calandria

A calandria is a tube or bundle of tubes positioned inside a brew kettle or similar vessel, through which steam or hot water circulates to heat the contents. Unlike direct flame or an external jacket, the calandria keeps the heating medium separate from the liquid being heated, allowing precise temperature control and preventing scorching of temperature-sensitive materials. The term is borrowed from the sugar and paper industries, where similar devices have been used for over a century.

In a typical brewery setup, steam enters the calandria at the bottom and exits at the top, creating a thermosiphon effect that improves heat transfer and circulation. The tubes are usually made from copper or stainless steel, chosen for their thermal conductivity and resistance to corrosion. A single kettle might contain a calandria with 10 to 30 meters of tubing, depending on the vessel size and desired heating rate. The calandria is submerged in the liquid to be heated, so its surface area directly contacts the wort, mash, or other brew medium.

Design variants exist based on application. Some calandrias use a single large-diameter tube coiled in a helix; others bundle several smaller tubes in parallel. The diameter typically ranges from 25 to 50 millimeters. The depth of immersion and the pitch of any coil affect heating efficiency. A calandria must be removable for cleaning, since mineral deposits and protein buildup reduce heat transfer and can block condensate return lines.

Common problems arise from three sources. Steam side corrosion or caustic attack degrades tube walls if water quality is poor or if caustic cleaning solutions contact the calandria directly. Liquid side fouling reduces performance and makes removal and descaling necessary. Condensate backup, caused by kinks in the return line or a plugged condensate trap, causes hammer and can rupture thin-walled tubes.

The calandria occupies a middle ground between slow indirect heating (an external jacket) and fast direct heating (flame or immersion heaters). It suits processes where heating rate matters but product quality demands gentle, even heat distribution. Breweries favor it because it maintains flavor profiles during rest steps and allows repeatable mash infusion schedules. Food and pharmaceutical manufacturing similarly rely on calandrias for batch heating without hot spots.