acknowledges the cross-over between equipment and usage. "The biggest confusion seems to be with the pot chiller and the bucket chiller, as they are the same thing used differently." "It is probably impractical to set up a systematic nomenclature incorporating all aspects [of chilling] but describing the actual chiller body is a solid start."

In-line chillers (incremental) include counter flow chiller - garden hose type, chamber counter flow, bucket immersion, and plate chiller (uncommon for homebrewers). [Also uncommon but possible is the fan-cooled radiator-type just like in your car.]

Bulk chillers include pot immersion [stirred or not], [chilled/frozen additives], and dump (or "through-the-air-cooled") chilling.

Coolants have a variety of forms: tap water, ice water bath, recirculating ice bath for in-line chillers, and [physical heat loss] coolants such as a pump or gravity fed tube.

Tom Williams of Norcross, Georgia provides the terminology from industrial usage. "‘Counterflow’ is one of three terms which generally describe heat exchanger configuration, the other two being ‘crossflow’ and ‘parallel flow’. Counterflow is the more common configuration because it allows the greatest change in fluid temperature for a given set of inlet conditions. These terms refer to the relative movement of the two fluids which exchange heat, and imply forced flow in both fluids. I have never heard any of the three terms applied to what Norm refers to as a "bulk" cooler. Perhaps "forced flow" might be a better term than "incremental" for the type of chiller in which wort flows through tubing. I agree with Norm that what is happening with the wort should be used to name the cooler, which would result in the "wort-flowing-through-tubing-immersed-in-ice" chiller being called a forced-flow chiller as well."

Tom wraps up the discussion of terminology by asking a very practical question. "While I am now a chiller user, I am still unsure of the technical reasons for using them. To me, the reduction in time alone is worth it, but what does rapid cooling do for the flavor of the beer? I recall someone stating that the two biggest improvements that a beginner can make are switching to liquid yeast and using a chiller. I have done both, but really, what have I done?"