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911.
The typical shape of a capillary-pressure curve is either convex (e.g., Brooks–Corey model) or S-shaped (e.g., van Genuchten model). It is not universally agreed which model reflects natural rocks better. The difference between the two models lies in the representation of the capillary entry pressure. This difference does not lead to significantly different simulation results for modeling CO2 sequestration in aquifers without considering CO2 dissolution. However, we observe that the van-Genuchten-type capillary-pressure model accelerates CO2 solubility trapping significantly compared with the Brooks–Corey-type model. We also show that the simulation results are very sensitive to the slope of the van-Genuchten-type curve around the entry-pressure region. For the representative examples we study, the differences can be so large as to have complete dissolution of the CO2 plume versus persistence of over 50% of the plume over a 5000-year period.The cause of such sensitivity to the capillary-pressure model is studied. Particularly, we focus on how the entry pressure is represented in each model. We examine the mass-transfer processes under gravity-capillary equilibrium, molecular diffusion, convective mixing, and in the presence of small-scale heterogeneities. Laboratory measurement of capillary-pressure curves and some important implementation issues of capillary-pressure models in numerical simulators are also discussed. Most CO2 sequestration simulations in the literature employ one of the two capillary-pressure models. It is important to recognize that these two representations lead to very different predictions of long-term CO2 sequestration. 相似文献
912.
This paper presents a field study conducted in northwest Turkey and characterizes the NH3 concentration and emission measured in summer season from three chicken farms. The influence of environmental conditions on NH3 concentration and emission was also investigated in this study. Ammonia concentration, temperature, relative humidity and airflow rate were continuously recorded for four sequential days. The environmental conditions were measured using a multifunction temperature and humidity‐meter with a hot wire probe. Portable multiple gas detectors with electro‐chemical sensors were used to measure NH3 concentration. The NH3 emission rates for houses were calculated by multiplying simultaneously measured NH3 concentrations and air flow rates. The average daily mean (ADM) house concentrations of house 1 (H1), house 2 (H2), and house 3 (H3) were measured as 4.43, 3.71, and 6.20 ppm, respectively. NH3 concentration was inversely proportional to temperature (r = ?0.279), relative humidity (r = ?0.063) and airflow rate (r = ?0.554) for all monitored houses. The ADM house NH3 emission was 135 g/(h house) for H1, 255 g/(h house) for H2, and 117 g/(h house) for H3. The combined average emission rate in this study (0.26 g/(d bird)) was lower than the emission rate measured in chicken farms in the USA. However, our results were comparable to rates calculated in European studies because house design, ventilation system and bird diet applied in Turkish chicken farms are very similar to those employed in European countries. The NH3 emissions were significantly correlated to NH3 concentrations (r = 0.45, p ≤ 0.001) and airflow rates (r = 0.97, p ≤ 0.001). A clear diurnal pattern was obtained for NH3 concentrations rather than NH3 emissions at the end of the study. 相似文献
913.
The emission of large amounts of solvent vapors with exhaust air from industrial production into the environment is a serious problem. In Germany, industry‐sector‐specific threshold values are applied and technical measures for pollution reduction are required. Different techniques for exhaust air cleaning are in use but still posing problems concerning costs and reliability. For these reasons, the development of processes for exhaust air treatment is the subject of the current research. A new concept for exhaust air cleaning is introduced that combines absorption of a solvent vapor by an organic fluid and a subsequent adsorption by a molecular sieve placed in the absorber. It was managed to close the loops of solvent recovery and sorbents regeneration. In laboratory‐scale experiments it was possible to reduce an initial ethylacetate pollution of 800 mg/m3 or 349 mg C/m3 below the limit value of 75 mg C/m3 over 60 h duration. Thermogravimetric measurements assisted to define optimum conditions for solvent recovery at 180°C from the molecular sieve. One unexpected positive finding was the considerable increase in the solvent release in the presence of the absorption fluid while adsorption isotherms revealed first insight into this process. 相似文献
914.
利用浙江省义乌市2015—2019年逐小时气象观测数据(相对湿度、风速、地气温差、能见度)和空气质量指数(Air Quality Index, AQI)数据, 分析了义乌地区低能见度天气(观测能见度lt; 10 km)的分布特征和气象要素条件。利用长短期记忆神经网络(Long Short Term Memory Neural Network, LSTM)模型对逐小时能见度进行模拟, 分别对比了观测能见度作为输入变量与否的模拟效果; 根据义乌地区低能见度天气条件的特征, 将模拟时段分为三个时期(11月至翌年2月, 3—6月, 7—10月), 对比了分时期模拟的效果; 以及评估了模型的预报步长。结果表明: 高湿、高污染、气温高于地温和低风速是义乌地区低能见度天气的主要特征。LSTM模型对单站能见度有较好的模拟效果, 当输入参数中加入历史观测能见度时, 能大幅提高模拟准确度, 日均能见度模拟结果均方根误差RMSE=0.63 km, 平均绝对误差MAE=0.51 km, 拟合优度R2=0.99;分时期进行模拟能得到更精准的模拟结果。本研究中选用的输入要素在冬季(11月至翌年2月)模拟效果最好, RMSE=2.35 km, MAE=1.46 km, 低能见度均方根误差RMSE_10 km=1.81 km, 低能见度平均绝对误差MAE_10 km=1.13 km, R2=0.83; 3—6月的模拟中, 输入变量中不加AQI模拟效果更好, 这意味着3—6月义乌地区的低能见度天气以雾天气为主导, 加入过多变量并不一定能提高模型准确度; 随着预报步长增大, 模型预报效果变差, 预测步长等于3 h, R2=0.71, 预测结果已不具备实际应用意义。 相似文献
915.
以某边坡工程压力分散型预预应力锚索的张拉试验为基础,介绍了压力分散型预应力锚索工作机理及张拉试验过程,并对应力损失、预应力筋的伸长量及桩身变形进行分析和初步探讨。 相似文献
916.
GCTS空心圆柱扭剪仪是研究土体在循环荷载下的主应力轴旋转的理想仪器。如何使用GCTS空心圆柱扭剪仪对软土空心试样进行反压饱和才能使后续试验结果更精确,探究了以GCTS空心圆柱扭剪仪为试验平台,对空心试样进行了反压饱和的试验方法。总结了空心扭剪仪反压饱和的3种加压方式:手动加压、自动加压和连续加压方式。通过一些试验探究了每种加压方式所对应的合理性参数。确定了适合吹填土的压差为15kPa。确定了孔压稳定的标准为:如果孔压在1min内的变化值小于围压和反压之间压力差的5%,则认为孔压稳定。 相似文献
917.
地层压力变化是导致孔内情况复杂化的关键因素,地层压力预测是钻探施工中泥浆设计和事故防范的重要手段,合理预知地层压力情况有助于最大限度地解决深孔钻探中的复杂问题[1]。近年来,地层应力预测技术在国内外得到了广泛探讨,而传统的水压致裂地层压力测量方法仍然是简单实用的手段之一。通过云南某矿区复杂地层深孔钻探工程中的应用实例,验证了地层压力预测在绳索取心钻探工程上的合理性和可行性。 相似文献
918.
919.
920.