Total Temperature Probe Thermal Insulation
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Solution Overview
Problem
Conventional total temperature probes, such as the Kiel probe, face challenges in accurately measuring total temperature due to heat conduction issues and sensitivity to fluid flow parameters like Mach number and Reynolds number, leading to inaccuracies in temperature measurement.
Innovation Solution
A total temperature probe design featuring a hollow elongate shroud with inner and outer skins that create a thermal insulation pocket, where fluid flow is controlled through strategically displaced apertures to minimize heat transfer and maximize recovery factor, allowing for more accurate temperature measurement independent of fluid flow conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional Kiel probe with a single cavity and shroud is used, then the temperature sensor can measure fluid temperature, but heat conduction through the shroud wall causes the measured temperature to be lower than the total temperature
Solution Approach 1:
The probe divides the original single cavity into two separate cavities (first cavity for temperature sensing, second cavity for thermal insulation). The shroud wall is segmented into an inner skin and an outer skin with a stagnant air pocket between them, creating thermal barriers that reduce heat conduction loss while maintaining measurement accuracy.
Solution Approach 2:
A relatively stagnant air pocket is introduced as an intermediary thermal insulation layer between the inner skin and outer skin of the shroud wall. This air pocket acts as a thermal barrier that reduces heat conduction from the temperature sensor through the shroud wall, minimizing energy loss and improving measurement accuracy.
2Loss of energy
If the shroud wall is made thinner to reduce heat conduction, then heat transfer is reduced, but the structural integrity and thermal insulation effectiveness are compromised
Solution Approach 1:
The shroud wall is constructed with thin inner and outer skins that are structurally adequate but individually provide limited thermal insulation. The thermal insulation function is achieved not by thickening the skins but by introducing the stagnant air pocket between them, allowing the use of thin, structurally sound walls while maintaining thermal effectiveness.
Solution Approach 2:
The shroud wall is designed as a composite structure with three layers: an inner skin, a stagnant air pocket, and an outer skin. This composite construction provides both structural integrity from the skins and thermal insulation from the air pocket, achieving both strength and heat conduction reduction without compromising either.
3Device complexity
If the probe design is simplified to reduce complexity, then manufacturing is easier, but the ability to achieve high recovery factor independent of flow parameters is reduced
Solution Approach 1:
The probe is segmented into distinct functional zones: a first cavity for temperature sensing with controlled fluid access, a second cavity for thermal insulation, and a stagnant air pocket for heat barrier. This segmentation creates a modular structure that achieves high recovery factor independence while maintaining reasonable manufacturing complexity through clear functional separation.
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 probe achieves a high recovery factor that is substantially independent of Mach number and Reynolds number, providing more accurate and reliable total temperature measurements with improved thermal isolation and reduced heat conduction, enabling precise correction of measured temperatures.
Implementation Method 1
the shroud wall comprising an inner skin and an outer skin which enclose a second cavity therebetween... controls heat transfer along the temperature sensor and its mount stem by thermally insulating the base of the stem using a relatively stagnant air pocket
Implementation Method 2
fluid flow is received into the first cavity, passes through at least one aperture in the inner skin into the second cavity and thence passes out of the shroud through at least one aperture in the outer skin... relative displacement between the apertures or arrays of apertures promotes fluid flow and thus heat transfer
Implementation Method 3
a temperature sensor mounted in the first cavity... the temperature measured by the temperature sensor is closer to the total temperature
Data Source
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Figure 5
AI summary
A total temperature probe comprising a hollow elongate shroud defined by a shroud wall that envelops a first cavity. The shroud wall is comprised of an inner skin and an outer skin which enclose a second cavity therebetween. A temperature sensor mounted in the first cavity. In use, fluid flow is received into the first cavity, passes through at least one aperture in the inner skin into the second cavity and thence passes out of the shroud through at least one aperture in the outer skin. Beneficially, heat conduction across the inner skin is minimal.