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Washing machines are one of the most energy and water demanding domestic appliances. Over years, a significant effort of the scientific community has been invested into making laundry more "sustainable". Nevertheless, the preparation of detergent solution has been entirely overlooked step of laundering. The preparation of aqueous detergent solutions in the currently available washing machines takes up to 10 minutes. In this work, we propose a design of a special rotary hydrodynamic cavitation generator, which would impact this process. New detergent dissolution rates have been experimentally tested on the laboratory model washing machine using the designed cavitation generator. The dissolution rates have been determined from the measurements of the undissolved detergent after the specific time of treatment. Additionally, the influence of hydrodynamic cavitation on that process has been isolated and investigated. To do so, two flow regimes have been established: the regime with cavitation present and the regime where cavitation was not present. In order to evaluate cavitational intensity, pressure oscillations inside cavitation generator have been recorded. Results indicate that cavitation significantly increases the detergent dissolution rates. In the cavitation flow regime, more than 80 % of the detergent is dissolved in approximately 10 seconds. With no cavitation present, about 150 seconds are needed to dissolve the same amount of the detergent. Intensification of the process can be attributed to mechanical effects of cavitation. This research shows that use of the cavitation generators in the washing machines could lead to shorter washing programs and henceforth potential water and energy savings. Highlights• Hydrodynamic cavitation was used to prepare aqueous detergent solution.• Special rotary hydrodynamic cavitation generator was designed.• Cavitation significantly improves detergent dissolution rates. • Cavitation generators could improve water and energy efficiency of washing machines.

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