In the days when humans were hunter-gatherers, subsistence consumption was the only known method of gathering food. There was no technology for storing anything for long periods of time, so people were forced to scavenge or collect only what they could eat right away. With the advent of civilizations, the focus of many people has led to the creation of dedicated farming classes that can support people who spend their extra spare time thinking of ways to solve problems like this. The solution to this problem will eventually become our modern cooling systems.
Early cooling systems were simple pits lined with ice and snow, then covered with straw for insulation. Many cultures have come up with ingenious ways to combat food spoilage, but the most impressive solution to this problem is one engineered by the ancient Persians around 500 BC. This civilization built large domed structures called “yahkchals” that preserved ice to a temperature equivalent to that of modern refrigerators. This is a clear case of necessity being the mother of invention, as the Persians required large amounts of ice to preserve food in and around the deserts in which they lived. These yahkchals were engineering masterpieces, yet they were surprisingly simple. They achieved what they did simply by constructing these buildings with thick walls made of a flexible, water-tight mortar known as sarooj. This material was made from sand, clay, animal hair, eggs, and other materials in specific proportions, and produced a very thick material that could be incorporated into an efficient cooling system because of the sarooj’s resistance to heat transfer. While food preservation was essential, yahkchals were also used to preserve luxury foods for the Persian royal family as they were often the wealthiest people with the largest and most numerous refrigeration systems.
During the European Industrial Revolution, modern refrigeration systems that used gas pressure to preserve food over long distances began to be built. This led to a paradigm shift in shipping that opened up an entire industry when people realized that food could be transported from any part of the world to another. This movement began in New Zealand when in 1881 a large merchant ship called Dunedin was fitted with a large cold storage unit to transport frozen meat to Great Britain. Despite the enormous distance, this early foothold in what would quickly become a huge industry ensured that New Zealand would dominate England’s meat-shipping business for a hundred years. This method would not have worked with ordinary ice storage because merchant ships could not provide the same stable conditions as the Persian yahkchal. Gas pressure has become the wave of the future.
Almost all modern refrigerators today use gas compression technology. Over the past 100 years, many innovative steps have been taken in improving the technology of cooling systems that have generally caused quantum leaps by allowing new modes of transport, such as trucks and aircraft, to be cooled. The final quantum leap resulted in safer chemicals that allowed commercial refrigerators to be found in smaller spaces such as homes across the United States.
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