A method for the determination of dynamic resistance of photovoltaic modules under illumination

Dynamic resistance of solar cells and modules have been determined from a dark IV characteristic curve. In the determination, it is often assumed that series resistance R_s is small and the shunt resistance R_sh very large, their effects can be neglected. The resultant dynamic resistance can be called the external dynamic resistance R_D. R_D is normally taken to be the slope of the IV characteristic of a cell or a module. We present in this paper a new method to determine an internal dynamic resistance R_d of a photovoltaic module based on one illuminated IV curve, taken into account finite series and shunt resistance. In the experiment, we measure illuminated and dark characteristics of a 4.5 Wp commercial X-Si solar module (9 V, 500 mA) at 25–27 °C, and calculate R_d and R_D. We see that R_d and R_D can be markedly different. Comparison is also made on the series resistance R_s and shunt resistance R_sh determined from single IV curve and two IV curve methods.     

Direct numerical simulation of nonpremixed flame-wall interactions

The objective of the present study is to use detailed numerical modeling to obtain basic information on the interaction of nonpremixed flames with cold wall surfaces. The questions of turbulent fuel-air-temperature mixing, flame extinction, and wall-surface heat transfer are studied using direct numerical simulation (DNS). The DNS configuration corresponds to an ethylene-air diffusion flame stabilized in the near-wall region of a chemically inert solid surface. Simulations are performed with adiabatic or isothermal wall boundary conditions and with different turbulence intensities. The simulations feature flame extinction events resulting from excessive wall cooling and convective heat transfer rates up to 90 kW/m². The structure of the simulated wall flames is studied in terms of a classical mass-mixing variable, the fuel-air based mixture fraction, and a less familiar heat loss variable, the excess enthalpy variable, introduced to provide a measure of nonadiabatic behavior due to wall cooling. In addition to the flame structure, extinction events are also studied in detail and a modified flame extinction criterion that combines the concepts of mixture fraction and excess enthalpy is proposed and then tested against the DNS data.     

传热传质过程和设备的有限时间热力学优化

1前言能源的短缺与高效利用问题是当代世界各国面临的重大社会问题之一。随着世界人口和经济的迅速增长,能源的消耗急剧地增加,并导致能源的严重短缺。因此,研究充分、高效利用现有能源的方式成为我们目前的重要任务。蒸馏作为全球范围内耗能量最大的工业,引起了很多工程界和物     

冷量计量仪表的选型

首先介绍了冷量计量方法,然后以盐水为例介绍了在冷量计量方面应该注意的问题,并对参与冷量计量的仪表在选择时应注意的事项作了详细说明。     

海水冷却电厂循环水合理取水方式研究

对海水冷却电厂循环水取水方式进行了研究,提出深层取水的概念,指出确定取水位置应考虑的影响因素,并对黄岛电厂拟采取的取水方案进行经济性分析。该方案实施后总体经济效益显著,对沿海地区电厂建设具有示范作用和指导意义。     

汽轮机热喷涂的研究与应用

采用超音速火焰喷涂方法,通过工艺试验研究,得到一套最佳喷涂工艺,涂层为Co基碳化钨时,明显提高了汽轮机高温部件的耐冲蚀能力。     

炼油化工节能技术新进展(二)

炼油、石化生产过程中大量存在的分离、换热和反应工序,节能潜力巨大。本文评述了炼油化工生产过程中可资采用的一系列节能新技术,主要有:微波分离、电磁分离、吸附分离、超声波分离、络合分离、膜法分离、分壁式塔器、抽提蒸馏等新的分离技术,以及反应蒸馏技术、超临界反应技术、膜法反应技术等新的反应技术和新型换热器及热能回收技术。     

分离式热管煤气、空气双预热器在上海宝钢4#高炉热风炉上的应用

本文介绍了分离式热管煤气、空气双预热器在上海宝钢4#高炉热风炉上的实际应用情况,通过换热器将煤气和空气预热来提高热风炉风温,从而提高高炉冶炼的经济效益。文章从技术、节能以及经济效益三方面详细分析其优越性。     

Q130/850-35-3.82/450型三废混燃余热锅炉的设计

本文分析了我国的能源形势,能源利用率与世界先进国家存在的差距,阐述了余热锅炉在回收余热、环境保护等方面起着重要作用,重点介绍了三废混燃余热锅炉的结构设计特点。     

太阳能与热泵技术应用在暖通空调中的进展

热泵是一项重要的节能技术,但因自身的缺陷使得它的应用遇到一定的困难。随着太阳能利用技术不断进步,太阳能系统集热效率逐渐提高,太阳能与热泵之间可以优势互补的特点逐渐显现。越来越多的专家、学者和企业的工程人员投入到对太阳能技术和热泵技术联合应用的研究之中,并取得了一定的成果。本文综述了太阳能热泵的一般原理及其各种模式控制方案,介绍了目前国内外的研究情况和一些有代表性的成果,并对将来太阳能热泵复合技术的发展进行了一些讨论。