Evaporative cooling is great. It’s how our bodies keep cool when it’s hot. We sweat. The sweat evaporates and that phase change carries heat away from our bodies because it takes heat to turn liquid water into water vapor.When you spray a mist of liquid water into the air, the tiny droplets of liquid can evaporate into individual water vapor molecules.
image/text credit: MissouriWindandSolar
Again, it takes heat to do that, and in this case the heat comes from the air. The result is cooler air. If you live in a dry climate, you may even use this principle to cool the air in your home with a device called a swamp cooler.Now, let’s take that principle and apply it to your air conditioner.
I’ve explained how air conditioners work in a previous article, collecting heat from inside the house and dumping it to the air outside the house. Because the outdoor air is hot, the compressor has to make the refrigerant that carries that heat even hotter than the outdoor air because heat always flows from hot to cold, or in this case, hotter to hot.
If you can evaporate water into the air right before it gets pulled into the condensing unit, you can decrease the temperature of the air and thus increase the capacity and efficiency of your air conditioner. Then, instead of dumping that heat from hotter to hot, you’re dumping it from hotter to not-quite-as-hot, and that’s easier to do.