Influence of load mass, drum speed and load composition on evenness of drying in a heat pump tumble dryer

Abstract

This work investigates the evenness of fabric drying in a household heat pump tumble dryer. The evenness of drying was defined as the standard deviation of the fraction of water, evaporated from each fabric item. Drying experiments were performed according to the IEC 61121 standard, which was also followed to determine quantities and types of cotton fabric items (towels, pillowcases and sheets) within each load. Regression analysis was performed to develop models for evenness of drying as a function of load mass and drum speed. Similarities between the tumble dryer energy efficiency parameters and the evenness of drying were analyzed. A high level of agreement was determined between responses of energy efficiency, drying time and evenness of drying to changes in drum speed. Effects of load mass were however more complex and were reflected in a non-linear response of evenness of drying to changes in load massthe best evenness of drying could be obtained at 2 kg load, followed by 6 kg and 4 kg load. Load composition was determined as an important factor affecting the evenness of drying. At larger loads, a sheet or a pillowcase in average contributed more to the un-evenness of drying than a towel. The presence of sheets and probably the ratio of sheets to other item types in the load were determined as the most probable factors that negatively affected the evenness of drying.

Investigation of fabric movement in a tumble dryer for the development of drying methods for wool fabrics to save energy

“…17 In addition, evenness of drying was better at the medium-level rotation speed, which was attributable to less squeeze of fabrics and even contact between fabrics and drying air. 18,19 Furthermore, fabric movement during tumble drying could influence the appearance of fabric in term of fabric smoothness. 18 If the fabrics are folded and entangled or trapped for prolonged time, the smooth appearance will be poor 18 .…”

“…17 In addition, evenness of drying was better at the medium-level rotation speed, which was attributable to less squeeze of fabrics and even contact between fabrics and drying air. 18,19…”

“…However, previous research on fabric motion and drying performance during tumble drying has mainly focused on cotton fabrics rather than wool materials. [17][18][19] The effect of fabric motion on the drying performance of wool fabrics in a tumble dryer was rarely studied.…”