History of Refrigerants

The concept of mechanical refrigeration starts back in the 1750s. Researchers knew nothing about cooling except that pressure and gasses somehow played a key roll in absorbing and removing heat. In these early days, everything was tried as a refrigerant: ammonia, alcohol, air, carbon dioxide, and more. It was the days of trial and error to create the robust understanding of physics and chemistry we have today.   Low Temperature Boiling The first experiments in refrigeration used Ether and Alcohol, which are readily evaporated. At sea level, Ether boils at 94F and Alcohol can boil as low as 151F, depending on the exact chemical form. Sea level is important here, as pressure changes the boiling point. Lowering the pressure causes a decrease in the boiling point. These gasses with low boiling points were ideal for early experiments. The first experiments used vacuum chambers and potentially some custom hardware. There isn’t a lot needed to build a basic vacuum chamber. A jar with a good seal, a hose, and a pump can create a vacuum. An observable refrigeration can be done with almost no special equipment at all. At this scale, cooling was possible, but not feasible. Alcohol, Ether, and other chemicals were common and easy to acquire, but no one was going to put a chunk of meat in a vacuum chamber, cover it in alcohol, wait for it to freeze, and try to store it somewhere. There had to […]

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Why is the AC Hissing?

Air conditioners produce liquid water by design and by the simple nature of physics. Sometimes this harmlessly leaks out around the air conditioner, such as with window units, and sometimes it leaks when a drain gets blocked. There is however, a second leak an air conditioner can develop: refrigerant leaks.   The Cooling Compound Air conditioners work by exploiting physics around state-changes. When liquid turns into a gas, it can absorb heat.The effectiveness of the state change varies from compound to compound. For air conditioning, we tend to use things like R134a (freon), R12 (phased out/illegal in much of the world now), and even propane. These are all chemicals which have particular properties ideal for cooling. For example, they won’t turn solid at 0 degrees C like water, so they won’t clog up the air conditioner’s tubing and fittings. These chemicals though have some downsides we can’t really escape. Propane is outright flammable and probably capable of turning your air conditioner into a flaming set piece in the next post-apocalypse movie. R12 destroys the ozone. And R134a is toxic. It causes a wide range of symptoms from headaches to hallucinations and death in the worst case exposures.   The Hissing Leak When the air conditioner is running or has recently been run, the refrigerant will be highly pressurized. In order for us to make it work, we compress it. We’re cramming a lot of material into a small space, which […]

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What About the Other Compressors?

Just how many ways are there to squeeze down a gas? If you look at the entirety of the industrial world, there’s probably a few hundred different devices. If you look at HVAC, luckily the list is a lot shorter. The air conditioning world relies primarily on five compressor designs.   Reciprocating This compressor works pretty much exactly the same as a car engine does, but without the gasoline and combustion. Inside a car you have your cylinders and pistons. When the piston moves up it compresses, when it goes down it sucks. The same principal is used in a reciprocating compressor. At the base of the compressor there will generally be an electric motor, which turns a shaft. The shaft has a bend in it to allow for offset motion. At the bend there’s a connecting rod, which links the shaft to the piston. When the shaft spins, the piston moves up and down. On the downstroke, fresh refrigerant is pulled in. On the up stroke the refrigerant is compressed and injected into the refrigerant loop. This particular design is popular in residential scale compressors. There are more parts involved, so there’s a greater chance of hardware failure, but the well understood nature of the piston and cylinder as well as massive manufacturing tolerances make them cheap to manufacture. Consider, steam engines were around in the 1800s, and this is the same principle as their driving pistons. The complexity […]

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How Does a Scroll Compressor Work?

Once upon a time, I thought there was really just one kind of compressor. How many ways can their possibly be to make something smaller? Turns out, quite a few. Each type of compressor has its own quirks. Some designs are more efficient. Some require less maintenance. There’s just this endless list of trade offs in designs to get a […]

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Albert Einstein Designed a Fridge

We all know Einstein as the man who invented E=MC2. He also used experiments to find Avogadro’s Number, proposed that light was not just a wave but also a particle (a photon), created the General Theory of Relativity, and among all his accomplishments, designed a fridge without a single moving part. As with all things in our industry, this relied on cheating the laws of physics into doing our bidding.   Motivation The first refrigerators were deadly machines. They used a similar compression system to what we have today, but there was a catch. The new technology had a short lifetime before failure and when it did fail, it failed deadly. At the time, there were three major refrigerants: methyl chloride, ammonia, and sulfur dioxide. Methyl Chloride can disrupt the central nervous system, starting with drunken symptoms and ending at paralysis, coma, and death. Ammonia is incredibly corrosive and will cause irritation of the skin, eyes, and lungs before more severe symptoms such as blindness and death by lung failure set in. Sulfur Dioxide is similar to ammonia, it attacks the skin and mucous membranes, and with the right circumstances can damage and destroy the lungs, and even interfere in the heart. The seals on early fridges would fail at random due to the newness of the technology, variations in product quality, and perhaps even outright design flaws. When such a failure occurred, toxic gasses got into the air, and […]

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