Dryers (668)

A clothes dryer or tumble dryer is a household appliance that is used to remove the moisture from a load of clothing and other textiles, generally shortly after they are cleaned in a washing machine.

Most dryers consist of a rotating drum called a tumbler through which heated air is circulated to evaporate the moisture from the load. The tumbler is rotated relatively slowly in order to maintain space between the articles in the load. In most cases, the tumbler is belt-driven by an induction motor.

Using these machines may cause clothes to shrink, become less soft (due to loss of short soft fibers/ lint) and fade. For these reasons, as well as environmental concerns, many people use open air methods such as a clothes line and clotheshorse.

Traditional Dryers

Traditional dryers continuously draw in the cool, dry, ambient air around them and heat it before passing it through the tumbler. The resulting hot, humid air is simply vented outside to make room for more dry air to continue the drying process.

The traditional design makes no effort to recycle the heat put into the load, and so is quite inefficient. Nevertheless, the basic design is simple, reliable, and cheap.

It should be noted that some methods of salvaging this heat for in-home heating, by use of inline vent boxes equipped with a flapper valve to direct heat to indoor areas, poses the concern of increased humidity within a dwelling. Humidity from these devices causes a likelihood of mold, mildew, and bacterial growth inside a home. It is recommended that dryers, whether electric or gas, be vented outdoors with a 4-inch diameter piping.

Spin dryers

These machines simply spin their drums faster than a typical washer could in order to extract additional water from the load. They may remove more water in two minutes than a heated tumbler dryer can in twenty, thus saving significant amounts of time and energy. Although spinning alone will not completely dry clothing, this additional step saves a worthwhile amount of time and energy for large laundry operations such as those of hospitals.

Heat pump dryers

Whereas condensation dryers use a passive heat exchanger cooled by ambient air, these dryers use a heat pump. The hot, humid air from the tumbler is passed through a heat pump where the cold side condenses the water vapor into either a drain pipe or a collection tank and the hot side reheats the air. In this way not only does the dryer avoid the need for ducting, but it also conserves much of its heat within the dryer instead of exhausting it into the surroundings. Heat pump dryers can therefore use less than half the energy required by either condensation or traditional dryers.

As with condensation dryers, the heat exchanger will not dry the internal air to as low a level of humidity as the ambient air. With respect to ambient air, the higher humidity of the air used to dry the clothes has the effect of increasing drying times; however, because heat pump dryers conserve much of the heat of the air they use, the already-hot air can be cycled more quickly, possibly leading to shorter drying times than traditional dryers, depending on the model.