## 2 Basic Analysis of Prediction Models and Model Verification
### Prediction Models of Viscosity and Thermal Conductivity
#### 3.4.1 Prediction Models of Viscosity and Thermal Conductivity
By analyzing the molecular structures of the liquids, it was found that the molecular structure of FC-72 contains two trifluoromethyl groups; the two types of molecular structures of HFE-7100 contain one and two trifluoromethyl groups, respectively; and the molecular structure of Novvec 649 contains three trifluoromethyl groups. It can be judged preliminarily that the contribution values of the trifluoromethyl groups according to [PERSON] et al. [110,111] were too great, or that the modification of the molecular structures including poly-trifluoromethyl was not considered, which is an important reason for the high deviations in the predicted viscosities of Novvec 649. When the NVIS model was used to predict the viscosities of Novvec 649 and HFE-7100, the relative deviations between the predicted and reference values were within 16%. For FC-72, the relative deviations were greater than 20%, and even up to 40%. By comparing the group contribution values given by the three models of SVIS1, SVIS2 and NVIS, it can be found that the group contribution values of \(-\)CF\({}_{2-}\) for the SVIS1 and SVIS2 models was 0, whileas the value of \(-\)CF\({}_{2-}\) in the NVIS model was a non-zero value. Therefore, when  
\[\mu_{\rm dim} =131.3\mu\;/\;(V_{c}\,T_{c})^{0.5} \tag{71}\]1 Relative deviations between the predicted and reference values [68,72] of the thermal conductivities of Novvec 649 and HFE-100 using the PCS model. the NVIS model was used to calculate the viscosities of FC-72, the reason for the larger deviations could have been that the functional group \(-\)CF\({}_{2-}\) with a large contribution value was repeatedly accumulated. In general, all the prediction models described above face the problem of having inaccurate contribution values of their fluorine-containing functional groups. In addition to the above models, a prediction model based on another group contribution method proposed by [PERSON] et al. [120] also showed the same result (not listed in this paper because of its high deviation). According to the studies in this work, there is no prediction model of viscosity with high precision and strong universality. Comparison and Discussion of Different Models of Thermal Conductivity  
The relative deviations of the predicted thermal conductivities of FC-72, Novec 649 and HFE-7100 are shown in Figures 16 and 17. \[\mu_{\rm dim} =131.3\mu\;/\;(V_{c}\,T_{c})^{0.5} \tag{71}\]2 Relative deviations between the predicted and reference values [70] of the viscosities of Novec 649. \[\mu_{\rm dim} =131.3\mu\;/\;(V_{c}\,T_{c})^{0.5} \tag{71}\]3 Relative deviations between the predicted and reference values [64] of the viscosities of FC-72. \[\mu_{\rm dim} =131.3\mu\;/\;(V_{c}\,T_{c})^{0.5} \tag{71}\]4 Relative deviations between the predicted and reference values [68] of the thermal conductivities of Novec 649. \[\mu_{\rm dim} =131.3\mu\;/\;(V_{c}\,T_{c})^{0.5} \tag{71}\]5 Relative deviations between the predicted and reference values [72] of the thermal conductivities of HFE-7100. \[\mu_{\rm dim} =131.3\mu\;/\;(V_{c}\,T_{c})^{0.5} \tag{71}\]6 Relative deviations between the predicted and reference values [74] of the viscosities of HFE-7100. The GTC and STC models based on the group contribution method had the largest relative deviations between the predicted and reference values among the five prediction models in this work, which suggests that the group contribution method may not be the best prediction method for the thermal conductivity of electronic fluoride liquids, and a reason for this may be the inaccurate contribution values of their fluorine-containing functional groups. For the other models (the PCS, RSTC and GHTC models), the relative deviations were basically less than 20%, but the predictive accuracy was still relatively low.