Geothermal measurements in the pilot-boreholes of the china continental scientific drilling

The geothermal measurements in the pilot-boreholes of the China Continental Scientific Drilling (CCSD) indicate that the temperature gradients in the target area of the deep drilling range from 19 to 26℃/km, which is lower than that (25—30℃/km) for the global continental area and similar to that for the KTB (21—28℃/km). Thermal conductivity measurements for 44 core samples show that the ultra-high pressure (UHP) metamorphic rocks have 50% higher thermal conductivity (with a mean of 3.94±1.26 W/mK) than that for the average value of the upper crust. The measured heat flow values vary between 76 and 80 mW/m², higher than that for the global continental area (65±1.6 mW/m²) and the continental China (61±15.5 mW/m²) as well as the adjacent North Jiangsu Basin (68 mW/m²), but lower than that below 1000 m in the KTB (85 mW/m²). The elevated heat flow in the pilot-boreholes can be attributed to the lateral heat concentration due to higher rock thermal conductivity of the UHP belt than that of the adjacent rocks. Lower deep temperature in the target area of the deep drilling can be expected due to the lower measured temperature gradient, which means that the Sulu area is geothermally suitable for continental deep drilling.     

Distribution feature of terrestrial heat flow densities in the Bohai Basin,East China

Temperature logging curves at 8 boreholes and well-testing temperature data at 142 boreholes are used to determine geotemperature gradients in the Bohai Basin. The thermal conductivities of 86 rock samples are measured at laboratory and the effects of porosity and temperature are corrected to obtain conductivities in situ. Terrestrial heat flow densities at 76 wells are determined based on these data. The distribution of the heat flow indicates that the terrestrial heat flow in the Bohai Basin is relatively high with an average value of 65.8 mW/m². This characteristic is caused by the tectonic evolution of the basin. During Cenozoic, the lithosphere stretched intermittently and the crust thinned so that heat conducted from the mantle increased and formed thermal abnormity at depth beneath the basin.     

Geothermal field and thermotectonic evolution in Southern South Yellow Sea Basin

Based on the available borehole temperature data and measurements of thermal conductivities on 10 core samples in the Southern South Yellow Sea Basin, 8 heat flow values are obtained. The results show that the mean values of temperature gradient and heat flow are 28.6“C/km and 69 mW/m^2, respectivdy. The thermal history reconstruction from the inversion of vitrinite reflectance data, using the temperature-gradient method, indicates that the highest paleo-heat flow occurred at the end of the Mesozoic, and then the barn began to cool to present day. Tectonic subsidence analysis shows that the basin experienced at least four episodes of quick subsidence since the late Paleozoic and that the tectonic evolution was quite strong and complex.     

On the asymmetric distribution of heat loss from the Earth’s interior

Mean heat flows and heat Josses of the Northern and Southern hemispheres are calculated using degree 12 spherical harmonic representation of the global heat flow field (Pollacket al., 1993). Mean heat flows and heat losses of 0° hemisphere and 180° hemisphere, with median lines being 0° longitude and 180° longitude, are also calculated. The mean heat flow of the Southern Hemisphere is 99.3 mW·m^¨, significantly higher than that of the Northern Hemisphere (74.0 mW·m^¨). The mean heat flow of 0° hemisphere (94. 1 mW·m²) is also higher than the value of 180° hemisphere (79. 3 mW·m²). The mantle heat loss from the Southern Hemisphere is 22.1 × 10¹² W, as twice as that from the Northern Hemisphere (10.8 × 10¹² W). The 16.9 × 10¹² W mantle heat loss from 0° hemisphere is close to 16.0 × 10¹² W from 180° hemisphere. The hemispherical asymmetry of global heat loss is originated by the asymmetry of geographic distribution of continents and oceans. The asymmetric distribution of heat loss is a long-term phenomenon in the geological history.     

氮化硼纤维填充聚乙烯醇导热复合材料的制备

以聚乙烯醇（PVA）为基体，选用六方氮化硼纤维（BN fiber）作为导热填料，通过溶液共混的方法制备导热复合材料。结合X射线衍射仪（XRD）、扫描电子显微镜（SEM）以及导热测试结果，探究填料的微观形貌以及与基体的界面相容性对于提升复合材料导热性能的影响。结果表明：BN fiber对于提升复合材料的面内导热率有很好的效果，而且采用过氧化氢（H₂O₂）溶液进行表面改性，可以有效改善界面相容性；当经过1 400℃热处理再经过表面改性的BN fiber（BN fiber-1400-H₂O₂）的填充量为5%（质量分数）时，复合材料的面内导热率达到了1.32 W·m^-1·K^-1，为纯PVA体系的629%，相比于表面改性前提升了60%。     

Fabrication and thermal conductivity of copper matrix composites reinforced by tungsten-coated carbon nanotubes

Carbon nanotubes (CNTs) were coated by tungsten using metal organic chemical vapor deposition. Magnetic stirring was employed to disperse the W-coated CNTs (W-CNTs) in a Cu matrix, and then, the mixed powders were consolidated by spark plasma sintering. The W-CNTs obtained a uniform dispersion within the Cu matrix when the W-CNT content was less than 5.0vol%, but high content of W-CNTs (10vol%) resulted in the presence of clusters. The W-CNT/Cu composites containing low content of W-CNTs (<5.0vol%) exhibited a higher thermal conductivity than the sintered pure Cu, while the CNT/Cu composites exhibited no increase in thermal conductivity after the incorporation of uncoated CNTs. The W-CNT content was found to play a crucial role in determining the thermal conductivity of the W-CNT/Cu composites. The thermal conductivity of the W-CNT/Cu composites increased first and then decreased with the W-CNT content increasing. When the W-CNT content was 2.5vol%, the W-CNT/Cu composite obtained the maximum value of thermal conductivity. The thermal resistance of the (W-CNT)-Cu interface was predicted in terms of Maxwell-Garnett effective medium approximation, and its calculated value was about 3.0×10⁻⁹ m²·K·W⁻¹.     

CSP生产线高速钢轧辊温度场有限元分析

采用有限元软件ANSYS,结合某CSP生产线F4机架工作辊表面温度的实测值,建立轧辊二维温度场模型,对轧辊在轧制过程中的温度和热凸度变化进行研究。结果表明,轧辊在咬入弧区的换热系数为5.8×104 W/(m2·K),在非咬入弧区的水冷等效换热系数为1.1×104 W/(m2·K);在此等效换热边界条件下,使轧辊热凸度达到稳定的烫辊时间约为75min。     

Doping effect on thermoelectric properties of nonstoichiometric AgSbTe<Subscript>2</Subscript> compounds

Nonstoichiometric ternary thermoelectric materials Ag_0.84Sb_1.15M_0.01Te_2.16 (M=Ce, Yb, Cu) were prepared by a direct melt-quench and hot press process. The carrier concentration of all the samples increased after doping. Thermoelectric properties, namely electrical conductivity, Seebeck coefficient, and thermal conductivity, were measured from 300 to 673 K. The phase transition occurring at about 418 K representing the phase transition from β-Ag₂Te to α-Ag₂Te influenced the electrical transport properties. The electrical conductivities of Ce and Yb doped samples increased after doping from 1.9×10⁴ to 2.5×10⁴ and 2.3×10⁴ S·m⁻¹, respectively, at 673 K. Also, at room temperature, the Seebeck coefficient of the Ce doped sample relatively increased corresponding to the high carrier concentration due to the changes in the band structure. However, all the thermal conductivities increased after doping at low temperature. Because of the higher thermal conductivity, the dimensionless figure of merit ZT of these doped samples has not been improved.     

扭曲椭圆管内超临界CO2冷却换热的数值模拟

为了提高CO₂热泵的传热性能,基于Fluent的数值模拟方法研究了不同质量流量下,扭距为100 mm及无扭曲状态下的水平椭圆管管内超临界CO₂冷却换热特性及二次流的变化规律,并针对竖直椭圆管引入局部换热系数和压降,研究了长短轴比b/a及扭距对扭曲管换热性能的影响。结果表明,低质量流量下扭曲椭圆管内浮升力明显大于椭圆管扭曲结构所产生的浮升力,对于低质量流量G<200 kg/(m²·s²)下的超临界CO₂流体,椭圆管具有更大强度的浮升力所造成的二次流,强化传热更明显;对于高质量流量G>200 kg/(m²·s²)下的超临界CO₂流体时,扭曲椭圆管具有更大强度自身结构所产生的周期性二次流来强化传热;管内的传热系数及压降随着扭曲程度及压扁程度的增大而增大。为扭曲椭圆管在CO₂热泵中的应用提供了重要的理论与数据支持。     

Selective interfacial bonding and thermal conductivity of diamond/Cu-alloy composites prepared by HPHT technique

Cu-based and Cu-alloy-based diamond composites were made by high-pressure-high-temperature (HPHT) sintering with the aim of maximizing the thermal conductivity of the composites. Improvements in interfacial bonding strength and thermo-physical properties of the composites were achieved using an atomized copper alloy with minor additions of Co, Cr, B, and Ti. The thermal conductivity (TC) obtained exhibited as high as 688 W·m⁻¹·K⁻¹, but also as low as 325 W·m⁻¹·K⁻¹. A large variation in TC can be rationalized by the discrepancy of diamond-matrix interfacial bonding. It was found from fractography that preferential bonding between diamond and the Cu-alloy matrix occurred only on the diamond {100} faces. EDS analysis and Raman spectra suggested that selective interfacial bonding may be attributed to amorphous carbon increasing the wettability between diamond and the Cu-alloy matrix. Amorphous carbon was found to significantly affect the TC of the composite by interface modification.