Thermal Conductivity Of Liquids Research Articles

Thermal Conductivity of Ionic Liquids at Atmospheric Pressure: Database, Analysis, and Prediction Using a Topological Index Method

Thermal conductivity is an important thermophysical property of ionic liquids (ILs). In this paper, a database for the thermal conductivity of ILs was established by collecting experimental data from literature covering the period from 2007 to 2013, including 359 data points, 45 ILs. The influences of temperature and the alkyl chain length of the cation on thermal conductivity were also discussed. A topological index method was proposed to estimate the thermal conductivity of ILs based on collected data which were divided into training (299 data points, 38 ILs) and testing (60 data points, 7 ILs) sets. The total average absolute deviation between the calculated and literature data was found to be 2.3%, with 2.1% for the training set and 2.9% for the testing set. The topological index method guarantees satisfactory precision with a simple form and can be easily expanded to new kinds of ILs.

Analysis and Interpretation of Results of Thermal Conductivity Obtained by the Hot Wire Method

The results of experimental research determining the coefficient of thermal conductivity λ of selected liquids have been presented in this article. During measurements, a “hot wire” method was used, which belongs to the most interesting method because of its simplicity, easiness of realization, and precision. Platinum Pt500 sensor was used during measurements, which along with the measuring system creates precise temperature measuring converter with voltage output. Temperature analog, novel converter was developed individually for the needs of this experiment, connected to the computer measuring system that consists of multifunctional output of 14-bit converter A/C type NI USB-6009 produced by National Instruments together with interactive software for registration and measurements of voltage signals. Measurements were registered with the help of computer measuring system, with sampling time every 0.1 s. In this study, three methods of interpretation measurement data are proposed. Furthermore, for the needs of experiment, a computer programwas written that enables fast calculation of values of thermal conductivity coefficients in different time intervals. The biggest challenge in “hot wire”method is to find the time range (tmin ÷tmax) to estimate the thermal conductivity. The study attempts to find the proper range for six liquids with known thermal conductivity. Finally, authors proposed a general relation to estimate thermal conductivity of liquids based on the known parameters: density and specific heat.

Thermal conductivity of simple liquids: Origin of temperature and packing fraction dependences

The origin of both weak temperature dependence and packing fraction dependence of T(1/4)η(3/2) in the thermal conductivity of the simple Lennard-Jones (LJ) liquid is explored. In order to discuss the relative contributions from attractive or repulsive part of the interaction potential separately, the thermal conductivity of a series of Weeks-Chandler-Anderson (WCA) fluids is calculated by molecular dynamics simulations. The results show that the repulsive part plays the main role in the heat conduction, while the attractive part has no direct effect on the thermal conductivity for a given packing fraction. By investigating WCA fluids with potentials of varying softness, we explain the difference observed between the LJ liquids such as argon and Coulombic liquids such as NaCl.

Thermal conductivity of simple liquids: Temperature and packing-fraction dependence

The thermal conductivity of rare gases in liquid and dense fluid states has been evaluated using molecular dynamics simulation with the Lennard-Jones (LJ) potentials and the Green-Kubo (GK) formula. All the calculated thermal conductivities are in very good agreement with experimental results for a wide range of temperature and density. Special attention was paid to temperature and packing-fraction dependence which is nontrivial from dimensional analysis on the LJ potentials and the GK formula. First, the temperature dependence of T(1/4) was determined from the calculations at constant densities. Secondly, in order to obtain the dependence on packing fraction from that on number density separately, a scaling method of particle and/or cell size was introduced. The number density dependence of (N/V)(2/3) which is expected from the dimensional analysis of the GK formulas was confirmed and the packing-fraction dependence of η(3/2) was determined by using the scaling method. It turned out that the summarized functional form of m(-1/2)(N/V)(2/3)η(3/2)T(1/4) can well express both the calculated and experimental thermal conductivities for Ar, Kr, and Xe, where m is the atomic mass. The scaling method has also been applied to molten NaCl and KCl so that it has been found that the thermal conductivity has the packing-fraction dependence of η(2/3) which is much weaker than that of the simple LJ liquids.

長鎖ポリマー液体の熱伝導率：分子間及び分子内エネルギー伝搬の寄与についての分子動力学的研究

長鎖ポリマー液体の熱伝導率：分子間及び分子内エネルギー伝搬の寄与についての分子動力学的研究

点接触式熱物性測定法を利用した軟質材料及び液体の熱伝導率測定手法

本報では，点接触式熱物性測定法を軟質材料及び液体へ適用する場合の課題を提起し，この課題に対してポリイミド薄膜を用いた新しい測定手法を提案した．また，ポリイミド薄膜が測定に与える影響を検証するために数値計算を行い，その影響を明らかにした．さらに，水や寒天などの熱伝導率測定を行った結果，再現性は改善されたものの，ポリイミド薄膜の影響によって算出される見かけの熱伝導率と文献値に差異が生じた．しかしながら，各試料の測定結果の間に相関があることから修正式を考慮することで，正確な熱伝導率を算出できる可能性を示した．

Thermophysical properties of the Al83Co10Ce7 glass-forming alloy in crystalline and liquid states

In the temperature range of T=300–1900K, covering the crystalline and liquid states, the electroconductivity, thermal diffusivity, thermal conductivity, density and magnetic susceptibility of Al83Co10Ce7 glass-forming alloy were studied. It is established that the values of electrical and thermal conductivity of the system investigated are relatively low (in comparison with pure aluminum). Analyzing temperature dependence of Lorentz function obtained, we found that the lattice contribution in total thermal conductivity is essential. In liquid state above T>1700K, the anomalous changes in electroresistivity and magnetic susceptibility of the alloy were revealed. These high-temperature anomalies are accompanied by neither detectable thermal effects nor significant changes of alloy density. It was found that the density of the alloy investigated is greater for the liquid state than for the solid one. The experimental results obtained are discussed in the frames of conjecture about existence of chemically interacting Al2REM associates in the melt.

A group contribution method for determination of thermal conductivity of liquid chemicals at atmospheric pressure

In this communication, a group contribution method (GC) for the representation/prediction of liquid thermal conductivity of pure chemical compounds, most of which are organic in nature, is presented. Nearly 19,000 liquid thermal conductivity data at different temperatures compiled for 1635 chemical compounds were extracted from the DIPPR 801 database and used to develop the proposed model, as well as to validate and optimize its parameters and evaluate its predictive capability. The parameters of the model comprise the occurrences/existence of 49 chemical substructures plus temperature. Nearly 80% of the data set (15,450 data points) is used to develop the model parameters, 10% of the data set (1931 data points) was employed to validate and optimize the model parameters, and the remaining data (1931 data points) were implemented to assess its predictive capability. The average absolute relative deviation of the model results with respect to the DIPPR 801 data is less than 7.1%. In terms of its simplicity and wide range of applicability, the model shows reasonable accuracy.

Development of a quantitative structure–liquid thermal conductivity relationship for pure chemical compounds

In this study, a quantitative structure-liquid thermal conductivity relationship was developed for pure mostly organic chemical compounds. An extensive data set including more than 19,000 evaluated liquid thermal conductivity data for 1635 pure mostly organic chemical compounds at various temperatures and at atmospheric pressure below the normal boiling point and at saturated pressure above the normal boiling point temperature was provided from DIPPR 801 database to develop, validate and assess the predictive capabilities of the obtained correlation. Parameters of the model comprise 20 molecular descriptors including temperature. The obtained model shows a good agreement with DIPPR 801 data. The model shows the same values of the average absolute relative deviation and root mean square error of 7.4% and 0.01 for the training set (80% of the data), the validation set (10% of the data), and the test set (10% of the data). In terms of wide range of applicability, the model shows reasonable accuracy.

Effects of Experimental Method on Aggregation State and Thermal Conductivity of Carbon Nanotube-Based Fluids

The thermal conductivity of liquids with carbon nanotubes (CNTs) is higher than that of liquids with spherical nanoparticles which results from low-resistance heat flow paths formed by CNT–CNT contact. Since CNTs easily precipitate or cluster in base liquids, path formation depends on the dispersion state of CNTs. A model of the thermal-conductivity enhancement of liquids with CNTs is presented by incorporating the aggregate state where such paths are formed. This model concludes that the anomalously wide range of enhancement values that have been observed recently is attributed to aggregate concentration. CNT clustering and sedimentation in base liquids are the causes of the decreased thermal-conductivity enhancement of such liquids due to the increase of the volume fraction of CNTs in aggregates. Predictions based on our model also show that experimental methods of obtaining liquids with uniformly dispersed CNTs can change the CNT geometry and aggregate concentration related to the thermal-conductivity enhancement. Surfactant addition, CNT surface treatment with acid, and sonication have characteristic effects on the CNT state and thermal conduction. The model from this study can prove helpful in explaining the magnitude of such effects quantitatively.

Measurement of Thermal Conductivity of Liquid Based on Transient Double-Hot Wire Technique

A new experimental apparatus has been developed for measuring the thermal conductivity of liquid by the two transient hot-wire method, which is based on the theory of one-dimensional unsteady heat conduction in infinite medium. The glass tubes, the heating line source and temperature measurement devices are designed in this experiment. As the temperature controller, low-temperature bath provides a constant water bath environment and current calibrator is the power source. Wheatstone bridge is used to test the relation between the temperature changes and resistance. Data acquisition and control unit is data acquisition devices of the Wheatstone bridge. As the temperature coefficient of platinum wire resistance is calibrated. It can be used to measure 32 groups of data from 10°C to 40°C at the every 10°C according to the experimental steps.

Estimation Method for Thermal Conductivity of Soft Materials and Liquids by Inverse Analysis

Estimation Method for Thermal Conductivity of Soft Materials and Liquids by Inverse Analysis

R1234ze(E)+R32 および R1234yf+R32 混合冷媒の飽和液の熱伝導率測定

R1234ze(E)+R32 および R1234yf+R32 混合冷媒の飽和液の熱伝導率測定

Measurement of Thermal Conductivity of Liquids at High Temperature

The goal purchased in this paper is to implement a pulse method to measure the thermal conductivity of liquid silica glass above 1200°C until 1600°C. A heat flux stimulation controlled in energy and in time is generated on the front face of an experimental cell. The temperature rise is measured on the rear face of this cell face by using a fast cooled infrared camera. The choice of the measurement cell geometry is fundamental to be able to estimate at the same time the thermal diffusivity and the specific heat of the liquid by an inverse technique. The parameters estimation problem takes into account the optimization of the cell wall thickness. The theoretical model used for the inversion takes into account the coupled heat transfer modes (conduction, convection and radiation) that can occur during the experiment, particularly the thermal conductive short-cut through metallic lateral walls of the cell and radiative transfer within the semi-transparent and participating medium. First measurements are performed on a cell filled with water at ambient temperature in order to validate the parameters estimation procedure.

Development of a general model for determination of thermal conductivity of liquid chemical compounds at atmospheric pressure

In this communication, a general model for representation/presentation of the liquid thermal conductivity of chemical compounds (mostly organic) at 1 atm pressure for temperatures below normal boiling point and at saturation pressure for temperatures above the normal boiling point is developed using the Gene Expression Programming algorithm. Approximately 19,000 liquid thermal conductivity data at different temperatures related to 1636 chemical compounds collected from the DIPPR 801 database are used to obtain the model as well as to assess its predictive capability. The parameters of the model comprise temperature, acentric factor, critical pressure, normal boiling temperature, and molecular weight. Nearly 80% of the data set (15,221 data) is randomly assigned to develop the model equation, 10% of the data set (1902 data) is used to validate the model, and the remaining data (1902 data) were implemented to evaluate its predictive power. The average absolute relative deviation of the model results from the DIPPR 801 data is less than 9%. In terms of simplicity and wide range of applicability, this empirical model shows acceptable accuracy. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1702–1708, 2013

Determination of thermal conductivity of liquids and polymers from batch mixer data

The paper proposes a new technique allowing the determination of thermal conductivity of liquids and polymer melts with unknown rheological behavior from batch mixer data; the mixing elements can have simple or complex geometries. The simple mixer is represented by an equivalent simple Couette with a cup and a bob having an effective hydrodynamic (or thermal) radius, and the true batch mixer is represented by two adjacent concentric cylinder viscometer. Using the universal internal effective radius, the thermal conductivity for four polymers was estimated from the batch mixer temperature–rotor speed and torque data. A good agreement was found with the values measured by transient line source method and those of the literature. Melt activation energy was calculated from torque–temperature batch mixer data, and the obtained values were found to be consistent with the values extracted from low-amplitude oscillatory shear experiments as well as with the available published data.

Detailed physical properties prediction of pure methyl esters for biodiesel combustion modeling

In order to accurately simulate the fuel spray, atomization, combustion and emission formation processes of a diesel engine fueled with biodiesel, adequate knowledge of biodiesel’s physical properties is desired. The objective of this work is to do a detailed physical properties prediction for the five major methyl esters of biodiesel for combustion modeling. The physical properties considered in this study are: normal boiling point, critical properties, vapor pressure, and latent heat of vaporization, liquid density, liquid viscosity, liquid thermal conductivity, gas diffusion coefficients and surface tension. For each physical property, the best prediction model has been identified, and very good agreements have been obtained between the predicted results and the published data where available. The calculated results can be used as key references for biodiesel combustion modeling.

Development of Thermophysical and Transport Properties for the CFD Simulations of In-Cylinder Biodiesel Spray Combustion

This paper reports the development, validation, and application of the thermophysical and transport properties of coconut, palm, and soy methyl esters for fuel spray and combustion modeling under light-duty diesel engine conditions. The developed fuel library is implemented in an open-source CFD code. The fuel properties are validated for both constant volume combustion chamber and compression ignition (CI) engine operation at a wide range of conditions. Sensitivity analysis on the effects of individual fuel properties is also investigated under both conditions. The properties of interest for the study are density, vapor pressure, heat of vaporization, liquid heat capacity, vapor heat capacity, second-virial coefficient, liquid dynamic viscosity, vapor dynamic viscosity, liquid thermal conductivity, vapor thermal conductivity, surface tension, and vapor diffusivity. From these twelve physical and transport properties, only five have significant effects on fuel spray structure, combustion, and emission cha...

A hot-wire method based thermal conductivity measurement apparatus for teaching purposes

The implementation of an automated system based on the hot-wire technique is described for the measurement of the thermal conductivity of liquids using equipment easily available in modern physics laboratories at high schools and universities (basically a precision current source and a voltage meter, a data acquisition card, a personal computer and a high purity platinum wire). The wire, which is immersed in the investigated sample, is heated by passing a constant electrical current through it, and its temperature evolution, ΔT, is measured as a function of time, t, for several values of the current. A straightforward methodology is then used for data processing in order to obtain the liquid thermal conductivity. The start point is the well known linear relationship between ΔT and ln(t) predicted for long heating times by a model based on a solution of the heat conduction equation for an infinite lineal heat source embedded in an infinite medium into which heat is conducted without convective and radiative heat losses. A criterion is used to verify that the selected linear region is the one that matches the conditions imposed by the theoretical model. As a consequence the method involves least-squares fits in linear, semi-logarithmic (semi-log) and log–log graphs, so that it becomes attractive not only to teach about heat transfer and thermal properties measurement techniques, but also as a good exercise for students of undergraduate courses of physics and engineering learning about these kinds of mathematical functional relationships between variables. The functionality of the experiment was demonstrated by measuring the thermal conductivity in samples of liquids with well known thermal properties.

Lattice dynamics analysis of the thermal properties of liquid iron

Abstract In this paper, the embedded atom method potential and Johnson potential are applied to calculate the thermal properties of liquid iron with an emphasis on a wide rage of temperatures and pressures. The results show that the liquid iron self-diffusion coefficient increases with increasing temperature and decreases with increasing pressure. The calculated self-diffusion coefficient is in good agreement with Protopapas' hard-sphere model at atmospheric pressure. According to the simulation results, we can get the Arrhenius equation between diffusion coefficient, temperature and activation energy. Increasing pressure enlarges the liquid iron activation energy and reduces the movement of atoms in liquid iron. Liquid iron thermal conductivity is computed using non-equilibrium molecular dynamics simulation and the simulation results are consistent with Pottlacher's experimental results with acceptable uncertainty in the 1535–2700 K temperature range.