Thermal Mass Flow Meter with Inclination Sensor

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Solution Overview

Problem

Thermal mass flow meters and controllers face accuracy issues due to the 'recirculation effect' caused by orientation changes, leading to inaccuracies in fluid flow rate measurement, which existing designs attempt to mitigate but often require specific installation orientations.

Innovation Solution

A thermal mass flow sensor integrated with an inclination sensor that detects the angle of inclination relative to reference axes, allowing for compensation of inaccuracies such as recirculation, exterior, and density effects by calculating and applying correction factors to the output signal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the thermal mass flow meter is installed in a specific orientation to avoid recirculation effects, then measurement accuracy is improved, but installation flexibility and adaptability deteriorate

Engineering Contradiction:

Improveflow rate measurement accuracyVSAvoidinstallation orientation flexibility

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The system dynamically adapts to different installation orientations by using an inclination sensor to detect the actual orientation and a controller to calculate and apply appropriate correction factors to the measurement signal, allowing accurate measurements regardless of installation position

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the measurement parameters by applying orientation-dependent correction factors to compensate for recirculation effects, transforming the measurement process to account for gravitational and convective influences at different angles

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the thermal mass flow meter is designed to work in multiple orientations with compensation, then adaptability is improved, but device complexity increases due to additional sensors and processing

Engineering Contradiction:

Improveinstallation orientation flexibilityVSAvoidsystem structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The inclination sensor and correction algorithm provide universal adaptability across multiple installation orientations, allowing a single device design to function accurately in various positions without requiring orientation-specific hardware variants

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system replaces mechanical orientation constraints with an electronic/software-based solution using inclination sensing and digital signal correction, eliminating the need for mechanical alignment features or orientation-specific mounting configurations

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables accurate fluid flow rate measurement regardless of the installation orientation, reducing errors caused by recirculation, exterior, and density effects, and allowing for flexible use of the mass flow meter in various orientations.

Implementation Method 1

electrical current is provided to the two resistive windings 146D, 146E which are in thermal contact with the sensor measuring portion 146C. The heat generated by the resistive windings 146D, 146E is used to heat the fluid flowing therein

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

convective forces due to differences in temperature between the fluid in the sensor measuring portion and that in the bypass 142 and the force of gravity may give rise to a recirculation of fluid

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 3

at least one inclination sensor adapted to provide at least one second electrical signal indicative of an angle of inclination of at least one of the sensor inlet portion, the sensor outlet portion, and the sensor measuring portion relative to at least one reference axis

Methodology Applied

Scientific EffectInclination detection:

Implementation Method 4

a controller adapted to receive the first electrical signal and the at least one second electrical signal, calculate a correction factor based upon the at least one second electrical signal, and apply the correction factor to the first electrical signal

Methodology Applied

Scientific EffectSignal processing and correction:

Data Source

PatentUS7409871B2Mass flow meter or controller with inclination sensor

Publication Date: 2008.08.12 BROOKS INSTRUMENT LLC

AI summary

A thermal mass flow meter associated with an inclination sensor that detects an angle of inclination of at least one portion of a thermal mass flow sensor relative to at least one reference axis. Based upon the detected angle of inclination, the output signal of the mass flow meter that is indicative of the mass flow rate of fluid through the sensor may be compensated to account for any inaccuracies relating to the orientation in which the mass flow meter is installed. Inaccuracies for which compensation may be provided include thermal siphoning effects and fluid buoyancy effects. By compensating for such inaccuracies, the mass flow meter may be used in any orientation, and/or may be used in non-inertial (e.g., accelerating) environments. The flow meter may be used as a stand alone device, or incorporated in a thermal mass flow controller.