Harmonica Tube Inner Wall Structure for Faster Refrigerant Nucleation
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Solution Overview
Problem
Conventional harmonica tube heat exchangers suffer from reduced heat exchange capacity due to slow nucleation and detachment of refrigerant nuclei from the smooth inner wall, leading to inefficient boiling heat transfer, especially under high heat generation conditions of power batteries.
Innovation Solution
The harmonica tube design incorporates protrusions and recesses on the inner sidewall of flow channels to facilitate rapid nucleation and detachment of refrigerant bubbles, preventing boundary layer formation and enhancing heat transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the inner wall of the flow channel is smooth, then the refrigerant flows smoothly through the channel, but the contact time between the refrigerant and the inner wall surface is too short and nucleation is not conducive
Solution Approach 1:
The inner wall of the flow channel is equipped with protrusions and recesses at specific locations rather than being uniformly smooth or rough. These localized structures create specific nucleation sites where bubbles can form and detach efficiently, while other areas maintain smooth flow characteristics. This resolves the contradiction by providing local nucleation promotion without compromising overall flow smoothness.
2Ease of operation
If the inner wall of the flow channel is smooth, then the refrigerant flows easily, but once nucleated the nucleus always swims along the inner wall surface and cannot be detached rapidly
Solution Approach 1:
Protrusions and recesses are strategically positioned on the inner wall to create localized detachment zones. These structures provide anchor points and flow disturbance zones that help nucleated bubbles detach rapidly from the wall surface, preventing them from swimming along the smooth wall. The majority of the wall remains smooth to maintain easy flow, while the localized structures provide the necessary detachment functionality.
Solution Approach 2:
Multiple protrusions and recesses are distributed along the flow channel, creating multiple identical nucleation and detachment sites. This copying of the same functional structure throughout the channel ensures consistent bubble detachment behavior across the entire heat exchange surface, maintaining both flow ease and high heat exchange capacity.
3Reliability
If protrusions and recesses are added to the inner sidewall, then nucleation and detachment of refrigerant bubbles are facilitated, but the manufacturing complexity increases
Solution Approach 1:
The protrusions and recesses are designed with specific dimensional parameters (size, spacing, depth) that can be optimized for manufacturing. By controlling these parameters within certain ranges, the structures can be formed using conventional machining or molding techniques, balancing the need for effective nucleation/detachment with manufacturing ease. The parameters are tuned to achieve the desired thermal performance without requiring overly complex manufacturing processes.
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 modified harmonica tube design significantly improves heat exchange capacity by promoting quick nucleation and preventing boundary layer formation, effectively addressing the inefficiencies of conventional designs under high heat conditions.
Implementation Method 1
at least part of the inner sidewall of the flow channels is provided with a protrusion protruding towards near the center direction of the flow channels and/or provided with a recess recessing away from the center direction of the flow channels
Implementation Method 2
once nucleated, the nucleus always swims along the inner wall surface and cannot be detached from the wall surface rapidly, causing the heat exchange capacity to be reduced
Data Source
AI summary
A harmonica-shaped tube, a harmonica-shaped tube type heat exchanger and a vehicle are provided. The harmonica-shaped tube includes a plurality of flow channels arranged at intervals. Inner walls of at least some flow channels include protrusions protruding in a direction approaching centers of the flow channels and/or include recesses recessing in a direction away from the centers of the flow channels. The protrusions and recesses enable a liquid fluid (e.g., refrigerant) to nucleate rapidly, and can also burst large nucleuses which grow in a disorderly manner, thereby preventing the large nucleuses from forming boundary layers on inner walls of the plurality of flow channels, such that nucleuses can be separated from inner wall surfaces rapidly. Therefore, heat exchange performance of the harmonica-shaped tube is improved, and heat exchange requirements of a traction battery are satisfied.