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This study explores the latent thermal energy storage potential of an organic phase change material with porous copper foam and its applicability in electronic cooling under varying heat load conditions. The organic phase change material, n-eicosane, is known for its inherently low thermal conductivity of 0.15 W/mK, rendering it vulnerable during power spikes despite its abundant latent heat energy for phase transition from solid to liquid. Porous copper foams are often integrated into n-eicosane to enhance the composite’s thermal conductivity. However, the volume fraction of the phase change material in the porous foam that optimally improves the thermal performance can be dependent on the boundary condition, the cut-off temperature, and the thickness. A finite difference numerical model was developed and utilized to ascertain the energy consumption for the composite of n-eicosane with two kinds of porous copper foam with varying porosity under different heat rates, cut-off temperatures, and thickness. In addition, the results are compared with a metallic phase change material (gallium), a material chosen with a similar melting point but significantly high thermal conductivity and volumetric latent heat. For validation of the numerical model and to experimentally verify the effect of boundary condition (heat rate), experimental investigation was performed for n-eicosane and high porosity copper foam composite at varying heat rates to observe its melting and solidification behaviors during continuous operation until a cut-off temperature of 70 ◦C is reached. Experiments reveal that heat rate influences the amount of latent energy storage capability until a cutoff temperature is reached. For broad comparison, the numerical model was used to obtain the accessed energy and power density and generate thermal Ragone plots to compare and characterize pure gallium and n-eicosane - porous foam composite with varying volume fractions, cutoff temperature, and thickness under volumetric and gravimetric constraints. Overall, the proposed framework in the form of thermal Ragone plots effectively delineates the optimal points for various combinations of heat rate, cutoff point, and aspect ratio, affirming its utility for comprehensive design guidelines for PCM-based composites for electronic cooling applications
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Figure of Merit-Based Optimization Approach of Phase Change Material-Based Composites for Portable Electronics Using Simplified Model
Abstract This work presents an approach to optimally designing a composite with thermal conductivity enhancers infiltrated with phase change material based on figure of merit (FOM) for thermal management of portable electronic devices. The FOM defines the balance between effective thermal conductivity and energy storage capacity. In this study, thermal conductivity enhancers are in the form of a honeycomb structure. Thermal conductivity enhancers are often used in conjunction with phase change material to enhance the conductivity of the composite medium. Under constrained heat sink volume, the higher volume fraction of thermal conductivity enhancers improves the effective thermal conductivity of the composite, while it reduces the amount of latent heat storage simultaneously. This work arrives at the optimal design of composite for electronic cooling by maximizing the FOM to resolve the stated tradeoff. In this study, the total volume of the composite and the interfacial heat transfer area between the phase change material and thermal conductivity enhancers are constrained for all design points. A benchmarked two-dimensional direct computational fluid dynamics model was employed to investigate the thermal performance of the phase change material and thermal conductivity enhancer composite. Furthermore, assuming conduction-dominated heat transfer in the composite, a simplified effective numerical model that solves the single energy equation with the effective properties of the phase change material and thermal conductivity enhancer has been developed. The effective properties like heat capacity can be obtained by volume averaging; however, effective thermal conductivity (required to calculate FOM) is unknown. The effective thermal conductivity of the composite is obtained by minimizing the error between the transient temperature gradient of direct and simplified model by iteratively varying the effective thermal conductivity. The FOM is maximized to find the optimal volume fraction for the present design.
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- Award ID(s):
- 1738793
- PAR ID:
- 10338900
- Date Published:
- Journal Name:
- Journal of Electronic Packaging
- Volume:
- 144
- Issue:
- 2
- ISSN:
- 1043-7398
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1115/1.4052074
