Air conditioners

Not only people need to stay cool, especially in a summer of record-breaking heat waves. Many machines, including cellphones, data centers, cars and airplanes, become less efficient and degrade more quickly in extreme heat. Machines generate their own heat, too, which can make hot temperatures around them even hotter. We are engineering researchers who study how machines manage heat and ways to effectively recover and reuse heat that is otherwise wasted. There are several ways extreme heat affects machines. No machine is perfectly efficient – all machines face some internal friction during operation. This friction causes machines to dissipate some heat, so the hotter it is outside, the hotter the machine will be. Cellphones and similar devices with lithium ion batteries stop working as well when operating in climates above 95 degrees Farenheit (35 degrees Celsius) – this is to avoid overheating and increased stress on the electronics. Cooling designs that use inn...

The U.S. Senate voted to ratify an international treaty on Sept. 21, 2022, agreeing to phase out a class of climate-warming chemicals that are widely used as coolants in refrigerators, air conditioners and heat pumps. If you’re getting a sense of déjà vu, don’t be surprised. These chemicals, called hydrofluorocarbons, or HFCs, were commercialized in the 1990s as a replacement for earlier refrigerants that were based on chlorofluorocarbons, or CFCs. CFCs were destroying the ozone layer high in the Earth’s atmosphere, which is essential for protecting life from the Sun’s harmful ultraviolet radiation. HFCs are less harmful than CFCs, but they create another problem – they have a strong heat-trapping effect that is contributing to global warming. If HFCs can be phased down globally – as many countries have agreed to do under the 2016 Kigali Amendment to the Montreal Protocol, the treaty just ratified by the U.S. Senate on a bipartisan...