scholarly journals Study on the Thermal Conductivity of Mannitol Enhanced by Graphene Nanoparticles for Thermoelectric Power Generation

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Jia Yu ◽  
Haoqing Wang ◽  
Li Kong ◽  
Hongji Zhu ◽  
Qingshan Zhu
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Open Circuit ◽  
Stable Operation ◽  
Test Results ◽  
Temperature Environment ◽  
Large Heat ◽  
Composite Phase Change Material ◽  
Graphene Nanoparticles ◽  
Change Material

The existing thermoelectric materials are greatly affected by the temperature environment, which can provide better power output in a stable temperature environment by using composite phase change material with enhanced heat conduction. The graphene is dispersed in the liquid mannitol to make the nanomixed material. Test results show that the thermal conductivity of mannitol increased from 0.7 Wm-1 K-1 to 2.07 Wm-1 K-1, 179.73% times as much. The effective thermal conductivity of mannitol can be increased to 8.4236 Wm-1 K-1 by using a graphite foam with a porosity of 0.9. After adding 1 wt.% and 5 wt.% graphene particles, the effective thermal conductivity increased to 8.73 Wm-1 K-1 and 9.63 Wm-1 K-1, respectively. The simulation results in a large heat source environment show that mannitol with improved thermal conductivity can ensure the stable operation of the thermoelectric material in the optimal temperature environment for 120 s, and the open-circuit voltage is maintained at about 6.5 V in that time.

Figure of Merit-Based Optimization Approach of Phase Change Material-based Composites for Portable Electronics Using Simplified Model

2021 ◽  
Author(s):  
Ayushman Singh ◽  
Srikanth Rangarajan ◽  
Leila Choobineh ◽  
Bahgat Sammakia
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
Phase Change Material ◽  
Figure Of Merit ◽  
Volume Fraction ◽  
Simplified Model ◽  
Transient Temperature ◽  
Change Material

Abstract This work presents an approach to optimally designing a composite with thermal conductivity enhancers (TCEs) infiltrated with phase change material (PCM) 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 present study, TCEs are in the form of a honeycomb structure. TCEs are often used in conjunction with PCM to enhance the conductivity of the composite medium. Under constrained composite volume, the higher volume fraction of TCEs improves the effective thermal conductivity of the composite, while it reduces the amount of latent heat storage simultaneously. The present work arrives at the optimal design of composite for electronic cooling by maximizing the FOM to resolve the stated trade-off. In this study, the total volume of the composite and the interfacial heat transfer area between the PCM and TCE are constrained for all design points. A benchmarked two-dimensional direct CFD model was employed to investigate the thermal performance of the PCM and TCE 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 PCM and TCE has been developed. 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.

Effect of the Additive on Thermal Conductivity of the Phase Change Material

2011 ◽  
Vol 399-401 ◽  
pp. 1302-1306 ◽  
Author(s):  
Wei Hua Li ◽  
Jin Feng Mao ◽  
Li Jun Wang ◽  
Lu Yan Sui
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Phase Change Material ◽  
Sodium Acetate ◽  
Heat Storage ◽  
Expanded Graphite ◽  
Sodium Acetate Trihydrate ◽  
Acetate Trihydrate ◽  
Composite Phase Change Material ◽  
Change Material

The aim of the paper is to analyze the effect of the additives on thermal conductivity of the phase change material. The experiment about heat storage and heat release performance of the composite phase change material which uses sodium acetate trihydrate as host material is studied. The effect of the expanded graphite on the composite phase change material is investigated. The results show that: expanded graphite which can be dispersed evenly in the composite phase change material, the thermal stability is well, significantly improve the thermal conductivity of the composite phase change material.

Thermally regulated cotton fabric coated with expanded graphite stabilized paraffin mixture as composite phase change material

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Wei Zhang ◽  
Enzheng Xing ◽  
Shang Hao ◽  
Yonghe Xiao ◽  
Ruonan Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Latent Heat ◽  
Cotton Fabric ◽  
Expanded Graphite ◽  
Thermal Regulation ◽  
Shape Stability ◽  
Content Type ◽  
Coated Fabric ◽  
Composite Phase Change Material ◽  
Change Material

Purpose This study aims to manufacture cotton fabric with thermal regulation performance by using the composite phase change material (CPCM) prepared by coating paraffin doped with expanded graphite (EG), and the thermal effect of the fabric material was evaluated and characterized. Design/methodology/approach EG/paraffin CPCM with shape stability and enhanced thermal conductivity were prepared by the impregnation method and then finished on the surface of cotton fabric with coating technology. The microstructure, crystal structure, chemical composition, latent heat property and thermal conductivity were analyzed by scanning electron microscope, x-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimeter and thermal constant analyzer. The photo-thermal effect of the coated fabric was studied by a thermal infrared imager. Findings CPCM prepared with a mass ratio of EG to paraffin of 1:8 showed excellent shape stability and low paraffin leakage rate. The latent heat of the CPCM was 51.6201 J/g and the thermal conductivity coefficient was increased by 11.4 times compared with the mixed paraffin. After the CPCM was coated on the surface of the cotton fabric, the light-to-heat conversion rate of the C-EG/PA3 sample was improved by 86.32% compared with the original fabric. In addition, the coated fabric showed excellent thermal stability and heat storage performance in the thermal cycling test. Research limitations/implications EG can improve the shape stability and thermal conductivity of paraffin but will reduce the latent heat energy. Practical implications The method developed provided a simple and practical solution to improving the thermal regulation performance of fabrics. Originality/value Combining paraffin wax with fabrics in a composite way is innovative and has certain applicability in improving the thermal properties of fabrics.

Characterization of Thermal Properties and Heat Transfer Behavior of Microencapsulated Phase Change Material Slurry and Multiwall Carbon Nanotubes in Aqueous Suspension

2007 ◽  
Author(s):  
Jorge L. Alvarado ◽  
Charles Marsh ◽  
Curt Thies ◽  
Guillermo Soriano ◽  
Paritosh Garg
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Effective Thermal Conductivity ◽  
Phase Change Material ◽  
Microencapsulated Phase Change Material ◽  
Change Material

In the last decade, microencapsulated phase change material (MPCM) slurries have been proposed and studied as novel coolants for heat transfer applications. Such applications include electronics cooling, and secondary coolants in air conditioning systems among others. Experiments have shown that MPCM’s increase the overall thermal capacity of thermal systems by taking advantage of the phase change material’s latent heat of fusion. However, research has also shown that the overall heat transfer coefficient is diminished due to a reduction in the effective thermal conductivity and increased viscosity of the slurry. For this reason, there is an urgent need to modify the content of microcapsules containing phase change material to increase their effective thermal conductivity and the overall heat transport process. Our solution consists of increasing the thermal conductivity of MPCM by adding carbon nanotubes to the shell and core of the microcapsules. Carbon nanotubes have shown to increase the thermal conductivity of liquids by 40% or more in recent experiments. In this paper, MPCM slurry containing octadecane as phase change material and multi-wall carbon nanotubes (MWCNTs) embedded in the capsule material and core are compared with pure water as heat transfer fluid. Thermal and physical properties of MPCM slurry containing carbon nanotubes were determined using a differential scanning calorimeter and concentric viscometer, respectively. Experimental convective heat transfer coefficient data for MWCNT aqueous suspensions under laminar flow and constant heat flux were determined using a bench-top heat transfer loop. Experimental heat transfer results are presented.

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