SMA Stack Cell Structure for Heat Transfer and Buckling Resistance
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Solution Overview
Problem
Existing SMA stack structures face challenges in achieving improved heat transfer rates and power density while maintaining structural stability, particularly due to issues with buckling and inefficient heat transfer through thinner walls.
Innovation Solution
A superelastic SMA structure with a hexagonal or circular shape forming an array of hollow perforated cells between thin vertical walls, featuring a central opening for enhanced stability and improved heat flux, along with tensioning elements for reduced loading, and optimized hydraulic diameters for efficient fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thinner walls are used in SMA stack structure, then heat transfer rate is improved, but compressive stability deteriorates due to buckling
Solution Approach 1:
The patent divides the stack structure into multiple hollow perforated cells separated by thin vertical walls. This segmentation creates a honeycomb-like configuration where each cell is structurally supported by adjacent cells, distributing compressive loads across the entire structure rather than concentrating stress on individual thin walls. The segmentation allows the use of thinner walls for heat transfer while maintaining overall structural stability through the collective support of the cellular arrangement.
Solution Approach 2:
The patent transitions from a conventional planar plate structure to a three-dimensional hollow perforated cell configuration. By adding the dimensional complexity of hollow cells with optimized wall thicknesses and cellular geometries, the structure achieves enhanced compressive stability through geometric reinforcement while maintaining thin wall sections for efficient heat transfer. The multi-dimensional cellular architecture provides structural rigidity without requiring thicker walls.
2Power
If thinner walls are used to improve heat transfer, then power density is improved, but structural strength deteriorates
Solution Approach 1:
The stack is segmented into multiple hollow perforated cells with thin vertical walls, maximizing the surface area-to-volume ratio for heat transfer while the cellular configuration provides structural reinforcement. The segmentation allows thin walls to be supported by adjacent cells, maintaining structural strength despite reduced wall thickness for improved power density.
Solution Approach 2:
The patent employs a composite structural approach combining thin SMA wall sections with the surrounding hollow cell geometry and supporting structures. This composite configuration allows the thin SMA walls to function optimally for heat transfer while the overall cellular structure and supporting elements provide the necessary structural strength, achieving high power density without sacrificing structural integrity.
3Power
If longer stacks are used to increase capacity, then heat transfer capacity is improved, but buckling resistance deteriorates
Solution Approach 1:
The long stack is segmented into multiple shorter hollow cell sections connected in series. Each cell section maintains adequate buckling resistance due to its shorter length and cellular configuration, while the cumulative effect of multiple sections provides the desired total heat transfer capacity. The segmentation prevents buckling propagation throughout the entire stack length.
Solution Approach 2:
The patent uses three-dimensional hollow cellular structures with optimized geometries to provide structural support along the stack length. The cellular configuration and vertical wall arrangements create geometric reinforcement that resists buckling in longer stacks, enabling increased heat transfer capacity without proportionally increasing susceptibility to buckling failures.
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 solution enhances power density and compressive stability, allowing for longer stacks with reduced support structures and improved heat transfer efficiency, while minimizing buckling and pressure drops.
Implementation Method 1
Recent research into the Elastocaloric [EC] effect has demonstrated its potential as a solid-state alternative to traditional Vapour Compression refrigeration and heat pumping approaches. The EC cycle takes advantage of the superelastic behaviour of Shape Memory Alloys, which facilitates, through cyclic uniaxial loading and unloading, the absorption of heat from a low temperature source and its rejection to a higher temperature sink.
Implementation Method 2
Each of the modules includes one or more structures formed of shape memory alloy, which converts from austenite to martensite upon application of a first stress and releases latent heat from the conversion.
Data Source
AI summary
The present application relates to a superelastic SMA structure, with enhanced power density and compressive stability, comprising two or more connected plate sections to form an overall substantially closed perimeter, wherein the structure comprises an opening positioned in the centre of the structure, and wherein the connected plate sections are dimensioned with a circular symmetry to allow a stacking assembly, and wherein each section includes an array of hollow perforated cells formed between one or more thin vertical walls of a thickness within a predefined range of values, and wherein at least one perforated cell defines a fluid passageway within a predefined range of hydraulic diameter values.