scholarly journals Enhanced Electrical Insulation and Heat Transfer Performance of Vegetable Oil Based Nanofluids

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Wei Yao ◽  
Zhengyong Huang ◽  
Jian Li ◽  
Liya Wu ◽  
Chenmeng Xiang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Electric Field ◽  
Vegetable Oil ◽  
Hexagonal Boron Nitride ◽  
Thermal Response ◽  
Electrical Insulation ◽  
High Thermal Conductivity ◽  
Heating And Cooling ◽  
Cooling Effects

Nanoparticles enhance the electrical insulation and thermal properties of vegetable oil, and such improvements are desirable for its application as an alternative to traditional insulating oil for power transformers. However, the traditional method of insulating nanofluids typically achieves high electrical insulation but low thermal conductivity. This work reports an environmentally friendly vegetable oil using exfoliated hexagonal boron nitride (h-BN) showing high thermal conductivity and high electrical insulation. Stable nanofluids were prepared by liquid exfoliation of h-BN in isopropyl alcohol. With 0.1 vol.% of the nano-oil, the AC breakdown voltage increased by 18% at 25°C and 15% at 90°C. Both the positive and negative lightning impulse breakdown voltages of the nano-oil were also enhanced compared with those of the pure oil. Moreover, the thermal conductivity of the nano-oil increased by 11.9% at 25°C and 14% at 90°C. Given its high thermal conductivity, the nano-oil exhibited faster heating and cooling effects than the pure oil. Nano-oils with an electric field (either DC or AC) displayed a faster thermal response than that without an electric field. The reason is that h-BN is oriented under the electric field and formed a thermal network to increase the heat transfer.

scholarly journals Aerogel Perfusion-Prepared h-BN/CNF Composite Film with Multiple Thermally Conductive Pathways and High Thermal Conductivity

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 1051 ◽  
Author(s):  
Xiu Wang ◽  
Zhihuai Yu ◽  
Liang Jiao ◽  
Huiyang Bian ◽  
Weisheng Yang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Composite Film ◽  
Hexagonal Boron Nitride ◽  
Traditional Approach ◽  
Synthetic Polymer ◽  
Electrical Insulation ◽  
High Thermal Conductivity ◽  
Polymer Materials ◽  
Thermally Conductive ◽  
Electrical Insulation Properties

Hexagonal boron nitride (h-BN)-based heat-spreading materials have drawn considerable attention in electronic diaphragm and packaging fields because of their high thermal conductivity and desired electrical insulation properties. However, the traditional approach to fabricate thermally conductive composites usually suffers from low thermal conductivity, and cannot meet the requirement of thermal management. In this work, novel h-BN/cellulose-nano fiber (CNF) composite films with excellent thermal conductivity in through plane and electrical insulation properties are fabricated via an innovative process, i.e., the perfusion of h-BN into porous three dimensional (3D) CNF aerogel skeleton to form the h-BN thermally conductive pathways by filling the CNF aerogel voids. When at an h-BN loading of 9.51 vol %, the thermal conductivity of h-BN/CNF aerogel perfusion composite film is 1.488 W·m−1·K−1 at through plane, an increase by 260.3%. The volume resistivity is 3.83 × 1014 Ω·cm, superior to that of synthetic polymer materials (about 109~1013 Ω·cm). Therefore, the resulting h-BN/CNF film is very promising to replace the traditional synthetic polymer materials for a broad spectrum of applications, including the field of electronics.

Sandwich-structured PVA/rGO films from self-construction with high thermal conductivity and electrical insulation

2021 ◽  
Vol 207 ◽  
pp. 108707
Author(s):  
Fanghua Luo ◽  
Min Zhang ◽  
Songlin Chen ◽  
Jianfeng Xu ◽  
Chen Ma ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Insulation ◽  
High Thermal Conductivity

scholarly journals High-Fidelity Calculation of Effective Thermal Response of Composite Media With Heat Generation Source

2020 ◽  
Author(s):  
Kevin Irick ◽  
Nima Fathi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Nuclear Fuel ◽  
Heat Generation ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Unit Cell ◽  
High Fidelity ◽  
Conductive Heat

Abstract The complexity of conductive heat transfer in a structure increases with heterogeneity (e.g., multi-component solid-phase systems with a source of internal thermal heat generation). Any discontinuity of material property — especially thermal conductivity — would warrant a thorough analysis to evaluate the thermal behavior of the system of interest. Heterogeneous thermal conditions are crucial to heat transfer in nuclear fuel assemblies, because the thermal behavior within the assemblies is governed significantly by the heterogeneous thermal conditions at both the system and component levels. A variety of materials have been used as nuclear fuels, the most conventional of which is uranium dioxide, UO2. UO2 has satisfactory chemical and irradiation tolerances in thermal reactors, whereas the low thermal conductivity of porous UO2 can prove challenging. Therefore, the feasibility of enhancing the thermal conductivity of oxide fuels by adding a high-conductivity secondary solid component is still an important ongoing topic of investigation. Undoubtedly, long-term, stable development of clean nuclear energy would depend on research and development of innovative reactor designs and fuel systems. Having a better understanding of the thermal response of the unit cell of a composite that represents a fuel matrix cell would help to develop the next generation of nuclear fuel and understand potential performance enhancements. The aim of this article is to provide an assessment of a high-fidelity computational model response of heterogeneous materials with heat generation in circular fillers. Two-dimensional, steady-state systems were defined with a circular, heat-generating filler centered in a unit-cell domain. A Fortran-based finite element method (FEM) code was used to solve the heat equation on an unstructured triangular mesh of the systems. This paper presents a study on the effects of a heat-generating filler material’s relative size and thermal conductivity on effective thermal conductance, Geff, within a heterogenous material. Code verification using the method of manufactured solution (MMS) was employed, showing a second-order accurate numerical implementation. Solution verification was performed using a global deviation grid convergence index (GCI) method to assess solution convergence and estimate solution numerical uncertainty, Unum. Trend results are presented, showing variable response in Geff to filler size and thermal conductivity.

The flexible film of SCF/BN/PDMS composites with high thermal conductivity and electrical insulation

2021 ◽  
Vol 23 ◽  
pp. 100573
Author(s):  
Houbao Liu ◽  
Xinqing Su ◽  
Renli Fu ◽  
Binyong Wu ◽  
Xudong Chen
Keyword(s):  
Thermal Conductivity ◽  
Electrical Insulation ◽  
High Thermal Conductivity ◽  
Flexible Film

scholarly journals Measurement of Thermal Conductivity along the Radial Direction in a Vertical Cylindrical Packed Bed

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Swaren Bedarkar ◽  
Nurni Neelakantan Viswanathan ◽  
Nidambur Bharatha Ballal
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Crucial Role ◽  
Iron Ore ◽  
Radial Direction ◽  
Thermal Response ◽  
Packed Bed ◽  
Lumped Parameter ◽  
Scientists And Engineers

Heat transfer in packed beds and their thermal response have been of great interest for scientists and engineers for the last several years, since they play a crucial role in determining design and operation of reactors. Heat transfer of a packed bed is characterised through lumped parameter, namely, effective thermal conductivity. In the present studies, experiments were performed to investigate the thermal conductivity of a packed bed in radial direction. The packed bed was formed using iron ore particles. To determine the effective thermal conductivity a new transient methodology is proposed. The results obtained were compared with the models proposed by ZBS and Kunii and Smith.

scholarly journals Recent Progress in the Study of Thermal Properties and Tribological Behaviors of Hexagonal Boron Nitride-Reinforced Composites

2020 ◽  
Vol 4 (3) ◽  
pp. 116
Author(s):  
Maryam Khalaj ◽  
Sanaz Zarabi Golkhatmi ◽  
Sayed Ali Ahmad Alem ◽  
Kahila Baghchesaraee ◽  
Mahdi Hasanzadeh Azar ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Boron Nitride ◽  
Recent Progress ◽  
Phonon Scattering ◽  
Hexagonal Boron Nitride ◽  
High Thermal Conductivity ◽  
Promising Candidate ◽  
Reinforced Composite ◽  
Low Thermal Expansion ◽  
Wide Range

Ever-increasing significance of composite materials with high thermal conductivity, low thermal expansion coefficient and high optical bandgap over the last decade, have proved their indispensable roles in a wide range of applications. Hexagonal boron nitride (h-BN), a layered material having a high thermal conductivity along the planes and the band gap of 5.9 eV, has always been a promising candidate to provide superior heat transfer with minimal phonon scattering through the system. Hence, extensive researches have been devoted to improving the thermal conductivity of different matrices by using h-BN fillers. Apart from that, lubrication property of h-BN has also been extensively researched, demonstrating the effectivity of this layered structure in reduction of friction coefficient, increasing wear resistance and cost-effectivity of the process. Herein, an in-depth discussion of thermal and tribological properties of the reinforced composite by h-BN will be provided, focusing on the recent progress and future trends.

scholarly journals Recent Advances in Heat Transfer Enhancements: A Review Report

2010 ◽  
Vol 2010 ◽  
pp. 1-28 ◽  
Author(s):  
M. Siddique ◽  
A.-R. A. Khaled ◽  
N. I. Abdulhafiz ◽  
A. Y. Boukhary
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Porous Media ◽  
High Thermal Conductivity ◽  
Vortex Generators ◽  
Two Phase ◽  
Enhancement Method ◽  
Enhancing Heat Transfer ◽  
Porous Fins ◽  
Two Phase Heat Transfer

Different heat transfer enhancers are reviewed. They are (a) fins and microfins, (b) porous media, (c) large particles suspensions, (d) nanofluids, (e) phase-change devices, (f) flexible seals, (g) flexible complex seals, (h) vortex generators, (i) protrusions, and (j) ultra high thermal conductivity composite materials. Most of heat transfer augmentation methods presented in the literature that assists fins and microfins in enhancing heat transfer are reviewed. Among these are using joint-fins, fin roots, fin networks, biconvections, permeable fins, porous fins, capsulated liquid metal fins, and helical microfins. It is found that not much agreement exists between works of the different authors regarding single phase heat transfer augmented with microfins. However, too many works having sufficient agreements have been done in the case of two phase heat transfer augmented with microfins. With respect to nanofluids, there are still many conflicts among the published works about both heat transfer enhancement levels and the corresponding mechanisms of augmentations. The reasons beyond these conflicts are reviewed. In addition, this paper describes flow and heat transfer in porous media as a well-modeled passive enhancement method. It is found that there are very few works which dealt with heat transfer enhancements using systems supported with flexible/flexible-complex seals. Eventually, many recent works related to passive augmentations of heat transfer using vortex generators, protrusions, and ultra high thermal conductivity composite material are reviewed. Finally, theoretical enhancement factors along with many heat transfer correlations are presented in this paper for each enhancer.

Thermal Aspects of Grinding: The Effect of the Wheel Bond on Heat Transfer to an Abrasive Grain

1991 ◽  
Vol 113 (4) ◽  
pp. 395-401 ◽  
Author(s):  
M. W. Harris ◽  
A. S. Lavine
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Heat Conduction ◽  
Beneficial Effect ◽  
Surface Temperature ◽  
Thermal Damage ◽  
High Thermal Conductivity ◽  
Abrasive Grain ◽  
Grain Surface

Heat generated during grinding can cause thermal damage to the workpiece and wheel. It is therefore important to understand the thermal aspects of grinding. This paper addresses heat conduction into the wheel, by considering a single abrasive grain in contact with the workpiece. In particular, the effect of the bond material on conduction into the grain is investigated. The results for the grain surface temperature are given in terms of parameters describing the geometry and thermal properties of the grain and bond. The beneficial effect of a high thermal conductivity for both the grain and the bond is clearly demonstrated.

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