Flattened Heat Exchanger Tube With Blocked Bypass Channels
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Solution Overview
Problem
Heat exchangers with flattened tubes suffer from inefficient heat transfer due to the formation of flow bypass channels at the ends, which reduce the overall heat transfer coefficient.
Innovation Solution
A tube design featuring a corrugated insert with alternating crests and troughs within the tube inner volume, along with flow channels and bypass channels, where the flow channels are enhanced by turbulation features like louvered openings, and flow blocks are used to prevent fluid flow through the bypass channels, maximizing heat transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If flattened tubes are used in heat exchangers to provide compact design and allow extended surface features, then the compactness and structural efficiency are improved, but flow bypass channels form at the tube ends causing reduced heat transfer efficiency
Solution Approach 1:
The tube interior is segmented into flow channels and bypass channels using a corrugated insert with alternating crests and troughs. The crests define flow channels that extend through the tube length, while the troughs define bypass channels at the ends. This segmentation directs fluid flow through designated paths, preventing bypass flow from reducing heat transfer efficiency while maintaining the compact flattened tube shape.
2Ease of operation
If bypass channels are present at tube ends, then fluid can flow through the tube, but heat transfer to or from the fluid becomes less efficient
Solution Approach 1:
Different regions of the tube interior are given different functions: the central region contains flow channels with corrugated walls that promote turbulence and heat transfer, while the end regions contain bypass channels with smoother walls that allow fluid to pass through without significant heat transfer. This local differentiation ensures that heat transfer occurs primarily in the regions where it is most effective, while still allowing overall fluid flow through the tube.
3Loss of energy
If louvered openings are added to planar flanks to enhance heat transfer through turbulence, then heat transfer coefficient is improved, but device complexity increases
Solution Approach 1:
The corrugated insert combines multiple functions into a single component: it defines flow channels, creates turbulence through corrugated walls, and provides structural support within the tube. The alternating crests and troughs simultaneously organize fluid flow paths and generate turbulent mixing, eliminating the need for separate turbulence-generating devices and reducing overall system complexity while enhancing heat transfer.
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 enhances convective heat transfer by minimizing fluid flow through bypass channels and promoting turbulence in flow channels, leading to improved heat transfer performance and efficiency.
Implementation Method 1
The openings in the planar flanks can be formed without the removal of material from the flanks, such as by louvered openings or by lanced and offset openings. This fluid communication between the flow channels can allow for enhanced heat transfer to or from a fluid traveling through the tube, as it serves to turbulate the flow of the fluid and prevent the formation of a fluid boundary layer, thereby enhancing the overall heat transfer coefficient within the tube.
Implementation Method 2
A tube for a heat exchanger includes a tube outer body having first and second broad, opposing, spaced apart, planar walls joined by first and second arcuate end walls. The tube inner volume is bounded by the first and second broad, planar walls and by the first and second arcuate end walls, and extends from an inlet end of the tube to the an outlet end of the tube.
Implementation Method 3
The first and second bypass channels can each additionally be bounded by an end one of the planar flanks of the corrugated insert, particularly by the planar flank that is arranged nearest to the arcuate end wall that also bounds the bypass channel.
Data Source
AI summary
A tube for a heat exchanger includes a tube outer body enclosing a tube inner volume, and a corrugated insert received within the tube inner volume. The tube outer body has a pair of broad planar walls joined by arcuate end walls. The corrugated insert defines flow channels through the tube, with opening in flanks of the insert allowing for flow communication between adjacent flow channels. Bypass channels adjacent the arcuate end walls are fluidly isolated from the adjacent flow channels by the absence of such openings in the end flanks. Flow through the bypass channels is obstructed by flow blocks at one or both ends of the bypass channels.