Effective heat conductivity of Honeycomb (porous) composite panel

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Cletus Matthew Magoda ◽  
Jasson Gryzagoridis ◽  
Kant Kanyarusoke
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Composite Material ◽  
Thermal Properties ◽  
Heat Conductivity ◽  
Composite Panel ◽  
Porous Composite ◽  
Content Type ◽  
One Dimensional ◽  
Coefficient Of Thermal Conductivity

Purpose The purpose of this paper is to validate an assumption of what to use as an effective (steady state) heat transfer coefficient of thermal conductivity for the honeycomb core sandwiched by Fiberglass face sheets composite. A one-dimensional model based on Fourier law is developed. The results are validated experimentally. Design/methodology/approach The results were obtained from the one-dimensional mathematical model of an overall or effective heat conductivity of the Honeycomb composite panel. These results were validated experimentally by applying heat flux on the specimen under controlled environment. The surface temperatures at different voltages were recorded and analysed. The skin of the sandwich composite material used in the investigation was Fiberglass sheet with a thickness of 0.5 mm at the bottom and 1.0 mm at the top surface. Both skins have a stacking sequence of zero degrees. Due to the presence of air cells in the core (Honeycomb), the model considers the conduction, convection and radiation heat transfer, across the thickness of the panel, combined as an effective conduction mode, whose value may be predicted by using the coefficient of thermal conductivity of the air based on the average temperature difference between the two skins. The experimental results for the heat transfer through the thickness of the panel provide validation of this assumption/prediction. Both infrared thermography and conventional temperature measurement techniques (thermocouples) were used to collect the data. Findings The heat transfer experiment and mathematical modeling were conducted. The data obtained were analyzed, and it was found that the effective thermal conductivity was temperature-dependent as expected. The effective thermal conductivity of the honeycomb panel was close to that of air, and its value could be predicted if the panel surface temperatures were known. It was also found that as temperature raised the variation between experimental and predicted effective air conduction raised up. This is because there was an increase in molecular diffusion and vibration. Therefore, the convection heat transfer increased at high temperatures and the air became an insulator. Originality/value Honeycomb composite panels have excellent physical and thermal properties that influence their performance. This study provides an appropriate method in determining thermal conductivity, which is one of the critical thermal properties of porous composite material. This paper also gives useful and practical data to industries that use or manufacture honeycomb composite panels.

scholarly journals Теплопроводность цепочки ротаторов с двухбарьерным потенциалом взаимодействия

2021 ◽  
Vol 63 (7) ◽  
pp. 975
Author(s):  
А.П. Клинов ◽  
М.А. Мазо ◽  
В.В. Смирнов
Keyword(s):  
Thermal Conductivity ◽  
Heat Conductivity ◽  
Normal Modes ◽  
Double Barrier ◽  
One Dimensional ◽  
Internal Barrier ◽  
Local Fluctuations ◽  
Small Height ◽  
Coefficient Of Thermal Conductivity ◽  
Height Dependence

The thermal conductivity of a one-dimensional chain of rotators with a double-barrier interaction potential of nearest neighbors has been studied numerically. We show that the height of the "internal" barrier, which separates topologically nonequivalent degenerate states, significantly affects the temperature dependence of the heat conductivity of the system. The small height of this barrier leads to the dominant contribution of the non-linear normal modes at low temperatures. In such a case the coefficient of thermal conductivity turns out to be the risen function of the temperature. The growth of the coefficient is limited by local fluctuations corresponding to jumps over the barriers. At higher values of the internal barrier height, dependence of the heat conductivity on temperature is similar to that of classical rotators.

Rheology effect and enhanced thermal conductivity of diamond/metakaolin geopolymer fabricated by direct ink writing

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yushen Wang ◽  
Wei Xiong ◽  
Danna Tang ◽  
Liang Hao ◽  
Zheng Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Diamond Powder ◽  
Thermal Imager ◽  
Corrosion Properties ◽  
Content Type ◽  
Sensor Material ◽  
Direct Ink Writing ◽  
Diamond Particles ◽  
Before And After

Purpose Traditional simulation research of geological and similar engineering models, such as landslides or other natural disaster scenarios, usually focuses on the change of stress and the state of the model before and after destruction. However, the transition of the inner change is usually invisible. To optimize and make models more intelligent, this paper aims to propose a perceptible design to detect the internal temperature change transformed by other energy versions like stress or torsion. Design/methodology/approach In this paper, micron diamond particles were embedded in 3D printed geopolymers as a potential thermal sensor material to detect the inner heat change. The authors use synthetic micron diamond powder to reinforced the anti-corrosion properties and thermal conductivity of geopolymer and apply this novel geopolymer slurry in the direct ink writing (DIW) technique. Findings As a result, the addition of micron diamond powder can greatly influence the rheology of geopolymer slurry and make the geopolymer slurry extrudable and suitable for DIW by reducing the slope of the viscosity of this inorganic colloid. The heat transfer coefficient of the micron diamond (15 Wt.%)/geopolymer was 50% higher than the pure geopolymer, which could be detected by the infrared thermal imager. Besides, the addition of diamond particles also increased the porous rates of geopolymer. Originality/value In conclusion, DIW slurry deposition of micron diamond-embedded geopolymer (MDG) composites could be used to manufacture the multi-functional geological model for thermal imaging and defect detection, which need the characteristic of lightweight, isolation, heat transfer and wave absorption.

Determination of the Thermal Properties of a PCB by Coupled Numerical and Experimental Approach

2020 ◽  
Author(s):  
Yener Usul ◽  
Mustafa Özçatalbaş
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Numerical Analysis ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Analyses ◽  
Analysis Model ◽  
Linear Temperature ◽  
Coefficient Of Thermal Conductivity

Abstract Increasing demand for usage of electronics intensely in narrow enclosures necessitates accurate thermal analyses to be performed. Conduction based FEM (Finite Element Method) is a common and practical way to examine the thermal behavior of an electronic system. First step to perform a numerical analysis for any system is to set up the correct analysis model. In this paper, a method for obtaining the coefficient of thermal conductivity and specific heat capacity of a PCB which has generally a complex composite layup structure composed of conductive layers, and dielectric layers. In the study, above mentioned properties are obtained performing a simple nondestructive experiment and a numerical analysis. In the method, a small portion of PCB is sandwiched from one side at certain pressure by jaws. A couple of linear temperature profiles are applied to the jaws successively. Unknown values are tuned in the analysis model until the results of FEM analysis and experiment match. The values for the coefficient of thermal conductivity and specific heat capacity which the experiment and numerical analysis results match can be said to be the actual values. From this point on, the PCB whose thermal properties are determined can be analyzed numerically for any desired geometry and boundary condition.

Effect of magnetic field-dependent thermal conductivity on natural convection of magnetic nanofluid inside a square enclosure

2019 ◽  
Vol 29 (4) ◽  
pp. 1466-1489 ◽  
Author(s):  
Mohammadhossein Hajiyan ◽  
Shohel Mahmud ◽  
Mohammad Biglarbegian ◽  
Hussein A. Abdullah ◽  
A. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Hartmann Number ◽  
Magnetic Nanofluid ◽  
Content Type ◽  
Square Enclosure ◽  
Field Dependent

Purpose The purpose of this paper is to investigate the convective heat transfer of magnetic nanofluid (MNF) inside a square enclosure under uniform magnetic fields considering nonlinearity of magnetic field-dependent thermal conductivity. Design/methodology/approach The properties of the MNF (Fe3O4+kerosene) were described by polynomial functions of magnetic field-dependent thermal conductivity. The effect of the transverse magnetic field (0 < H < 105), Hartmann Number (0 < Ha < 60), Rayleigh number (10 <Ra <105) and the solid volume fraction (0 < φ < 4.7%) on the heat transfer performance inside the enclosed space was examined. Continuity, momentum and energy equations were solved using the finite element method. Findings The results show that the Nusselt number increases when the Rayleigh number increases. In contrast, the convective heat transfer rate decreases when the Hartmann number increases due to the strong magnetic field which suppresses the buoyancy force. Also, a significant improvement in the heat transfer rate is observed when the magnetic field is applied and φ = 4.7% (I = 11.90%, I = 16.73%, I = 10.07% and I = 12.70%). Research limitations/implications The present numerical study was carried out for a steady, laminar and two-dimensional flow inside the square enclosure. Also, properties of the MNF are assumed to be constant (except thermal conductivity) under magnetic field. Practical implications The results can be used in thermal storage and cooling of electronic devices such as lithium-ion batteries during charging and discharging processes. Originality/value The accuracy of results and heat transfer enhancement having magnetic field-field-dependent thermal conductivity are noticeable. The results can be used for different applications to improve the heat transfer rate and enhance the efficiency of a system.

Heat Exchange Between a Tube and Water-Saturated Soil

1986 ◽  
Vol 108 (4) ◽  
pp. 298-302 ◽  
Author(s):  
C. A. van der Star ◽  
G. A. M. van Meurs ◽  
C. J. Hoogendoorn
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Saturated Soil ◽  
Mutual Distance ◽  
Tube Material ◽  
Surrounding Water ◽  
Analytical Approximations ◽  
Water Saturated ◽  
Regional Groundwater

The heat transfer between a cylinder and the surrounding water-saturated soil is studied numerically. Parameters which influence this heat transfer are thermal properties of the soil, dimension and thermal conductivity of the tube material, and a regional groundwater flow. The results are compared to analytical approximations. When two tubes are present, their mutual distance is also such a parameter.

scholarly journals Thermal conductivity of silicon doped by phosphorus: ab initio study

2018 ◽  
Vol 35 (4) ◽  
pp. 717-724
Author(s):  
B. Andriyevsky ◽  
W. Janke ◽  
V.Yo. Stadnyk ◽  
M.O. Romanyuk
Keyword(s):  
Thermal Conductivity ◽  
Heat Conductivity ◽  
Phonon Scattering ◽  
Theoretical Calculations ◽  
Doped Semiconductors ◽  
Silicon Crystals ◽  
Coefficient Of Thermal Conductivity ◽  
Silicon Doped ◽  
Scattering Time ◽  
Phosphorus Doped

Abstract An original approach to the theoretical calculations of the heat conductivity of crystals based on the first principles molecular dynamics has been proposed. The proposed approach exploits the kinetic theory of phonon heat conductivity and permits calculating several material properties at certain temperature: specific heat, elastic constant, acoustic velocity, mean phonon scattering time and coefficient of thermal conductivity. The method has been applied to silicon and phosphorus doped silicon crystals and the obtained results have been found to be in satisfactory agreement with corresponding experimental data. The proposed computation technique may be applied to the calculations of heat conductivity of pure and doped semiconductors and isolators.

Numerical simulation of thermal properties at Cu/Al interfaces based on hybrid model

2015 ◽  
Vol 32 (3) ◽  
pp. 574-584
Author(s):  
Yunqing Tang ◽  
Liqiang Zhang ◽  
Haiying Yang ◽  
Juan Guo ◽  
Ningbo Liao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Bonding Temperature ◽  
Dissimilar Materials ◽  
Element Model ◽  
Potential Method ◽  
Interfacial Thermal Resistance ◽  
Interfacial Region ◽  
Fe Model ◽  
Content Type

Purpose – The purpose of this paper is to investigate thermal properties at Cu/Al interfaces. Design/methodology/approach – A hybrid (molecular dynamics-interface stress element-finite element model (MD-ISE-FE) model is constructed to describe thermal behaviors at Cu/Al interfaces. The heat transfer simulation is performed after the non-ideal Cu/Al interface is constructed by diffusion bonding. Findings – The simulation shows that the interfacial thermal resistance is decreasing with the increase of bonding temperature; while the interfacial region thickness and interfacial thermal conductivity are increasing with similar trends when the bonding temperature is increasing. It indicates that the higher bonding temperature can improve thermal properties of the interface structure. Originality/value – The MD-ISE-FE model proposed in this paper is computationally efficient for interfacial heat transfer problems, and could be used in investigations of other interfacial behaviors of dissimilar materials. All these are helpful for the understanding of thermal properties of wire bonding interface structures. It implies that the MD-ISE-FE multiscale modeling approach would be a potential method for design and analysis of interfacial characteristics in micro/nano assembly.

Examination of Microstructure of Cement Composite Material for Renovation of Horizontal Structures

2019 ◽  
Vol 808 ◽  
pp. 103-108
Author(s):  
Lenka Mészárosová ◽  
Vít Černý ◽  
Rostislav Drochytka ◽  
Winfried Malorny
Keyword(s):  
Thermal Conductivity ◽  
Composite Material ◽  
High Temperature ◽  
Surface Temperature ◽  
Cement Composite ◽  
Volume Weight ◽  
Coefficient Of Thermal Conductivity ◽  
New Material ◽  
Properties Of Materials ◽  
Low Volume

Development of new material is focused on modification of properties of materials with silicate binder so that these could be used for renovation of horizontal structures of high-temperature devices and at the same time contribute to reduction of heat transportation of constructions with higher surface temperature (in this case 200 and 500 °C). Main requirements for this material is low volume weight and low coefficient of thermal conductivity. This paper assesses influence of exposition to higher temperatures on microstructure.

Eulerian–Eulerian multi-phase RPI modeling of turbulent forced convective of boiling flow inside the tube with porous medium

2019 ◽  
Vol 30 (5) ◽  
pp. 2739-2757 ◽  
Author(s):  
Reza Azadbakhti ◽  
Farzad Pourfattah ◽  
Abolfazl Ahmadi ◽  
Omid Ali Akbari ◽  
Davood Toghraie
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Porous Medium ◽  
Flow Boiling ◽  
Rensselaer Polytechnic Institute ◽  
Content Type ◽  
Turbulent Flow Regime ◽  
High Reynolds ◽  
Multi Phase

Purpose The purpose of this study is simulation the flow boiling inside a tube in the turbulent flow regime for investigating the effect of using a porous medium in the boiling procedure. Design/methodology/approach To ensure the accuracy of the obtained numerical results, the presented results have been compared with the experimental results, and proper coincidence has been achieved. In this study, the phase change phenomenon of boiling has been modeled by using the Eulerian–Eulerian multi-phase Rensselaer Polytechnic Institute (RPI) wall boiling model. Findings The obtained results indicate using a porous medium in boiling process is very effective in a way that by using a porous medium inside the tub, the location of changing the liquid to the vapor and the creation of bubbles, changes. By increasing the thermal conductivity of porous medium, the onset of phase changing postpones, which causes the enhancement of heat transfer from the wall to the fluid. Generally, it can be said that using a porous medium in boiling flows, especially in flow with high Reynolds numbers, has a positive effect on heat transfer enhancement. Also, the obtained results revealed that by increasing Reynolds number, the created vapor phase along the tube decreases and by increasing Reynolds number, the Nusselt number enhances. Originality/value In present research, by using the computational fluid dynamics, the effect of using a porous medium in the forced boiling of water flow inside a tube has been investigated. The fluid boiling inside the tube has been simulated by using the multi-phase Eulerian RPI wall boiling model, and the effect of thermal conductivity of a porous medium and the Reynolds number on the flow properties, heat transfer and boiling procedure have been investigated.

Analysis of nanofluids as a means of thermal conductivity enhancement in heavy machineries

2014 ◽  
Vol 66 (2) ◽  
pp. 238-243 ◽  
Author(s):  
Ayush Jain ◽  
Imbesat Hassan Rizvi ◽  
Subrata Kumar Ghosh ◽  
P.S. Mukherjee
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Ethylene Glycol ◽  
Base Fluid ◽  
High Concentration ◽  
Content Type ◽  
Conductivity Enhancement ◽  
Heavy Machinery ◽  
Heat Transfer Fluids ◽  
Experimental Findings

Purpose – Nanofluids exhibit enhanced heat transfer characteristics and are expected to be the future heat transfer fluids particularly the lubricants and transmission fluids used in heavy machinery. For studying the heat transfer behaviour of the nanofluids, precise values of their thermal conductivity are required. For predicting the correct value of thermal conductivity of a nanofluid, mathematical models are necessary. In this paper, the effective thermal conductivity of various nanofluids has been reported by using both experimental and mathematical modelling. The paper aims to discuss these issues. Design/methodology/approach – Hamilton and Crosser equation was used for predicting the thermal conductivities of nanofluids, and the obtained values were compared with the experimental findings. Nanofluid studied in this paper are Al2O3 in base fluid water, Al2O3 in base fluid ethylene glycol, CuO in base fluid water, CuO in base fluid ethylene glycol, TiO2 in base fluid ethylene glycol. In addition, studies have been made on nanofluids with CuO and Al2O3 in base fluid SAE 30 particularly for heavy machinery applications. Findings – The study shows that increase in thermal conductivity of the nanofluid with particle concentration is in good agreement with that predicted by Hamilton and Crosser at typical lower concentrations. Research limitations/implications – It has been observed that deviation between experimental and theoretical results increases as the volume concentration of nanoparticles increases. Therefore, the mathematical model cannot be used for predicting thermal conductivity at high concentration values. Originality/value – Studies on nanoparticles with a standard mineral oil as base fluid have not been considered extensively as per the previous literatures available.

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