Metabolic Rate Measuring with Indirect Calorimetry for Thermal Comfort Evaluation

The metabolic rate (MET) is a fundamental parameter influencing thermal comfort. In this paper, the MET is obtained by indirect calorimetry to propose equations and related laws applicable to the environment at an altitude of 4 m, so as to enrich the research. Here, experiments with 30 healthy male subjects are conducted at sitting, 2, 4, and 6 km/h walking speeds in various ambient environments controlled by the climate chamber. The MET, thermal sensation vote (TSV), and heart rate (HR) were collected during the experiments. The results indicate that the ambient environments have little impact on MET, but it is obvious for HR. The linear relationship between walking speed, HR, and MET is fitted to be MET = 28.38 × Speed + 62.25 and MET = 3.67 × HR − 195.56. Moreover, the TSV and five kinds of predicted mean vote (PMV) calculated by various sources of MET are compared. For sitting activity, a slight difference from the MET could cause a significant difference in PMV, which leads to the PMV that may be above, below, or close to the TSV. For the 2 km/h walking activity, five kinds of PMV are close to TSV. However, for the 4 km/h walking activity, PMV is always higher than TSV. These findings are significant in elucidating the relationship between MET and thermal comfort.