Non-Profit Internet Source for News, Events, History, & Culture of Northern Frederick & Carroll County Md./Southern Adams County Pa.


Real Science

The chemistry of air-conditioning

Michael Rosenthal

(10/2017) I grew up in northeastern Ohio in the nineteen-forties. The United States was engaged in World War II, and technological developments at home were limited, as resources were directed largely to the war effort. There were no new cars on the market until 1946, and ration stamps were used to limit scarce items in food purchase. I remember anxiously waiting for Juicy Fruit chewing gum to come back on the market; it disappeared due to ingredient shortage (we were told) and the demand for distribution via "C-Rations" to the troops.

I lived in a house built in the early days of The War (as we called it). It was a comfortable home, modern for its time compared to pre-war houses, but it had no central air conditioning. So in the hot summers, we opened the windows and used electric fans to cool us. Eventually, when they became available, my parents installed a window air conditioner in the master bedroom; when it was very hot, I was invited in for a while to cool off. What a treat! Of course cars had no air conditioning either, and we drove with the windows open to cool off, unless one was lucky enough (and wealthy enough) to own a convertible. I also remember the treat in going into an air-conditioned movie theater.

Now we take air conditioning everywhere for granted, in restaurants, in theaters, in stores, in cars, and at home, though one still sees those air conditioning units sticking out of windows in older neighborhoods (do they still work?).

The original refrigerants in air conditioners were ammonia, methyl chloride, and propane, none of them a good idea from the standpoints of toxicity and flammability. In 1928 chlorofluorocarbons (CFCs) were discovered and replaced these dangerous ingredients. Chlorofluorocarbons are chemicals which have carbon atoms bonded to fluorine and chlorine atoms; however, when these chemicals are released in the air, they rise to the upper atmosphere where ultraviolet radiation triggers reactions that release chlorine atoms. Chlorine atoms attack and destroy ozone molecules. In 1987, the Montreal Protocol required production of CFCs to stop. Hydrofluorocarbons (HFCs) were introduced as replacements. They contain no chlorine, and thus remove the danger to the ozone layer; however, HFCs have a high global warming potential, and in 2016, an amendment to the Montreal Protocol planned a phase-out of HFCs as well. So what is next? Hydrofluoroolefin refrigerants may be the replacement. They have a lower global warming potential, but are more expensive. Thus, there is an open research field to develop a well-working, non-toxic, and affordable refrigerant that minimizes danger to the environment.

So how does this all work? In a compressor, refrigerant vapor is pressurized, which increases its temperature. The hot high pressure vapor moves through condenser coils and loses heat, which is vented outside by fans. The refrigerant, now a liquid, is forced through an expansion valve. This turns the liquid into a mist and rapidly cools it. Finally, the cold mist travels through evaporator coils. Air blown over the evaporator coils is cooled while heat from the air vaporizes the refrigerant. The cool air is blown into your car or your house, where the warm air is expelled into the atmosphere. Air conditioning can be thought of as a luxury, but as recent events that have occurred due to the hurricanes have shown, it can be life-saving as well, especially in very hot climates.

Now for some updates on topics we have discussed in earlier articles and a bit on Hurricane Harvey.

There are still those individuals who oppose vaccines and claim that vaccines induce autism. There is absolutely no scientific evidence to support this assertion. Minnesota recently had its worst measles outbreak in decades. There are anti-measles activists there who have even suggested having "measles parties" to expose unvaccinated children to others infected by measles so they can contract the disease and acquire future immunity. Is this crazy or what?

The outbreak in Minnesota seems to have originated from a Somali American community from which some 8,200 people were exposed in day-care clinics, schools and hospitals. Some twenty-two people were hospitalized, many with high fever, breathing difficulties, and dehydration. No deaths have been reported at the date (late August) of my source (The Washington Post). On the positive side, many individuals have recognized the need for vaccination, with some 8,000 vaccinations reported between April and July in 12 clinics. The Somali imans (clergy) have been urging people to get their children vaccinated.

I had measles as a child (as well as Chicken Pox). Luckily I survived the experience, but it wasn’t fun. I was confined to our home for two weeks, and I was fortunate to have no lasting effects. In those days, they posted a red sign (as I remember it) on your door as a quarantine measure, to prevent your infecting others. Measles was essentially eliminated in the United States in 2000, but has resurfaced due to the anti-vaccination movement. Though the effects of measles resemble a bad cold, and the virus is usually cleared within 14 days, complications can include pneumonia, blindness, encephalitis, and swelling of the brain. One rare complication actually can kill children years after their infection.

We’ve written several times about the lead contamination in Flint, Michigan, which occurred when Flint changed its water supply to the nearby Flint River in 2014. Recent chemical and microscopic analyses conclusively reveal that the lead came from corrosion of the water pipes. To begin with, one should never use lead pipes to carry drinking water. But what happened in Flint, we now know, was that the city did not treat the Flint River water with a corrosion inhibitor (orthophosphate) which would have largely or fully prevented the lead from being released. The crisis lasted one and one-half years, and calculations show that a lead pipe delivering water to a single Flint household would have released some 18 grams of lead into the flowing water.

Finally, let’s look at the impact of Hurricane Harvey’s impact on air quality. Texas wins points from us on their development of renewable energy. But Harvey struck back at their progress by causing the release of some million pounds of air pollutants into the atmosphere. These pollutants came from oil refineries, chemical plants, and shale drilling sites, which have experienced chemical leaks and discharges, and flaring. These released chemicals include benzene, 1,3-butadiene, hydrogen sulfide, sulfur dioxide, toluene, and xylene. Some of these chemicals are carcinogenic and all are poisonous and environmentally damaging. The Center for Biological Diversity reports the releases total at more than 5 million pounds.

In addition to the direct release, river overflow washed over waste pits and drilling pads at shale gas and shale oil sites in Central Texas, causing yet unevaluated damage to the environment. Damage to rooftops in oil refinery storage tanks caused evaporation and oil spills. Flooding caused a problem due to excessive rainfall which has been a serious concern at the Beaumont Agro plant of BASF, the second largest producer of chemical products in North America, whose primary products are pesticides, herbicides, and insecticides. Texas is the nation’s largest producer of chemicals.

Michael is former chemistry professor at Mount. St. Marys

Read other articles by Michael Rosenthal