| With the popularization of home passenger vehicles in China,vehicular hyperthermia caused by solar radiation which lead to child death has become a social issue of great concern.In this paper,the predicted heat strain model(PHS)is used to study the children's heatstroke and survival time in enclosed vehicles.Firstly,the predicted heat strain model(PHS)is programmed by using the LabVIEW virtual instrument platform.The calculation process and writing logic of heat strain in LabVIEW program are sorted out.The input parameters,output parameters and judgment conditions of the program are explained in detail.It is the base for the modification of the program according to the parameters for children.Secondly,since the PHS model is established based on the study of standard adults,this paper establishes a cylindrical model for children and adults to theoretically calculate the heat transfer of children and adults and explore the difference between them.It is found that because children have a larger body surface area to mass ratio,their body temperature rises faster and they are more prone to danger in the same high temperature environment.The PHS was adjusted according to the characteristics of children,and the feasibility of PHS applied to children was verified by comparing experimental data.Thirdly,because PHS requires the input of environmental parameters,this paper measured the thermal environment parameters of the vehicles in the outdoor environment and wind tunnel environment in summer.The experiment found that when the car is socked in hot environment,if the cabin temperature equal to ambient temperature in the begining,the cabin air temperature can be 22~24°C higher than the ambient temperature after 1h,and the temperature rise mainly occurs in the first 40 minutes.If the car starts to heat up from 23.2°C after the air conditioner is turned off,the air temperature will rise by 34.9°C in 1 hour.Through comparison experiments,it is concluded that the temperature rise in different vehicles varies,and the difference of thermal environment parameters at different positions in the vehicle is small.Turn on the air conditioner in the car,adjust to the maximum cooling,maximum air volume,and blown surface mode.The front and rear seats have strong air blowing feeling.After the air conditioner is turned on for the first 10 minutes,the air temperature in the cabin drops significantly.The front seat temperature drops by 37.0°C.The seat temperature dropped by 32.1°C.Finally,based on the children's parameters,this paper uses the LabVIEW program of PHS,combined with the measured cabin ambient temperature,to simulate the heat strain of children in the cabin.The rectal temperature is the main physiological symptom judgment index.Children will unable to bear at 38?,heat stroke at 40?,and die at 42?.If a 1-year-old boy under low metabolism of 70W/m2 and dry relative humidity of 30%condition,was left in the cabin which temperature rise from 23.2°C.The model male child will reached unbearable state within 48minutes,heat stroke within 67 minutes,and demise within 81 minutes.If the vehicle starts to warm from an ambient temperature of 38?,the child will reached unbearable state within 31 minutes,heat stroke within 49 minutes,and demise within 63 minutes.Considering that children's metabolic rate rises sharply when children cry loudly,and the relative humidity of the car is increased due to evaporation of human body,the situation of children will be more critical.For example,if the child's metabolic rate is 100 W/m~2 and the relative humidity of the compartment is 50%,in the rear of the car which air temperature rises from 23.2?,the child's fatal time will be shortened to 61 minutes.Older children have a slightly longer allowable exposure time in the car.And there is a smaller difference in gender.Therefore,in the summer,if the caregiver closes the air conditioner in the car and go shopping for 1 to 2 hours,leaving the child alone in the car,it will cause serious harm to the child's life and health. |
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