Dishwasher Water Inlet Control for Variable Hot Water Temperature
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Household dishwashers face inefficiencies in energy and water usage due to the reliance on external hot water supplies, which can lead to increased operating costs and suboptimal cleaning and drying results, especially when using solar thermal systems that provide variable hot water temperatures.
Innovation Solution
A dishwasher with a bi-thermal water inlet system and temperature measurement capabilities allows for precise control of hot and cold water intake during wash cycles, using a temperature sensor to adjust the ratio of hot to cold water based on the measured temperature of the incoming hot water, thereby optimizing the temperature of the washing liquor and reducing the need for electrical heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If hot water from external supply is used for washing, then energy consumption is reduced, but water temperature varies leading to suboptimal cleaning results
Solution Approach 1:
The system dynamically adjusts the water temperature parameter by mixing hot water from external supply with cold water from internal supply. The control unit calculates the required amounts based on measured external hot water temperature and program requirements, ensuring consistent washing temperature despite variations in external hot water supply temperature.
Solution Approach 2:
The system measures the actual temperature of hot water from the external supply using a temperature sensor, feeds this information back to the control unit, and adjusts the mixing ratio of hot and cold water accordingly. This closed-loop control ensures reliable cleaning results despite variations in external water supply temperature.
2Loss of energy
If hot water from solar thermal system is used, then operating costs are reduced, but temperature control precision deteriorates
Solution Approach 1:
The system performs preliminary measurement of the external hot water temperature before the washing cycle begins. Based on this advance knowledge, the control unit calculates the precise amounts of hot and cold water needed to achieve the target washing temperature, enabling precise temperature control from the start of the cycle.
Solution Approach 2:
The system dynamically adjusts the water intake parameters during the filling phase based on measured temperature conditions. The control unit continuously monitors and adjusts the mixing ratio of hot and cold water to maintain precise temperature control, adapting to variations in solar thermal system output.
3Temperature
If mixed water temperature is regulated by throttling hot water and increasing cold water, then setpoint temperature is reached, but water intake time increases
Solution Approach 1:
The system performs preliminary measurement of external hot water temperature and pre-calculates the optimal mixing ratio before the water intake phase. This advance preparation allows the system to intake the precise amounts of hot and cold water in one operation, reaching the setpoint temperature faster than sequential adjustment methods.
Solution Approach 2:
The system changes the water intake parameters based on measured temperature conditions. Instead of using fixed throttling ratios, the control unit adjusts the intake parameters dynamically to optimize the heating process and reduce water intake time while achieving the target temperature.
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 enhances the efficiency of wash cycles by minimizing energy consumption, optimizing water usage, and ensuring consistent cleaning and drying results across varying ambient conditions, while preventing damage to items from excessive temperatures.
Implementation Method 1
a temperature sensor for measuring the temperature of the hot water from the external hot water supply
Implementation Method 2
a water inlet device which has a hot water valve that can be controlled by the control device and a cold water valve that can be controlled by the control device
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The dishwasher (1) has a temperature sensor (27) arranged downstream of a water inlet device (11). A wash program provides a wash step, where the wash step includes an intake phase for taking in water via the water inlet device. A spraying phase sprays a set of items to be washed with a washing liquor (S) containing the water that is taken in via the water inlet device. The wash program includes a phase of the intake phase during which hot water is taken in via a hot-water valve (12) and temperature of the hot water is measured by the sensor. The temperature sensor is negative temperature coefficient (NTC) thermistor. An independent claim is also included for a method for executing a wash cycle with a dishwasher.