低温下半导体热电材料发电性能的初步研究

为了对液化天然气(LNG)的冷能回收利用，对半导体热电材料在低温下的发电性能进行了实验研究，得到了这种热电材料的发电性能随冷端温度变化的关系，并发现在热端温度不变的情况下，冷端温度在特定温度下热电堆的输出电动势达到最大值。运用数值方法理论计算了该热电堆在实验所处条件下的输出电动势。并将计算值与实验值进行了对比。     

半导体热电堆串、并联发电性能及热电堆复现性研究

对半导体热电堆的复现性进行了实验研究。以此为基础进行了热电堆的串联,并联实验,得到了半导体热电堆串联并联的规律,并用有限差分法对热电堆的各项发电性能指标进行了数值计算,为热电发电技术做了有益的探索。     

冷、热端温度对半导体热电堆发电性能影响的初步研究

对半导体热电堆的发电性能进行了实验研究,得出这种半导体热电堆在冷端温度不变的情况下,其发电性能与热端温度的关系,以及半导体热电堆在热端温度的情况下,冷端温度对其发电性能的影响,发现半导体热电堆作为电源时,其内阻对它的性能指标有很大的影响,而且内阻随着温度的升高而增大,采用间化的方法从理论上计算了热电堆的特性,得到了计算与实验结果基本吻合。     

小型热电联产生产成本分析和实例

简述了目前热电联产企业的现状,由于电力行业市场化势在必行,热电行业面临上网电价和大型电力行业竞争的严峻局面。通过对热电企业成本分析,指出热电比和投运率是影响热电联产企业供电成本最主要的因素。并进行了成本计算实例分析。     

建筑物小型热电联产在欧洲的发展

本文首先介绍了建筑物小型热电联产的特点及其在一些欧洲国家的发展与应用情况。然后指出了小型热电联产对环境污染的改善推广过程中应采取的措施，最后分析了小型热电联产的技术发展特点。     

评估热电联产经济性指数的推导及其应用

本文推导了个评估热电联产经济性的指数,讨论了提高热电联产经济性的各种措施.并以一由燃气透平和余热锅炉组成的区域供热、供冷热电联产为例分析了各种因素的变化,对热电联产经济性的影响,说明导得的指数不仅可方便地评估热电联产的经济可行性,而且也可评估下列经济和技术因素对经济性的影响:①提高电和热的售价,②降低燃料成本,③降低热电联产建设费用及其固定成本,④提高装机容量利用系数,     

太阳能半导体热电装置尺寸的优化分析

以多P-N结构成的半导体热电装置为研究对象,通过对热电装置模型的简化,并考虑材料参数随温度变化的实际情况,建立了热电效率随尺寸变化的数学模型。分析得出了影响热电装置热电效率的尺寸参数,为优化分析确定了设计变量和状态变量,并使有限元优化分析得到了简化。借助ANSYS优化分析模块,计算出了热电装置的最优化尺寸方案。     

热电联产最大的敌人是自己

本文对几个热电机组的数据进行分析后认为，假如没有达到规定的技术指标，热电联产不能提高能源利用率，也不能降低环境污染，这种现象如普遍存在，将会影响热电联产事业的发展。     

根据第一和第二定律的分析对选择的燃气轮机热电联产系统性能评价

对选择的燃气轮机热电联产系统的热力学性能,以第一定律和第二定律分析为基础进行了研究.探讨了余热锅炉设计中的喉部温差和工艺蒸汽压力对燃料利用率(第一定律效率)、电一热比、以及第二定律效率的影响.采用先进的工业燃气轮机的三个系统的结果清楚地表明,仅仅依据第一定律效率的性能评价是不适当的.决策者应发现本文中的方法在热电联产系统的比较和选择中是有用的.     

联合热电装置极限工作温差研究

基于非平衡热力学理论，对联合半导体热电装置循环模型的工作温差进行研究。分别针对热电发电机驱动热电制冷机和驱动热电热泵两类循环模型，给出了一定热源条件下，装置的极限工作温差同热电单元比的关系，并研究了极限工作温差随发电机高温热源温度的变化规律。     

厨房余热回收热电热泵储水式热水器的研究

在热电热泵热力学分析的基础上,设计研制了一台用于回收公共厨房排气余热、容积为36L的热电热泵储水式热水器,该装置采用热管散热器对热电热泵冷、热端散热,在回收厨房余热的同时制取生活热水.针对该热电热泵储水式热水器,对其制热性能进行实验研究,结果表明:热电热泵冷、热端温差是影响热电热泵制热性能的重要因素:排气温度越高,热水温度越低,则冷、热端温差越小,制热系数越大.在此基础上,对热电热泵储水式热水器进行优化,并对样机的性能进行测试,结果表明:工作电压对热水加热时间影响较大,工作电压越大,加热时间越短;在电压20V时将热水从28℃加热到46℃,样机相比普通电热水器节省电耗30%以上.     

A thermochemical reactor design with better thermal management and improved performance for methane/carbon dioxide dry reforming

A solar thermochemical reactor with better thermal management is proposed to improve the performance for dry reforming of methane. Conical cavity is introduced in the thermochemical reactor to adjust incident solar radiation distribution. Preheating area is adopted to recover sensible heat from gas outlet. Multiphysical model is presented for analyzing the overall performance of the reactor under different inlet flow rates. Also, local ideal reaction temperature required for maximizing local hydrogen production is analyzed according to the reaction kinetics. It is shown that better synergy between real temperature distribution and ideal temperature requirement can be achieved in this new reactor. Compared with conventional reactor, the present reactor exhibits the better performance in terms of reactant conversion, energy storage efficiency and hydrogen yield. Particularly, hydrogen yield is increased by 4.31%–17.12% at inlet flow rates between 6 and 12 L min^?1.     

改善吸附式制冷系统的方法研究

从吸附式制冷系统的各部件及热力关系着手，初步分析了一些造成实际循环与理论循环偏离的原因，指出了设计和完善吸附式制冷系统的基本思路和一些关键因素，对吸附式制冷系统的设计和运行调节有一定的指导意义。     

火力发电厂性能计算与能损分析的研究与实现

对火力发电厂能损分析中的一些重要问题进行了探讨,包括能损分析比较原理,应达值及基准工况的选取,求解湿蒸汽焓值的改进方法以及母管制机组中的义务分配等,提出了以实际运行工况为基准的偏差分析方法,避免了对变工况模型的依赖以及由于模型不完善可能导致的误差,具有真实反映机组性的优点,最后介绍了一种简便易行的能 分析系统的实现方案,并展示了某100MW机组的能损分析计算结果。     

单U、双U型埋管换热器换热性能与经济性研究

结合实际工程建立单U型与双U型埋管换热器实验系统,进行夏季排热和冬季取热实验。以单位井深换热量为评价指标对不同埋管方式的换热性能进行分析比较,得出排热和取热工况下,双U型埋管单位井深换热量均高于单U型。同时,分析了单U与双U型埋管换热器的经济成本构成,采用投资成本指标、静态投资成本差值和投资成本比数等参数,从换热性能和经济成本两方面对地下埋管换热器进行综合评价。     

几种空气源热泵热水器工质的实验研究

对三种混合工质(TJM01、TJM02、TJM03)的基本物理性质、安全环保性及溶油性进行了分析,又通过实验对三种混合工质的循环系统性能进行了分析。分析结果表明,三种混合工质在安全环保性和溶油性方面的差别都很小;在基本物性方面,TJM03较好;在系统性能方面,TJM03性能较好,而TJM01性能一般,TJM02性能较差。     

Design and control of an ideal heat-integrated distillation column (ideal HIDiC) system separating a close-boiling ternary mixture

Despite the fact that a stand-alone ideal heat-integrated distillation column (ideal HIDiC) can be thermodynamically efficient and operationally stable, the application of an ideal HIDiC system to separate a close-boiling multi-component mixture is still a challenging problem because of the possibility of strong interactions within/between the ideal HIDiCs involved. In this work, employment of two ideal HIDiCs to separate a close-boiling ternary mixture is studied in terms of static and dynamic performance. It is found that the ideal HIDiC system can be a competitive alternative with a substantial energy saving and comparable dynamic performance in comparison with its conventional counterpart. The direct sequence appears to be superior to the indirect sequence due to the relatively small vapor flow rates to the compressors. Controlling the bottom composition of the first ideal HIDiC with the pressure elevation from the stripping section to the rectifying section helps to suppress the disturbances from the feed to the second ideal HIDiC. Special caution should, however, be taken when the latent heat of the distillates is to be recovered within/between the ideal HIDiCs involved, because a positive feedback mechanism may be formed and give rise to additional difficulties in process operation.     

Influence of regeneration on the performance of a Brayton refrigeration-cycle working with an ideal Bose-gas

A general regenerative model of the Brayton refrigeration-cycle working with an ideal Bose-gas is used to discuss the influence of both the quantum degeneracy and regeneration on the performance of the cycle. Expressions for some important parameters, such as the refrigeration load, work input, coefficient of performance and minimum pressure-ratio, of the Brayton refrigeration-cycle are derived analytically and used to generate the refrigeration load, work input, coefficient of performance, and relative refrigeration-load versus pressure ratio curves. Moreover, several special cases are discussed in detail. The results obtained here will be helpful to reveal the performance characteristics of the Bose-Brayton refrigeration-cycle, further understand the difference and connection between the classical and quantum Brayton refrigeration-cycles, and theoretically expound the importance of the regeneration application for the Brayton refrigeration-cycle.     

A New Realistic Characteristics of Real Energy Conversion Process: A Contribution of Finite Size Thermodynamics

The perfection of the energy conversion process is currently gauged through a kind of quality indicator that compares the real performance of the process to that of the ideal reversible Carnot process. The criteria resulting from this commonly used approach give a false idea as to the real quality of the energy conversion process. Indeed, the real energy conversion process that generates true energetic power levels is compared to the ideal associated Carnot process, which generates a zero-output power level. The real conversion process implementing finite heat exchanger areas is then compared to the ideal process that needs an infinite heat exchanger area to fulfill the same power requirements. This paper presents a new thermo-economic approach, based on Finite Size Thermodynamics, that is more suitable for qualifying real energy conversion processes. This approach takes into account the external thermodynamic irreversibilities relative to the heat transfer rate through a finite size heat exchanger surface between the external heat sources or sinks and an ideal process without internal thermodynamic irreversibilities. This new approach enables a more realistical evaluation of ideal performances of real energy conversion processes. It makes possible the definition of new criteria that characterize more reasonably the quality of a real thermal process compared with the corresponding endoreversible process the same power duty (performance criterion) or the same involved total heat exchanger surface (technical criterion).     

Appropriate strategies for determining the photoconversion efficiency of water photoelectrolysis cells: A review with examples using titania nanotube array photoanodes

Proper determination of light to chemical energy conversion efficiency of a photoelectrochemical cell is critical in evaluating its performance. Since the demonstration of photocatalytic water splitting using semiconductor electrodes, many strategies have been suggested and employed for the determination of photoconversion efficiency. We review these approaches as well as factors limiting ideal case efficiencies. Cell efficiency values are found to vary considerably depending upon the errors involved in the basic assumptions and measurement procedures. With researchers using different expressions for efficiency calculation, the values can be inconsistent and a direct comparison meaningless; we demonstrate this with the help of photocurrent data obtained from a photoelectrolysis cell employing titania nanotube array photoanodes. We find, and demonstrate, that realistic solar photoconversion efficiencies can be estimated with the help of incident photon to electron conversion efficiency (IPCE) values and solar irradiance data using the expression: ratio of the net power output to the power supplied by the incident light, where the net power output is the difference between the maximum electrical power available from the hydrogen produced and the power supplied by an external source. The power from the external source is determined by taking product of the photocurrent and the potential difference between the working and counter electrodes.