Or should it be the other way around, because hotter water evaporates easier than cold water?
I know this sounds stupid, so just hear me out.
I use an evaporative cooler and add normal room temperature water. Someone told me to add cold water from the refrigerator to get better results. I intuitively thought that indeed cold water will produce colder air.
But as we all know evaporative coolers cool air by using the air to evaporate water which takes away heat from the air. So, we need the water to evaporate to cool the air. But we know that hotter water evaporates easier than cold water.
So, should it not be the case that refrigerated water will actually not evaporate as efficiently and hence not produce cooler air than in case of room temperature water ?
For what it's worth, I tried both and could not feel any noticeable difference, but of course, it was nowhere close to a controlled experiment. So, I would appreciate an answer about what does physics predict what would happen?
Best Answer
It depends on whether or not you are calculating cooling per unit time or cooling per unit water.
Per unit water, you get (a little bit) more cooling. Besides the enthalpy of vaporization, you get a little bit more cooling as the water absorbs heat to come up to room temperature.
Per unit time, the speed of evaporation will be (slightly) less. As you mention, the warmer water will vaporize more rapidly.
Neither of these effects are large. The total budget is dominated by the vaporization. A 15 degree C difference in the water will be hard to notice.