Enhancement of thermophysical coefficients in nanofluids: A simulation study

2020 ◽  
Vol 34 (25) ◽  
pp. 2050222
Author(s):  
Xiandai Cui ◽  
Xiaomin Cheng ◽  
Hong Xu ◽  
Bei Li ◽  
Jiaoqun Zhu
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermophysical Properties ◽  
Phase Change Materials ◽  
Nonequilibrium Molecular Dynamics ◽  
Microscopic Mechanism ◽  
Dynamics Simulations ◽  
First Time

Molten salts constitute one kind of PCMs (Phase Change Materials) widely used in concentrating solar power facilities for heat storage and heat transfer. This paper aims to simulate nanofluid PCMs with molecular dynamics method. Concretely, the thermophysical properties of a nanofluid of KNO3 doped with SiO2 nanoparticle are investigated by equilibrium and nonequilibrium molecular dynamics simulations. For the first time, these properties of a nanofluid in the family of PCMs are calculated. The density, thermal expansion coefficient, specific heat capacity, thermal conductivity, and viscosity are characterized as functions of the SiO2 nanoparticle concentration. The effect of the SiO2 nanoparticle size on the nanofluid’s properties is also investigated. The simulation results present an enhancement of the thermophysical properties, especially for the specific heat capacity, in good agreement with the existing experimental results on a representative nanofluid PCM, and open prospects for the understanding of microscopic mechanism leading to such enhancements.

Experimental Study on the Specific Heat Capacity Measurement of Water-Based Al2O3-Cu Hybrid Nanofluid by using Differential Thermal Analysis Method

2019 ◽  
Vol 15 ◽  
Author(s):  
Andaç Batur Çolak ◽  
Oğuzhan Yıldız ◽  
Mustafa Bayrak ◽  
Ali Celen ◽  
Ahmet Selim Dalkılıç ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermophysical Properties ◽  
Volume Concentration ◽  
Pure Water ◽  
Heat Capacity Measurement ◽  
Experimental Results ◽  
Hybrid Nanofluid ◽  
Capacity Measurement

Background: Researchers working in the field of nanofluid have done many studies on the thermophysical properties of nanofluids. Among these studies, the number of studies on specific heat are rather limited. In the study of the heat transfer performance of nanofluids, it is necessary to increase the number of specific heat studies, whose subject is one of the important thermophysical properties. Objective: The authors aimed to measure the specific heat values of Al2O3/water, Cu/water nanofluids and Al2O3-Cu/water hybrid nanofluids using the DTA method, and compare the results with those frequently used in the literature. In addition, this study focuses on the effect of temperature and volume concentration on specific heat. Method: The two-step method was used in the preparation of nanofluids. The pure water selected as the base fluid was mixed with the Al2O3 and Cu nanoparticles and Arabic Gum as the surfactant, firstly mixed in the magnetic stirrer for half an hour. It was then homogenized for 6 hours in the ultrasonic homogenizer. Results: After the experiments, the specific heat of nanofluids and hybrid nanofluid were compared and the temperature and volume concentration of specific heat were investigated. Then, the experimental results obtained for all three fluids were compared with the two frequently used correlations in the literature. Conclusion: Specific heat capacity increased with increasing temperature, and decreased with increasing volume concentration for three tested nanofluids. Cu/water has the lowest specific heat capacity among all tested fluids. Experimental specific heat capacity measurement results are compared by using the models developed by Pak and Cho and Xuan and Roetzel. According to experimental results, these correlations can predict experimental results within the range of ±1%.

Multicanonical Molecular Dynamics Simulation Study of the Liquid-Solid and Solid-Solid Transitions in Lennard-Jones Clusters

2011 ◽  
Author(s):  
Toshihiro Kaneko ◽  
Kenji Yasuoka ◽  
Ayori Mitsutake ◽  
Xiao Cheng Zeng
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Transition Temperature ◽  
Peak Position ◽  
Temperature Curve ◽  
Dynamics Simulation ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
First Time ◽  
Good Agreement

Multicanonical molecular dynamics simulations are applied, for the first time, to study the liquid-solid and solid-solid transitions in Lennard-Jones (LJ) clusters. The transition temperatures are estimated based on the peak position in the heat capacity versus temperature curve. For LJ31, LJ58 and LJ98, our results on the solid-solid transition temperature are in good agreement with previous ones. For LJ309, the predicted liquid-solid transition temperature is also in agreement with previous result.

Thermal Analysis of Phase Change Material Based Heat Transfer Fluid in Solar Thermal Collector

2020 ◽  
Author(s):  
Tyler J. E. O’Neil ◽  
Celine S. L. Lim ◽  
Sarvenaz Sobhansarbandi
Keyword(s):  
Heat Capacity ◽  
Phase Change ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Phase Change Materials ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Liquid Form ◽  
High Specific Heat ◽  
Multi Walled Carbon Nanotubes

Abstract Phase change materials (PCMs) are commonly used as energy storage mediums in solar thermal systems. This paper investigates the mixture of PCM doped with nanoparticles to be used as HTFs directly integrated in a U-pipe ETC to be applied in solar thermal collectors. The selected type of PCM-HTF in this study is erythritol (C4H10O4), with high specific heat capacity in liquid form, as well as its unique sub-cooling behavior. In order to overcome the low thermal conductivity of erythritol and further enhance specific heat capacity, a weight concentration of 1% multi-walled carbon nanotubes (MWCNT) is added. Additionally, to insure even distribution of MWCNT and consistent properties of the HTF, triethanolamine (TEA) is proposed to be incorporated as a dispersant. The samples were each tested in a Thermogravimetric Analyzer (TGA) and Differential Scanning Calorimeter (DSC) to analyze their thermal properties. The results from the DSC tests show 12.4% enhancement of specific heat capacity of the proposed HTF mixture as well as nearly 5° C depression of freezing onset temperature. This study allows for the optimization of the operating temperature range of the collector when integrated with these materials, where direct heat gain can be obtained in the collector.

Physical properties of high-temperature solid alkali chlorides by molecular dynamics simulation using a recent EIM interatomic potential

2019 ◽  
Vol 33 (10) ◽  
pp. 1950088 ◽  
Author(s):  
Xiandai Cui ◽  
Jiaoqun Zhu ◽  
Hong Xu ◽  
Xiaomin Cheng ◽  
Weibing Zhou
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Interatomic Potential ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Experimental Values ◽  
Alkali Chlorides ◽  
Change Material

Thermophysical properties of phase change material NaCl and KCl were calculated using molecular dynamics (MD) simulations and a recent EIM interatomic potential. Density, thermal expansion coefficient, specific heat capacity were computed using equilibrium MD (EMD) simulations. The results are very close to the experimental values. The thermal conductivity was computed using two non-equilibrium MD (NEMD) methods and the results were compared with the experimental data. They appear to be relatively reasonable. Binary NaCl/KCl systems have also been investigated. The specific heat capacity with different compositions are calculated. They are very close with recent experimental results.

scholarly journals Determination of effective specific heat capacity of interior plaster containing phase change materials

2019 ◽  
Vol 282 ◽  
pp. 02052
Author(s):  
Václav Kočí ◽  
Jiří Maděra ◽  
Robert Černý
Keyword(s):  
Heat Capacity ◽  
Phase Change ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Building Materials ◽  
Phase Change Materials ◽  
Calorimetric Data ◽  
Thermal Oscillation ◽  
Effective Specific Heat

A precise technique for determination of effective specific heat capacity of building materials is presented within this paper. The applicability of the technique is demonstrated on a PCM-enhanced plaster, being characterized by a phase change between 15 and 30 °C. The effective specific heat capacity is determined by means of inverse analysis of calorimetric data using computational model of the device. The identified effective specific heat capacity values reached up to 1890 J·kg-1·K-1 when cooled and 1580 J·kg-1·K-1 when heated. Using this quantity in simulation of thermal performance, the PCM-enhanced plaster showed to have a promising potential to be used in buildings’ interiors as a thermal regulator to stabilize inner environment as it contributed to a thermal oscillation decrease by up to 2.5 °C

Thermal Conductivity and Specific Heat Capacity of Carbon Nanotube Bundles

2007 ◽  
Author(s):  
John Shelton ◽  
Frank Pyrtle
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Heat Capacity ◽  
Carbon Nanotube ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Element Analysis ◽  
Single Walled Carbon ◽  
Nanotube Bundles ◽  
Dynamics Simulations

Carbon nanotubes (CNTs) have been thoroughly documented to demonstrate superior heat transfer properties. It has also been determined that these properties decrease substantially as overall dimensions increase from the nanoscale to the microscale. Using non-equilibrium molecular dynamics simulations and finite element analysis, the influence of both internal and external thermal boundary resistance effects on the thermal conductivity and specific heat capacity of single walled carbon nanotube bundles were investigated. Comparisons were made between accepted property values for single CNTs and for CNT bundles. Also, energy transfer between varying sized bundles of single-walled carbon nanotubes (SWCNTs) and a surrounding pressure-driven Lennard-Jones (LJ) fluid were calculated.

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