| Heat transfer is one of the most fundamental issues in the field of chemical production,and thermal conductivity is an important physical parameter to characterize the heat conduction of a substance,which provides an important reference for finding a suitable heat exchange medium and is widely used in theoretical research and engineering design.Organics with high thermal conductivity play a key role in manufacturing applications for a wide range of applications,including solar energy collection,automotive control units and microelectronic devices.Among them,aldehydes,ketones and alcohols are the three more common types of organics,and are a variety of important chemical products and intermediates,widely used as industrial raw materials,pharmaceuticals,and daily necessities.In practical applications,liquid organic mixtures are usually used as heat transfer media.The study of heat transfer process and thermal conductivity of aldehydes,ketones and alcohols organics and their mixtures is not only of practical significance,but also can provide reference for the heat transfer study of other organics.However,the thermal conductivity mechanism of liquid organics is still not fully elucidated.In addition,there are many difficulties in obtaining the thermal conductivity by experimental methods.Most of the engineering applications use empirical or semi-theoretical methods to calculate the thermal conductivity,and in some cases there are large deviations.In contrast,the thermal conductivity of liquid organics obtained by computational simulation is more reliable in both theory and application.Therefore,in this study,the heat transfer processes of a series of aldehydes,ketones and alcohols and their three binary liquid organic mixtures were simulated using a nonequilibrium molecular dynamics（NEMD）.The microscopic heat transfer processes of aldehydes,ketones and alcohols and their three binary liquid organic mixtures were investigated,and the microscopic heat transfer mechanisms of liquid organics were explored at the molecular level,and the main research works are as follows:（1）The heat conduction processes of a series of aldehydes,ketones and alcohols at four temperatures were simulated by the NEMD simulation.The relative deviations between the calculated and experimental values of the thermal conductivity of the three organics were less than 4.32%,4.86% and 4.94%,respectively,and the relative mean deviations were less than3.24%,2.62% and 3.77%,respectively,indicating that the simulation results were basically consistent with the experimental results.By analyzing the heat flux decomposition,partial thermal conductivity and heat transfer efficiency,the results indicate that the heat energy is mainly transferred through torsion angle,bending angle,Coulomb interaction and kinetic energy.In addition,as the molecular chains grow,the heat energy transferred through nonbonded interactions decreases and the heat energy transferred through bonded interactions increases,which indicates a significant relationship between the heat transfer mechanism and the molecular structure of aldehydes,ketones and alcohols.（2）The thermal conductivity of heptane,hexanal,2-hexanone and hexanol at 263～363 K were simulated by the NEMD simulation,and the corresponding thermal conductivities were calculated.The relative deviations between the calculated and experimental values of thermal conductivity at 263～363 K for the four organics were less than 7.31%,7.11%,7.15% and9.23%,respectively,and the relative mean deviations were less than 5.40%,5.46%,4.29%and 7.80%,respectively,indicating that the simulation results were basically consistent with the experimental results.The results of the heat flux decomposition and atomic heat path indicate that the Coulomb interaction term,van der Waals interaction term and torsion angle term,which contribute significantly to the total heat flux,all decrease with increasing temperature,which makes the thermal conductivity of the four organics decrease with increasing temperature.It is speculated that the increase in temperature enlarges the atomic vibrations of molecules,accelerates the molecular motion,and decreases the mass density of the simulated system,which causes the above changes in the thermal conductivity of the four organic species.（3）The heat conduction of 3-pentanone + butanol,butanol + decane and heptane +n-undecane at different mass fractions were simulated by the NEMD simulation,respectively.The relative deviations of the mean values of the calculated thermal conductivity of the three binary liquid organic mixtures from the experimental values were less than 9.27%,7.63% and9.76%,respectively,and the relative mean deviations were less than 3.51%,6.65% and 4.13%,respectively,indicating that the simulation results were in general agreement with the experimental results.According to the heat flux decomposition and atomic heat path analysis,it is known that in the three mixtures,the heat energy is mainly transferred through Coulomb interaction,kinetic energy and torsion angle terms.In addition,the molecular structure of the mixtures and the weight fraction of each component are significantly correlated with the heat transfer mechanism.This study provides a microscopic basis for exploring the heat conduction process of liquids and provides a preliminary understanding of the pathways and modes of heat conduction in liquid organic substances,while contributing to the understanding of the microscopic mechanisms of liquid organic mixtures. |
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