| Wearing impermeable chemical protective clothing would cause heat stress such as increased body temperature and heart rate.In severe cases,dehydration and intolerance will occur,and even cause serious consequences such as heat injury and death.In order to enhance the safety and comfort,it is necessary to relieve the heat stress in the condition of wearing impermeable chemical protective clothing.The passive microclimate cooling system can absorb the heat generated by human body,and it is more suitable for the working environment where people wear impermeable chemical protective clothing due to its advantages of no power supply,reliable performance and simple structure.At present,there are few researches on the cooling effect of passive microclimate cooling system under the condition of wearing impermeable chemical protective clothing.Therefore,research on the cooling effect of passive microclimate cooling system under the condition of wearing impermeable chemical protective clothing is of great practical significance for optimizing the technical design of passive microclimate cooling system and effectively improving the thermal and physiological comfort.The main work of this paper includes using the method of human thermal physiological experiment to study the influence of impermeable chemical protective clothing on heat stress.The influencing factors of the cooling efficiency of the passive microclimate cooling system were analyzed,and combined with the influencing factors,passive microclimate cooling systems were designed and made for the working environment of impermeable chemical protective clothing.The cooling efficiency of the passive microclimate cooling system for impermeable chemical protective clothing was compared and analyzed by the thermal manikin experiment method and the human thermal physiological experiment method.The evaluation method of the cooling efficiency of passive microclimate cooling system was improved by combining the thermal manikin method with the human thermal physiological experiment method.In this paper,human thermal physiological experiments were carried out firstly,focusing on the effect of impermeable chemical protective clothing on heat stress.In a hot and humid environment with air temperature of 35℃ and relative humidity of 60%,eight subjects wore three kinds of chemical protective clothing to exercise with different intensities.The tolerance time,core temperature,mean skin temperature,heart rate,heat storage rate were measured and calculated.Wearing a heavy impermeable chemical protective clothing caused a more severe heat stress than wearing a breathable chemical protective clothing or a light impermeable chemical protective clothing.Under the same slope movement,the human body wearing a heavy impermeable chemical protective clothing within 30 minutes had a core temperature rise of 0.74°C,a mean skin temperature rise of 3.12°C,a heart rate rise of 69 bpm,a heat accumulation of 269.93 k J,and a heat storage rate of 149.96 W.And the tolerance time was only 46 minutes,which was shortened by 20.69% and 13.21% respectively compared with the tolerance time of wearing breathable chemical protective clothing and light impermeable chemical protective clothing.Based on the heat balance equation under the condition of wearing impermeable chemical protective clothing,combined with the cooling principle of passive microclimate cooling system,the factors affecting the cooling effect of passive microclimate cooling system were analyzed,and the passive microclimate cooling systems were designed and manufactured.The influence of the properties of phase change materials(PCM)and the design of the system structure on the cooling effect of the passive microclimate cooling system was studied by the thermal manikin experiment.When the passive microclimate cooling system has the same structural design,as the amount of PCM increases,the mean cooling power of the passive microclimate cooling system gradually increases,and the effective time gradually increases.The amount of PCM would not significantly influence the maximum cooling power of passive microclimate cooling system,and the maximum cooling power increases with the increase of the contact surface area between PCM and human body.With the decrease of PCM package size,the effective time of passive microclimate cooling system becomes shorter,the maximum cooling power increases gradually,and the mean cooling power increases gradually.As the specific heat capacity of PCM increases,the maximum cooling power of passive microclimate cooling system increases gradually.With the increase of PCM latent heat and thermal conductivity,the mean cooling power of passive microclimate cooling system increases gradually,and the effective time increases gradually.The mean cooling power per unit area per unit mass varies with different types of PCM,but is less affected by PCM dosage,PCM package size and system structure.The effectiveness of passive microclimate cooling system to relieve the heat stress of people wearing impermeable chemical protective clothing was studied through human thermal physiology experiment.Eight subjects wore impermeable chemical protective clothing in a hot and humid environment.After wearing the passive microclimate cooling system,the body core temperature dropped by 0.46°C,the mean skin temperature dropped by 0.76°C,and the subjects complained that there was no local skin overcooling during the entire experiment.The heart rate drops by 6 bpm,which effectively relieves heart rate pressure.The sweating rate decreased by 2.47g/min,and the heat storage rate decreased by 80.75 W.The tolerance time was extended by 9.21 minutes,an increase of 26.9%.In the hot and humid environment,personnel wearing impermeable chemical protective clothing,passive microclimate cooling system can significantly reduce the thermal physiological reaction,prolong the tolerance time,and effectively alleviate the heat stress.To optimize the evaluation method of cooling effect of passive microclimate cooling system,a walk-sweat combined mode of thermal manikin was proposed.The results showed that compared with the static sweating mode stipulated in ASTM F2371 standard,the measurement accuracy of the walk-sweat combined mode of the thermal manikin was improved by 17.30%,which could more accurately evaluate the cooling effect of the passive microclimate cooling system under the condition of wearing the impermeable chemical protective clothing. |
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