Some features of convective heat and mass transfer in multicomponent gaseous mixtures

Unstable diffusive mass transfer in a three-component gaseous mixture under nonisothermal conditions is investigated experimentally. Using linear analysis of the mixture for stability, the critical Rayleigh numbers are determined. Al' Farabi Kazakh National State University, Almaty. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 6, pp. 977–981, November–December, 1996.     

Comparison of methods of describing mass transfer in multicomponent mixtures

The accuracy of three basic approximate methods of describing mass transfer in multicomponent mixtures is estimated by using a mathematical model of intraphase mass transfer.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 4, pp. 615–619, April, 1977.     

Separation of mixtures and heat and mass transfer in connected channels

The stationary and oscillatory regimes of thermal convection in a binary liquid mixture flowing in narrow connected channels under the action of positive and negative thermodiffusion have been studied. It is established that specific oscillatory flows develop in the case of positive thermodiffusion at a small supercriticality. A mechanism explaining the observed phenomena is proposed and confirmed by the results of numerical calculations. It is shown that connected channels can be used in technological processes for the separation of components in binary liquid mixtures.     

An approximate mathematical model of heat and mass transfer in two-phase flow

We propose an approximate method for studying transport processes in one-dimensional two-phase flow which permits the determination of the system output as a function of input and the system parameters. The error of the method is estimated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 34, No. 4, pp. 673–683, April, 1978.     

Radiation heat transfer in two-phase media

The state of the art of approximate and numerical methods of the theory of radiation heat transfer is analyzed. The principles for producing engineering methods of computing the radiation heat-transfer characteristics in power plants are examined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 807–814, November, 1987.     

Analytical solution for the simultaneous heat and mass transfer problem in air washers

An analytical solution approach for the simultaneous heat and mass transfer problem in air washers operating as evaporative coolers is presented. A one-dimensional model using the coupled mass and energy balance equations in the air washer is presented. Then, starting from a linear approach for the experimental curve of the air saturation, an analytical solution for the model was derived. The solution showed an excellent agreement with the available results found in the literature. The influence of several important parameters for the cooling process such as temperature and ambient air humidity, air flow rate and feeding water temperature, in the air cooling rate was investigated. The efficacy of the process can be greatly increased by reducing the cooling water temperature and the applied air flow rate. The analytical solution can be easily included into the models used for simulating desiccant air-conditioning systems operating in conjunction with air washers.     

Optical investigation of heat and mass transfer in vapor condensation from vapor-gas mixtures

Experimental data on the temperature and concentration fields are obtained by an interferometric procedure in vapor condensation from a vapor-gas mixture and from a vapor-vapor mixture of six working media under natural convection conditions.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 6, pp. 892–897, December, 1987.     

Control of sources in one problem of heat and mass transfer in gas mixtures

A necessary condition of controllability for processes of heat and mass transfer in binary gas mixtures and liquid solutions is presented. The necessary and sufficient conditions for invertibility of the system under consideration are obtained.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 6, pp. 936–940, December, 1985.     

Limiting heat transfer in horizontal two-phase thermosiphon

Experimental results on the heat-transfer crisis in a horizontal thermosiphon with steam heating are outlined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 1, pp. 63–67, January, 1990.     

Convective heat transfer coefficients for near-horizontal two-phase flow of nitrogen and hydrogen at low mass and heat flux

Correlations for convective heat transfer coefficients are reported for two-phase flow of nitrogen and hydrogen under low mass and heat flux conditions. The range of flowrates, heat flux and tube diameter are representative of thermodynamic vent systems (TVSs) planned for propellant tank pressure control in spacecraft operating over long durations in microgravity environments. Experiments were conducted in normal gravity with a 1.5° upflow configuration. The Nusselt number exhibits peak values near transition from laminar to turbulent flow based on the vapor Reynolds number. This transition closely coincides with a flow pattern transition from plug to slug flow. The Nusselt number was correlated using components of the Martinelli parameter and a liquid-only Froude number. Separate correlating equations were fitted to the laminar liquid/laminar vapor and laminar liquid/turbulent vapor flow data. The correlations give root-mean-squared (rms) prediction errors within 15%.     

Diffusional mass transfer in liquid mixtures

The general form of the equations for determining the flow relations in liquid mixtures is obtained. A closed calculation algorithm and an experimental method of holographic interferometry are developed for the identification of the binary-diffusion coefficients. A ternary mixture is investigated by the method of molecular dynamics.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 6, pp. 1016–1023, December, 1990.     

Model of heat and mass transfer in the drying process with the removal of multicomponent liquid systems

A mathematical model of heat and mass transfer is proposed on the basis of the assumption of thermodynamic equilibrium between the liquid and the vapor removed in the course of drying.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 2, pp. 229–234, August, 1984.     

Coupled heat and mass transfer during nonisothermal absorption by falling droplet with internal circulation

We considered mass and heat transfer during nonisothermal absorption of a gas by a falling droplet with internal circulation. Gas phase is assumed to be free of inert admixtures and mass transfer is liquid phase controlled. Mass flux is directed from a gaseous phase to a droplet, and the interfacial shear stress causes a fluid flow inside the droplet. Droplet deformation under the influence of interface shear stress is neglected. Absorbate accumulation and temperature increase in the bulk of liquid phase are taken into account. The problem is solved in the approximations of a thin concentration and temperature boundary layers in the liquid phase. The thermodynamic parameters of the system are assumed constant. The system of transient partial parabolic differential equations of convective diffusion and energy balance with time-dependent boundary conditions is solved by combining the similarity transformation method with Duhamel's theorem, and the solution is obtained in a form of Volterra integral equation of the second kind which is solved numerically. Theoretical results are compared with available experimental data for water vapor absorption by falling droplets of aqueous solution of LiBr.     

Convective heat transfer in a dynamic two-phase bed

An electrochemical method is used to investigate the average mass transfer coefficients and it is shown that the experimental data are correlated very satisfactorily by a relationship [4, 5] obtained on the assumption of no evaporation at the surface of the liquid film.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 6, pp. 1060–1065, June, 1971.     

A detailed study on simultaneous heat and mass transfer in an in-tube vertical falling film absorber

In the present study, a numerical model of a vertical in-tube falling film absorption heat exchanger utilizing NH₃−H₂O pair as working fluid is developed. At first, the results of the simulations are validated with experimental data obtained from the absorber of an Absorption Heat Transformer (AHT). Then, in order to comprehend the effect of measurements errors on the results of the model, the sensitivity of the model with respect to the measured inlet conditions is investigated. Furthermore, simultaneous heat and mass transfer along the interface throughout the pipes length is studied. Results indicate that the main resistances for heat and mass transfer are the ones between gas and interface. It has been also found that the majority of the gas gets absorbed by the film in the top segments of the pipes since the driving forces along the interface are higher in these segments.     

Mathematical analysis for the efficiency of a semi-spherical fin with simultaneous heat and mass transfer

In this paper an analytical solution for the efficiency of a semi-spherical fin when subjected to simultaneous heat and mass transfer mechanisms is studied. For the mathematical analysis of a wet fin equation, a relationship between humidity ratio and temperature of the saturation air is needed. The driving forces for the heat and mass transfer are the temperature and humidity ratio differences, respectively. Analytical solutions are obtained for the temperature distribution over the fin surface when the fin is fully wet. It is observed that in humid conditions the fin has high efficiency to be used in industry. The variation effects of these parameters have been considered. Finally linear relation has been proposed for humidity and temperature on the fin surface.     

A note on two-phase film mass transfer without mass forces

Some aspects of two-phase film mass transfer in the absence of mass forces are examined. The results are novel in that the parametric equations contain expressions which take into account the physical properties of the contact phases.     

Contact heat transfer and external mass transfer in contact drying

The heat transfer, compounded by a phase transformation, between the heater surface and the adjoining dried material is considered here as well as the mass transfer between the free surface of this material and surrounding medium (air or cloth) during the first stage and the second stage of the drying process.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 3, pp. 482–490, September, 1970.     

A review of hydrocarbon two-phase heat transfer in compact heat exchangers and enhanced geometries

Hydrocarbons are considered as alternative fluids for refrigeration, air-conditioning and heat pump applications. Pure butane, propane or their mixtures can be adopted, but due to their flammable properties, the systems have to be designed in such a way that the refrigerant charge is minimized. Therefore, compact heat exchangers and enhanced geometries are adopted in such systems. In this paper, the current state of the art for two-phase heat transfer calculations for pure hydrocarbons and their mixtures is reviewed and analysed. Recommendations are proposed for estimating evaporation and condensation heat transfer in various geometries including enhanced tubes as well as compact heat exchangers.