Non-vaned Swirl Core Configurations for Nuclear Reactor Coolant
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Solution Overview
Problem
Existing coolant passage designs in nuclear reactors suffer from weak swirling flow due to straight passage walls, which limits heat transfer efficiency and increases the risk of Critical Heat Flux (CHF) onset, jeopardizing structural integrity.
Innovation Solution
Non-circular coolant passages with varying cross-section sizes and angular orientations, combined with twist rates and fillets, are designed to enhance swirling flow without the need for vanes or rifling, promoting more effective heat transfer and flow stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If straight passage walls are used in coolant passages, then manufacturing is simpler, but swirling flow velocity is weak (only approximately 1% of axial coolant flow velocity)
Solution Approach 1:
The patent applies curvature by transitioning from straight passage walls to twisted passage walls. The twist rate introduces a curved geometry that generates swirling flow in the coolant. This curvature principle directly addresses the contradiction by using geometric curvature to increase swirl velocity without adding complex mechanical components like vanes or rifling, thus maintaining manufacturing simplicity while achieving the desired flow characteristics.
2Speed
If vanes or rifling are added to increase swirling flow, then heat transfer effectiveness improves, but manufacturing constraints restrict physical access along the full length of coolant passages
Solution Approach 1:
The patent extracts the swirl-generating function from separate components (vanes or rifling) and integrates it directly into the passage wall geometry itself. By embedding the twist rate into the passage wall design, the invention eliminates the need for separate swirl-inducing components that would be difficult to manufacture and install. This integration resolves the manufacturing accessibility issue while maintaining the heat transfer benefits of swirling flow.
Solution Approach 2:
The patent merges the structural function of the passage wall with the flow-control function of vanes or rifling. The twisted passage wall simultaneously serves as both the coolant conduit and the swirl-generating element. This merging of functions eliminates the need for separate components, making manufacturing more accessible while achieving the desired swirling flow for enhanced heat transfer.
3Reliability
If non-circular coolant passages with varying cross-sections are used, then swirling flow and heat transfer are enhanced, but passage design complexity increases
Solution Approach 1:
The patent applies local quality by varying the cross-sectional dimensions and twist rate along the axial length of the passage. Different sections of the passage have different geometric properties optimized for local flow conditions. This gradual variation in local geometry enhances swirling flow and heat transfer effectiveness while maintaining structural integrity and preventing CHF, without requiring abrupt or complex design changes throughout the entire passage.
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 design significantly increases swirling flow velocity, delaying or preventing CHF onset and enhancing heat transfer efficiency, thereby maintaining safe operational temperatures within structural limits.
Implementation Method 1
Swirling coolant flow is one way to increase heat transfer and help prevent CHF onset in flowing coolant. Inducing swirling flow can delay and/or prevent the onset of CHF by creating a pressure gradient within a coolant passage. Swirling the coolant creates a pressure gradient towards the center of rotation.
Implementation Method 2
Swirling the coolant creates a pressure gradient towards the center of rotation. For example, in an internal flow configuration, swirling the coolant lowers pressure at the center of a passage relative to the pressure on passage walls.
Implementation Method 3
In single-phase heat transfer, swirling flow speeds up coolant velocity over passage walls, increasing heat transfer.
Implementation Method 4
The point at which the sudden heat transfer degradation occurs is referred to as the Critical Heat Flux (CHF) point, the Departure from Nucleate Boiling (DNB) point, and/or the dryout point. Swirling the coolant creates a pressure gradient towards the center of rotation... This keeps passage walls wetted with liquid coolant rather than coolant vapor, delaying or preventing the onset of CHF.
Data Source
AI summary
A non-circular coolant passage is disclosed, which includes one or more walls axially defining a flow path; an inlet connecting to a first end of the flow path; and an exit connecting to a second end of the flow path, wherein a size of a passage cross-section varies in the axial direction. In certain exemplary embodiments the passage cross-section size varies uniformly, while in others the passage cross-section size varies incrementally. In certain exemplary embodiments, an angular orientation of the passage cross-section varies in the axial direction. The cross-section angular orientation can vary uniformly, incrementally, or a combination of both. In still other embodiments, both the size of the passage cross-section and the angular orientation of the passage cross-section vary in the axial direction. In these embodiments, the passage cross-section size and/or the angular orientation of the passage cross-section can vary uniformly, incrementally, and/or a combination of the two.