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.     

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.     

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.     

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%.     

Experimental study of condensation heat transfer of R-404A in helically coiled tubes

In this research, the heat transfer coefficients of R-404A vapor condensation inside helically coiled tubes are studied, experimentally. The effects of different coil pitches and curvature radii at different vapor qualities and mass velocities are considered. The vapor is condensed inside the helically coiled tubes by transferring heat to the cooling water flowing in annulus. Results show that the coil diameter has significant effect on condensation heat transfer coefficient. By decreasing the coil diameter or increasing the Dean number, the heat transfer coefficient is increased as the highest value is obtained at curvature radius of 4.35 cm which is 45% greater than the corresponding figure of curvature radius of 7.65 cm at mass velocity of 125 kg m⁻² s⁻¹. Also, at low vapor qualities, the coil pitch effect is more pronounced. Finally, based on the results, a new correlation is developed to evaluate the condensation heat transfer coefficient of R-404A inside helically coiled tubes.     

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.     

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.     

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.     

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.     

Experimental investigation of heat and mass transfer during condensation of water vapor from humid air on a vertical surface under natural convection conditions

Results are presented of an experimental investigation of the heat and mass transfer accompanying condensation of water vapor from vapor-air mixtures with low volumetric vapor contents (_o.v 2.1%). Empirical formulas are proposed for the heat transfer coefficient and the rate of condensation.     

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.     

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.     

Effect of ionizing radiation field on CsI aerosols formed by condensation of supersaturated vapor

The effect of the ionizing radiation field on the behavior of CsI aerosols formed by condensation of supersaturated vapor was examined. Supersaturated CsI vapor was formed by evaporation from a metal surface ohmically heated to high temperatures. A study of the size distribution function of CsI particles showed that, both in the field of ⁶⁰Co γ-radiation and in a stationary electron beam, three modes of particle size are observed with the mean sizes of 0.13, 0.57, and 0.76 μm. The amount of particles of size 0.13 μm is larger by a factor of ～10–20 than the amount of particles of sizes 0.57 and 0.76 μm. Comparison of the distribution functions of CsI aerosol particles formed by supersaturated vapor condensation in an ionizing radiation field and without it showed that the ionizing radiation affected not only the size but also the amount of particles.     

An anomalous change in the supercooling of vapor in spontaneous condensation

Spontaneous condensation of vapor at transonic velocities in the subsonic part of a flow in contrast to condensation in all the remaining regions of the flow leads not to an increase, but rather to a decrease in temperature and not to a drop, but rather to a rise in the supercooling of vapor. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 2, pp. 215–217, March–April, 1998.     

Heat transfer during condensation of vapors on a jet

Relations determining heat transfer during condensation of vapor on a jet with consideration of the thermal resistance to mass transfer of vapor toward the jet were obtained and the results of calculations are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 21, No. 1, pp. 84–91, July, 1971.     

Flow of vapor through a quasiclosed volume with a temperature gradient

Results of a theoretical and experimental study of the flow of cadmium sulfide vapor through a cylindrical chamber are cited, with condensation and reevaporation of vapor from the chamber walls taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 17, No. 3, pp. 429–436, September, 1969.     

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.     

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.     

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.     

The effect of thermal diffusion on the condensation of small additions of vapor from a gas flow

We examine the effect of thermal diffusion on the condensation of small additions of heavier vapor molecules from the gas flow streamlining a plate. We demonstrate that the thermal diffusion in this case may noticeably increase the diffusion flow of the vapor through the laminar boundary layer to the condensation surface (the surface of the plate).Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 16, No. 5, pp. 909–913, May, 1969.