URETHANE RIGID FOAMS: A REVIEW OF THE FACTORS AFFECTING THE ATTAINMENT AND RETENTION OF OPTIMUM THERMAL CONDUCTIVITY AND THEIR SIGNIFICANCE IN SERVICE APPLICATIONS

Heat Transfer ◽  
1971 ◽  
pp. 261-269
Author(s):  
G.W. BALL ◽  
R. HURD ◽  
M.G. WALKER
Keyword(s):  
Thermal Conductivity ◽  
Factors Affecting ◽  
Rigid Foams

Enhanced Thermal Conductivity for Graphene Nanoplatelets/Epoxy Resin Composites

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Dahai Zhu ◽  
Yu Qi ◽  
Wei Yu ◽  
Lifei Chen ◽  
Mingzhu Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Epoxy Resin ◽  
Mass Fraction ◽  
Great Influence ◽  
Graphene Nanoplatelets ◽  
Resin Matrix ◽  
Heat Conducting ◽  
Factors Affecting ◽  
Molding Method ◽  
Ep Matrix

Graphene nanoplatelets (GNPs) have excellent thermal conductivity. It can significantly improve the heat-conducting property of epoxy resin (EP) matrix. In this paper, the GNPs/EP composites were successfully prepared by using ultrasonication and the cast molding method. The prepared GNPs/EP composites were systematically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal conductivity analyzer. Some factors affecting the thermal transfer performance of the composites were discussed. The defoamation has great influence on the thermal conductivity of composite. There is a nearly linear relationship between the mass fraction and the thermal conductivity of composite when the mass fraction of GNPs is below 4.3%. The results show that when the mass fraction of GNPs is 4.3% with crushing time of 2 s, the thermal conductivity of GNPs/EP composite is up to 0.99 W/m K. The thermal conductivity is increased by 9.0% compared with that without pulverization treatment (0.91 W/m K). When it is ground three times, the thermal conductivity of composite reaches the maximum (1.06 W/m K) and it is increased by 307.7% compared with that of epoxy resin matrix.

A review of factors affecting minimum temperature reached on clear, windless nights.

1991 ◽  
Vol 42 (1) ◽  
pp. 191 ◽  
Author(s):  
WK Gardner ◽  
GK McDonald ◽  
SE Ellis ◽  
M Platt ◽  
RG Flood
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Water Content ◽  
Temperature Profiles ◽  
Surface Emissivity ◽  
Factors Affecting ◽  
Surface Temperatures ◽  
Net Flux ◽  
Soil Heat Capacity ◽  
Initial Starting

A mathematical model of heat flux in which net flux was assumed to be proportional to the surface temperature was used to examine the effects of important environmental variables on minimum surface temperatures reached during cloudless nights. Variables considered were altitude, atmospheric water content, surface emissivity, soil heat capacity and conductivity, length of night, and initial starting temperature. Final temperatures reached were especially sensitive to changes in soil thermal conductivity and heat capacity. Both these parameters are affected by moisture content (particularly when low), making this the single most important factor affecting the severity of frost. Lower initial starting temperatures and longer nights increase the severity of frosting, as does any decrease in the depth of the atmosphere (as happens with changes in altitude) or reductions in the water content of the atmosphere. Emissivity of the radiating surface is relatively unimportant. Temperature profiles in the soil were similar, but extended to greater depths as heat capacitance declined, whereas lower thermal conductivity resulted in cooler surface temperatures while the decline in temperature did not extend as deep. The model was shown to be an improvement on one in which net flux was assumed to remain constant, and allows for a more instructive sensitivity analysis.

scholarly journals Investigating and Modeling the Factors Affecting Thermal Optimization and Dynamic Viscosity of Water Hybrid Nanofluid/Carbon Nanotubes via MOPSO using ANN

2020 ◽  
Vol 2 (3) ◽  
pp. 108-114
Author(s):  
Amin Moslemi Petrudi ◽  
Ionut Cristian Scurtu
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Volume Fraction ◽  
Optimization Process ◽  
Hybrid Nanofluid ◽  
Engineering Systems ◽  
Factors Affecting ◽  
Multi Objective ◽  
Ann Modeling ◽  
Artificial Neural Network Ann

Optimization is to find the best answer among existing situations. Optimization is used in the design and maintenance of many engineering systems to minimize costs or maximize profits. Due to the widespread use of optimization in engineering, this topic has grown a lot. In this paper, the optimization of multi-objective of Water Hybrid Nanofluid/Carbon Nanotubes is investigated. Multi-Objective Particle Swarm Optimization (MOPSO) algorithm has been used in order to maximize thermal conductivity and minimum viscosity by changing the temperature (300 to 340 ºk) and the volume fraction (0.01 to 0.4%) of nanofluid. Artificial Neural Network (ANN) modeling of experimental data has been used to obtain the values. Parto fronts, the optimal points and different values are 20 members and 15 iterations, and in order to compare the results optimization process on the first, fifth, tenth fronts, a relation has been proposed to predict the viscosity and Parto fronts in the optimization process. The aim of the study was to optimize nanofluid to reduce viscosity and increase thermal conductivity.

Analysis of heat transfer characteristics in textiles and factors affecting thermal properties by modeling

2019 ◽  
Vol 89 (21-22) ◽  
pp. 4681-4690 ◽  
Author(s):  
Hua Shen ◽  
Kaifang Xie ◽  
Haoxuan Shi ◽  
Xiaofei Yan ◽  
Lexi Tu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Mass Density ◽  
Test Plate ◽  
Heterogeneous Model ◽  
Factors Affecting ◽  
Heat Leakage ◽  
Experiment And Simulation ◽  
The One ◽  
High Consistency

The heat transmission through a fabric during the measurement of thermal resistance was simulated by a novel heterogeneous model that was constructed according to the structure of ThermolabII Tester KES-F7. In this model, the heat transmissions along the longitudinal and transverse directions of yarn were treated independently. The material constants of fabrics, such as mass density, specific heat, thermal conductivity and thickness, were used as parameters for simulation in this fabric model. The validity of this model was then confirmed by the high consistency between the heat flux obtained from experiment and simulation, with the average difference ratio lower than 5%. The simulation results suggested that the guard area could effectively reduce the horizontal heat leakage from the test plate when the experimental fabric was thin. Only less than 8% of heat leaked in the one-layer case, while the leakage was significantly aggravated when more layers of fabric were stacked, resulting in the considerably lower thermal insulation achieved in both experiment and simulation compared with that in real fabrics. The temperature distribution in the model also implied that the longitudinal and transverse thermal conductivity of yarn exerted great effect on the heat leakage during the measurement. Moreover, for multilayers consisting of different fabrics, the laying sequence could obviously influence the heat leakage and, consequently, change the obtained thermal resistance.

Fabrication and Measurement of Flexible Polymer Aerogel and Factors Affecting its Thermal Conductivity

2021 ◽  
Vol 324 ◽  
pp. 133-138
Author(s):  
Jia Zhen Wang ◽  
Jing Du ◽  
Yun Bo Wang
Keyword(s):  
Thermal Conductivity ◽  
Sol Gel ◽  
Optimal Solution ◽  
Factors Affecting ◽  
Flexible Polymer ◽  
Different Types ◽  
Wire Method ◽  
High Production ◽  
Gel Technique ◽  
High Production Cost

Silica aerogels are the most widely studied type of aerogel. However, its application still suffers from low mechanical strength and high production cost. The paper studies the use of recyclable PVC as the backbone material of the aerogel and introduces an economically friendly fabrication process of flexible PVC aerogel using sol-gel technique and ambient drying instead of the CO2 critical drying. Three different types of PVC powder with the molecule weight of 43000, 48000, and 80000 respectively are chosen and dissolved in DMF in five different concentrations-0.2, 0.4, 0.6, 0.8, and 1.0 g (mL)-1. The lowest thermal conductivity of the aerogel is measured using hot-wire method as 0.0323W(m*K)-1, which is made of PVC with molecule weight of 80000 in a concentration of 0.4g (mL)-1. The analysis based on SEM pictures shows that PVC type and concentration would greatly influence aerogel’s structure thus affecting its thermal conductivity. The optimal solution for producing low thermal conductivity aerogel is to use PVC powder with low molecule weight with a concentration between 0.2 and 0.6 g (mL)-1.

The Synthesis and Application of a Novel Class of Polyols for Preparation of Polyurethane

2013 ◽  
Vol 357-360 ◽  
pp. 1441-1445
Author(s):  
Xiao Lin Li ◽  
Zheng Fang ◽  
Dong Ji ◽  
Zhi Dong Wan ◽  
Kai Guo
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Polyurethane Foams ◽  
Low Density ◽  
Cell Content ◽  
Low Thermal Conductivity ◽  
High Compressive Strength ◽  
Rigid Polyurethane Foams ◽  
Closed Cell ◽  
Rigid Foams

The synthesis of a novel class of diamine-based polyols derivatives and the potentials and the limitations of these polyols were reported. This class of diamine-based polyols with high hydroxyl values and no acid values can be used in rigid polyurethane foams. The prepared rigid foams show the properties of low density, high closed cell content, low thermal conductivity, and high compressive strength.

A Review of the Factors Affecting the Thermophysical Properties of Silicate Slags

2012 ◽  
Vol 31 (4-5) ◽  
pp. 301-321 ◽  
Author(s):  
KC Mills ◽  
L Yuan ◽  
Z Li ◽  
GH Zhang ◽  
KC Chou
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Liquidus Temperature ◽  
List Type ◽  
Silicate Network ◽  
Individual Property ◽  
Factors Affecting ◽  
Property Data ◽  
Specific Temperature ◽  
Increasing Temperature

AbstractThis paper is dedicated to the memory of the of Prof. Masanori Iwase and his life and work. The factors which affect the thermo-physical properties of silicate and aluminno-silicate slags are reviewed. These include (i) the polymerisation of the silicate network (ii) various cation effects and (iii) temperature. Of these, the degree of polymerisation of the silicate network (expressed here through the parameter Q (= 4-NBO/T)) is the most important and the viscosity (η), electrical resistivity and thermal conductivity all increase as Q increases. Various ways in which different cations affect the properties are considered for each individual property viz. the -M-O bond strength affects (i) liquidus temperature (ii) activity coefficient of SiO2 and (iii) thermal expansion coefficient and whereas both the size and number of available cations affect the electrical conductivity and resistivity.The following observations were made: There is less scatter in property data for liquid slags at a specific temperature than that for the liquidus temperature.The relation between Arrhenius parameters, lnA and B for viscosity and electrical resistivity is non-linear.The magnitude of the thermal conductivity (k) in solid slags is related to the rigidity of silicate network and the rapid decrease in k with increasing temperature occurs at a temperature where the viscosity reaches η = 106 dPas.The introduction of Al2O3 into the silicate chain results in significant changes to the propertiesThe ways in which the various properties can be calculated from chemical composition are outlined.

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