地热-Ⅰ型热导仪实验室间互检及改进

作者于1980年访美期间,通过样品的成组对比测试,将我国自行试制的地热-Ⅰ型岩石热导仪与美国地质调查所西部总部地热实验室的改型分棒仪,进行实验室间的互检,历时近三个月。对比结果,既肯定了地热-Ⅰ型热导仪的总体适用性,同时也揭示了几项误差因子,为我实验室尽快筹建地热-Ⅱ型热导仪提出了改进方向和设计依据。本文简要报道互检结果及对各项误差因子的分析。

RESULTS OF THE CROSS-CHECK BETWEEN LABORATORIES ON THE GEOTHERM-I THERMAL CONDUCTIVITY METER AND THE GUIDE LINES FOR FURTHER IMPROVEMENT

The author, while visiting the United States in 1980, made a cross-check through a set of comparative measurements on 65 rock samples between the Geotherm-I rock thermal conductivity meter installed in our laboratory and the modified divided-bar device of the geothermal laboratory in the U. S. Geological Survey(at Menlo Park). Three working states were used during the cross-check:(1)measurements on dry rock samples;(2)measurements on water-saturated rock samples; and(3)measurements on rock fragments. The results indicate that the accumulated error of the two individually developed measuring devices does not exceed ?15% in most cases. In the meantune, it has been revealed that the Geotherm-I device is still subjected to two systematic errors:(1)a systematic error caused by the overall difficiency in diameter of the sample being tested in comparison with the standard samples;(2)a random or systematic error caused by the irregularity in the rock sample surface flatness. The mechanism of correction for the former factor has been preliminarily made clear using an electric network anology calculation with gaining a good correlation curve. Meanwhile, some approxiomate theoretical correction curves for the error due to surface flatness irregularity were obtained using an equivalent volume principle. After above-mentioned two corrections, the agreement of the results from two instruments is better than ?10%.The results of the cross-check gave following guide line for the further improvement of the Geotherm-I device:1. Standardigation of rock sample diameters;2. Improvement of the structure of the standard samples;3. Application of water-saturated working state during measurements:4. Installation of a cross-check system within the laboratory;5. Realization of quantitative control and direct display of working pressureAll these points are the major base lines for designing a GEOTHERM-II rock thermal conductivity meter.