What is "hand fan"

n. A hand-held device designed to be waved back and forth in order to induce airflow for the purpose of cooling the user.

A handheld fan is an implement used to induce an airflow for the purpose of cooling or refreshing oneself. Any broad, flat surface waved back-and-forth will create a small airflow and therefore can be considered a rudimentary fan. Generally, purpose-made handheld fans are shaped like a sector of a circle and made of a thin material (such as paper or feathers) mounted on slats which revolve around a pivot so that it can be closed when not in use.

The movement of a handheld fan provides cooling by increasing the airflow over the skin, which in turn increases the evaporation rate of sweat droplets on the skin, and increasing heat convection by displacing the warmer air, produced by body heat, that surrounds the skin. This evaporation has a cooling effect due to the latent heat of evaporation of water. Fans are convenient to carry around, especially folding fans.

Next to the folding fans, the rigid hand screen fan, was also a highly decorative and desired object among the higher classes. Its purpose is different since they are more cumbersome to carry around. They were mostly used to shield the lady's face against the glare of the sun or the fire.