热系数测量方法及生物油导热系数研究.pdf

中国科学技术大学
硕士学位论文
高精度热探针导热系数测量方法及生物油导热系数研究
姓名:张宏泽
申请学位级别:硕士
专业:热能工程
指导教师:程文龙
20070601
摘要
热探针法是一种常用的测量松散粉末、颗粒材料和液体等物质导热系数的方
法,具有快速方便的特点。但是传统的热探针方法,由于自身系统误差难以消除,
导致测量结果精度不高。由生物质原料快速热解产生的生物油是一种可再生能
源,生物油的导热系数是其利用过程中的一个重要的热物性参数,但是,国内外
对于生物油导热系数的研究成果却不多。生物油的成分很复杂,部分成分易挥发,
这给生物油导热系数的测量带来一定的难度。
针对传统的热探针测量方法,本文提出了对有效测量数据的判断准则,该准
则利用实验数据的最佳线性原理,对实验数据点进行有效合理地筛选,得出有效
测量数据,从而能够在一定程度上提高实验测量精度。
热探针的热容以及直径所造成的系统误差是导致实验精度不高的一个重要
原因,为了克服传统热探针方法的系统误差,本文提出了蒙特卡洛反演的热探针
导热系数测量法。这种方法是从热探针导热问题微分方程的精确解出发,充分考
虑热探针热容的影响,同时在不需要主观地对有效测试时间段进行筛选的情况
下,就能在比较短的时间里准确得到待测样品的导热系数。
在上述研究的基础上,本文建立了热探针测量实验系统,测量结果显示:采
用蒙特卡洛反演方法对于水、甘油、硅油以及无水乙醇的平均测量误差约为
0.8%,即使对于无水乙醇这类很难用热探针方法准确测量的液体,其测測量误差也
可以控制在1.%以内,其测量精度明显高于传统的热探针方法
本文利用上述导热系数测量系统,对生物油以及添加了甲醇、乙醇、乙酸乙
酯等液体燃料的生物油液体燃料混合物的导热系数进行了测量,得到的实验数
据表明:随着温度的上升,生物油的导热系数变化不大;生物油/液体燃料混合
物的导热系数随着混合物中液体燃料质量百分比的升高而下降。
通过生物油以及生物油/液体燃料混合物的导热系数实验数据,得出了几种
导热系数预測方程,这几种预测方程的计算值与实验数据的偏差在1.49%以内。
关键词:热探针法;导热系数;蒙特卡洛法
Abstract
The thermal probe method is commonly used to measure the thermal conductivities
of loose powders, granular materials and liquids. However, the precision of the
traditional thermal probe method is not high enough since its systematic error is hard
to be eliminated. The bio-oil produced from rapid pyrolysis of raw biomass materials
is a kind of renewable energy. Its thermal conductivity is one of the major thermal
parameters in its applications. However, the previous investigations for its thermal
conductivity were rarely epo ed It is paly due to the complicated composition of
the bio-oil and some volatile components, which limit the measurement of its thermal
conductivity
For the traditional thermal probe method, this thesis presents a kind of judgment
criteria to the effective measurement data. By use of the best linear theory. the criteria
can help screen the data points reasonably and get the effective measurement data,
which can partly improve the measurement accuracy.
The systematic eror derived from the heat capability and diameter of the thermal
probe is an important reason for the low accuracy of experiments. To further improve
the experiment accuracy, a method for the thermal conductivity measurement with the
utilization of the Monte Carlo inversion based on the exact solution of the thermal
probe is presented. The influence of the thermal probe, that is, its thermal capacity and
diameter, was considered. With this method, the thermal conductivity of liquid is
accurately measured in a relatively short time without any subjective screening to the
effective experiment time
In this thesis, the thermal conductivities of water, glycerol, silicon oil, and
ethanol were measured using the Monte Carlo inversion method. The average error is
about 0.8%. Even for ethanol, which is hard to measure with the traditional method,
the error can be controlled within 1.5%. The measurement accuracy is obviously
higher than that of traditional thermal probe method
By the use of the mentioned measurement system, this thesis measured the