"Frontiers in Energy"

Li, Minghui

2011 "Frontiers in Energy"

doi: 10.1007/s11708-010-0130-x

Abstract From 2006 to 2009, the aggregate energy intensity of China fell by 14.38%,1) which means that China has made substantial progress towards its goal of achieving approximately a 20% reduction in energy intensity during the period of the 11th FYP (Five-Year Plan). This paper describes some new properties of the mechanism for the decrease in China’s energy intensity since the beginning of the 11th FYP. First, compared with the period of the 10th FYP, technical, structural, and residential energy-savings have been improved to a certain extent. Secondly, unlike the dynamic mechanism before 2000, technical energy savings have been the main driver of momentum since the beginning of the 11th FYP. Next, although structural energy savings are not the main factor, they are still a key factor for the decrease in energy intensity. Finally, residential energy savings are still a stable driver of momentum for the decline in China’s energy intensity.

Guo, Lei;Zhang, Shusheng;Cheng, Lin

2011 "Frontiers in Energy"

doi: 10.1007/s11708-010-0128-4

Abstract To explore the mechanism of boiling bubble dynamics in narrow channels, we investigate 2-mm wide Iand Z-shaped channels. The influence of wall contact angle on bubble generation and growth is studied using numerical simulation. The relationships between different channel shapes and the pressure drop are also examined, taking into account the effects of gravity, surface tension, and wall adhesion. The wall contact angle imposes considerable influence over the morphology of bubbles. The smaller the wall contact angle, the rounder the bubbles, and the less time the bubbles take to depart from the wall. Otherwise, the bubbles experience more difficulty in departure. Variations in the contact angle also affect the heat transfer coefficient. The greater the wall contact angle, the larger the bubble-covered area. Therefore, wall thermal resistance increases, bubble nucleation is suppressed, and the heat transfer coefficient is lowered. The role of surface tension in boiling heat transfer is considerably more important than that of gravity in narrow channels. The generation of bubbles dramatically disturbs the boundary layer, and the bubble bottom micro-layer can enhance heat transfer. The heat transfer coefficient of Zshaped channels is larger than that of the I-shaped type, and the pressure drop of the former is clearly higher.

Liu, Zongde;Liu, Miao;Zhao, Liping

2011 "Frontiers in Energy"

doi: 10.1007/s11708-010-0129-3

Abstract This paper introduces the applied background of wear and corrosion-resistant materials in the electricity industry. Next, the paper summarizes the development of preparation technology for cermets and cermet coatings and claddings, finally explaining the application and development of submicron-grain cermet coatings and claddings through reaction synthesis technology.

Hu, Yuanyang;Wang, Liwei;Xu, Lu;Wang, Ruzhu;Kiplagat, Jeremiah;Wang, Jian

2011 "Frontiers in Energy"

doi: 10.1007/s11708-011-0152-z

Abstract A two-stage chemisorption cycle suitable for deep-freezing application driven by low-temperature heat source was proposed. Through two-stage desorption processes, the two-stage cycle can break through the limitations of the heating temperature and ambient cooling temperature. The two-stage cycle based on CaCl2/BaCl2-NH3 working pair can utilize the heat source with a temperature of above 75°C, and simultaneously realize deep-freezing all the year round. Experimental results and performance prediction show that the adsorption quantity of calcium, theoretical coefficient of performance (COP) and optimized specific cooling power (SCP) of the CaCl2/BaCl2-NH3 chemisorption system are 0.489 kg/kg (salt), 0.24 and 120.7W/kg, when the heating temperature, ambient cooling temperature, pseudo-evaporating temperature and mass ratio of reacting salt and expanded graphite are 85, 30, −20, and 4:1, respectively.

Yang, Yang;Liu, Jing

2011 "Frontiers in Energy"

doi: 10.1007/s11708-010-0126-6

Abstract Most people were not aware of the role of energy as a basic force that drives the development and economic growth of the world until the two great oil crises occurred. According to the conservation law, energy not only exists in various forms but is also capable of being converted from one form to another. The common forms of energy are mechanical energy, chemical energy, internal energy, electrical energy, atomic energy, and electromagnetic energy, among others. The fluids in nature serve as the most common carriers and media in the energy conversion process. Following the rapid development of microelectromechanical systems (MEMS) technology, the energy supply and conversion issue in micro/nano scale has also been introduced in research laboratories worldwide. With unremitting efforts, great quantities of micro/nano scale energy devices have been investigated. Micro/nanofluid shows distinct features in transporting and converting energy similar to their counterpart macroscale tasks. In this paper, a series of micro/nanofluid-enabled energy conversion devices is reviewed based on the transformation between different forms of energy. The evaluation and contradistinction of their performances are also examined. The role of micro/nanofluid as media in micro/nano energy devices is summarized. This contributes to the establishment of a comprehensive and systematic structure in the relationship between energy conversion and fluid in the micro/nano scale. Some fundamental and practical issues are outlined, and the prospects in this challenging area are explored.

Hou, Youmin;Xie, Danmei;Li, Wangfan;Yu, Xinggang;Shi, Yang;Qin, Hanshi

2011 "Frontiers in Energy"

doi: 10.1007/s11708-011-0160-z

Abstract As a result of adopting saturation steam and long blade, problems of water erosion of last stage blade for steam turbine become more prominent. In order to improve the operation reliability and efficiency of steam turbine, it is necessary to investigate the nonequilibrium condensing wet steam two phase flow and the dehumidity method. A wet steam model with user defined function based on FLUENT software was investigated to simulate the steam condensing flow in the cascades. The simulation consequences show that the pressure variations in simulation depict a good agreement with the experiment data. On the basis of the discrete phase model simulation results and experiment data, the efficiency of existing dehumidity blade with suction slot was calculated. A new stationary dehumidity blade was designed to elevate the dehumidity efficiency: the efficiency in the suction surface was increased by 21.5%, and that in the pressure surface was increased by 12.2%.

Alaydi, Juma Yousuf

2011 "Frontiers in Energy"

doi: 10.1007/s11708-010-0134-6

Abstract The analysis of collected wind data at two sites in the Gaza Strip, namely, Gaza City and Gaza International Airport in Rafah city, is presented. The two sites are candidates for remote area wind energy applications. The purpose of this paper is to present the results of the assessment of wind energy potential in the Gaza Strip in order to evaluate the wind regimes for installing wind energy conversion systems for power generation. The data on wind speed, direction and frequency distribution are used to analyze wind energy characteristics and availability at some stations in the Gaza Strip. The vertical extrapolation was based on the power-law expression, and the wind energy and potential have been estimated at the wind turbine hub height of approximately 50 m. Furthermore, the values of theWeibull parameters c and k are determined from summary statistics of wind resource. Consequently, the wind power is estimated by adoption of the Weibull distribution expression. Based on the results of this paper, sites are recommended for wind energy exploitation in the Gaza Strip.

Liu, Lijun;Liu, Xin;Li, Zaoyang;Kakimoto, Koichi

2011 "Frontiers in Energy"

doi: 10.1007/s11708-011-0155-9

Abstract A computer simulator with a global model of heat transfer during crystal growth of Si for solar cells is developed. The convective, conductive, and radiative heat transfers in the furnace are solved together in a coupled manner using the finite volumemethod. A three-dimensional (3D) global heat transfer model with 3D features is especially made suitable for any crystal growth, while the requirement for computer resources is kept permissible for engineering applications. A structured/unstructured combined mesh scheme is proposed to improve the efficiency and accuracy of the simulation. A dynamic model for the melt-crystal (mc) interface is developed to predict the phase interface behavior in a crystal growth process. Dynamic models for impurities and precipitates are also incorporated into the simulator. Applications of the computer simulator to Czochralski (CZ) growth processes and directional solidification processes of Si crystals for solar cells are introduced. Some typical results, including the turbulent melt flow in a large-scale crucible of a CZ-Si process, the dynamic behaviors of the mc interface, and the transport and distributions of impurities and precipitates, such as oxygen, carbon, and SiC particles, are presented and discussed. The findings show the importance of computer modeling as an effective tool in the analysis and improvement of crystal growth processes and furnace designs for solar Si material.

Luszcz, Pawel;Xu, Hongming;Wyzsnski, Mirek;Ma, Xiao;Stevens, Rob;Tsolakis, Athanasios

2011 "Frontiers in Energy"

doi: 10.1007/s11708-011-0154-x

Abstract An optically accessed, single cylinder engine operated in homogenous charge compression ignition (HCCI) mode with negative valve overlap (NVO) strategy was used to perform combustion processes diagnostics under premixed conditions corresponding to the low load regime of the HCCI operational envelope. The aforementioned processes analysis was conducted utilizing synchronized simultaneous combustion event crank-angle resolved images, acquired through piston crown window with in-cylinder pressure recording. This investigation was carried out for one-step ignition fuel—standard gasoline, fuel proceeding single-stage ignition process under conditions studied. The initial combustion stage is characterized by a maximum local reaction spreading velocity in the range of 40–55 m/s. The later combustion stage reveals values as high as 140 m/s in case of stoichiometric combustion. The mixture as well as combustion stages effects are pronounced in these observed analytical results.

Metwalley, Sameh M.;Abouel-Seoud, Shawki A.;Farahat, Abdelfattah M.

2011 "Frontiers in Energy"

doi: 10.1007/s11708-011-0158-6

Abstract Natural gas (NG) represents today a promising alternative to conventional fuels for road vehicles propulsion, since it is characterized by a relatively low cost, better geopolitical distribution than oil, and lower environmental impact. This explains the current spreading of compressed natural gas (CNG) fuelled spark ignition (SI) engine, above all in the bi-fuel version, which is able to run either with gasoline or with NG. However, the aim of the present investigation is to evaluate the emission characteristics at idling condition. The vehicle engine was converted to bifueling system from a gasoline engine, and operated separately either with gasoline or CNG. Two different fuel injection systems (i.e., multi-point injection (MPI)-sequential and closed-loop venturi-continuous) are used, and their influences on the formation of emissions at different operating conditions are examined. A detailed comparative analysis of the engine exhaust emissions using gasoline and CNG is made. The results indicate that the CNG shows low air index and lower emissions of carbon monoxide (CO), carbon dioxide (CO2), and total hydrocarbon (THC) compared to gasoline.