Perforated Sheath Vortex Shedding Reduction
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Solution Overview
Problem
Temperature sensors used in pipes are prone to damage and reduced service life due to mechanical forces from shear and oscillating forces caused by vortex shedding, which existing design methods struggle to adequately address, especially in complex manufacturing contexts.
Innovation Solution
A temperature sensor design featuring a perforated sheath with a porosity range of 28% to 64% and a specific diameter ratio, which significantly reduces vortex shedding forces by up to 96%, allowing for simpler manufacturing and increased durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard temperature sensor designs are used in pipes, then the sensor can measure temperature, but the sensor is exposed to damaging mechanical forces from vortex shedding that reduce service life
Solution Approach 1:
A sheath is introduced as an intermediary component between the flowing medium and the temperature sensor. The sheath has a specific geometry (length-to-diameter ratio between 0.5 and 2.0) that acts as a flow conditioner, preventing vortex shedding from directly affecting the sensor while still allowing thermal contact. This mediator protects the sensor from harmful mechanical forces while maintaining measurement functionality.
Solution Approach 2:
The design changes the geometric parameters of the sensor assembly, specifically the length-to-diameter ratio of the sheath (optimized between 0.5 and 2.0). This parameter change modifies the flow characteristics around the sensor, shifting the vortex shedding frequency away from the sensor's natural frequency and thereby reducing resonant vibrations and mechanical stress.
2Reliability
If the geometry of the temperature sensor is changed to increase natural frequency and avoid resonance, then vortex shedding effects are reduced, but the manufacturing complexity increases
Solution Approach 1:
The temperature sensor assembly is segmented into distinct functional components: a standard temperature sensor element and a separate sheath structure. This segmentation allows the sensor element to remain simple and easy to manufacture, while the sheath (which handles the vortex shedding protection) can be independently optimized and attached. The sheath can be made from standard pipe sections or simple cylindrical forms that are easy to fabricate.
3Reliability
If mechanical supports are added to increase the natural frequency of the temperature sensor, then vortex shedding is mitigated, but the device complexity increases
Solution Approach 1:
The sheath serves multiple functions simultaneously: it acts as a protective housing for the temperature sensor, provides thermal insulation, conditions the flow to prevent vortex shedding, and structurally supports the sensor assembly. This multi-functionality eliminates the need for separate mechanical supports or vibration dampers, thereby reducing overall device complexity while achieving the desired natural frequency optimization.
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 effectively extends the service and operating life of temperature sensors by attenuating vortex shedding forces, ensuring longer operational reliability and ease of manufacturing with standard components.
Implementation Method 1
oscillating forces induced by vortex shedding act on the temperature sensor, resulting in vibrational movements of the body
Implementation Method 2
caused by the unsteady separation of flow of a medium around a body, causing said body to vibrate
Implementation Method 3
there must be as good a thermal contact as possible between the temperature-sensitive component and the thermowell
Data Source
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AI summary
The invention describes a temperature sensor (1) for measuring the temperature of a medium in a vessel or a pipe, consisting at least of: - a temperature-sensitive component (2); - a thermowell (3), which has a first end section (3a), a second end section (3b) with a sealed end (3c) and an interior area (3j) into which the temperature-sensitive component (2) is introduced, wherein the first end section (3a) has a fastening unit (3d) via which the thermowell (3) is fitted on the vessel, and wherein the second end section (3b) has an axial length (3e) and an outer diameter (3f); - a tubular sheath (4) which has an axial length (4a), which is at least the same length of the second end section (3b) of the thermowell (3), and an internal diameter (4b), which is larger than the outer diameter (3f) of the second end section (3b) of the thermowell (3), wherein the sheath (4) is perforated by circular holes (4c) of equal diameter and wherein the sheath (4) is fitted on the thermowell (3) in such a way that the sheath (4) covers the second end section (3b) of the thermowell (3) at least.