Compressed Sintered Graphite Thermal Storage Managing Phase Change Pressure
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Solution Overview
Problem
Existing thermal energy storage systems using silicon metalloid materials face issues with pressure buildup and cracking due to expansion and contraction, and poor heat transfer efficiency, particularly when using containment tubes and bundled graphite rods.
Innovation Solution
A thermal energy storage apparatus featuring a contiguous block of compressed sintered graphite with progressively decreasing side wall angles and discrete sections, eliminating containment tubes and enhancing heat transfer by using electric heating elements and a closed-cycle heat engine, while maintaining the phase change material in a receptacle that disperses pressure and prevents cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If containment tubes are used to store phase change material, then the material is contained and protected, but heat transfer efficiency decreases and the apparatus becomes more complex
Solution Approach 1:
The invention removes containment tubes from the system entirely. The phase change material is placed in direct contact with the graphite heat-absorbing block, eliminating the thermal resistance barrier that tubes create. This extraction of the containment element resolves the contradiction by prioritizing heat transfer efficiency while maintaining material containment through the graphite block's structural design.
Solution Approach 2:
The invention merges the containment function with the heat transfer medium itself. The graphite block serves both as the heat-absorbing material and as the containment structure for the phase change material. This merging eliminates the intermediate containment tubes that impede heat transfer, allowing direct thermal contact between the phase change material and graphite.
2Device complexity
If bundled graphite rods are used as heat-absorbing material, then the structure is simple, but heat transfer efficiency is poor
Solution Approach 1:
The invention merges multiple graphite rod bundles into a single contiguous block of compressed sintered graphite. This consolidation maintains the simplicity of using graphite as the heat-absorbing material while dramatically improving heat transfer efficiency by eliminating the air gaps and thermal resistance between individual rods or bundles. The contiguous block provides direct, uninterrupted thermal contact with the phase change material.
3Stress or pressure
If phase change material is stored in separate enclosures, then pressure buildup is contained, but the enclosures are prone to cracking and heat transfer efficiency is reduced
Solution Approach 1:
The invention removes separate enclosures for the phase change material and replaces them with a containment approach using the graphite block itself. The graphite block's structural integrity and thermal properties allow it to contain the material while managing pressure through direct contact and thermal expansion accommodation, eliminating the cracking issues associated with separate enclosures.
Solution Approach 2:
The invention uses the composite interaction between the phase change material and the graphite heat-absorbing block. The graphite block's unique properties - including its ability to absorb thermal energy and its structural stability - create a composite system that manages pressure effectively without requiring separate enclosures, thereby preventing cracking while maintaining containment.
4Loss of energy
If phase change material undergoes expansion during solidification, then thermal energy is stored, but pressure builds up on the enclosure
Solution Approach 1:
The invention converts the harmful effect of expansion-induced pressure into a beneficial thermal storage mechanism. The phase change material's expansion during solidification is allowed to occur in direct contact with the graphite block, which absorbs the thermal energy released during the phase change. The graphite's structural stability accommodates the expansion without creating damaging pressure concentrations, transforming what would be a harmful mechanical stress into useful thermal energy storage.
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 effectively manages pressure during phase changes, enhances heat transfer efficiency, and reduces the risk of cracking, allowing for reliable and efficient storage and retrieval of thermal energy.
Implementation Method 1
the silicon metalloid material would absorb thermal energy as it underwent a phase change from a solid to a liquid
Implementation Method 2
storing thermal energy within the compressed sintered graphite for use at a later time
Implementation Method 3
on undergoing a phase change from liquid to solid, there is an expansion of the material rather than contraction
Implementation Method 4
enhancing heat transfer by using electric heating elements and a closed-cycle heat engine
Implementation Method 5
enhancing heat transfer by using electric heating elements
Implementation Method 6
The thermal energy stored within the silicon metalloid material could be converted into electrical and/or mechanical action through electrical devices such as a Stirling engine or Turbine
Data Source
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AI summary
A thermal energy storage apparatus, including: a block of a heat-absorbing material, the block defining at least one receptacle and being a contiguous block of compressed sintered graphite; and a phase change material stored in the or each receptacle, the phase change material being one that expands as it cools, wherein separation of side walls of the or each receptacle progressively increases as they extend upwardly from the base, whereby as the phase change material solidifies and expands it is urged upwardly to reduce pressure applied to the heat- absorbing material.