# Metabolic Rate Measuring with Indirect Calorimetry for Thermal Comfort Evaluation
## 3 Results and Discussion
### The Comparisons of TSV and PMV  
According to ASHRAE Standard 55 [1], PMV is only applicable to predict the thermal sensation of the body at MET \(<4\) met. Therefore, this research compares the TSV and PMV of sitting and 2 km/h and 4 km/h walking. TSV is the mean value of the thermal sensation vote, which is collected after exercising each activity. PMV\({}_{\text{ISO}}\) is calculated by formulas for PMV in ASHRAE Standard 55, whose values of MET are provided by the activity diary in ISO 8996-2004 [7]. PMV\({}_{\text{SI}}\) is calculated by formulas for PMV, whose values of MET are provided by the linear predictive equation based on speed in this study. PMV\({}_{\text{S2}}\) and PMV\({}_{\text{S3}}\) are resourced from the exponential and quadratic polynomial equations in this study, respectively. Moreover, PMV\({}_{\text{HR}}\) is resourced from the predictive equations for MET based on HR in this study. Further, the values of MET in the cool environment are calculated by the individual equation. The comparisons of TSV and PMV in cold, cool, warm, and hot environments are shown in Figure 13. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Research** & **Linear Relationships** & **R2** & **Data Sources** \\ \hline This study in the cool environment & MET = 3.67 \(\times\) HR \(-\) 195.56 & 0.77 & China \\ This study in other environments & MET = 3.80 \(\times\) HR \(-\) 218.90 & 0.76 & China \\ [PERSON]’s study & MET = 3.27 \(\times\) HR \(-\) 161.30 & 0.68 & China \\ ISO 8996 & MET = 3.80 \(\times\) HR \(-\) 210.00 & — & Europe \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The specific forms of the linear relationships. Figure 13: The comparisons of TSV and PMV in the (**a**) cold, (**b**) cool, (**c**) warm, and (**d**) hot environments. The results show that the TSV is impacted significantly by the environments and activity intensities. For sitting activity, the TSV is \(<\)\(-\)0.5 in the cold and cool environments, and the TSV is \(>\)0.5 in the hot environment. It indicates that the subjects feel thermal stresses in these conditions. The subjects do not feel uncomfortable in the warm environment because the TSV is close to 0. It is worth noting that even though the subjects feel cold, hot, or comfortable in various environments, their MET is markedly unchanged. It suggests that the bodies do not feel strong thermal stresses to regulate heat dissipation due to the suitable clothing. For a 2 km/h walking activity, the subjects feel comfortable in the cold and cool environments according to the values of TSV, but they feel hot in the warm and hot environments. However, the subjects in all environments feel hot because the TSV is always higher than 0.5 for 4 km/h walking activity. It indicates that the subjects feel warmer at the higher activity intensity because it can raise the core temperatures of the bodies. In summary, the TSV always rises following the activity intensity increases and the environment becomes warm. It indicates that the body feels comfortable performing high-intensity activities in a cool environment. In contrast, the body feels comfortable performing low-intensity activities in a warm environment. The discrepancies between TSV and the five kinds of PMV are significantly different at various activity intensities. For sitting activity in all environments, PMV\({}_{\text{S1}}\) is close to TSV, PMV\({}_{\text{ISO}}\) is always lower than TSV, but PMV\({}_{\text{S2}}\), PMV\({}_{\text{S3}}\), and PMV\({}_{\text{HR}}\) are consistently higher than TSV. For the 2 km/h walking activity, five kinds of PMV are not significantly different from TSV, although they are slightly lower or higher than TSV in all environments. For the 4 km/h walking activity, the TSV is always lower than PMV, indicating that PMV overestimates the actual thermal sensations of the human body. Interestingly, PMV\({}_{\text{S1}}\) and PMV\({}_{\text{S3}}\) are the same because the MET calculated by the linear equation is similar to the quadratic polynomial equation in this study.