Effects of baffle position in serpentine flow channel on the performance of proton exchange membrane fuel cells

This study used a three-dimensional numerical model of a proton exchange membrane fuel cell with five types of channels:a smooth channel(Case 1);eight rectangular baffles were arranged in the upstream(Case 2),midstream(Case 3),downstream(Case 4),and the entire cathode flow channel(Case 5)to study the effects of baffle position on mass transport,power density,net power,etc.Moreover,the effects of back pressure and humidity on the voltage were investigated.Results showed that compared to smooth channels,the oxygen and water transport facilitation at the diffusion layer-channel interface were added 11.53%-20.60%and 7.81%-9.80%at 1.68 A·cm^(-2)by adding baffles.The closer the baffles were to upstream,the higher the total oxygen flux,but the lower the flux uniformity the worse the water removal.The oxygen flux of upstream baffles was 8.14%higher than that of downstream baffles,but oxygen flux uniformity decreased by 18.96%at 1.68 A·cm^(-2).The order of water removal and voltage improvement was Case 4>Case 5>Case 3>Case 2>Case 1.Net power of Case 4 was 9.87%higher than that of the smooth channel.To the Case 4,when the cell worked under low back pressure or high humidity,the voltage increments were higher.The potential increment for the back pressure of 0 atm was 0.9%higher than that of 2 atm(1 atm=101.325 kPa).The potential increment for the humidity of 100%was 7.89%higher than that of 50%.

A 10kW-scale Distributed Power Plant of Natural Gas-Proton Exchange Membrane Fuel Cell

A 10 kW-scale natural gas fueled proton exchange membrane fuel cell(PEMFC) distributed power plant is presented in this paper,which is designed for cogeneration of power and heat. With homemade catalysts for CO removal in a two-stage methanation process and integrated reactor in the fuel processing system,the reformed fuel with CO molar fraction less than 10-5 is obtained for the fuel cell stack. Based on Matlab/Simulink/Stateflow and xPC Target platform,a rapid control prototype(RCP) is developed for real-time condition management,signal tracking and parameter tuning,data storing,and man-machine interaction. In a typical running with 4.3 kW stack power,the hydrogen production efficiency,gross power generation efficiency and heat recovery efficiency approach to 76%,41% and 50%,respectively. The peak stack power reaches 7.3 kW. Though there is still considerable dis-tance to long-term operation at 10 kW-scale net power generation,it is a milestone for the PEMFC-based stationary application in China.

Selection of organic Rankine cycle working fluid based on unit-heat-exchange-area net power

To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.

A more precise method to evaluate kinetic leakage of anion exchange resin used in condensate polishing of power plant

Sulfate mass transfer coefficient(MTC) is a sensitive parameter to evaluate the kinetic leakage of anion exchange resin used in condensate polishing system of thermal and nuclear power plant.However,a sufficiently precise determination method has not been well established.In this paper,the final expression of sulfate MTC derived based on plug flow reactor model is the same as Harries' model,which is widely acknowledged in this field.In the determining system we constructed,in-situ calibration of the concentration of sulfate and its cation conductivity was conducted and sulfate MTCs of four typical strongly basic anion exchange resin samples were determined.The systematic error is 8.26% and the calibrated curve used for quantifying sulfate is obtained.The repeatability and reproducibility standard deviation are 0.05×10^(-4) m·s^(-1) and 0.07×10^(-4) m·s^(-1) respectively,which are lower than previous works.By controlling test condition accurately,this study has developed a more precise sulfate MTC determining method.This method provides a basis for further research.

Impacts of a Japan–South Korea power system interconnection on the competitiveness of electric power companies according to power exchange prices

In many regions,international power system interconnections provide economic,energy-security,environmental,and technical benefits.In contrast,such interconnections remain scarce in Northeast Asia.In 2016,after approving a joint memorandum of understanding between major electric power companies from China,Japan,South Korea,and Russia,related initiatives regained momentum in the region.Nevertheless,the corresponding developments in Japan remain limited,mainly owing to the lack of involvement of Japanese electric power companies.This study represents a pioneering attempt to provide an economic assessment based on power exchange prices of a power system interconnection between Japan and South Korea regarding the competitiveness of electric power companies in terms of competitive business segments and strategic consequences.We found that although the position of Japanese generators may slightly deteriorate,that of the supply segment would substantially improve,thus suggesting that more opportunities than threats are derived from the interconnection.This promising outcome may foster the adoption of an interconnection with South Korea considering the positive economic and business perspectives in Japan.Furthermore,realizing the interconnection may improve the energy security and air quality in the region.

APRICING METHOD of SURPLUS THERMAL POWER EXCHANGE BETWEEN GRIDS

This paper presents a case study on surplus thermal power being exchange between power grids and associate prices. The analysis shows the potential value of surplus thermal power exchange between grids under the condition whatever a grid is excessive or short in capacity.

Power Exchange Summary of SGCC in 2007

In 2007, State Grid Corporation of China (SGCC) actively executed Implementation Opinions on Deepening Power Institutional Reform during the 11th Five-Year Plan Period and pressed forward three-tier power market construction. Based on regulated and transparent power transactions, SGCC actively enhanced service quality, strived for optimal allocation of electricity in a wider scope. Meanwhile, great achievements have been made in energy-conservation and emission-reduction. This paper briefly introduces three-tier power market construction with market transaction data in 2007, then summarizes and analyzes the characteristics of power trading. Finally, suggestions on further development of power market are tentatively given.

Exchange Server 2010的远程PowerShell

Microsoft Exchange Server 2010增加了对远程机器执行PowerShell命令的功能。如果你管理多个Exchange组织，或者希望充分实现对Exchange服务器的远程访问，这个功能将对你很有帮助。

The Power of Inter-Party Exchange

THOUGH far away from each other in distance, relations between China and African countries have moved ever closer in recent years. No doubt, inter-party exchange has played an important part in this process. After the founding of the People＇s Republic of China in 1949. the Communist Party of China （CPC）, China＇s ruling Party, has maintained friendly relations with its counterparts in African countries, greatly promoting cooperation in various fields between China and Africa.

Design of Portable Shell and Tube Heat Exchanger for a Solar Powered Water Distiller

This study presents theoretical considerations and results of a portable shell and tube heat exchanger in a solar water distiller system. The device is composed of a glass heat exchanger, which served as a condenser for vapor condensing which were produced in black paint solar absorber. It was also composed of a tank for water source and a tank for produced distilled water. Shell and tube was designed and simulated using an implicit numerical scheme. Simulation results showed that accumulated mass water greatly depended on the inlet vapor temperature and volume, heat exchanger material, coolant water temperature and volume. Thus, changing the material from stainless steel to glass in the same condition （vapor temperature, vapor volume, coolant temperature and coolant volume）. These inexpensive shell and tube heat exchangers permitted to produce 40 litre/day, distilled water from vapor with 378 K inlet temperature in atmosphere pressure. If inlet pressure increases, vapor temperature will decline and thereupon, heat exchanger＇s efficiency tangibility will increase.

Meta-sided exchange环及其扩张

讨论了meta-sided exchange环的性质。证明了如果R是Abelian meta-sided exchange环,则对R的任意素理想P,都有R/P是局部环;如果R是Abelian环,(S,≤)是严格序幺半群且对任意s∈S,都有0≤s,则广义幂级数环[[RS,≤]]是meta-sided exchange环当且仅当R是meta-si-ded exchange环。

“One Belt One Road”Initiative and China and the Middle East Media Exchanges

The proposal of the“One Belt One Road”initiative has brought historic opportunities for media exchanges between China and the Middle East,and has also put forward higher requirements for media cooperation between the two sides.At present,media exchanges between China and the Middle East have made positive progress,but there are still some problems.To do a good job in media exchange and cooperation between China and the Middle East,we should start with the implementation and improvement of existing mechanisms,the transformation of media working methods and concepts,the broadening of communication channels,the concern for interests,and the strengthening of personnel training,so as to continuously improve the effectiveness of media exchange and cooperation between the two sides and promote the healthy development of bilateral relations.

DEVELOPMENT OF A FOREIGN EXCHANGE TRANSACTION SYSTEM

This paper presents a new transaction method in terms of which deals are concluded by competitive prices, and indicates its design on multiuser platform, especially the research of synchronization and vieing for powers. The system was programmed with SCO FOXBASE 210, C language and Shell. The result of nearly two year′s use proved that the transaction method and its accomplishments are all practicable.

Development and Test of a New Solar-Air Heat Exchanger for the Linear Mirror II System

The Linear Mirror II is an innovative system to concentrate solar energy, developed by Isomorph SRL. In this paper, a solar-air heat exchanger of new conception is presented and tested together with a Linear Mirror II. The heat exchanger surface is selective with respect to direction and position of light absorption and emission and once heated by the Linear Mirror II, can reach an air temperature of up to 230&degC.

Primary Study of Power-Exchanging Trans- action Model Among Price-Varied Power Plants in Practical Conditions

At present, electricity price to grid of domestic power plants is priced by the national administration based on the policy of "one power plant with one electricity price to grid," which is difficult to realize real bidding for access to grid in practice in a short term. This paper presents one kind of power-exchanging transaction model among price-varied power plants, which will be beneficial to price-varied power plants without any loss of profits of them and guarantee state-owned assets profits in minimum loss with no promotion of average price limit by power plants. Under ideal conditions, the computation results showed the sufficiency and necessity of power-exchanging transaction and maximum similarity with the requirements of optimized resources disposition in economics. The presented model is shown to be full of practicability and has been used in some part of power market.