Bent Capillary Tubes for Pressure Difference Sensor Thermal Stress
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Solution Overview
Problem
Pressure difference sensors face accuracy and stability issues due to significant thermal expansion differences between materials, leading to bending loads that can corrupt or destroy the measuring cell.
Innovation Solution
The introduction of bent capillary tubes with a novel geometry, where the tubes either bend towards or away from each other, minimizes thermomechanical reactions by optimizing the thermal expansion coefficients of the platform, stiffening elements, and pressure difference measuring cell, thereby reducing thermal expansion-related stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If straight capillary tubes are used to connect the platform and stiffening elements, then the device structure is simple and easy to manufacture, but thermal expansion differences cause bending loads that corrupt pressure measurement signals and reduce accuracy
Solution Approach 1:
The capillary tubes are designed with bends instead of straight configurations. The bends allow the tubes to accommodate differential thermal expansion between the platform and stiffening elements, preventing bending loads on the pressure difference measuring cell while maintaining measurement accuracy.
Solution Approach 2:
The invention changes the geometric parameters of the capillary tubes by introducing bends at specific positions. This parameter change allows the system to compensate for thermal expansion differences without affecting the pressure measurement function, thereby resolving the contradiction between measurement precision and structural simplicity.
2Reliability
If straight capillary tubes are used, then the device is easy to manufacture, but thermal expansion differences can lead to destruction of the pressure difference measuring cell
Solution Approach 1:
The bent configuration of the capillary tubes provides mechanical compliance to absorb thermal expansion stresses, preventing cell destruction over time. While the fabrication process becomes slightly more complex, the design ensures long-term reliability by eliminating the risk of thermal stress-induced failure.
Solution Approach 2:
The bends in the capillary tubes act as pre-designed stress absorption elements that cushion against thermal expansion forces before they can reach and damage the pressure difference measuring cell, thereby ensuring long-term stability.
3Adaptability or versatility
If the platform material has high thermal expansion coefficient, then the platform can be made from common materials like stainless steel, but it expands significantly more than the measuring cell during temperature changes causing bending loads
Solution Approach 1:
The invention explicitly utilizes thermal expansion principles by designing bent capillary tubes that accommodate the differential expansion between the platform and stiffening elements. The bends allow the system to handle materials with different thermal expansion coefficients without compromising mechanical stability.
Solution Approach 2:
By changing the geometric parameters of the capillary tube path (introducing bends), the system can work with common platform materials like stainless steel while compensating for their higher thermal expansion coefficients, thereby maintaining mechanical stability across temperature variations.
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 enhances mechanical stability and maintains the accuracy of pressure measurement signals by minimizing thermomechanical reactions, potentially preventing cell destruction and ensuring long-term stability.
Implementation Method 1
the platform expands significantly more than the composite of stiffening element and pressure difference measuring cell, since the thermal expansion coefficient of the platform material is significantly greater than that of the material of the pressure difference measuring cell, and the material of the stiffening element
Data Source
AI summary
A pressure difference sensor for providing a pressure measurement signal, comprising: a pressure difference measuring cell, which is suppliable with first and second pressures and which outputs the pressure measurement signal; first and second ceramic stiffening elements, each of which is joined with the pressure difference measuring cell and has a duct, via which the first, respectively the second, pressure is suppliable to the pressure difference measuring cell; a platform with first and second pressure input openings, each of which extends from a first surface to a second surface of the platform, wherein the pressure input openings are sealed on the first surface, each with its own isolating diaphragm, and first and second pressures tubes, which are arranged between the stiffening elements and the platform, and wherein each of the first pressure tube and the second pressure tube has at least one bend in a region between the platform and a first, respectively second, connecting area of the corresponding pressure tube.