Thermal Exchange Coefficient Measurement Using Wall Temperature Gradients
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Solution Overview
Problem
Existing methods for determining the thermal exchange coefficient between a fluid and a pipe wall are inadequate, particularly for turbulent fluids with large temperature differences and in the presence of non-condensable gases, as they require direct measurement or integrated surface measurements, which are not feasible in industrial applications.
Innovation Solution
A device with two wall temperature sensors and a fluid temperature sensor, along with a computer algorithm, calculates the thermal exchange coefficient locally by measuring temperature differences and thermal flow, using thermal conductivity to determine the coefficient without external heat interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mathematical exchange correlation models (Colburn, Dittus-Boelter, Rosenhow) are used to determine thermal exchange coefficient, then the measurement can be performed using standard sensors, but the method becomes unsuitable for turbulent fluids with large temperature differences, non-condensable gases, and fluid vortices
Solution Approach 1:
The patent replaces mathematical correlation models with a direct physical measurement method using temperature sensors and heat flow calculations. Instead of relying on empirical formulas that fail under certain conditions, the invention uses actual temperature measurements at the wall and in the fluid combined with thermal conduction equations to directly calculate the thermal exchange coefficient, making it applicable to turbulent flows, large temperature differences, and conditions with non-condensable gases.
2Measurement precision
If external heating is applied to measure thermal exchange coefficient, then the measurement can be performed, but external heat addition interferes with the measurement
Solution Approach 1:
The patent employs passive measurement where the natural heat transfer between the fluid and pipe wall is measured without external intervention. Temperature sensors measure the existing temperature distribution, and the thermal exchange coefficient is calculated from these natural conditions, eliminating interference from external heating while still enabling accurate measurement.
3Area of stationary object
If integrated surface measurement is performed, then the entire surface can be characterized, but local measurement precision is lost
Solution Approach 1:
The patent implements local measurement by positioning temperature sensors at specific locations on the pipe wall and in the adjacent fluid. The thermal exchange coefficient is calculated locally at each sensor position, providing spatially-resolved data that characterizes heat transfer variations across different regions of the pipe, enabling identification of local anomalies such as hot spots or flow separation zones.
4Measurement precision
If multiple temperature sensors are positioned far apart in the wall thickness direction, then the temperature difference measurement is improved, but the measurement is no longer localized
Solution Approach 1:
The patent resolves the localization conflict by using sensors arranged in a specific spatial configuration where two wall sensors are positioned at different depths but laterally aligned, and a fluid sensor is positioned adjacent to the wall surface. This three-dimensional arrangement allows calculation of local thermal exchange coefficient at a specific lateral position while maintaining sufficient temperature difference measurement capability through the wall thickness direction.
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 allows for precise, non-intrusive, and localized measurement of the thermal exchange coefficient, providing accurate results even in challenging industrial conditions, with minimal disturbance to the pipe and facilitating integration within the pipe.
Implementation Method 1
a first temperature sensor measuring a first temperature value TC1 of a wall at a point P1
Implementation Method 2
a second temperature sensor measuring a second temperature value TC2 of the wall at a point P2
Implementation Method 3
a fluid temperature sensor measuring a temperature value TF of the fluid at a point PF
Implementation Method 4
first means for calculating, from the temperature values TC1 and TC2, a temperature value Tp of the wall and a thermal flow Φ given by the following equation: Φ=−λgrad (TC1−TC2), where λ is the thermal conductivity of the wall
Implementation Method 5
second means for calculating, from fluid temperature TF, temperature TP and thermal flow Φ the thermal exchange coefficient h in the following form: h=Φ(TF−TP)
Data Source
AI summary
A device for determining the thermal exchange coefficient between a fluid and a wall at a point PN of a surface of the wall in contact with the fluid, including a measuring device (DT) which measures at least two temperature values TC1 and TC2 of the wall and a temperature value TF of the fluid, and a computer for calculating, from the temperature values TC1 and TC2, a temperature value Tp of the wall and a thermal flow Φ given by the following equation:Φ=−λgrad (TC1−TC2),where λ is the thermal conductivity of the wall, and for calculating, from the fluid temperature TF, the average temperature TP and the thermal flow φ the thermal exchange coefficient h in the following form:h=Φ/(TF−TP).