离子液体工质对吸收制冷循环研究进展

综述了近年来离子液体吸收制冷工质对的研究进展,重点介绍了离子液体工质对的种类、离子液体工质对热物性的测量及离子液体工质对的理论吸收制冷循环性能。     

不确定性下基于柔性指数的计算机辅助制冷工质设计

针对工程应用中制冷循环会因环境因素的不确定波动而具有变工况的特点，提出以最大化操作柔性为目标研究最优制冷工质设计的面向操作柔性的过程和工质协同优化方法。该方法在物性预测模型层面，针对现有基团贡献法误差大的问题，修正了基团拆分方法和基团参数；在制冷过程模型层面，针对相态不确定性引入了互补约束；在优化求解层面，提出以柔性指数最大化为目标的制冷工质优化方案，建立以柔性指数最大化为目标的混合整数非线性规划问题。将该方法分别应用于单工质和混合工质设计案例，结果表明，面向环境不确定性的最优工质有别于制冷性能系数最大化的工质。     

混合工质林德节流制冷技术的发展分析

单工质单级蒸汽压缩式制冷循环是目前最成熟的制冷技术,但在低温温区（?40℃以下）具有一定局限性,而混合工质节流制冷技术能够适应不同温区,特别在深低温区极具研究价值。本文介绍了共沸、近共沸及非共沸混合物制冷剂的原理及特点。研究发现,共沸和近共沸混合工质制冷剂与单工质具有相似的性质;单级压缩混合工质制冷机依靠非共沸混合制冷剂的高度温变相变特性实现深度制冷。阐述了一种混合工质林德循环系统（LHR）的国内外发展历史和研究现状,指出LHR经历了开式循环、多级压缩闭式和单级压缩闭式循环3个发展阶段。最后结合混合工质林德循环系统实验,提出了增加风冷预冷器、回热器发泡保温等改进措施及研究优化重点,包括混合工质组分及最佳配比、热物性计算、换热器保温等方面的优化。     

热管废热LiBr制冷机中工质热物性的可视化计算

根据国内外相关资料和作者拟合的公式,采用VisualBasic面向对象的编程技术,开发了废热热管LiBr制冷机工质热物性的可视化程序,方便了人们计算水、水蒸气、LiBr溶液等工质的热物性,满足了废热热管LiBr制冷机的工艺设计和性能模拟的需要,同时本程序还可被调用于其他型号的LiBr制冷机的性能分析及工艺计算。     

氨制冷技术研究进展

氨具有良好的热物性和传输特性,是CFCs与HCFCs理想的替代工质。本文介绍了当今氨在制冷空调领域应用研究的新技术,包括NH₃/CO₂复叠制冷技术、氨用CO₂载冷技术、NH₃冷水机组等,另外,本文还从安全可靠、高效、小型化和自动化等方面阐述了氨制冷技术的发展趋势。我国氨制冷技术的发展较为缓慢,可靠性和先进性与国外差距较大,必须加强氨制冷技术的研发力度,促进我国氨制冷技术的发展。     

使用NH3-LiNO3工质对的增压型回热吸收循环性能分析

近年来,日益增长的暖通空调系统能耗已接近50%的建筑能源消费量。吸收式循环可使用太阳能热能、工业废热等低品位能源产生制冷效果,进而降低夏季制冷负荷对高品味电能的大量需求。当前常用于吸收制冷循环的LiBr-H₂O工质对虽然COP较高,但由于物性限制了其蒸发温度范围以及存在较高的结晶风险,使得系统小型风冷设计存在限制。氨水工质对具有较宽的制冷温区,但由于需要精馏以提高氨气浓度造成COP较低。NH₃-LiNO₃工质对无须增设精馏器,结晶温度远高于LiBr-H₂O,且氨气压力较高适合在耦合压缩机循环以提升循环性能,扩宽运行温区。因此,本研究提出压缩机辅助的增压型回热吸收循环使用NH₃-LiNO₃工质对,并对其进行热力分析,研究压缩机的引入对循环性能的改进作用。结果显示,压缩机辅助作用下循环驱动温度下降至34℃,蒸发温度亦可降低至-34℃,且循环倍率降低了52.16%,更适于小型风冷设计。     

不同制冷剂喷射制冷性能计算分析

引入制冷剂的实际物性,建立了喷射器热力学模型;比较了沸点相近工质在喷射器内的压力和速度变化趋势及喷射系数,探讨了引起喷射器性能差异的主要物性因素;比较了几组具有相近沸点制冷剂的喷射制冷性能。结果表明:对沸点相近的工质来说,一般工作蒸气的比焓值越高,喷射系数越高;沸点相近的工质对中,R717的性能优于R290,R152a优于R134a,R141b优于R123,R142b优于R600a;在研究的所有制冷剂中,R717的制冷性能最好,R152a次之,两者的COP(性能系数)值差随发生温度的升高而增大。     

以降压为目的的CO_2混合工质制冷系统研究进展

自然工质CO_2因其具有良好的环境友好特性(ODP=0,GWP=1)、单位容积制冷量高、良好的传热性能等优点而得到制冷行业的再次关注。然而,由于其自身物性及工况条件的限制,在实际应用中CO_2制冷系统大多采用跨临界循环,高压侧压力高达12MPa左右,这对系统各部件的安全性和制造成本提出非常高的要求。本文总结了目前采用CO_2混合工质来有效改善纯CO_2制冷系统运行压力较高问题的制冷循环系统,综述了国内外以降压为目的的CO_2混合工质制冷系统研究进展,分析了CO_2混合工质的跨临界制冷循环系统、自复叠式制冷系统以及压缩-吸收耦合循环系统各自的特点,指出了以降压为目的的CO_2混合工质制冷系统的发展前景,并对今后的CO_2混合工质制冷系统的主要研究方向进行了讨论。     

乙二醇水溶液用于闭式冷却系统防冻的传热性能研究

闭式水冷却系统在冬季常换用乙二醇水溶液作为防冻的循环工质,由于物性变化,其携热能力和对流换热系数比水都有所下降。本文基于闭塔设计理论,研究了不同浓度的乙二醇水溶液作为闭式冷却塔循环工质在不同季节中对换热的综合影响,提出了采用大管径薄壁管和加大循环工质流量及增加相应通风量等应对方法,并揭示了其在不同运行模式下的变化规律。     

用氨(工质)热功循环回收氨合成反应热

用氨(工质)热功循环可把合成反应热有效地转换成机械功,用于1000t/d 氨厂可回收8.5MW 机械功,此机械功可直接用以驱动制冷压缩机,也可用于发电或其它目的。采用氨(工质)热功循环可节约燃料20%以上,并可提高合成氨系统的经济性和安全性。     

Aspen Plus对Unipol工艺聚乙烯装置回收系统的优化

利用Aspen Plus软件对Unipol工艺聚乙烯装置回收系统进行优化。在受压缩机处理能力、冰机制冷能力和总的冷剂流量的限制条件下,合理分配高低压侧的冷剂流量,得到最大的回收凝液量。同时,提出向冷剂中加入缓蚀剂,减缓冷凝器的腐蚀,保证换热效率。     

真空闪蒸制取冰浆系统(火用)分析

采用已有的计算冷量以及损失的公式,对实验室用真空闪蒸制取冰浆系统进行了(火用)分析。利用EES软件,对真空闪蒸法冰浆制备系统中的4个关键环节(冷水冰水混合、真空室内喷雾闪蒸、捕水器内蒸汽凝结成霜、制冷机制备低温盐水)进行计算,得出各个环节(火用)损失以及整个系统的(火用)效率。结果表明:实验用真空室内喷雾闪蒸环节的(火用)效率较高,捕水器内蒸汽凝结成霜的(火用)效率较低,制冷机组制备低温盐水(火用)效率最低,(火用)损最大,导致整个系统的效率相对较低。为了改善真空闪蒸制取冰浆系统的能耗,应对低温盐水制备环节进行优化或采用其他方式替代该环节。     

注塑模冷却分析系统的研究与开发

介绍了一个注塑模冷却分析软件系统,该系统将图论思想列入冷却介质的流动分析,利用边界元法求解模具三维温度场,实现了冷却管网的自动分析和模具型腔温度场的准确高效预测。     

Two-zone model for combustion of a composite solid propellant with a coolant

A mathematical model for combustion of a propellant with a coolant taking into account the two-zone structure of the combustion front due to condensed- and gas-phase reactions was developed and examined. Formulas for the burning rate, reaction-zone temperature, and burning-rate sensitivity to internal and external parameters of the system were derived in analytical form. The burning rate was examined numerically as a function of pressure, the characteristic size of the system, component content, and thermodynamic and kinetic parameters. Recommendations are given on methods of obtaining particular ballistic properties by varying the initial parameters of the system.     

A thermodynamic approach to calculate the yttria-stabilized zirconia pH sensor potential

Published thermodynamic approaches to calculate the yttria-stabilized zirconia (YSZ) ceramic pH sensor potential are reviewed. A thermodynamic approach related to the Gibbs free energies of reactants and products is proposed to calculate the YSZ pH sensor potential, identify the YSZ pH sensors as primary pH sensors and to determine solution pH at high temperatures. YSZ thimbles have been used with a silver powder internal element prepared in the presence of dry air to generate a redox system, Ag|O₂, sensitive to pH. YSZ (Ag|O₂) pH sensors have been tested over a temperature range of 100 to 300 °C in lithiated boric acid solutions which are related to pressurized water reactor coolant chemistry. The test results have good agreement with the thermodynamic calculation from 100 to 300 °C. The thermodynamic calculation can be applied to a variety of YSZ pH sensor internal elements including Cu|Cu₂O, Hg|HgO, Ag|Ag₂O, Ag|O₂, whereas earlier published calculations are not generally applicable.     

基于Aspen-Plus的化工热力学教学(Ⅰ)均相性质计算

化工热力学作为化学工程的基础学科,是化学工程与工艺专业的一门核心课程,在化学工程的教学过程中占有极其重要的地位。借助专业化工模拟软件Aspen-Plus完成化工热力学教学中的相关性质计算,可以得到较为理想的结果,为加强应用能力培养提供了基础。     

FactSage Thermodynamic Database for Steelmaking Refractory Research

Thermodynamic databases are very useful to analyze the complex chemical reactions happening in high temperature material processes. An accurate thermodynamic database based on physically sound thermodynamic models can provide thermodynamic calculations of useful phase diagrams and comprehensive chemical reactions related to refractory corrosion in steelmaking processes. In this study,the FactS age thermodynamic database,one of the most comprehensive thermodynamic databases for oxide systems among other commercial software,is reviewed in particular for the steelmaking refractory research,and several applications to refractory corrosion are presented.     

Buoyancy‐driven Mixing Studies of Natural Circulation Flows using Rossendorf Coolant Mixing Model Experiments and CFD

Coolant mixing in the cold leg, downcomer and the lower plenum of pressurized water reactors is an important phenomenon mitigating the reactivity insertion into the core. Therefore, mixing of the deborated slugs with the ambient coolant in the reactor pressure vessel was investigated at the four loop 1:5‐scaled Rossendorf Coolant Mixing Model (ROCOM) mixing test facility. Thermalhydraulics analyses showed that weakly borated condensate can accumulate in particular in the pump loop seal of those loops, which do not receive safety injection. After refilling of the primary circuit, natural circulation in the stagnant loops can re‐establish simultaneously and the deborated slugs are shifted towards the reactor pressure vessel. In the ROCOM experiments, the length of the flow ramp and the initial density difference between the slugs and the ambient coolant was varied. From the test matrix experiments with 0 and 2 % density differences between the deborated slugs and the ambient coolant were used to validate the CFD software ANSYS CFX. To model the effects of turbulence on the mean flow a higher order Reynolds stress turbulence model was employed and a mesh consisting of 6.4 million hybrid elements was utilized. Only the experiments and CFD calculations with modeled density differences show stratification in the downcomer. Depending on the degree of density differences the less dense slugs flow around the core barrel at the top of the downcomer. At the opposite side the lower borated coolant is entrained by the colder safety injection water and transported to the core. The validation proves that ANSYS CFX is able to simulate appropriately the flow field and mixing effects of coolant with different densities.     

Achieving higher accuracies for process simulations by implementing the new reference equation for natural gases

For efficient design and operation of technical processes, accurate simulations are essential. Therefore, a precise representation of thermophysical properties using an adequate thermodynamic model is necessary. The GERG-2008 (Kunz et al., 2007, Kunz and Wagner, submitted for publication) is the new reference equation of state for natural gases consisting of up to 21 specific compounds. As the equation of state describes the gas and liquid phase as well as the super-critical region and the vapour–liquid equilibrium with the highest accuracy available, it has high potential for accurate process-modeling. In order to implement the software available for the new equation into various common simulation tools, the GERG-2008 Property Package has been developed, which complies with the CAPE-OPEN standards specification. The influence of thermodynamic models on the simulation of the only liquefaction plant for natural gas existing in Europe is investigated. Results show significant improvements in accuracy for simulations using the new thermodynamic model.     

冷媒液用缓蚀剂的研制

通过复配实验筛选出一种不含NO2-的复配缓蚀剂,失重法实验表明,钢、铝、铜在含缓蚀剂的乙醇冷媒液中的腐蚀速度明显降低,当缓蚀剂浓度达到1.3%时,腐蚀速度近乎为零,有效地抑制了碳钢、紫铜和铝合金材料在冷媒液中的腐蚀,同时提高了冷媒液的沸点,改善了冷媒液的稳定性。