Heat Exchanger Tube Dimple Pattern for Pressure Drop Reduction
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Solution Overview
Problem
Existing heat exchanger tubes with dimple patterns on their surfaces enhance thermal efficiency but often lead to increased pressure drops and reduced durability due to varying cross-sectional areas and interference with fin attachment, which compromises thermal efficiency and service life.
Innovation Solution
The tubes feature a unique dimple pattern with protuberances on the inner surfaces arranged in longitudinal rows that are offset, maintaining a constant hydraulic area and minimizing pressure drops while facilitating better fin attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dimples are formed on the outer surface of the tubes to increase heat transfer, then thermal efficiency is improved, but pressure drop of the fluid increases
Solution Approach 1:
The patent applies local quality by creating dimples only in specific regions of the tube surface rather than uniformly across the entire surface. The dimples are positioned in zones that optimize heat transfer while minimizing interference with fluid flow, thereby improving thermal efficiency without excessively increasing pressure drop.
Solution Approach 2:
The patent changes geometric parameters of the dimples including their size, depth, spacing, and distribution pattern. By optimizing these parameters, the patent achieves enhanced heat transfer coefficients while controlling the pressure drop penalty to acceptable levels.
2Productivity
If dimples are formed on the tube surface to create turbulent flow, then heat transfer is enhanced, but the cross-sectional area of the tubes varies along the length
Solution Approach 1:
The patent applies local quality by creating dimples only in specific regions of the tube surface rather than uniformly across the entire surface. The dimples are positioned in zones that optimize heat transfer while minimizing interference with fluid flow, thereby improving thermal efficiency without excessively increasing pressure drop.
Solution Approach 2:
The patent maintains equipotentiality by ensuring that the overall cross-sectional flow area remains constant along the tube length despite the presence of dimples. The dimple patterns are designed so that reductions in area at dimple locations are compensated by increased spacing between dimples in adjacent rows, maintaining uniform hydraulic characteristics.
3Ease of manufacture
If straight line rows of dimples are formed on the tubes, then manufacturing is simplified, but fin attachment quality is reduced when fins align with dimples
Solution Approach 1:
The patent applies asymmetry by arranging dimples in staggered or offset patterns rather than straight aligned rows. This asymmetric arrangement prevents continuous straight lines of dimples from forming, allowing fins to be properly attached to the tube surface without bridging gaps between dimples, thereby maintaining both manufacturability and fin attachment quality.
Solution Approach 2:
The patent uses the dimple pattern arrangement as an intermediary element that mediates between the conflicting requirements of easy manufacturing and good fin attachment. By carefully designing the offset pattern, the patent enables straightforward fabrication processes while simultaneously providing adequate solid material for fin brazing or bonding.
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 thermal efficiency by maintaining turbulent fluid flow while reducing pressure drops and improving fin attachment quality, thus maximizing both thermal efficiency and durability of the heat exchanger tubes.
Implementation Method 1
The protrusions cause the flow of the fluid within the tubes to be turbulent which is known to increase the heat transfer from the fluid to the tube
Implementation Method 2
heat in a fluid flowing through the tubes is conducted through the walls of the tubes, into the fins, and into the air
Implementation Method 3
the protuberances in one row are longitudinally offset from the protuberances in another row to maintain a substantially constant hydraulic area of the tube along the longitudinal axis... which causes the increase in the pressure drop of the fluid
Data Source
AI summary
A tube for a heat exchanger is disclosed, the tube including a plurality of protuberances formed on an inner surface of the tube. The protuberances are arranged in a pattern that maintains a substantially constant cross sectional hydraulic area along a length of the tube.