Relationship between drying parameters and drying performance in domestic tumble dryers

Abstract

The purpose of this study is to investigate the effect of drying parameters on drying performance in an air-vented tumble dryer, and to optimize its drying performance by adjusting parameters. The critical drying parameters that influenced specific moisture extraction rate (SMER), final moisture content, evenness of drying, and smoothness appearance were determined by the analysis of variance in JMP software, which were rotational speed of the motor and load size, with clearly significant individual effects and binary interactions. In order to improve the applicability of the outcomes obtained in this study and to take into account the interactions between drying parameters and drum structure parameters on drying efficiency, non-dimensional analysis was used and the correlation between drying efficiency and dimensionless variables was studied. The Buckingham Pi theorem was applied to the problem to derive dimensionless Pi terms upon which the drying efficiency depends. A step regression analysis was then conducted to test the assumption that SMER was influenced by the dimensionless parameters based on the standard least squares fitting. Results indicated that the regression model showed an explanatory power of 73.8%. By adjusting the dimensionless parameters in the model, an optimized energy-saving drying program was obtained with the desirability goal of reducing the value of SMER. Compared with the original program, energy efficiency was improved by 32.4%.

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

“…Drum scaling effects have not yet been systematically measured and analyzed in open literature; however, they were approached indirectly through dimensional analysis. Studies [7,29] have shown that drum dimensions (radius, volume) are relevant in many non-dimensional groups that can be used to model the tumble dryer energy efficiency. Furthermore, drum radius together with drum speed defines the centrifugal force acting on fabrics, which is one of key factors that affects the fabric motion patterns.…”

“…Though not aimed at detailed analysis of parameters affecting the evenness of drying, the study demonstrated that the RMC i distribution for a 3.83 kg load depended on the types of cloths in the load. A more detailed study of evenness of drying was conducted by Yu et al [29] in a commercial air vented tumble dryer with a rated capacity of 10 kg. The drying experiment was performed at different drum motor speeds (800, 1000 and 1200 rpm), air velocities (4.8, 7.8 and 10.8 m/s) and constant heater power 3000 W. Three cotton loads of 1, 3 and 5 kg according to the GB/T 8629 [30] were used.…”

Improvement in drying performance through sample movement change in tumble dryers

“…At R 50/57.5(0) and R 50/ 57.5(1), the sample moved at a speed nearly equal to the drum rotational speed at the positions close to the drum wall due to the centrifugal force. However, in the case of R 50/57.5 (9) and R 50/57.5 (29), the sample did not continuously rotate along the drum wall and fell due to the change in the drum rotational direction, thereby passing through various positions.…”

“…In the XY plane, the total drying loads filled the internal space of the dryer at R 50/57.5(0) and R 50/57.5 (1). For frequent changes in the direction as in the case of R 50/57.5 (9) and R 50/57.5 (29), the total drying loads were observed to be actively mixed, and they were agglomerated or spread due to several changes in the outlines. When the drum temporarily stopped for a change in direction, we observed that the sample and the dummy loads agglomerated as they fell toward the bottom of the drum, and then they were spread out again by the centrifugal force when the rotation of the drum resumed.…”

“…The mechanism of drying fabric is based on mechanical movement, including the stress applied to the fabric by mechanical force, tension due to bending of the fabric, and deformation due to compression, friction, and interference between fabrics. 9 The drying process occurs as the moisture on the fabric surface between the yarns and on the fibers is diffused and desorbed and moves to the inside of the drum dryer. 10 Yun and Park 11 correlated fabric movement to drum rotational speed.…”