Most dryers consist of a rotating drum through which high-temperature air is circulated. The hot air removes the moisture from the fabric through evaporation. The drum is rotated relatively slowly in order to create a tumbling effect. In most cases, the drum is belt-driven by an induction motor.
There are generally two classes of dryer: electric and gas. Both of these refer to the method used to elevate the temperature of the air flowing through the drum.
Electric Dryers
The electric dryer generally uses a coiled wire that is heated by using electric current. The amount of electric current is varied to adjust the air temperature.
Gas Dryers
The gas dryer employs a gas burner that burns natural gas, propane or butane to form a jet of hot gases that are directed into a venturi chamber that uses the bernoulli effect to pull in ambient air so as to raise its temperature. The air temperature can be adjusted by adjusting the size of the gas flame.