Study And Prediction Of Heat Transfer Performance Of Thermal Textile Considering The Skin Tissue

With the increase of demand and users of heat therapy products,the demand for its quality of fever is also increasing.In this paper,the finite element method is used to simulate the temperature distribution on the surface and inside of the skin tissue under the action of the heat treatment products.The BP neural network is used to establish an effective analysis model of the heat treatment of the skin tissue,which in turn giving help in setting heat temperature,the combination ways and the heating time of the textiles,and provide theoretical reference for design optimization of thermal therapy products.First of all,making different carbon fiber heating elements which with different temperatures,measuring three common plain textiles of thermal performance parameters in the market.Selecting the parts of the human body(arm and the back neck)as the experimental sample,and test the maximum temperature of the skin layer of human skin tissue when it in the situations of ditferent skin tissue layer thickness,different heating element temperature,and different inner and outer layers covering the fabric.All the results dates are used as verification samples to verify the accuracy of the BP artificial neural network model obtained from subsequent training.Secondly,this paper establishes the micro-geometric model of thermotherapy textiles,and uses finite element method to simulate the influence of yarn heating temperature,covering fabric and pore filler(coating)on the horizontal and vertical temperature field distribution of the inner and outer surfaces of the micro-model.The results show that the increase of the heat transfer coefficient of the heating yarn temperature or the covering fabric can increase the lateral heat transfer distance of the fabric.When 10wt%SiC coating is a pore-filling material in the fabric,the fabric can be effective in reducing heat loss in the heat transfer process.The heat transfer analysis results obtained by the microscopic model supplemented the macroscopic model research of Chen Yang and other heating fabrics,and the results were the same,indicating that the microscopic model and the macroscopic combination model can effectively and accurately characterize the heat transfer characteristics of the heating fabric.On the basis of the above,a macroscopic model of the heating element-fabric-skin tissue assemble is established.Considering the heat transfer performance of skin tissue,the temperature distribution of different fabric-skin tissue models was simulated by ANSYS under different load constraints of different environmental conditions,and the temperature distribution of skin tissue in two layers and three dimensions was obtained.The results showed that under the same fever condition,the maximum temperature of the epidermis layer and the dermis layer increased almost the same,and the temperature rise of the subcutaneous tissue layer was smaller than that of the epidermis layer and the dermis layer.Therefore,when designing the heating temperature of the hyperthermia product,it is necessary to consider the target temperature to be reached at the lesion site(subcutaneous tissue),not only the temperature rise of the epidermis.The scald time threshold can be calculated according to the skin tissue heat flux.The thicker the subcutaneous tissue layer of the human body,the smaller the maximum temperature that can be achieved,and the smaller thickness of the subcutaneous tissue layer,the more uniform of the temperature distribution.Therefore,when setting the heating temperature of the thermotherapy fabric,it is necessary to flexibly set the heating temperature for different people and different body parts.The distance between the heat sources can also be set according to the thickness of the subcutaneous tissue layer of the user to ensure the uniformity of heat generation of the skin tissue.The thermal conductivity and thickness of the inner and outer fabrics have a common influence on the heat transfer in the model.The inner layer fabric should have a large thermal conductivity.The outer layer of the heating sheet should have a larger thickness and a lower thermal conductivity.It can increase the heat transferred from the heating elements to the skin tissue;reduce the heat loss of the heating elements to the outside to improve the heat utilization rate of the heating sheet;using the nano-SiC coating materials to make the heating film can effectively improve the temperature uniformity of the fabric-skin tissue.The data is obtained as a training sample which taken by the finite element method introducing into the BP artificial neural network method.The thickness of subcutaneous tissue layer,the thickness of inner layer fabric,the inner layer fabric thermal conductivity,the thickness of outer layer fabric,the outer layer fabric thermal conductivity,the heating element heating temperature as the input of the artificial neural network,Skin tissue epidermis,dermis,subcutaneous tissue maximum temperature,skin tissue heat flux as a network output.The experimental results were imported into the training model,and the prediction accuracy errors of the temperature and heat flux of each layer were all within 5%.It is shown that the established neural network prediction model is reasonable and can accurately predict the heat transfer results of the heating sheet-skin tissue-fabric.It can be used to guide and predict the design and functional evaluation of thermal therapy textiles and garments,and has certain commercial value.