scholarly journals Comprehensive Experimental Study on the Thermophysical Characteristics of DI Water Based Co0.5Zn0.5Fe2O4 Nanofluid for Solar Thermal Harvesting

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6218
Author(s):  
Tsogtbilegt Boldoo ◽  
Jeonggyun Ham ◽  
Honghyun Cho
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Energy Conversion ◽  
Thermophysical Properties ◽  
Base Fluid ◽  
Energy Conversion Efficiency ◽  
Thermophysical Characteristics ◽  
Magnetic Nanofluid ◽  
Solar Exposure ◽  
Water Based

The thermophysical properties of water-based Co0.5Zn0.5Fe2O4 magnetic nanofluid were investigated experimentally. Consequently, the viscosities of 0.25 wt% and 1 wt% Co0.5Zn0.5Fe2O4 nanofluid were 1.03 mPa∙s and 1.13 mPa∙s, each greater than that of the 20 °C base fluid (water), which were increased by 7.3% and 17.7%, respectively. The Co0.5Zn0.5Fe2O4 nanofluid thermal conductivity enhanced from 0.605 and 0.618 to 0.654 and 0.693 W/m·°C at concentrations of 0.25 wt% and 1 wt%, respectively, when the temperature increased from 20 to 50 °C. The maximum thermal conductivity of the Co0.5Zn0.5Fe2O4 nanofluid was 0.693 W/m·°C at a concentration of 1 wt% and a temperature of 50 °C. Furthermore, following a solar exposure of 120 min, the photothermal energy conversion efficiency of 0.25 wt%, 0.5 wt%, 0.75 wt%, and 1 wt% Co0.5Zn0.5Fe2O4 nanofluids increased by 4.8%, 5.6%, 7.1%, and 4.1%, respectively, more than that of water.

Thermophysical Properties for ZnO-Water Nanofluid: Experimental Study

2021 ◽  
Vol 1025 ◽  
pp. 9-14
Author(s):  
Adnan H. Rasheed ◽  
Hajar Alias ◽  
Sami D. Salman
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Experimental Study ◽  
Zinc Oxide ◽  
Thermophysical Properties ◽  
Base Fluid ◽  
Volume Fraction ◽  
Nanoparticle Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Rotational Viscometer

This paper presents the thermophysical properties of zinc oxide nanofluid that have been measured for experimental investigation. The main contribution of this study is to define the heat transfer characteristics of nanofluids. The measuring of these properties was carried out within a range of temperatures from 25 °C to 45 °C, volume fraction from 1 to 2 %, and the average nanoparticle diameter size is 25 nm, and the base fluid is water. The thermophysical properties, including viscosity and thermal conductivity, were measured by using Brookfield rotational Viscometer and Thermal Properties Analyzer, respectively. The result indicates that the thermophysical properties of zinc oxide nanofluid increasing with nanoparticle volume fraction increasing, as well as the thermophysical properties of zinc oxide nanofluid affected by the change in temperature.

EXAMINATION OF THERMOPHYSICAL CHARACTERISTICS OF A HEAT-PROTECTIVE MATERIAL BASED ON FIBERGLASS DURING DESTRUCTION

2021 ◽  
pp. 91-97
Author(s):  
D.Ya. Barinov ◽  
◽  
S.Yu. Shorstov ◽  
M.G. Razmahov ◽  
A.I. Gulyaev ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermophysical Properties ◽  
Thermal Effects ◽  
Space Technology ◽  
Muffle Furnace ◽  
Thermophysical Characteristics ◽  
Initial State ◽  
Protective Material ◽  
Temperature Dependences

When designing advanced samples of aviation and rocket and space technology, during the operation of which the temperature on the surface of the material can exceed the temperature of destruction, it is important to have an understanding of the values of thermophysical properties. The work investigates the thermophysical properties of fiberglass in the initial state and after the binder is burned out in a muffle furnace. The temperature dependences of thermal effects, heat capacity, thermal diffusivity and thermal conductivity were determined, density was measured, and thermogravimetric analysis was carried out. Using a stereomicroscope, the microstructure of the lateral cut of the samples was examined and its evolution was determined during the burning of the binder.

Thermoelectric Transport in Silicon Germanium Nanocomposite

2008 ◽  
Author(s):  
Hohyun Lee ◽  
Daryoosh Vashaee ◽  
Xiaowei Wang ◽  
Giri Joshi ◽  
Gaohua Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Silicon Germanium ◽  
Figure Of Merit ◽  
Waste Heat ◽  
Electrical Energy ◽  
Energy Conversion Efficiency ◽  
Thermoelectric Effects ◽  
Thermoelectric Transport ◽  
Potential Applications

Direct energy conversion between heat and electrical energy based on thermoelectric effects is attractive for potential applications in waste heat recovery and environmentally-friendly refrigeration. The energy conversion efficiency depends on the dimensionless figure of merit of thermoelectric materials, ZT, which is proportional to the electrical conductivity, the square of the Seebeck coefficient, and the inverse of the thermal conductivity. Currently, the low ZT values of available materials restrict the applications of this technology. However, significant enhancements in ZT were recently reported in nanostructured materials such as superlattices mainly due to their low thermal conductivities. According to recent studies, the reduced thermal conductivity of nanostructures is attributed to the large number of interfaces at which phonons are scattered. Based on this idea, nanocomposites are expected to have a lower thermal conductivity than their bulk counterparts with low fabrication cost just by mixing nano sized particles. In this work, we will discuss mechanisms of thermoelectric transport via modeling and provide experimental evidence on the enhancement of thermoelectric figure of merit in SiGe-based nanocomposites.

Experimental Measurement of Thermophysical Properties of Alumina- MWCNTs/Salt–Water Hybrid Nanofluids

2020 ◽  
Vol 16 (5) ◽  
pp. 734-747 ◽  
Author(s):  
Amir Hossein Sharifi ◽  
Iman Zahmatkesh ◽  
Fatemeh F. Bamoharram ◽  
Amir Hossein Shokouhi Tabrizi ◽  
Safieh Fazel Razavi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Salt Concentration ◽  
Thermophysical Properties ◽  
Base Fluid ◽  
Volume Fraction ◽  
Ph Value ◽  
Nanoparticle Volume Fraction ◽  
Optimal Conditions ◽  
Hybrid Nanofluids

Background: Hybrid nanofluids are considered as an extension of conventional nanofluids which are prepared through suspending two or more nanoparticles in the base fluids. Previous studies on hybrid nanofluids have measured their thermal conductivity overlooking other thermophysical properties such as viscosity and electrical conductivity. Objective: An experimental investigation is undertaken to measure thermal conductivity, viscosity, and electrical conductivity of a hybrid nanofluid prepared through dispersing alumina nanoparticles and multiwall carbon nanotubes in saltwater. These properties are the main important factors that must be assessed before performance analysis for industrial applications. Methods: The experimental data were collected for different values of the nanoparticle volume fraction, temperature, salt concentration, and pH value. Attention was paid to explore the consequences of these parameters on the nanofluid’s properties and to find optimal conditions to achieve the highest value of the thermal conductivity and the lowest values of the electrical conductivity and the viscosity. Results: The results demonstrate that although the impacts of the pH value and the nanoparticle volume fraction on the nanofluid’s thermophysical properties are not monotonic, optimal conditions for each of the properties are reachable. It is found that the inclusion of the salt in the base fluid may not change the thermal conductivity noticeably. However, a considerable reduction in the viscosity and substantial elevation in the electrical conductivity occur with an increase in the salt concentration. Conclusion: With the addition of salt to a base fluid, the thermophysical properties of a nanofluid can be controlled.

scholarly journals Schemes for and Mechanisms of Reduction in Thermal Conductivity in Nanostructured Thermoelectrics

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Xiaoliang Zhang ◽  
Ming Hu ◽  
Konstantinos P. Giapis ◽  
Dimos Poulikakos
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Longitudinal Direction ◽  
Energy Conversion Efficiency ◽  
Nonequilibrium Molecular Dynamics ◽  
Boundary Scattering ◽  
Nanowire Surface ◽  
Simulation Results ◽  
Nanocomposite Structures

Nonequilibrium molecular dynamics (NEMD) simulations were performed to investigate schemes for enhancing the energy conversion efficiency of thermoelectric nanowires (NWs), including (1) roughening of the nanowire surface, (2) creating nanoparticle inclusions in the nanowires, and (3) coating the nanowire surface with other materials. The enhancement in energy conversion efficiency was inferred from the reduction in thermal conductivity of the nanowire, which was calculated by imposing a temperature gradient in the longitudinal direction. Compared to pristine nanowires, our simulation results show that the schemes proposed above lead to nanocomposite structures with considerably lower thermal conductivity (up to 82% reduction), implying ∼5X enhancement in the ZT coefficient. This significant effect appears to have two origins: (1) increase in phonon-boundary scattering and (2) onset of interfacial interference. The results suggest new fundamental–yet realizable ways to improve markedly the energy conversion efficiency of nanostructured thermoelectrics.

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