Fans generate airflow. There are two basic kinds of fans in use today. One is the blower wheel, which is a flat disc with protruding vanes. It takes up less space but needs to be cleaned frequently, or it will become unbalanced and create excessive noise and wear out the motor bearing. The other is a paddle type fan, in which a number of flat surfaces are positioned perpendicular to the hub.
Paddle fans require a larger housing but provide greater airflow and smoother operation.
There are also several different types of heating elements. The two main ones are calrod or incoloy and coil wound. Calrod heating elements are similar to the burners on an electric kitchen range. They take longer to heat up cool down, but they are very long-lasting and virtually unbreakable. Once you are familiar with the terms used to describe dryers, consider the various types available.