Research on Marangoni Condensation Modes for Water–ethanol Mixture Vapors

In this paper the condensation experiments for water–ethanol vapors were carried out at different vapor pressures over a wide range of ethanol concentration. The condensation modes were observed and quantitatively analyzed in order to clarify the condensation phenomenon and dropwise condensation mechanisms. The cycle time of dropwise condensation, affected by vapor-to-surface temperature difference, ethanol concentration and vapor pressure, was approximate 0.2 s to 2 s. The quantity proportion of drops with the diameter less than 1 mm was more than 70% in all drops for all mixture vapors. The peak values of the maximum departing diameters increased with the ethanol vapor concentration, and were weakly affected by the vapor pressure, and the values were about 1.5 mm to 5 mm. The rivulet condensation mode was usually observed as a transition state appeared when the drop mode changed to film mode. The maximum distance between rivulets was sensitive to the ethanol vapor concentrations and little dependent on the vapor-to-surface temperature difference.     

冷凝法油气回收装置研究和应用

石油及其产品在加工和储运过程中产生的蒸发损耗是困扰石油加工储运和环保行业的重要问题,推广和采用油气回收技术十分迫切和重要.介绍了冷凝法油气回收装置的工艺原理,并对冷凝法油气回收装置的应用进行了说明.     

Modeling Iron Pentacarbonyl Vaporization Accompanied by Vapor Condensation on a Flowing Down Liquid Film

Using iron pentacarbonyl distillation as an example, we analyze the vaporization process in a closed vaporization–condensation system where vapor condenses on a flowing down liquid film. We jointly analyze the mechanisms behind vaporization, vapor transport, condensation, and flowing of the condensate on the inner surface of a vertical tube. We calculate the thickness of the flowing down liquid film, determine the vaporization coefficient for a closed system using experimentally determined temperature dependences of the vaporization rate and saturated vapor pressure, and present the vaporization rate as a function of the vaporization and condensation temperatures, the radius and height of the condensation tube, and the vaporization area of the still residue.     

Condensation of R407C in a horizontal microfin tube

This paper describes experimental results that show the effects of mass velocity and condensation temperature difference on the local heat transfer characteristics during condensation of R407C in a horizontal microfin tube. The experiments were performed at the saturation temperature of 40 °C, the refrigerant mass velocity of 50, 100, 200 and 300 kg m⁻² s⁻¹, and the condensation temperature difference of 1.5, 2.5 and 4.5 K. A superficial heat transfer coefficient for the vapor phase was obtained by subtracting the heat transfer resistance of condensate film estimated by using a previously developed theoretical model of film condensation of pure vapor from the overall heat transfer resistance. On the basis of the analogy between heat and mass transfer, an empirical equation for the superficial vapor phase heat transfer coefficient was developed. The heat transfer coefficient predicted by the combination of the previously developed theoretical model of film condensation of pure vapor and the empirical equation of the superficial vapor phase heat transfer coefficient agreed with the measured values with the r.m.s. error of 9.2%.     

Effect of precursor supply on structural and morphological characteristics of fe nanomaterials synthesized via chemical vapor condensation method

Various physical, chemical and mechanical methods, such as inert gas condensation, chemical vapor condensation, sol-gel, pulsed wire evaporation, evaporation technique, and mechanical alloying, have been used to synthesize nanoparticles. Among them, chemical vapor condensation (CVC) has the benefit of its applicability to almost all materials because a wide range of precursors are available for large-scale production with a non-agglomerated state. In this work, Fe nanoparticles and nanowires were synthesized by chemical vapor condensation method using iron pentacarbonyl (Fe(CO)5) as the precursor. The effect of processing parameters on the microstructure, size and morphology of Fe nanoparticles and nanowires were studied. In particular, we investigated close correlation of size and morphology of Fe nanoparticles and nanowires with atomic quantity of inflow precursor into the electric furnace as the quantitative analysis. The atomic quantity was calculated by Boyle's ideal gas law. The Fe nanoparticles and nanowires with various diameter and morphology have successfully been synthesized by the chemical vapor condensation method.     

真空预冷中捕水器的理论研究

真空预冷装置中,捕水器是一个十分关键的部件.其性能的优劣,直接关系到预冷的效果.介绍了捕水器的内部结构和捕水特性,建立了物理模型,对水蒸气在捕水器管路凝结问题进行了理论计算.最后对理论结果进行分析.     

Analysis of vapor condensation in porous media

Abstract

The present work analyzes the problem of vapor condensation in porous media. Specific consideration is given to a transient‐state one‐dimensional formulation, representing a porous slab exposed to the saturated vapor from one side and the cold plate on the other side. When condensation occurs, three zones will exist inside the porous medium. Near the cold plate, a liquid zone is expected. Adjacent to this zone and extending into the medium will be a two‐phase zone which is dominated by capillary and vapor phase transport. Ahead of this zone the medium will remain saturated with vapor phase. Predictions from the three‐zone model used in this study have been compared with the two‐zone model which neglects the effect of surface tension forces. The results show that the two‐zone model can only predict the condensation phenomena in low permeability media. Capillary pressure or surface tension effects become significant and cannot be neglected during the condensation of vapor in high permeability media.     

Condensation from a vapor-gas mixture on a plane surface

An approach is developed, which was previously suggested for the investigation of intensive condensation of pure vapor in application to a one-dimensional steady-state problem of condensation in the presence of a noncondensable component. Results are obtained, which make possible the estimation of the parameters of the limiting modes of condensation from a vapor-gas binary mixture.     

Theory and Calculation of the Condensation Growth of a Droplet in Pure Vapor and in a Vapor–Gas Mixture

Consideration is given to the theory of condensation as applied to the liquefaction of gases. Numerical calculations of the growth of a droplet using methane as an example revealed the decisive role of heat removal from its surface to the ambient medium in condensation from both a pure vapor and a vapor–gas mixture. It is shown that for very low supersaturations of the vapor, radiative heat removal can prevail over convective heat removal.     

Slightly nonequilibrium condensation of a saturated vapor on a liquid surface

A solution of the Barnett equations is obtained for the problem of slightly nonequilibrium vapor condensation on a liquid surface. It is shown that a Barnett sublayer with nonzero pressure gradient exists inside the nonequilibrium wall layer. The sublayer diminishes the interphase condensation resistance and induces supersaturation of the vapor.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 35, No. 5, pp. 851–857, November, 1978.     

Heat Transfer in Condensation of Vapor Moving inside Vertical Tubes

A review of works devoted to the study of heat transfer in condensation of moving vapor in cocurrent flow of vapor and film is presented. Generalization of a wide range of experimental data obtained by different authors showed that in wave regimes of film flow conditions take place under which an increase in vapor velocity does not lead to enhancement of heat transfer, as compared to heat transfer in condensation of motionless vapor. In turbulent film flow, an intense entrainment of the film from the crests of waves into the vapor core begins when W > We_cr, thus leading to considerable enhancement of heat transfer.     

Study of the Attachment Stage of a Welding Arc Discharge of Direct-Current Straight Polarity on Aluminum Surface

The results of a study on aluminum welding by direct-current straight polarity arc in a protective gas environment (argon, helium) are presented. The welding arc burns in aluminum vapor; the condensation products consequently lower the temperature of the welding column in the anode region. The condensation products of aluminum are formed by the cluster mechanism with the formation of fractal thread-like structures. The clustering mechanism is characterized by the release of nondissociated molecular blocks of aluminum into the vapor state. They form a morphologically complex composition of the alumina film on the surface of the weld pool during condensation.     

Investigation of the Growth of Particles Produced in a Laval Nozzle

This study focuses on numerical modeling of condensation of water vapor in a Laval nozzle, using the liquid drop nucleation theory. Influence of nozzle geometry, pressure, and temperature on the average drop size is reported. A computer program written in MATLAB was used used to calculate the nucleation and condensation of water vapor in the nozzle. The simulation results are validated with the available experimental data in the literature for steam condensation. The model reveals that the average drop size is reduced by increasing the divergent angle of the nozzle. The results also confirm that increasing the inlet pressure has a direct effect on the average drop size while temperature rise has an inverse effect on the drop size.     

Mechanism of vapor bubble condensation in a vapor-water mixture under impact

The mechanism and the cause of vapor bubble condensation in a vapor-water stream are analyzed. The causes (inertia of the liquid and heat transfer) actively contributing to condensation are examined. Experimental data are presented on the collapse of vapor bubbles in boiling water under impact.Translated from Inzhenerno-Flzicheskii Zhurnal, Vol. 22, No. 3, pp. 429–434, March 1972.     

R22饱和蒸汽在C-S水平管外凝结换热的实验研究

以R22为工质在套管式冷凝器中对C-S水平管在饱和蒸汽状态下冷凝传热的性能进行实验研究，得出凝结换热系数与表面张力及蒸汽流速之间的关系，并拟合出其实验关系式。     

Modeling the ultrapurification of substances by simple distillation

This paper presents a mathematical model for the ultrapurification of substances in a closed vaporization–condensation system, where the evaporation rate is determined by the combined effect of the mechanisms behind vaporization, condensation, and vapor transport from the vaporization surface to the condensation surface, and the impurity distribution in the liquid is determined by the diffusion mechanism. The degree of purification is evaluated as a function of the vaporization and condensation temperatures and the main simple distillation apparatus design parameters by numerical simulation for a particular example: removal of barium impurities from selenium.     

First integrals of equations of motion of a droplet in the presence of mass transfer to the carrier medium

Analysis is performed of first integrals in the limiting Stokes and Newtonian modes of motion of a droplet for two cases, namely, that of the droplet moving in its own vapor in the presence of phase transitions and that of the droplet moving in dusty gas without phase transformations but in view of the capture of dust particles. Expressions are found for the lengths over which the processes of condensation, complete evaporation of droplet, and deposition of particles occur. Comparison is made of the lengths and times of complete evaporation of droplet in the Stokes and Newtonian modes of droplet motion. Asymptotic formulas are obtained for these quantities, which correspond to low and high superheating of vapor, as well as formulas for the limiting diameters of droplet in the cases of condensation of vapor or capture of particles.     

Resonance phenomena during vapor condensation in a cooled tube

Experiments show evidence of the resonance phenomena during vapor condensation inside a cooled tube. The resonance sharpness depends on the region of application of an external perturbation (vapor or condensed phase).     

Weak evaporation or condensation process on a flat surface with excitation of the inner degrees of freedom of molecules taken into account

The evaporation (condensation) rates and temperature jump are calculated in a vapor in contact with its intrinsic condensed phase. The contribution of the vapor molecule inner degrees of freedom is analyzed.     

Condensation from a vapor-gas mixture

A review of the possible approaches to calculation of vapor condensation from a binary vapor-gas mixture on a surface is presented. Emphasis is paid to justification of the application of molecular-kinetic theory methods for calculation of applied problems. Quantitative estimates for the parameters of the existence in principle of the regimes of one-dimensional stationary condensation are given.