Water Heater Sensor Isolation with Thermal Lag Compensation

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Solution Overview

Problem

Conventional water heaters with metallic temperature sensors are expensive due to the high cost of materials like brass and copper, which are used for good thermal conductivity, necessitating a less expensive yet effective temperature sensor configuration.

Innovation Solution

A water heater with a temperature sensor that is at least partially thermally isolated from the water, using a non-metallic well or a polymeric body, and a controller that compensates for thermal isolation by processing temperature signals to determine a command temperature, potentially using first, second, or third-order lag models.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a metallic well (brass or copper) is used to thermally engage the temperature sensor with water, then thermal conductivity and temperature measurement accuracy are improved, but material cost increases

Engineering Contradiction:

Improvetemperature measurement accuracyVSAvoidmaterial cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces expensive metallic wells (brass or copper) with a less expensive polymeric well that is thermally isolated from direct water contact. The polymer well provides sufficient thermal conductivity for temperature sensing while dramatically reducing material costs, accepting that it will degrade over time but replacing it is more economical than maintaining expensive metal components

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent introduces a polymeric well as an intermediary between the temperature sensor and water. This intermediary provides thermal coupling sufficient for accurate temperature measurement while being cost-effective and corrosion-resistant, eliminating the need for direct metal-to-water thermal engagement

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the temperature sensor is thermally isolated from water using non-metallic materials, then material cost decreases, but thermal conductivity and temperature tracking accuracy worsen

Engineering Contradiction:

Improvematerial costVSAvoidtemperature tracking accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent changes the thermal parameters of the sensing system by using a polymeric well with specific thermal conductivity properties. The controller compensates for the reduced thermal conductivity by adjusting the thermal coupling parameters and using lag compensation algorithms to maintain accurate temperature tracking despite the non-metallic material

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements feedback control where the controller continuously monitors the temperature sensor output and compares it with expected water temperature behavior. When thermal lag is detected due to the polymeric well isolation, the controller adjusts heating cycles to compensate, ensuring accurate temperature control despite the thermal isolation

Inventive Principle:

Principle #23Feedback

3Ease of manufacture

If a polymeric body is used to accommodate the temperature sensor, then manufacturing complexity and assembly ease are improved, but thermal isolation increases

Engineering Contradiction:

Improveassembly easeVSAvoidthermal isolation

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent uses a thin polymeric well that provides structural accommodation for the temperature sensor while minimizing thermal resistance. The thin-walled polymer structure allows sufficient heat transfer from water to sensor, balancing manufacturing ease with thermal coupling requirements

Inventive Principle:

Principle #30Flexible shells and thin films

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

The solution provides a cost-effective temperature sensor configuration that maintains accurate water temperature control by accounting for thermal isolation, ensuring efficient heating cycles while reducing material costs.

Implementation Method 1

a heating source that is disposed proximate the water tank such that the heating source may heat water within the water tank

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a temperature sensor that is at least partially thermally isolated from the water in the water tank

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

A command temperature, which may be different from the temperature signal received from the at least partially thermally isolated temperature sensor in time and/or magnitude may be determined by processing the temperature signal received from the at least partially thermally isolated temperature sensor to account and/or compensate for the thermal isolation of the temperature sensor

Methodology Applied

Scientific EffectThermal lag:

Data Source

PatentUS8770152B2Water Heater with partially thermally isolated temperature sensor

Publication Date: 2014.07.08 RESIDEO LLC

AI summary

A water heater having a water tank and a heating source disposed proximate to the water tank such that the heating source may heat water within the water tank. A temperature sensor is provided that is partially thermally isolated from the water in the water tank. A controller may be provided that at least partially compensates for the partial thermal isolation of the temperature sensor and regulates the heating source. In some instances, the temperature sensor may be at least partially disposed within a thermally isolating mass.