Assessment of the heat transfer characteristics and cooling performance of firefighter cooling vests using thermal manikins

Firefighting suits worn by firefighters in high-temperature radiation environments, coupled with moderate physical exertion, can lead to body heat accumulation and increased microenvironment temperature inside the suits, which triggers adverse physiological reactions due to severe heat stress, resulting in decreased work efficiency, heat cramps, and other harms. Hence, cooling vests are widely used by firefighters to effectively alleviate heat stress in firefighting scenarios. However, most contemporary cooling vests encounter issues such as severe cold stress, short cooling duration, and poor comfort. Therefore, it is necessary to conduct research on the cooling performance of these vests.

The cooling effectiveness of three types of firefighter cooling vests was assessed using a thermal manikin system in an environmental chamber under the following conditions: temperatures of 35 ℃, 40 ℃, and 45 ℃ and directed thermal radiation of 1.5 and 2.5 kW/m², with low, moderate, and high levels of physical exertion. D1922L temperature sensors were deployed on the thermal manikin system to measure the temperatures of the outer, insulation, comfort, and inner layers of the cooling vest as well as the temperatures of the inner and outer layers of the firefighting suit.

The experiments reveal that the cooling vests effectively reduce the microenvironmental temperature inside the firefighting suit, with a temperature difference of 6.6 ℃ between the inner and outer layers of the firefighting suit after 200 min of exposure. The cooling effect is most pronounced in the abdominal area with direct radiation. Among the three types of cooling vests assessed, Cooling Vest 1 exhibits the best performance, achieving a cooling power of 4.097 W and a cooling duration exceeding 2 h. Meanwhile, Cooling Vest 3 has a relatively poor cooling performance, with a cooling power of 0.753 W and a cooling duration of 90 min. As the physical exertion levels increase, the cooling effect of the vests is less pronounced. The linear fitting slopes of the temperature variation curves for the manikin's abdominal areas at 65, 110, and 165 W/m² are 0.106 8, 0.273 4, and 0.508 6, respectively. Furthermore, the cooling performance of the vests diminishes with increasing environmental temperatures. At an environmental temperature of 45 ℃, the temperature gradients in the manikin's chest, shoulders, abdomen, and back areas increase by 50.0%, 40.6%, 60.0%, and 50.0%, respectively. Moreover, the directed thermal radiation has a significant impact on the cooling performance of the vests. The temperature of the manikin's chest area reaches 35.69 ℃ within only 7 min with a directed thermal radiation of 2.5 kW/m².

These research findings are anticipated to serve as the preliminary data to enable the determination of rational work durations and intensity. In real fire rescue scenarios, the distribution of phase change materials for heat storage over the chest area and the duration of high-intensity work should be carefully considered. Additionally, these findings provide technical support for the development, testing, and evaluation of personal thermal protective equipment.