A comparison of the silica and Na-K-Ca geothermometers for thermal springs in Utah

The silica and Na-K-Ca chemical geothermometers do not always agree (within 25°C) when applied to hot springs in Utah. Some of the differences can be explained by mixing of hot and cold ground waters. However, the geology of the areas in which the springs arise must also be taken into account.     

温度-浓度耦合变量下甲烷吸收谱线关联分析

采用可调谐激光吸收光谱技术对甲烷体积分数进行检测时,由于测量环境温度变化导致气体吸收谱线线强发生变化,将对测量结果造成不可避免的影响。基于直接吸收光谱法分析不同甲烷体积分数(1.0%～15.0%)在温度290～350 K时吸收谱线特性变化规律,采用多项式回归和共享参数全局线性拟合得到温度-甲烷体积分数耦合变量甲烷光谱吸光度关联式。结果表明:相同温度下,甲烷光谱吸光度A随甲烷体积分数升高而增大;相同甲烷体积分数下,由于总配分函数比值r_Q在甲烷吸收光谱线强随温度变化过程中占据主导作用,r_Q随温度增大的线性降低使得甲烷线强随温度升高而减小;在甲烷体积分数1.0%～15.0%、测量温度290～350 K时,温度-甲烷体积分数耦合变量甲烷光谱吸光度关联式的反演结果相对误差小于1.000%。     

Aluto-langano geothermal field, ethiopian rift valley: physical characteristics and the effects of gas on well performance

This study, which focuses on the Aluto-Langano geothermal field, is part of the ongoing investigations of the geothermal systems in the Ethiopian Rift Valley. Aluto-Langano is a water-dominated gas-rich geothermal field, with a maximum temperature close to 360°C, in the Lakes District region of the Ethiopian Rift Valley. The upflow zone for the system lies along a deep, young NNE trending fault and is characterized by boiling. As a result, the deep upflow zone loses some water as steam and produces a cooler saline shallow aquifer. The high partial pressure of carbon dioxide (about 30 bar in the reservoir) depresses the water table and restricts boiling to deeper levels. The main aquifer for the system is in the Tertiary ignimbrite, which lies below 1400 m. The capacity of the existing wells is close to 7 MW_c; the energy potential of the area is estimated to be between 3000 and 6000 MW_t yr km⁻³, or 10–20 MW_c km⁻³ for over 30 years.     

Correlation between global solar irradiation and air temperature in Asturias, Spain

Since the temperature is probably the most registered meteorological variable, correlation models based on air temperature data are especially interesting to estimate monthly average values of solar irradiation in countries with lack of direct measurements.Previous models that correlate monthly average irradiation on horizontal surfaces with air temperature can be improved by means of dimensional analysis. The procedure makes the influence of the altitude, the distance to sea, and a reference temperature more explicit.The model proposed in the present paper seems to be adequate to the data obtained from meteorological stations supported by official organizations in Asturias, a region with a diverse orography on the northern Spanish coast.Comparisons between model predictions, experimental data, and estimations computed by other methods have shown acceptable results.The methodology has also been applied to other four Spanish stations in order to check the procedure in places with different latitude and climatology.     

Coupled heat and mass transfer by MHD free convection flow along a vertical plate with streamwise temperature and species concentration variations

The problem of steady, laminar, coupled heat and mass transfer by MHD free convective boundary‐layer flow along a vertical flat plate with the combined effects of streamwise sinusoidal variations of both the surface temperature and the species concentration in the presence of Soret and Dufour effects is considered. A suitable set of dimensionless variables is used to transform the governing equations of the problem into a non‐similar form. The resulting non‐similar equations have the property that they reduce to various special cases previously considered in the literature. An adequate and efficient implicit, tri‐diagonal finite difference scheme is employed for the numerical solution of the obtained equations. Various comparisons with previously published work are performed and the results are found to be in excellent agreement. A representative set of numerical results for the velocity, temperature, and concentration profiles as well as the surface shear stress, rate of heat transfer, and the rate of mass transfer is presented graphically for various parametric conditions and is discussed. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21033     

Comparison between polystyrene and fiberglass roof insulation in warm and cold climates

This study clarifies the law of diminishing returns when improving the conservation level of residential buildings by using case studies simulation. It explores the effect of different climates on the decision of selecting the insulation type and thickness. It shows the importance of using the life-cycle cost model on the decision of adding more insulation levels and knowing when to stop. RENCON program was employed to estimate the annual heating and cooling requirements of a 108 m² house. The analysis was carried out for several cases of two types of roof insulation (polystyrene and fiberglass) in two different locations (College Station, Texas and Minneapolis, Minnesota.) R5 was found to be the most cost effective thermal resistance in polystyrene in both locations. In fiberglass, R10 was the most cost effective. It was found that investing money to improve the insulation levels in the cold climate house has better returns than that of the warm climate.     

Relation between concentration and acceptance in solar collectors

The maximum concentration ratio has been derived by Winston for optical systems having an angular acceptance described by a step function. In this paper a more comprehensive relation between maximum concentration ratio and angular acceptance is obtained. This relation is valid for any acceptance function; the proof is based on thermodynamics and is valid for large angles as well.

The total energies collected yearly by concentrators having different acceptance functions are compared.     

Effects of concentration and temperature on the coupled heat and mass transport in liquid mixtures

Using published experimental data on the thermal conductivity, mutual diffusivity, and heats of transport, the degree of coupling between heat and mass flows has been calculated for binary and ternary nonideal liquid mixtures. The binary mixtures consist of two types: the first is six systems of six-to-eight-carbon straight and branched chain alkanes in chloroform and in carbon tetrachloride; and the second is mixtures of carbon tetrachloride with benzene, toluene, 2-propanone, n-hexane, and n-octane. The ternary mixture considered is toluene-chlorobenzene-bromobenzene. The published data are available at 25°C, 30°C and 35°C and ambient pressure. Using the linear nonequilibrium thermodynamics (LNET) and the dissipation-phenomenological equation (DPE) approach, the effects of concentration, temperature, molecular weight, chain-length, solute, solvent, and branching on the degree of coupling are examined. The extent of coupling and the thermal diffusion ratio are expressed in terms of the transport coefficients to obtain a better understanding of the interactions between heat and mass flows in liquid mixtures. It is found that the composition of the heavy component bromobenzene changes the direction and magnitude of the two-flow coupling in the ternary mixture.     

Lattice Boltzmann study of velocity,temperature, and concentration in micro-reactors

The flow, temperature and concentration characteristics in micro-reactors are inherently different from those in macro-reactors. In the former, slip-flow is important. In the case of heterogeneous chemical reaction, jump in the wall temperature and concentration also occur. In this study, we describe the two-dimensional model simulation of the gas velocity, temperature, and concentration in micro-reactors, using lattice Boltzmann methods (LBM). Slip (or jump) in all three transport variables (flow, temperature, and concentration) are considered. The results show two-dimensional profiles of the velocity, temperature, and concentration in the reactors. Due to simultaneous heat and mass transfer, Nusselt number (Nu) and Sherwood number (Sh) are shown to be dependent on a number of variables, including Knudsen number (Kn), transport accommodation coefficients, and the reaction rate. The results in this study assume significance from the perspective of understanding flow and transport characteristics in micro-reactors.     

Correlation between relative sunshine and state of the sky

It is possible to construct a sunshine map referring to a large zone, lacking in a widespread network of recording stations, correlating the relative sunshine with the “state of the sky”, defined by the monthly mean number of the clear, mixed and overcast days, whose data are more largely available. In the correlation here proposed climatological and meteorological factors are introduced in order to express the helioclimatic characteristics of every location. The application to Italy, using the data of the period 1973–1977 provided by the 31 stations of ITAV, has suggested the classification of these stations in seven “helioclimatic groups” characterized by different values of the above factors, mainly representative of the position and typology of the surrounding surfaces and of the atmospheric transparence in a cloudy or cloudless sky. The positive results of the comparison between the experimental and computed relative sunshine values are shown in the tables.     

Hydromagnetic double-diffusive convection in a rectangular enclosure with opposing temperature and concentration gradients

The finite-difference method is used to predict numerically the characteristics of hydromagnetic double-diffusive convective flow of a binary gas mixture in a rectangular enclosure with the upper and lower walls being insulated. Constant temperatures and concentrations are imposed along the left and right walls of the enclosure and a uniform magnetic field is applied in the x-direction. Consistent with what is reported by previous investigators, an oscillation in the flow is observed in the absence of the magnetic field for a specific range of buoyancy ratio values where the Prandtl number Pr=1, the Lewis number Le=2, the thermal Rayleigh number Ra_T=10⁵, and the aspect ratio A=2 for the enclosure. In the presence of the magnetic field, however, no oscillatory behavior is observed. Numerical results are reported for the effect of the heat generation or absorption coefficient and the Hartmann number on the contours of streamline, temperature, concentration and density. In addition, results for the average Nusselt and Sherwood numbers are presented and discussed for various parametric conditions. In this study, the thermal and compositional buoyancy forces are assumed to be opposite.     

颅内动脉瘤的DSA与临床相关性分析

目的　分析评价颅内动脉瘤的脑血管造影与临床相关性。方法　回顾性分析48例颅内动脉瘤患者的脑血管造影表现和临床资料,就其动脉瘤大小、部位、形态、检查方法以及临床表现进行综合分析。结果　颅内动脉瘤临床表现与动脉瘤大小、部位有一定关系,相同或不同部位动脉瘤可产生不同或相同临床症状,旋转DSA技术是常规脑血管造影的有效补充检查手段。结论　1.颅内动脉瘤临床症状与其生长部位及大小有一定相关性,但无明显特异性;2.旋转DSA技术在动脉瘤诊断和治疗中具有极其重要的作用。     

Effect of temperature and iron concentration on the growth and hydrogen production of mixed bacteria

Anaerobic mixed culture acclimated with sucrose was used as inoculum in batch experiments to investigate the effects of various parameters on biological hydrogen production from sucrose. In particular, the effect of the culture temperature has been investigated in detail. The optimum of the iron concentration in the external environment on hydrogen production was also studied at different temperatures. Experimental results show that the hydrogen production ability of the anaerobic bacteria was deeply affected by both culture temperature and iron concentration. Increasing the culture temperature favored the production of hydrogen when it was in the range of 25–40 °C, and high sucrose conversion efficiencies (ca. 98%) were consistently obtained with the mixed bacteria at the same time. While the temperature went on increasing to 45 °C, the hydrogen production was almost inhibited. The optimum concentrations of iron for hydrogen production decreased obviously along with increasing the reactor's temperature. For 25, 35, and 40 °C, the maximum production yield of hydrogen were 356.0, 371.7, and 351.1 ml obtained at the iron concentration of 800, 200, and 25 mg FeSO₄l^-1${\mathrm{l}}^{-1}$, respectively.     

国际市场煤炭与石油价格相关性研究

煤炭消费增长与我国国民经济增长速度关系密切,2011年以来中国连续成为全球最大煤炭进口国,2013年煤炭进口量达到3.3×108t。国内煤炭价格日益受到国际市场煤炭价格的影响,两者之间的联系愈发紧密。而国际市场上煤炭价格与石油价格的波动具有较强的一致性。通过对煤炭价格和石油价格的相互影响机制进行定性分析、相关性分析以及回归分析,证实煤炭价格与石油价格之间存在显著的正相关关系,石油价格上涨或下跌1%则煤炭价格上涨或下跌0.3654%,石油价格的变化可以解释煤炭价格约18%的变动。煤炭与石油互为能源替代品,石油价格通过替代效应和影响宏观经济来直接、间接地影响煤炭价格。过高的石油价格会使消费者选用相对便宜的煤炭,改变市场供求从而拉高煤炭价格,使两者价格趋向于一致。鉴于外界预测2014年全球石油价格将维持在目前的较高水平,考虑到煤炭与石油价格的正相关性,据此判断国际市场煤炭价格也将保持在现有水平,并随石油价格小幅波动。由于国内外煤炭品质及价格存在差异,因此国内煤炭价格将继续承受下行压力,并逐步向国际市场煤价靠拢。     

The impact of cooling on cell temperature and the practical solar concentration limits for photovoltaics

The solar concentration limit for densely packed, high‐concentrated photovoltaic (HCPV) cells was analyzed for a novel two‐phase cooling design. Eight working fluids were examined in the two‐phase cooling analysis: R134a, R11, R113, R114, R123, R141b, water, and ammonia. In addition, the study investigated the concentration limit for mass flow rates ranging from 10^?3 to 1 kg s^?1. Results from this analysis showed that the limits neared 2000 suns for the six organic fluids examined, whereas for water and ammonia, the practical concentration limit reached about 4000 and 6000 suns, respectively. It was concluded that water and ammonia exhibited greater limits of concentration because they possess greater values of sensible and latent heats compared with the organic fluids examined. The results using this two‐phase cooling design were then compared with computational and experimental reference data from other HCPV studies conducted that used cooling mechanisms, such as impinging jets, liquid immersion, and microchannel cooling. Together, the data was compiled and compared with a simplified, one‐dimensional, theoretical model using a generic, hypothetical cooling mechanism for densely packed HCPV cells. The general, practical solar concentration limit was predicted to be approximately 10 000 effective suns for a cooling device with a heat transfer coefficient on the order of 10⁶ W m^?2 K^?1. At this limit, it was determined that the cells' conductive resistance, rather than the external cooling mechanism, becomes the controlling factor for heat removal. Copyright © 2010 John Wiley & Sons, Ltd.