Thermal Characteristics of Damp Hydrophobic, Microfibrous Batt

1988 ◽  
Vol 110 (1) ◽  
pp. 19-22
Author(s):  
K. A. Steele
Keyword(s):  
Thermal Conductivity ◽  
Mathematical Model ◽  
Thermal Characteristics ◽  
Region Of Interest ◽  
Experimental Results ◽  
Preliminary Design ◽  
Insulating Material ◽  
Temperature Range ◽  
Higher Temperature ◽  
Thermal Conductivities

The thermal characteristics of damp, hydrophobic insulating material used primarily in underwater dry suit applications were investigated. Testing was performed in a Rapid-K Thermal Conductivity Instrument manufactured by Dynatech, Inc. A mathematical model of the process was proposed, and the results obtained using this model were compared to experimental results. The two agreed well except in the higher temperature range, where the model predicts higher thermal conductivities than those observed. However, for the region of interest agreement was good, and the model should be considered valid for the preliminary design of dry suits using hydrophobic batting as an insulator.

Effects of Nb doping on thermoelectric properties of Zn4Sb3 at high temperatures

2009 ◽  
Vol 24 (2) ◽  
pp. 430-435 ◽  
Author(s):  
D. Li ◽  
H.H. Hng ◽  
J. Ma ◽  
X.Y. Qin
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
High Temperatures ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermoelectric Performance ◽  
Temperature Range ◽  
A Value ◽  
Nb Doping ◽  
Thermal Conductivities

The thermoelectric properties of Nb-doped Zn4Sb3 compounds, (Zn1–xNbx)4Sb3 (x = 0, 0.005, and 0.01), were investigated at temperatures ranging from 300 to 685 K. The results showed that by substituting Zn with Nb, the thermal conductivities of all the Nb-doped compounds were lower than that of the pristine β-Zn4Sb3. Among the compounds studied, the lightly substituted (Zn0.995Nb0.005)4Sb3 compound exhibited the best thermoelectric performance due to the improvement in both its electrical resistivity and thermal conductivity. Its figure of merit, ZT, was greater than the undoped Zn4Sb3 compound for the temperature range investigated. In particular, the ZT of (Zn0.995Nb0.005)4Sb3 reached a value of 1.1 at 680 K, which was 69% greater than that of the undoped Zn4Sb3 obtained in this study.

Determination of Thermal Conductivity of Soils: A Need for Computing Heat Loss Through Buried Submarine Pipelines

1982 ◽  
Vol 22 (04) ◽  
pp. 558-562 ◽  
Author(s):  
P.C. Rawat ◽  
S.L. Agarwal
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Crude Oil ◽  
Rheological Properties ◽  
Heat Loss ◽  
Experimental Results ◽  
Dry Density ◽  
Empirical Relationships ◽  
Thermal Conductivities

Abstract An important parameter required for computing heat loss through buried submarine pipelines transporting crude oil is the thermal conductivity of soils. This paper describes an apparatus designed for determination of the thermal conductivity of soils at the desired moisture/ density condition in the laboratory under steady-state conditions. Experimental results on the three soils studied show that thermal conductivity increases as dry density increases at a constant moisture content and that it increases as water content increases at constant dry density. These results confirm the trends isolated earlier by Kersten. The experimental results are compared with the available empirical relationships. Kersten's relation is observed to predict the thermal conductivity of these soils reasonably. The predictions from Makowski and Mochlinski's relation (quoted by Szilas) are not good but improve if the sum of silt and clay fractions is treated as a clay fraction in the computation. Introduction Submarine pipelines are used extensively for transporting crude oil from offshore to other pipelines offshore or onshore. These pipelines usually are steel pipes covered with a coating of concrete. They often are buried some depth below the mudline. The rheological properties of different crude oils vary, and their viscosities increase with a decrease in temperature. Below some temperature, the liquid oil tends to gel. Therefore, for efficient transportation, the crude must be at a relatively high temperature so that it has a low viscosity. The temperature of the soil/water system surrounding a submarine pipeline is usually lower than that of oil. This temperature difference induces heat to flow from the oil to the environment, and the temperature of the oil decreases as it travels along the length of the pipeline. One must ensure that this temperature reduction does not exceed desirable limits dictated by the rheological properties of oil and by the imperatives of efficient economic properties of oil and by the imperatives of efficient economic transportation. Thus the analytical problem is to predict the temperature of crude in the pipeline some distance away from the input station. To do so, knowledge of the overall heat transfer coefficient for the pipeline is required, for which, in turn, it is necessary to know the thermal conductivities of the oil, the pipeline materials and its coating, and the soil. This paper presents thermal conductivities of soils determined in the laboratory under steady-state conditions and also presents a comparison of the test results of three soils with values determined from existing empirical relationships. Literature Review Heat moves spontaneously from higher to lower temperatures. In a completely dry porous body, transmission of heat can take place not only by conduction through the solid framework of the body and the air in the pores but also by convection and radiation between the walls of a pore and by macro- and microdistillation. In soils, however, it can be ascribed essentially to conduction, a molecular phenomenon that can be expressed in terms of experimentally determined coefficients of conductivity or resistivity, although these actually may include microdistillation and other mechanisms. SPEJ p. 558

Thermoelectric Properties of Bi2Te3-ySey Bulk Materials Synthesized by Melting-Grinding Process

2018 ◽  
Vol 773 ◽  
pp. 145-151
Author(s):  
Min Soo Park ◽  
Gook Hyun Ha ◽  
Hye Young Koo ◽  
Yong Ho Park
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Thermal Characteristics ◽  
Grinding Process ◽  
Alloy Scattering ◽  
Temperature Range ◽  
P Type ◽  
Optimal Effect

The Bi–Te thermoelectric system shows an excellent figure of merit (ZT) near room temperature. Research on increasing the ZT value for n‑type Bi–Te is imperative because the thermoelectric properties of this compound are inferior to those of the p-type material. For this purpose, n-type Bi2Te3-ySey powders with various amounts of Se dopant (0.3 ≤ y ≤ 0.6) were synthesized by a vacuum melting-grinding process to improve the physical properties. The ZT value of the sintered bodies was investigated in the temperature range of 298–423 K with regard to the electrical and thermal characteristics. As the Se content increased, the electrical conductivity decreased owing to a reduction in the carrier concentration, which improved the overall value of ZT. The thermal conductivity clearly decreased as the Se content increased in the temperature range of 298–373 K due to increased alloy scattering, as well as a reduction in the lattice thermal conductivity caused by crystal grain boundary scattering. At room temperature, Bi2Te2.7Se0.3 (y = 0.3) exhibited the highest ZT of 0.85. At increased temperatures, the ZT value was highest for Bi2Te2.55Se0.45 (y = 0.45), indicating that the optimal effect of the Se dopants varies depending on the temperature range.

Thermal Characteristics of Soluble Starch Synthase From Wheat Endosperm

1995 ◽  
Vol 22 (4) ◽  
pp. 703 ◽  
Author(s):  
CF Jenner ◽  
K Denyer ◽  
J Guerin
Keyword(s):  
Thermal Characteristics ◽  
Soluble Starch ◽  
Starch Synthase ◽  
Wheat Grain ◽  
Wheat Endosperm ◽  
Temperature Range ◽  
Higher Temperature ◽  
Temperature Responses

The aim of the work reported in this paper was to characterise the thermal responses of soluble starch synthase (SSS) extracted from the endosperm of the developing wheat grain. Using partially purified preparations of SSS, the reaction obeyed Michaelis-Menten kinetics with both substrates amylopectin and ADPglucose. Both the Vmax and the Km varied with temperature. Values for Vmax were higher at 45�C compared with 25�C. However, the Km values for both substrates were also higher at 45�C than at 25�C indicating that the affinity of the enzyme for its substrates was reduced at the higher temperature. Over the temperature range 15-45�C, the Km for arnylopectin was minimal at 20�C, and rose exponentially between 25 and 45�C. Kinetic analyses indicated that the reaction was sequential and that the substrates could bind to the enzyme in either order. At 25�C the binding of one substrate to the enzyme increased the affinity of the complex for the second substrate but at 45�C these effects were abolished. These thermal characteristics of SSS could explain certain important features of the temperature responses of starch deposition in the wheat grain in vivo.

Thermal Expansion and Isotopic Composition Effects on Lattice Thermal Conductivities of Crystalline Silicon

2006 ◽  
Author(s):  
Yunfei Chen ◽  
Guodong Wang ◽  
Deyu Li ◽  
Jennifer R. Lukes
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Md Simulation ◽  
Lattice Thermal Conductivity ◽  
Mass Difference ◽  
Dynamics Simulation ◽  
Temperature Range ◽  
Simulation Results ◽  
Callaway Model ◽  
Thermal Conductivities

Equilibrium molecular dynamics simulation is used to calculate lattice thermal conductivities of crystal silicon in the temperature range from 400K to 1600K. Simulation results confirmed that thermal expansion, which resulted in the increase of the lattice parameter, caused the decrease of the lattice thermal conductivity. The simulated results proved that thermal expansion imposed another type resistance on phonon transport in crystal materials. Isotopic and vacancy effects on lattice thermal conductivity are also investigated and compared with the prediction from the modified Debye Callaway model. It is demonstrated in the MD simulation results that the isotopic effect on lattice thermal conductivity is little in the temperature range from 400K to 1600K for isotopic concentration below 1%, which implies the isotopic scattering on phonon due to mass difference can be neglected over the room temperature. The remove of atoms from the crystal matrix caused mass difference and elastic strain between the void and the neighbor atoms, which resulted in vacancy scattering on phonons. Simulation results demonstrated this mechanism is stronger than that caused by isotopic scattering on phonons due to mass difference. A good agreement is obtained between the MD simulation results of silicon crystal with vacancy defects and the data predicted from the modified Debye Callaway model. This conclusion is helpful to demonstrate the validity of Klemens' Rayleigh model for impurity scattering on phonons.

THERMAL CONDUCTIVITY OF METALS AT HIGH TEMPERATURES: I. DESCRIPTION OF THE APPARATUS AND MEASUREMENTS ON IRON

1947 ◽  
Vol 25a (6) ◽  
pp. 357-374 ◽  
Author(s):  
L. D. Armstrong ◽  
T. M. Dauphinee
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
High Temperatures ◽  
Armco Iron ◽  
Absolute Error ◽  
Cylindrical Sample ◽  
Comprehensive Analysis ◽  
Temperature Curve ◽  
Temperature Range ◽  
Thermal Conductivities

An apparatus for measuring the thermal conductivity of metals in the temperature range 0° to 800 °C. is described. The method utilizes unidirectional heat flow in a cylindrical sample in a vacuum. The advantages of the method are outlined and a comprehensive analysis of possible errors in the measurements is included. Measurements on Armco iron indicate that results with an absolute error of less than 2% may be obtained. The results of measurements on a sample of Armco iron gave thermal conductivities of 0.1819 c.g.s units at 0 °C. and 0.0698 c.g.s. units at 800 °C. A change in slope of the thermal conductivity–temperature curve was found at a temperature of approximately 375 °C., and is tentatively attributed to the presence of 0.03% nickel impurity.

scholarly journals Predictive model of the dependence of the cost of insulation on thermal characteristics

2019 ◽  
Vol 140 ◽  
pp. 04018
Author(s):  
Olga Gamayunova ◽  
Anton Radaev ◽  
Mikhail Petrichenko ◽  
Raimond Bogdanivics
Keyword(s):  
Thermal Conductivity ◽  
Mathematical Model ◽  
Predictive Model ◽  
Building Materials ◽  
Thermal Characteristics ◽  
Average Density ◽  
Coefficient Of Determination ◽  
The Cost ◽  
Selection Of

In the market of building materials today there is a large selection of various thermal insulation materials, differing in cost, thermal conductivity and other characteristics. This article describes the predictive model of the cost of insulation from thermal characteristics, such as: thickness, thermal conductivity, (average) density, water absorption and combustibility group. The coefficient of determination was used to assess the quality of the obtained economic-mathematical model. The described predictive model can be effectively used to solve problems associated with determining the optimal characteristics of insulation by the criterion of minimizing cost.

Anisotropy of thermal conductance in near-ideal graphite

1965 ◽  
Vol 284 (1396) ◽  
pp. 17-31 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Basal Plane ◽  
Thermal Conduction ◽  
Theoretical Estimate ◽  
Thermal Conductance ◽  
Temperature Range ◽  
Neutron Damage ◽  
Plane Direction ◽  
Umklapp Scattering ◽  
Thermal Conductivities

Measurements of thermal conductivities of a number of pyrolytic graphites are reported in­cluding values for annealed, hot pressed graphite (IFPA 57). Thermal conductivities of IFPA 57 in both basal plane and c -axis directions approach the values for ideal graphite at higher tem­peratures. A theoretical estimate of the anisotropy of thermal conduction in ideal graphite in the temperature range where umklapp scattering predominates shows fair agreement with the present experimental value. Such defects as are normally present in well-oriented graphite produce comparatively little effect on the c -axis thermal conductivity and exposure to neutron damage has a much smaller effect in the direction of the c axis, than in the basal plane direction.

scholarly journals Mathematical Model for Analyzing Heat Transfer Characteristics of Ablative Thermal Insulating Material

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Junjie Gao ◽  
Haitao Han ◽  
Daiying Deng ◽  
Jijun Yu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mathematical Model ◽  
Size Distribution ◽  
Distribution Area ◽  
Heat Transfer Characteristics ◽  
Equivalent Thermal Conductivity ◽  
Insulating Material ◽  
Transfer Characteristics ◽  
Thermal Insulating

A mathematical model based on minimal thermal resistance and equal law of specific equivalent thermal conductivity is developed to discuss the heat transfer characteristics of ablative thermal insulating material from the mesoscopic scale. Based on the statistical results of mesoscopic parameters, the microstructure unit cell model was established to analyze the influence rule of mesoscopic parameterization which includes the size, distribution, and positional relation of microsphere and fiber. The results show that the equivalent thermal conductivity decreases with the density, size, distribution area, and distance of microsphere and the space distance and volume fraction of fiber decreasing. Besides, the equivalent thermal conductivity will become larger when more quality of heat transfers along the fiber direction. Exploring the relationship between the macroscopic heat transfer process and the microstructure is meaningful for exploring the heat transfer behavior of thermal insulating material and improvement of the processing technology.

The Thermal Conductivity of Several Fluoride Glasses

1985 ◽  
Vol 61 ◽  
Author(s):  
K. A. McCarthy ◽  
H. H. Sample ◽  
M. B. Koss
Keyword(s):  
Thermal Conductivity ◽  
Strong Correlation ◽  
Preliminary Analysis ◽  
Fluoride Glass ◽  
Plateau Region ◽  
Fluoride Glasses ◽  
Fluorozirconate Glasses ◽  
Temperature Range ◽  
Beryllium Fluoride ◽  
Thermal Conductivities

ABSTRACTThe thermal conductivities of beryllium fluoride glass and a fluoroberyllate glass have been measured in the 2–100K temperature range. These results are compared with earlier results on fluorozirconate glasses. The “plateau” region is well-defined for both materials. The plateau-center conductivity for BeF2 glass is the lowest yet recorded for any glass; it is some three times lower than the fluoroberyllate glass and four times lower than the fluorozirconates. A preliminary analysis of the data show a strong correlation between plateau-center conductivity and average cation mass of the material.

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