共查询到20条相似文献,搜索用时 15 毫秒
1.
低温下导热系数测定对生物器官的低温保存、低温外科医学及数值模拟计算至关重要.在分析探针法测量原理的基础上,用探针法对低温下猪主动脉的导热系数进行了测量研究.实验表明探针在用甘油和蒸馏水进行标定后,可以方便准确地测量-90~-35℃温区下猪主动脉的导热系数. 相似文献
2.
C. Baroncini P. Di Filippo G. Latini M. Pacetti 《International Journal of Thermophysics》1980,1(2):159-175
Eighteen correlations appearing in the literature for the prediction of thermal conductivity, , of liquids are critically analyzed, and their reliability is checked using coherent input data and selected experimental values. The best results are obtained using the Reid, Sherwood, and Prausnitz correlation with a mean deviation of about 8% between predicted and experimental values. An improved correlation is proposed starting from the Viswanath equation, chosen because of its simplicity and convenience. The values of thermal conductivity obtained by this new correlation agree with the experimental values within 1%. 相似文献
3.
The principle of corresponding states has been applied to the thermal-conductivity data for molten alkali halides which have been obtained by recent forced Rayleigh scattering measurements. The theory, which was developed by Harada et al. for the transport properties of uni-univalent molten salts, is based on the fluctuation-dissipation theorem with the pair interaction between ions composed of core repulsive and Coulombic potentials. Four characteristic parameters specific to each salt have been used to reduce the thermal conductivity and temperature. It has been found that the thermal conductivity of molten alkali halides is adequately correlated by the corresponding-states correlation (
* 1/T
*) within experimental accuracy. By employing the correlation, the thermal conductivity of molten alkali fluorides, which could not be measured by the forced Rayleigh scattering method, is predicted.Paper dedicated to Professor Joseph Kestin. 相似文献
4.
A discussion is presented regarding the significance of the spatial temperature gradient approximation normally used in thermal conductivity measurement. Examples are presented illustrating the magnitude of temperature differences allowed for conductivity integral (TCI) method of analysis is presented as an alternative method which totally eliminates the need to impose temperature difference restrictions on the measurement process, so long as other errors, such as radiative heat losses, do not become excessive. 相似文献
5.
6.
A computerized system utilizing the transient needle-probe technique has been developed for thermal conductivity measurements on solids and liquids. Thermal conductivities are determined to an accuracy of better than 5%. The instrument is unique in that it uses off the shelf components such as a personal computer and analog-to-digital conversion devices, together with software developed in our laboratory. The initial expense and time required to begin measurements are less than 20% of those for normal transient hot-wire measurements. Typical results are presented for liquid tertiary butyl alcohol, 1-methylnaphthalene, and glycerin.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A. 相似文献
7.
J. N. Sweet 《International Journal of Thermophysics》1986,7(4):743-754
New techniques have been developed for reducing thermal conductivity data from thermal comparative measurements. The first of these techniques is based on making a Taylor-series expansion of the stack centerline temperature profile. The result is an expression giving the ratio of sample to reference conductivities at any temperature as a function of measured quantities, the stack thermocouple readings and stack element thicknesses. The conventional formula presently used to reduce comparative conductivity data is shown to be a special result of the general analysis. A second technique involves the use of linear least-squares (LS) techniques to derive both the sample and the reference conductivities from the measured data. The LS technique provides the coefficients for a polynomial temperature expansion of the reference and sample conductivities directly. Use of the new techniques is illustrated in a reduction of some comparative data on the conductivities of Pyrex 7740 and Pyroceram 9606. It is shown that a highly self-consistent pair of conductivity functions can be derived for these two commonly used reference materials if the conductivity vs temperature relation for Pyrex is modified slightly from its recommended value. The Pyroceram conductivity results from the comparative measurements are in good agreement with a conductivity derived from pulse diffusivity and differential scanning calorimetry measurements and also in good agreement with the recommended Pyroceram conductivity function.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A. 相似文献
8.
An improved correlation for the thermal conductivity of HCFC123 (2,2-dichloro-1,1,1-trifluoroethane)
Arno Laesecke Richard A Perkins John B Howley 《International Journal of Refrigeration》1996,19(4):231-238
An updated survey of the existing thermal conductivity data for HCFC123 is presented. In addition, new wide-ranging thermal conductivity measurements, which have been carried out at NIST, are summarized. These results supplement the existing database and are used for an improved correlation of the thermal conductivity of HCFC123. The correlation covers the temperature range from 180 to 480 K with pressures up to 67 MPa or densities up to 1900 kg m−3. The correlation includes an empirical critical enhancement term of a form suitable for industrial use and represents the NIST dataset within ±2.22% at the 95% confidence level. 相似文献
9.
10.
N. A. Sokolov 《Measurement Techniques》2007,50(4):412-415
A procedure for the computer modeling of the measurement of thermal conductivity by the symmetrical steady-state method employing
a plane layer with a guard hotplate is proposed, which enables the effect of the thermal conductivity of the heater module
on the systematic error of the thermal apparatus being modeled to be taken into account.
__________
Translated from Izmeritel’naya Tekhnika, No. 4, pp. 44–46, April, 2007. 相似文献
11.
This paper presents two schemes for a theoretically based data assessment of the thermal conductivity of dilute polyatomic gases. The first employs the simplified Thijsse expression, combined with accurate experimental data obtained from a transient hot-wire apparatus, as reference. The second makes use of theoretical results for the temperature dependence of the ratio D
int/D. Both methods lead to mutually consistent results for linear molecules and to useful criteria for discriminating between experimental data sets. The paper also demonstrates the influence of data burdened with systematic errors upon the final results of different correlation schemes. 相似文献
12.
K. Hisano 《International Journal of Thermophysics》1997,18(2):535-545
Thermal radiation calorimetry was applied to measure the thermal conductivity of insulating solid specimens. We consider the
system in which a disk-shaped specimen and a flat heater are mounted in a vacuum chamber with the specimen heated on one face
by irradiation. A temperature difference between two faces was observed at elevated temperatures under steady-state conditions.
An apparatus was developed using a thin graphite sheet as the heater element. Disk-shaped Pyrex glass and Pyroceram specimens,
whose surfaces were blackened with colloidal graphite, were used in the measurements. Noncontact temperature measurement was
performed using pyrometers and a thermocouple set in the gap between the heater and the specimen. Deviations of the estimated
thermal conductivities from the recommended values were about 5% in the temperature range 250 to 800°C.
Paper presented at the Fourth Asian Thermophysical Properties Conference, September 5–8, 1995, Tokyo, Japan. 相似文献
13.
This paper presents thermal conductivity measurements of propane over the temperature range of 192–320 K, at pressures to 70 MPa, and densities to 15 mol · L–1, using a transient line-source instrument. The precision and reproducibility of the instrument are within ±0.5%. The measurements are estimated to be accurate to ±1.5%. A correlation of the present data, together with other available data in the range 110–580 K up to 70 MPa, including the anomalous critical region, is presented. This correlation of the over 800 data points is estimated to be accurate within ±7.5%.Nomenclature
a
n, bij, bn, cn
Parameters of regression model
-
C
Euler's constant (=1.781)
-
P
Pressure, MPa (kPa)
-
P
cr
Critical pressure, MPa
-
Q
1
Heat flux per unit length, W · m–1
-
t
time, s
-
T
Temperature, K
-
T
cr
Critical temperature, K
-
T
0
Equilibrium temperature, K
-
T
re
Reference temperature, K
-
T
r
Reduced temperature = T/T
cr
-
T
TP
Triple-point temperature, K
Greek symbols
Thermal diffusivity, m2 · s–1
-
T
i
Temperature corrections, K
-
T
Temperature difference, K
-
T
w
Temperature rise of wire between time t
1 and time t
2, K
-
T
*
Reduced temperature difference (T–T
cr)/Tcr
-
corr
Thermal conductivity value from correlation, W · m–1 · K–1
-
cr
Thermal conductivity anomaly, W · m–1 · K–1
-
e
Excess thermal conductivity, W · m–1 · K–1
-
*
Reduced density difference
-
Thermal conductivity, W–1 · m–1 · K–1, mW · m–1 · K–1
-
bg
Background thermal conductivity, W · m–1 · K–1
-
0
Zero-density thermal conductivity, W · m–1 · K–1
-
Density, mol · L–1
-
cr
Critical density, mol · L–1
-
re
Reference density, mol · L–1
-
r
Reduced density
Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
14.
R. K. Williams J. B. Bates R. S. Graves D. L. McElroy F. J. Weaver 《International Journal of Thermophysics》1988,9(4):587-598
The thermal conductivity of partially stabilized zirconia was measured over the temperature range 320–1273 K using the radial heat flow method. The data have an absolute uncertainty of about ±2% and repeat measurements showed no evidence of changes in the thermal conductivity at high temperatures. This also was true for the thermal diffusivity data, which were obtained in vacuum over the temperature range 300–1473 K. Both sets of thermal conductivity data pass through minima at high temperatures. Quantitative differences were observed in the temperatures and thermal conductivities of the two minima. The results were analyzed by assuming parallel conduction by phonons and photons, and the phonon component was identified by fitting lower-temperature data. Extrapolating this curve allowed identification of the photon contribution to the thermal conductivity at high temperatures. The photon contribution approached a T
3 function and was larger in the thermal conductivity specimens. The difference in the photon contributions correlates with changes in the optical properties of the samples produced during the high temperature measurments. 相似文献
15.
16.
晶体材料导热性质的经验方程与预测方法 总被引:1,自引:0,他引:1
依据现有相关的功能晶体材料导热系数实验数据,寻求了晶体材料导热系数与平均原子密度和平均原子量之间关联的经验方程,并对Ⅲ-Ⅴ族化合物半导体和碳化物晶体材料给出了经验方程中的常数,从而为这些晶体材料导热性质的预测提供了一种可靠的方法。 相似文献
17.
A new model based on the rough hard-sphere theory is proposed for the correlation and prediction of the thermal conductivity of molten salts. The model is capable of predicting the thermal conductivity of all the members of a family of molten salts characterized by a common anion if the behavior of any single member of the family of salts is known. Only the molar volumes of the molten salt and the solid salt at the melting temperature are required in the calculations. In addition, the model is easily extended to mixtures with a simple mixing rule. 相似文献
18.
热传导聚合物基复合材料的研究进展 总被引:5,自引:0,他引:5
本文主要介绍了聚合物基复合材料的导热机理 ,以及预测二相体系复合材料热导率的理论模型方程。同时介绍了聚合物基导热材料的 3种类型及其具体应用 ,并提出聚合物基导热材料现阶段值得开发的课题和研究方向 相似文献
19.
R. Mostert H. R. van den Berg P. S. van der Gulik 《International Journal of Thermophysics》1989,10(2):409-415
The thermal conductivity of ethane in the critical region has been measured isochorically at densities up to 1.76 times the critical density and at temperatures down to 0.13 K above the critical temperature. The measurements were performed with a thermal conductivity apparatus based on the parallelplate method. The experimental accuracy was 0.5 to 5%, depending on the distance to the critical point. The experimental results agree well with a recently developed crossover theory for the thermal diffusivity of fluids in the critical region.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
20.
Abstract A relatively simple technique for the prediction of the thermal conductivity of polar organic fluids over the temperature range from 0° to 100°C is presented. The proposed model is basically derived via the generalized property correlation model developed by Riazi and Daubert in 1980. The method requires, as input, only normal boiling point, specific gravities and dipole moments or acentric factors for each compound of interest. Predicted thermal conductivities are compared with 93 literature data for 12 polar liquids. Average deviation between prediction and experiment is approximately within 8–12%, depending on the type of third input parameter, as opposed to 17% for the much involved method of Robins and Kingrea previously recommended. 相似文献