Thermal Flowmeter Channel Structure for Corrosion-Resistant Microflow Sensing
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Solution Overview
Problem
Conventional thermal type flowmeters using glass substrates for channels suffer from low corrosion resistance against alkaline liquids, and require high machining accuracy to connect inflow and outflow channels accurately, leading to potential pressure loss and flow disturbances, which affect measurement accuracy.
Innovation Solution
The flowmeter uses a resin channel member with a resin channel member having a first groove for measurement, where the inflow and outflow channels have diameters larger than the groove width, and a plate member made of sapphire or glassy carbon for enhanced corrosion resistance, with an annular seal to prevent leakage, and a sensor unit positioned for stable liquid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a glass substrate is used for the channel, then the channel has good chemical stability, but the corrosion resistance against alkaline liquids deteriorates due to neutralization reaction with silicon dioxide
Solution Approach 1:
The invention uses a composite structure combining resin material for the channel body (providing corrosion resistance) with a glass substrate containing the temperature-controlled section (providing chemical stability and thermal properties). This composite approach allows each material to contribute its advantageous properties while mitigating their respective disadvantages.
2Measurement precision
If the groove width is reduced to measure micro-flow rate, then the flow rate measurement range improves, but the machining accuracy requirement deteriorates for connecting inflow and outflow channels
Solution Approach 1:
The invention divides the channel structure into functionally distinct segments: the groove section for flow rate measurement and the inflow/outflow channel sections for liquid transport. This segmentation allows each part to be optimized independently - the groove can be made narrow for micro-flow measurement while the connecting channels can have larger diameters for easier machining and better connection reliability.
Solution Approach 2:
The invention applies different dimensional characteristics to different parts of the channel system. The groove has a small width (0.2-1mm) optimized for micro-flow measurement, while the inflow and outflow channels have larger diameters (0.5-2mm) optimized for easy connection and reduced pressure loss. This local differentiation of dimensions resolves the contradiction between measurement precision and manufacturing ease.
3Manufacturing precision
If the inflow and outflow channels are connected with high machining accuracy to match groove center, then the connection precision improves, but the device complexity and manufacturing difficulty deteriorates
Solution Approach 1:
The invention applies different dimensional specifications to different channel sections. The groove maintains a precise small width for measurement accuracy, while the inflow and outflow channels use larger diameters that are more tolerant to machining variations. This local differentiation reduces the overall manufacturing difficulty while maintaining measurement precision.
Solution Approach 2:
The invention uses a slightly excessive channel diameter (larger than the groove width) at the connection points. This excessive dimension provides a margin of error that compensates for machining inaccuracies, allowing connections to be made more easily without compromising the precision of the measurement section.
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 configuration enables easy formation and accurate measurement of flow rates with enhanced corrosion resistance against alkaline and acidic liquids, reducing pressure loss and flow disturbances, and improving measurement accuracy.
Implementation Method 1
transfers heat to a liquid subjected to measurement from the heat transfer component via the glass substrate
Data Source
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AI summary
Provided is a thermal type flowmeter including: a resin channel member; a plate member defining, together with the channel member, a measuring channel used for measuring a liquid flow rate; and a sensor unit having a heating resistor that transfers heat to the plate member and a temperature detecting resistor that determines a temperature of the plate member. The channel member includes a flat surface in which a first groove is formed, an inflow channel having a circular cross section connected to one end in axis direction along the axis of the first groove, and an outflow channel having a circular cross section connected to the other end in the axis direction of the first groove, and inner diameters of positions of the flat surface at which the inflow channel and the outflow channel are opened, respectively, are larger than the width of the first groove.