用于集中供热的冷凝热回收火用分析

用火用平衡分析法对西山热电的原集中供热系统和冷凝热回收后的集中供热系统进行了火用流分析。两者对比表明,冷凝热回收用于集中供热是实现节能减排的一条有效途径。

700 ℃超超临界燃煤发电机组热力系统设计及分析

根据MC(Master Cycle)系统的框架结构,设计了基于MC的1 000MW、700℃超超临界燃煤发电机组热力系统,确定了相关的热力参数,同时设计了基于常规热力系统结构的对比系统.将这2个热力系统划分为锅炉、汽轮机、发电机、凝汽器和管道共5个单元,采用分析法计算了各单元的损、损系数和效率指标.结果表明:采用MC系统机组的热经济性比常规热力系统机组的热经济性高,主要体现在MC系统机组中汽轮机系统的热经济性较高,尤其是MC系统机组中汽轮机系统的中压缸、第3～6级加热器具有更高的热经济性.

Performance improvement in stepped solar still modified by sponge layer

In this paper,the experimental investigation on the performance improvement of conventional stepped solar still is conducted.The steps are covered by the porous material to improve the performance of the conventional device and increase the evaporation rate.All the parameters,including the temperature on the glass surface,the water temperature inside the evaporation zone,and the amount of water produced in both conventional and modified stepped solar stills are measured and compared.The efficiency of two devices and their exergy efficiency have been calculated.Finally,the economic analysis of both devices has been done to check the economic feasibility of the modified device.The amount of freshwater generated during one day was 2244.4 and 3076.2 mL/m^(2),respectively for the conventional and modified stepped solar stills.As a result,the amount of water produced in one day by modified stepped solar still is 35.5% more than the conventional one.Also,the costs for the conventional and modified stepped solar stills have been calculated as 0.0359 and 0.029$/(L·m^(-2)),respectively.

以最小为目标的氢气分配网络优化

优化氢气分配网络,合理利用氢气资源,对炼化企业的节能降耗、降低生产成本具有重要意义。在氢气分配网络中,除了氢气的消耗,最主要的能耗就是压缩气体时所消耗的功。为了将氢气的消耗和压缩功的消耗从节约能源的角度统一优化,提出以'基准'为基础对氢气分配网络模型进行优化设计,即将新氢用量和压缩过程的功耗都转换成耗,以总的消耗量作为衡量氢网络优劣的基准。同时利用网络结构调优策略,以有效地减少压缩机的数目,保证了系统的能量性能和经济效益。通过一个精炼厂实例的成功应用,证实了此种方法的有效性。

区域供冷系统的动态逐时能分析与分析

基于热力学第一定律和第二定律,建立了常规区域供冷系统、天然水源区域供冷系统以及空气源区域供冷系统共三种区域供冷系统的分析通用模型;并基于上海某中央商业中心,用TRNSYS软件建立了三种区域供冷系统的动态逐时能分析与分析模拟模型;分析了三种区域供冷系统的损失、效率以及系统能效;提出了宜采用天然水源区域供冷系统的天然水源至冷水机组间的管路长度限值的确定方法。结果发现,天然水源区域供冷系统的效最高,其次为空气源区域供冷系统,常规区域供冷系统的最小,其值分别为16.52%,15.05%以及12.12%;其单位冷量的损失分别为0.289,0.323以及0.414。另外,天然水源区域供冷系统的能效最高,其次为常规区域供冷系统,空气源区域供冷系统的最小,其系统电力能效依次为2.52、2.32以及2.2。

环保型多元混合工质在小型低温装置上的应用

采用低GWP和零ODP的环保型多元混合工质(R50,R1150,R290,R600a,N2),对回热式单级压缩节流制冷循环进行系统设计与优化。在带预冷的回热式单级压缩节流制冷循环中,利用NIST-REFPROP8.0物性分析软件,对混合工质热力性质进行模拟计算。通过热力学分析和2种优选配比下系统的主要性能参数(压缩机吸排气温度、压力,低温桶内温度)对比试验测试,得到了组分最佳配比N2∶CH4∶C2H4∶C3H8∶i C4H10=32∶20∶12∶20∶16,系统运行75min左右可达到最低制冷温度170K左右,实现带预冷的环保型多元混合工质在小型低温装置系统的稳定运行。

基于热利用率的原油管输优化运行研究

在区分可避免、不可避免热损失的基础上,提出了热利用率的定义,用以评价原油管道不同运行工况下的耗状况,能够真正体现对热的有效利用程度。以大庆某输油管道为例,计算原油管道在不同运行条件下的热利用率,研究其随管径、原油输量、出站温度及保温层厚度等影响因素的变化情况,并采用正交实验分析法比较四种因素对管道热利用率的影响程度。研究结果表明,四种因素对热利用率影响程度由大到小依次是管径、原油输量、出站温度、保温层厚度,可为原油管道优化运行提供一定理论依据。

低温乙烯再液化流程的改进与优化

针对一种广泛应用的复叠式低温乙烯闪蒸气(BOG)再液化装置进行流程改进,利用Aspen HYSYS软件分析了再液化循环中间压力pE2、制冷循环中间压力pR2和制冷循环蒸发压力pR1对现有流程和改进流程COP、效率的影响,获得现有流程和改进流程的最优工况,并分别对它们的最优工况进行了热力学分析及损失计算。结果表明:再液化3 055 kg/h的乙烯BOG,改进流程在最优工况下的压缩机耗功可比现有流程减小10.47%,相应的COP和效率比现有流程提高了11.68%;改进流程最优工况下的pE2和pR2分别比现有流程低290 k Pa、50 k Pa,即两个闪蒸罐可在更低的工作压力下达到更高的COP及效率,系统安全性提升。

Determination and Analysis of Heavy Metals Contents in Edible Fungi

[Objective] This study aimed to understand the status of heavy metal contamination in edible fungi, thereby providing some scientific basis for the safety of edible fungi. [Method] The heavy metal contamination status in four kinds of edible fungi, i.e., shitake mushroom, mushroom, agaric and needle mushroom, from Guiyang City and Tongren City, Guizhou Province was evaluated by flame atomic absorption spectrophotometry. [Result] Cu, Mn, Cr and Ni were detected in the four kinds of edible fungi from Guiyang and Tongren; the Cr contents in the four kinds of edible fungi from Guiyang and Tongren all exceeded the national standard, and the Cu contents all met the national standard; The Ni contents in agaric and needle mushroom from Guiyang, and the Ni contents in the four kinds of edible fungi from Tongren, all exceeded the national standard; the enrichment capacity of the four kinds of edible fungi for the four kinds of heavy metal elements ranked as Cu＇s Mn＇s Cr＇s Ni＇s; among the four kinds of edible fungi, mushroom showed the strongest enrichment capacity for the four kinds of heavy metal elements. [Conclusion] The heavy metal contamination in the four kinds of edible fungi was all severe in Guiyang and Tongren, especially in Tongren. There has been currently no national standard for Mn content in edible fungi, which needs to be developed as soon as possible.

2D multi-scale hybrid optimization method for geophysical inversion and its application

Local and global optimization methods are widely used in geophysical inversion but each has its own advantages and disadvantages. The combination of the two methods will make it possible to overcome their weaknesses. Based on the simulated annealing genetic algorithm （SAGA） and the simplex algorithm, an efficient and robust 2-D nonlinear method for seismic travel-time inversion is presented in this paper. First we do a global search over a large range by SAGA and then do a rapid local search using the simplex method. A multi-scale tomography method is adopted in order to reduce non-uniqueness. The velocity field is divided into different spatial scales and velocities at the grid nodes are taken as unknown parameters. The model is parameterized by a bi-cubic spline function. The finite-difference method is used to solve the forward problem while the hybrid method combining multi-scale SAGA and simplex algorithms is applied to the inverse problem. The algorithm has been applied to a numerical test and a travel-time perturbation test using an anomalous low-velocity body. For a practical example, it is used in the study of upper crustal velocity structure of the A＇nyemaqen suture zone at the north-east edge of the Qinghai-Tibet Plateau. The model test and practical application both prove that the method is effective and robust.

STUDY ON SEAMLESS AND MULTILEVEL VPN

The virtual private network (VPN) system, which is one of the construction methods for private networks over the Internet, is gaining prominence. VPNs are currently used for corporate networks to support end to end communications. But if they are applied to private networks for distributed departments in organizations, some problems should be concerned, such as low efficiency of packet transfer and nonsupport of unsymmetrical VPN connections. At first this paper analyzes the limitations of VPN used in the environment of multiple subnets, and then brings up a distributed module of VPN with low cost, high packet transfer efficiency and powerful functions of user authentication and access control.

Exergy Analysis and Retrofitting of Natural Gas-based Acetylene Process

This article presents an acetylene production process by partial oxidation/combustion of natural gas. The thermodynamic performance and exergy analysis in the process are investigated using the flow-sheeting program Aspen Plus. The results indicate that the most important destruction of exergy is found to occur in the reactor and water quenching scrubber, amounting to 8.23% and 10.39%, respectively, of the entire system. Based on the results of thermodynamic and exergy analysis, the acetylene reactor has been retrofitted. The improvement ratios of molar 02 to CH4 and molar CO to CN4 are 0.65 and 0.20, respectively. An improvement of the acetylene production system is proposed. Adopting the improvement operation conditions and using oil to realize the reaction heat recovery, the feedstock of natural gas is reduced by 9.88% and the exergy loss in the retrofitting process is decreased by 19.71% compared to the original process.

Effects of working parameters on gasoline engine exergy balance

To improve the energy utilization efficiency of internal combustion （IC） engine, exergy analysis was conducted on a passenger car gasoline engine. According to the thermodynamic theory of IC engine, in-cylinder exergy balance model was built. The working processes of gasoline engine were simulated by using the GT-power. In this way, the required parameters were calculated and then gasoline engine exergy balance was obtained by programming on computer. On this basis, the influences of various parameters on exergy balance were analyzed. Results show that, the proportions of various forms of exergy in gasoline engine from high to low are irreversible loss, effective work, exhaust gas exergy and heat transfer exergy. Effective exergy proportion fluctuates with cylinder volumetric efficiency at full load, while it always increases with break mean effective pressure （BMEP） at part load. Exhaust gas exergy proportion is more sensitive to speed, and it increases with speed increasing except at the highest speed. The lower proportion of heat transfer exergy appears at high speed and high load. Irreversible loss is mainly influenced by load. At part load, higher BMEP results in lower proportion of irreversible loss; at full load, the proportion of irreversible loss changes little except at the highest speed.

Coupling effect of evaporation and condensation processes of organic Rankine cycle for geothermal power generation improvement

Organic Rankine cycle(ORC)is widely used for the low grade geothermal power generation.However,a large amount of irreversible loss results in poor technical and economic performance due to its poor matching between the heat source/sink and the working medium in the condenser and the evaporator.The condensing temperature,cooling water temperature difference and pinch point temperature difference are often fixed according to engineering experience.In order to optimize the ORC system comprehensively,the coupling effect of evaporation and condensation process was proposed in this paper.Based on the laws of thermodynamics,the energy analysis,exergy analysis and entropy analysis were adopted to investigate the ORC performance including net output power,thermal efficiency,exergy efficiency,thermal conductivity,irreversible loss,etc.,using geothermal water at a temperature of 120℃as the heat source and isobutane as the working fluid.The results show that there exists a pair of optimal evaporating temperature and condensing temperatures to maximize the system performance.The net power output and the system comprehensive performance achieve their highest values at the same evaporating temperature,but the system comprehensive performance corresponds to a lower condensing temperature than the net power output.

CENOZOIC VOLCANISM AND GEOTHERMAL RESOURCES IN NORTHEAST CHINA

This paper is concentrated on Cenozoic volcanism and geothermal resources in Northeast China. There are a lot of Cenozoic volcanoes, a large area of volcanic rocks, a large number of active faults and rich geothermal resources in Northeast China. The time and space characteristics of Cenozoic volcanism and the space distribution characters of hot springs and high geothermal flux regions in Northeast China are described and discussed on the basis of geological, geothermal, drilling and volcanological data. It is revealed that the hot springs and high geothermal flux regions are related to the Cenozoic volcanism, rifting and faulting in Northeast China. It is especially emphasized that the hot springs and high geothermal anomaly areas are controlled by active deep faults. It is proposed that the Cenozoic volcanism regions, rift basins, active fault belts, activated plate suture zones and large earthquake occurrence points are the best areas for prospecting geothermal resources. The geothermal resources in younger volcanic zones are richer than those in older volcanic belts. The hot springs and active or activated faults might be a very good clue for looking for geothermal resources.

Exergy Analysis of Single and Multi-Step Thermal Processes

The present paper introduces the concepts of exergy and treats it applications to analysis of the gain in exergy efficiency between one-step and multi-step thermal processes. The analysis, which is carried out with the Excel-based SEPE program, is exemplified with the comparison between single-step and two-steps heat pump setup for providing heat to a floor heating system and for domestic hot water. The paper discusses the use of the concept of exergy efficiency as a measure of success for design of a heat pump application and how the use of information on exergy destruction and temperature levels in different parts of the system add a new perspective to the analysis and the evaluation of the system performance. The paper shows how this information can be used to improve the system configuration and also the operation of the system for given boundary conditions. This is especially useful when the energy from the low temperature sources can be utilized at different temperature or quality levels such as for space heating and domestic hot water.

Live Memory Acquisition through FireWire

Although FireWire-based memory acquisition method has been introduced for several years, the methodologies are not discussed in detail and still lack of practical tools. Besides, the existing method is not working stably when dealing with different versions of Windows. In this paper, we try to compare different memory acquisition methods and discuss their virtues and disadvantages. Then, the methodologies of FireWire-based memory acquisition are discussed. Finally, we give a practical implementation of FireWire-based acquisition tool that can work well with different versions of Windows without causing BSoD problems.

Suspension mechanism and application of sand-suspended slurry for coalmine fire prevention

North and west China has abundant coal resources, however, such resources make these regions prone to serious mine fire disasters. Although the copious sand and fly ash resources found in these areas can be used as fire-fighting materials, conventional grouting is expensive because of water shortage and loess particles. A new compound material(i.e., a sand-suspended colloid), which comprises a mineral inorganic gel and an organic polymer, is developed in the current study to improve the quality of sand injection and reduce water wastage when grouting. The new material can steadily suspend the sand, through the addition of a small amount of colloid yielding steady sand-suspended slurry. The process of producing the slurry is convenient and quick, overcoming the shortage of sand-suspending thickeners which need heat and are difficult to produce. The space work model based on the theory of the double-electric layer is established to study the suspended mechanism of the solid particles in the sand-suspended colloid.The dispersion effect of the sand-suspended colloid is demonstrated by the incorporation of the electrostatic effect by the double-electric layer and the steric hindrance effect on the sand particles, ensuring the stability of the colloid system and the steady suspension of sand particles in the sand-suspended colloid.Mechanical analysis indicates that the sand is suspended steadily under the condition that the rock sand particles stress on the lower part of the fluid is less than the yield stress of the colloid. Finally, the fireprevention technology of sand suspension was applied and tested in the Daliuta Coal Mine, achieving successful results.

Numerical and experimental analysis of quenching process for cam manufacturing

In order to obtain satisfactory mechanical properties for the cam used in high-power ship diesel engines, a new quenching technology was proposed by designing a two-stage quenching process with an alkaline bath as the quenching medium. To demonstrate the effectiveness of the proposed new quenching technology, both numerical analysis and experimental study were performed. The new quenching technology was analyzed using finite element method. The combined effects of the temperature, stress and microstructure fields were investigated considering nonlinear material properties. Finally, an experimental study was performed to verify the effectiveness of the proposed new quenching technology. The numerical results show that internal stress is affected by both thermal stress and transformation stress. In addition, the direction of the internal stress is changed several times due to thermal interaction and microstructure evolution during the quenching process. The experimental results show that the proposed new quenching technology significantly improves the mechanical properties and microstructures of the cam. The tensile strength, the impact resistance and the hardness value of the cam by the proposed new quenching technology are improved by 4.3%, 8.9% and 3.5% compared with those by the traditional quenching technology. Moreover, the residual stress and cam shape deformation are reduced by 40.0% and 48.9% respectively for the cam manufactured by the new quenching technology.

Research on Genesis of Pyrite near the Permian-Triassic Boundary in Meishan,Zhejiang,China

The content and crystal forms of pyrite and sulfur isotope composition of pyrite sulfur as well as its vertical distribution near the Permian-Triassic （P/T） boundary in the Meishan section, Changxing county, Zhejiang province, China were studied using geological, petrological, mineralogical and geochemical methods （techniques）. The result showed that the genesis of abundant pyrites in bed 24e2 at the uppermost part of the Changxing Formation in the Me- ishan section may be related to volcanic activity. In bed 24e2 of the Meishan section, pyrite has its highest content of 1.84% and the sulfur isotope composition has the highest 834S value at ＋2.2%0 which is very similar to that of the average value of volcanic gas, There are some volcanic products such as β-quartz, siliceous cylinders and siliceous spherules which coexisted with pyrites in beds 24e2 and 24f. It can be concluded that a large quantity of volcanic ash fell into the South China Sea and was incorporated into marine sediments during the formation of limestone at the uppermost part of the Changxing Formation. The volcanic eruption with massive amounts of H2S and SO2 gas at the end of the Permian period resulted in the enrichment of HES in the South China Sea areas, The reaction of H2S with reactive iron minerals formed the mass of abundant pyrites.