Research On Heat Transfer Of The System Of Human Body-chemical Protective Clothing-environment Based On CFD

In recent years,China’s industrialization process has been accelerating,and with the increase of production capacity,chemical leaks and other safety accidents have occurred frequently.Skin is the main way to toxic chemical exposure,and chemical protective clothing,as personal skin protection equipment,is always playing an important role in safeguarding the safety of the staff.Chemical protective clothing,which is large in structure and weight,has the characteristics of high thermal resistance and strong isolation performance,which prevents dry heat and water vapor from diffusing.In face of hot environment or heavy work,it is easy to trigger heat stress,and may be even fatal.Therefore,it is necessary to accurately evaluate and optimize the heat transfer properties of chemical protective clothing to lengthen the wearing time of the clothing and reduce its potential injuries.The numerical simulation method of computational fluid dynamics integrates fluid dynamics,computer and visualization processing technology,which can deeply explore the complex heat and flow transfer and other physical phenomena between the system of human body-chemical protective clothing-environment,avoiding the shortcomings of traditional experimental method and one-dimensional mathematical model,such as high cycle cost and incomplete consideration of garment structure effects.It is of great significance to the design and production of chemical protective clothing,the guidance of use and the optimization of heat transfer performance improvement.In this essay,through the numerical simulation method of computational fluid dynamics,we studied the effect of structural changes of chemical protective clothing on the heat transfer of the system of human body-chemical protective clothing-environment under different ambient temperatures and wind speeds.We also analyzed the changes of the heat flow rate of the body skin surface,the temperature of the air gap of the clothing,and the air flow state of it.We finally evaluated the heat transfer performance of the chemical protective clothing so as to provide data support for the design,production and safe use of chemical protective clothing.Here were the main research contents.(1)Established a feasible three-dimensional model of the dressed torso and indoor dressed human body,extracted the domains,divided the appropriate computational grids and determined the computational models and algorithm.(2)Through laboratory tests and literature review,determined the thermophysical and optical performance parameters of materials and boundaries conditions involved in heat and flow transfer simulations,such as fluid,chemical protective fabric and walls under various study environments.(3)By simulating the steady-state heat and flow transfer in the torso-microenvironmentchemical protective clothing and human body-connected chemical protective clothingindoor environment through computational fluid dynamics method,studied the effects of the air layer under the chemical protective clothing,the ventilation opening of the garment,the ambient temperature and wind speed on heat and flow transfer.(4)The Stolwijk 25-node human thermal regulation model was used to construct a coupled heat transfer system to study the skin temperature changes in 27 ℃ environment with different metabolic rates when the human body wears a one-piece chemical protective clothing of different structures.After researching,we’ve drawn the following conclusions.(1)The air flows up and down from the hem of the chemical protective clothing to the collar,and the insulation effect is the best when the thickness of the air layer under the suit is 10 mm at the speed of 0.06 m/s.The heat transfer performance of the protective suit is better when the thickness of the uniform air layer under the suit is 8 mm to 20 mm after the speed is increased.(2)The non-uniform underclothing space caused by the wrinkles on the surface of the protective clothing makes the average heat flow on the skin surface of the torso increase significantly,and the better the thermal comfort performance of the fabrics used in the protective clothing,the more likely they are to be affected by the clothing wrinkles.(3)Setting one-way ventilation outlet in the middle of the back or the middle of the back waist is more conducive to cool torso.If ventilation outlet radius is 2.0 cm,the hot air dissipates quickly,and if ventilation radius is 2.5 cm,heat dissipation will be smoother.(4)It is the best when the heat transfer performance of the torso,arms and legs closes one-piece chemical protective clothing with a uniform thickness of 10 mm or 20 mm under the air layer in a windless environment.The heat transfer performance of the chemical protective clothing with a thickness of 10 mm under the air layer in a windy environment is better,and the heat transfer performance of the collar,cuffs and trouser leg opening ventilated chemical protective clothing with a thickness of 30 mm under the air layer is also better.(5)The setting of ventilation openings has a strong auxiliary effect on releasing the heat accumulating in the air space near the shoulders,underarms and crotch of the chemical protective clothing,and the improvement of the heat transfer effect of the chemical protective clothing is better than replacing the materials used to make the protective clothing.(6)It is recommended that the continuous working time of the human body wearing one-piece chemical protective clothing in medium activity intensity should not exceed 35 min,and when the activity level is high,it should not exceed 20 min.