不可逆布雷顿制冷循环的有限时间热力学分析

研究定常态流恒温热源和变温热源不可逆布雷顿制冷循环的有限时间热力学性能，并讨论了工质与热源间的最佳匹配和非共沸工质循环的优化问题。所得结果对实际制冷工程有一定指导意义。     

应用于钠冷快堆的超临界二氧化碳布雷顿循环系统

为了满足系统经济性和安全性的,在快堆技术的发展过程中,涌现出许多先进技术概念。在众多先进技术当中,超临界二氧化碳布雷顿循环系统被认为是最具应用前景的能量传输技术之一。文章基于超临界二氧化碳布雷顿循环,结合我国快堆的特点和需求,探讨超临界二氧化碳(S-CO2)在我国钠冷快堆技术研发中潜在的应用可行性。     

费米气体布雷顿制冷循环的性能分析

基于理想费米气体的状态方程，建立以理想费米气体^3He为工质的布雷顿制冷循环模型，导出循环的输入功、制冷系数和制冷量等重要参数的普遍表达式。对几种有趣的情况作了详细的讨论。确定了布雷顿制冷循环正常运行的压强比界限。     

逆布雷顿循环空气制冷机的性能分析

针对开式逆布雷顿循环空气制冷机的热力性能展开理论分析,建立压缩机、膨胀机和回热器3大部件的制冷机系统模型.就部件性能和流程选择、环境温度、制冷温度等系统参数以及压比等设计参数对空气制冷机性能和COP值的影响进行了研究,证明存在着一个最佳的压力比πopt～4使制冷系统的制冷系数最大.提出了进一步提高制冷机效率的改进方案,对系统参数和设计参数进行了优化设计.     

超临界二氧化碳管内流动及换热特性分析研究

通过对超临界二氧化碳管内流动及换热特性研究现状和分析方法介绍,列出常用的超临界二氧化碳在不同条件下的传热和压降关联式,进一步说明自然工质二氧化碳的跨临界循环特点和所具有的独特的热物理性质,指明超临界二氧化碳的利用和新型换热设备的研发方向。     

超临界二氧化碳发泡热硫化硅橡胶的研究

对超临界二氧化碳制备硅橡胶泡沫材料的可行性进行了研究.采用“预硫化—发泡—完全硫化”工艺,研究了发泡温度、压力、溶胀时间、卸压时间等对硅橡胶泡沫的密度和泡孔结构的影响,通过扫描电子显微镜(SEM)对泡孔结构进行了分析.结果表明:利用超临界二氧化碳发泡热硫化硅橡胶,得到了泡孔孔径小(＜ 100μm)、泡孔均匀、泡孔结构可...     

超临界二氧化碳循环发电技术应用

超临界二氧化碳循环可应用于火力发电、核能发电、太阳能热发电等多种发电技术领域,作为新型的动力循环系统替代目前广泛使用的汽轮发电机组或燃气轮机发电机组。在进入商业化应用之前,需要对超临界二氧化碳循环技术在各种应用场景下的优势及其潜在的社会和经济效益进行探讨。通过分析超临界二氧化碳循环的特点和优势,探索其与化石能源、核能、太阳能、生物质能、余热等各种热源相结合的可行性,提出多种发电系统方案,可为今后超临界二氧化碳循环的商业化应用提供参考。随着超临界二氧化碳循环技术不断成熟,设备成本进一步降低,其系统简化、结构紧凑、效率高等优势将更加突显。     

磁布雷顿制冷循环性能的优化分析

基于统计力学的性质推导出了顺磁系统的热力学关系,并构建了以满足居里定律的顺磁材料为工作物质的一般磁布雷顿制冷循环模型。研究了内不可逆性和传热不可逆性对循环优化性能的影响。根据该循环模型,推导出了循环的各种优化关系并深刻讨论了循环的性能特性,所得结果将有助于实际的磁制冷机的优化设计和应用。     

一类回热式布雷顿制冷循环的有限时间热力学性能

研究了恒温热源条件下具有等熵压缩、膨胀过程的闭式回热式布雷顿制冷循环的有限时间热力学性能。导出循环制冷率、制冷系数与循环压比的关系，由此得到最佳制冷率、制冷系数的特性。     

逆布雷顿循环空气制冷机的(火用)分析

从Yong的角度分析了逆布雷顿循环空气制冷系统的Yong损失，建立了空气制冷机各部件的Yong损失模型，计算出了空气制冷机的Yong效率，提出了提高效率、节约能源的措施。     

超临界二氧化碳流动和换热研究进展

综述了国际上对超临界二氧化碳管内换热和压降特征的研究。提供了多种公开发表的超临界流体在冷却工况下的换热关联式及单相压降关联式,将实验关联式的计算结果与文献中的实验数据进行对照,在此基础上对关联式的准确性进行了讨论。同时指出了现有研究内容的不足。     

超临界二氧化碳微细管内冷却换热研究

对超临界二氧化碳在微细竖直圆管内冷却条件下的对流换热进行了数值模拟研究,分析了不同管径、进口雷诺数及不同的热流率对超临界二氧化碳对流换热的影响,考察管内局部流体温度、湍动能、湍流雷诺数的变化。湍流模型采用低雷诺数YS模型。研究表明,在临界温度区域比较大的截面,超临界二氧化碳局部传热系数达到最大值,同时管内传热受湍流雷诺数影响较大。     

Effect of lubricating oil on cooling heat transfer of supercritical carbon dioxide

In this research, the cooling heat transfer coefficient and pressure drop of supercritical CO₂ with PAG-type lubricating oil entrained were experimentally investigated. The inner diameter of the test tubes ranged from 1 to 6 mm. The experiments were conducted at lubricating oil concentrations from 0 to 5%, pressures from 8 to 10 MPa, mass fluxes from 200 to 1200 kg m⁻² s⁻¹, and heat fluxes from 12 to 24 kW m⁻².In comparison to the oil-free condition, when lubricating oil entrainment occurred, the heat transfer coefficient decreased and the pressure drop increased. The maximum reduction in the heat transfer coefficients—about 75%—occurred in the vicinity of the pseudocritical temperature. The influence of oil was significant for a small tube diameter and a large oil concentration. From visual observation, it was confirmed that this degradation in the heat transfer was due to the formation of an oil-rich layer along the inner wall of the test tube. However, when the oil concentration exceeded 3%, no further degradation in the heat transfer coefficient could be confirmed, which implies that the oil flowing along with CO₂ in the bulk region does not influence the heat transfer coefficient and the pressure drops significantly. For a large tube at a lower mass flux, no significant degradation in the heat transfer coefficient was observed until the oil concentration reached 1%. This is due to the transition of the flow pattern from an annular-dispersed flow to a wavy flow for a large tube, with CO₂ flowing on the upper side and the oil-rich layer on the lower side of the test section.     

Thermodynamic analysis of different two-stage transcritical carbon dioxide cycles

The aim of this paper is the thermodynamic evaluation and optimisation of different two-stage transcritical carbon dioxide cycles. Five different cycles are studied: basic single-stage cycle, single-throttling with two-stage compression cycle, split cycle, phase separation cycle and single-stage cycle coupled with a gas cooling circuit. Each basic cycle is analysed for the effect of internal heat transfer between different streams of refrigerants. In the case of two-stage compression, intermediate cooling between the compressor stages is present. An analysis on the Plank cycle for intermediate pressure higher than critical one is performed. Each cycle is optimised with regards to energy performance, calculating the optimal values of both the upper and the intermediate pressures. In the case of split cycle, the ratio of the mass flow rate in the main stream to the one in the auxiliary stream is also optimised.     

超临界二氧化碳水平管内层流混合对流换热数值模拟

为得到二次流对换热的强化作用,对恒壁温冷却工况下,超临界二氧化碳在水平微细圆管内的混合对流换热进行了数值模拟。分析了重力水平、冷壁面温度、入口雷诺数Re等参数变化时管道壁面的传热系数,管内浮升力引发的二次流、范宁摩擦系数沿管道的变化规律,引入相对二次流动能将二次流的强度定量表示出来。研究发现管内流体顶部温度高于底部,上母线传热系数远高于下母线且在超临界二氧化碳的拟临界温度附近达到峰值,二次流及范宁摩擦系数在入口区域变化最剧烈,重力加速度对管内流场产生重要影响。     

Comparison between supercritical carbon dioxide extraction and aqueous surfactant washing of an oily machining waste.

Mathematical models are developed to compare aqueous surfactant washing to supercritical carbon dioxide (SCCO2) extraction. These two cleaning processes are potentially competitive technologies which can be used to remove oily contaminants from a solid waste. In both processes, the cleaning efficiency for a batch of waste is evaluated by quantifying the residual oil content in the treated sample. A mass transfer model is used to simulate a semi-continuous washing process, and the experimental data, obtained in a batch operation, are used to estimate the equilibrium parameters in the model. For SCCO2 extraction, a linear desorption model is used to describe the supercritical desorption of oil from the solid phase into the CO2 phase and the simulated results agreed very well with the experimental data. The oil removal in aqueous surfactant washing is viewed to be controlled primarily by the diffusional transport of oil from the interiors of the waste elements to the surface, thus, it can be significantly affected by the size of the particles. A pre-cleaning pulverization is then recommended to improve the cleaning efficiency without increasing any other operation costs. In SCCO2 extraction, the desorption of oil from the solid waste is the controlling step and consequently, the solvent flow rate has no influence on oil removal. Our theoretical studies show that the difference between the cleaning efficiencies of these two technologies is not significant, with the oil concentration in the washing products approximately 5% lower than that in the extraction products.     

Drying of silica gels with supercritical carbon dioxide

Results of drying experiments of aerogels with supercritical carbon dioxide are reported. In addition to the results of experiments with a pilot extracting apparatus, a preliminary design is also given of a large-scale supercritical carbon dioxide extraction plant to be used for drying of aerogels. From the experiments it was found that crack-free aerogels could be obtained when drying with carbon dioxide under supercritical conditions. The lowest temperature and pressure at which crack-free aerogel samples were obtained was at 35 °C and 85 bar, respectively. The temperature had a minor influence on the drying time. It was also found that the diffusion of ethanol into the aerogel pores limits the drying time. This limitation implies that the thickness of the aerogel tiles will have a large influence on the cost of drying of an aerogel.     

废水源热回收热泵使用前景分析

本文分析了废热水排放企业和公共浴室的给水和排水现状,.介绍了废水源热回收热泵的工作原理和特点,从不同角度分析了使用废水源热回收热泵的前景和重大意义.