利用工程热力学原理对商品价值量进行分析、计算的探讨

热力学是研究一个体系的热、能量等量的科学,整个社会的劳动人员、物资、生产设备等一起构成了一个经济整体,从热力学的角度,这个整体是一个体系。在这个体系中不可避免地涉及有关能量之类的问题,比如劳动人员的劳动付出,实质就是一个做功和能量转移的过程,因此有理由认为热力学的一些基本定律也适用于经济体系。本文的主要思想是用热力学原理来分析和解决经济管理问题。首先作者从思考马克思的科学社会主义的热力学依据出发,得出“社会生产力不断进步的热力学本质是经济体系的熵（即无序程度）在减小“这一结论;然后又对商品的价值量的热力学本质进行思考,认为商品价值量的实质是该商品相对于原料的有效程度的增加,在热力学上就是从原料到生产产品的过程中,由劳动者向商品中转移的熵流的大小。     

热力学定律太阳能

物质的分子运动是一种无规则运动,它永远不会停止,只与温度有关。气体作用在容纳它的器壁上的压力,是大量气体分子和器壁碰撞的平均效果。气体的温度决定于大量气体分子的平均动能。由于引进了能、能的传递和转换的概念,并确立了能的转换所遵循的基本规律,我们不必详细考察分子运动的过程,就能描述物质的行为。热力学是从能量观点研究物质运动过程的科学。热力学定律是热力学的基础,它是由实验结果概括而确立的。由这些定律推出的许多结论,都与实验结果     

高碱灰渣烧结反应的化学热力学平衡计算

针对高碱灰渣烧结特性进行化学热力学平衡反应计算,并与试验结果进行了比较.计算采用FactSage 5.2计算软件中的Equilib模型.计算结果显示高碱灰渣的强烧结特性主要是由大量黝方石、蓝方石、霞石、无水芒硝等较低熔点的钠基复合盐造成.计算结果与试验分析物相基本一致,表明化学热力学反应平衡分析方法是研究灰渣烧结特性的有效手段.     

碱土金属碳酸盐热分解反应贮存太阳能的初步研究

本文对利用碱土金属碳酸盐的分解/合成反应贮存太阳能,在热力学和动力学方面进行了研究,利用热力学计算确定了这些反应的转向温度,并由实验得到的热重曲线计算了反应级数、半衰期和活化能。最后,导出了反应速度常数和温度之间的关系式。     

1986年中国工程热物理学会热机气动热力学学术会议简况

由中国工程热物理学会举办的中国工程热物理学会热机气动热力学1986年学术会议于9月19日至22日在四川峨嵋西南交通大学科技中心举行。学会理事长、气动热力学组组长吴仲华同志等全国各地代表77人参加了会议。共宣读论     

蒸馏系统有效能分析

蒸馏是一种特别消耗大量能量的分离操作,因此在蒸馏系统的设计和操作中对有效能的利用给予适当考虑极为重要。如同其他单元操作,由蒸馏塔及其有关热交换器网络组成的蒸馏系统的热分析,向来是根据以热力学第一定律为基础的能量平衡考虑能量的利能来完成的;然而,鉴于必须同时从能量观点定性的分析这些系统,也考虑了以熵及有效能平衡和热力学第二定律为基础的分析。     

论合成煤气的冷煤气效率对IGCC供电效率的影响

本文从热力学第一定律和热力学第二定律的角度，论述了在ＩＧＣＣ电站中，由气化炉产生的合成煤气的冷煤气效率对于供电效率ηＮｃｃ的影响关系。由此从理论上证明了：提高以发电为目的的气化炉之冷煤气效率的必要性。     

结构热力学原理

本文给出了结构热力学的相关定义,探讨了结构热力学研究的对象。方向及方法。明确了热力系集和热力学载体的概念。揭示了结构热力学的发展方向和应用背景。本文还从结构热力学的观点,提出了热力学参数不对等原理,从而为结构热力学奠定了选取其结构特征参数的基础。     

用"热力学熵振荡原理"指导政府选择经济宏观调控的最佳程度

热力学是研究一个体系的热、能量等量的科学,整个社会的劳动人员、物资、生产设备等一起构成了一个经济整体。从热力学的角度,这个整体是一个体系。在这个体系中不可避免地涉及有关能量之类的问题,比如劳动人员的劳动付出,实质就是一个做功和能量转移的过程,因此有理由认为热力学的一些基本定律也适用于经济体系。本文的主要思想是用热力学原理来分析和解决经济管理问题。作者从思考马克思的科学社会主义的热力学依据出发,得出“社会生产力不断进步的热力学本质是经济体系的熵（即无序程度）在减小”,运用“熵振荡原理”探讨了政府对经济进行宏观调控的最佳程度的选择这一问题。     

熵与(火用)及(火用)分析与(火用)传递

能量与能质寓于同一的客观属体--能,又分别表征能的不同的客观属性.热力学可划分为基础热力学和应用热力学两大类,相应地形成了分别以熵和(火用)为核心的两个热力学参数框架体系.(火用)理论的直接应用是(火用)分析法;其扩展应用是与经济学结合产生的热经济学,与传输学结合产生(火用)传递理论.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Decomposition of limestone in a solar reactor

The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m² parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO₂ emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.     

Biohydrogen production by Anabaena sp. PCC 7120 wild-type and mutants under different conditions: Light, nickel, propane, carbon dioxide and nitrogen

Increasing awareness of environmental problems caused by the current use of fossil fuel-based energy, has led to the search for alternatives. Hydrogen is a good alternative and the cyanobacterium Anabaena sp. PCC 7120 is naturally able to produce molecular hydrogen, photosynthetically from water and light. However, this H₂ is rapidly consumed by the uptake hydrogenase.This study evaluated the hydrogen production of Anabaena sp. PCC 7120 wild-type and mutants: hupL⁻ (deficient in the uptake hydrogenase), hoxH⁻ (deficient in the bidirectional hydrogenase) and hupL⁻/hoxH⁻ (deficient in both hydrogenases) on several experimental conditions, such as gas atmosphere (argon and propane with or without N₂ and/or CO₂ addition), light intensity (54 and 152 ??Em⁻²s⁻¹), light regime (continuous and light/dark cycles 16 h/8 h) and nickel concentrations in the culture medium.In every assay, the hupL⁻ and hupL⁻/hoxH⁻ mutants stood out over wild-type cells and the hoxH⁻ mutant. Nevertheless, the hupL⁻ mutant showed the best hydrogen production except in an argon atmosphere under 16 h light/8 h dark cycles at 54 ??Em⁻²s⁻¹ in the light period, with 1 ??M of NiCl₂ supplementation in the culture medium, and under a propane atmosphere.In all strains, higher light intensity leads to higher hydrogen production and if there is a daily 1% of CO₂ addition in the gas atmosphere, hydrogen production could increase 5.8 times, related to the great increase in heterocysts differentiation (5 times more, approximately), whereas nickel supplementation in the culture medium was not shown to increase hydrogen production. The daily incorporation of 1% of CO₂ plus 1% of N₂ did not affect positively hydrogen production rate.     

Investigation of the thermodynamic and kinetic properties of La–Fe–B system hydrogen-storage alloys

La–Fe–B hydrogen-storage alloys were prepared using a vacuum induction-quenching furnace with a rotating copper wheel. The thermodynamic and kinetic properties of the La–Fe–B hydrogen-storage alloys were investigated in this work. The P–C–I curves of the La–Fe–B alloys were measured over a H₂ pressure range of 10⁻³ MPa to 2.0 MPa at temperatures of 313, 328, 343 and 353 K. The P–C–I curves revealed that the maximum hydrogen-storage capacity of the alloys exceeded 1.23 wt% at a pressure of approximately 1.0 MPa and temperature of 313 K. The standard enthalpy of formation ΔH and standard entropy of formation ΔS for the alloys' hydrides, obtained according to the van't Hoff equation, were consistent with their application as anode materials in alkaline media. The alloys also exhibited good absorption/desorption kinetics at room temperature.     

The Solar Office in context

The goal of sustainability in buildings can only hope to be realised if buildings are designed to both conserve and generate energy. The Solar Office at Doxford International is designed to minimise the use of energy while its external fabric is designed to replace such energy that is used. The recently completed building is now subject of a comprehensive monitoring programme. The programme covers both the performance of the 73 kW_p photovoltaic installation and the environmental conditions within the building as a whole. Hour by hour findings are posted on a dedicated web site. Photovoltaics could have the same impact on building form and layout as the invention of the passenger lift at the end of the last century.     

Hydrogen recovery from the photovoltaic electroflocculation-flotation process for harvesting Chlorella pyrenoidosa microalgae

In this paper, an integrated process using photovoltaic power to harvest microalgae by electro-flocculation (EF) and hydrogen recovery is presented. It is mainly favorable in regions with high solar radiation. The electro-flocculation efficiency (EFE) of Chlorella pyrenoidosa microalgae was investigated using various types of electrodes (aluminum, iron, zinc, copper and a non-sacrificial electrode of carbon). The best results regarding the EFE, and biomass contamination were achieved with aluminum and carbon electrodes where the electrical energy demand of the process for harvesting 1 kg of algae biomass was 0.28 and 0.34 kWh, respectively, while the energy yield of harvested hydrogen was 0.052 and 0.005 kWh kg^?1, respectively. The highest harvesting efficiency of 95.83 ± 0.87% was obtained with the aluminum electrode.The experimental hydrogen yields obtained were comparable with those calculated from theory. With a low net energy demand, microalgae EF may be a useful and low-cost technology.     

Electrochemical behavior of Mg–Li,Mg–Li–Al and Mg–Li–Al–Ce in sodium chloride solution

Mg–Li, Mg–Li–Al and Mg–Li–Al–Ce alloys were prepared and their electrochemical behavior in 0.7 M NaCl solutions was investigated by means of potentiodynamic polarization, potentiostatic current–time and electrochemical impedance spectroscopy measurements as well as by scanning electron microscopy examination. The effect of gallium oxide as an electrolyte additive on the potentiostatic discharge performance of these magnesium alloys was studied. The discharge activities and utilization efficiencies of these alloys increase in the order: Mg–Li < Mg–Li–Al < Mg–Li–Al–Ce, both in the absence and presence of Ga₂O₃. These alloys are more active than commercial magnesium alloy AZ31. The addition of Ga₂O₃ into NaCl electrolyte solution improved the discharging currents of the alloys by more than 4%, and enhanced the utilization efficiencies of the alloys by more than 6%. It also shortened the transition time for the discharge current to reach to a steady value. Electrochemical impedance spectroscopy measurements showed that the polarization resistance of the alloys decreases in the following order: Mg–Li > Mg–Li–Al > Mg–Li–Al–Ce. Mg–Li–Al–Ce exhibited the best performance in term of activity, utilization efficiency and activation time.     

Temperature dependence of the enthalpy of formation of metal hydrides characterized by an excess volume

A universal framework to calculate the temperature dependence of the excess enthalpy present in regions characterized by an excess volume is calculated for metals and metal hydrides. At high temperatures, the different contributions from the pressure–volume, heat capacity, entropy and work associated with the thermal expansion are studied separately and their magnitudes and signs are compared. It is found that the pressure–volume contribution opposes and dominates the other three contributions at both high temperature and excess volume, and it is thus found that this contribution becomes the leading temperature dependent contribution to the enthalpy of a material. The conditions under which a temperature change will reduce the enthalpy of formation of metal hydrides are also given and the Mg/MgH₂ system is studied as an example. Excluding the heat capacity contribution, an increase in temperature tends to offset the effect of the excess volume on the enthalpy of formation. It is also demonstrated that the impact of temperature will be more favorable to a reduction of the enthalpy of formation if a large fraction of the metal hydride is in a state of small excess volume compared to a small fraction of the hydride in a state of high excess volume.     

The effect of electrode infiltration on the performance of tubular solid oxide fuel cells under electrolysis and fuel cell modes

The electrochemical performance of two different anode supported tubular cells (50:50 wt% NiO:YSZ (yttria stabilized zirconia) or 34:66 vol.% Ni:YSZ) as the fuel electrode and YSZ as the electrolyte) under SOFC (solid oxide fuel cell) and SOEC (solid oxide electrolysis cell) modes were studied in this research. LSM (La_0.80Sr_0.20MnO_3−δ) was infiltrated into a thin porous YSZ layer to form the oxygen electrode of both cells and, in addition, SDC (Sm_0.2Ce_0.8O_1.9) was infiltrated into the fuel electrode of one of the cells. The microstructure of the infiltrated fuel cells showed a suitable distribution of fine LSM and SDC particles (50–100 nm) near the interface of electrodes and electrolyte and throughout the bulk of the electrodes. The results show that SDC infiltration not only enhances the electrochemical reaction in SOFC mode but improves the performance even more in SOEC mode. In addition, LSM infiltrated electrodes also boost the SOEC performance in comparison with standard LSM–YSZ composite electrodes, due to the well-dispersed LSM nanoparticles (favouring the electrochemical reactions) within the YSZ porous matrix.     

Tailored solar optics for maximal optical tolerance and concentration

Recently identified fundamental classes of dual-mirror double-tailored nonimaging optics have the potential to satisfy the pragmatic exigencies of concentrator photovoltaics. Via a comprehensive survey of their parameter space, including raytrace verification, we identify champion high-concentration high-efficiency designs that offer unprecedented optical tolerance (i.e., sensitivity to off-axis orientation) - a pivotal figure-of-merit with a basic bound that depends on concentration, exit angle, and effective solar angular radius. For comparison, results for the best corresponding dual-mirror aplanatic concentrators are also presented.