地幔热导率的选取对动力学数值模拟的影响——以岩石圈张裂过程为例

目前存在有多种地幔热导率模型,不同模型在数值和随温压变化的特征上有明显的差异.为探究不同热导率模型对动力学数值模拟结果的影响,本文对不同模型下的岩石圈张裂过程进行模拟研究,探讨地幔热导率对岩石圈热传输、变形和熔融过程的影响及其作用机理.结果显示,不同热导率模型下,岩石圈的变形和熔融特征表现出明显差异.高热导率模型下,岩石圈破裂较晚,形成陆缘较为宽阔,地壳熔融强烈而地幔熔融较弱;低热导率模型下,岩石圈破裂较早,形成陆缘较为狭窄,地幔熔融强烈而地壳熔融较弱.这种差异源于不同地幔热导率下岩石圈和地幔热状态的变化及相应力学性质的改变.高热导率下,热传导的增温效应显著,岩石圈呈现较热的状态,其强度整体较低,壳幔耦合减弱;而低热导率下,热对流的增温效应显著,岩石圈呈较冷的状态,其强度整体较高,壳幔耦合增强.基于模拟结果,本文认为地幔热导率的选取对动力学模拟的结果有着较为显著的影响,相对于随温压的变化,热导率数值的差异对动力学数值模拟的结果影响更大,尤其是对于地幔熔融过程的影响.     

YRD型高温高压程控岩石热导仪

基于环形热源与点热源传热方程具有相同解的原理，研制一种非稳态相对测量的高温高压岩石热导仪．论述了仪器的结构、测量原理和主要设计思想，介绍了技术指标、数据采集与处理程序．测试结果重复率优于±３％，准确度优于±５％，工作温度为室温至１８０℃．工作压力为常压至２２ＭＰａ．     

青藏高原中部土壤热传导率参数化方案的确立及在数值模式中的应用

本文针对模式发展的需要, 在Farouki土壤热传导率参数化方案的基础上, 综合Johansen和Côté的参数化方案, 发展了一个用于青藏高原中部的土壤热传导率参数化方案, 用“全球协调加强观测计划之亚澳季风青藏高原试验计划(CAMP/Tibet)”中那曲布交(BJ)站实际资料对该方案进行了检验, 并将它用于公共陆面模式(CoLM)中, 对青藏高原那曲地区进行了单点数值模拟试验. 结果表明: 在未冻结及冻结土壤中, 新方案比Farouki方案计算的土壤热传导率小, 更接近实测值. 加入新方案的CoLM模式对土壤温度模拟的准确性比原模式有一定的提高.     

Thermal conductivity of NaCl,MgO, coesite and stishovite up to 40 kbar

The thermal conductivity of NaCl, MgO, coesite and stishovite have been measured as a function of pressures up to 40 kbar (4 Gpa) at room temperature. Polycrystalline coesite and stishovite were synthesized under high pressures and temperatures at our laboratory. An improved version of the comparative method suitable for the thermal conductivity measurement of small samples under high pressures was designed. The zero-pressure values are 0.0189 and 0.0412 cal. cm^?1 s^?1 °C^?1 for coesite and stishovite, respectively. The thermal conductivities were found to increase linearly with pressure, and the increase rates relative to their zero-pressure values were 3.1, 0.68, 0.39 and 0.90% per kbar for NaCl, MgO, coesite and stishovite, respectively. On the thermal conductivity of coesite, the pressure dependence is small and the zero-pressure value is almost the same as that of polycrystalline quartz. On the other hand, the zero-pressure value of stishovite is 2.2 times as large as that of coesite.     

Anisotropic thermal properties of talc under high temperature and pressure

The anisotropic thermal conductivity and diffusivity of talc were simultaneously measured up to 5.3 GPa and 900 K using the pulse transient method. Although significant anisotropy was observed in the thermal conductivity of talc, the average thermal conductivity is comparable to that of olivine and roughly three times greater than that of antigorite. From the ratio of the thermal conductivity to the thermal diffusivity, the heat capacity of talc was evaluated. The pressure derivative of heat capacity was found to be positive, which is related to the anomaly of thermal expansivity of talc above 50 °C at atmospheric pressure.     

Measurements of thermal conductivity and specific heat in volcanogenic rocks

A laboratory installation has been developed together with a technique for determining thermo-physical properties (thermal conductivity and specific heat) in cylindrical rock specimens. The technique is based on iTOUGH2-EOS3 inversion modeling using temperature measurements inside specimens as a result of their short-term heating and subsequent return to the initial temperature. We estimated the thermal conductivity and specific heat for a collection of volcanogenic petrotypes that reflect the rocks that compose the Rogozhnikovskii volcanogenic oil reservoir (29 specimens). The average thermal conductivity of the dry rocks is 1.47 W/m °C and the average specific heat is 754 kJ/kg °C; the reproducibility of this estimation is 2.2% for thermal conductivity and 0.7% for specific heat.     

岩石稳定平板热导仪

制成了一种岩石稳定平板热导仪, 通过与已知热参数的标准样品比较, 可测定导热系数.测试中消除标本界面热阻的影响, 保证精度要求, 并减少岩石样品加工的时间.      

Temperature and Pressure Dependencies of Thermal Transport Properties of Rocks: Implications for Uncertainties in Thermal Lithosphere Models and new Laboratory Measurements of High-Grade Rocks in the Central Fennoscandian Shield

Measurements on thermal conductivity and diffusivity as functions of temperature (up to 1150 K) and pressure (up to 1000 MPa) are presented for Archaean and Proterozoic mafic high-grade rocks metamorphosed in middle and lower crustal pressures, and situated in eastern Finland, central Fennoscandian Shield. Decrease of 12–20% in conductivity and 40–55% in diffusivity was recorded between room temperature and 1150 K, which can be considered as typical of phonon conductivity. Radiative heat transfer effects were not detected in these samples. Pressure dependencies of the samples are weak if compared to crystalline rocks in general, but relatively typical for mafic rocks.The temperature and pressure dependencies of thermal transport properties (data from literature and the present study) were applied in an uncertainty analysis of lithospheric conductive thermal modellings with random (Monte Carlo) simulations using a 4-layer model representative of shield lithosphere. Model parameters were varied according to predetermined probability functions and standard deviations were calculated for lithospheric temperature and heat flow density after 1500 independent simulations. The results suggest that the variations (uncertainties) in calculated temperature and heat flow density values due to variations in the temperature and pressure dependencies of conductivity are minor in comparison to the effects produced by typical variations in the room temperature value of conductivity, heat production rate or lower boundary condition values.     

Numerical simulation of divided-bar thermal conductivity measurements

Summary A three-dimensional numerical model of the divided-bar thermal conductivity measuring device that can include both solid and fluid sample portions has been developed. The model has been employed to investigate the effects of porosity in divided-bar measurements and the effects of the distribution of solid sample and contained fluids in porous material on the thermal conductivity calculated from the bar temperature measurements. The results show that the positions of the temperature sensors and thus the nature of the vertical column between the temperature measuring points is of prime importance, and that the sizes of the solid and fluid portions of the sample affect the sample conductivity estimates. The divided bar measures the thermal conductivity parallel to the axis of the bar. Thermal conductivity variations in the radial direction have little effect on the calculated conductivity. Whether or not the sides of the bar are insulated strongly affects the calculated conductivity.Presented at the International Meeting on Terrestrial Heat Flow and the Structure of Lithosphere, Bechyn Castle, Czech Republic, September 2 – 7, 1991.     

Prediction of thermal conductivity in reservoir rocks using fabric theory

An accurate prediction of the thermal conductivity of reservoir rocks in the subsurface is extremely important for a quantitative analysis of basin thermal history and hydrocarbon maturation. A model for calculating the thermal conductivity of reservoir rocks as a function of mineral composition, porosity, fluid type, and temperature has been developed based on fabric theory and experimental data. The study indicates that thermal conductivities of reservoir rocks are dependent on the volume fraction of components (minerals, porosity, and fluids), the temperature, and the fraction of series elements (FSE) which represents the way that the mineral components aggregate. The sensitivity test of the fabric model shows that quartz is the most sensitive mineral for the thermal conductivity of clastic rocks. The study results indicate that the FSE value is very critical. Different lithologies have different optimum FSE values because of different textures and sedimentary structures. The optimum FSE values are defined as those which result in the least error in the model computation of the thermal conductivity of the rocks. These values are 0.444 for water-saturated clay rocks, 0.498 for water-saturated sandstones, and 0.337 for water-saturated carbonates. Compared with the geometric mean model, the fabric model yields better results for the thermal conductivity, largely because the model parameters can be adjusted to satisfy different lithologies and to minimize the mean errors. The fabric model provides a good approach for estimating paleothermal conductivity in complex rock systems based on the mineral composition and pore fluid saturation of the rocks.     

Comparing parametrization of the coefficient of molecular thermal conductivity of the thermosphere

At present, different parametrizations of the molecular thermal conductivity coefficient are used in the models of the dynamics and neutral and ion composition of the thermosphere. These parametrizations have been compared by solving the energy balance equation for medium-global conditions. The spread in estimates reaches ～300 K for temperature of the thermosphere and ～40% for density at an altitude of 300 km. A new parametrization of the molecular thermal conductivity coefficient has been proposed. This parametrization is based on the renewed temperature dependences of molecular conductivity [Uribe et al., 1990] according to measurements in pure N₂ and O₂ gases and on the last theoretical estimates of O atom elastic collision sections [Kharchenko et al., 2000].     

Thermal properties of vesicular rhyolite

Thermal diffusivity of rhyolite melt and rhyolite foam (70–80% porosity) has been measured using the radial heat transfer method. Cylindrical samples (length 50–55 mm, diameter 22 mm) of rhyolite melt and foam have been derived by heating samples of Little Glass Mountain obsidian. Using available data on heat capacity and density of rhyolite melt, the thermal conductivity of samples has been determined. The difference in thermal conductivity between rhyolite melt and foam at igneous temperatures ( 1000°C) is about one order of magnitude. The effect of thermal insulation of magmas due to vesiculation and foaming of the top layer is discussed in terms of the data obtained using a simple illustrative model of magma chamber convection.     

Porosity determinations and the thermal conductivity of rock fragments with application to heat flow on Cyprus

A standard core analysis technique has been modified to estimate porosities from measurements on rock fragments. For the range of rocks tested, chip-determined fractional porosities were within ±0.025 of the values measured on solid-core samples. This has enabled thermal conductivity measurements on rock fragments to be corrected for the effect of porosity, yielding agreement with conductivity determinations on solid core generally to better than ± 10%. The application of this is illustrated by the determination of heat flow in a 300-m borehole in western Cyprus (latitude 34°54′N, longitude 32°34′E, elevation 82 m). A decrease in temperature gradient with depth is almost completely compensated for by increasing thermal conductivity, and the best value for heat flow at this site is 23 ± 4 mW m^?2.     

水合物合成及导热系数测定

设计了一套实验装置，结合瞬态面热源法来测量混合气水合物导热系数及含混气水合物的沙子多孔介质的有效导热系数.在-10℃～5℃，压力66MPa下，含体积比甲烷9001%，乙烷503%，丙烷496%的混合气与0971mol/m3十二烷基磺酸钠水溶液生成的水合物的导热系数约为055W/(m·K)，并且其值随温度的上升而增高，呈玻璃体导热特性.由于“爬壁”效应的存在，混合气与饱含SDS水溶液的沙子多孔介质反应生成含混合气水合物的沙子多孔介质的有效导热系数（约12W/(m·K)）显著低于含四氢呋喃水合物的沙子多孔介质的值（约19W/(m·K)）.虽然本实验使用了SDS来加速和促进水合反应的进行，但是水合物样品中依然存在游离水，因此本研究采用了温度振荡法来进一步促进含SDS水溶液的水合反应进行，研究发现当浴槽温度在-10℃～4℃间周期变化时，游离水在水的相变温度区附近转变为水合物，通过几个周期的温度振荡，样品中的游离水被完全消耗掉.最后通过对含不同浓度SDS的四氢呋喃水合物导热系数测试，讨论了实验中加入SDS对水合物导热系数的影响，结果认为本实验中加入的SDS量对测试结果影响很小（±15%）.     

Performance Enhancement of Solar Latent Heat Thermal Storage System with Particle Dispersion — an Exergy Approach

Phase change material (PCM) employed latent heat thermal storage (LHTS) system has been showing good potential over the years for energy management, particularly in solar energy systems. However, enhancement in thermal conductivity of PCMs is emphasized as PCMs are known for their poor thermal conductivity. In this work, the thermal performance of a shell and tube LHTS module containing PCM‐metal particles composite is investigated while charging and is compared with that of pure PCM system. The effect of particle dispersion on latent heat capacity of pure PCM is also analyzed. Enthalpy based governing equations are solved numerically adopting FLUENT code. Exergy based performance evaluation is taken as a main aspect. The numerical results are presented for various operating conditions of heat transfer fluid (HTF) and indicate considerable performance improvement of the system when particles are dispersed.     

Interrelations Between Thermal Conductivity and Other Physical Properties of Rocks: Experimental Data

— A new non-contact and non-destructive optical scanning instrument provided a large number of high-precision measurements of thermal conductivity tensor components in samples of sedimentary and impact rocks, as well as new insights into interrelations between thermal conductivity and other physical properties. More than 800 core samples (dry and fluid-saturated) of sedimentary rocks from different Russian oil-gas deposits and impact rocks from the well “Nördlingen 1973” drilled in the Ries impact structure (Germany) were studied using optical scanning technology. It was established that the thermal conductivity parallel to the stratification is more informative for petrophysical investigations than the thermal conductivity perpendicular to the layering. Different approaches were developed to estimate porosity, permeability, pore space geometry, and matrix thermal conductivity with a combination of thermal conductivity measurements in dry and fluid-saturated samples and mathematical modelling. These approaches allow prediction of the rock porosity and permeability and their spatial distribution along a well using thermal conductivity measurements performed with the optical scanning instrument directly applied to cores. Conditions and constraints for using Lichtenecker-Asaad's theoretical model for the estimation of porosity and thermal conductivity of sedimentary rocks were determined. A correlation between thermal conductivity and acoustic velocity, porosity, density, and electric resistivity of impact rocks was found for different rock types. New relationships between permeability, electrical and thermal conductivity found for sedimentary rocks are described.     

湿热老化后膨胀型钢结构防火涂层导热系数数值计算

通过对已有多孔材料导热系数计算模型的总结和分析,提出了湿热老化后膨胀型钢结构防火涂层导热系数的计算模型。为考察该模型的计算精度,进行了湿热老化试验及隔热性能试验,测量涂层膨胀倍率、炭化层泡孔尺寸和钢板温度等数据。结果显示,湿热老化后炭化层泡孔尺寸增大导致涂层导热系数增大,隔热性能下降,钢板温度上升。利用本文试验测量数据（泡孔尺寸）计算炭化层导热系数,再根据炭化层导热系数的数值计算结果分析钢板温度,并将钢板温度的计算结果与试验结果进行对比,两者吻合良好,验证了膨胀型防火涂层导热系数计算模型的适用性。     

A Method to Estimate the Hydraulic Conductivity of the Ground by TRT Analysis

The knowledge of hydraulic properties of aquifers is important in many engineering applications. Careful design of ground‐coupled heat exchangers requires that the hydraulic characteristics and thermal properties of the aquifer must be well understood. Knowledge of groundwater flow rate and aquifer thermal properties is the basis for proper design of such plants. Different methods have been developed in order to estimate hydraulic conductivity by evaluating the transport of various tracers (chemical, heat etc.); thermal response testing (TRT) is a specific type of heat tracer that allows including the hydraulic properties in an effective thermal conductivity value. Starting from these considerations, an expeditious, graphical method was proposed to estimate the hydraulic conductivity of the aquifer, using TRT data and plausible assumption. Suggested method, which is not yet verified or proven to be reliable, should be encouraging further studies and development in this direction.     

Lattice and radiative thermal conductivity variations through high p, T polymorphic structure transitions and melting points

A steady-state radial heat flux method is used to determine the apparent, lattice and radiative, thermal conductivity and its p, T-dependence up to 6 GPa and over a wide temperature range from 300 to 1600 K. The method employs a differential thermocouple to resolve small changes in temperature gradient due to a line source placed in a sample space subjected to well-defined uniform test temperatures. Measurements are made using an on-line computer. The method is shown to be eminently suitable for determining: (1) the p, T-dependence of the phonon conductivity of cubic single crystals and polycrystalline samples; (2) minima in the apparent thermal conductivity marking the onset of radiative contributions; (3) isolation of phonon and radiative components at high T; (4) conductivity variations caused by progressive polymorphic structure transformations; and (5) conductivity variations through high-pressure melting points into the liquid phase.Results for cubic structures such as MgO and NaCl give good agreement with existing standard values at low temperatures. The conductivity of MgO goes with the inverse of the temperature which is expected from 3-phonon processes. The conductivity of NaCl is of the form λαT^?1.32 with the deviation most likely due to thermal expansion effects.At higher temperatures, a radiative contribution was observed in NaCl and CaCO₃. Calculated values of the extinction coefficient of NaCl increase slightly with pressure.     

Porosity and Thermal Conductivity of the Soultz-sous-Forêts Granite

— The success of the Soultz-sous-Forêts Hot-Dry-Rock project depends on the ability to maintain fluid circulation in a fractured granite. Fractures represent the main fluid pathways. To understand the behavior of this granite in respect to thermal fluid-rock interaction the important aspects are (1) the porous network around these fractures and (2) the thermal conductivity of the rock. This granite is altered and composed of different weathered facies. Variations of porosity and thermal conductivity take place in regard to the alteration and fracturing of the granite. Two types of porosity measurements were performed, mercury injection and water porosity on two samples sizes. The two methods give similar porosity values between 0.3% and 10%. Thermal conductivity measurements were performed in two perpendicular directions to look at anisotropy with two methods at different scale and value ranges from 2.3 to 3.9 W.m^?1.K^?1. Optical scanning provides us with a good knowledge of local increase of thermal conductivity due to sealed fracture or quartz-cemented matrix. The relationship between porosity and thermal conductivity is not obvious and has to be studied in details, and results show three cases: (1)?a relationship between conductivity and porosity (increase of conductivity with a decrease of porosity), (2)?a relationship between conductivity and sealed fractures (increase of conductivity related to an increase of fracture density), (3)?and a combination of the two previous ones. The results are carefully compared for different types of granite: alterated, fractured or both. These first results indicate that parameters such as thermal conductivity are linked to the porous medium, the structure and the mineralogy of the rock.