电热织物系统热传递模拟及其参数设计

Heat transfer simulation and parametric design of electric heating textile system

为保证电加热服装的舒适性与安全性,并为其优化设计提供参考,通过Comsol软件建立了包含皮肤层的电热织物系统传热模型,考虑了热传导、热对流、热辐射3种传热方式,进行了多物理场耦合模拟。将模拟的瞬态结果与实验数据进行对比发现,二者随时间变化的温度曲线相近,且实时温度和最终温度相对误差均低于4%,说明模拟值与实验值之间具有良好的吻合性。通过该数值模型进行了稳态的参数化研究,拟合了皮肤温度与环境温度、风速、发热片加热温度、服装内外层热阻之间的线性关系,建立了皮肤温度预测模型,并应用模型设计电加热服装的相关参数。本文研究结果可为特定使用环境下电加热片的设计与选择提供理论参考。

Objective In order to ensure the thermal comfort and safety of users,it is necessary to investigate the performance of electric heating clothing.Electric heating textile system simulation can achieve precise simulation of heating components and explore the effect of various parameters on heating performance.This paper establishes a three-dimensional heat transfer model of an electrically heated fabric system including the skin layer to study the effects of environmental factors,heating temperature,and thermal resistance of the inner and outer layers of the clothing on skin temperature.Based on the influence relationship,a skin temperature prediction model is established.Method A combination of electric heating clothing fabric was adopted,in which the heating component is a carbon nanomaterial heating film.The electric heating fabric system was numerically simulated using Comsol Multiphysics,considering the three heat transfer modes,which are conduction,convection,and radiation.The simulation involved the coupling of multiple physical fields.The effectiveness of the model was experimentally validated using an iSGHP thermal resistance tester and an MSR145 temperature humidity sensor.Results The simulated experiment process obtained real-time temperature,and the simulated curve was compared with the experimental results,demonstrating a similar trend.At the beginning of the plate heating,the simulated heating rate was higher than the experimental value,and then the temperature gradually stabilized and approached the experimental value.There could be two reasons for this situation.1.The heating temperature and heat flux of the simulation did not have a start-up time.In reality,it takes several seconds for the heating plate to reach the desired temperature,and when the temperature difference between the environment and the heating temperature is large,the heating time will be longer.Also,it takes a certain amount of time for the hot plate of the thermal resistance tester to reach the required power.2.The simulation assumes that the fabric is thermally insulated on all sides,but it is difficult to achieve absolute thermal insulation in actual experiments,and there is still a small amount of heat exchange.A parametric study on the model is conducted in a steady state and three regions for skin temperature prediction are selected.Point A represents the skin temperature(T_(ska))beneath the midpoint of the heating detection area,domain B represents the average skin temperature(T_(skb))beneath the rectangular region of the heating detection plate,and point C represents the skin temperature(T_(skc))beneath the edge point of the heating detection plate.Then,the quantitative relationship between skin temperatures(T_(ska),T_(skb),T_(skc))and ambient temperature(T_(a)),wind velocity(V_(a)),heating plate temperature(T_(h)),as well as inner and outer clothing thermal resistances(I_(1),I_(2))was determined through regression analysis method.Based on this,a predictive model for skin temperature was established.For setting the comfort range of skin temperature,it was recommended to meet the following conditions simultaneously,i.e.,the edge point temperature(T_(skc))remains at 34℃,the skin temperature(T_(ska))in the heating detection area no more than 41℃,and the average skin temperature(T_(skb))in the large heating no more than 37℃.Conclusion A three-dimensional heat transfer model of an electrical heating fabric system,including the skin layer,has been established.The transient simulation results are compared with experimental data,showing a close similarity in temperature variation over time.The relative error between real-time and final temperatures is lower than 4%,indicating good agreement between simulated and experimental values.A parameterized study of the steady-state model is conducted based on the linear relationship between the skin temperatures of three regions and the ambient temperature,wind velocity,heating temperature of the heating element,and thermal resistances of the inner and outer layers of the clothing.A predictive model for skin temperature is developed.This skin temperature prediction model can be used to design the heating temperature and the inner and outer layers of the clothing based on the comfortable range of skin temperature under specific environmental conditions.Conversely,given the determined inner and outer layers of the clothing,the environmental conditions and heating temperature of the heating element can be determined based on the comfortable range of skin temperature.By predicting the post-dressing skin temperature,it is possible to assess thermal comfort and optimize clothing design accordingly.