LIQUID nitrogen seems a good place to start if you want to cool something down. If Peter Dearman, a British inventor, is correct, it might be even better than it looks. Mr Dearman is a man with a bee in his bonnet. He has dreamed, since he was 15, of making a useful motor powered by liquid nitrogen. Now, at 64, he thinks he has done it—not, as he had originally imagined, to run a car, but to run a refrigerator that promises to be more efficient and less polluting than conventional alternatives.
The Dearman engine works a bit like a steam, petrol or diesel engine. It uses heat to expand a gas (known as a working fluid), which drives a piston. The difference is that instead of starting at room temperature the working fluid ends up there, and starts instead at -196°C, the boiling point of nitrogen. That temperature change, and the expansion of the nitrogen it causes, is enough to do work equivalent to a more conventional heat engine—but not, sadly, much better than such an engine. Nitrogen engines have thus, for most of Mr Dearman’s life, been an idea looking for an application. Now, though, he thinks he has found a niche whose incumbent...
from The Economist: Science and technology http://ift.tt/1EddUQN
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