四种土壤对铯的吸附热力学研究

近些年来,土壤铯(Cs)污染是人们所关注的问题。本文采用静态吸附法,比较研究了中国四种典型土壤在不同温度下(288K、298K、308K)对溶液中Cs吸附的热力学特征,结果表明四种土壤对Cs均具有一定的吸附能力,且在任何温度下,其吸附量为黑土>紫色土>褐土>红壤。随着温度的提高,每种土壤对Cs的吸附量较高。四种土壤对Cs的吸附等温线均可以用Freundlich模型进行拟合。土壤有机质含量和季节温度变化可能对土壤吸附Cs产生显著影响。     

van’tHoff方程及相关问题的讨论

van’t Hoff方程是描述化学平衡常数与温度之间关系的方程,且有\"化学反应等压方程\"和\"化学反应等容方程\"之说。目前教材对于这些方程的推导不严格,甚至不正确,对于\"等压\"和\"等容\"的含义也没有解释,造成了该方程使用上存在困难,出现许多错误的结论,使得在推导活化能与反应热关系时出现混乱。针对此问题,从化学势是状态函数入手,证明了摩尔反应吉布斯函数也是状态函数,并以此为基础,利用严谨的数学和热力学概念,推出了van’t Hoff方程。结果表明,van’t Hoff方程的2种形式,即所谓的\"化学反应等压方程\"和\"化学反应等容方程\",其使用条件与等压和等容无关,只是一种习惯叫法而已。在此基础上,严格导出了理想气体化学反应的Arrhenius活化能和恒压反应热及恒容反应热之间的关系。研究明确了任意反应和理想气体反应van’Hoff方程的形式和使用条件,对人们正确认识和利用热力学领域理想气体反应活化能和反应热的关系打下了基础。     

Thermodynamics and process analysis for future economic scenarios

Economists are increasingly interested in forecasting future costs and benefits of policies for dealing with materials/energy fluxes, polluting emissions and environmental impacts on various scales, from sectoral to global. Computable general equilibrium (CGE) models are currently popular because they project demand and industrial structure into the future, along an equilibrium path. But they are applicable only to the extent that structural changes occur in or near equilibrium, independent of radical technological (or social) change. The alternative tool for analyzing economic implications of scenario assumptions is to use Leontief-type Input-Output (I-O) models. I-O models are unable to endogenize structural shifts (changing I-O coefficients). However, this can be a virtue when considering radical rather than incremental shifts. Postulated I-O tables can be used independently to check the internal consistency of scenarios. Or I-O models can be used to generate scenarios by linking them to econometric macro-drivers (which can, in principle, be CGE models). Explicit process analysis can be integrated, in principle, with I-O models. This hybrid scheme provides a natural means of satisfying physical constraints, especially the first and second laws of thermodynamics. This is important, to avoid constructing scenarios based on physically impossible processes. Process analysis is really the only available tool for constructing physically plausible alternative future I-O tables, and generating materials/energy and waste emissions coefficients. Explicit process analysis also helps avoid several problems characteristic of pure CGE or I-O models, viz. (1) aggregation errors (2) inability to handle arbitrary combinations of co-product and co-input relationships and (3) inability to reflect certain non-linearities such as internal feedback loops.     

Money as Social Exergy

Synopsis It has been proposed that open thermodynamic systems will act to dissipate available energy gradients by self-organizing into coherent structures that, with time, evolve and develop into nested hierarchies – panarchies – that adapt to internal and external changes according to a characteristic adaptive cycle. This paper seeks to apply these ideas in the purely societal realm by investigating the role of money in economic systems. Money represents the value embodied in goods; a value that is separate from the exact nature of those goods. We suggest that money thereby liberates the ‘free value’ of economic desire and that this free value has properties analogous to energy. The result is the self-organization of structures and systems (‘econosystems’) that dissipate this ‘free value’. Econosystems act at different scales, and nested levels of econosystems form a panarchy, having effects that can be observed. In particular, it appears that money facilitates the creation of relationships between econosystem actors, increasing the connectedness of the econosystems that envelop those actors. We have identified a phenomenon whereby freed social value (i.e. money) can aggregate, or pool, at a larger econosystem scale in structures such as banks. These pools act as gradients that actors at the neighborhood scale can exploit for self-organization in the econosystem. Thus, econosystem actors appear to be freed from thermodynamic constraints by using money as a means of self-organization. However, because of these pools of aggregated social exergy, connectedness is increased at the larger scale of the econosystem. The potential consequence of this dynamic is that money may act to push larger scale econosystems toward a state of heightened vulnerability to collapse, while freeing smaller scale actors from apparent constraints. In this way, we propose that money acts to skew information feedback loops between econosystem actors and larger scale structures such as economies and ecosystems.      

Comments

This paper is a first step toward building a Packaging Recycling Index (PRI) for the commercial packaging industry. This index has two parts; the first part refers to the percentage of "recovered material" in the construction of commercial packages. The second part refers to the percentage of the packaging that may be recycled by the consumer post use. The purpose of the PRI is to construct a simple label that would indicate the "greenness" of commercial packaging by considering total thermodynamic throughput. Building on the work of Frederick (1995) this work attempts to correct societal misunderstandings about product usage by looking at entropy rather than price as a measure of efficiency. This paper uses packaging data from Kell Container in Chippewa Falls, Wisconsin to develop the initial index as described above.     

二氧化碳加氢合成甲醇模拟研究

采用ASPEN PLUS11.1流程模拟软件,模拟了二氧化碳和氢气为原料合成甲醇反应过程,研究了了原料配比、压力、温度可能对反应的影响,以及对催化剂开发应该考虑的问题。为催化剂的开发及工艺设计提供一定的依据。     

回热式地热双循环发电系统工质选择

为了解决不同工质地热双循环发电系统热力学性能差异较大的问题,采用EES(engineering equation solver)软件对1 MW回热式地热双循环发电系统进行了分析,研究地热源温度为90～150 ℃时,不同工质发电系统的吨水净发电量、净效率、膨胀比等热力学参数的变化规律,通过对比以上参数获得综合性能最优的工质,使双循环发电系统的热力学性能达到最优。结果表明：在冷热源温度等参数恒定条件下,系统吨水净发电量随工质蒸发温度的增加存在一个最大值;系统最大吨水净发电量、净效率和膨胀比随地热源温度的升高而增大,工质质量流量的变化趋势则相反;相同冷热源参数条件下,R134a的吨水净发电量最大,R245fa的净效率和膨胀比最大,在地热源温度为110 ℃时,工质R134a的吨水净发电量为3.035 （kW·h）/t,工质R245fa的净效率为6.24%、膨胀比为3.146;综合对比工质的系统热力学性能参数和工质物性,工质选用R245fa。研究成果可为回热式地热双循环发电系统的参数设计提供指导。     

过冷器前节流中间补气空气源热泵性能模拟研究

为了解决空气源热泵在低温工况下性能衰减、排气温度过高和制热不足等问题,以过冷器前节流中间补气空气源热泵循环系统为研究对象,建立了以带补气单螺杆压缩机为热力系的循环理论数学模型,给出了中间平衡补气压力的计算流程,并对系统参数进行了模拟计算。结果表明：与不补气压缩系统相比,补气对系统COP、制热量的提升具有明显作用;压缩机的补气口越靠近吸气结束位置,系统性能参数越好;在蒸发温度-25 ℃情况下,补气与过冷器过冷侧液体出口的温差降低6 ℃,压力损失系数从0.42增加到0.82,COP提升了14%左右。因此,在能够保证过冷器正常运行的情况下,尽可能减小补气口与过冷器过冷侧液体出口的温差,尽量减少补气过程中的压力损失,有利于补气热泵系统性能的提升。研究结果可为过冷器空气源热泵系统的设计提供理论支持。     

浅析温差式水泵设计与应用

在遵循热力学定律前提下,设计温差式水泵,将部分废热用于做功,达到节能减排的目的。文章将阐述温差式水泵的工作原理及应用情况。     

工程热力学课程教学改革与实践

以培养厚基础、宽口径、强能力、高素质的高级专门人才为目标,对建筑环境与设备工程专业的工程热力学课程内容进行重组与优化,采用对比式教学等方法,利用多媒体等技术手段,本课程教学改革取得了较好的效果。