Studies of thermal conductivity of liquids. Part I

Abstract

The thermal conductivity of liquids is an important physical property, the value of which is required in the solution of most heat transfer correlations. The accuracy of the various correlations predicting these heat transfer coelllcients cannot be better than the accuracy with which the thermal conductivity is known. Until recently, nevertheless, the available data were scanty and of doubtful accuracy. During recent years considerable effort has been expended in the experimental determination of the thermal conductivity of various liquids, but little progress has been made toward developing an apparatus that yields dependable results.This paper presents experimental results on fifty-three pure organic liquids obtained with a newly designed, extensively tested apparatus. The results are correlated on a semitheoretical basis from a modified statement of the theory of corresponding states. An alternative theoretical equation f o r predicting the thermal conductivity of liquids is given in Part 11. The two methods of correlation are mutually supporting. APPARATUSThe thermoconductimetric apparatus was described in detail in an earlier publication ( 5 ) , where the results of a number of tests were also presented. The design features were decided upon as a result of previous experimental and theoretical studies ( & 5 ) on the various features of previously used apparatus. The apparatus (Figure 1) is of the steady state type. I n it lthe liquid layer is enclosed between two, 6-in.-diam. horizontal parallel steel bars and heated downward t o eliminate convection currents. To establish isothermal surfaces, the top and bottom bars are heated and cooled respectively by large amounts of water drawn from and returned to constant-temperature baths. The water rate is great enough t o eliminate much temperature change after the water circulates through the apparatus. Heat flows in series through the liquid layer and a 4-in.-thick steel bar. To improve the accuracy of measuring the heat flow, eighteen thermocouples were embedded in the steel bars in four layers at different positions from the center of the bars, and the heat flow was measured by means of the thermal conductivity of steel and the dimensions of the bar. The thermal conductivity of the piece of steel used in the apparatus was determined in a separate, specially constructed apparatus ( 5 ) . Heat losses were minimized by enclosing the bars in a glass cylinder and providing thermal guarding. This feature also permitted visual observation of the liquid layer, the thickness of which can be varied and is measured by means of three micrometers. This makes it possible to study the presence and effects of heat transfer by radiation across the liquid layer. The steel bars were nickel and chrome plaited, the metal surfaces in contact with the liquid layer being highly polished. Method of Calculation.In this apparatus the thermal conductivity of the liquid may be calculated by two independent methods, a n extrapolation method and an over-all-resis- where R, = resistance to he...

Thermal conductivities of liquids: new determinations for seven liquids and appraisal of existing values

“…The results for toluene of 'A R ' quality are given in figure 7. There is again seen to be good agreement with the values of Riedel and with the subsequent deter minations of Schmidt & Leidenfrost (1954). The values due to Bridgman, Smith and Shiba are again high, the departures amounting to from 10 to 18%.…”

Models for viscosity, thermal conductivity, and surface tension of selected pure fluids as implemented in REFPROP v10.0

“…Figure 15 shows deviations between the data and the model as a function of temperature. The data of Sakiadis and Coates (Sakiadis & Coates, 1955) are shown only for comparison. They were not used in the fitting process as they were considered not as reliable as Watanabe (Watanabe, 2003).…”

“…Parameters for the critical enhancement are presented in Table 4. Sakiadis and Coates (Sakiadis & Coates, 1955) data are shown for comparison purposes only. All experimental data are at atmospheric pressure.…”

Корреляция Между Теплофизическими И Акустическими Свойствами В Нефтях

“…Затем этот подход использовал Бриджман [13], принявший l равной среднему расстоянию между молекулами. В работах [14][15][16][17] использовалось представление о " свободном объеме" и учитывались внутренние степени свободы. В работе Широкова [18] после исключения l из уравнений для вязкости и теплопроводности получалась формула, связывающая их друг с другом.…”