What is the primary refrigerant that keeps beer chilled in the trunk line?

The primary refrigerant that keeps beer chilled in the trunk line is indeed glycol. This is due to its efficiency and effectiveness in maintaining a stable temperature in the draft beer system. Glycol is used in a closed-loop system that circulates between the chiller and the trunk lines, which are the long lines connecting the keg and the tap.

Glycol has a much lower freezing point than water and provides better cooling capabilities. It can absorb and maintain cold temperatures without freezing, which is crucial for ensuring that the beer is served at the optimal temperature. The use of glycol also minimizes the risk of temperature fluctuations that could negatively impact the taste and quality of the beer being dispensed.

While air and water are sometimes used in some systems for cooling purposes, they do not offer the same level of temperature control as glycol. Propylene glycol, while similar in function, is often subjected to more specific applications, primarily in food-grade scenarios due to its lower toxicity levels. In the context of beer cooling in draft systems, glycol remains the standard refrigerant for effective thermal regulation.