Self-cooling beer keg

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A self-cooling beer keg is a beer keg that cools itself using evaporative cooling. It works on the principle of an adsorption chiller .

Working principle

Construction of a self-cooling beer keg

In a special beer barrel, the barrel (A) filled with beer is surrounded by an absorbent layer, e.g. B. cotton wool (B) soaked with water. Around this layer there is a second layer (C) which contains an activated zeolite or molecular sieve . Layers (B) and (C) are evacuated . Layer (B), however, still has at least a pressure that roughly corresponds to the vapor pressure of water , since it must be in liquid form. Layer (C) should be evacuated as well as possible.

If a connection is now created between (B) and (C) by opening a valve, the pressure in (B) drops suddenly (pressure equalization), which causes it to fall below the vapor pressure of water, whereupon it evaporates from (B) . The resulting water vapor is adsorbed again by the zeolite in (C) , which means that an equilibrium cannot be established immediately and the pressure remains below the vapor pressure of the water, which enables further evaporation. Since water vapor has about a thousand times greater volume than water, a large amount must be adsorbed in order to have enough evaporation for an effective cooling effect. While the zeolite binds (adsorbs) the water vapor, it heats up, so you can directly feel from where to where the energy is transported (from (B) to (C)). The energy that the water needs to pass from the liquid to the vapor phase must be extracted from the beer in the form of heat inside the keg bubble (A) (i.e. from (A) to (B)), because only here does it exist sufficient thermal contact. The zeolite, which heats up, is thermally insulated from it. The effect is strong enough that some of the water in (B) can even freeze.

By heating the keg in the brewery , the process is reversible , since molecular sieves are less able to hold the bound substance (here water) at higher temperatures than at low temperatures. The heating must not happen too quickly, however, since otherwise the molecular sieve will age too much or be completely destroyed. Then layer (B) can be supplied with water again, (B) easily evacuated and (C) well evacuated, so that the barrel (A) filled with beer can then be cooled again by turning a lever.

Invention and application

The self-cooling by evaporative cooling beer keg was invented by Peter Maier-Laxhuber, who in 1983 at the Technical University of Munich with the topic of sorption heat pumps and sorption with the substance pair zeolite - H 2 O in physics doctorate . Maier-Laxhuber founded Zeo-Tech GmbH based in Unterschleißheim , which he runs together with Carl Christian von Weizsäcker . Maier-Laxhuber and his company hold numerous patents for evaporative cooling in Europe and the USA and are developing the technology for other areas of application.

For the cooling of beer kegs, Zeo-Tech GmbH granted a worldwide license for the technology to Cool System Bev GmbH in Fürth in 1999 . Initially, Cool System had outsourced production, but set up its own production facility in Burkau, Saxony, and has been manufacturing there since May 2003. The pilot customer for the self-cooling keg sold under the registered trademark CoolKeg was Tucher Bräu .

literature

Individual evidence

  1. ↑ Peter K. Maier-Laxhuber, b. Maier: sorption heat pumps and sorption with the pair of substances zeolite - H 2 O . Technical University of Munich, Munich 1983. (Dissertation at the Faculty of Physics)
  2. ↑ ZEO-TECH Zeolith-Technologie GmbH , Unterschleißheim. (Munich District Court, HRB 85534)
  3. ↑ Inventor = Peter Maier-Laxhuber at the DPMA, more than 200 patents.
  4. ↑ For example, US Patent 7726139 , see References.
  5. ^ Cool-System Bev. GmbH , Nuremberg (Nuremberg District Court, HRB 16169)
  6. ↑ The self-cooling barrel . In: Beverage Industry , No. 6/2003, ISSN  0016-9323 , pp. 35-37.