# Experimental Investigation into the Thermal Performance of Personal Cooling Mechanisms
## 4 Discussion  
According to the results of mean skin temperature, it was noted that during low-energy activities, the mean skin temperature of the manikin when wearing various cooling vests tended to be lower than that of the manikin without a vest. This suggests that the different cooling mechanisms effectively contribute to decreasing the manikin's mean skin temperature during this level of activity. As the activity level escalated to moderate metabolic activity, the manikin wearing different cooling vests displayed lower mean skin temperatures than the nude manikin, except when wearing cooling vest 4, which utilises phase change materials (PCMs). However, during high metabolic rate activity, only when wearing cooling vest 2, which employs an air-cooling mechanism, did the manikin demonstrate lower mean skin temperatures.  
The hypothalamus temperature range, indicative of thermal comfort for individuals, is typically between 36.1 \({}^{\circ}\)C and 37.1 \({}^{\circ}\)C. When assessing the effectiveness of various cooling vests, it was observed that during low-energy activities, the initial mean skin temperature of the manikin fell within this range, suggesting a state of thermal comfort. However, as the activity level increased to a moderate metabolic rate, the hypothalamus temperature of the nude manikin rose to 38.1 \({}^{\circ}\)C, like the temperature observed in the manikin wearing cooling vest 4, the vest with PCMs, implying limitations in effectively lowering core temperatures. Conversely, with the same activity level, the manikin wearing the cool water circulation vest, the air-cooling vest, or the water evaporation cooling vest maintained a hypothalamus temperature of 36.9 \({}^{\circ}\)C, indicating thermal comfort. During high metabolic rate activity, the manikin wearing cooling vest 2, the air circulation vest, exhibited the lowest hypothalamus temperature of 37.1 \({}^{\circ}\)C, the only vest with an adequate thermal comfort at this level.  
The thermal sensation is associated with the mean skin temperature and hypothalamus temperature. At low activity levels, the manikin wearing the cooling vests had better thermal sensation than the nude manikin, suggesting that all the cooling vests effectively improved the manikin's thermal sensation. As the activity level increased to a moderate metabolic rate, the thermal sensation of the manikin wearing the different cooling mechanisms remained better than that of the manikin without any vest, except for the manikin wearing cooling vest 4, the PCM vest. This indicates that this cooling vest could only improve the thermal sensation of the manikin at low-energy activities. After conducting high metabolic rate activities, it was observed that only the manikin wearing vest 2, the air-cooling vest, had improved thermal sensation. This indicates that the air-cooling vest effectively enhanced the manikin's thermal sensation during low, moderate, and high activity levels.  
Figure 6: Comparison of the thermal comfort index across different metabolic rates.  
The results regarding the thermal comfort index indicate a direct relationship between mean skin temperature, hypothalamus temperature, and thermal sensation. The nude manikin was found to be slightly uncomfortable. In contrast, the manikin wearing various cooling vests demonstrated improved thermal comfort, especially at low activity levels, as reflected in thermal sensation measurements. The cool water circulation vest, air circulation vest, and evaporation vest enhanced thermal comfort compared to the nude manikin and the PCM vest during moderate activity levels. However, at high energy activity levels, only the air circulation vest significantly improved the thermal comfort of the manikin.