A method of measuring the thermal conductivity of liquids

We described the development of an apparatus for the determination of the thermal conductivity of liquids. The apparatus is suitable for all kinds of liquids, including the strongest acids. From a given time we pass an electric current through a thin straight wire, placed in a homogeneous material of which the thermal conductivity is to be measured. The constant heat production in the wire causes a cylindrical temperature field in the material. The rise of temperature depends on the thermal properties of the material. The apparatus used is sketched in figure 1. The drawback of the old methods, viz the convection current of the liquid is evaded, because the time in which the measurement is done, is so short that the density differences can not develop a disturbing convection current within this time. The results of the measurements are given in table II. For water we found the same dependence of the thermal conductivity on temperature as F. Schmidt and W. Sellschopp (see figure 9)

On the measurement of the thermal conductivity of liouids by a non-stationary method

In 1949 in this journal 1) a paper appeared dealing with a non-stationary method for measuring the thermal conductivity of liquids. This method, indicated first by Stålhane and Pyk 2), was based upon the temperature rise at a certain distance from an electrically heated wire, producing a constant heat flow into the liquid. Results obtained by using this method were found to be unreliable. The time during which convection does not disturb the measurements appeared to be too short to apply the proposed mathematical approximations. E.g., neglecting the ratio of the specific heats per cm3 of the liquid and the heating wire (c/c00) is not allowed. In consequence of a more rigorous mathematical treatment the method has to be changed to yield the correct results as its application to a series of experimental data shows. As the necessary changes mean a serious drawback of the original method it is suggested to lengthen the time during which measurements are possible by rotating the vessel containing the liquid about the heater to suppress convection