Alternative Drying: Heat Pump Dryers

Nowadays households have an increased need to dry their clothes quickly, and also to save as much as possible on their bills. The most popular devices are tumble dryers that make the moisture evaporate from the clothes through a procedure that uses a great amount of energy and water. There are two different ways to expel the water: either through air vented dryers that push the moisture out while generating stenches, steam, and noise, or air condenser dryers that use a heat exchanger to dry the clothes.

Heat pump dryers, instead, work as a condenser and a heat pump by pushing moisture from the drum to the evaporator. There, it is dehumidified, and the air is blown back into the drum. Advantages stem from a reduced and optimized use of energy (they rank in the A category for appliances efficiency). Lower wasted heat is being produced, so that the device can work well even at higher temperatures,  leaving no stench or steam. Also, no cooling effect derives from the process, as in the case of air vented dryers. Heat pump dryers currently have a low market penetration, but there are signs suggesting further development and success in the future. At present, these devices are priced higher than the traditional dryers, as they have more expensive elements with respect to the other models.

Heat pump dryers, however, are used not only for clothes, but also for some agricultural products and crops such as grain, fruit, or medicinal plants.This is an alternative to solar drying in order to preserve their taste and quality, and the substances contained in the food while avoiding them to rot. However the drying procedure needs to be controlled and to follow certain guidelines in order for the products to keep their properties and not lose value during the processing. Usually the best option is a heat pump dryer that dehumidifies, so that low temperature and low humidity are needed, which is good for sensible crops. The efficiency of these machines is measured by looking at the relation of the water evaporated from the product, and both energy and time needed to perform the operation.