Dual-Purpose Resistive Heater for Sensorless Fluid Flow Measurement

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Solution Overview

Problem

Existing heating and sensing systems for fluid flow applications, such as vehicle exhaust systems, face challenges due to harsh environmental conditions like vibration and thermal cycling, leading to instability and potential damage to physical sensors. Additionally, external sensors introduce delays and increase the risk of component failure.

Innovation Solution

A control system that incorporates a heater with resistive heating elements and a control device capable of determining fluid flow characteristics based on heat loss from the heating elements. This system calculates mass flow rates and fluid temperatures by analyzing changes in resistance under specific heat flux densities, allowing for more accurate and reliable fluid flow measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If physical sensors are used in harsh environments, then temperature measurement is achieved, but sensor stability and reliability deteriorate due to vibration and thermal cycling

Engineering Contradiction:

Improvetemperature measurementVSAvoidsensor stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent combines the heating element and temperature sensor into a single integrated unit. The heating element serves dual purposes: generating heat and sensing temperature through its electrical resistance. This eliminates the need for separate physical sensors that would be vulnerable to vibration and thermal cycling damage.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The heating element is designed to perform multiple functions simultaneously: it acts as both a heater and a temperature sensor. By measuring the electrical resistance of the heating element, the system obtains temperature information without requiring additional sensing components that could fail in harsh environments.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If external sensors are used for temperature control, then temperature monitoring is achieved, but system response time deteriorates due to thermal resistances in sensor wires

Engineering Contradiction:

Improvetemperature monitoringVSAvoidsystem response time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The temperature sensing function is merged directly into the heating element itself. Since the heating element is already in direct thermal contact with the fluid, it provides immediate temperature feedback without the thermal lag introduced by external sensor connections and wiring.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces mechanical/physical sensor connections with an electrical measurement approach. By measuring the electrical resistance of the heating element, temperature is determined without requiring physical sensor wires that introduce thermal resistance and time delays.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If safety margins are applied in heater design, then risk of heater damage is reduced, but heater power density decreases requiring larger heater size

Engineering Contradiction:

Improveheater safetyVSAvoidheater power density

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The integrated temperature sensing provides real-time feedback on the actual temperature at the heating element. This allows the control system to adjust power delivery dynamically, maintaining safe operating temperatures while maximizing heater power density without requiring excessive safety margins that would reduce efficiency.

Inventive Principle:

Principle #23Feedback

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 system provides improved reliability and accuracy in fluid flow measurements, reduces the risk of sensor damage, and enhances the overall performance of heating systems in harsh environments by utilizing the heating elements as both heating and sensing components.

Implementation Method 1

a heater operable to heat a fluid flow, where the heater includes at least one resistive heating element

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

A control system that incorporates a heater with resistive heating elements and a control device capable of determining fluid flow characteristics based on heat loss from the heating elements

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 3

This system calculates mass flow rates and fluid temperatures by analyzing changes in resistance under specific heat flux densities

Methodology Applied

Scientific EffectResistive temperature detection: Electrical Resistance

Data Source

PatentUS12326107B2Dual-purpose heater and fluid flow measurement system

Publication Date: 2025.06.10 WATLOW ELECTRIC MANUFACTURING CO

AI summary

A control system for use in a fluid flow application includes a heater and a control device. The heater includes at least one resistive heating element having a relationship between resistance and temperature defining a non-monotonic curve. The heater is to heat fluid flow. The control device is to determine a flow characteristic of the fluid flow and a temperature of the at least one resistive heating element along the non-monotonic curve between resistance and temperature based on a change in resistance of the at least one resistive heating element.