Correlation of the Area-Mass Transfer Coefficient Inside the Drum of a Clothes Dryer

Abstract

The mass transfer process inside the drum of a clothes dryer affects its performance. The area-mass transfer coefficient was defined and correlated to the weight of the clothes, drum speed, the Reynolds number, Schmidt number, and Gukhman number using the experimental results of 32 runs on a Frigidaire clothes dryer. The coefficient of correlation was 0.994. A separate correlation for the Sherwood number was evaluated for a single piece of cloth stretched perpendicular to the flow in a pipe. This second correlation was used to compare the mass transfer inside the actual dryer with that of the “idealized” mass transfer process for a single piece of cloth. The results indicated that the average mass transfer efficiency for clothes in the dryer was only 26.4% of the ideal process. Means to enhance the area-mass transfer coefficient and the reasons for the poor performance of an actual dryer are discussed.

Keywords:

• Clothes drying
• Correlation
• Dryer efficiency
• Drying process
• Mass transfer efficiency
• Mass transfer process

Acknowledgments

We gratefully acknowledge funding for this research by Frigidaire, IEC (Iowa Energy Center), CATD (Center for Advanced Technology Development), the office of the Provost at Iowa State University, and equipment provided by the Department of Mechanical Engineering. We also acknowledge the contribution of ISU technicians (Gay Scandrett and Jim Dautremont) and the contribution of Seung-Bae Hong in the early stages of the project.

Notes

^aIt is the area of clothes occupying the drum subtracted from the flow area of the drum.

^bThe water concentration in cloth or moisture content is defined as (M _wc–M _dc), where M _wc is the wet weight of cloth and M _dc is the dry weight of cloth.