Water Heater Element Descaling Using Combined AC and DC Voltage

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Solution Overview

Problem

Existing water heating devices face issues with scale formation on heating elements due to hard water, leading to performance degradation and potential device failure, with existing solutions involving chemical additives or physical methods that have limitations in efficacy and complexity.

Innovation Solution

An electrochemical method using a combination of AC and DC voltages applied between a heating element and a counter electrode, with the heating element as the positive electrode, to prevent or remove scale by controlling pH and oxidation reactions, effectively keeping the anode clean and preventing scale adherence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If DC voltage is applied to prevent scale formation, then scale prevention effectiveness is improved, but corrosion risk increases

Engineering Contradiction:

Improvescale prevention effectivenessVSAvoidcorrosion risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic reversal of electrode polarity through AC voltage, causing the heating element to alternate between anode and cathode roles. This periodic action prevents continuous oxidation and corrosion on the heating element surface while maintaining scale prevention effectiveness, directly resolving the contradiction between scale prevention and corrosion risk associated with DC voltage application.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the electrical parameter from pure DC to AC with specific frequency and voltage characteristics. By adjusting AC voltage amplitude and frequency, the system maintains effective scale prevention while the alternating polarity inherently reduces cumulative corrosion effects, thus resolving the contradiction through parameter optimization.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If higher voltage and current are used to improve scale removal, then scale removal effectiveness is improved, but corrosion risk increases

Engineering Contradiction:

Improvescale removal effectivenessVSAvoidcorrosion risk

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent utilizes periodic polarity reversal through AC voltage to enable higher current application during scale removal phases while limiting cumulative corrosion. The alternating current allows aggressive cleaning currents to be applied intermittently without causing continuous corrosion damage, resolving the contradiction between scale removal effectiveness and corrosion risk.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent maintains continuous application of electrical field with AC voltage, ensuring scale prevention acts continuously while the alternating polarity prevents corrosion accumulation. This continuous useful action with periodic polarity reversal enables sustained scale removal effectiveness without proportional increase in corrosion risk.

Inventive Principle:

Principle #20Continuity of useful action

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 method efficiently prevents and removes scale from heating elements, allowing for higher voltage and current usage compared to DC alone, reducing corrosion risks and maintaining device performance without chemical additives.

Implementation Method 1

heating element to heat aqueous liquid in the water heater

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

applying a first AC voltage between the heating element and a counter electrode, and applying a DC voltage between the heating element and the counter electrode, wherein the DC voltage is at least 0.5 V, especially at least 1.0 V, and wherein the heating element is chosen as positive electrode

Methodology Applied

Scientific EffectElectrochemical oxidation: Oxidation

Implementation Method 3

A principle could be to have two electrodes in the water connected with a DC power supply. At the anode (+ electrode) oxidation is taking place. At the cathode (- electrode) reduction is taking place

Methodology Applied

Scientific EffectElectrochemical scale prevention:

Data Source

PatentEP2596294B1Prevention or reduction of scaling on a heater element of a water heater

Publication Date: 2015.12.09 KONINKLIJKE PHILIPS NV

Figure 1a~1b
Figure 1c~1d
Figure 1e~1f

AI summary

The invention provides a method of using a water heater arranged for heating an aqueous liquid wherein the water heater comprises a heating element to heat aqueous liquid in the water heater. The method comprises (a) heating aqueous liquid in the water heater with the heating element), wherein the heating element is in contact with the aqueous liquid; and (b) applying a first AC voltage between the heating element and a counter electrode, and applying a DC voltage between the heating element and the counter electrode, wherein the DC voltage is at least 0.5 V, and wherein the heating element is chosen as positive electrode.