Thermal Flow Meter Sensor Housing Thermal Isolation
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Solution Overview
Problem
Traditional thermal mass flow controllers (MFCs) face accuracy issues due to external temperature differentials, which cause thermal gradients that affect flow measurements, and existing solutions like central point attachment can lead to flexure and increased heat conduction to the sensor.
Innovation Solution
A novel sensor housing design with thermal isolation slots and a raised middle portion to minimize heat conduction and thermal gradients, using two lateral points for attachment to the base instead of a central point, reducing thermal contact and enhancing mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a central point attachment is used to mount the sensor housing to the base, then the housing is mechanically stable, but heat conduction to the sensor increases and flexure occurs
Solution Approach 1:
The housing attachment is segmented from a single central point to two lateral points, distributing the mechanical connection while reducing thermal conduction paths. This segmentation allows the housing to remain stable while minimizing heat transfer to the sensor.
Solution Approach 2:
The middle portion of the housing bottom is raised, extracting thermal contact from the central region where heat conduction would be most problematic. This creates a thermal isolation zone that reduces heat flow to the sensor while maintaining mechanical support at the lateral attachment points.
2Measurement precision
If thermal isolation slots are added to reduce heat conduction, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The housing is segmented by adding slots that divide the structure into distinct thermal zones. These slots create thermal barriers that reduce heat conduction to the sensor while maintaining the overall housing integrity and providing clear manufacturing instructions.
Solution Approach 2:
The slots are strategically positioned to create local thermal isolation zones around the sensor area, applying thermal management only where needed rather than requiring complete housing redesign. This localized approach improves measurement accuracy without excessive complexity.
3Loss of energy
If the middle portion of the housing bottom is raised, then thermal contact is reduced, but manufacturing complexity increases
Solution Approach 1:
The raised middle portion creates a localized feature that is simple to manufacture using standard molding or machining techniques. This local modification to the housing bottom geometry provides effective thermal isolation without requiring complex multi-piece constructions or specialized manufacturing processes.
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 design significantly reduces thermal gradients and heat conduction to the sensor, improving measurement accuracy and stability, achieving output variations below 0.1% of full scale and maintaining mechanical integrity.
Implementation Method 1
electrical current is provided to the two resistive windings 147, 148, which are in thermal contact with the sensor measuring portion 146C. The heat generated by the resistive windings 147, 148 is used to heat the fluid flowing therein
Implementation Method 2
A thermal mass flow controller or mass flow meter according to the present invention provides a novel sensor housing that reduces heat conduction from the housing mounting plate or base to the sensor itself
Data Source
AI summary
A thermal mass flow controller or mass flow meter having a novel sensor housing that reduces heat conduction from the housing mounting plate or base to the sensor itself. The housing also greatly minimizes the thermal gradient that can result from the uneven application of heat to the housing base. This reduction is accomplished in part by the use of one or more thermal isolation slots to isolate the upper portion of the housing (which holds the sensor) from the lower portion of the housing. Heat transfer to the sensor housing is also minimized by raising the middle portion of the bottom of the housing so that thermal contact is made between the base and the housing only at the two ends of the housing.