The patent. US 8,080, "Improved process for the artificial production of ice", granted 6 May 1851 to John Gorrie of New Orleans, Louisiana — though he practised in Apalachicola, Florida. It is the first United States patent for mechanical refrigeration. Gorrie was a physician who believed, incorrectly, that malaria and yellow fever were caused by hot damp air; he built cooling machines to chill sickrooms, and the ice was a by-product of that goal. The medical theory was wrong and the machine was right.

The thermodynamics. Compressing a gas does work on it and raises its temperature. If that heat is then removed to the surroundings while the gas is still compressed, the gas has lost energy it cannot recover. Allowing it to expand — particularly against a piston, so it does work on the way out — drops it well below its starting temperature. This is the air-cycle or reverse-Brayton refrigeration cycle. The essential insight is that a refrigerator does not destroy heat; it moves heat from a cold place to a warm one, and the compressor work is the price of moving it uphill.

Why against a piston and not just a valve. Venting compressed gas through a restriction cools it too — the Joule-Thomson effect — but expanding it against a load extracts far more energy and gives a much larger temperature drop. Gorrie's patent specifies expansion through an engine for exactly this reason, and the same distinction separates a turboexpander from a throttle valve in modern plant.

He was destroyed commercially. The natural-ice industry was large, entrenched and hostile; the New York Globe reportedly mocked "a crank down in Apalachicola, Florida, that thinks he can make ice by his machine as good as God Almighty". Gorrie's financial backer died, he failed to raise more capital, and he died in 1855 having sold no machines. Air-cycle refrigeration was later superseded for most uses by vapour-compression systems, which are far more efficient because they exploit latent heat of vaporisation rather than the sensible heat of a gas — but it survives today in aircraft air-conditioning packs, where the compressed air is free from the engines and there is no refrigerant to carry. Florida placed a statue of Gorrie in the United States Capitol.

Heating & Cooling

Blueprints (2)

Gorrie Ice Machine

Apparatus for Treating Air