Opposed Helical Heat Exchange Coils for Stress-Stable Arrays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Heat exchange arrays in power plants face challenges with elastic stress-induced distortion and instability due to the winding process of concentric coils, which can lead to uneven heat transfer and potential damage to fins, especially in large-scale applications where complete stress relief is difficult to achieve.
Innovation Solution
The use of interconnected left-handed and right-handed helically coiled heat exchange tubes with external fins, supported by rigid members to counterbalance elastic stresses, and a manufacturing method involving a rotatable mandrel to form coils of opposite chirality, ensuring stability and efficient packing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If concentric coils are wound by winding a straight length of tube around a rotating body, then the heat exchange array can be manufactured, but elastic stress is produced within the coil causing distortion and instability
Solution Approach 1:
The patent applies asymmetry by using helically coiled tubes with opposite chirality (one left-handed, one right-handed) instead of identical symmetric coils. This asymmetric configuration causes the elastic stresses in the two coils to act in opposite directions, thereby counterbalancing each other and reducing overall distortion and instability in the heat exchange array.
Solution Approach 2:
The patent implements the counterweight principle by introducing a second coil with opposite chirality whose elastic stress acts as a counterbalancing force to the first coil's stress. The support members rigidly interconnecting the two coils allow these opposing stresses to neutralize each other, stabilizing the overall structure without requiring complete stress relief.
2Reliability
If the entire array is heated in an oven to reduce elastic stress, then stress relief can be achieved, but it is not feasible for large-scale arrays
Solution Approach 1:
The patent extracts the stress relief problem from the entire array by focusing on counterbalancing stresses at the coil level rather than attempting to relieve stress throughout the entire large-scale array. This approach makes the solution feasible for large installations where oven heating would be impractical.
Solution Approach 2:
The patent changes the physical configuration parameter of the coils by using opposite chirality instead of attempting to change the stress state through thermal treatment. This parameter change (from thermal stress relief to mechanical stress counterbalancing) makes the solution scalable to large arrays.
3Use of energy by moving object
If external fins are added to increase heat transfer surface area, then heat exchange efficiency is improved, but the coils become harder to bend and more difficult to coil
Solution Approach 1:
The patent merges the two coils with opposite chirality and uses support members to rigidly interconnect them. This combined structure allows the elastic stresses to counterbalance each other, which compensates for the increased difficulty of coiling finned tubes by reducing the net stress and distortion that would otherwise make the coiling process even more difficult.
4Ease of manufacture
If coils are wound in the same direction, then manufacturing is simplified, but elastic stress forces act in the same direction causing distortion
Solution Approach 1:
The patent applies inversion by winding one coil in a left-handed helical direction and the other in a right-handed helical direction. This inverted configuration ensures that the elastic stress forces act in opposite directions, counterbalancing each other and preventing the distortion that would occur if both coils were wound in the same direction.
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 approach reduces overall stress and distortion, enhances heat transfer efficiency, and allows for more even distribution of coils, improving the stability and performance of heat exchange arrays in large-scale power plant applications.
Implementation Method 1
As the tube is wound into a coil, stresses are produced within the coil as the metal used to manufacture the tubing undergoes plastic and elastic deformation
Implementation Method 2
The heat exchange medium is heated by the exhaust gas, and can be used for further processes
Implementation Method 3
The exhaust gas is passed through a heat exchange unit comprising a heat exchange array
Data Source
Figure 1
Figure 1a~1b
Figure 2
AI summary
A heat exchange array arranged to be used in a heat exchange unit and further arranged to recover energy from an exhaust gas, comprising: a first heat exchange tube and a second heat exchange tube, each arranged to carry a heat exchange medium and further each comprising a series of external fins; and wherein the first heat exchange tube comprises a left-handed helically coiled tube having an first elastic stress, and the second heat exchange coil comprises a right-handed helically coiled tube having a second elastic stress, and wherein the first and second heat exchange tubes are interconnected such that the first elastic stress opposes the second elastic stress.