The history of domestic refrigeration began long before the appearance of the compressor units we are used to, and few people think that the first devices operated on completely different physical principles and chemicals. Unlike modern inert freons, early refrigerants often they were highly toxic, flammable or caustic, which imposed serious restrictions on the design and scope of technology. Understanding what refrigerators used to work on is necessary not only for general development, but also for the correct operation of ancient specimens, which can still be found in collections or in country houses.
The first attempts at artificial refrigeration were based on the use of absorption cycles, where thermal energy played the role of the driving force instead of an electric compressor. The working fluid was most often a mixture ammonia and water, less often - sulfur dioxide, which made these units powerful, but potentially dangerous if depressurized. It was the chemical composition of the “blood” of the refrigerator that determined its dimensions, noise level and even the method of connection to the energy source.
The evolution of refrigerants followed the path of finding a balance between heat transfer efficiency and safety for humans. If in the 19th century engineers experimented with volatile ethers and methyl compounds, then the 20th century brought the era of fluorocarbons, which radically changed the idea of everyday comfort. However, before the advent of this era, the world knew completely different odors and risks associated with leaks of working substances.
Ammonia and the absorption cycle
One of the most common substances in the history of refrigeration is ammonia (R717), which has been actively used since the middle of the 19th century. In absorption refrigerators, which became widespread in the USSR (famous models ZIL or Crystal), ammonia served as a refrigerant, and hydrogen or helium served as a buffer gas. The principle of operation was to heat the mixture, separate the components and then evaporate ammonia, which made it possible to achieve low temperatures without the use of moving mechanical parts.
This design had a number of unique advantages, the main of which was absolute noiselessness and durability. The absence of a compressor meant that there was practically nothing to break into the device, and such units could operate for decades, while consuming significantly less electricity or operating even from the open flame of a gas burner. However, ammonia also has a downside - its pungent odor and toxicity at high concentrations.
- 🧪 High efficiency: Ammonia has excellent thermophysical properties, providing rapid cooling.
- ⚠️ Toxicity: Ammonia leakage is hazardous to health, although in modern household quantities absorption models, the risk is minimal.
- 🔥 Versatility: Ability to operate on gas, electricity or even a car battery.
⚠️ Attention: Old Soviet-made absorption refrigerators may have thinner heat exchanger tubes. If a persistent smell of ammonia appears, operation must be stopped immediately, since the mixture of ammonia with air is explosive.
Modern analogues of such systems are often used in motorhomes and campers, where independence from the electrical network is important. Despite the fact that the efficiency of absorption systems is lower than that of compressor systems, their reliability and ability to operate silently make them irreplaceable in certain niches.
Sulfur dioxide and ether: a dangerous past
Before the chemical industry learned to synthesize safe fluorocarbons, engineers were forced to use what nature provided, even if it was dangerous. Sulfur dioxide (sulfur dioxide) and various types ethers (methyl, ethyl) were the main working fluids at the end of the 19th and beginning of the 20th centuries. These substances easily passed from a gaseous state to a liquid state at a relatively low pressure, which simplified the design of compressors of that time.
However, the use of such refrigerants required increased vigilance from owners. Ether vapors are extremely flammable, and any spark in the electric motor could lead to a fire. Sulfur dioxide, in turn, upon contact with air moisture, formed sulfurous acid, which caused corrosion of metal parts and was dangerous for breathing. That is why the first refrigerators were often installed in separate rooms or kitchens with powerful ventilation.
Why were these substances abandoned?
The refusal occurred not only because of the danger. With the development of chemistry, more stable compounds appeared that did not decompose at high compression temperatures and did not require complex sealing. In addition, the smell of sulfur and ether in a living room was simply unbearable at the slightest leak, which made the domestic use of such units extremely inconvenient.
Maintenance of such machines was complex and required special skills. Mechanics had to constantly monitor the integrity of oil seals and seals, since the molecules of ether and sulfur dioxide were very small and easily penetrated through microscopic gaps.
- 💨 Volatility: Ethers are highly volatile, which accelerated cooling cycles, but increased the risk of leaks.
- 🔥 Fire hazard: The main reason for banning ethers in household appliances is the risk of explosion.
- 🏭 Corrosion: Decomposition products of sulfur compounds quickly damaged steel pipelines.
⚠️ Attention: If you are the owner antique refrigerator from the early 20th century, do not under any circumstances try to start it without checking it by a specialist. Remains of sulfur compounds can be preserved in the system, and their release in a confined space of an apartment is unacceptable.
Carbon dioxide and methyl chloride
In parallel with toxic substances in the history of refrigeration, there were also more inert, but technologically sophisticated alternatives. Carbon dioxide (CO2) and methyl chloride (R40) have carved out a niche in commercial and industrial refrigeration, as well as some premium consumer models. Carbon dioxide was attractive due to its inflammability and availability, but required the creation of systems operating under enormous pressure - up to 70 atmospheres and higher.
Methyl chloride, also known as freon-40, was less more aggressive to oils than ammonia, and had no odor, making it attractive for home use. However, it was also toxic and at certain concentrations became explosive. Methyl chloride devices often had more massive compressors designed for the specific properties of the gas.
The technology of that time did not allow the creation of compact and sealed systems that could withstand high pressure CO2 or the aggressive environment of chloride compounds, so such refrigerators were bulky and expensive.
Interestingly, methyl chloride is still sometimes used in cascade deep-freezing systems, where it is necessary to achieve ultra-low temperatures inaccessible to conventional freons.
Comparison of old and modern refrigerants
In order to understand the scale of technological progress, it is necessary to compare the characteristics of the substances on which refrigerators worked earlier with modern analogues. The evolution went from dangerous and unstable compounds to inert and safe ones, and then to environmentally friendly ones.
| Refrigerant | Period of active use | Toxicity | Flammability | Main disadvantage |
|---|---|---|---|---|
| Diethyl ether | 1850–1930 | Low | High | Explosive vapors |
| Sulphurous anhydride | 1870–1930 | High | No | Corrosion and suffocation |
| Ammonia (R717) | 1850 – present | High | Medium | Pungent odor, toxicity |
| Methyl chloride (R40) | 1920–1950 | Average | High | Toxicity upon leakage |
| Freon-12 (R12) | 1930–2000 | No | No | Destruction of the ozone layer |
As can be seen from the table, the main driver of the change in generations of refrigerants was safety and environmental friendliness. Freonswhich replaced ammonia and ethers, At first they seemed like an ideal solution: they were odorless, did not burn and were not poisonous. However, later it turned out that their stability plays a cruel joke on the ecology of the planet.
Problems of tightness and maintenance
The use of aggressive and volatile substances in early refrigerators dictated special requirements for materials and assembly. Unlike modern sealed circuits, where the compressor is sealed in a steel casing, older systems were often semi-open or open. This meant that the compressor shaft came out through the stuffing box seal, which wore out over time.
Owners had to regularly check the refrigerant level and, if necessary, call the “refrigerator” for refilling. This was a labor-intensive process that required special equipment and knowledge. Often, a simple method was used as a leak indicator: they brought a burning candle to the pipe connections - if the flame changed color (turned green), it means that refrigerant vapor was present in the air (it worked especially effectively with chlorine-containing substances).
- 🔧 Regular lubrication: Open compressors required constant monitoring of the oil level.
- 🛠️ Replacing oil seals: Rubber seals quickly hardened from contact with oils and gases.
- 🌡️ Pressure control: Pressure gauges were a mandatory tool in the service kit.
⚠️ Attention: Technical characteristics and permissible Leakage standards for retro equipment may differ from modern standards. When servicing vintage units, always check the original manufacturer's documentation, since modern oils and gases may be incompatible with old seal materials.
With the advent of freons and the development of soldering technology for copper tubes, it was possible to create completely sealed “black boxes” that operate without maintenance throughout their service life. This became possible due to the inertness of new gases to the system materials.
Environmental aspect and transition to new substances
For a long time, engineers did not think about what happens to the refrigerant after it leaves the system. It was believed that if the gas is not toxic to humans in small doses, then it is also safe for nature. However, the discovery of the ozone hole in the second half of the 20th century turned the industry upside down. It turned out that chlorofluorocarbons (CFC)such as the famous R12, rising into the upper layers of the atmosphere, under the influence of ultraviolet radiation destroy ozone molecules.
This led to the adoption of the Montreal Protocol and the gradual ban of old freons. The search began for new substances that would be safe for both humans and the planet. This is how hydrofluorocarbons (HFCs) did not contain chlorine, and then a return to natural refrigerants such as isobutane (R600a), which, like ether in the past, is flammable, but in microscopic quantities (less than 150 grams in a modern refrigerator) is absolutely safe.
☑️ Environmental friendliness of refrigerants
Today we are seeing a full circle of history: from dangerous natural substances (ammonia, ether) we moved to safe synthetics (freons), and now we are returning to natural gases (propane, butane, CO2), but having already learned to control them with the help of electronics and durable materials.
Understanding that what refrigerators used to work on helps to appreciate the complexity of engineering solutions of the past. Each stage of development of refrigeration technology was dictated by the need to solve a specific problem: to make the unit more powerful, safer, more compact or more environmentally friendly.
Frequently asked questions (FAQ)
Is it possible to fill an old Soviet refrigerator with modern freon?
Theoretically this is possible, but technically it is extremely difficult and often not economically feasible. Older systems ran on R12 freon or ammonia, which require different types of compressor oil. Replacing the refrigerant will require a complete flush of the system, an oil change, and possibly a compressor change. It is easier and safer to replace the unit with a modern one.
Why did old refrigerators hum louder than modern ones?
The main reason is the design of the compressor and the lack of high-quality sound insulation. Early motors had an open design and were mounted rigidly to the body. In addition, the refrigerants of that time required higher pressures or larger volumes of pumping, which increased the load on the mechanics.
Is ammonia dangerous in household absorption refrigerators?
In good condition - no. The amount of ammonia in a household refrigerator system (ZIL, Saratov) is only a few tens of grams. When leaked, it dissipates quickly. The only danger is a large concentration in a closed, unventilated space, which is unlikely in an ordinary kitchen.
How to determine what gas was in the refrigerator of the 50s?
Usually this information is indicated on a metal plate (nameplate) on the back or inside cameras. Look for the designations R12, R22 or the words “Freon”. If the refrigerator is absorption (without a compressor), an ammonia mixture was almost certainly used.