9. Calculations and Report
9.1 Calculate the thermal conductivity of the sample using Eq 2, used in conjunction with appropriate values of A and B, as follows:
9.2 Calculate a preliminary value of KL using each set of experimental data collected in the manner described above. Average the last three such values to obtain the final value. The reported test temperature shall be the arithmetic mean of the bath temperature and the wire temperature determined from the cell resistance.
NOTE 3 - When cgs units are used, the units of KL are cal/s·cm·°C. The conversion factors in Table 1 can be used to calculate units in other commonly used systems. The use of cgs units followed by conversion of the units KL as required is recommended as a matter of convenience only as they permit the easy performance of the various calculations involved in the approximate solution of the Callendar equation for conversion of resistance thermometer readings to actual temperatures.
NOTE 4 - When testing a liquid at a temperature less than 90 % of its absolute 50 % boiling point at one atmosphere, as measured by Test Methods D86, D1160, D2887, D2893, the thermal conductivity data may be expected to be a nearly linear function of temperature. Specifically, if changes in the function Δλ/ΔT over two successive ranges of 100°C differ by more than 40 %, the operator should consider recalibration of the apparatus.
10. Precision and Bias
10.1 Because of the complex nature of the procedure for the determination of thermal conductivity and because of the expensive equipment involved in the initial set-up of the procedure, there is not a sufficient number of volunteers to permit a cooperative laboratory program for determining the precision and bias of the method. If the necessary volunteers can be obtained, a program will be undertaken at a later date. As a preliminary estimate, repeatability appears to be about 10 % of the mean of two results by the same operator.
11. Keywords
11.1 nonmetallic liquids; thermal conductivity