Double Pipe Inner Tube Geometry for Bent-Section Heat Transfer
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Solution Overview
Problem
Existing heat-exchange cycles in motor-vehicle air conditioning systems face reduced thermal efficiency due to pressure losses and decreased heat-exchanging performance at bent portions of double pipes, particularly when using configurations with straight-shaped inner pipes and smooth outer pipes.
Innovation Solution
A heat-transferring double pipe design featuring an inner pipe with distinct regions of differing protruding parts, where the first region has fewer protrusions to minimize pressure losses at bent portions and the second region has more protrusions for enhanced heat exchange in straight portions, combined with a smooth outer pipe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a straight-shaped inner pipe is used in the double pipe configuration, then the manufacturing process is simplified, but the heat-exchanging performance at bent portions deteriorates due to passageway narrowing and pressure losses
Solution Approach 1:
The inner pipe is designed with different cross-sectional shapes at different locations: a first cross-sectional shape (e.g., circular) at bent portions to maintain passageway area and reduce pressure losses, and a second cross-sectional shape (e.g., oval or flattened) at straight portions to enhance heat-exchanging performance. This local differentiation allows the pipe to optimize for both manufacturing simplicity and thermal efficiency at different locations.
Solution Approach 2:
The inner pipe is divided into multiple sections along its length, with each section having a specific cross-sectional shape optimized for its function. The segmentation allows the pipe to transition between different geometric configurations to address the conflicting requirements of manufacturing ease and heat exchange efficiency at different locations.
2Reliability
If the inner pipe cross-sectional shape is optimized for heat exchange, then thermal efficiency improves, but the passageway area at bent portions narrows causing increased pressure losses
Solution Approach 1:
The pipe cross-sectional shape varies locally along its length: at bent portions, the cross-section maintains a shape that preserves passageway area (e.g., circular) to minimize pressure losses, while at straight portions, the cross-section adopts a shape optimized for heat exchange (e.g., oval with increased surface area). This resolves the contradiction by applying different geometric optimizations at different locations.
3Reliability
If protruding parts are added to the inner pipe to enhance heat exchange, then thermal efficiency improves, but the complexity of the manufacturing process increases
Solution Approach 1:
Instead of adding complex protruding parts, the invention changes the fundamental parameter of the pipe cross-sectional shape itself. By varying the cross-sectional geometry (e.g., from circular to oval) along the pipe length, the surface area for heat exchange is increased without introducing additional protruding structures, thus maintaining manufacturing simplicity while improving thermal efficiency.
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 overall heat-exchanging performance by reducing passageway narrowing and pressure losses at bent portions while maintaining optimal heat transfer in both bent and straight sections, improving compatibility with bending work.
Implementation Method 1
a twisted pipe is often used (refer to Patent Documents 1-3) as the inner pipe of double pipes proposed to date
Implementation Method 2
effecting the exchange of heat by causing a high-temperature coolant, which is discharged from the condenser, and a low-temperature coolant, which is discharged from the evaporator, to circulate, in opposition to each other, in two streams of space configured by the double pipe
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An inner pipe (2) is used in a heat-transferring double pipe for exchanging heat between a fluid that flows through the interior of the inner pipe (2) disposed in the interior of an outer pipe and a fluid that flows between the inner pipe (2) and the outer pipe. The inner pipe (2) has a first region (21) and a second region, which have cross-sectional shapes that differ, and the first region (21) has a plurality of first protruding parts (211) that protrude outward and has a first recess-protrusion shape in which locations of the first protruding parts (211) are offset helically in a longitudinal direction. The second region has a plurality of second protruding parts that protrude outward, in which the number of second protruding parts is greater than the number of first protruding parts, and has a second recess-protrusion shape, in which locations of the second protruding parts are offset helically in the longitudinal direction.