Thermocouple Fluid Temperature Measurement via Wire Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional thermocouple temperature measurements often inaccurately represent fluid temperatures due to differences in temperature, composition, and ambient conditions, leading to measurement discrepancies.
Innovation Solution
A method involving multiple thermocouples and instruments to measure temperatures at different positions on the thermocouple wires, discretizing the wires into elements, and solving energy conservation equations to accurately determine fluid temperature, reducing unknown variables and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional thermocouple is used to measure fluid temperature, then the measurement is simple and direct, but the measured temperature differs from the actual fluid temperature due to heat transfer effects
Solution Approach 1:
The thermocouple wire is divided into multiple discrete segments along its length, with each segment's energy balance independently formulated. This segmentation allows the complex heat transfer problem to be broken down into manageable differential equations that can be solved numerically, transforming a single-point measurement into a distributed measurement system that accounts for spatial temperature variations.
Solution Approach 2:
The measurement approach transitions from one-dimensional (single sensing point) to a distributed one-dimensional model along the wire length. By considering temperature distribution along the entire wire rather than at a single point, the method captures the spatial variation of temperature and heat transfer effects, enabling more accurate fluid temperature calculation through energy balance equations.
2Measurement precision
If multiple thermocouples and measurement positions are used to improve accuracy, then temperature measurement accuracy improves, but the device complexity and calculation requirements increase
Solution Approach 1:
The energy balance equations for all wire segments are formulated and prepared in advance, with the mathematical model structured to accept measurement data and directly compute fluid temperature. This preliminary formulation of the solution framework allows for efficient numerical solution when data is available, reducing computation time compared to iterative or experimental approaches.
Solution Approach 2:
The physical measurement system is complemented by a mathematical model that substitutes complex physical experimentation with numerical computation. Instead of using multiple physical thermocouples to directly measure fluid temperature through trial and error, the energy balance equations provide a direct computational path from measured wire temperatures to fluid temperature, reducing both physical complexity and calculation time.
3Strength
If the thermocouple size is increased, then the structural strength and durability improve, but the temperature measurement error increases
Solution Approach 1:
The method pre-calculates and stores the relationship between wire diameter and measurement error through the energy balance equations. By having this relationship established in advance, the system can compensate for the increased error introduced by larger wire sizes used for structural strength, allowing engineers to select wire dimensions that balance mechanical requirements with measurement accuracy without requiring trial and error.
Solution Approach 2:
The approach explicitly accounts for wire diameter as a variable parameter in the energy balance equations. By treating the wire size parameter as known and incorporating it into the mathematical model, the system can accurately calculate fluid temperature regardless of the wire dimensions used for structural strength, effectively decoupling the mechanical design constraints from the measurement accuracy.
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 approach enhances temperature measurement accuracy by accounting for various heat transfer mechanisms and reducing calculation time, allowing for precise fluid temperature determination in steady flow fields.
Implementation Method 1
The first wire between the first sensing junction and the first position is discretized into at least two first elements along its extension direction; the second wire between the first sensing junction and the second position is discretized into at least two second elements along its extension direction; energy conservation equations are established for the sensing junction of the first thermocouple, each first element, and each second element
Implementation Method 2
a convection heat transfer coefficient between the first wire and the fluid, and a convection heat transfer coefficient between the second wire and the fluid
Implementation Method 3
an emissivity of the first wire, an emissivity of the second wire, an absorbed irradiation by the first wire, an absorbed irradiation by the second wire
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A temperature measurement method, a probe, and a device for measuring fluid temperature are disclosed. For the temperature measurement method, a main thermocouple is placed in a fluid to obtain a first temperature, two auxiliary thermocouples are placed on the two wires of the main thermocouple respectively to obtain a second temperature and a third temperature. Applying multiple stimuli to the main thermocouple makes it experience multiple thermal equilibrium states. The first temperature, the second temperature, and the third temperature in each thermal equilibrium state are obtained. In each thermal equilibrium state, energy conservation equations are established for the main thermocouple, and the energy conservation equations of all thermal equilibrium states are solved together to obtain the fluid temperature. The present invention also provides the probe and the device for implementation of the method.