Ribbed Metal Heat Exchanger Tube for Segmented Boiling Channels
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Solution Overview
Problem
Current heat exchanger tubes for evaporators lack efficient structures to enhance heat transfer during the evaporation of liquids, leading to suboptimal performance and increased costs due to larger sizes and higher refrigerant requirements.
Innovation Solution
The development of metallic heat exchanger tubes with integral ribs and segmented channels, featuring radially outward projections and cavities that create localized overheating and nucleate boiling sites, reducing fluid flow and enhancing bubble formation and heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If additional structures are added to the groove base to enhance heat transfer, then the heat transfer coefficient increases, but the device complexity increases
Solution Approach 1:
The groove base is segmented into multiple discrete additional structures (protrusions and cavities) rather than using a continuous complex structure. This segmentation allows the heat transfer surface to be divided into functional zones that enhance nucleate boiling while maintaining manufacturing feasibility through standardized repetitive elements.
Solution Approach 2:
Additional structures are placed specifically at the groove base where the liquid film is thinnest and temperature is highest, creating localized enhancement zones. The protrusions and cavities are positioned to exploit the natural flow patterns and thermal gradients, providing targeted heat transfer improvement without uniformly complicating the entire heat exchanger surface.
2Power
If the channel cross-sectional area is reduced to increase heat transfer intensity, then the heat transfer coefficient increases, but the fluid flow is impeded
Solution Approach 1:
The channel cross-sectional area is reduced only locally at the groove base region where additional structures are positioned, rather than constricting the entire channel length. This localized reduction intensifies heat transfer where the liquid film is thinnest and thermal gradient is steepest, while maintaining adequate flow area elsewhere to preserve overall fluid productivity.
Solution Approach 2:
The additional structures partially obstruct the channel to create the desired effect - enough reduction to enhance heat transfer intensity through increased velocity and turbulence, but not so much as to completely block flow. The obstruction is calibrated to provide optimal heat transfer enhancement while maintaining acceptable pressure drop and flow rate.
3Power
If higher projections are added to the groove base to enhance evaporation, then the bubble formation increases, but the fluid flow in the channel is adversely impeded
Solution Approach 1:
Instead of only increasing projection height in the radial dimension, the invention adds a second dimension by creating cavities beneath the protrusions. This vertical stacking of features (protrusion above, cavity below) provides multiple interfaces for bubble formation and liquid replenishment without requiring excessive single-dimension projection heights that would block the channel.
Solution Approach 2:
The cavity is nested within the groove base structure, with the protrusion extending from the groove base and the cavity positioned beneath it. This nested arrangement creates a compact multi-level structure that provides enhanced evaporation surfaces while maintaining a compact overall profile that does not excessively protrude into the channel flow path.
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 design significantly increases the heat transfer coefficient by segmenting the channel, optimizing evaporator tube structures for improved performance across a wide range of operating conditions, while reducing the cross-sectional area for fluid flow and promoting efficient bubble nucleation and vapor exchange.
Implementation Method 1
incorporating additional structural elements in the groove base area between the fins... intensify the nucleate boiling process to increase heat transfer during evaporation
Implementation Method 2
Evaporation occurs in many areas of refrigeration and air conditioning... liquids of pure substances or mixtures evaporate on the outside of the tube
Implementation Method 3
The additional structures locally reduce the flow-through cross-sectional area in the channel between two fins and thereby limit fluid flow in the channel
Implementation Method 4
Shell-and-tube heat exchangers are often used, in which liquids of pure substances or mixtures evaporate on the outside of the tube, while brine or water cools on the inside
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a metal heat exchanger tube (1), comprising integral ribs (2) formed on the outside of the tube, said ribs having a rib foot (3), rib flanks (4), and a rib tip (5), the rib foot (3) protruding radially from the tube wall (10) and a channel (6) being formed between the ribs (2), which channel has a channel bottom (61) and in which channel there are arranged additional structures (7, 71, 72) spaced apart from each other. The additional structures (7, 71, 72) divide the channel (6) between the ribs (2) into segments (8). The additional structures (7, 71, 72) locally reduce the cross-sectional area through which fluid can flow in the channel (6) between two ribs (2) and thus at least delimit a fluid flow in the channel (6) during operation. First additional structures (7, 71) are delimited by radially outwardly directed projections (71) which start from the channel bottom (61) and are each delimited in the radial direction by a termination face (713) located between the channel bottom (61) and the rib foot (5), thus defining a radial extension of the projections (71). Radially outwardly located cavities (72) are arranged as second additional structures (7, 72) at the location of the projections (71) and are formed from material of the rib flanks (4) and of the radially outwardly arranged termination face (713) of the projections (71). The cavities are each arranged in the radial direction between a termination face (713) and the rib tip (5), so that the cavities (72) around the radial extent of the projections (71) are formed above the channel bottom (61) of the channel (6), laterally against the rib flank (4). The cavities (72) are open in the axial direction.