低温混合工质池核沸腾换热研究

随着 J- T(焦耳汤姆逊效应 )节流制冷机的发展 ,需要对混合工质进一步研究。文中介绍了几种主要的沸腾换热机理 ,指出沸腾换热研究的难点和发展方向 ;并分析了混合工质沸腾换热系数低于相应纯质的原因 ;最后列举了几种通用的混合工质沸腾换热关联式     

Hybrid micro-nano structured thermal interfaces for pool boiling heat transfer enhancement

Boiling heat transfer from hybrid micro-nano structured thermal interfaces has been studied experimentally using PF5060 and deionized water as working fluids for the range of saturation temperatures T_sat between 35 °C and 60 °C. Various enhancement structures were fabricated using surface micromachining in silicon. The performance of the smooth and roughened silicon surfaces, bare and fully coated with carbon nanotubes (CNTs), the silicon-etched as well as CNTs-based pin-fin arrays, and the 3D microstructures have been studied in detail. The highest heat fluxes were obtained using the 3D microstructure without CNTs—these are 27 and 130 W/cm² for PF5060 and water, respectively. Experimental results indicate that use of the CNT-enabled, purely nano-structured interfaces appear to improve boiling heat transfer only at very low superheats, as compared to the smooth surfaces.     

MSC Pool组网方案的研究

随着GSM网络规模的扩大,核心网网元数目的增多,核心网控制节点以池组方式工作是移动通信网络技术的发展趋势,并能简化运营商网络规划建设。为此,我们结合近年来各电信运营商业务的发展,拓展MSC Pool在未来网络发展中的应用,以求更好地发挥MSC Pool的安全性能,并能为我们的通信设计提供必要的帮助。     

Interactions between bubble formation and heating surface in nucleate boiling

The heat transfer and bubble formation is investigated in pool boiling of propane. Size distributions of active nucleation sites on single horizontal copper and steel tubes with different diameter and surface finishes have been calculated from heat transfer measurements over wide ranges of heat flux and selected pressure. The model assumptions of Luke and Gorenflo for the heat transfer near growing and departing bubbles, which were applied in the calculations, have been slightly modified and the calculated results have been compared to experimental investigations by high speed video techniques. The calculated number of active sites shows a good coincidence for the tube with smaller diameter, while the results for the tube with larger diameter describe the same relative increase of the active sites. The comparison of the cumulative size distribution of the active and potential nucleation sites demonstrates the same slope of the curve and that the critical radius of a stable bubble nuclei is smaller than the average cavity size.     

Experimental investigation in pool boiling heat transfer of ammonia/water mixture and heat transfer correlations

The nucleate pool boiling heat transfer coefficient of ammonia/water mixture was investigated on a cylindrical heated surface at low pressure of 4-8 bar and at low mass fraction of 0 < x_NH3 < 0.3 and at different heat flux. The effect of mass fraction, heat flux and pressure on boiling heat transfer coefficient was studied. The results indicate that the heat transfer coefficient in the mixture decreases with increase in ammonia mass fraction, increases with increase in heat flux and pressure in the investigated range. The measured heat transfer coefficient was compared with existing correlations. The experimental data were predicted with an accuracy of ±20% by the correlation of Calus&Rice, correlation of Stephan-Koorner and Inoue-Monde correlation for ammonia/water mixture in the investigated range of low ammonia mass fraction. The empirical constant of the first two correlations is modified by fitting the correlation to the present experimental data. The modified Calus&Rice correlation predicts the present experimental data with an accuracy of ±18% and the modified Stephan-Koorner correlation with an accuracy of ±16%.     

Total Syntheses of Xiamycins A,C, F,H and Oridamycin A and Preliminary Evaluation of their Anti‐Fungal Properties

Divergent and enantiospecific total syntheses of the indolosesquiterpenoids xiamycins A, C, F, H and oridamycin A have been accomplished. The syntheses, which commence from (R)‐carvone, employ a key photoinduced benzannulation sequence to forge the carbazole moiety characteristic of these natural products. Late‐stage diversification from a common intermediate enabled the first syntheses of xiamycins C and F, and an unexpected one‐pot oxidative decarboxylation, which may prove general, led to xiamycin H. All synthetic intermediates and the natural products were tested for anti‐fungal activity. Xiamycin H emerged as an inhibitor of three agriculturally relevant fungal pathogens.     

Enhanced heat transfer in confined pool boiling

We report the results of an experimental investigation of the heat transfer during nucleate boiling on a spatially confined boiling surface. The heat flux as a function of the boiling surface temperature was measured in pool boiling pots with diameters ranging from 15 mm down to 4.5 mm. It was found that a reduction of the pool diameter leads to an enhancement of the nucleate boiling heat flux for most of the boiling curve. Our experimental results indicate that this enhancement is not affected by the depth of the boiling pot, the material of the bounding wall, or the diameter of the inlet water supply. High-speed camera imaging shows that the heat transfer enhancement for the spatially confined pool boiling occurs in conjunction with a stable circulating flow, which is in contrast to the chaotic and mainly upward motion for boiling in larger pool diameters. An explanation for the enhancement of the heat transfer and the associated change in flow pattern is found in the singularisation of the nucleate boiling process.     

MSC Pool技术在实际组网中的优势和问题

在3GPPR5中（3GPPTS23．236）规定了核心网控制节点（MSS,SGSN等）以池组方式工作的机制,打破了以往BSC／RNC与MSS之间一对一的控制关系。本文简要阐述了MSC Pool组网技术的原理、组网结构、实现方式、在实际组网中带来的优势,分析了网络实际应用效果以及存在的不足和待解决的问题。     

MSC Pool技术中NNSF的部署方式

本文首先介绍了MSC Pool的技术原理与组网优势,然后对MSC Pool技术中NNSF的两种部署方式做了重点阐述,说明了由MGW代理实现NNSF的信令组网方式,并且介绍了一种比较可行的组网实现方案。