Phase-Change Energy Cell with Axial Membrane Expansion
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Solution Overview
Problem
Existing energy cells using phase-change materials for hydraulic or mechanical energy conversion face issues such as high stresses and short lifetimes due to large diameter changes in the bladder, leading to potential folding and complex assembly processes.
Innovation Solution
A device with a concentric tube design where the phase-change material is in the core and pushes hydraulic fluid outside, reducing membrane expansion and stress, and featuring a detachable membrane with ribs for reinforcement and easy assembly, using a heat exchanger for efficient heat recovery from waste flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bladder diameter changes significantly to displace hydraulic fluid, then the volume displacement efficiency is improved, but the stress in the bladder material increases and lifetime decreases
Solution Approach 1:
The invention transitions from radial expansion (changing bladder diameter) to axial expansion (extending bladder length). The bladder is configured as a tube that expands primarily in the axial direction rather than radially, displacing hydraulic fluid through length extension rather than diameter increase. This dimensional change reduces circumferential stress while maintaining volume displacement efficiency.
Solution Approach 2:
The invention uses a tube-like membrane structure that is optimized for axial flexibility rather than radial flexibility. The tube configuration allows the membrane to expand lengthwise with lower stress concentrations compared to radial expansion, improving both durability and displacement efficiency.
2Stress or pressure
If the bladder material is made thinner to reduce stress, then the stress for the same volume change is reduced, but the bladder becomes more susceptible to folding and tearing
Solution Approach 1:
By changing the expansion direction from radial to axial, the invention reduces the stress-thickness relationship challenges. Axial expansion distributes stress along the length of the tube rather than concentrating it circumferentially, allowing for thinner walls without compromising strength against folding and tearing.
Solution Approach 2:
The tube membrane is designed with ribs or reinforcement elements that segment the structure, providing localized support to prevent folding while maintaining overall flexibility for axial expansion. This segmentation allows thinner material usage without sacrificing durability.
3Ease of manufacture
If the energy cell uses a piston-cylinder construction, then the structure is simple and easy to manufacture, but friction losses reduce efficiency
Solution Approach 1:
The invention replaces the mechanical piston-cylinder contact system with a hydraulic membrane system. The flexible tube membrane separates the phase-change material chamber from the hydraulic fluid chamber, eliminating solid-to-solid friction while maintaining effective force transmission through fluid pressure. This resolves the contradiction by using hydraulic principles to achieve both efficiency and manufacturability.
4Productivity
If the bladder is made larger to increase volume displacement, then the energy conversion efficiency is improved, but the stresses in the bladder material increase due to larger diameter changes
Solution Approach 1:
The invention achieves larger volume displacement through axial extension of the tube membrane rather than radial expansion. This allows the bladder to be effectively 'larger' in terms of displacement capacity without the stress penalties associated with increased diameter, as the stress is distributed along the axial length rather than concentrated circumferentially.
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 prevents undesired folds, extends membrane lifetime, simplifies assembly, and allows for efficient heat recovery from low-temperature waste flows, reducing stress and improving the energy conversion process.
Implementation Method 1
an energy cell which makes use of the properties of a phase-change material whose volume changes by definition upon each change of phase from a solid to a liquid phase and vice versa
Implementation Method 2
which expands upon the transition from the solid to the liquid state due to heating
Implementation Method 3
a heat exchanger for efficient heat recovery from waste flows
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Energy cell that is provided with a pressure vessel (2) with two chambers separated by a membrane, respectively a first chamber (6) filled with a phase-change material (23) and a second chamber (7) filled with hydraulic fluid (24), whereby this energy cell (1) is provided with means to be able to heat and cool the phase-change material (23) alternately, coupled with a volume change, whereby the second chamber (7) is provided with a passage (26) that acts as an input and/or output for the hydraulic fluid (24), whereby the membrane (5) is stretched elastically upon a phase change whereby the volume in the first chamber (6) increases.