In this paper, an experimental approach for acoustic characterization of a household heat pump tumble dryer is developed. The main noise sources including BLDC motor, centrifugal fan, drain pump, and ...ventilation duct were identified using an acoustic camera survey based on beamforming, sound pressure level, directivity, and laser Doppler vibrometer vibration velocity measurements. In addition, noise reduction measures were taken, and sound power level and directivity measurements were used to evaluate the significance of the identified sources on the total noise emission. As a result, the A-weighted sound power level was reduced from 64.8 to 60.4 dB and the directivity pattern was improved. The proposed experimental approach for noise identification and the validation approach can be applied to other complex household appliances of similar size.
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 mass - the 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.
The use of heat pump tumble dryers is nowadays more common because they offer huge energy savings compared to conventional tumble dryers. Earlier studies made on conventional tumble dryers have shown ...that parameters such as heater power, fan speed, drum speed, weight and initial moisture content of textiles and air leakage have a huge impact on the energy efficiency and drying time. In the present study, a modified commercial heat pump tumble dryer was evaluated for energy consumption and drying time by changing operating parameters including fan speed, drum speed, and mass load. The total energy consumption and drying time were measured and corrected for the initial and final moisture content in the textiles. The experimental results based on 27 drying tests were evaluated to develop linear regression models for energy consumption and drying time, which show a good agreement with the experimental data. The results show that a large mass load, a high drum speed, and a low fan speed give the highest energy efficiency, i.e. the lowest energy consumption per kg of drying load. Larger loads extend the length of the drying cycle while higher fan and drum speeds result in shorter drying time.
The present study investigates fabric motion in the drum and its effect on performance parameters of a domestic heat pump tumble dryer in several operating points, defined by different load masses ...and drum speeds. Fabric motion in the drum was recorded by using a high-speed camera and evaluated statistically in order to determine the relation between the fabric distribution and the dryer performance parameters. Multiple regression analysis was performed to develop models for condensate mass flow rate as a function of drum speed, load mass, and drying stage. The results enable optimization of dryer operating parameters with respect to energy efficiency, drying time per kilogram of fabric, and condensate mass flow rate.
A heat pump tumble dryer model was developed to investigate the effects of evaporator geometry on drying time and energy consumption. The model was validated using experimental data available in the ...literature. The effects of the evaporator's geometrical specifications on heat and mass transfer and pressure drops on both sides of the evaporator were investigated. Then, the energy consumption and drying time of the dryer were determined. The results indicated that the energy consumption is reduced by 12% when the number of rows in the evaporator is increased from 2 to 4. Increasing the number of columns from 2 to 4 could reduce energy consumption by 8%. The energy consumption increases by 18% when the outer diameter of the tube is increased from 6 mm to 10 mm. Increasing the longitudinal tube pitch from 10 mm to 30 mm leads to a 21% increase in energy consumption.
•A heat pump tumble dryer model was developed.•The effects of evaporator geometry on dryer performance were investigated.•Heat and mass transfer and pressure drops of the evaporator were investigated.•Optimal geometrical specifications for the evaporator were determined.
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