| It is an important function of textiles to resist the severe cold and maintain the normal body temperature of the human body.Different from the traditional passive warm clothing,the new active heating clothing shows better temperature control effect,in particular in that aspect of temperature controllability and stability of the electric heating fabric.But the cost of the electric heating material is generally high,in order to reduce the cost of the raw material for design and production consumption,the electric heating performance of the electric heating model of the conductive fabric can be built,the using efficiency of the heating material and the structure of the heating fabric can be optimized,and the heating efficiency is improved.Electrothermal fabric includes conductive woven fabric and conductive knitted fabric.Compared with knitted fabric,the structure of woven fabric is more stable.The existing heating model of electrothermal fabric is mainly analyzed from the macro level or experimental test point of view,which can not effectively predict the uniformity of heating temperature distribution in electrothermal fabric.And there are some limitations in guiding the distribution of heating elements in the design of electrothermal fabrics.In order to systematically explain the uniformity of heating temperature distribution of electrothermal fabric,it is necessary to establish the heating model of electrothermal woven fabric from the yarn level,which provides a theoretical basis for the design and development of electrothermal woven fabric.In view of the lack of research on heating model and temperature distribution uniformity of electrothermal woven fabric,this paper constructs the electric heating temperature prediction model of conductive yarn and electrothermal woven fabric from the yarn level,which can calculate the temperature in fabric.At the same time,for the two basic arrangement of the conductive yarn heating unit in the machine fabric,the influence of the fabric resistance and the distance of the conductive yarn on the electric heating performance of the fabric is compared and the model is verified and optimized.The specific contents of the study are as follows:(1)Based on the machine fabric yarn unit,the temperature difference of the conductive yarn and the non-conductive yarn in the fabric is introduced,the electric heating model of the electric heat engine fabric is constructed,and the heating temperature and the distribution uniformity of the fabric are predicted.The carbon fiber yarn is used as the heating element to construct its resistance and electric heating model in air,and the electric heating model after weaving into the fabric.According to the two transfer forms of temperature in the fabric,the heat loss of the conductive yarn is divided into the heat convection between the yarn and the air and the heat conduction inside the fabric.The heat loss of the non-conductive yarn is only the thermal countercurrent between the yarn and the air.When the heat transfer of each part is balanced,the fabric reaches the maximum heating temperature.It is found that in order to keep the uniform distribution of heat in the surface,the distance between conductive yarns should not be too large,and the distance between conductive yarns is related to the fabric density and the number of spacing between non-conductive yarns.And the maximum heating temperature of series electrothermal fabric decreases with the increase of total resistance of fabric,but the increase of total resistance of parallel electrothermal fabric will not cause the change of maximum heating temperature of fabric.(2)Two kinds of electrothermal fabrics with different structures were designed and prepared,the model was verified and optimized,and the hypothesis of the model was discussed.the results show that the electric heating model of the fabric can effectively predict the temperature of the electroheated fabric under different voltage conditions.The electrothermal fabric was designed and prepared based on series and parallel structures.The electric heating experiments were carried out under different voltage conditions to verify the model.The results show that the deviation range of the electric heating model and the actual measurement temperature of the single conductive yarn in air is less than 4.64% and the fitting degree is high.It can be seen that the model can be used to predict the maximum heating temperature and fabric temperature uniformity of conductive yarn and series electric heating machine fabrics under different voltage conditions.By adding the influencing factors of temperature to the fabric resistance of parallel conductive motor fabric,the electrothermal model of parallel conductive motor fabric is optimized.The deviation range of the optimized parallel fabric electric heating model and the actual measured value is reduced from 9.81% to 3.41%,and the standard deviation of the deviation value is reduced from 4.31 to 2.11.The fitting degree has been obviously improved.(3)The model is used to optimize the structure of electrothermal fabric,and the effects of fabric resistance and conductive yarn spacing on the electrothermal properties of the fabric are compared.it is found that the heating efficiency of the heating unit is obviously better than that ofthe heating unit when the heating unit is connected in series,and in order to keep the temperature distribution uniform,the maximum spacing is 2mm(4 non-conductive yarns).In order to evaluate the effect of fabric resistance and conductive yarn spacing on the electrothermal properties of fabric,cotton yarn was used as warp yarn,carbon fiber yarn and cotton yarn were arranged as weft,and two kinds of electrothermal fabrics with series and parallel heating elements were prepared.The maximum heating temperature,heating rate,heat dissipation rate and temperature distribution uniformity of the two fabrics were evaluated respectively,and the heating efficiency of the two fabrics was compared and analyzed.The results show that the smaller the distance between conductive yarns is,the higher the maximum heating temperature of electrothermal fabric is,and the higher the heating rate is,the better the temperature uniformity is.Under the same voltage,the greater the fabric resistance,the smaller the maximum heating temperature and the slower the temperature rise rate,but the fabric resistance has no obvious effect on the parallel electrothermal fabric.The heating efficiency when the heating unit is connected in parallel is obviously better than the heating efficiency when the heating unit is connected in series,and the heating efficiency is uniform,and the maximum spacing is 2mm(4non-conductive yarns).In summary,two structure electric heat engine fabric electrothermic model is built from that yarn level,and the temperature uniformity in the fabric is predicted.The different influence of the distance between the fabric resistance and the conductive yarn on the electric heating performance of the two different structure electric heating fabrics is demonstrated,and a certain theoretical basis for the development of the electric heat engine is provided.However,this subject lacks the evaluation of human administration performance,aiming at the temperature uniformity in the model,and can be used for heating the fashion design of different parts of the human body to the sensitivity of the temperature in the future research. |
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