The thermal conductivity of liquid 1,1,1,2-tetrafluoroethane (HFC 134a)

The thermal conductivity of HFC 134a was measured in the liquid phase with the polarized transient hot-wire technique. The experiments were performed at temperatures from 213 to 293 K at pressures up to 20 MPa. The data were analyzed to obtain correlations in terms of density and pressure. This study is part of an international project coordinated by the Subcommittee on Transport Properties of Commission 1.2 of IUPAC, conducted to investigate the large discrepancies between the results reported by various authors for the transport properties of HFC 134a, using samples of different origin. Two samples of HFC 134a from different sources have been used. The thermal conductivity of the first sample was measured along the saturation line as a function of temperature and the data were presented earlier. The thermal conductivity of the second one, the round-robin sample was measured as a function of pressure and temperature. These data were extrapolated to the saturation line and compared with the data obtained, previously in order to demonstrate the importance of the sample origin and their real purity. The accuracy of the measurements is estimated to be 0.5%. Finally, the results are compared with the existing literature data.     

A Study of Schemes for Internet Data Transmission Based on CATV Networks

1　ＴｈｅＣａｕｓｅｏｆｔｈｅＰｒｏｂｌｅｍＴｈｅＣＡＴＶｎｅｔｗｏｒｋｈａｓｂｅｅｎｄｅｖｅｌｏｐｅｄｒａｐｉｄｌｙｉｎｔｈｅｐａｓｔｆｅｗｙｅａｒｓ.Ｂｙｔｈｅｅｎｄｏｆ 1 998,ｔｈｅｃｏｎ ｓｕｍｅｒｓｈａｄｒｅａｃｈｅｄ 6 70ｍｉｌｌｉｏｎ ,ａｎｄｂｙｔｈｅｅｎｄｏｆｌａｓｔｃｅｎｔｕｒｙ ,ｔｈｅｃｏｎｓｕｍｅｒｓｒｅａｃｈｅｄ 85 0ｍｉｌｌｉｏｎ .Ｍｏｒｅｏｖｅｒ,ｔｈｅｎｕｍｂｅｒｏｆｃｏｎｓｕｍｅｒｓｗｉｌｌｂｅｍｏｒｅｔｈａｎ 1 0 0 0ｍｉｌｌｉｏｎ ,ａｎｄｔｈｅＣＡＴＶｎｅｔｗｏｒｋｗ…     

有线电视双向网络设计和回传调试

较详细阐述了有线电视双向网络光节点的设置,电缆干线网、用户分配网的设计等问题,最后介绍了回传调试的有关操作事宜。     

EPON在广电HFC网络双向改造建设中的应用

介绍了有线电视网络几种传统双向改造技术后,研究了如何将EPON这种基于以太网的无源光网络技术应用到有线电视HFC网络改造中,以最低的代价实现传统HFC网络的双向改造,同时指出了在应用中应该注意的几点问题,为当前及今后我国有线电视网络双向建设开辟了一条网络发展新路。     

萃取精馏在ODS替代品纯化工艺中的应用进展

介绍了萃取精馏技术在HFC-32、HFC-134a、HFC-152a、HFC-125、HFC-245fa等ODS替代品纯化中的应用进展。     

Use of nanoparticles to make mineral oil lubricants feasible for use in a residential air conditioner employing hydro-fluorocarbons refrigerants

The application of nano-fluids in refrigerating systems is considered to be a potential way to improve the energy efficiency and reliability of HVAC&R facilities and to make economic the use of environment-friendly refrigerants. In this paper, we report a method that uses nanoparticles to enhance the energy efficiency of retrofitted residential air conditioners (RAC) employing HFCs as alternative refrigerants. The reliability and performance of RAC with nanoparticles in the working fluid have been investigated experimentally. A new mineral-based nano-refrigeration oil (MNRO), formed by blending some nanoparticles (NiFe₂O₄) into naphthene based oil B32, was employed in the RAC using R410a as refrigerant. A method showing how to disperse the NiFe₂O₄ nanoparticles in the mineral oil refrigeration lubricants is presented together with an investigation of their stability. The solubilities of the new MNRO in R134a, R407C, R410a and R425a were measured. The performances of the RAC, such as the cooling/heating capacity, the power input and the energy efficiency ratio, were determined. The results indicate that the mixture of R410a/MNRO works normally in the RAC. The cooling/heating EER of the RAC increased about 6% by replacing the Polyol-Easter oil VG 32 lubricant with MNRO.     

高带宽业务需求与宽带网络的演进

文章首先分析了中国、国外宽带接入的发展现状,然后分析各种宽带业务对网络带宽的要求,并结合公众客户、政企客户的带宽需求,对目前主要的固网宽带接入技术进行了分析与比较,指出带宽需求与网络能力的辩证关系;提出网络能力应适度超前用户的带宽需求;最后总结了推动宽带发展的思路。     

HFC网络技术研究

当前，经过HFC(光纤同轴混合)／CATV(有线电视)网络传送高比特率信息流到用户的通信系统正快速发展着，作为因特网的接入媒介，HFC／CATV网络近来更加普及了。这种网络由一个中央执行系统，一个CMTS(电缆调制解调器终端系统)和数百个CM(电缆调制解调器)组成，通过它们，用户可将自己的计算机连入网络中。为此较详细地分析和研究了HFC网络传输技术及其应用前景。     

EPON在县级广电网络改造中的应用

介绍如何利用EPON技术进行县级有线电视网络的双向化改造,并在改造的过程中少走错路、弯路,最终推动有线电视网络向FTTH网络发展.     

有线电视用户收费综合管理系统

详细介绍了黑龙江鸡西市有线电视收费管理系统。