3ω slope comparative method for fluid and powder thermal conductivity measurements

2016 ◽  
Vol 30 (25) ◽  
pp. 1650322
Author(s):  
X. H. Zheng ◽  
L. Qiu ◽  
P. Yue ◽  
G. Wang ◽  
D. W. Tang
Keyword(s):  
Thermal Conductivity ◽  
Comparative Method ◽  
Powder Materials ◽  
Dimensional Model ◽  
Time Saving ◽  
Depth Measurement ◽  
Heat Penetration ◽  
Detector Parameter ◽  
The Relationship ◽  
Detector Characteristic

By analyzing the relationship among the heat penetration depth, measurement frequency and detector characteristic parameters, a simple and practical [Formula: see text] slope comparative method has been proposed. The corresponding measurement system for measuring the thermal properties of fluids and powder materials was established and verified using several specimens with known thermophysical parameters, such as alcohol, distilled water, and air. Compared to the two-dimensional model, the data processing of the method is relatively simple and quick. Due to the elimination of errors introduced by the detector parameter measurement, the measurement accuracy of the method is higher than the conventional one-dimensional model. By using an appropriate frequency range, the new method is time saving and convenient for measuring the thermal conductivity of fluids and powders with low thermal conductivity. Based on the analysis, the effective thermal conductivity of nano-SiO2 powder is accurately determined.

An Experimental Investigation on Thermal Conductivity and Viscosity of Graphene doped CNTs /TiO2 Nanofluid

2020 ◽  
Vol 17 (3) ◽  
Author(s):  
A.M. Zetty Akhtar ◽  
M.M. Rahman ◽  
K. Kadirgama ◽  
M.A. Maleque
Keyword(s):  
Thermal Conductivity ◽  
Zeta Potential ◽  
Base Fluid ◽  
Minimum Quantity Lubrication ◽  
Cutting Fluid ◽  
Cutting Zone ◽  
Observation Method ◽  
The Stability ◽  
The Relationship ◽  
Zeta Potential Analysis

This paper presents the findings of the stability, thermal conductivity and viscosity of CNTs (doped with 10 wt% graphene)- TiO2 hybrid nanofluids under various concentrations. While the usage of cutting fluid in machining operation is necessary for removing the heat generated at the cutting zone, the excessive use of it could lead to environmental and health issue to the operators. Therefore, the minimum quantity lubrication (MQL) to replace the conventional flooding was introduced. The MQL method minimises the usage of cutting fluid as a step to achieve a cleaner environment and sustainable machining. However, the low thermal conductivity of the base fluid in the MQL system caused the insufficient removal of heat generated in the cutting zone. Addition of nanoparticles to the base fluid was then introduced to enhance the performance of cutting fluids. The ethylene glycol used as the base fluid, titanium dioxide (TiO2) and carbon nanotubes (CNTs) nanoparticle mixed to produce nanofluids with concentrations of 0.02 to 0.1 wt.% with an interval of 0.02 wt%. The mixing ratio of TiO2: CNTs was 90:10 and ratio of SDBS (surfactant): CNTs was 10:1. The stability of nanofluid checked using observation method and zeta potential analysis. The thermal conductivity and viscosity of suspension were measured at a temperature range between 30˚C to 70˚C (with increment of 10˚C) to determine the relationship between concentration and temperature on nanofluid’s thermal physical properties. Based on the results obtained, zeta potential value for nanofluid range from -50 to -70 mV indicates a good stability of the suspension. Thermal conductivity of nanofluid increases as an increase of temperature and enhancement ratio is within the range of 1.51 to 4.53 compared to the base fluid. Meanwhile, the viscosity of nanofluid shows decrements with an increase of the temperature remarks significant advantage in pumping power. The developed nanofluid in this study found to be stable with enhanced thermal conductivity and decrease in viscosity, which at once make it possible to be use as nanolubricant in machining operation.

WRITER’S INDIVIDUALITY IN THE LITERARY INTERPRETATION OF SOCIAL AND MORAL PROBLEMS

2020 ◽  
Vol 6 (3) ◽  
pp. 51-56
Author(s):  
Bakhodir Kholikov ◽  
Keyword(s):  
Comparative Method ◽  
Literary Interpretation ◽  
Moral Problems ◽  
The Relationship ◽  
Mario Puzo

The article examines the question of writer’s individuality in the literary interpretation of social and moral problems etective novels on the examples of works "The Godfather" by Mario Puzo and "Shaytanat" by Tahir Malik. The article focuses on the study of the relationship between the reality of a work and reality of life in the context of the period. The comparative method was used in the process of understanding the content of these works, created in different periods

scholarly journals Can We Use Grip Strength to Predict Other Types of Hand Exertions? An Example of Manufacturing Industry Workers

2021 ◽  
Vol 18 (3) ◽  
pp. 856
Author(s):  
Victor Ei-Wen Lo ◽  
Yi-Chen Chiu ◽  
Hsin-Hung Tu
Keyword(s):  
Grip Strength ◽  
Manufacturing Industry ◽  
Prediction Models ◽  
Demographic Variable ◽  
Time Saving ◽  
Daily Lives ◽  
Working Environments ◽  
Central Taiwan ◽  
Study Participants ◽  
The Relationship

Background: There are different types of hand motions in people’s daily lives and working environments. However, testing duration increases as the types of hand motions increase to build a normative database. Long testing duration decreases the motivation of study participants. The purpose of this study is to propose models to predict pinch and press strength using grip strength. Methods: One hundred ninety-eight healthy volunteers were recruited from the manufacturing industries in Central Taiwan. The five types of hand motions were grip, lateral pinch, palmar pinch, thumb press, and ball of thumb press. Stepwise multiple linear regression was used to explore the relationship between force type, gender, height, weight, age, and muscle strength. Results: The prediction models developed according to the variable of the strength of the opposite hand are good for explaining variance (76.9–93.1%). Gender is the key demographic variable in the predicting models. Grip strength is not a good predictor of palmar pinch (adjusted-R2: 0.572–0.609), nor of thumb press and ball of thumb (adjusted-R2: 0.279–0.443). Conclusions: We recommend measuring the palmar pinch and ball of thumb strength and using them to predict the other two hand motions for convenience and time saving.

scholarly journals Enhancement of the Thermal Performance of the Paraffin-Based Microcapsules Intended for Textile Applications

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1120
Author(s):  
Virginija Skurkyte-Papieviene ◽  
Ausra Abraitiene ◽  
Audrone Sankauskaite ◽  
Vitalija Rubeziene ◽  
Julija Baltusnikaite-Guzaitiene
Keyword(s):  
Thermal Conductivity ◽  
Thermal Performance ◽  
Comparative Method ◽  
Multiwall Carbon Nanotubes ◽  
Acrylic Resin ◽  
Positive Influence ◽  
Outer Shell ◽  
Ir Camera ◽  
Spacer Fabric ◽  
Thermally Conductive

Phase changing materials (PCMs) microcapsules MPCM32D, consisting of a polymeric melamine-formaldehyde (MF) resin shell surrounding a paraffin core (melting point: 30–32 °C), have been modified by introducing thermally conductive additives on their outer shell surface. As additives, multiwall carbon nanotubes (MWCNTs) and poly (3,4-ethylenedioxyoxythiophene) poly (styrene sulphonate) (PEDOT: PSS) were used in different parts by weight (1 wt.%, 5 wt.%, and 10 wt.%). The main aim of this modification—to enhance the thermal performance of the microencapsulated PCMs intended for textile applications. The morphologic analysis of the newly formed coating of MWCNTs or PEDOT: PSS microcapsules shell was observed by SEM. The heat storage and release capacity were evaluated by changing microcapsules MPCM32D shell modification. In order to evaluate the influence of the modified MF outer shell on the thermal properties of paraffin PCM, a thermal conductivity coefficient (λ) of these unmodified and shell-modified microcapsules was also measured by the comparative method. Based on the identified optimal parameters of the thermal performance of the tested PCM microcapsules, a 3D warp-knitted spacer fabric from PET was treated with a composition containing 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS shell-modified microcapsules MPCM32D and acrylic resin binder. To assess the dynamic thermal behaviour of the treated fabric samples, an IR heating source and IR camera were used. The fabric with 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS in shell-modified paraffin microcapsules MPCM32D revealed much faster heating and significantly slower cooling compared to the fabric treated with the unmodified ones. The thermal conductivity of the investigated fabric samples with modified microcapsules MPCM32D has been improved in comparison to the fabric samples with unmodified ones. That confirms the positive influence of using thermally conductive enhancing additives for the heat transfer rate within the textile sample containing these modified paraffin PCM microcapsules.

scholarly journals Effect of microstructure on the properties of polystyrene microporous foaming material

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 103-110
Author(s):  
Anfu Guo ◽  
Hui Li ◽  
Jie Xu ◽  
Jianfeng Li ◽  
Fangyi Li
Keyword(s):  
Thermal Conductivity ◽  
Compression Modulus ◽  
Cell Diameter ◽  
Compressive Property ◽  
Strength Increase ◽  
Compression Performance ◽  
Negative Linear Correlation ◽  
Sample Density ◽  
Foaming Temperature ◽  
The Relationship

AbstractThe performance of Polystyrene microporous foaming (PS-MCF) materials is influenced by their microstructures. Therefore, it is essential for industrializing them to investigate the relationship between their microstructure and material properties. In this study, the relationship between the microstructure, compressive property, and thermal conductivity of the PS-MCF materials was studied systematically. The results show that the ideal foaming pressure of PS-MCF materials, obtaining compression performance, is around 20 MPa. In addition, the increase of temperature causes the decrease of sample density. It effects that the compression modulus and strength increase with the decrease of foaming temperature. Because the expansion rate and cell diameter of the PS-MCF materials reduce the thickness of cell wall, they are also negatively correlated with their mechanical properties. Moreover, there is a negative linear correlation between the thermal conductivity and cell rate, whereas the cell diameter is positively correlated with the thermal conductivity.

Polyimide-Silica Hybrid Aerogels with High Mechanical Strength for Thermal Insulation Applications

2011 ◽  
Vol 1306 ◽  
Author(s):  
Wenting Dong ◽  
Wendell Rhine ◽  
Shannon White
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Ambient Conditions ◽  
Separation Membranes ◽  
Low Dielectric ◽  
Aging Conditions ◽  
Hybrid Aerogels ◽  
Mechanical Strengths ◽  
The Relationship ◽  
Silica Hybrid

ABSTRACTHigh performance polyimides have been widely investigated as materials with excellent thermal, mechanical, and electronic properties due to their highly rigid structures. Aspen has developed an approach to prepare polyimide aerogels which have applications as low dielectric constant materials, separation membranes, catalyst supports and insulation materials. In this paper, we will discuss the preparation of polyimide-silica hybrid aerogel materials with good mechanical strengths and low thermal conductivities. The polyimide-silica hybrid aerogels were made by a two-step process and the materials were characterized to determine thermal conductivity and compressive strength. Results show that compressive moduli of the polyimide-silica hybrid aerogels increase dramatically with density (power law relationship). Thermal conductivity of the aerogels is dependent on the aging conditions and density, with the lowest value achieved so far being ~12 mW/m-K at ambient conditions. The relationship between aerogel density and surface area, thermal stability, porosity and morphology of the nanostructure of the polyimide-silica hybrid aerogels are also described in this paper.

Improvement of Thermal Conductivity of Electroplated Copper Thin-Film Interconnections by Controlling Their Micro Texture

2014 ◽  
Author(s):  
Pornvitoo Rittinon ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Grain Boundaries ◽  
Diffraction Method ◽  
Electron Back Scatter Diffraction ◽  
High Resistivity ◽  
Copper Thin Film ◽  
Electroplated Copper ◽  
The Relationship

Copper thin films are indispensable for the interconnections in the advanced electronic products, such as TSV (Trough Silicon Via), fine bumps, and thin-film interconnections in various devices and interposers. However, it has been reported that both electrical and mechanical properties of the films vary drastically comparing with those of conventional bulk copper. The main reason for the variation can be attributed to the fluctuation of the crystallinity of grain boundaries in the films. Porous or sparse grain boundaries show very high resistivity and brittle fracture characteristic in the films. Thus, the thermal conductivity of the electroplated copper thin films should be varied drastically depending on their micro texture based on the Wiedemann-Franz’s law. Since the copper interconnections are used not only for the electrical conduction but also for the thermal conduction, it is very important to quantitatively evaluate the crystallinity of the polycrystalline thin-film materials and clarify the relationship between the crystallinity and thermal properties of the films. The crystallinity of the interconnections were quantitatively evaluated using an electron back-scatter diffraction method. It was found that the porous grain boundaries which contain a significant amount of vacancies increase the local electrical resistance in the interconnections, and thus, cause the local high Joule heating. Such porous grain boundaries can be eliminated by control the crystallinity of the seed layer material on which the electroplated copper thin film is electroplated.

Orientation Specific Thermal Properties of Polyimide Film

2000 ◽  
Vol 123 (3) ◽  
pp. 273-277 ◽  
Author(s):  
Robert J. Samuels ◽  
Nancy E. Mathis
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Polyimide Film ◽  
New Materials ◽  
Polyimide Films ◽  
Nondestructive Technique ◽  
Theoretical Understanding ◽  
First Time ◽  
The Relationship ◽  
Transfer Mechanisms

The present study examines the relationship between thermal conductivity and planarity in polyimide films. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation of the polyimide film have been characterized by polarizing microscope techniques, while the thermal conductivity measurements were done using a new rapid nondestructive technique. This correlation represents the first time thermal conductivity has been measured by modified hot wire techniques and related to the internal structure of polyimide. This work contributes to a deeper theoretical understanding of thermal conductivity and heat transfer mechanisms as they relate to orientation. Thermal conductivity evaluation could provide a new tool in the arsenal of structural characterization techniques. This relationship between thermal conductivity and orientation is key for applications of directional heat dissipation in the passive layers of chip assemblies. Such a correlation has potential to speed the development cycles of new materials during formulation as well as assure properties during production.

scholarly journals Land subsidence and hydrodynamic compaction of sedimentary basins

1998 ◽  
Vol 2 (2/3) ◽  
pp. 159-171 ◽  
Author(s):  
H. Kooi ◽  
J. J. de Vries
Keyword(s):  
Response Time ◽  
Land Subsidence ◽  
Sedimentary Basins ◽  
Sediment Loading ◽  
Dimensional Model ◽  
One Dimensional ◽  
Model Equations ◽  
Sediment Layers ◽  
The Relationship

Abstract. A one-dimensional model is used to investigate the relationship between land subsidence and compaction of basin sediments in response to sediment loading. Analysis of the model equations and numerical experiments demonstrate quasi-linear systems behaviour and show that rates of land subsidence due to compaction: (i) can attain a significant fraction (>40%) of the long-term sedimentation rate; (ii) are hydrodynamically delayed with respect to sediment loading. The delay is controlled by a compaction response time τc that can reach values of 10-5-107 yr for thick shale sequences. Both the behaviour of single sediment layers and multiple-layer systems are analysed. Subsequently the model is applied to the coastal area of the Netherlands to illustrate that lateral variability in compaction-derived land subsidence in sedimentary basins largely reflects the spatial variability in both sediment loading and compaction response time. Typical rates of compaction-derived subsidence predicted by the model are of the order of 0.1 mm/yr but may reach values in excess of 1 mm/yr under favourable conditions.

scholarly journals THE RELATIONSHIP between COURSE MANAGEMENT and EXAMINATION ATTRITION RATES among UNDERGRADUATE MEDICAL STUDENTS at the UNIVERSITY OF ZAMBIA

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Harrison Daka ◽  
Sekelani S. Banda ◽  
Charles M. Namafe
Keyword(s):  
Medical Students ◽  
Academic Staff ◽  
Comparative Method ◽  
Group Discussion ◽  
Course Management ◽  
Undergraduate Medical Students ◽  
Attrition Rates ◽  
Training Programmes ◽  
The University ◽  
The Relationship

This study investigated the relationship between course management and examination attrition rates among undergraduate medical students at the University of Zambia, School of Medicine between the years 2008 to 2016. An explanatory sequential research design was used for data collection. Data were captured using an evaluation survey instrument, students’ Focus Group Discussion schedule and an interview schedule for key informants. Quantitative data from the first set were analysed using descriptive and inferential statistics while qualitative data from the second set were analysed using constant comparative method. The findings indicate that there was significant statistical difference in the course workloads in all programmes (p = 0.000, F = 4, 596, d f = 8.53). The course loads were heavy, had little time allocated to them. Course concepts were not taught in depth and led to students’ perceptions that the courses were difficult. As such, there is urgent need to revise or review course contents (i. e. curricular) of several programmes to be in accordance with the time allocated to them and that the Department of Medical Education and Development (DMED) should consider organizing specific pedagogical training programmes for existing and newly employed academic staff.

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