Latent Heat Storage Device with Graphite Matrix
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Solution Overview
Problem
Existing latent heat storage devices based on phase change materials (PCMs) and graphite composites face challenges in reducing thickness and ensuring mechanical stability, particularly for electronic device cooling where space is limited and thermal conductivity is low.
Innovation Solution
A method involving preheating graphite blanks in a vacuum furnace above the melting temperature of a PCM, infiltrating the PCM into the graphite to form a denser composite, and applying a high-density graphite cover foil for enhanced thermal conductivity and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If phase change materials are used for heat storage, then heat storage capacity is improved, but thermal conductivity deteriorates
Solution Approach 1:
The patent creates a composite material system where phase change material particles are embedded within a porous graphite matrix. The graphite provides high thermal conductivity pathways while the PCM particles provide latent heat storage capacity. This composite structure resolves the contradiction by combining materials with complementary properties - the graphite matrix acts as a thermal conduit network that overcomes the inherently low thermal conductivity of pure PCM while maintaining the high heat storage capacity through phase change.
Solution Approach 2:
The patent utilizes a porous graphite matrix with controlled porosity to hold PCM particles. The porous structure allows sufficient PCM content for high heat storage capacity while the graphite walls of the pores provide continuous thermal conduction pathways. The porosity is optimized to balance PCM loading (for heat storage) with thermal conductivity requirements, resolving the contradiction between quantity of heat storage material and thermal performance.
2Reliability
If additional graphite materials are added to improve thermal conductivity, then device complexity increases
Solution Approach 1:
The patent merges the structural support function and thermal conduction function into a single porous graphite matrix component. Rather than adding separate graphite heat sinks or thermal pathways, the graphite is integrated as the very matrix that holds the PCM particles. This consolidation achieves high thermal conductivity without increasing device complexity, as the same structure that provides mechanical integrity also provides thermal pathways.
Solution Approach 2:
The graphite matrix serves multiple functions simultaneously: it provides structural rigidity to the device, acts as a thermal conduction network, and serves as the containment medium for PCM particles. This multi-functionality eliminates the need for additional components, thereby improving thermal conductivity without increasing device complexity.
3Quantity of substance
If PCM is used without structural support, then heat storage capacity is improved, but mechanical stability deteriorates
Solution Approach 1:
The porous graphite matrix provides a rigid structural framework that confines the PCM particles. The graphite walls of the pores act as structural support elements that maintain mechanical stability while the porous nature allows high PCM loading for heat storage capacity. The matrix structure prevents PCM deformation and provides overall device rigidity.
Solution Approach 2:
The composite of PCM particles embedded in graphite matrix creates a material where the graphite phase provides mechanical strength and structural integrity while the PCM phase provides heat storage capacity. The interfacial bonding between PCM particles and graphite matrix ensures mechanical stability is maintained even with high PCM content.
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 method enables the production of thin, high-capacity latent heat storage devices with improved thermal conductivity and mechanical stability, suitable for electronic device cooling and other applications, achieving storage capacities and conductivities that are promising for practical use.
Implementation Method 1
preheating the graphite blank to a temperature that lies above a melting temperature of the phase change material to be infiltrated; the preheating is effected in a vacuum furnace
Implementation Method 2
aspirating the phase change material (PCM) in the liquid phase into the reactor space and causing the phase change material (PCM) to infiltrate the graphite blank
Implementation Method 3
Phase change materials (PCM) are capable of storing heat energy in the form of latent heat. The heat content is stored primarily by the conversion of the PCM from one phase to another. Most PCMs thereby change between a liquid phase and a solid phase.
Implementation Method 4
The heat transferred into or out of the PCM does not change its temperature; it is referred to as latent heat
Data Source
Figure 1~2
Figure 3
AI summary
A latent heat storage device is formed with a carrier substrate (1) formed of expanded graphite material. Phase change material is infiltrated in the graphite material. A thin graphite sheet provides for the functional heat conductivity into an out of the carrier substrate. Prior to the infiltration, the carrier substrate (1) has predetermined volume dimensions and a given starting density. After the phase change material (PCM) is infiltrated in the carrier substrate (1), the density of the infiltrated carrier substrate (1) exceed the starting density by a ratio of at least 3:1 or 4:1 or more. The volume dimensions of the infiltrated the carrier substrate (1) remain substantially unchanged. In the alternative, the latent heat storage device may also be formed by providing a PCM coating layer on a thin carrier substrate (1). In that case, the phase change material is interspersed in a carrier matrix forming the PCM coating layer. The composite device may be very thin.