The Invention of Mechanical Refrigeration
- Wednesday, July 09, 2008
Scientists understood that heat was a form of energy. The more energy something had, the more heat it generated. In order for something to become cold, it must lose some of its energy. Refrigeration, as it turns out, is not a matter of creating cold, but rather of taking away heat. It is a thermodynamic process. The heat moves from one object to another. The first object gets colder, while the second object gets hotter.
God built a refrigeration system into each one of us. It’s called “sweat.” When we sweat, beads of perspiration build up on our bodies. Here’s the ingenious part: When the sweat evaporates off of our skin, it causes heat to transfer from our bodies into the atmosphere! Sweating is a thermodynamic process.
Scientists began experimenting with ways to control evaporation. They learned that there were some materials that, when properly controlled, could move a lot of heat, resulting in a lot of cooling. This led to early refrigerating devices. A classic example, which was used into the early 1900s and still shows up on occasion at flea markets, is called the “Icy Ball.”
The Icy Ball was invented in the early 20th century as an affordable refrigeration system for the average household. It used two metal spheres connected by an inverted, U-shaped metal tube. One of the spheres was called the “cold” side, and the other was called the “hot” side. The Icy Ball worked on a principle known as “gas-absorption.” It had no moving parts and required no electricity! Here’s how it worked.
The Icy Ball had to be regenerated once every 24 hours. This means it had to be “charged” so it could operate. The cold side sphere was filled with pure liquid ammonia. The hot side was filled with pure water. Ammonia vapor would fill the inverted U-tube. The liquid water on the hot side liked to absorb ammonia vapor. As it absorbed the vapor, the pressure in the tube decreased. This caused the pure liquid ammonia on the cold side to start to evaporate.
As it evaporated, the temperature would drop. In operation, it would drop to as low as 19º F. The hot side would start heating up—but this had to be controlled. If the hot side got too hot, it would quit absorbing the ammonia vapor, and the refrigerator would stop working. To remedy this, metal cooling fins were welded on the hot side sphere. This allowed air in the room to cool the hot side so it could continue to absorb ammonia vapor, thereby keeping the refrigeration process running.
The Icy Ball, once regenerated, would be lifted into place so that the cold side sat inside a chest, much like an ice chest. This refrigeration action kept the inside of the chest cold, making it a refrigerator.
Some very good pictures of this, including an exhibit of the Crosley Icy Ball at the Smithsonian Institute, can be seen at http://crosleyautoclub.com/IcyBall/crosley_icyball.html.
As people began to try to improve refrigeration systems, they tried a number of different materials in addition to ammonia. These included methyl formate, methyl chloride, and sulfur dioxide. But there was a problem: These materials were all hazardous. As refrigerators began to develop into household appliances, accidents occurred. Some refrigerators would spring leaks in the cooling system and release the chemicals into the home. People were killed by methyl chloride poisoning into the early 1900s. To solve this problem, scientists at DuPont invented a chemical called Freon. Freon made an excellent refrigerant, and it was safe to people if it was accidentally released. Years later, it would be hypothesized that Freon was damaging the earth’s ozone layer, resulting in the elimination of Freon as a refrigerant.
The World After Mechanical Refrigeration
As the demand for refrigeration grew, new methods and techniques were developed to continue to improve upon the systems. The two main types of refrigeration systems used today are the vapor cycle and the gas cycle systems. The refrigerators we have in our homes are vapor cycle systems. They work in a manner very similar to the Icy Ball, except that motors inside our refrigerators keep the process running so that we don’t have to regenerate the vapor. It is a cycle, meaning it repeats itself. The liquid evaporates, creating cooling, and is then compressed and condensed back into a liquid. It cycles back around and evaporates again, creating more cooling.
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