## 4 Results and Discussion  
### Validation of the Method  
As a first step in the implementation of a new device to obtain experimental values of any thermophysical property, a set of tests to validate the technique should be mandatory, though often omitted [12]. Thereby, we observed the goodness of the application of the THW theoretical model by comparing the measured temperature rise with the one obtained from Equation (6) in the temperature range 283.15 to 333.15 K. As an example of the operation of the conductivity meter, Figure 2 shows raw data of a THW test with Milli-Q water as working fluid. The \(\Delta T_{\text{exp}}\)-In(\(t\)) relationship is displayed following Equation (6) and with a linear tendency over 100 ms, as usual [12; 36], highlighting this zone with a shading. Therefore, data below this time should be disregarded (non-shaded zone in Figure 1) to accomplish good metrological quality in the determination of the thermal conductivity, as explained by [PERSON] et al. [12]. The procedure explained above was applied to each fluid considered in this work, and a least squares linear fitting was performed in the time range from 300 to 800 ms of the measured \(\Delta T_{\text{exp}}\)-In(\(t\)) charts, in which the linear trend can be guaranteed. Figure 3 accounts for the comparison between the experimental temperature rises (\(\Delta T_{\text{exp}}\)) and those obtained from the linear regressions (\(\Delta T_{\text{reg}}\)) of the three independent tests for W, EG, PG, EG:W 50:50 vol% mixture, \(n\)-C\({}_{14}\), and \(n\)-C\({}_{16}\), up to 1 s. The agreement is within \(\pm 1\%\) (95% level of confidence), which directly impacts on the repeatability of the device, as discussed below. Figure 1: Scheme of the thermal conductivity device: (**1**) THW-L2 device, (**2**) EchoTerm Dry Bath, (**3**) sample container, (**4**) sample cell, and (**5**) THW sensor. Tests were performed in such a way that the obtained temperature rise followed the recommendations of the manufacturer (2-3 K for low viscosity samples and 3-4 K for high viscosity ones). To accomplish this fact, the software runs a preliminary test prior to any measurement to determine an appropriate heating power to achieve the required temperature rise, as above-mentioned. Above results show that there are some systematic and random deviations on these thermal conductivity experiments, which come from departures between the assumed mathematical model and the current measured data. Here, we present a throughout analysis of the source of these uncertainties based on the corrections derived by [PERSON] et al. [24]. Throughout these corrections, the ones applicable to our experimental device are those that come from the thermophysical properties of the wire (non-zero heat capacity and finite thermal conductivity), \(\delta T_{1}\); outer boundary conditions, \(\delta T_{2}\); radial convection and viscous dissipation, \(\delta T_{4}\); radiation heat transfer, \(\delta T_{5}\); variable fluid properties, \(\delta T_{7}\); and truncation error of the exponential integral, \(\delta T_{9}\), respectively. This selection agrees with the recommendations published by [PERSON] and [PERSON] [3]. A careful examination of these absolute deviations was performed, and results are summarized in Table 2.  
None of the deviations exceeds 0.01%, in line with the level of deviation accepted in the literature [20; 24; 36]. This means that the design of the THW-L2 instrument was carefully performed taking into account these corrections to minimize them. Nevertheless, as previously reported, we found a disagreement of 1% between the experimental temperature rise and the regressed one; 99% of this deviation comes from other effects that are not usually considered in the literature, such as from the assumption of constant heating rate.