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A Brief History of Evaporative Cooling 07/08/2014

When you look up at an evaporative cooling plant that’s whirring away and providing fresh cool air to a building or factory, it’s hard to believe that the basic technology has been around for centuries.

The phenomenon of the evaporative cooling effect has been known about since at least ancient Egyptian times. According to archaeologists, there are frescoes in Egyptian temples dated at over 4,500 years old showing servants fanning pots of water to cool their royal masters.

It’s clear from these wall decorations that not only was the cooling effect of water known about, but the idea was important enough to display on the wall of a temple.

Further discoveries from ancient Egypt show buildings specifically designed to take advantage of evaporative cooling to escape from the heat of the North African sun. Such features as porous water containers, ponds and narrow rills of water were designed in such a way that their use was unambiguous – that use being to cool the surrounding air.

Like many great ideas of the ancient civilisations, the idea of evaporative cooling was lost for many centuries, and it wasn’t until relatively modern times that they were effectively re-discovered.

It was – almost inevitably – the colossal mind of Leonardo da Vinci that was credited with the first steps toward the technology as we know it today. He’s credited with being the inventor of an early mechanical air cooler, which was essentially a kind of water wheel which guided cool air into a room. Air was cooled by what is now known as evaporative cooling as the air passed over the wheel.

As the age’s great thinkers emerged, the properties of both gases and liquids began to be more readily understood. Both Pascal and Boyle devised physical laws that explained how liquids and gases behave, Boyle’s Law being an important one in the air conditioning industry as it governs the flow of and volume of air under pressure.

With fluid dynamics also being explained, Dalton was able to show the nature of evaporation, and how it is linked to the global cycle. On a smaller scale, it explains how liquids evaporate and act as a cooling agent in air.

While the first coolers based on these ideas were small scale, it was not long before greater industrialisation led to calls for up-scaling of these devices. That led to the explosion of the cooling industry that you see now – both through refrigerants and evaporative water-cooled systems. It’s been a few thousand years, but we got there in the end.

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