Electrodeposition and morphology analysis of Bi-Te thermoelectric alloy nanoparticles on copper substrate

Nanoscale Bi-Te particles with thermoelectric properties on copper substrate were investigated. The substrate was prepared by electroplating copper layer on a copper zinc alloy plate in a copper sulfate solution. Electrodeposition of the Bi-Te alloy particles was then performed in a nitrate bath. The electrolyte is composed of 0.05 M bismuth nitrate and 0.01 M tellurium dioxide dissolved in 2.0 M HNO₃. Cyclic voltammetry and quartz microbalance tests associated with the electrodeposition process were conducted to show the mechanism and kinetics of the deposition. The morphology and compositional analysis of Bi-Te was obtained using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) respectively. The morphology analysis suggested that nanoscale Bi-Te particles were obtained and the EDS results indicated that the surface of the copper substrate contained Cu₂O. The atomic ratio 1:1 for Bi:Te in the alloy, which is equivalent to the weight percentage of Bi:Te = 62%:38% was confirmed from the data obtained.     

Enhancement of high temperature thermoelectric properties of intermetallic compounds based on a Skutterudite IrSb3 and a half-Heusler TiNiSb

Phonon glass and electron crystal (PGEC) thermoelectric materials have been expected to be a new class of thermoelectric materials for high temperature applications. Among the efforts to optimize the high temperature thermoelectric properties of various PGEC thermoelectric materials, recent experimental works on the Skutterudite IrSb₃ and half-Heusler TiNiSb intermetallic compounds are presented herein by which the material design concept for high energy conversion efficiency, i.e. a high figure of merit, is suggested. It is revealed that the thermoelectric efficiency of IrSb₃ can be increased by the decrease of lattice thermal conductivity due to the rattling effect of La atoms filled in the structural vacancies of the Skutterudite crystal structure. In the half-Heusler TiNiSn, high temperature thermoelectric properties are improved by Hf substitution to the Ti sites by reducing lattice thermal conductivity and also by Sb doping to increase power factor. It is concluded that the proper alloy designing for controlling crystal structure and carrier concentration could enable these intermetallic compounds to exhibit a high potential for elevated temperature thermoelectric applications.     

空分设备冷却器的酸洗除垢及维护

简介了空分设备各冷却器的材质 ,详细介绍了酸洗除垢的过程及酸洗后的处理工作 ,最后阐述了循环水系统的日常维护措施     

The maximum temperature difference and polar characteristic of two-stage thermoelectric coolers

The maximum temperature differences (MTDs) of three types of two-stage thermoelectric (TE) coolers are analysed, which are the ones with thermocouples at two stages electrically connected in series and parallel and electrically separated, respectively. The analyses are all performed with respect to an important ratio r in two-stage TE coolers, viz the ratio of thermocouple number between stages. The MTDs of the first and the last configurations can be both far higher than that of a one-stage TE cooler, which may promote the cryogenic applications of TE coolers. When r approaches to infinity, close-form formulae of their limiting MTDs are found. In the mean time, the polar characteristic of two-stage TE coolers is discussed, when the supplied electric current(s) is alternated.     

离心压缩机级间冷却器国产化改造后的性能分析

介绍离心空压机级间冷却器国产化改造后的运行情况,从冷却器管束分布形式、管束总数量、管束尺寸以及冷却器通道容积等方面,比较分析原装冷却器与国产冷却器的性能。     

Design and construction of a traveling wave thermoacoustic refrigerator

A traveling wave thermoacoustic refrigerator was designed, constructed, and tested. This refrigerator was composed of a linear motor, a branched tube, and a looped tube. A regenerator, composed of many screen meshes, was installed inside the looped tube. When the linear motor delivers an acoustic wave to the branched and looped tubes, heat pumping occurs along the regenerator. In this work, the regenerator radius and position were numerically optimized and the performance of the optimized refrigerator was measured. At the optimized values of regenerator radius and position, the refrigerator achieves a minimum cold temperature of 232 K and about 20% of the Carnot coefficient of performance at 265 K.     

陈列冷柜玻璃门表面结露问题的试验研究

透明的玻璃陈列冷柜为顾客挑选食品提供了方便,但现有的陈列冷柜玻璃门表面容易凝结水雾,失去透明展示效果。本课题在对玻璃陈列冷柜玻璃表面结露条件与影响因数进行分析的基层上,试验研究了采用双层发热导热膜玻璃冷柜玻璃门表面结露有关问题,并与普通双层充氩气涂层玻璃门冷柜进行了性能比较,为玻璃展示冷柜玻璃表面防露设计提供参考。     

空分设备氧透冷却器酸洗除垢

介绍了空分设备氧透冷却器酸洗除垢的酸洗剂的配比及除垢过程 ,分析了酸洗除垢的经济效益 ,最后指出了酸洗除垢在空分设备清洗中的前景。     

Effects of thermal conduction in microchannel gas coolers for carbon dioxide

A numerical code was developed for an accurate fully three-dimensional simulation of crossflow compact heat exchangers using finned flat tubes with internal microchannels; such components are often employed as gas coolers in transcritical refrigerating machines CO₂ operated. The equations describing the system were discretised by means of a finite-volume and finite-element hybrid technique for strictly adhering to the real heat transfer process regarding the finned surfaces. The numerical code uses recent correlations by different authors for predicting the heat transfer coefficients both refrigerant side and air side. The results of simulations are verified against experimental data reported in the open literature.The aim of this work is to investigate the effects of thermal conduction inside metal on the overall performance of the considered gas coolers; high-resolution meshes for the discretisation of separating wall and fins makes it possible to avoid much of the approximations typical of the traditional approaches. In particular the efficiency of finned surfaces, the real distribution of thermal fluxes between the two fin roots and the effects of thermal conduction along the walls of microchannel flat tubes are extensively discussed.The numerical simulations confirm that the traditional approach for describing fins, which assumes them as adiabatic at the middle section in order to decouple the equations accounting for the effect of different temperatures at the fin roots, can be considered acceptable in a wide range of applications. In a similar way, the conduction on fins along the direction of the air velocity and the longitudinal conduction on tubes produce a negligible effect on the performance of the considered class of heat exchangers.     

热泵热水器发展现状及性能试验研究

介绍了热泵型热水器的原理、特点和市场发展现状，在大量调研的基础上讨论了热泵热水器未来的发展潜力。对市场上的一种典型热泵热水器的性能进行了试验研究，得到了不同工况下的各种数据，通过理论及数据分析，提出改良措施，为热泵热水器的进一步应用提供参考。     

Performance analysis of automatic storage/retrieval systems by stochastic modelling

This study considers an automated storage/retrieval system that performs either single or dual commands and analyses it as a queuing system with two waiting spaces and one server. It is assumed that the storage and retrieval commands arrive at the system according to Poisson processes with different rates and that the service times of single and dual commands are distributed differently. The steady-state probability distribution of the number of commands in the system at the service completion epochs is derived; subsequently, the semi-Markov process is employed to obtain the distribution at an arbitrary time. Several performance measures are derived and include the expected number of commands in the system, the expected waiting time, the probability that an arbitrary command cannot enter the system (the ‘blocking probability’) and the utilization of the storage/retrieval machine.     

不可逆空气制冷循环的制冷率和制冷系数优化

用有限时间热力学方法分析恒温热源不可逆空气制冷循环特性 ,在总热导率一定的条件下 ,研究最优制冷率、制冷系数时热导率的最优分配 ,并分析了各种参数对循环特性的影响 ,所得结果对工程制冷系统设计有一定的指导意义。     

User-friendly and intuitive graphical approach to the design of thermoelectric cooling systems

This study proposes a user-friendly graphical method for calculating the steady-state operational point of a thermoelectric cooler (TEC)-based active cooling system, including the heatsink role. The method is simple and intuitive and provides comprehensive information about the cooling system such as its feasibility, required heatsink, the TEC current, temperatures of the cold and hot sides, and coefficient of performance (COP). The method could help designers to examine and choose a thermoelectric module from catalogues to meet a specific cooling problem. To start using the method, designers need only the experimental TEC data provided by practically all manufacturers of such devices. The experimental results of this study verify the high accuracy of the proposed model and graphical approach.     

A comprehensive design and rating study of evaporative coolers and condensers. Part I. Performance evaluation

The mathematical models of evaporative fluid coolers and evaporative condensers are studied in detail to perform a comprehensive design and rating analysis. The mathematical models are validated using experimental as well as numerical data reported in the literature. These models are integrated with the fouling model presented in an earlier paper, using the experimental data on tube fouling. In this paper, we use the fouling model to investigate the risk based thermal performance of these evaporative heat exchangers. It is demonstrated that thermal effectiveness of the evaporative heat exchangers degrades significantly with time indicating that, for a low risk level (p=0.01), there is about 66.7% decrease in effectiveness for the given fouling model. Furthermore, it is noted that there is about 4.7% increase in outlet process fluid temperature of the evaporative fluid cooler. Also, a parametric study is performed to evaluate the effect of elevation and mass flow rate ratio on typical performance parameters such as effectiveness for rating calculations while surface area for design calculations.     

循环加热式热泵热水机性能评价系统研究

对国家标准中循环加热热泵热水机性能评价方法的研究,结合主流性能评价系统存在的不足,给出提高性能评价系统精度及可行性的思路:一是尽可能的减少热量损失所占机组总加热的比重,二是简化精确计算热量损失方法。PPR管件替换钢制管件可以有效减少评价系统热损,热损修正函数的引入使热损计算更加准确、易行,使得循环加热式热泵热水机组制热量的计算也更加准确,性能系数的得出更加可靠,从很大程度上促进了热泵热水机行业的性能改善与研发进程,加速热泵热水机替换传统热水器的进程,为国家的低碳节能与可持续发展有一定促进。     

Thermal conductivity of InAs quantum dot stacks using AlAs strain compensating layers on InP substrate

The growth and thermal conductivity of InAs quantum dot (QD) stacks embedded in GaInAs matrix with AlAs compensating layers deposited on (1 1 3)B InP substrate are presented. The effect of the strain compensating AlAs layer is demonstrated through Atomic Force Microscopy (AFM) and X-ray diffraction structural analysis. The thermal conductivity (2.7 W/m K at 300 K) measured by the 3ω method reveals to be clearly reduced in comparison with a bulk InGaAs layer (5 W/m K). In addition, the thermal conductivity measurements of S doped InP substrates and the SiN insulating layer used in the 3ω method in the 20–200 °C range are also presented. An empirical law is proposed for the S doped InP substrate, which slightly differs from previously presented results.     

Optimum configurations of vertical fins under condensation of saturated vapor

In the present study, an optimum fin shape envelope was determined via a theoretical procedure that minimized the fin volume subject to constrained heat transfer rate. A unified analysis is presented for both longitudinal and pin fins with vertical orientation of the fin surface. The analysis was carried out on the assumption of a power law fin temperature distribution. Under certain simplified conditions, this optimization model has been validated. Results obtained from the model are also compared with previously published results for the specific set of designed conditions. From optimization study, practical fin profiles are found under the condensation of quiescent vapor atmosphere.     

直线等离子体装置中氩等离子体热负荷特性研究

利用自建的单阴极直流弧光放电直线等离子体装置研究了氩等离子体的稳态热负荷特性,拟为研究等离子体性质、及其与壁材料相互作用提供一定的参考。研究表明,实验中产生的氩等离子体热负荷可达0.5 MW/m2,能持续稳定放电5h以上;氩等离子体热负荷与输入功率成正比,热效率随输入功率的增加而增大;等离子体热负荷强烈依赖于磁场和气体流量,磁场越强、流量越高热负荷越大;同时,增加气体流量或增强磁场,均可显著提高等离子体热效率。通过测量相同条件下距离阳极等离子体喷口215和430mm处的热负荷发现,两处热负荷相差2倍,表明在轴向上热负荷与距离成反比。     

水流量对空气源热泵热水器性能的影响

通过对空气源热泵热水器的性能进行实验研究,测试了水流量对热泵热水器性能的影响。实验结果表明：水流量对加热时间、能效比等性能有一定的影响,这种影响随着流量偏离正常值而加剧;设计适当的水流量,不但可以适当提高热泵热水器的能效比（COP）,而且降低了冷凝器进出口水的温差值和排气压力。