Bhavaraju N C, Cao H, Yuan D Y, Valvano J W, Webster J G
Flint Hills Scientific, Lawrence, KS 66049, USA.
IEEE Trans Biomed Eng. 2001 Feb;48(2):261-7. doi: 10.1109/10.909647.
This paper presents an experimental technique to measure the directional thermal conductivity and thermal diffusivity of materials. A heated thermistor heats the sample and a sensing thermistor placed about 2.5 mm away measures the temperature rise due the heating pulse at the heated thermistor. An empirical relation between the power delivered by the first thermistor and the temperature rise recorded by the sensing thermistor is used to measure the thermal conductivity of the material along the line joining the thermistors. Diffusivity of the material is determined from the delay between the power pulse in the heated thermistor and the temperature pulse at the sensing thermistor. Signal processing was done to eliminate errors in the measurement due to change of base line temperature. Uncertainty of the measurement technique was found to be 5% when tested in media of known thermal properties. The thermal conductivity and thermal diffusivity of swine left ventricle in normal and ablated conditions were measured using this technique. The thermal conductivity of the tissue dropped significantly from 0.61 to 0.50 W.m(-1).K(-1) after ablation while the diffusivity dropped from 2.1 x 10(-7) to 1.7 x 10(-7)m2.s(-1).
本文介绍了一种测量材料定向热导率和热扩散率的实验技术。一个加热的热敏电阻加热样品，一个放置在约2.5毫米远处的传感热敏电阻测量由于加热热敏电阻处的加热脉冲而引起的温度上升。利用第一个热敏电阻传递的功率与传感热敏电阻记录的温度上升之间的经验关系来测量材料沿连接热敏电阻的直线方向的热导率。材料的扩散率由加热热敏电阻中的功率脉冲与传感热敏电阻处的温度脉冲之间的延迟确定。进行了信号处理以消除由于基线温度变化而导致的测量误差。在已知热特性的介质中进行测试时，发现该测量技术的不确定度为5%。使用该技术测量了正常和消融条件下猪左心室的热导率和热扩散率。消融后组织的热导率从0.61显著下降到0.50W·m(-1)·K(-1)，而扩散率从2.1×10(-7)下降到1.7×10(-7)m2·s(-1)。
