Tuesday, April 15, 2008

DEVICEHYPE: The Jet-Powered Beer Cooler

This is something that was published many years ago, but it's still well worth a read.

Imagine creating your own jet engine out of spare car parts. Impressive enough, but what would one do with such a device?

Well, as the author explains, one can use it to cool beer quickly. Think of a microwave in reverse (that analogy works only in the sense of how fast it works, not how it accomplishes the goal). Why is this so? Well, a jet engine uses a lot of fuel - propane in this case. Using a lot of fuel out of a propane tank in a short period of time will cool the tank rapidly, due to the ideal gas law (PV = nRT). Basically, if you decrease the volume of a gas (V) while maintaining the same pressure (P), the temperature (T) of the remaining gas has to drop (n and R are constants).

For a science lesson, follow the Wikipedia links above. For a great diversion, read all about the Jet-Powered Beer Cooler.
In New Zealand there are two things that are the essence of being a 'good Kiwi bloke'. These are of course playing rugby and having a shed.

Not being built for playing rugby I have had to go with the shed. I may not know a rugby hoop from a cricket stick but I know my shed like the head of my hammer. A shed is a place where a kiwi bloke spends much of his time alone surrounded by his tools, current and past half finished projects and the collection of parts and material usually referred to by others (typically wives/girlfriends) as 'that pile of junk'.


Unfortunately [a] small quantity of ice would not keep multiple beers cold during the course of a day in the shed. And no, you cannot, not under any circumstances, put ice into the beer. No!

It was obvious I had to come up with a better solution to the problem.

I knew from some long forgotten physics lecture that when a liquid expands into a gas it will draw heat from its surroundings. And I happened to have a source of a suitable liquid right in my shed in the form of a LPG cylinder (liquid petroleum gas). Obviously it would not do to evaporate vast quantities of a flammable gas into the closed confines of my garage. That would probably be dangerous. What I needed was a way to remove the dangerous gas. The solution was obvious. The gas is flammable so why not burn it. Burning the gas with a normal burner would not use up the gas fast enough to give me any serious cooling. What I needed was a way to use up a lot of fuel very, very quickly.

What I needed was a jet engine!
Gotta love those Kiwis!

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