Flat-Tube Heat Exchanger Rib Geometry for Higher Heat Transfer
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Solution Overview
Problem
Existing heat exchangers for motor vehicles, particularly those with parallel ribs, face challenges in manufacturing complexity and reduced heat transmission power due to fixed rib density and gill length dependencies on bending radius, which complicates production and affects performance.
Innovation Solution
The use of an arcuate piece with three portions of different curvatures, where the middle portion has a low curvature and the outer portions have higher curvatures, creating an asymmetric profile, allows for simpler production and maintains the advantages of parallel ribs with longer gill lengths and improved heat transmission, by being producible on conventional rib rollers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a constant curvature rib bending radius is used for parallel ribs, then the manufacturing process is simplified, but the gill length is reduced and heat transmission power is lowered
Solution Approach 1:
The rib bending radius is segmented into three distinct portions: a first portion with a first bending radius, a middle portion with a second (larger) bending radius, and a second portion with a third bending radius. This segmentation allows each portion to serve different functions - the tighter bends enable sufficient gill length while the middle portion with larger radius maintains manufacturing simplicity and parallelism.
Solution Approach 2:
Different portions of the rib are assigned different bending radii according to their specific functional requirements. The outer portions have tighter curvature for structural integrity and gill length, while the middle portion has a larger bending radius to maintain parallelism with the tube wall and simplify manufacturing in that critical region.
2Stability of the object's composition
If the rib bending radius is increased to maintain parallelism, then the rib spacing is fixed, but the gill length becomes shorter and heat transmission power is reduced
Solution Approach 1:
The rib structure is divided into segments with different bending radii. The middle portion uses a larger bending radius to maintain parallelism and stable rib spacing, while the outer portions use smaller bending radii to ensure sufficient gill length extends from the tube surface to the rib.
Solution Approach 2:
The rib bending radius is made variable along the length of the rib (one dimension) rather than constant throughout. This dimensional variation allows the rib to simultaneously achieve parallelism in the middle region and sufficient gill length at the ends, resolving the contradiction between these two requirements.
3Power
If a rectangular or meander-shaped corrugated rib is used to achieve long gill lengths, then heat transmission power is improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
Instead of using complex rectangular or meander-shaped profiles that require specialized manufacturing, the invention uses a curved profile with varying bending radii. This curved approach can be produced using conventional rib rollers and forming tools, significantly reducing manufacturing complexity while maintaining the benefit of long gill lengths.
Solution Approach 2:
The bending radius parameter is varied continuously or in steps along the rib length, transitioning from tight bends at the ends to a larger radius in the middle portion. This parameter change allows the rib to achieve the desired geometry for long gills without requiring complex manufacturing processes, as the varying curvature can be produced with standard forming equipment.
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 enhances air throughput, flow deflection, and heat transmission power while reducing manufacturing costs and complexity, offering improved performance and ease of production compared to conventional parallel ribs.
Implementation Method 1
a soldered heat exchanger network consisting of flat tubes and of corrugated ribs
Implementation Method 2
the surface of the corrugated ribs is slotted, that is to say equipped with gills, which break up the boundary layer flows that are formed and which bring about a deflection of the air flow from one flow duct into the other
Implementation Method 3
the flat tubes have flowing through them a liquid and/or vaporous medium, for example a coolant or refrigerant, which discharges its heat to the ambient air or absorbs heat from the ambient air
Data Source
AI summary
The invention relates to a heat exchanger, especially for motor vehicles, comprising a soldered heat exchanger network made of flat pipes (2,3) and corrugated ribs (1). A liquid and/or vaporous-type medium can flow through the flat tubes (2, 3) and air can circulate around the corrugated ribs. One corrugated rib respectively comprises two surfaces (4,5) which are arranged in an essentially parallel manner in relation to each other and which are connected respectively by an arch-shaped piece (6) which is soldered to a flat pipe, said arch-shaped piece comprising three sections (6a,6b,6c) which have different curvatures.