Washing Machine Heating Control for Bleach-Active Laundry Temperature
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Solution Overview
Problem
In domestic washing machines, large loads and high fill ratios lead to a significant temperature gradient between the washing liquor and laundry, resulting in a mean laundry temperature below 50°C, which is inadequate for effective bleach activation, necessitating extended wash times to achieve proper cleaning.
Innovation Solution
A program-controlled washing machine that captures specific parameters related to the laundry items and appliance, using an expert system to control heating and adjust energy input, ensuring a tailored wash temperature and uniform heating process, with predefined temperature peaks and hysteresis adjustments to maintain the target temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heating is extended to raise laundry temperature, then cleaning performance improves, but wash time increases significantly
Solution Approach 1:
The heating element is positioned to directly contact the laundry items before the washing liquor is introduced. This preliminary direct heating action raises the laundry temperature to the required level (above 50°C for bleach activation) before the main wash cycle begins, eliminating the need for extended heating periods during the wash cycle.
Solution Approach 2:
The heating process is divided into distinct phases: initial direct heating of laundry, followed by introduction of washing liquor, and then periodic temperature maintenance. This periodic approach allows the system to achieve target temperatures efficiently while maintaining them throughout the wash cycle without continuous extended heating.
2Productivity
If heating power is increased to reduce wash time, then energy consumption increases
Solution Approach 1:
High-power heating is applied only during the preliminary phase when the heating element directly contacts the laundry. This concentrated energy input achieves rapid temperature rise without requiring sustained high-power heating throughout the entire wash cycle, thus reducing total energy consumption while improving productivity.
Solution Approach 2:
The heating element maintains continuous thermal contact with the laundry throughout the wash cycle, ensuring that heat is continuously transferred without interruption. This continuous useful action allows for more efficient energy utilization compared to intermittent heating, reducing total energy consumption while maintaining effective wash temperatures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for shorter wash times while maintaining effective cleaning performance, ensuring the mean wash temperature is consistently above the minimum required for bleach activation, even with large loads, thereby optimizing wash efficiency and reducing overall wash duration.
Implementation Method 1
a heating unit to heat the washing liquid to a wash temperature
Implementation Method 2
The washing liquor is heated by the heating element. When the drum moves, other laundry items come into contact with the heated washing liquor. The laundry is heated by means of the exchange between the free and bound liquor.
Implementation Method 3
The laundry is heated by means of the exchange between the free and bound liquor
Data Source
AI summary
A method for washing laundry in a program-controlled domestic laundry-care appliance including the steps of heating washing liquid present in the tub and heating the washing liquid to a specific washing temperature set as a function of determined parameter values that are specific to the laundry being washed and/or the appliance.