## 4 Results and Discussion
### Proposal of Correction Factor \(\Delta\lambda/\lambda\)  
Hereafter, we expose a method to correct the systematic deviations found and discussed in the last section. The differentiated deviations of the thermal conductivity depending on the fluid could be explained by an overestimation of the applied heating power, \(\dot{q}\), for low thermal conductivity fluids, disallowing the establishment of the stationary regime due to deficient viscous dissipation (high viscosity fluids) or convection effects (low viscosity fluids) [50]. Consequently, a careful analysis of the performance of the equipment with the fluids to be studied should be carried out. This fact entails the use of this device working with common conventional heat transfer fluids or nanofluids (lower than 0.700 W m\({}^{-1}\) K\({}^{-1}\)). It should be mentioned that the manufacturer states that its operational thermal conductivity range is 0.01 to 2 W m\({}^{-1}\) K\({}^{-1}\). Average deviations between our experimental data and those from the literature are reported in Figure 6 as a function of the mean thermal conductivity, \(\overline{\lambda}\), of the fluid in thestudied temperature range. It must be noted that the variation of the thermal conductivity in this narrow temperature interval is very low, less than 0.079 W m\({}^{-1}\) K\({}^{-1}\) for all the fluids. Figure 6 evidences that average deviations between experimental and literature thermal conductivity values are lower with increasing thermal conductivity of the fluid. Furthermore, these deviations suggest a linear tendency over the thermal conductivity range. Hence, we propose the following empirical relationship identified as a correction factor, \(\Delta\lambda/\lambda\), to correct the above-mentioned systematic deviation effects:  
\[100\bigg{(}\frac{\lambda_{\text{exp}}-\lambda_{\text{lit}}}{\lambda_{\text{ lit}}}\bigg{)}=5.969-8.45\,\overline{\lambda} \tag{8}\]  
where \(\overline{\lambda}\) (standard deviation of 0.0043) is expressed in W m\({}^{-1}\) K\({}^{-1}\). As previously mentioned, this proposed equation is applicable at the temperature range 283.15 to 333.15 K and the thermal conductivity range 0.100 to 0.700 W m\({}^{-1}\) K\({}^{-1}\). It should be noted that the actual values of the coefficients of Equation (8) are valid only for this particular instrument, including the software. If researchers use other commercial devices, similar procedure should be accomplished to implement this methodology. The proposed correction factor was double checked with a pure molecular fluid, \(n\)-C\({}_{16}\), and MgO/\(n\)-C\({}_{14}\) nanofluid at mass fractions of 1, 5, and 10 wt%, with both samples being measured at 303 K. Thermal conductivities of the nanofluids were also determined in this work by using a KD2 Pro (Decagon Devices, Pullman, WA, USA) [35]. The employment of Equation (8) provides noteworthy decreases of the discrepancies in THW-L2 values, obtaining reductions in the thermal conductivity deviations from 7.5 to 2.3% for \(n\)-C\({}_{16}\)[51, 52, 53, 54]. In case of MgO/\(n\)-C\({}_{14}\) nanofluids, these reductions were from 9.1 to 4.3% at 1 wt%, from 8.6 to 3.7% at 5 wt%, and from 9.3 to 4.4% at 10 wt%. Following the methodology and recommendations throughout this paper, it is possible to obtain reliable experimental thermal conductivity data from the THW-L2 device once the correction factor is applied. Taking into account the impacts of the departures of the temperature rise from the ideal model, the repeatability of thermal conductivity values, the deviations from literature data, and the proposed correction factor for the raw experimental data, an expanded uncertainty of 5% (\(k=2\)) was estimated. The proposed methodology can be applied to other commercial instruments following the reported procedure, especially when a proper calibration cannot be afforded. Thus, systematic deviations in thermal conductivity data would be reduced, leading to a standardization of the operation with such devices, in particular for nanofluids research community.