Product Code Database
A clothes dryer ( tumble dryer, drying machine, drying device, or simply dryer) is a powered Home appliance that is used to remove moisture from a load of clothing, bedding and other textiles, usually after they are washed in the washing machine.
Many dryers consist of a rotating drum called a "tumbler" through which heated air is circulated to evaporate moisture while the tumbler is rotated to maintain air space between the articles. Using such a machine may cause clothes to shrink or become less soft (due to loss of short soft fibers). A simpler non-rotating machine called a "drying cabinet" may be used for delicate fabrics and other items not suitable for a tumble dryer. Other machines include steam to de-shrink clothes and avoid ironing.
Tumble dryers are sometimes integrated with a washing machine, in the form of washer-dryer combos, which are essentially a front loading washing machine with an integrated dryer or (in the US) a laundry center, which stacks the dryer on top of the washer and integrates the controls for both machines into a single control panel. Often the washer and dryer functions will have a different capacity, with the dryer usually having a lower capacity than the washer. Tumble dryers can also be top loading, in which the drum is loaded from the top of the machine and the drum's end supports are in the left and right sides, instead of the more conventional front and rear. They can be as thin as in width, and may include detachable stationary racks for drying items like plush toys and footwear.
In terms of energy use, condenser dryers typically require around 2 kilowatt hours (kW⋅h) of energy per average load.
Because the heat exchange process simply cools the internal air using ambient air (or cold water in some cases), it will not dry the air in the internal loop to as low a level of humidity as typical fresh, ambient air. As a consequence of the increased humidity of the air used to dry the load, this type of dryer requires somewhat more time than a tumble dryer. Condenser dryers are a particularly attractive option where long, intricate ducting would be required to vent the dryer.
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 afterward for re-use. 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 up to 50% less energy required by either condensation or conventional electric dryers. Heat pump dryers use about 1 kW⋅h of energy to dry an average load instead of 2 kW⋅h for a condenser dryer, or from 3 to 9 kW⋅h, for a conventional electric dryer. Domestic heat pump dryers are designed to work in typical ambient temperatures from . Below , drying times significantly increase.
As with condensation dryers, the heat exchanger will not dry the internal air to as low a level of humidity as the typical 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 tumble dryers, depending on the model.
As wet steam exits the tumbler, it is mechanically compressed (hence the name) to extract water vapor and transfer the heat of vaporization to the remaining gaseous steam. This pressurized, gaseous steam is then allowed to expand, and is superheated before being injected back into the tumbler where its heat causes more water to vaporize from the clothing, creating more wet steam and restarting the cycle.
Like heat pump dryers, mechanical steam compression dryers recycle much of the heat used to dry the clothes, and they operate in a very similar range of efficiency as heat pump dryers. Both types can be over twice as efficient as conventional tumble dryers. The considerably higher temperatures used in mechanical steam compression dryers result in drying times on the order of half as long as those of heat pump dryers.
Given that this is a relatively simple and cheap technique to materialize, most consumer products showcase the added benefit of portability and/or modularity. Newer designs implement a fan heater at the bottom to pump hot air into the vertical drying rack chamber. Temperatures in excess of can be reached inside these "hot air balloons," yet lint, static cling, and shrinkage are minimal. Upfront cost is significantly lower than tumble, condenser and heat pump designs.
If used in combination with washing machines featuring fast spin cycles (800+ rpm) or spin dryers, the cost-effectiveness of this technique has the potential to render tumble dryer-like designs obsolete in single-person and small family households. One disadvantage is that the moisture from the clothes is released into the immediate surroundings. Proper ventilation or a complementary dehumidifier is recommended for indoor use. It also cannot compete with the tumble dryer's capacity to dry multiple loads of wet clothing in a single day.
A clean, unobstructed dryer vent improves both the efficiency and safety of the dryer. As the dryer duct pipe becomes partially obstructed and filled with lint, drying time markedly increases and causes the dryer to waste energy. A blocked vent increases the internal temperature and may result in a fire. Clothes dryers are one of the more costly home appliances to operate.
Several factors can contribute to or accelerate rapid lint build-up. These include long or restrictive ducts, bird or rodent nests in the termination, crushed or kinked flex transition hose, terminations with screen-like features, and condensation within the duct due to un-insulated ducts traveling through cold spaces such as a crawl space or attic. If plastic flaps are at the outside end of the duct, one may be able to flex, bend, and temporarily remove the plastic flaps, clean the inside surface of the flaps, clean the last foot or so of the duct, and reattach the plastic flaps. The plastic flaps keep insects, birds, and snakes out of the dryer vent pipe. During cold weather, the warm wet air condenses on the plastic flaps, and minor trace amounts of lint sticks to the wet inside part of the plastic flaps at the outside of the building.
Ventless dryers include multi-stage lint filtration systems and some even include automatic evaporator and condenser cleaning functions that can run even while the dryer is running. The evaporator and condenser are usually cleaned with running water. These systems are necessary, in order to prevent lint from building up inside the dryer and evaporator and condenser coils.
Aftermarket add-on lint and moisture traps can be attached to the dryer duct pipe, on machines originally manufactured as outside-venting, to facilitate installation where an outside vent is not available. Increased humidity at the location of installation is a drawback to this method.
In the United States, an estimate from the US Fire Administration in a 2012 report estimated that from 2008 to 2010, fire departments responded to an estimated 2,900 clothes dryer fires in residential buildings each year across the nation. These fires resulted in an annual average loss of 5 deaths, 100 injuries, and $35 million in property loss. The Fire Administration attributes "Failure to clean" (34%) as the leading factor contributing to clothes dryer fires in residential buildings, and observed that new home construction trends place clothes dryers and washing machines in more hazardous locations away from outside walls, such as in bedrooms, second-floor hallways, bathrooms, and kitchens.
To address the problem of clothes dryer fires, a fire suppression system can be used with sensors to detect the change in temperature when a blaze starts in a dryer drum. These sensors then activate a water vapor mechanism to put out the fire. careinfo.org , New S.A.F.E. system tackles safety problem of fires in laundry dryers , November 2001. Accessed 10 October 2011.
Clothes dryers are second only to refrigerators and freezers as the largest residential electrical energy consumers in America. "Emerging Technologies: A Case Study of the Super Efficient Dryers Initiative". ACEEE.org
In the European Union, the EU energy labeling system is applied to dryers; dryers are classified with a label from A+++ (best) to G (worst) according to the amount of energy used per kilogram of clothes (kW⋅h/kg). Sensor dryers can automatically sense that clothes are dry and switch off. This means over-drying is not as frequent. Most of the European market sells sensor dryers now, and they are normally available in condenser and Air vents dryers.
|
|
