Rapid Measuring And Studying On The Thermal Conductivity Of Binary System

In modern industry, especially in chemical and petroleum, it widely refers to mass over-all heat transfer process and most of them are liquids in these fields. Thermal conductivity is one of an important thermal physical parameter for expressing heat exchange. It is practically significant in theoretic study and manufacture practice, But these data are quite lack comparing of other thermal physical parameters. Moreover, the coherence about reportorial data doesn't meet with current literature very well and the discrepancy is more than 10%～20% by different experimenters. Along with the development of modern technology and measuring apparatus, thermal conductivity is requested to increase veracity and that of binary system or multi-group system is needed more and more. So, the measurement and study on thermal conductivity of binary mixtures looks imminent.The over-all heat transfer process of liquids is very complex and it has three ways: heat conduction,convection,radiation. In this paper, it was only discussed thermal conductivity with single heat transfer form that was heat conduction. Therefore, the influence of natural convection and radiation must be avoided or restrained at maximum limit. Considering the influence, the apparatus established in this experiment was mostly shown that: the time of measurement was short, only one second; the temperature rise was less than 0. 6℃.In this paper, based on the principle of transient relative method, the experimental apparatus for measuring thermal conductivity of liquids has been discussed in detail. Firstly, the apparatus was calibrated at 25℃,50℃and atmosphere by using six reference liquids (glycerol,ethylene glycol,methanol,acetone,toluene and heptane) with known thermal conductivities. The calibration constant A and B as well as the calibration equation of the apparatus were obtained. Secondly, the thermal conductivities of three binary systems in five differential concentration were measured. The mixtures were alcohol—acetone, alkane—acetone, alcohol—water at the same condition. The measuring results were discussed and the error was analyzed. Moreover, the curves of measuring data dV / dt and thermal conductivityλ, dV / dt and concentration x,λand x were separately fitted. Then we obtained the curve equations at 25°C,50°C, which were expressed by polynomial. This work was a try for analyzing and measuring concentration of mixtures. The result was satisfactory. The average error was less than±0.90%. So, in after work, if only known thermal conductivityλor concentration x of liquids at 25°C or 50°C,the same condition, it was convenient that the concentration x or thermal conductivity A obtained from curve equation ofλand x.The calibration equations of the apparatus are: 25°C,λ=0. 6527-0. 0010 dV / dt and 50°C,λ=0. 5944-0. 0009 dV/dt. At the two temperature, the maximum error is about±1.0% by comparing measuring data with literature data. This shows that the measuring results of thermal conductivity of binary system are exact and credible.