天然气水合物开采技术研究现状与展望

天然气水合物是一种世界公认的最具潜力的清洁能源,目前我国对水合物的勘探开采研究正进入关键突破阶段,南海泥质粉砂天然气水合物成藏机理与赋存规律尚不明晰,开采过程水合物分解相变机制与安全、高效技术仍需进一步探明。本文重点介绍了包括降压开采、固态流化开采等在内的天然气水合物开采技术的研究与应用现状,并通过分析天然气水合物开采技术存在的问题给出了相应的发展建议。研究建议,推动天然气水合物、深部油气等多气源立体开采基础研究和重大工程;强化技术融合,推进理论与实践协同并进;推进天然气水合物中试尺度实验和多场耦合的数值模拟大科学平台建设;建立健全天然气水合物的相关标准等措施,以提升我国天然气水合物开采技术的研发水平和技术成熟度,以期早日实现天然气水合物的大规模商业化开发,服务于我国的能源安全战略。

基于TDTR技术水合物热导率测量方法

四氢呋喃水合物(THF)是典形的笼形水合物,目前有关其热导率的报道较少,且都存在测量样品不是单一相、测量过程水合物发生分解等问题。采用基于飞秒脉冲激光的时域热反射法(TDTR)测量THF热导率。根据样品常温下是流体的特点,设计了可同时适用样品制备及TDTR测量的温控台,实现THF热导率非接触原位测量。获得THF热导率为0.6W/(m·K),Al/THF界面热导为90.3MW/(m^2·K)。该实验结果有助于理解并完善固体水合物微观导热机理,明晰水分子笼子和客体分子的耦合关系。

我国林草机械业发展现状、问题及对策--基于对565位林草业专家的调研

林草机械现代化是林草业实现高质量发展的重要途径。系统掌握林草机械业发展现状,针对其存在问题提出政策建议具有重要意义。文中以565位林草业专家学者作为调研对象,采用李克特5级量表设计问卷,基于调研结果开展定性与定量分析。结果表明:我国林草机械业总体发展水平评价得分均处于中等偏下水平,各类细分产品评价得分也多数处于中等及中下水平。其成因在于行业特性、企业自身问题、政策支持不足等因素,其中缺乏专业人才队伍支持、缺乏社会资本关注、名优企业品牌建设力度与政策支持不足等因素的分值较高。针对上述问题提出加大行业投入力度、完善林草机械企业生产体系、完善林草机械业科技研发体系、完善林草机械业应用及推广体系等建议。

中国林业机械用户满意度调查与分析

以个人、公司、林场与合作社四类林业机械用户作为研究对象,通过在线调查获取一手数据,采用有序Logit模型、联立表格和描述性统计相结合的方法,分析林业机械用户对购置补贴、使用和售后服务的满意度及其成因。结果表明:个人、公司、林场与合作社用户对林业机械购置补贴比较满意,对林业机械使用基本满意,对林业机械售后服务满意度一般;林业机械价格、效益和用户需求对林业机械购置补贴、使用和售后服务的满意度均具有显著的正向影响;用户类型对林业机械使用满意度和售后服务满意度均无显著影响,公司用户相对于林场用户对购置补贴的满意度更低。为了提高用户对于林业机械的满意度,建议进一步加大林业机械资金补贴力度、注重提高林业机械产品品质和使用效率、完善林业机械社会化服务体系。

In-situ observation for formation and dissociation of carbon dioxide hydrate in porous media by magnetic resonance imaging

The study of formation and dissociation of CO 2 hydrate in porous media was characterized by magnetic resonance imaging (MRI) system in in situ conditions. This work simulated porous media by using glass beads of uniform size. The growth and dissociation habit of CO2 hydrate was observed under different temperature and pressure conditions. The induction time and the hydrate saturation during the growth and dissociation process in different sizes of porous media were obtained by using the MRI signal intensity. The results indicate that hydrate growth rate and the induction time are affected by the size of porous media, pressure, and degree of supercooling. There are three hydrate growth stages, i.e., initial growth stage, rapid growth stage and steady stage. In this study,the CO2 hydrate forms preferentially at the surface of vessel and then gradually grows inward. The hydrate tends to cement the glass beads together and occupies the pore gradually. As the hydrate decomposes gradually, the dissociation rate increases to the maximum and then decreases to zero.

Forced Convection Heat Transfer in Porous Structure: Effect of Morphology on Pressure Drop and Heat Transfer Coefficient

A light-weight structure with sufficient mechanical strength and heat transfer performance is increasingly required for some thermal management issues.The porous structure with the skeleton supporting the ambient stress and the pores holding the flowing fluid is considered very promising,attracting significant scientific and industrial interest over the past few decades.However,due to complicated morphology of the porous matrices and thereby various performance of the pressure drop and heat transfer coefficients (HTC),the comprehensive comparison and evaluation between different structures are largely unclear.In this work,recent researches on the efforts of forced convection heat transfer in light-weight porous structure are reviewed;special interest is placed in the open-cell foam,lattice-frame,structured packed bed,and wire-woven structures.Their experimental apparatus,morphological of the porous structures,effect of morphology on pressure drop and HTC,and further applications are discussed.The new method which measure morphology accurately should be paid more attention to develop more accuracy correlation.Also,the most research focused on low Reynolds number and existing structure,while very few researchers investigated the property of forced convection heat transfer in high velocity region and developed new porous structure.

An In-Situ MRI Method for Quantifying Temperature Changes during Crystal Hydrate Growths in Porous Medium

Given the complexity of the thermo-hydro-chemically coupled phase transition process of hydrates,real-time in-situ observations are required.Thermometry maps are particularly essential in analyzing the heat transfer process during the growth and dissociation of crystal hydrates.In this study,we present the temporally and spatially resolved thermometry of the formation of tetrahydrofuran hydrates based on the temperature dependence of the chemical shift of the water proton.Images of temperature changes were synchronously obtained using a 9.4 T^(1)H magnetic resonance imaging(MRI)system to predict the saturation level of the aqueous solution,phases of the solid hydrates,and the positive temperature anomaly of the exothermic reaction.It was observed that variations in the MRI signal decreased while the temperature rise differed significantly in space and time.The results predicted in this study could have significant implications in optimizing the phase transition process of gas hydrates.

基于促进大学生就业的单位选择评价指标体系研究

本文运用层次分析法(AHP)构建了基于促进大学生就业的单位选择评价指标体系,确定了9个较为关键的评价指标及其权重值。分析各项指标对单位选择评价的影响程度,高校学生就业部门可据此对校园招聘企业进行综合评价。