Experimental and numerical study on tube-side flow and heat transfer characteristics of superheated vapor flow in catalyst-filled LH2 spiral wound heat exchanger

High energy consumption is considered to be one of the most persistent problems in liquid hydrogen (LH₂) plants. The combination of heat exchanger and ortho-para (O–P) hydrogen conversion has attracted considerable attention as a cutting-edge technology to reduce energy consumption. The flow and heat transfer characteristics of O–P hydrogen conversion catalyst-filled spiral wound heat exchanger (SWHE) were investigated in this study in two steps. In the first step, pressure-drop experiments were performed in a tube filled with porous media. The results indicated that the pressure drop was overestimated when using Ergun's equation. Therefore, a new empirical pressure-drop correlation for a channel filled with O–P catalyst was formulated. Subsequently, a novel heat transfer model was established based on this correlation for further numerical simulations. The distributions of the temperature, pressure, and para hydrogen content in a catalyst-filled tube were determined. In addition, the influence of the flow rate on the heat exchange coefficient and outlet para hydrogen was clarified; it was found that, with an increase in the flow rate, the heat exchange coefficient increased, whereas the outlet para hydrogen content decreased. At a flow rate of 0.5 m³/h, the para hydrogen content increased by 44% after hydrogen flowed through the channel filled with the O–P catalyst. Furthermore, a prediction model for the para hydrogen content with a flow rate range of 0–1.5 m³/h was derived. This study provides promising theoretical evidence for the engineering application of SWHEs filled with O–P catalysts in large-scale hydrogen liquefaction units.     

风积粉细砂隧道施工中的注浆加固技术

神朔铁路杏树峁隧道采用低压渗入性注浆方法，在风积粉细砂地层中压注改性水玻璃浆液，解决了隧道施工中的超前支护、注浆矽化加固的可注性，浆液选材配比及注浆工艺待技术问题，有效地控制了漏砂、坍塌和结构过量沉降等问题的发生。本文根据现场实践，应用注浆固结理论，对风积粉细砂注浆加固后的强度和稳定性进行了分析。     

Efficacy of recycled sand or organic solids as bedding sources for lactating cows housed in freestalls

Our objective was to compare the composition of bedding materials and manure, cow welfare and hygiene assessments, measures of milk production and quality, and incidence of mastitis during a 3-yr trial with lactating Holstein cows housed in a freestall barn containing 4 identical pens with 32 freestalls/pen. Bedding systems evaluated included deep-bedded organic manure solids (DBOS), shallow-bedded manure solids spread over mattresses (MAT), deep-bedded recycled sand (RSA), and deep-bedded new sand (NSA). The experiment was designed as a 4 × 4 Latin square with 4 bedding systems and 4 experimental periods, but was terminated after 3 yr following discussions with the consulting statistician; therefore, data were analyzed as an incomplete Latin square. A total of n = 734 mostly primiparous cows (n = 725 primiparous, n = 9 multiparous; 224 to 267 cows/yr) were enrolled in the trial. Before placement in freestalls, organic solids (OS) exhibited lower concentrations of dry matter (36.5 vs. 94.3%), and greater concentrations of volatile solids, C, N, NH₄-N, P, water-extractable P, K, and S compared with RSA or NSA. Cow comfort index was greater for sand-bedded systems compared with those using OS (88.4 vs. 82.8%). Cows bedded in systems using OS (DBOS and MAT) exhibited greater mean hock scores (1 = no swelling, no hair loss; 2 = no swelling, bald area on hock) than those bedded in sand (1.25 vs. 1.04), but this effect was entirely associated with use of mattresses (MAT), which differed sharply from DBOS (1.42 vs. 1.07). Generally, hygiene scores for legs, flanks, and udders were numerically similar for DBOS, NSA, and RSA bedding systems, and differences between bedding systems were associated entirely with MAT, yielding detectable contrasts between MAT and DBOS for legs (2.94 vs. 2.20), flanks (2.34 vs. 1.68), and udders (1.83 vs. 1.38). No significant contrast comparing bedding systems was detected for measures of milk production or quality. Documented cases of clinical mastitis requiring treatment ranged from a low rate of 7.4 cases/yr for RSA to a high of 23.1 cases/yr for DBOS, based on a mean enrollment of 60.7 to 63.0 cows/treatment per yr. Cows bedded with OS exhibited a greater incidence of mastitis than those bedded with sand (19.0 vs. 8.4 cases/yr), but no differences were observed for comparisons within individual bedding-material types. Collectively, these results generally favored use of sand-bedding materials over systems using OS.     

Hydrocarbon potential of Permian coals of South Karanpura Coalfield,Jharkhand, India

The present study investigates the hydrocarbon generative potential of the coal seams of Barka Sayal Area of South Karanpura Coalfield, India, using petrological and geochemical characteristics. These coals are vitrinite rich followed by liptinite and inertinite. Rank wise these are sub-bituminous ‘A’ to high volatile bituminous ‘C’ and fall in the early catagenesis stage of evolution. The presence of Type III kerogen and high hydrogen index value indicates excellent gaseous hydrocarbon generative potential, but low T_max suggests a characteristic of immature source rock. The calculated high conversion (%) and sufficient oil yield (%) justifies the suitability of these coals for liquefaction processes.     

Quantitative analysis of alkanoate and condensed arenes in the extracts from direct coal liquefaction residue by ultrasonication-assisted solvent extraction using alcohols

Shenmu-Fugu coal liquefaction residue (SFCLR) was ultrasonically extracted with methanol, ethanol, and isopropanol, respectively. Abundant of condensed arenes (CAs) were identified in the extracts using gas chromatography/mass spectrometer (GC/MS) by quantitative analysis, besides some alkanes and heteroatom-containing compounds. The most dominant CAs is benzo[ghi]perylene with its yield of 71.77 mg/g in isopropanol extract based on GC/MS analysis. Series of alkanoates were identified in the extracts from SFCLR with high yields. Interestingly, methyl alkanoates were identified in each of the three extracts, while ethyl and isopropyl alkanoates were only identified in the ethanol and isopropanol extracts, respectively. Accordingly, we presume that transesterification of methyl alkanoates with ethanol or isopropanol occurs during the ultrasonication-assisted solvent extraction.     

砂石加工系统中筛分楼的动力有限元分析

筛分楼是筛分设备的承重结构,筛分设备工作时不可避免地将动力荷载传递给筛分楼,使其产生位移作用。基于大型有限元商业软件ANSYS,采用动力时程分析方法分析了某水电站砂石加工系统中筛分楼的动力响应。结果表明,振动筛正常工作时不会与筛分楼产生低频共振,筛分楼在振动筛长期作用下,水平位移和垂直位移均在控制标准内,说明设计的筛分楼是安全的。     

粉质粘土液化层中采用夯扩桩失败原因的剖析

本文叙述了在饱和粉质粘土中进行夯扩桩施工所带来的工程质量问题;分析了因土的液化造成了桩质量事故的原因;介绍了碎石桩的应用效果.可供在类似地质条件下的工程进行桩基设计和施工时参考.     

The composition analysis of coal-derived light oil

The composition of coal-derived light oil (IBP-220 °C) was separated into 5 fractions by atmospheric distillation and analyzed by gas chromatography/mass spectrometry (GC/MS). The light oil was made at 0.1 t/d coal direct liquefaction bench scale unit (BSU) at China Coal Research Institute (CCRI). Six groups of organics, including acyclic hydrocarbon, alicyclic hydrocarbon, aromatics, phenols, polynuclear aromatics and heterocyclics, were found and 80 compounds were tentatively identified in total. Alicyclic hydrocarbon is the main component of the light oil compared to other groups whether in relative mass percentage or the number of compounds in group. The predominant oxygen-contained compound is phenols, and the nitrogen-containing compound is pyridine. No sulfur-containing compound is detected. Supported by the National Basic Reserch Program of China (2004CB217605)     

强夯在吹填粉细砂中的应用

该文介绍了某工程利用强夯加固大面积吹填土的地基处理实践。根据强夯试验区施工前后现场观测结果以及原位测试结果,探讨了强夯应用于饱和吹填土地基的加固机理及效果,为类似地基处理提供了参考依据。     

石英尾矿尾砂综合利用研究综述

石英尾矿尾砂是宝贵的矿产资源,我国年排放量上千万吨,资源化利用已成为必然趋势。石英尾矿尾砂的化学成分相对稳定,其在水泥、玻璃、墙体材料、微晶玻璃、釉质材料、硅微粉、电工电子封装材料、化工材料、工业填料等方面均有不同程度的利用,具有广阔的发展前景。