Experimental study of the gravity effect on the distribution of refrigerant flow in a multi-pass condenser

Gravity in multi-pass condensers affects the refrigerant flow rate distribution, owing to the gravitational pressure drop that occurs mainly in the U-bend tubes in fin and tube condensers with horizontal tubes. This effect was studied using an experimental approach. A condenser with two ‘nU’ circuits was selected, and the temperature variation of the refrigerant side was measured and compared along each circuit. The critical air velocity, which indicated the initiation of the gravity effect, was found for a given refrigerant flow rate. As the air velocity increased beyond the critical air velocity, the gravity effect (or mal-distribution of the refrigerant flow) developed further. Similarly, the critical refrigerant flow rate was also determined for a given air velocity. As the refrigerant flow rate decreased below the critical refrigerant flow rate, the gravity effect also developed further. The gravity-affected region was shown in the table with rows of air velocities and columns of refrigerant flow rates, and expressed using a single parameter for a given refrigerant flow circuit.     

Effect of Rare Earths on Corrosion Resisting Properties of Carbon-Manganese Clean Steels

Rareearthelementshavesignificantactionsinsteels ,includingwipingoffimpurityelements ,trans modifyinginclusions ,andimprovingmicrostructureetal,soaddingappropriaterareearthsintosteelscanef fectivelyimprovetheircorrosionresistingproper ties[1,2 ] .Todaypuri…     

Investigation of Structure and Hydriding Properties of La0.6 Nd0.4 Ni4.8 Mn0.2 Cux Alloys

The structure and hydriding performance of La0.6Nd0.4Ni4.8Mn0.2Cux (x = 0 ～ 0.4) alloys were investigated in order to develop suitable materials for metal hydride air conditioner. The effect of Cu addition on the crystal structure,equilibrium pressure, hydrogen capacity and hysteresis as well as hydrogen absorption/desorption kinetics were systematically studied by using the measurement of P-C isotherms, X-ray diffraction and scanning electron microscopy. As the amount of Cu increases, the plateau pressure increases and hydrogen absorption/desorption kinetics is improved, but the effective hydrogen storage capacity decreases. It is shown that variations in the basal plane parameter a can be used as an indication for the plateau pressure changes. With the increase of parameter a, the plateau pressure decreases. For La0.6 Nd0.4Ni4.8Mn0.2Cux(x = 0 ～ 0.4) alloys there is a relationship between the effective hydrogen storage capacities and the ratios of their unit cell parameters c and a. The effective hydrogen storage capacity decreases with increase of a/c.     

新一代顺序式X射线荧光光谱仪——飞利浦PW2400型X射线荧光光谱仪

介绍了飞利浦ＰＷ２４００型新的Ｘ射线荧光光谱仪，它采用了多种新技术，包括脱Ｘ射线管（ＳＳＴ），直读光学定位传感器（ＤＯＰＳ）多道分析器（ＭＣＡ）及新的窗式软件。     

4A和13X分子筛去除水中重金属Cd2＋及其吸附性能研究

以4A和13X分子筛为吸附材料,考察废水pH值和Cd2＋初始浓度等对Cd2＋去除率的影响,并研究了分子筛对Cd2＋的吸附性能。结果表明,4A和13X分子筛投加量为0．16 g/L、废水pH值为5、Cd2＋浓度为20 mg/L时,Cd2＋去除率达到95％以上;分子筛对Cd2＋的去除机理以离子交换吸附为主,交换出来的Na＋与分子筛吸附的Cd2＋摩尔浓度比为2;在吸附热力学和动力学方面,4A和13X分子筛均符合Langmuir吸附等温模型和Lagergren二级速率方程,计算的饱和吸附容量 Q0分别为150．15、163．67 mg/g ,二级反应速率常数K2分别为2．45＆#215;10-3、3．96＆#215;10-4 g/（mg ＆#183; s）。该吸附反应是一种单分子层反应速度较快的化学吸附过程。     

Experimental investigation and numerical simulation of large-sized aluminum tube extrusion forming

Large-sized aluminum tube has big section effect, aspect ratio and thin thickness, so that the extrusion technology is complex and the large specific pressure is generated in extrusion cavity. The temperature variation and velocity effect is difficult to control. The extrusion forming of large-sized aluminum tube was researched and simulated. Three-dimensional thermo-mechanical coupled finite element model was constructed and appropriate boundary conditions were given out. The results show that large-sized aluminum tube can be formed by isothermal extrusion through controlling the extrusion velocity and founding the relationship between extrusion velocity and extrusion temperature.     

包钢无缝厂轧管机辊缝伺服系统的调试

在原有轧管机管壁人工控制的基础上 ,引入液压伺服系统及自反馈控制 ,完成对管壁轧制的自动控制     

金属铕制备工艺的研究

本文采用正交实验的方法,研究了金属铕的制备工艺条件。实验结果表明,还原－蒸馏温度１１００℃,还原剂过量系数０．３,保温时间１．５小时,金属铕的纯度大于９９．９％,直收率大于９０％     

液态金属实验回路(LMEL)的总体设计和运行

液态金属实验回路（ＬＭＥＬ）是国内唯一用于聚变堆磁流体动力学（ＭＨＤ）效应和材料相容性研究的大型实验装置。与国外同类先进的装置相比，回路流程和运行方式均有重大改进，使其更先进、安全并具有多功能。回路运行分为两个阶段：第一阶段以钠－钾低共熔合金（２２Ｎａ７８Ｋ）为工质，研究ＭＨＤ效应，ＬＭＥＬ的最大哈特曼（Ｈａｒｔｍａｎｎ）数Ｍ和相互作用参数Ｎ分别为０．７５×１０４和２．５×１０４；第二阶段以液态锂为工质，研究结构材料与锂的相容性，最高温度和流速分别为５２０℃和１．３８ｍ／ｓ。