Wound Heat Exchanger Capillary Bundle Design
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Solution Overview
Problem
Existing capillary tube bundle manufacturing techniques for extracorporeal blood circuit heat exchangers are costly and lack direct control over production parameters, leading to suboptimal heat transfer rates and pressure drop performance due to fixed tube sizes and orientations.
Innovation Solution
A capillary tube bundle sub-assembly is created using a substrate core with continuous capillary tubing wound in a manner that allows each layer to be non-parallel and spiraling less than 360°, with varying pitch directions and angles between layers to prevent nesting and optimize packing fraction and shear rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capillary tube mats are knitted or woven together with threads, then the tubes are held together to form a bundle, but the manufacturing process becomes complex and expensive
Solution Approach 1:
The patent removes the knitting or weaving threads from the capillary tube bundle construction, extracting the problematic element that caused manufacturing complexity and expense while maintaining tube bundle integrity through alternative means
Solution Approach 2:
The patent divides the capillary tubes into discrete segments that are individually positioned and secured at specific locations along the tube length, replacing the continuous threading approach with localized attachment points that simplify manufacturing
2Ease of manufacture
If capillary tube size and orientation are fixed in the mat structure, then manufacturing is simplified, but heat transfer rates and pressure drop performance cannot be optimized
Solution Approach 1:
The patent introduces variability in capillary tube orientation and spacing along the length of the tube, allowing the structure to adapt to optimize heat transfer and flow characteristics at different positions rather than maintaining fixed uniform parameters throughout
Solution Approach 2:
The patent applies different tube orientations, spacing, and configurations at different locations within the bundle, enabling local optimization of heat transfer performance and pressure drop characteristics according to specific operational requirements
3Quantity of substance
If capillary tubes are wound in parallel layers, then packing density is maximized, but interlayer nesting occurs reducing heat exchange efficiency
Solution Approach 1:
The patent introduces asymmetric angular offsets between adjacent capillary tube layers, preventing symmetric nesting patterns that would reduce heat exchange efficiency while maintaining high packing density through optimized angular relationships
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 reduces costs, allows for direct control over production parameters, and enhances heat transfer rates and pressure drop performance by preventing interlayer nesting and optimizing fluid flow characteristics.
Implementation Method 1
heat transfer occurs between the blood and the heat exchange fluid
Implementation Method 2
enhances heat transfer rates and pressure drop performance by preventing interlayer nesting and optimizing fluid flow characteristics
Data Source
AI summary
A capillary tube bundle sub-assembly for use in an extracorporeal heat exchanger includes a continuous capillary tubing wound about a core to define a plurality of capillary layers each including a plurality of capillary segments. The capillary segments each define opposing terminal ends adjacent opposing ends of the core. The capillary segments of each layer are circumferentially aligned relative to an axis of the core, with each successive layer being radially outward of an immediately preceding layer. The capillary segments are non-parallel with the axis, spiraling partially about the axis in extension between the opposing terminal ends. Each capillary segment forms less than one complete revolution (i.e., winds less than 360°). The segments within each layer are substantially parallel with one another; however, an orientation of the segments differs from layer-to-layer such as by pitch or angle.