Thermal Properties Analysis And Simulation Of Electrically Heated Garments

Electrically heated garments can provide heat for people who work and live in low temperature environment,reduce people's risk of frostbite,and local heating can keep cold parts of the body warm.However heating element is an important part of electrically heated garments.Based on this,the thermal properties(including resistance,heating rate,surface temperature uniformity,equilibrium temperature and other indicators)of carbon fiber,heating unit integrated with carbon fiber and electrically heated garments were studied systematically.Further based on the heat transfer theory of multi-layer fabric,a simplified three-dimensional finite element model of fabrics system embedded with heating unit was established using ANSYS system,and the steady state heat transfer simulation was carried out.The temperature distribution in the cross section and surface of the fabrics system with internal heat source were studied,so as to provide reference for optimized design of electrically heated garments in winter.In this paper,firstly,the resistance stability,the maximum load current,the rising temperature of carbon fiber,and the relationship between the power consumption and the equilibrium temperature were studied.10 cm long 12 K carbon fiber were chosen.The experimental results show that the resistance change rate of carbon fiber filament is less affected by voltage and ambient temperature,and the heating rate is fast.The power consumption and equilibrium temperature of carbon fiber filament have a highly positive linear correlation,and the coefficient of determination(R~2)is 0.977.Then,the carbon fiber heating plate was prepared in parallel with 3 bundles of carbon fiber filament.The equilibrium temperature of heating plate and the heating power are closely related.And under 5 V load voltage,the equilibrium temperature of the heating plate reaches 45.1?.The infrared temperature images show that the temperature uniformity of heating plate is better.Finally,the heating plates and the heating circuit were integrated into the garment body of the clothing,and the power of electrically heated garments was tested.The results shows that the heating power of heat plate,the ambient temperature and the fitting degree of the garment will affect the heating effect of electrically heated garments.When the heating power is different,the temperature difference between the same parts of electrically heated garments is bigger.The bigger the heating power is,the higher the temperature is.When the heating power is 4.08 W,the back temperature is the highest,which is 34.3?,followed by the chest,the waist and the abdomen.Therefore,to make the heating effect of the heating clothing better,it is necessary to make the clothing that is more consistent with the human body curve.In order to explore how the heat generated by the heating plate is transferred in electrically heated garments,a three-dimensional finite element model of fabrics system embedded with heating unit was established using ANSYS system to simulate different models under different conditions to obtain the temperature field distribution of the model.The simulation results show that when the power output of the heating plate is the same,the lower the ambient temperature is,the lower the temperature of the heating plate is.This is consistent with the experimental results.According to the wearing environment,the output power of the heating plate can be selected reasonably.By comparing the simulation results of the heating plate with the longitudinal stripes with that of the uniform heating plate,the amount of heat transfer along the model plane can be increased by dispersing the heating zone of the heating plate.Therefore,in order to save the heating material,it is possible to reasonably optimize the interval distance of the heating area according to heat generation and control the temperature distribution in the interval distance.With the increase of the thickness of air layer,model surface temperature becomes lower.When the thickness of the air layer is large,further considering the complex heat transfer in the air layer.It can be simulated by modifying the equivalent thermal conductivity of the air,and with the increase of the equivalent thermal conductivity of the air,the heat transfer distance in the model is increased.