两级蒸发对跨临界CO_2引射制冷系统影响的实验研究

两级蒸发引射制冷循环中通过二级蒸发器不仅能调节引射器出口干度还能提高系统效率。通过改变第二蒸发器冷冻水流量对两级蒸发引射制冷系统进行实验研究,并与改变引射器面积比的调控效果进行比较。结果表明:在实验工况范围内,气冷器压力、第一蒸发器压力和压缩机流量都随第二蒸发器冷冻水流量的增加而增大;而且引射器面积比越大,气冷器压力越高而蒸发器压力和压缩机流量越低。同时,系统引射系数随第二蒸发器冷冻水流量的增加而降低,而制冷量和COP则升高,尤其是在小引射系数下,系统制冷量和COP提高的更为明显。本研究为引射循环提供了另外一种良好的调控思路。     

基于极大滴法的两级隔振系统的优化设计

本文研究了两级隔振系统的参数优化设计，利用大滴方法处理不可微优化问题，实例计算表明，该方法具有比较的效果，本文对从事隔振设计的研究人员有一定的指导意义。     

多柔体系统动力学部件两级降阶响应分析

利用传统的模态综合法进行多柔体系统动力学建模时,没有考虑到控制系统设计技术的承受能力和激励的特点,保留的大量低频子结构模态对于整体控制目标没有贡献,反而加大了组合的整体方程的复杂程度．因此,为考虑部件级的降阶,可以在传统的部件组合之前,对部件模态坐标独立变换处理,去掉系统中弱能控和弱能观部分,而剩下的模态仍可使后继分析有必要的精度,从而建立降阶的动力学方程．     

两级压缩式热泵空调与冰箱复合系统

根据两级压缩式制冷原理和热泵空调与冰箱制冷系统运行工况的不同,提出一种新型两级压缩式热泵空调与冰箱复合系统,介绍其原理及不同工况模式下的实现方式。该系统将热泵空调系统与冰箱系统冷热量相互有效利用,具有节能效果。对一个应用实例进行数值模拟,结果表明：复合系统能耗与常规的各自独立系统的总耗能相比,冬季节能约9％,夏季节能约18％。     

基于极大熵法的两级隔振系统的优化设计

本文研究了两级隔振系统的参数优化设计，利用极大熵方法处理不可微优化问题；实例计算表明，该方法具有比较好的效果。本文对从事隔振设计的研究人员有一定的指导意义。     

两级冷凝热泵热水系统的实验研究

空气源热泵热水器运行在高温工作区时,压缩机功率及压缩机排气温度往往偏高,这不仅给机组的安全稳定性带来了隐患,同时系统的效率也会明显下降。针对这一问题,文中提出了一种两级冷凝热泵热水系统以及相应的控制方式,并进行了实验。实验结果表明,与传统的热泵热水器相比,这一系统不仅能提高供水温度,而且能让热泵热水机组在高温工作区的冷凝温度相对较低,从而在提高供水温度的同时,有效的降低了机组最高压缩机功率以及最高压缩机排气温度,系统运行安全、可靠、高效。     

超滤膜用于反渗透的前置处理

介绍了内压式中空毛细管超滤膜技术用于反渗透进水前置处理的特点、工业应用情况和其经济效益．     

催化剂复配和氧化剂的加入方式对Fenton氧化体系的影响研究

以1000mg/L的苯酚溶液为底物,通过比较采用不同催化剂时的氧化效果,发现将Fe3+和Fe2+混合作为催化剂使用,能减少Fe2+的损失,提高催化剂的利用率,提高H2O2的利用率,从而提高Fenton体系的氧化能力。同时发现采用逐渐滴加H2O2的方式,能减少50%催化剂的用量,同时保持良好的氧化效果,使COD的去除率达到80%左右。     

Cu2ZnSnS4-CdS复合材料的制备及其在光催化制氢中的应用

为了进一步提高Cu₂ZnSnS₄的光催化制氢性能,首先通过水热法制备出Cu₂ZnSnS₄光催化材料,在此基础上加入Cd（CH₃COO）₂·2H₂O和Na₂S进行二次水热反应制备Cu₂ZnSnS₄-CdS复合材料。通过XRD、SEM、TEM、Raman及XPS等分析测试方法对Cu₂ZnSnS₄-CdS复合材料的物相结构、微观形貌和元素价态进行了表征。结果表明:成功制备了结晶性能较好的Cu₂ZnSnS₄-CdS复合材料。Cu₂ZnSnS₄-CdS复合材料是由球状和块状颗粒组成;Cu₂ZnSnS₄-CdS复合材料表面>95%的Cd和S原子（原子比为1:1）的存在说明块状颗粒Cu₂ZnSnS₄表面生长的球形颗粒为CdS;在氙灯下的光催化制氢性能表明,Cu₂ZnSnS₄-CdS复合材料的光催化制氢效果明显优于Cu₂ZnSnS₄和CdS,产氢效率为296.17 μmol（g·h）-1。      

Effect of tin addition on corrosion behavior of a low-alloy steel in simulated costal-industrial atmosphere

The effect of tin addition on the atmospheric corrosion behavior of a low-alloy steel in simulated coastal-industrial atmosphere has been investigated by indoor wet/dry cyclic corrosion test (CCT). The results indicate that tin addition can obviously make the steel substrate more resistant to atmospheric corrosion by suppressing the cathodic H⁺ reduction reaction, and but tin addition is not of obvious beneficial effect when the steel is covered with a thicker rust layer during long-term corrosion process. The reason lies in the fact that the presence of un-reduced H⁺ can lower the electrolyte pH value and lead to a loose and porous rust layer on tin-containing steel sample than that on tin-free steel sample. In addition, the 120 CCT cycles corrosion process of the two steels can be divided into three stages. Both the tin-free and tin-containing steels show an increasing corrosion rate during the initial corrosion stage and then exhibit a decreasing corrosion rate during the second and third corrosion stages. Moreover, tin addition makes the tin-containing steel rust layer have a higher amount of α-FeOOH and lower amount of γ-FeOOH and Fe₃O₄ than the tin-free steel rust layer.     

火电厂中水回用RO膜污染特征研究

城市污水深度回用为火力发电厂锅炉补给水已成为世界各国解决缺水问题的主要方案之一,中水水质对深度回用工艺中反渗透膜的影响不容忽视.将电厂中水回用工程中污染的反渗透膜组件进行解剖分析,通过加压染料试验、表观观察、烧失量分析、SEM-EDX、GC-MS等方法对膜面污染物及其在膜面的分布特征进行研究.结果表明,膜面主要为有机污染,主要污染物为烃类、脂肪酸类物质;少量无机污染主要是SiO2;污染物总量沿从膜卷进口端到出口端的方向逐渐增多,无机污染的变化与之相同,而有机污染的变化与之相反.表明阻垢和杀菌预处理系统及维护管理工作完善.     

镁的添加对制备泡沫铝夹芯板泡孔稳定性的影响

通过粉末-铝板复合轧制方法制备出一种界面为冶金结合的泡沫铝夹芯板.分别采用对发泡剂的处理和添加Mg元素的方法来提高芯材泡沫的稳定性.研究发现只有同时对发泡剂处理以及添加Mg元素才能够提高泡沫的稳定性.研究了此种方法中重要的泡沫稳定机制,Mg元素的添加改善了铝硅合金粉末原料生产过程中产生的氧化物颗粒在孔壁上的润湿性,使氧化物颗粒嵌入孔壁中,阻碍了孔壁上金属排液现象的产生,有效的起到稳定泡孔的作用.     

国内外大型低温冷藏库氨制冷系统和制冷设备节能及安全技术的发展趋势

近年来国内外冷冻冷藏行业针对不同的冷库形式和贮藏用户特点,在低温冷藏库氨制冷系统和制冷机器、设备采用一些节能及安全技术。本文根据我国的国情和国外先进国家氨制冷系统的发展趋势做出一些研究和对比。     

Time-based replacement policies for a fault tolerant system subject to degradation and two types of shocks

A single component nonrepairable system suffering from both an internal stochastic degradation process and external random shocks is investigated in this paper. More specifically, the Wiener process with a positive drift coefficient is introduced to describe the gradual deterioration and the arrival number of external shocks is counted with a nonhomogeneous Poisson process (NHPP). Meanwhile, fault tolerant design is incorporated into the stochastically deterioration system so as to protect it from shock failures to some extent and is consummately addressed via a generalized m − δ shock model. From the actual engineering point of view, external shocks are typically classified into two distinct categories in this current research, that is, a minor shock (Type I shock) increasing the damage load on current degradation level and a traumatic shock (Type II shock) resulting in system catastrophic failure immediately. The closed-form expression of system survival function is derived analytically and is viewed as the generalization of existing reliability function for systems subject to dependent and competing failure processes. Based on which, two time-based maintenance (TBM) policies including an age replacement model and a block replacement model are scheduled, where the expected long-run cost rate (ELRCR) in each model is, respectively, optimized to seek the optimal replacement interval. In the illustrative example part, a subsea blowout preventer (BOP) control system is arranged to validate the theoretical results numerically. To compare which policy is more profitable under different conditions, the relative gain on optimal maintenance cost rate of the two TBM policies is presented.     

GARCH族模型在上海股市分阶段对比分析中的应用

应用GARCH模型族对上海股市1997年前后两个阶段的综合指数收益率进行建模分析.通过对股票收益率的基本统计量以及参数估计结果进行对比分析,从理论上定量地证明了投资者正在从以前的盲目投资逐渐地转变为理性投资,上海股市已经由市场初创过渡调整期进入了规范发展期,越来越遵循市场规范,日趋成为一个较成熟的市场.     

Effect of inorganic salts on the inhibition of hydrolyzing halo‐ester in a two‐phase solution

Abstract

Effect of the inorganic salts on the conversion of halo‐ester (ethyl‐2‐bromoisobutyrate, EtOBuBr) hydrolyzing in an alkaline aqueous solution/organic solvent two‐phase medium was investigated. The rate of hydrolyzing EtOBuBr and the conversion are obviously affected by the inorganic salts. The experimental data verify the proposed mechanism of hydrolysis. The reaction steps which hydrolyze these bromo‐alkyl bonds (Br‐C bond) and ester functional groups (–COOR) are developed and discussed. A kinetic model of the main reaction steps was established in which the rate expressions were derived. The intrinsic rate constants of the reactions were determined from the experimental data of EtOBuBr hydrolysis via parameter estimation. The results indicated that the conversion of hydrolyzing EtOBuBr is highly dependent on the concentration of alkaline compound in the aqueous solution. It is also found that sodium carbonate, sodium chloride, sodium nitrate and sodium sulfate inhibit the reaction, while calcium carbonate enhances it. The corresponding rate constants of hydrolyzing EtOBuBr in a variety of inorganic salt concentrations were searched.