Pressure-Compensated Thermal Storage Module
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Solution Overview
Problem
Thermal energy storage systems using incompressible phase change materials face issues with pressure buildup and leakage when the material transitions between solid and liquid phases, making them unsuitable for applications like aerospace due to the risk of vessel rupture or inadequate thermal contact when the material contracts.
Innovation Solution
A sealed enclosure containing an incompressible phase change material and a compressible material, such as an inert gas, within an elastic bladder allows the PCM to expand and compress without significant pressure increase, using an external reservoir for pressure control and incorporating a pressure relief manifold for over/under pressure protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PCM fills the sealed vessel when in solid state, then the vessel becomes pressurized when heated and PCM converts to liquid phase, but this causes leakage, rupture or catastrophic failure of the thermal energy storage system
Solution Approach 1:
The sealed vessel is segmented into two distinct compartments: an inner expandable bladder containing the PCM and an outer vessel structure containing a compressible fluid. This segmentation allows the PCM to expand independently within the bladder while the outer vessel maintains structural integrity by containing the pressure in a separate fluid medium.
Solution Approach 2:
A compressible fluid acts as an intermediary substance between the expanding PCM and the rigid vessel walls. The fluid absorbs the expansion pressure through compression, preventing direct transmission of high stresses to the vessel structure and eliminating the risk of rupture or leakage.
2Temperature
If the space is a sealed vessel of constant volume and the PCM fills the vessel when in liquid state, then the PCM does not make sufficient thermal contact with the vessel when cooled and contracts into solid phase
Solution Approach 1:
The inner bladder is designed as a flexible, collapsible membrane that maintains intimate thermal contact with the PCM throughout phase transitions. When the PCM contracts during solidification, the flexible bladder collapses accordingly, ensuring continuous thermal contact between the PCM and the heat transfer surfaces, thereby maintaining effective thermal coupling.
3Reliability
If a large increase in pressure pushes liquid-phase PCMs through seams, interfaces, O-rings, fittings and other pathways, then leakage occurs, but using a compressible material allows the PCM to expand and compress without significant pressure increase
Solution Approach 1:
The system utilizes a pneumatic approach by filling the outer vessel with a compressible gas or fluid. This allows the accommodation of PCM volume changes through pressure absorption in the fluid medium, eliminating the need for complex pressure relief mechanisms, expansion joints, or reinforced sealing systems that would otherwise be required to prevent leakage.
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 configuration prevents leakage and rupture while ensuring effective thermal contact by managing pressure and maintaining system integrity, making thermal energy storage systems more reliable for applications requiring controlled temperature buffering.
Implementation Method 1
the PCM melts from a solid to a liquid when its temperature goes above a certain temperature, and thus absorbs heat, and solidifies from a liquid to a solid when its temperature goes below the certain temperature and thus releases heat
Implementation Method 2
a material, such as a suitable wax, that releases or absorbs heat at a phase transition of the material
Implementation Method 3
a sealed enclosure enclosing an incompressible phase change material (PCM) and a compressible material contained in an elastic bladder
Implementation Method 4
an elastic bladder
Data Source
AI summary
A thermal energy storage system including an enclosure having an internal volume. An incompressible phase change material (PCM) is provided within the internal volume of the enclosure, where the PCM contracts into a solid state when its temperature falls below a certain temperature and expands into a liquid state when its temperature goes above the certain temperature. An elastic bladder is positioned adjacent to the PCM within the internal volume of the enclosure and is filled with a compressible material, where the PCM pushes against the bladder when it is expanded to the liquid state and causes the compressible material to be compressed within the bladder and the enclosure.