Search

This paper presents experimental results on occurrence of large-scale maldistribution of parameters of liquid and vapor flows in a regular-packing distillation column. Experiments on separation of mixtures of R114/R21 freons were conducted in a Mellapak 350.Y packing of 0.9 m in diameter. Temperature distributions across column cross sections at different heights were obtained. The experimental studies revealed appearance of large-scale maldistribution of local parameters (temperature and density) across the cross section and height of distillation column when the concentration differential across the column height achieves certain values under conditions of negative stratification of vapor density. An estimative analysis of occurrence of large-scale unevenness under conditions of negative stratification of vapor flow density was done. The experimental data will serve as basis for calculating the efficiency of separation of mixtures in structured packings of column apparatuses to make allowance for the effects of the scale factor associated with large-scale maldistribution of local flow parameters.

The paper presents results of an experimental study of separation efficiency and distribution of flow parameters over the cross section of the distillation columns. The experiments were carried out on the large-scale research setup “Large Freon Column” with diameter of packing of 0.6 m and 0.9 m. The mixture of refrigerants R114 and R21 was used as the working liquid at a pressure of 3 bar in the column. Experimental data were obtained at uniform and nonuniform irrigation of the Mellapak 350.Y and Sulzer 500X structured packings by a controlled liquid distributor. The liquid distributor with independently controlled valves for each drip point was used for controlled packing irrigation. The newmethod for dynamically controlled irrigation of the packing by an operated liquid distributor is suggested. This method is aimed at the destruction of large-scale maldistribution areas (flows) inside the column and the achievement of higher separation efficiency through periodic irrigation of the entire packing or its individual areas under the liquid distributor. The use of dynamically controlled irrigation of the packing allows an increase in efficiency of mixture separation of up to 20%.

The paper presents numerical modelling of the liquid film spreading dynamics of the R21 (mol. fraction: 0.9) and R114 refrigerants mixture. We considered an outer flow along a round vertical cylinder at Reynolds number of 104 and various contact angles. The simulation was performed in OpenFOAM software on the basis of the volume of fluid (VOF) method. We have shown that the wetting front deforms at wetting angles of 30 and 50 degrees, and regular jets form. At the same time, it was demonstrated that at the wetting angle of 10 degrees the spreading front has practically a flat shape, but one may see some regular thickenings of the liquid film along the contact line of the front.

The paper presents the results of experiments on measuring heat transfer in laminar-wave films of R114/R21 refrigerant mixture flowing down a vertical plate (70 × 80 mm). The experiments were carried out on the saturation line at a pressure of 2 bar. To enhance heat transfer, a porous copper coating with a flat layer thickness of 400 μm and a porosity of 45% was applied to the heat-transfer surface by 3D printing. The effectiveness of the application of the technique used for the heat transfer enhancement is demonstrated: an increase in the boiling heat transfer coefficient is obtained up to three times in comparison with the reference smooth surface, as well as two-fold increase in heat transfer coefficient in the evaporation regime. Based on the obtained experimental results and analysis of the research data of other authors, the geometric structure of promising multiscale porous enhancing coating is proposed for further research.

The paper presents investigation results on heat transfer in falling films of refrigerant R21 on an array of horizontal tubes with a coating deposited by the method of microarc oxidation (MAO). Different MAO-coatings were applied on the surface of tubes of aluminum alloys AD31 and D16T with a diameter of 10 mm in silicate-alkaline, acidic, and phosphate electrolytes. Two coated test tubes were copper-plated additionally in a copper sulfate solution. The enhancement of heat transfer on the tubes with a porous coating depends in a complex manner on the parameters of MAO-coating surfaces defined by their treatment regimes. The highest 3-fold heat transfer enhancement in comparison with plain tube in the nucleate boiling regime was achieved on the surface of a tube made of alloy D16T with the MAO coating of 30-μm thickness, obtained in a silicate-alkaline electrolyte. Additional deposition of copper particles on the MAO-coatings leads to an enhancement of heat transfer by (20–30) % compared to plain tube. In the studied range of Reynolds number 600–1500, the effect of irrigation density on the heat transfer coefficients is not observed.

The paper presents investigation results about the influence of various methods of surface treatment on heat transfer enhancement in falling films of R21 Freon on an array of horizontal tubes. The experiments were carried out on the aluminum alloy tubes with a ceramic coating obtained by micro-arc oxidation and on copper tubes with a structured surface, treated by deformational cutting. The experiments were carried out in a regime of turbulent film flow at Reynolds numbers from 400 to 1500. The results of measuring the heat transfer coefficients on the surface of samples with a developed surface and on the standard smooth tube are compared. The highest values of heat transfer coefficients in falling films during nucleate boiling were obtained on a structured surface with semi-closed cavities. Heat transfer enhancement on the surface of a tube made of alloy D16T with the MAO coating of 30 μm thick, obtained in a silicate-alkaline electrolyte, is comparable to heat transfer enhancement on the surface of copper tubes with a microstructure applied by the deformational cutting method.

An automated system of acquisition of raw experimental data and a control system for operation modes of an experimental large-scale separation column are described. The influence of a new method of irrigation of a structured packing on the separation column efficiency is studied. Based on the data obtained by the developed automated system, a 20–30% increase in the efficiency of mixture separation on a structured packing is expected.

Structured packings are widely used in distillation columns to separate various types of mixtures. These packings have an ordered structure, which ensures more uniform conditions for interaction of counter-current flows of liquid and vapor than in the random packings and have a small hydraulic resistance. Nevertheless, in columns with a diameter of more than 0.5 m, formation of large-scale non-uniformity in distribution of liquid and vapor flow parameters over the packing cross-section is observed. In this work, experimental data on formation of large-scale non-uniformity in the temperature field over the cross-section of the Sulzer 500X packing, as well as on the efficiency of mixture separation and the pressure drop across the packing were obtained. The experiments were carried out with separation of R114/R21 freon mixture on a 10-layer structured packing Sulzer 500X with a diameter of 0.6 m and a height of 2.2 m. Experimental data were compared with the results obtained earlier for a structured packing Mellapack 350.Y with a diameter of 0.9 m and a height of 2.1 m. The presented experimental data will be used to construct and verify a new model of mass transfer and efficiency of mixture separation in the large-scale distillation packed columns.

Experimental results on measuring heat transfer in falling films of R21 refrigerant on a bundle of horizontal tubes with structured surfaces are presented. The experiments were carried out in the range of Reynolds number of the saturated liquid film from 500 to 1500 at a pressure of 3 bar in the evaporator. To intensify heat transfer, copper tubes with an external surface treated by the method of deformational cutting (MDC) were used. Three types of structures were used: structure No. 1 with half-closed microcavities, structure No. 2 with a rhomboid shape, and structure No. 3 created on the basis of structure No. 2 with additional transverse ribbing. It was shown that the studied types of structures can significantly increase the heat transfer coefficient as compared to a smooth surface. The structure with half-closed microcavities was the most effective for heat transfer enhancement.

The effect of surface microstructures created by the precision method of processing plastic materials (method of deformational cutting) on heat transfer was studied on falling films of refrigerant mixture R114/R21. The binary mixture film flowed along the outer surface of the vertical heated cylinders in the laminar-wave regime within the range of the film Reynolds numbers from 300 to 1400. The heat flux density varied from zero to critical values. It has been shown that surfaces with semi-closed pores have an advantage in heat transfer enhancement at boiling (up to four times compared to a smooth surface), while micro-pin structures contribute to an increase at evaporation regime (up to two times compared to a smooth surface). Both types of microstructures demonstrate an increase in the values of critical heat flux in comparison with a reference smooth surface (more than two times) and significantly exceed the values obtained for some of modern commercially available surfaces of “GEWA” and “Turbo” series. The parameters of surface microstructures, most effective for heat transfer enhancement in various regimes, have been identified. The experimental results were compared with the available correlations for calculating the heat transfer coefficient and the critical heat flux.

This paper describes application of SiC ceramic foam to distillation. The investigated foam SiC ceramic packing and smooth SiC ceramic packing parameters in geometrical characteristics are similar to the Mellapale structured packing parameters. The hydrodynamic performance parameters including pressure drop for dry and wet packing, flood velocity, and liquid hold-up, which are determined in a plexiglas tower of a 100-mm internal diameter. The mass transfer efficiency is measured in another glass tower of a 100-mm internal diameter by total reflux experiments, using a mixture of n-heptane and cyclohexane at atmospheric pressure. The experimental results show that the foam SiC ceramic structured packing has a higher dry and wet pressure drop, higher liquid hold-up, higher mass transfer efficiency, and unchanged flood velocity, comparing with a smooth SiC ceramic structured packing with the same shape. Comparison of the experimental data on the separation efficiency and relative pressure drop was performed for foam/smooth SiC ceramic and metal Mellapak structured packings.

The results of an experimental study of heat transfer in the liquid films flowing down a vertical cylinder with different types of surface structuring are presented. The methods of heat transfer enhancement and critical heat flux increase using horizontal ribbing, rhomb-shaped notches and mesh surface coating at the wave-laminar film flow were investigated. The mixture of refrigerants R114 and R21 was used as a working liquid; initial concentration of volatile component R114 in the mixture was varied from 0% to 19%. It is found out that a change in the character of the wave film flow on the surface with horizontal ribbing at film Reynolds numbers Re > 400 leads to heat transfer intensification at evaporation compared with the smooth and rhomb-shaped surfaces. At evaporation and development of nucleate boiling, the heat transfer coefficient on the surface with mesh coating is higher than for the smooth and textured surfaces. At nucleate boiling there is no effect of surface texture on heat transfer. The influence of the initial composition of a binary mixture of refrigerants with close saturation temperatures on the heat transfer coefficient at evaporation and boiling is insignificant. The development of crisis phenomena over the studied structured surfaces is determined by the regularities of dry spot formation, specific to evaporation of the wave liquid film.

Results on experimental investigation of heat transfer in the liquid films dichlorofluoromethane R21 and dichlorotetrafluoroethane R114 Freon mixture over the vertical tubes are presented. We have studied the film flow over the outer surface of tubes with 50-mm diameter and different configurations: smooth surface, horizontal ribs, and diamond-shape knurling. Heat transfer coefficients were measured under the conditions of evaporation and nucleate boiling together with wave characteristics of the falling film, binary mixture composition, and critical heat fluxes corresponding to dry spots formation. The film Reynolds number at the inlet to the test section was varied from 15 to 250. At evaporation regime the heat transfer coefficient for a smooth surface decreases classically with an increase of Reynolds number. Dependence of heat transfer coefficient on irrigation density for the surface with diamond-shape knurling is similar to dependence for the smooth surface with insignificant heat transfer intensifi...

The paper presents experimental results on the separation efficiency and distribution of flow parameters over the cross section for uniform and nonuniform modes of irrigation of aMellapak 350.Y structured packing in a distillation column 0.9 m in diameter using a mixture of Freon R114 and R21. Empirical data are obtained for the dynamic characteristics of forming a large-scale temperaturemaldistribution over the packing cross section as the column operation becomes steady. The dynamics of changes in the structure of large-scale temperatures maldistribution over the packing cross section is studied under various disturbing effects on the parameters of jet irrigation. The gained results form a methodological and comparative base for further investigations aimed at searching for new methods of mass transfer intensification in mixture separation, which are based on dynamically controlled irrigation of the regular packing by a liquid.

The paper presents the experimental results on heat transfer in films falling down the vertical cylinder with mesh coating in a wide range of Reynolds’ number (30–270). The mixture of freons R21 and R114 as well as the pure R21 were used as working liquids. The features of heat transfer in falling liquid films on the surface with wire mesh coating compared with the smooth surface have been revealed. It is shown that the heat transfer coefficient at evaporation on the surface with mesh coating is somewhat higher than on the smooth surface; and the nucleate boiling develops earlier on the surface with such a coating. The influence of the initial mixture composition on the coefficient of heat transfer is negligible at evaporation and boiling of binary mixture of freons with close saturation temperatures

The paper presents the results of experimental studies on liquid spreading over the Sulzer 500X packing at single drip point irrigation. The experiments were carried out using a 10% mixture of R114/R21 freons on one packing layer with a diameter of 0.6 m. The flow rate of liquid flowing from the lower edge of the packing was measured automatically by a flow meter moving along the packing sheets with a given step. The flow meter used volumetric measurement method. The receiving collector of flow meter is 50x50 mm in size, operating range of flow measurement is 0.05–50 ml/s. Distributions of liquid over the packing were measured at single-jet irrigation in the range of jet flow rates 2.5 < q irrig < 60 ml/s. Spreading zone in the case of irrigation by a single jet is limited by the corrugation channels coming from the irrigation point. The pattern of spreading at low-flow jet irrigation has the shape of a dome with a low flow rate at the outlet of corrugation channels, which limit the spreading zone. With an increase in the flow rate, the share of liquid in these channels increases and dominates over other parts of the spreading zone.

It is well known that a good quality of liquid distribution over the surface of structured packings is crucial for high performance of large diameter columns. The angle of rotation of the packing layers and their number are among the main parameters characterizing the distribution of liquid in a structured packing over the column cross-section and height. This paper presents investigation results on the influence of the rotation angle of structured packing layers on separation efficiency, pressure drop, distribution of local composition of mixture and local liquid flow rate under the packing. The experiments were carried out in distillation column with the internal diameter of 0.9 m on a structured packing with a specific area of 500 m2/m3, and the corrugation angle of packing equal to 45°. The mixture of refrigerants R114 and R21 at the pressure of 3 bar and total reflux was used as the working fluid. The column was packed with 11 packing layers with rotation angles of 20, 45, 70, and 90 degrees. According to experimental results, a decrease in the angle of packing layer rotation from 90 to 20 degrees leads to a decrease in separation efficiency, while the HETP value increases by 10–12%.

The paper considers the influence of enhanced surfaces on heat transfer during evaporation and boiling of a falling laminar-wave liquid film. A mixture of R114/R21 refrigerants was used as a test fluid. The liquid film flowed on the outer surface of vertically-oriented cylinders. To intensify the evaporation process, the authors used the mesh coatings with variable mesh sizes, whereas the surfaces with variable characteristics of microstructure obtained by deformational cutting were used to enhance boiling. The report makes a conclusion about the studied types of structured surfaces, most effective for enhancement of heat transfer in different regimes. It is shown that the mesh coatings intensify heat transfer at evaporation twice as compared to a smooth surface; the microstructured coatings with partly-closed micropores obtained by deformational cutting allow fourfold heat transfer intensification at boiling.

Results of experimental study of the effect of initial maldistribution of structured packing irrigation on efficiency of binary mixture separation are presented in this article. The studies were carried out in the experimental distillation column with the diameter of 0.9 m using the R114 and R21 freon mixture. Experiments were performed on the structured Mellapak 350.Y packing of stainless steel 316L, containing 19 layers with the total height of 4.016 m at the ratio of mole liquid and vapor flow rates L/V = 1 and 1.7, respectively, and the pressure in the upper part of the column ptop = 3 bars. Nonuniformity at the packing inlet was generated via the blocking of some holes in the liquid distributor. Here, we present some results on efficiency of mixture separation, pressure drop on the packing, distribution of local liquid flow rate under the packing over the cross-section and on the column wall within the range of vapor loading factor (0.69

The results of the study of heat transfer, crisis phenomena, and wave characteristics of laminar-wavy liquid films falling over a vertical three-dimensional texture surface have been considered. The R21/R114 freon mixture is served as a working fluid. Some peculiarities of heat transfer, hydrodynamics, and development of crisis phenomena in a binary liquid film falling over heat-releasing surfaces of different geometry have been revealed. The dependence of the heat-transfer coefficient on the flow rate for a three-dimensional texture surface in the regime of evaporation is shown to be similar to the dependence for a smooth surface with slightly intensified heat transfer in the region of inlet film Reynolds numbers of 100–500. The heat transfer coefficients of nucleate boiling on the studied types of structured surfaces are much lower than for a smooth tube. In the regime of undeveloped nucleate boiling, the critical heat flux for all surface types is deter-mined by the dependence obtained by considering the appearance of the heat transfer crisis in an evaporating wave liquid film.

Results of experimental studies of heat-and-mass transfer and hydrodynamic processes at distillation on a regular packing are presented. The mixture of freons R114–R21 at the pressure of 0.3 MPa was used as a working mixture. The mixture was separated on the Mellapak 350Y structured packing with the diameter of 0.9 m under the conditions of complete reflux ( L/V = 1) at different packing heights. A specially designed liquid distributor with a possibility to change the density and pattern of drip points was used to irrigate the packing. The experimental data on the efficiency of mixture separation (height of transfer unit HTU ) and distribution of the local flow rate density over the column cross-section were compared. It is shown that an increase in the height of the structured packing from 2.1 m to 4.0 m leads to a significant decrease in the efficiency of mixture separation in the distillation column.

Investigation results on hydrodynamics, heat transfer, and crisis phenomena in laminar-wave liquid films falling down the surfaces of different geometry are presented in this study. Freon mixture R21/R114 with initial concentration of low-boiling component of 4–16.6 % was used as the working liquid. The film Reynolds number at the inlet to the experimental section varied from 60 to 700. The heat flux density was changed within 0–5 W/cm2. The images of wave surface of the falling liquid film and formation of dry spots were visualized and recorded by the high-speed video camera. Results of investigation of the wave structure of the film surface, measurements of heat transfer coefficients under the conditions of boiling, and critical heat fluxes in the film flow over the smooth and structured surfaces are presented.

The paper presents the results of experimental investigation of heat transfer and hydrodynamics of falling films of binary mixtures of R21 and R114 freons on the surfaces with complex configuration. The vertical tubes of 50-mm diameter with the smooth and structured surfaces, made of D16T alloy, were used as the working sections. The range of film Reynolds number at the inlet to the working section was Re =10÷155. The image of wave surface of the falling liquid film was visualized and recorded by a high-speed digital video camera. At evaporation the heat transfer coefficients on the smooth and structured surfaces are determined by the liquid flow rate and weakly depend on the heat flux. At low liquid flows, the heat transfer coefficients on the structured surface decrease in comparison with the smooth surface because of liquid accumulation and enlargement of efficient thickness in microtexture channels. At high liquid flows, a change in the structure of the wave film surface leads to an increase in heat transfer coefficients in comparison with the smooth surface.

The distribution of the composition of a mixture of Freons R-114 and R-21 over the cross section of a distillation column filled with structured packing is experimentally studied. Results on the efficiency of Freon mixture separation, the pressure drop in the packing, and the distribution of the local concentration of the low-boiling component throughout the cross section and height of the structured packing are presented. The vapor phase load factor was varied over a wide range up to hydraulic flooding. According to the experimental results, the large-scale maldistribution of the mixture composition occurs inside the packing over the column cross section, even though the overall separation performance of the column is excellent. Maldistribution is observed throughout the total height of the column. The location of the large zones of maldistribution significantly depends on the liquid and vapor flow rates.

The paper present the results of experimental studies on dynamics of the film flow of cryogenic liquid over the complex surfaces: vertical plane and ribbed aluminum plates with horizontal wave microtexture. Experimental results were obtained at the flow of liquid nitrogen. According to high-speed video recording, in case of horizontal microstructure the wave dynamics influences considerably liquid redistribution in transverse direction. This is caused by the fact that liquid flows intensively at propagation of secondary waves along the channels of horizontal microstructure. According to results of experiments on the ribbed structured perforated aluminum surfaces with the horizontal microstructure with the use of highly wetting low-viscous liquids, the film flow character depends significantly on the irrigation rate. The direction and parameters of microstructure, position and diameter of holes effect significantly the zones of liquid spreading and its distribution over the surface of the ribbed structured plates, especially, within the range of low liquid flow rates.

The results of an experimental study of the effect of the initial maldistribution over a structured packing on the separation efficiency of a binary freon mixture are considered. The study was performed in a distillation column 0.9 m in diameter on a mixture of R114 and R21 freons. The results on the efficiency of freon mixture separation, the pressure drop on the packing, and the distribution of the local liquid flow rate under the packing are presented. The experimental results showed that the rotation angle of structured packed layers have a significant effect on the efficiency of mixture separation in the case of maldistribution.

In this paper, the results of an experimental investigation of the distribution of local coefficients of mass transfer on a pipe wall for a flow of a two-phase gas-liquid mixture with a turn of 90° are presented. The mass transfer coefficients were measured by using an electrodiffusion method. It has been shown that the distribution of local mass transfer coefficients on the inner surface of a curvilinear channel is nonuniform both in length and along the perimeter and depends on the content of gas in the two-phase flow.

A large-scale experimental setup is designed to study the hydrodynamic parameters and the mass-transfer efficiency in a countercurrent flow of mixtures of Freon R21 and Freon R114 on structured packings in a column 0.9 m in diameter. The study deals with the local and integral parameters of separation of the mixture, the degrees of nonuniformity of the flow rates and concentration distributions of the liquid and vapor phases over a cross section and on the column wall, and the pressure difference while varying the number of packing layers and their rotation angle. The mass-transfer processes while independently varying the liquid and vapor flow rates over wide ranges are also investigated. Experimental data are presented to illustrate the effect of the operating parameters on the height of an equivalent theoretical plate, the relative pressure difference, and the distributions of the local parameters of the flows.

Experimental data on heat transfer with intense evaporation in the falling films of liquid nitrogen were analysed. According to data generalization, heat transfer at evaporation becomes more intense under the precrisis modes at high heat fluxes for two studied boundary conditions on the heat-releasing surface: Tw ≈ const and qw ≈ const. The relative contributions of conductive and convective components of heat transfer for different heat fluxes were estimated due to statistical treatment of the wave characteristics carried out by the capacitance probes for measurement of the local liquid film thickness. It was found out that heat transfer intensification is mainly caused by a drastic decrease in thermal resistance of the local zones with intensely evaporating residual layer between large waves. At that, the convective component of heat transfer related to wave perturbations on a free surface of a liquid film decreases significantly with a rise of heat fluxes. New data on pulsations of the local temperature of the heat-releasing surface were obtained at different points along the flow with the modes of “dry spot” formation.

The use of modern structured packing in the distillation columns allows much more even distribution of the liquid film over the packing surface, but it does not completely solve the problem of uniform distribution of flow parameters over the entire height of the packing. Negative stratification of vapor along the packing height caused by different densities of vapor mixture components and higher temperature in the lower part of the column leads to formation of large-scale maldistributions of temperature and mixture composition over the column cross-section even under the conditions of uniform irrigation of packing with liquid. In these experiments, the idea of compensatory action of liquid distributor on the large-scale maldistribution of mixture composition over the column cross-section was implemented. The experiments were carried out in the distillation column with the diameter of 0.9 m on 10 layers of the Mellapak 350Y packing with the total height of 2.1 m. The mixture of R-21 and R-114 was used as the working mixture. To irrigate the packing, the liquid distributorr with 126 independently controlled solenoid valves overlapping the holes with the diameter of 5 mm, specially designed by the authors, was used. Response of the column to the action of liquid distributor was observed in real time according to the indications of 3 groups of thermometers mounted in 3 different cross-sections of the column. The experiments showed that the minimal correction of the drip point pattern in the controlled liquid distributor can significantly affect the pattern of flow parameter distribution over the cross-section and height of the mass transfer surface and increase separation efficiency of the column within 20%.

Negative vapor stratification along the height of distillation column caused by different density of vapor mixture components and higher temperature at the column bottom, leads to formation of large-scale maldistribution of temperature and mixture composition over the column cross-section even at uniform irrigation of the structured packing. Experimental results concerning the dynamic effect of packing irrigation on separation efficiency of the two-component mixture of R-21 and R-114 are presented in this paper. The structured packing Zulser 350Y was installed in the distillation column with the diameter of 0.9 m. Experiments were carried out on the 10- and 19-layer packing with an overall height of 2.1 and 4 m, respectively. The liquid distributor with independently controlled 126 valves for each irrigation point, developed by the authors, was used for packing irrigation. The experiments showed that the periodic impact of the irrigation system on the large-scale non-uniformity of mixture composition, formed in the packing, could significantly affect the distribution of flow parameters over the cross-section and height of the mass transfer unit. Essentially nonuniform periodic irrigation of the packing can improve the separation efficiency of the column within 20%, if the switching periods are comparable with the times of formation of large-scale non-uniformity.

Successive and versatile investigation of heat and mass transfer in two-phase flows is caused by their wide application in power engineering, cryogenics, chemical engineering, and aerospace industry, etc. Development of new technologies, upgrading of the methods for combined transport of oil and gas, and improvement of operation efficiency and reliability of conventional and new apparatuses for heat and electricity production require new quantitative information about the processes of heat and mass transfer in these systems. At the same time necessity for the theory or universal prediction methods for heat and mass transfer in the two-phase systems is obvious. In some cases the methods based on analogy between heat and mass transfer and momentum transfer are used to describe the mechanism of heat and mass transfer. These studies were initiated by Kutateladze, Kruzhilin, Labuntsov, Styrikovich, Hewitt, Butterworth, Dukler, et al. However, there are no direct experimental evidences in literature that analogy between heat and mass transfer and momentum transfer in two-phase flows exists. The main problem in the development of this approach is the complexity of direct measurement of the wall shear stress for most flows in two-phase system. The success of the analogy for heat and momentum transfer was achieved in the prediction of heat transfer in annular gas-liquid flow, when the wall shear stress is close to the shear stress at the interface between gas core and liquid film. Following investigation of possible application of analogy between heat and mass transfer and hydraulic resistance for calculations in two-phase flows is interesting from the points of science and practice. The current study deals with experimental investigation of mass transfer and wall shear stress, and their interaction at the cocurrent gas-liquid flow in a vertical tube, in channel with flow turn, and in channel with abrupt expansion. Simultaneous measurements of mass transfer and friction factor on a wall of the channels under the same flow conditions allowed us to determine that connection between mass transfer and friction factor on a wall in the two-phase flow is similar to interconnection of these characteristics in a single-phase turbulent flow, and it can be expressed via the same correlations as for the single-phase flow. At that, to predict the mass transfer coefficients in the two-phase flow, it is necessary to know the real value of the wall shear stress.

This paper presents the experimental results on heat transfer and hydrodynamics of the falling films of binary Freon mixtures on the tubes with smooth and textured surfaces. The range of Re number alteration at the working section inlet was Re = 10–155. The wave surface of the falling liquid film and the process of dry spot formation were recorded by the high‐speed digital video camera. Results of investigation of the wave surface structure, measurements of heat transfer coefficients and dynamics of dry spot formation on the heated surface with corresponding critical heat fluxes are shown in this paper.

Results of an experimental investigation of heat and mass transfer and wall shear stress at gas-liquid flow in a vertical tube are presented. Local wall shear stress and mass transfer coefficients were measured by an electrochemical method. Experiments were performed in the range of Reynolds number variation with respect to liquid Rci, = 8.5 × 103-5.4 × 104, gas Reg = 3 × 103-1.4 × 105, pressure 0.1-1 MPa. The relationship between heat and mass transfer and wall shear at gas-liquid flows is shown to exist. The results of measuring heat and mass transfer coefficients are generalized by formulas applied to calculate heat and mass transfer in single-phase turbulent flow.