Pressure drop and heat transfer of arrays of in-line circular blocks on the wall of parallel channel

Pressure drop and heat transfer of arrays of in-line circular blocks on the wall of a parallel channel are measured. Diameter and height of the blocks are 40 and 18 mm, respectively, while pitches of the blocks are varied. The effects of the number of lines and rows and other factors on pressure drop and heat transfer are investigated. The pressure loss coefficient ζ is the sum of the pressure drop across three regions, the inlet, intermediate and outlet regions, and is formulated as an empirical equation that agrees with experimental data to within ±10%. Average heat transfer coefficient of the first row of blocks is 10% lower than that of the second row. Coefficients of the first 5 rows Nu_mi, are approximated to within ±10% by Nu_mi=0.118(Re/β)^0.75, where β is the opening ratio. The average Nusselt number of the second to fifth rows is also correlated to fan power, P_w, to within 5% by Nu_ave=190P_w^0.25, where P_w=ΔPU_mA₀,ΔP is the pressure difference, U_m is the mean velocity and A₀ is the cross-sectional area of the duct. Finally, the Nusselt number is represented by a non-dimensional expression as Nu_ave=0.134(ζ^1/3Re)^0.75.     

Optical evaluation and analysis of an internal low-concentrated evacuated tube heat pipe solar collector for powering solar air-conditioning systems

An optical evaluation and analysis of an internal low-concentrating evacuated tube heat pipe solar collector designed to enhance the collection of solar radiation for medium temperature applications is presented in this paper. The internal low-concentrating evacuated tube heat pipe solar collector was designed with an acceptance angle of 20° given a geometrical concentration ratio of 2.92. The truncation of the upper part of the reflector giving a geometrical concentration ratio of 1.95 was carried and enabled the internal low-concentrating evacuated tube heat pipe collector to be enclosed by a borosilicate glass tube with 100 mm and 93 mm outer and inner diameters, respectively. Ray trace analysis at different transverse angles determines optical efficiencies, related optical losses and flux distribution on the absorber of the internal low-concentrating evacuated tube heat pipe solar collector. A detailed two dimensional ray trace techniques considering only the direct insolation component predicated overall ray’s acceptance of 93.72% and optical efficiency of 79.13% from transverse angles of 0° to 20°.     

电力送变电系统节能技术探究

随着中国经济的快速发展,人民生活水平的不断提高,对能源特别是电力能源的需求越来越大。但是,粗放型的经济发展方式使中国的资源环境状况不容乐观。中国要想摆脱粗放型经济发展方式,实现经济生态自然协调可持续的科学发展,除了要提高公民的节能环保意识外,还要通过发展技术从根本上降低能源消耗和减少污染,技术是推动人类进步的重要动力。就电力送变电系统节能降耗技术方面进行了浅析,并提出建议和措施。     

大亚湾核电站调试锅炉工程电气系统的设计及运行

简要介绍大亚湾核电站调试锅炉工程配电系统一次及二次接线的设计、电气设备选择及其布置。经过调试运行证明,该系统满足了调试锅炉的要求,并已顺利完成了核电站1号主汽轮发电机组及其辅机在各种工况下的试运行试验。     

On the use of reactive power as an endogenous variable in short‐term load forecasting

In the last decades, short‐term load forecasting(STLF) has been the object of particular attention in the power systems field. STLF has been applied almost exclusively to the generation sector, based on variables, which are transversal to most models. Among the most significant variables we can find load, expressed as active power (MW), as well as exogenous variables, such as weather and economy‐related ones; although the latter are applied in larger forecasting horizons than STLF. In this paper, the application of STLF to the distribution sector is suggested including inductive reactive power as a forecasting endogenous variable. The inclusion of this additional variable is mainly due to the evidence that correlations between load and weather variables are tenuous, due to the mild climate of the actual case‐study system and the consequent feeble penetration of electrical heating ventilation and air conditioning loads. Artificial neural networks (ANN) have been chosen as the forecasting methodology, with standard feed forward back propagation algorithm, because it is a largely used method with generally considered satisfactory results. Usually the input vector to ANN applied to load forecasting is defined in a discretionary way, mainly based on experience, on engineering judgement criteria and on concern about the ANN dimension, always taking into consideration the apparent (or actually evaluated) correlations within the available data. The approach referred in the paper includes pre‐processing the data in order to influence the composition of the input vector in such a way as to reduce the margin of discretion in its definition. A relative entropy analysis has been performed to the time series of each variable. The paper also includes an illustrative case study. Copyright © 2003 John Wiley & Sons, Ltd.     

奥里油特性及其发电应用分析

针对我国即将成为奥里油的重要用户这一客观形势，介绍了奥里油的特性及其在电厂中应用的优缺点，并指出了在应用中须注意的几个技术问题，最后介绍了奥里油燃烧后烟气的净化和废物的处理问题。     

煤矿供配电系统设计节能技术探析

目前煤矿企业经济形势严峻,节约能源已成为矿井降低经济成本的重要措施。主要介绍了在煤矿供配电系统设计时应当注意的几点节能措施,并提出了煤矿企业应加强供配电节能管理的建议,对矿井节能具有一定的借鉴意义。     

Wind power potential and characteristic analysis of the Pearl River Delta region, China

Wind power potentials of the Pearl River Delta (PRD) region have been statistically analyzed based on the hourly measured wind speed data in four islands. The hourly and monthly wind speed and wind power density are assessed to have remarkable variations, and the Weibull distribution function has been derived from the available data with its two parameters identified. The wind power and operating possibilities of these locations have been studied based on the Weibull function. The wind power potentials of these sites were found to be encouraging; however, the wind power at different site varies significantly, so attention should be paid to the wind conditions as well as the site terrains in choosing the wind farm sites.     

The price of independents: an analysis of the independent power sector in England and Wales

This paper presents a focused analysis of the role of entrants into the electricity generation market since privatisation. It examines subsequent developments in the market and in the industry's structure and performance. The analysis draws heavily upon new information gained from telephone interviews with many of those involved with the so-called “independent power producers” (IPPs), as well as information in the existing literature. Our key finding is that IPP entry has not significantly increased competition and has adversely affected the future viability of the electricity system. We attribute these failures to the very policies that encouraged the initial entry of the IPPs.     

浅析10kV配电房高低压开关选择与保护

根据配电房高低压开关不同类型选择问题,通过对10 kV配电房的高低压开关的性能以及数据的相互比较,同时根据在实际运用中所反应出的情况,阐述了10 kV配电房高低压开关及选择方面需注意的事项并提出合理建议,为配电房的设备选型打下基础,也为中国电网建设做出应有的贡献。     

Measurement of the clamping pressure distribution in polymer electrolyte fuel cells using piezoresistive sensor arrays and digital image correlation techniques

A combined method for the simultaneous measurement of the clamping pressure distribution and endplates deformation in polymer electrolyte fuel cells (PEFC) is presented. The proposed approach, which allows overcoming some important limitations associated with the use of conventional pre-scaled pressure films, is used to investigate the correlation between the actual pressure distribution on the membrane electrode assembly (MEA), the endplate out-of-plane deformation and the applied clamping torque, for two single fuel cells assembled with either copper or aluminium/copper endplates. Results proved that, in point-load design PEFCs, both pressure magnitude and distribution are affected by endplates deformation and thickness mismatching between the sealing gasket and the MEA. Moreover, while the average pressure on the MEA displays a slight increase (+25%) as the clamping torque is raised from 5 to 10 N m, it increases monotonically on the sealing gasket, with local peaks that exceed the saturation level of the sensor array (20.7 MPa). A dimensionless uniformity index has been introduced to assess the uniformity of the pressure distribution, allowing an easy comparison of different fuel cell assembly configurations. The proposed methodology might assist the design of next-generation fuel cells or could be used as a powerful validation tool for detailed finite element models. It can also be applied to study other kind of fuel cells and batteries as well.     

Prediction for the burnout of pulverized coal in a coal-fired power plant by combining proximate analysis,coal petrography,and pulverized-coal size distribution

Highly changeable coal quality, low combustion efficiency, and huge consumption of coal are the three common problems facing most of China’s coal-fired power plants. Proper prediction for the coal burnout in power boilers has important economic and environmental significance. By combining critical factors in proximate analysis, coal petrography, and the size distribution of pulverized coal, this article aims to propose a comprehensive method to predict the burnout of pulverized coal in power boilers. Results show that: (a) volatile content and calorific value are the two most important factors in proximate analysis, (b) the most important factors in coal petrography are the relative content of reactive and unreactive macerals and the mean and standard deviation of vitrinite reflectance, and (c) the 90–200-μm-size fraction is a particularly important factor in the size distribution of pulverized coal. Compared with any parameters or indices based on one of the three aspects in proximate analysis, coal petrography, and pulverized-coal size distribution, the synthetic index into which these critical factors are combined has a better significant correlation with coal burnout.     

On the development of an International Curriculum on Hydrogen Safety Engineering and its implementation into educational programmes

The present paper provides an overview of the development of an International Curriculum on Hydrogen Safety Engineering and its implementation into new educational programmes. The curriculum is being developed as part of the educational and training activities of the European Network of Excellence “Safety of Hydrogen as an Energy Carrier” (HySafe). It has a modular structure consisting of five basic, six fundamental and four applied modules. The reasons for this particular structure are explained. To accelerate the development of teaching materials and their implementation in training/educational programmes, an annual European Summer School on Hydrogen Safety will be held (the first Summer School was from 15–24 August 2006, Belfast, UK), where leading experts deliver keynote lectures to an audience of researchers on topics covering the state-of-the-art in hydrogen safety science and engineering. The establishment of a postgraduate certificate course in hydrogen safety engineering at the University of Ulster (starting in January 2007) as a first step in the development of a worldwide system of hydrogen safety education and training is described.     

Preparation of a stable nanocomposite phase change material (NCPCM) using sodium stearoyl lactylate (SSL) as the surfactant and evaluation of its stability using image analysis

In this study, a new method was proposed for the preparation of a stable Al₂O₃-paraffin nanocomposite phase change material (NCPCM). Sodium stearoyl lactylate (SSL) was used as the surfactant to improve the dispersion of Al₂O₃ nanoparticles (2.5, 5, 7.5, and 10 wt.%) in paraffin with a SSL/Al₂O₃ mass ratio of 1:3.5. After preparation, one group of the samples was placed in an incubator at a temperature of 60 °C for one week to evaluate its stability during the time elapsed. The other was left alternately in two incubators, one at 60 ^°C and the other at 25 ^°C over time intervals of 1 h in order to evaluate the stability of the sample after given numbers of melting/freezing cycles. This latter treatment has been seldom ever reported elsewhere. For NCPCM stability evaluation, the samples were broken into two parts equal in volume and the change ratios of surface layer Al³⁺ concentration are determined. Also, image analysis is used for evaluating the stability of nanofluids. The results obtained from the two methods are found to be in good agreement. Image analysis is, therefore, proposed as a nondestructive method with good accuracy, especially for evaluating the stability of high concentration nanofluids.     

Synthesis and photovoltaic properties of an alternating phenylenevinylene copolymer with substituted-triphenylamine units along the backbone for bulk heterojunction and dye-sensitized solar cells

We have fabricated bulk heterojunction (BHJ) photovoltaic devices based on the as cast and thermally annealed P:[6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) blends and found that these devices gave power conversion efficiency (PCE) of about 1.15 and 1.60% respectively. P is a novel alternating phenylenevinylene copolymer which contains 2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid units along the backbone and was synthesized by Heck coupling. This copolymer was soluble in common organic solvents and showed long-wavelength absorption maximum at 390-420 nm with optical band gap of 1.94 eV. The improvement of PCE after thermal annealing of the device based on the P:PCBM blend was attributed to the increase in hole mobility due to the enhanced crystallinity of P induced by thermal treatment. In addition, we have fabricated BHJ photovoltaic devices based on the as cast and thermally annealed PB:P:PCBM ternary blend. PB is a low band gap alternating phenylenevinylene copolymer with BF₂-azopyrrole complex units, which has been previously synthesized in our laboratory. We found that the device based on this ternary blend exhibited higher PCE (2.56%) as compared to either P:PCBM (1.15%) or PB:PCBM (1.57%) blend. This feature was associated with the well energy level alignment of P, PB and PCBM, the higher donor-acceptor interfaces for the exciton dissociation and the improved light harvesting property of the ternary blend. The further increase in the PCE with thermally annealed ternary blend (3.48%) has been correlated with the increase in the crystallinity of both P and PB. Finally, we used copolymer P as sensitizer for quasi solid state dye-sensitized solar cell and we achieved PCE of approximately 3.78%.     

Reducing the fuel consumption and emissions with the use of an external fuel cell hybrid power unit for electric taxiing at airports

Airport ground operations have a great impact on the environment. Various innovative solutions have been proposed for aircraft to perform taxi movements by deactivating their main engines. Although these solutions are environmentally beneficial, onboard and external electric taxiing solutions that are actively used and planned to be used in airports are not completely carbon-free. The disadvantages of the existing solutions can be alleviated by using an external fuel cell hybrid power unit to meet the energy required for taxiing that does not put additional weight on the aircraft. To reveal the power and energy required by the system, Airbus A320-200, which is a narrow-body aircraft and frequently used in airports, has been considered in this study. To determine the physical requirements of the aircraft for taxiing, a total of 900 s taxi-out movement consisting of four different periods with different runway slope, headwind, and maximum speeds were examined. According to the determined physical requirements, the conceptual design of the proposed fuel cell battery system was created and the physical data of the system for each period were obtained using the Matlab Simulink environment. As a result of the simulation, it is seen that the system consumes approximately 1.96 g of hydrogen per second. In addition, it has been calculated that 578.34 kg of CO₂ is emitted during the taxi-out movement. The results also show that as a result of using the proposed system, approximately 14.6 million tons of CO₂ emission per year can be prevented.