叉流溶液除湿装置全热交换过程的解析解

除湿器是溶液除湿空调系统的重要组成部件。在已有叉流热质交换模型的基础上,通过合理简化给出了空气焓值、溶液等效焓值在除湿器内部的分布情况以及全热效率的解析解。解析解得到的焓值场分布情况与精确数值模型差分离散求解结果进行了比较,解析解得到的全热效率采用叉流除湿装置的实验结果进行验证,解析解与数值求解结果和实验结果很好的符合。该解析解可用于叉流除湿器的设计计算,也为叉流除湿器的场分布优化提供了条件。     

内冷却紧凑式叉流除湿器性能数值模拟与分析

该文提出了一种内冷却紧凑式叉流除湿器，对的该除湿器的除湿以及再生过程建立了热质交换的二维动态数学模型，并运用全隐式差分格式获得了该模型的数值解，对影响该类除湿器工作性能的多种因素及其作用结果进行了分析和对比，为除湿器结构的设计、工作状态点的选择提供了必要的理论依据。结果表明，本文提出的内冷却紧凑式叉流除湿器的性能较普通固定床式除湿器的性能有显著提高。     

转轮除湿器简化模型数值模拟与性能分析

针对转轮除湿器建立了简洁实用的无量纲数学模型,分析了影响该设备除湿效果的无量纲因素;同时,通过对模型进行数值计算,以处理气流出口平均含湿量以及除湿效率为目标函数,定量分析了转轮结构、热质交换性能、运行设置、工作气流入口状态等几个重要方面的参数对除湿效果的影响,为转轮除湿器性能的优化提供必要的理论依据。     

雾化加湿中的液滴蒸发与加湿过程数值分析

将雾化强化加湿技术引入加湿除湿海水淡化系统,建立雾滴与热空气之间的质能守恒及热质传递模型,并在相关假设基础,对雾化加湿器内的雾滴蒸发与空气热湿过程进行分析。分析结果显示,当空气和雾滴初始温度分别为90℃及20℃,气液体积比在45×10~3时,直径为100μm的雾滴在1.29s内实现完全蒸发,此时空气相对湿度为78%,而当气液体积比降低至40×10~3时,液滴直径降至36.7μm时达到气液平衡,此时空气相对湿度为100%。空气热湿过程分析结果显示,气液体积比为25×10~3~40×10~3时,出口空气相对湿度均能达到饱和状态,出口空气温度约为35℃,蒸发率可达70%以上。     

高炉余热驱动鼓风除湿技术实验研究

为了研究液体除湿装置应用于高炉鼓风的可行性。基于某高炉,对采用LiCl溶液脱湿鼓风装置进行理论分析和模化实验。研究表明:除湿效果与溶液液气比、温度、浓度有关。液体除湿液气质量比在1. 4时质交换效率可达38. 1%,为最佳液气质量比;除湿过程中溶液喷淋温度由37. 1℃降至27. 0℃,质交换效率由14. 68%升高至59. 98%,即除湿过程中,溶液温度越低、浓度越高除湿效果越好;全年运行时,浓度保持40%不变,除湿溶液采用冷却塔冷却,月均除湿量均可满足。在模拟最湿热工况时,当空气水蒸气分压力为3 500 Pa时,相对湿度在90%以上,即含湿量为22. 15 g/kg,本实验台除湿结果可达到9. 6 g/kg。     

盐溶液与空气接触的除湿单元模块性能研究

在实验测量的基础上,分析了使用Celdek规整填料和溴化锂除湿溶液的叉流除湿模块的全热效率及除湿效率的影响因素,给出了两个效率的经验关联式,使用该经验关联式计算的全热效率和除湿效率的数值与实验结果的平均偏差分别为6.3%和6.0%。通过与文献中逆流除湿器的实验结果对比,该经验关联式的预测结果与实验结果很好的符合,也可用于预测逆流除湿器的性能。     

太阳能溶液除湿系统再生器的实验研究

结合工程实例进行了太阳能溶液除湿系统除湿溶液再生实验,研究了除湿溶液再生过程的热质交换特性,得到了不同溶液入口参数下再生器内部各测点温度,揭示了不同空气和溶液入口参数对出口溶液浓度的影响和填料对再生器热质交换的影响。文章可为太阳能溶液除湿系统再生器的设计提供依据。     

溶液除湿/再生设备热质交换过程解析解法及其应用

溶液除湿空调系统中最重要的部件是除湿器和再生器。该文在已有热质交换模型基础上，对顺流和逆流两种情况，在一定简化条件下给出了解析解，得出了状态参数沿程分布情况，并与文献中提出的精确数学模型进行了校验。应用此解析解可为除湿器的设计计算和校核计算提供依据．确定绝热除湿过程最佳流量比以及为气液逆流热质交换提供了一种简化计算的方法。     

内冷型液体除湿器数学模型及性能分析

提出了一种内冷型液体除湿器,并对该除湿器的除湿过程建立了热质交换的稳态数学模型.通过与实验结果的比较,发现数值计算结果与实验结果吻合较好,多数数据的偏差都在±10%以内.分析了各参数对除湿性能的影响,为除湿器的结构设计和性能分析提供了理论和应用依据.     

高炉鼓风除湿热质交换性能理论与实验研究

基于Whitman理论以及热质平衡理论建立高炉鼓风除湿器理论模型,设计并搭建1∶200高炉鼓风除湿模化实验台,对高温高湿环境下鼓风除湿性能进行实测。结果表明:除湿量理论值与实验值偏差在0.67%～8.53%内,数据差异小,说明理论模型适应性好,可将此理论模型用于大高炉鼓风除湿器设计计算;在高温高湿环境下,鼓风空气入口干球温度为43.5℃、含湿量为58.54 g/m~3时,溶液喷淋浓度为40%,喷淋温度为21.2℃,气液质量流量比为0.7时,除湿效果最优,除湿后鼓风空气含湿量降低44.79 g/m~3,鼓风湿度低至13.75 g/m~3,高炉鼓风风温可提升268.74℃。     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

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.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

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.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法，这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

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.     

Economie d'énergie en trigénération

Trigeneration is defined as the production of three useful forms of energy—heat, cold and power—from a primary source of energy such as natural gas or oil. For instance, trigeneration systems typically produce electrical power via a reciprocating engine or gas turbine and recover a large percentage of the heat energy retained in the lubricating oil, exhaust gas and coolant water systems to maximize the utilization of the primary fuel. The heat produced can be totally or partially used to fuel absorption refrigerators. Therefore, trigeneration systems enjoy an inherently high efficiency and have the potential to significantly reduce the energy-related operation costs of facilities. In this paper, we describe a model of characterization of trigeneration systems trough the condition of primary energy saving and the quality index, compared to the separate production of heat, cold and power. The study highlights the importance of the choice of the separate production reference system on the level of primary energy saving and emissions reduction.     

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.     

Mineralogical characterization of the intraseam layers of Lofoi lignite deposits in Florina basin (western Makedonia,northwest Greece)

The mineralogical composition of intraseam layers from Lofoi lignite deposits (northwest Greece) is the subject of the present study. The samples were examined by means of X-ray diffraction (XRD), thermo-gravimetric (TG/DTG) and differential thermal analysis (DTA), and Fourier transform infrared (FT-IR) spectrometry. The clay minerals prevail in most samples, with illite-muscovite being the dominant phase, and kaolinite and chlorite being the other major clay components. No smectite was found. Quartz and feldspars, dominate in two cases. The studied materials are characterized as clays to clayey sands, showing significant similarities with the intraseam layers of the adjacent Achlada lignite deposits.