Why does desiccant cool down air?

Question

I put a lot of desiccant inside a large airtight container and left it for a while, then I opened it and put my hand inside, I can feel the air is much cooler, why is that?

Answer 1

The adsorption of water to a desiccant actually releases heat. But the slight temperature rise this causes is counteracted by equilibration with the outside of the container.

So at this point, the air inside of the container will have the same temperature as the air outside, but a lower humidity.

Now, if you put your hand in, it feels cooler than the air around, because more moisture on your hand evaporates in the dried air, cooling the surface of your hand.

Answer 2

Using $PV=nRT$ (as a simplification), since your container is closed, $V$ is constant. But the desiccant lower the water molecules and since the container is in contact with the environment, you can think of the process as an isothermal process. So the pressure must go down.

Surface evaporation is more likely in lower pressure environments and your hand has water molecules on it (moisture) so by surface evaporation. your hand loses heat.