Asymmetric Trip Strip Layout to Prevent Thermal Saturation
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Solution Overview
Problem
Existing turbulated cooling passageways with skewed trip strips experience degraded heat transfer performance due to thermal saturation, especially in longer passages with large Length-to-diameter ratios (L/d > 20).
Innovation Solution
The implementation of a layout with periodic reflections of skewed trip strips along the flow passage, where the trip strips are oriented asymmetrically with respect to the flow direction and periodically altered in direction at a frequency of L/d ≤ 20, to prevent streamwise heat transfer decay and maintain efficient heat exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If skewed trip strips are used to reduce pressure loss, then pressure loss is reduced, but heat transfer performance degrades in long passages due to thermal saturation
Solution Approach 1:
The patent applies periodic action by alternating the skew direction of trip strips at regular intervals along the passage length. This periodic alternation prevents thermal saturation by periodically redistributing the thermal boundary layer, ensuring that fluid approaching the end wall does not become thermally saturated. The periodic pattern maintains heat transfer effectiveness while preserving the low pressure loss benefits of skewed trips.
Solution Approach 2:
The patent implements local quality by varying the skew direction of trip strips at different locations along the passage. Specifically, trip strips alternate between positive and negative skew directions in different sections, creating locally optimized flow patterns that prevent thermal saturation in specific regions while maintaining overall low pressure loss throughout the passage.
2Loss of energy
If asymmetric trip strip configuration is used, then pressure loss is reduced, but thermal saturation occurs at end walls leading to degraded heat transfer
Solution Approach 1:
The patent utilizes asymmetry by employing skewed trip strips with non-zero skew angles rather than symmetric perpendicular trips. The asymmetric skew configuration reduces pressure loss by aligning the trip strips with the flow direction. However, to counteract the resulting thermal saturation, the patent combines this asymmetry with periodic alternation of skew direction, creating a balanced solution that addresses both pressure loss and thermal saturation.
3Reliability
If trip strips are placed at an angle to flow direction, then heat transfer is enhanced, but asymmetric temperature profile develops causing thermal saturation
Solution Approach 1:
The patent applies periodic action by systematically alternating the skew direction of trip strips at regular intervals. This periodic alternation counteracts the development of asymmetric temperature profiles by periodically reversing the flow distortion pattern, preventing thermal saturation and maintaining temperature profile symmetry throughout the passage length.
Solution Approach 2:
The patent implements inversion by reversing the skew direction of trip strips in alternating sections. Instead of maintaining a constant skew direction that creates asymmetric temperature profiles, the patent inverts the skew direction periodically, causing the asymmetric thermal effects to cancel out over the passage length and preventing thermal saturation.
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 effectively prevents thermal saturation and maintains high heat transfer performance in longer passages by periodically altering the trip strip orientation, thereby mixing the flow and sustaining a temperature differential across the passage.
Implementation Method 1
In the flow past surface-mounted ribs, a boundary layer separates upstream and downstream of the ribs. These flow separations reattach the boundary layer to the heat transfer surface, thus increasing the heat transfer coefficient.
Implementation Method 2
The separated boundary layer enhances turbulent mixing, and therefore the heat from the near-surface fluid can more effectively get dissipated to the main flow, thus increasing the heat transfer coefficient.
Implementation Method 3
The separated boundary layer enhances turbulent mixing, and therefore the heat from the near-surface fluid can more effectively get dissipated to the main flow, thus increasing the heat transfer coefficient.
Data Source
AI summary
A layout for asymmetric trip strips including a flow passage having a lower wall and an upper wall opposite the lower wall, each of the lower wall and the upper wall including an inner surface, the flow passage having a passage inlet and a length L and a diameter d; multiple skewed trip strips extending from at least one inner surface of the lower wall or the upper wall; and at least one periodic reflection of the skewed trip strips along the flow passage downstream of the passage inlet at a frequency with a length-to-diameter ratio of L/d≤20.