Compared to a standard or high-efficiency clothes washer, a clothes dryer is a very simple appliance. Every dryer from the most simple to the most expensive uses a combination of heat, air, and motion to dry clothes by removing moisture.
How a Clothes Dryer Produces Heat
Every clothes dryer uses heat to speed the drying of clothes. The heating element can be fueled by electricity, natural gas or propane gas.
In dryers powered solely by electricity, the heating coils are similar to those used in ovens or hot water heaters. An electric current is sent through the coil which is designed to create resistance. The resistance builds up electrons and creates energy or heat. The metal coils become very hot from the electron buildup. The heat is transferred to the surrounding air and forced throughout the dryer by a blower or fan.
Natural gas or propane gas dryers depend upon a pilot light which ignites the gas creating heat. Gas dryers use metal plates designed to transfer the created heat into the air. Again a blower moves the heated air throughout the dryer to the wet laundry. While gas is used to create heat, all gas dryers also require electricity to power other components of the dryer.
All dryers use thermostats and thermal fuses to regulate the temperature within the dryer. These parts are key to the safe operation of the appliance preventing overheating which can lead to fires. When one of the fail-safe components fails, it is important to look for the root cause of the problem. A blown fuse means the dryer is overheating. A good cleaning to get rid of lint may be all that is needed to prevent a problem down the road.
How a Clothes Dryer Circulates Air
Air circulation is essential to efficient clothes drying. Think about how much more quickly clothes dry on a clothesline when there is a breeze. The amount of time it takes clothes to dry is largely related to the flow of air through the machine. Air is drawn into the dryer through openings or vents on the outside of the housing. The air is heated and distributed throughout the drum by a fan or blower. The heated air helps to draw the moisture from the clothing.
Fresh air is continuously drawn in during the drying cycle in all vented dryers, as the moisture-laden air is forced through the lint screen and out the back of the dryer into a duct that should be vented to the outside of the home. Incorrect venting or blockages in the venting will impede the airflow and slow the drying efficiency of the appliance.
Ventless clothes dryers draw fresh air into the dryer where it is heated and passed through the clothes, but instead of being vented out the air travels through a heat exchanger. The heat exchanger cools the air causing the moisture in the air to condense and flow into a drainpipe or into a containment chamber within the dryer. As the air is dried, it is reheated and passed through the clothes again. The process is repeated until the clothes are dry.
How a Clothes Dryer Tumbles Clothes
The dryer drum is designed to move and tumble the clothes. Without the tumbling motion, the clothes would lie in a huge pile making air circulation nearly impossible. Almost all dryer drums are turned by a simple pulley system powered by an electric motor. The dryer drum sits on a roller system and most are supported by an axle.
Special Features on Some Clothes Dryers
While the components described above are basic to every clothes dryer, there are additional systems and features available. Dryers offer different cycle options from timed to automatic moisture sensing. Some controls are a basic system of cams, gears and electrical contacts. Newer, more expensive dryers are controlled by computer electronics.
Some new dryers feature a steam dry feature. The steam feature creates steam in the dryer independent of a traditional drying cycle. Steam drying is used to freshen clothes that are wrinkled or have strong odors. These dryers require a water line or have a water reservoir that must be filled manually and an additional heating element for the water to create the steam mist.