碳素纤维发热元件电热性能的研究

为了提高碳素发热元件的电热性能,测试了不同工艺碳素纤维发热元件的电热温升和热惯性,针对碳素纤维发热元件的结构特性,建立了其传热方程并进行求解.结果表明:无芯碳素纤维发热元件在相同表面负荷范围内的电热温升约高出支撑芯元件20℃以上,而股线无芯元件的瞬时温升约高出支撑元件60℃以上;惰性气氛下对碳素纤维进行瞬时高温除杂,所得元件电热温升和120s时瞬时温升约高出其他元件10℃以上;采用5%和30%两种定型胶质量浓度所得元件的电热温升差约40℃左右、140s时瞬时温升差约60℃左右,较高质量浓度的定型胶可提高元件电热温升、减小热惯性.碳素纤维的发射率是影响元件电热性能的重要指标,提高发射率可获得电热温升高、热惯性小的碳素发热元件.

Electrical thermal properties of carbon fiber heating elements

In order to improve the electrical thermal properties of carbon fiber heating elements,the characteristics of electrical thermal temperature increment and thermal inertia of carbon fiber heating elements with different processes were tested,and the thermal transfer equation was established and solved according to the special structure of carbon fiber heating elements.Results show that the carbon fiber heating elements without supporting core have higher temperature increment of more than 20 ℃ in the same surface power density range than the elements with supporting core,and the instant temperature increment for thread type elements without supporting core is over 60 ℃ higher than that of the elements with supporting core.By performing surface desizing for carbon fiber by instant high temperature process in inert gases,the temperature increment and instant temperature increment at 120 s are 10 ℃ higher than those of the elements treated by other surface desizing processes.Moreover,the difference of temperature increment for the two kinds of elements made by 5% and 30% concentrations of holding glue is about 40 ℃ and the difference of instant temperature increment is about 60 ℃.Improving the concentration of holding glue can increase the electrical thermal temperature rise and decrease the thermal inertia for the carbon fiber heating elements,which is helpful to achieve high-efficient and high-sensitive no-core carbon fiber heating elements.The emissivity of carbon fiber is an important index influencing the variation of electrical thermal properties.The high temperature rise and low thermal inertia carbon fiber heating elements can be obtained by improving the emissivity.