Phase separation transition in a driven diffusive system with anti-ferromagnetic interaction

One-dimensional non-equilibrium systems with short-range interaction can undergo phase transitions from homogeneous states to phase separated states as interaction (?) among particles is increased. One of the model systems where such a transition has been observed is the extended Katz-Lebowitz-Spohn (KLS) model with ferromagnetically interacting particles at ?=4/5. Here, the system remains homogeneous for small interaction strength (?<4/5), and for anti-ferromagnetic interactions (?<0). We show that the phase separation transitions can also occur in anti-ferromagnetic systems if interaction among particles depends explicitly on the size of the block (n) they belong to. We study this transition in detail for a specific case ?=δ/n, where phase separation occurs for δ<−1.     

Experimental study on the condensation of supersonic steam jet submerged in quiescent subcooled water: Steam plume shape and heat transfer

The condensation of supersonic steam jet submerged in the quiescent subcooled water was investigated experimentally. The results indicated that the shape of steam plume was controlled by the steam exit pressure and water temperature. Six different shapes of steam plume were observed under the present test conditions. Their distribution as a function of the steam exit pressures and water temperatures was given. As the steam mass velocity and water temperature increase, the measured maximum expansion ratio and dimensionless penetration length of steam plume were in the ranges of 1.08–1.95 and 3.05–13.15, respectively. The average heat transfer coefficient of supersonic steam jet condensation was found to be in the range of 0.63–3.44 MW/m²K. An analytical model of steam plume was found and the correlations to predict the maximum expansion ratio, dimensionless penetration length and average heat transfer coefficient were also investigated.     

Experimental study on condensation heat transfer of steam on vertical titanium plates with different surface energies

Visual experiments were employed to investigate heat transfer characteristics of steam on vertical titanium plates with/without surface modifications for different surface energies. Stable dropwise condensation and filmwise condensation were achieved on two surface modification titanium plates, respectively. Dropwise and rivulet filmwise co-existing condensation form of steam was observed on unmodified titanium surfaces. With increase in the surface subcooling, the ratio of area (η) covered by drops decreased and departure diameter of droplets increased, resulting in a decrease in condensation heat transfer coefficient. Condensation heat transfer coefficient decreased sharply with the values of η decreasing when the fraction of the surface area covered by drops was greater than that covered by rivulets. Otherwise, the value of η had little effect on the heat transfer performance. Based on the experimental phenomena observed, the heat flux through the surface was proposed to express as the sum of the heat flux through the dropwise region and rivulet filmwise region. The heat flux through the whole surface was the weighted mean value of the two regions mentioned above. The model presented explains the gradual change of heat transfer coefficient for transition condensation with the ratio of area covered by drops. The simulation results agreed well with the present experimental data when the subcooling temperature is lower than 10 °C.     

无机化学中的脱水缩合反应

将无机化学中的脱水缩合反应进行分类:发生在无机含氧酸之间的脱水缩合反应;发生在无机含氧酸酸式盐之间的脱水缩合反应和酸化含氧酸盐溶液而发生的脱水缩合反应。介绍了缩合反应及缩合反应产物的应用。     

Heat and mass transfer characteristics of simulated high moisture flue gases

The heat transfer process occurring in a condensing heat exchanger where noncondensible gases are dominant in volume is different from the condensation heat transfer of the water vapor containing small amount of noncondensible gases. In the process the mass transfer due to the vapor condensation contributes an important part to the total heat transfer. In this paper, the Colburn-Hougen method is introduced to analyze the heat and mass transfer process when the water vapor entrained in a gas stream condenses into water on the tube wall. The major influential factors of the convective-condensation heat transfer coefficient are found as follows: the partial pressure of the vapor p _v , the temperature of the outer tube wall T _w , the mixture temperature T _g , Re and Pr. A new dimensionless number Ch, which is defined as condensation factor, has been proposed by dimensional analysis. In order to determine the relevant constants and investigate the convection-condensation heat and mass transfer characteristics of the condensing heat exchanger of a gas fired condensing boiler, a single row plain tube heat exchanger is designed, and experiments have been conducted with vapor-air mixture used to simulate flue gases. The experimental results show that the convection-condensation heat transfer coefficient is 1.52 times higher than that of the forced convection without condensation. Based on the experimental data, the normalized formula for convention-condensation heat transfer coefficient is obtained. A heat transfer area m² - Ch condensation factor - c _p specific heat at constant pressure, J/(kg·K) - G mass flux Kg/(m²·s) - h heat transfer coefficient W/(m²·K) - J J-factor - Nu Nusselt number - pa pressure - Pr Prandtl number - Q heat transfer rate - q heat flux W/m² - r latent heat, kJ/kg - Re Reynolds number - Sc Schmidt number - T temperature, C or K - heat conductivity m W/(m·K) - density, kg·m³ - g gas - h moistened hot air - i interface - v vapor - w water     

Effect of temperature gradient on Marangoni condensation heat transfer for ethanol–water mixtures

This paper experimentally studied the effect of macroscopic temperature gradient on Marangoni condensation of ethanol–water vapor mixtures under a wide range of concentrations. For each concentration, the experiment was performed at different velocities and pressures. An oblique copper block was employed to create surface temperature gradient. The results indicated that local heat flux was varied along transversal condensation surface, which was caused by surface temperature gradient. This difference in heat flux might be attributed to the variation of condensate thickness on condensation surface. In addition, a mean heat transfer coefficient was derived along transversal condensation surface. For low ethanol concentration (0.5%, 1%), the coefficient kept a high value over a relative wide range of vapor-to-surface temperature difference (<10 K) and could be augmented as much as 15% as compared with literature under similar experimental condition. Moreover, the mean heat transfer coefficient generally increased with increasing velocity or pressure for all concentrations of the ethanol–water mixtures.     

激光显示照明光路中复眼透镜的设计

设计激光投影机光学系统需要从如何减小光学系统的体积和提高激光光源的光效两个方面考虑。研究了激光显示照明系统中的复眼透镜,并对设计的复眼小透镜矩形单元进行了优化,发现在复眼透镜整体尺寸和单颗复眼小透镜焦距一定的情况下,整个复眼透镜上的阵列越多,即复眼透镜上蜂窝的数量越多,其匀光效果就越好,且此时投影机系统的体积也较小。为了提高激光光源的光效,设计中对复眼透镜在不同数值孔径照明光束下的匀光效果进行了讨论。并对优化设计后的复眼透镜进行40 000条光线追迹,实验显示其光线透过率可以达到92.5%,且几乎无杂散光。     

正则局部Lipschitz函数可微性的几何条件

Ｂａｎａｃｈ空间的范数可微性可用它的单位球面来刻画．本文把这些范数可微性的几何条件推广到正则局部Ｌｉｐｓｃｈｉｔｚ函数情形．     

On the dependence of the condensation coefficient on surface curvature

It is concluded that there is as yet no adequate theoretical solution for the size dependence of the condensation coefficient, the Okuyama-Zung approach to this problem being discounted.