Average Mass Transfer Rates Research Articles

Mass transfer between a flowing fluid and a solid wavy surface

AbstractThis paper considers the transfer of mass or heat between a fluid and a small amplitude solid wavy surface. A periodic variation of the transfer rate can occur because of wave induced variations of the normal convective flow and of the properties of the turbulence. Solutions of the mass balance equations are presented for the laminar flow at a large Schmidt number or Prandtl number and for turbulent flow at large and small wave numbers. For turbulent flows at intermediate wave numbers, the prediction is limited by inadequacies of present theories that model the wave induced variation in the turbulent diffusion of heat or mass. In order to provide guidance for this modeling, new measurements on the variation of the mass transfer rate along a solid wavy surface are presented for a Schmidt number of 729. An analogy between momentum and mass transfer is explored as a means for evaluating the turbulent diffusion terms.The amplitude of the function describing the mass transfer variation is found to decrease with decreasing wave number and the phase to increase with decreasing wave number. The phase angle and the amplitude of the variation in the mass transfer rate relative to the average mass transfer rate are insensitive to changes in Schmidt number or Prandtl number. For turbulent flows, the phase change can be large enough that the maximum in the mass transfer rate can exist somewhere in the trough of the wave. This result is of considerable significance in interpreting wavelike dissolution patterns.

Mass transfer in TV Cassiopeiae

The period variations of TV Cassiopeiae between 1901 and 1977 are discussed in the light of the period change model proposed by Biermann and Hall. During each period decrease 4.0×10−6M⊙ of mass is transferred from the secondary star to the primary. The average observable mass transfer rate is found to be 4.3×10−7M⊙ yr−1. This average rate corresponds to the thermal time-scale of the mass-losing star.

Mass transfer at the wall as a result of coherent structures in a turbulently flowing liquid

A direct numerical calculation of the instantaneous mass transfer at a solid boundary was made from a one-dimensional mass balance equation with the only input Information being the normal velocity. This velocity was generated on the computer so as to have the gross characteristics of the normal velocity obtained from turbulence experiments. The average mass-transfer rate was adequately predicted. Other characteristics of the scalar field are reported.

Comparative analysis of mass transfer at vibrating electrodes

The application of oscillatory flows to electrochemical processes was found to increase the rate of mass transfer and improve the quality of deposit. Various mechanisms to which this phenomenon is attributable are discussed and expressions for the average rate of mass transfer, resulting thereof, are derived. Comparison with experimental data indicates that the stretched-film concept, although an oversimplification of the physical situation, is most successful in correlating the data.

Mass Transfer Rates in Algol Binaries Deduced from Their Period Changes

Average mass transfer rates in 23 Algol binaries are derived by analyzing their observed period changes within the framework of the Biermann-Hall period change model. These are compared with thermal mass loss rates computed from the dimensions which the cooler (mass-losing) component had at the onset of mass outflow. The agreement is quite good and confirms a claim made earlier that the subgiant components in Algol binaries are losing mass at a rapid (thermal) rate, not at a slow (nuclear) rate.

Natural Convection Mass Transfer Adjacent to Vertical and Downward-Facing Inclined Surfaces

Experimental measurements for natural convection mass transfer adjacent to vertical and downward-facing inclined surfaces were performed using an electrochemical technique. The measurements yielded the time average and instantaneous mass transfer rates for the laminar, transition, and turbulent flow regimes along the test surface. The laminar mass transfer measurements were found to agree with both the analytical and experimental results for both the vertical and downward-facing inclined surfaces. The Rayleigh number marking the onset of the transition from laminar flow conditions depended heavily upon the angle of inclination of the test surface. In the turbulent regime the time average local mass transfer coefficient was correlated by the Rayleigh number to 1/3 power.

A mathematical treatment of the effect of particle size distribution on mass transfer in dispersions

AbstractA mathematical model is proposed that takes into account interaction between drops or bubbles in a swarm as well as the effect of particle size distribution. The model is used to solve the equations for unsteady state mass transfer with and without chemical reaction when the drops or bubbles are suspended in a nonextraordinarily purified agitated fluid. Steady state diffusion to a family of moving drops with clean interface and without interaction and chemical reaction has been also analyzed. The model demonstrates the sort of error that may arise when one applies uniform drop size assumptions to drop populations. It is shown quantitatively that this error is usually small when one replaces the variable particle size by the mean. By using variables that can be determined and predicted, the equations presented permit the estimation of diffusion rate per unit area of interface, as well as the average concentration and the total average rate of mass transfer in the disperser under pseudo steady state conditions.

Forced convection mass transfer: Part III. Increased mass transfer from a flat plate caused by the wake from cylinders located near the edge of the boundary layer

AbstractEnhanced rates of mass transfer in the wake region behind detached cylindrical turbulence promoters were investigated with the use of the naphthalene sublimation technique. The maximum increase in the average rate of mass transfer through laminar boundary layers was over 170%. The remarkable feature of these results was that the enhanced rates of mass trasfer persisted for over one hundred and thirty cylinder diameters downstream from the cylinder generating the wake. The observed effect was not only strongly dependent on the free stream velocity and the location of the cylinders relative to the mass transfer surface, but there were marked differences observed between the rate of mass transfer in the wake region behind one and behind two cylinders. These results resemble a “tuning phenomenon” and are believed to be due to Tollmein‐Schlichting instabilities and premature transition.