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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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Temperature Dependence of Thermal Conductivity of Proteins: Contributions of Thermal Expansion and Grüneisen Parameter
Abstract The thermal conductivity of many materials depends on temperature due to several factors, including variation of heat capacity with temperature, changes in vibrational dynamics with temperature, and change in volume with temperature. For proteins some, but not all, of these influences on the variation of thermal conductivity with temperature have been investigated in the past. In this study, we examine the influence of change in volume, and corresponding changes in vibrational dynamics, on the temperature dependence of the thermal conductivity. Using a measured value for the coefficient of thermal expansion and recently computed values for the Grüneisen parameter of proteins we find that the thermal conductivity increases with increasing temperature due to change in volume with temperature. We compare the impact of thermal expansion on the variation of the thermal conductivity with temperature found in this study with contributions of heat capacity and anharmonic coupling examined previously. Using values of thermal transport coefficients computed for proteins we also model heating of water in a protein solution following photoexcitation.
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- Award ID(s):
- 2245240
- PAR ID:
- 10642585
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemPhysChem
- Volume:
- 26
- Issue:
- 6
- ISSN:
- 1439-4235
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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