by Valerie Valdez
In the old days, housewives hung the clothes out on the clothes line to dry. While some people still do it, most households have a dryer. But which one should you buy and which one is the best?
A Tumbler dryer is the simplest, most reliable and widely used type. It draws in the cool, dry air around it and heats it before passing it through the tumbler. The resulting hot, humid air is vented outside to make room for more dry air to continue the drying process. This design doesn’t recycle the heat put into the load and is environmentally wasteful.
A Condenser dryer is similar to a normal dryer, but instead of exhausting the air, the dryer uses a heat exchanger to cool the air and condense the water vapor into a drain pipe or a collection tank. The dryer air is run through the loop again. The condenser dryers typically use more power than conventional dryers.
Heat Pump dryers allow the hot air from the tumbler to pass through a heat pump where the cold side condenses the water vapor into a drain pipe or a collection tank and the hot side reheats the air for re-use. It conserves much of its heat within the dryer instead of exhausting it into the surroundings. Heat pump dryers can use up to 50% less energy.
A new type of dryer is the Mechanical Steam Compression dryer that instead of using hot air, uses water recovered from the clothing in the form of steam. The tumbler and its contents are superheated and the wet steam that results purges the system of air. This wet steam exits the tumbler and is mechanically compressed to extract water vapor and transfer the heat of vaporization to the remaining steam.
This pressurized steam expands, and is heated then injected back into the tumbler where its heat causes more water to vaporize from the clothing, creating more steam and restarting the cycle. Like heat pump dryers, mechanical steam compression dryers recycle much of the heat, and the higher temperatures result in faster drying times.