Thermowell Segmentation for Faster Thermal Response
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Solution Overview
Problem
Thermowells in process fluid measurement systems are intrusive, require regular evaluation, and increase response time due to their robust design, which is necessary for withstanding physical, thermal, and chemical challenges, but this slows responsiveness to temperature changes, especially in fast-changing processes.
Innovation Solution
A process fluid temperature measurement system using a thermowell with a thermally insulative collar and multiple temperature sensitive elements spaced by a spacer with known thermal conductivity, allowing for reduced thermowell length and improved responsiveness by inferring process fluid temperature through heat flux measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a robust thermowell design is used to withstand physical, thermal, and chemical challenges, then reliability is improved, but response time increases
Solution Approach 1:
The thermowell is divided into two distinct segments: an upper robust segment for mechanical protection and a lower slender segment for thermal response. This segmentation allows each part to optimize its function - the upper part withstands physical/chemical challenges while the lower part quickly responds to temperature changes.
Solution Approach 2:
Different parts of the thermowell have different structural qualities - the upper portion is robust and thick-walled for durability, while the lower portion is slender and thin-walled for fast thermal response. This local differentiation resolves the contradiction between reliability and response time.
2Measurement precision
If thermowell length is increased to ensure substantial thermal contact with process fluid, then measurement accuracy is improved, but response time increases
Solution Approach 1:
The thermowell is segmented into an upper robust segment and a lower slender segment. The lower segment's reduced length and minimized thermal mass enable faster response to temperature changes while the upper segment provides the necessary structural support and thermal contact area.
Solution Approach 2:
The lower portion of the thermowell has locally optimized properties - reduced thickness and length to minimize thermal mass for faster response, while the upper portion has increased thickness for structural strength and thermal contact.
3Strength
If thermowell is designed with thick walls to withstand physical and chemical challenges, then strength is improved, but thermal responsiveness decreases
Solution Approach 1:
The thermowell is divided into an upper robust segment with thick walls for strength and a lower slender segment with thin walls for thermal responsiveness. This segmentation allows the structure to be strong where needed while remaining thermally responsive at the sensor location.
Solution Approach 2:
The wall thickness is locally differentiated - thick in the upper portion for mechanical strength and chemical resistance, and thin in the lower portion for fast thermal conduction and responsiveness.
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 solution reduces the need for extensive thermowell inventory, minimizes response time, and maintains measurement accuracy by using a thermally insulative collar and multiple temperature sensors to calculate heat flux, enabling faster detection of temperature changes in process fluids.
Implementation Method 1
a thermally insulative collar
Implementation Method 2
spaced by a spacer with known thermal conductivity
Data Source
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AI summary
A process fluid temperature measurement system (300) includes a thermowell (200) configured to couple to a process fluid conduit and extend through a wall (102) of the process fluid conduit. A temperature sensor assembly (110) is disposed within the thermowell (200) and includes a first temperature sensitive element (304) and a second temperature sensitive element (306). The first temperature sensitive element (304) is disposed within the thermowell (200) adjacent a distal end (305) of the thermowell (200). The second temperature sensitive element (306) is spaced apart from the first temperature sensitive element (304) along a spacer (308) having a known thermal conductivity. Transmitter circuitry (311) is coupled to the first (304) and second temperature sensitive elements (306) and is configured to perform a heat flux calculation to provide a process fluid temperature output.