They used to sit on top of counters in stores, and they were normally filled with orange juice, and a stirring arm rotated very slowly. I believe that the motion of the liquid created some kind of cooling effect. Can anyone confirm this and explain how? And what were they called?

They used to sit on top of counters in stores, and they were normally filled with orange juice, and a stirring arm rotated very slowly. I believe that the motion of the liquid created some kind of cooling effect. Can anyone confirm this and explain how? And what were they called?

Stirring a liquid - in the absence of other effects - will actually warm it; it was using huge falling mass mechanical stirrers that Joule proved transformation of one form of energy (gravitational) went through another (mechanical) to heat energy. There must be something more to the machines - perhaps a radiator somewhere external.

 

http://en.wikipedia.org/wiki/James_Prescott_Joule

This is just a guess, but rather than trying to cool a large volume all at once one obvious solution is to send a small amount through a compact chiller and then mix the cold liquid in with the rest. That's how I assume these work — there's a cooling unit and pump in the base.

Or, alternatively, the stirring was just to keep the juice from settling and any cooling the device did was separate from the stirring mechanism.

Or, alternatively, the stirring was just to keep the juice from settling and any cooling the device did was separate from the stirring mechanism.

This, and to mix the flavor syrup evenly through the drink, so you don't end up with syrup in one spot.

Or, alternatively

Or both (or all three)

When I worked in a bar (a long time ago) the apparent purpose of these items was to culture microorganisms on the workings which are almost impossible to keep clean.

The given reason was to keep the juice stirred and cooled,