Analysis and evaluation of the thermal performance of combinations of suits and life jackets in water

Abstract

Life jackets are essential life-saving devices, and also play an important role in the thermal protection of drowning victims in cold water. To better understand the thermal performance of the combinations of suits and life jackets in water, a thermal manikin named “Walter” in a water tank was used to simulate the environment surrounding the drowning person. Three sets of suits and three sets of life jackets form a total of 12 test combinations to simulate the clothes worn by drowning people. The thermal resistance of 12 combinations in water were measured according to ISO 15831 and heat transfer coefficients for the chest, back, upper arm, arm, thigh and leg of the 12 test combinations were calculated and compared. Results showed that the combinations of the clothes and life jacket efficiently lowered conduction and convective heat transfer coefficients in the water. The total thermal resistance of the 12 test combinations ranged from 0.011 to 0.054°C · m2/W. The post-hoc analysis revealed that the conductive thermal resistances of the clothing combinations with life jackets were all elevated compared to those of the clothing combinations without life jackets ( p < 0.001), showing that life jackets provide better thermal insulation. The linear regression indicated that the conductive thermal resistance of the test combination had a considerable impact on the convective heat transfer coefficient. This study helps to establish the systematic study of the thermal protection performance of life jackets.

A Coupling System for Prediction of Physiological Parameters in an Immersed Condition

“…A thermal manikin is a crucial instrument for measuring thermal comfort and evaluating local heat exchange in clothing today. They allow for repeated testing and eliminate inaccuracies caused by subject variability while avoiding the high expenses and ethical obligations associated with real-life testing [11]. Thermal manikin investigations are frequently pessimistic compared to actual test results because a thermal manikin cannot replicate the thermoregulatory response of the human body [12], and it is challenging to generate vasoconstriction and cold fibrillation responses.…”

“…Based on this, researchers have also created numerous human thermal models, most of which have been focused on applications in air exposure conditions to replicate human physiological reactions [13][14][15]. When using water as the heat transfer medium in watery situations, the methods with which human, clothing, and the environment transmit heat are more complicated [11]. Due to its 3500 times greater volumetric specific heat capacity and 25 times stronger thermal conductivity, water can absorb heat more effectively than air [4].…”

“…Montgomery et al [16], Xu et al [17], and Wu et al [18] proposed thermal models to simulate the physiological responses under low-temperature immersion environments. Kim et al [19] and Yang et al [11] conducted tests with a thermal manikin and used empirical equations to predict the thermal comfort of people wearing life preservers in water. The truth is most thermal manikins are more inclined for passively studying the heat exchange from the human body to the environment through clothing and are unable to make active adjustments to the complex environment, while the human thermal model can better simulate the thermal regulation response of the human body; however, considering that the heat transfer mechanism of the life jacket in the submerged environment is very complex, the model may be inaccurate in predicting the amount of heat transfer from the human body through the life jacket in the submerged environment [18].…”

Modification and Validation of a Dynamic Thermal Resistance Model for Wet-State Fabrics

“…As the "second skin" of the human body, clothing is the most important barrier for maintaining thermal stability [1]. Clothing should help maintain the body's thermal and moisture balance, enabling the body to be in a state of psychological, physiological, and sensory comfort during long periods of work and activity.…”