制冷系统中应用R22/R142b非共沸混合制冷剂时冷凝温度和蒸发温度的确定

R22／R142b非共沸混合制冷剂在冷凝器和蒸发器中其冷凝温度和蒸发温度是变化的。混合制冷剂浓度、冷凝压力和蒸发压力的不同，都会导致其最高冷凝温度、最低冷凝温度、最高蒸发温度和最低蒸发温度发生变化。因此，压力、温度和浓度等参数的选取是R22／R142b应用中需要解决的问题。本文利用溶液热力学的有关定律，采用严密的数学推导及定性分析导出它们之间的相关关系式，并绘制相关曲线和图表，为R22／R142b的应用提供了方便、可靠的依据和方法。     

负载型Nb2O5对异丁烯/异丁醛缩合生成2,5-二甲基-2,4-己二烯的催化性能

采用Hammett指示剂、吡啶吸附红外光谱（Py—IR）和微反测试等方法，考察了负载型Nb2O5催化剂表面酸性特征和对异丁烯（IB）异丁醛（IBA）缩合生成2，5-二甲基-2，4-己二烯（DMHD）反应（称为Prins缩合）的催化活性。结果表明，催化活性与催化剂表面酸性特征有关。在Nb2O5／γ-Al2O3表面，只有当Nb2O5负载量超过一定量后才形成可检测的B酸位，并对IB／IBA缩合生成DMHD的反应才有明显的催化活性。随着Nb2O5负载量增加．Nb2O5 γ-Al2O3。表面B酸位数增加且强度增强，催化剂的活性和产物的选择性增加；当Nb2O5负载量超过分散布容量后，因表面形成较强的B酸位而导致DMHD选择性降低。将TiO2引入Nb2O5／γ-Al2O3，使催化剂表面B酸位数增加．从而提高了催化剂的活性；而将ZrO2引入Nb2O5/γ-Al2O3，则导致催化剂表面B酸位数大幅度减少，从而显著降低了催化剂的活性。催化剂表面B酸位是IB／IBA缩合生成DMHD的反应活性中心。     

Influence of tube inclination on the flow regime boundaries of condensing steam

Flow regime data of condensing steam inside an inclined 13.4 mm ID tube are presented. The effect of upward and downward inclinations within ± 10° on the different transition lines is discussed. In all test runs, complete condensation has been achieved inside the condenser, with or without full tube at exit depending on the total mass flow rate and inclination angle. It is shown that the zones occupied by the wavy and slug regimes experience significant shifts, whereas the effect on the annular flow boundary appears to be insignificant at the present small inclination angles. The present data sets are compared with adiabatic gas-liquid flow regime maps developed analytically and experimentally for horizontal and inclined tubes. Deviations due to the condensation process are observed; however, consistent trends are identified among the two types of flow.     

INVERSE ESTIMATION OF THE WALL HEAT FLUX IN LAMINAR FILM CONDENSATION ON A FINITE-SIZE HORIZONTAL DISK WITH VARIABLE HEAT FLUX

An inverse model is used to estimate the wall heat flux in film condensation on a horizontal disk. The inverse analysis is based on film condensation thickness readings taken at several different points on the plate. Finite-difference methods are employed to discretize the problem domain, and then a linear inverse model is constructed to identify the unknown conditions. This approach rearranges the matrix forms of the governing differential equations and estimates the unknown surface conditions. Then, the linear least-squares method is adopted to find the solution.

Unlike other methods, the proposed inverse analysis method requires no prior information regarding the functional form of the unknown quantities. In addition, only one iteration is necessary for calculation, and no initial guess is required.     

镉原子在He－Cd激光器冷凝区凝结的蒙特卡罗模拟

用蒙特卡罗方法模拟了镉原子在Ｈｅ—Ｃｄ激光器的两种结构不同的冷凝区内的凝结，得到了镉原子在结构不同的冷凝区凝结的分布关系，对两种结构的分布关系进行了比较，表明改进冷凝区的结构，可以提高冷凝区对镉原子的凝结率。     

苯胺气相缩合生成二苯胺γ-Al_2O_3注Mo注N催化剂的研究

应用三束技术即高能注射方法对γ -Al2 O3注射第二组分改性 ,通过对γ -Al2 O3注Mo或注Mo注N制得Mo/γ -Al2 O3和Mo -N/γ -Al2 O3催化剂 ,研究催化剂在苯胺气相缩合生产二苯胺过程中的催化性能。与γ -Al2 O3以及浸渍法制得的Mo/γ -Al2 O3催化剂的催化性能进行对比 ,实验表明 ,注射法制得的Mo/γ -Al2 O3、Mo -N/γ -Al2 O3催化剂催化性能明显提高     

Approximate Solutions of the Nonlinear Schr?dinger Equation for Ground and Excited States of Bose-Einstein Condensates

I present simple analytical methods for computing the properties of ground and excited states of Bose-Einstein condensates, and compare their results to extensive numerical simulations. I consider the effect of vortices in the condensate for both positive and negative scattering lengths, a, and find an analytical expression for the large-N₀ limit of the vortex critical frequency for a > 0, by approximate solution of the time-independent nonlinear Schrödinger equation.     

Influence of Several Metal lons on the Gelation Activation Energy of Silicon Tetraethoxide

The effects of nine metal cations (Li⁺, Na⁺, Mg²⁺, Ca²⁺, Sr²⁺, Cu²⁺, Al³⁺, La³⁺, and Y³⁺) on silica gel formation have been investigated by studying the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) in the presence of metal nitrates. The influence of the water: TEOS mole ratio, metal ion concentration, and the reaction temperature has been investigated. The overall activation energy for gel formation has been determined from the temperature dependence of the time of gelation for each system. The activation energy for network formation is 54.5 kJ/mol. The gel formation time as well as the activation energy sharply increases in the presence of Cu²⁺, Al³⁺, La³⁺, and Y³⁺. In contrast, the presence of Li⁺, Na⁺, Mg²⁺, Ca²⁺, or Sr²⁺ lowers the gelation time but has no appreciable effect on the activation energy. This difference may be attributed to the participation or nonparticipation of the metal ions in the formation of the three-dimensional polymeric network during polycondensation. The concentration of metal ion (Mg²⁺, Ca²⁺, Y³⁺) or the water: TEOS mole ratio had no appreciable effect on the gelation activation energy. A simple test has been proposed to determine whether a metal ion would act as a network intermediate or modifier in silica and other glassy networks.     

Research on Marangoni condensation heat transfer for water and ethanol mixture vapor

A brass block was constructed as a test block to study the Marangoni condensation in this paper. The maximal temperature difference of the block surface on which pure steam condensed was 11^°C when the block was cooled by the normal temperature water. Regulations and modes of Marangoni condensation for mixture vapor with different mass fractions were studied when the speed of vapor was 0.3 m/s. As both temperature gradients and concentration gradients exist on the condensing surface, the experimental results indicate that the maximal heat transfer coefficient of mixture vapor can be 2.8 times that of pure steam when the Marangoni condensation of mixture vapor appears. The heat transfer coefficient of mixture vapor increases with the decrease of surface subcooling, and it appears a steep increase when the surface subcooling is small enough; the heat transfer flux has a maximum value as the surface subcooling rises; and the different modes of condensation are confirmed when the different ethanol concentration and different surface subcooling exist. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(8): 505–514, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20035     

Bisoxathiolane sulfides from a dioxoene fatty acid

A quantitative preparation of bisoxathiolane from 9,12-dioxo-trans-10-octadecenoic acid is discussed. The reagents used are β-mercaptoethanol and BF₃₋ etherate in acetic acid. The structure of the product was established with the help of elemental analysis, infrared, nuclear magnetic resonance and mass spectroscopy data.