Novel Drying Technologies

**111**

**Chapter 6**

**Abstract**

Vibration

thermal drying process.

**1. Introduction**

ultrasonic transducer, physical mechanism

The Study of Fabric Drying

*Chang Peng and Saeed Moghaddam*

Using Direct-Contact Ultrasonic

Our existing cloth drying technology is an energy-intensive process, which generally involves blowing hot air across tumbling wet fabrics to facilitate evaporation and moisture removal. To address the relatively low energy efficiency of existing cloth drying techniques, in this chapter, a totally new cloth drying technology is introduced, which uses high frequency ultrasonic vibrations generated by piezoelectric transducer instead of thermal heating to extract moisture in cloth as a cold mist, dramatically reducing drying time and energy consumption. The physical mechanism of ultrasonic fabric drying process in direct-contact mode is first studied. A novel ultrasonic transducer driving method, in which the power supply to the transducer is regulated by a binary modulating signal, is then developed for use in direct-contact ultrasonic drying of fabrics. A demonstration unit is finally fabricated to show the efficacy of the process and its energy saving compared to

Clothes dryers offer a rapid means to dry laundry in households but consume substantial residential electricity. Clothes dryers are the second largest source of residential energy use in a household following water heater [1]. Every year the operation of clothes dryers in the United States consumes as much electricity as does the entire state of Massachusetts (60 billion kWh per year) [2]. The demand of clothes dryers in U.S. has increased by nearly 6% over the last decade. Until 2009, 80% of U.S. households had a clothes dryer and 80% of them are electric clothes dryers, the remaining being gas dryers [3]. Although a set of technologies such as air-vented dryers and heat pump dryers have been introduced to the market, the energy efficiency of clothes

In the current clothes dryer architecture, the clothes dry by passing hot air over the wet fabric. The state of the art for clothes drying technology involves mechanical (centrifugal) water extraction in the washing machine followed by thermal drying in a dryer. The moisture initially extracted by the washing machine reduces the remaining moisture in the clothes to ~50% of the dry weight [4]. The clothes are then placed in a dryer drum, where the remaining moisture is removed by circulating heated air through them. Thermal water removal from clothes in all existing

**Keywords:** fabric drying, energy efficiency, ultrasonic vibration,

dryers has not been improved significantly over the last 20 years.

#### **Chapter 6**
