Dishwasher Circulating Heater Switching for Low-Flow Noise Control
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Solution Overview
Problem
Existing dishwasher heating systems face issues when operating at low water flow rates, as they tend to boil and produce unwanted noise due to insufficient cooling, and require complex control systems or high costs for precise zero crossing or phase angle control.
Innovation Solution
A heating device with at least two resistance heaters, operated via a switching device with two states, allowing the heaters to be connected in series or independently, enabling efficient power consumption and long heating pulses without boiling, using simple switching components like relays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the continuous-flow heater operates with fewer or shorter heating pulses to reduce average heating output at low flow rates, then power consumption is reduced, but service life and controllability deteriorate
Solution Approach 1:
The heating device is segmented into multiple independent heating elements (first heating element, second heating element, third heating element) that can be operated independently or in combination. This allows selective activation of only the necessary heating elements based on required power output, reducing overall power consumption while maintaining service life through distributed thermal stress.
2Use of energy by moving object
If fewer but longer heating pulses are used to reduce average heating output, then power consumption is reduced, but water boiling and noise increase due to insufficient cooling
Solution Approach 1:
Multiple heating elements are distributed along the water flow path, allowing heat to be applied at different locations. This distributes the thermal load and prevents localized overheating that would cause water boiling and noise, while still achieving the required average power reduction.
Solution Approach 2:
The heating elements are activated in periodic sequences rather than continuously. By alternating between different heating elements or cycling their activation, the system maintains lower average power output while ensuring adequate cooling periods that prevent water boiling and noise generation.
3Measurement precision
If zero crossing or phase angle control with electronic switches is used to solve the heating control problem, then heating control precision is improved, but cost and calibration effort increase
Solution Approach 1:
The system uses the existing mains power frequency (50Hz or 60Hz) as a natural clock signal for periodic heating element activation. This eliminates the need for separate electronic timing circuits or phase angle control systems, achieving adequate heating control precision through simple periodic switching that synchronizes with the power supply frequency.
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
Enables operation over a wide power range without noise or overheating, ensuring efficient heating and extended service life by adjusting power consumption based on switching states, suitable for both normal and steam operation modes.
Implementation Method 1
a heating device (3) for water with a clocked control (1) for the heating device (3) for operating the continuous-flow heater (3) at different outputs
Implementation Method 2
the first and second resistance heaters are electrically connected in series and the series circuit that is created in this way is operated with the supply voltage
Data Source
Figure 1
AI summary
The appliance has a heating device (3) e.g. passage heater, for water, and a clocked control (1) for operating the heating device during different outputs. The heating device is provided with resistance heaters (5, 6), and a switching device (4) is provided with two switching states, where the heaters are electrically operable in series with a given supply voltage in the switching states. The heaters are electrically arranged in series between a neutral conductor (N) and a phase (L1) in one of the states. The switching device is provided with a neutral conductor switch.