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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The thermal properties of porous andesite
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The thermal properties of porous andesite

机译：多孔矿石的热性能

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The thermal properties of volcanic rocks are crucial to accurately model heat transfer in volcanoes and in geothermal systems located within volcanic deposits. Here we provide laboratory measurements of thermal conductivity and thermal diffusivity for variably porous andesites from Mt. Ruapehu (New Zealand) and variably altered basaltic-andesites from Merapi volcano (Indonesia) measured at ambient laboratory pressure and temperature using the transient hot-strip method. The specific heat capacity of each sample was then calculated using these measured values and the bulk sample density. Thermal conductivity and thermal diffusivity decrease as a function of increasing porosity, but specific heat capacity does not vary systematically with porosity. For a given porosity, saturation with water increases thermal conductivity and specific heat capacity, but decreases thermal diffusivity. Measurements on samples from Merapi volcano show that, compared to the unaltered samples from Mt. Ruapehu, hydrothermal alteration deceases thermal conductivity and thermal diffusivity, and increases specific heat capacity. We use an effective medium approach to parameterise these data, showing that when the porosity and pore-fluid properties are scaled for, the measured values agree well with theoretical predictions. We find that despite the microstructural complexity of the studied andesites, porosity is the principal parameter dictating their thermal properties. To understand whether the measured changes in thermal properties are sufficient to influence natural processes, we model heat transfer from magma to the surrounding host-rock by solving Fick's second law cast in 1D Cartesian (dyke geometry) and cylindrical (conduit geometry) coordinates. We provide models for different host-rock porosities (0-0.6), different initial magmatic temperatures (800-1200 degrees C), and different levels of host-rock alteration. Our modelling shows how the cooling of a dyke and conduit is slowed by a higher host-rock porosity and by increased hydrothermal alteration. The thermal properties provided herein can help improve modelling designed to inform on volcanic and geothermal processes. (C) 2020 Elsevier B.V. All rights reserved.
机译：火山岩的热性质对于准确地模拟火山和位于火山沉积物内的地热系统中的热传递至关重要。在这里，我们为来自Mt的可变多孔和岩石的导热率和热扩散性提供实验室测量。 Ruapehu（新西兰）和来自Merapi火山（印度尼西亚）的可变改变的玄武岩 - 使用瞬态热带法测量在环境实验室压力和温度下。然后使用这些测量值和散装样品密度计算每个样品的比热容量。热导率和热扩散率随着孔隙率的函数而降低，但是比热容量不随孔隙率系统地变化。对于给定的孔隙率，用水饱和增加导热性和比热容量，但是降低了热扩散性。来自Merapi Volcano的样本的测量表明，与来自Mt的未改变的样本相比Ruapehu，水热改变会降低导热性和热扩散率，并增加比热容量增加。我们使用有效的介质方法来参数化这些数据，表明当孔隙率和孔隙流体性能缩放时，测量值与理论预测很好。我们发现，尽管研究了洞中的微观结构复杂，但孔隙度是指示其热性能的主要参数。要了解热性能的测量变化是否足以影响自然过程，我们通过在1D笛卡尔（Dyke Geometry）和圆柱形（导管几何）坐标中求解Fick的第二律铸造，从岩浆到周围主机岩石的热传递。我们为不同的宿主岩石孔隙（0-0.6）提供模型，不同的初始岩浆温度（800-1200摄氏度）和不同水平的宿主岩石改变。我们的建模显示了如何通过更高的宿主岩孔隙度和增加的水热改变来减慢堤坝和导管的冷却。本文提供的热特性可以帮助改善旨在通知火山和地热过程的建模。 （c）2020 Elsevier B.v.保留所有权利。

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