Elucidation of magnetic stabilization of boiling two-phase flow by utilizing the magnetization of the fluid is proposed herein. The effect of magnetic field on the stability of the boiling two-phase pipe flow of the magnetic fluid under a nonuniform magnetic field is investigated both theoretically and experimentally. First, governing equations of boiling two-phase flow based on the unsteady thermal nonequilibrium two-fluid model are presented and analytically solved using a linearization method. The analytical results on stabilization are then inspected experimentally using an experimental apparatus composed of a small test loop. Results of the analytical study on the void waves, show that the stabilization of two-phase flow can be obtained by practical use of the magnetic body force acting on the fluid and by applying the appropriate superficial gas-phase velocity. Those results also show that magnetic stabilization is obtained because the two-phase magnetic body force enhances the diffusion effect of the void waves. It is experimentally clarified that the two-phase flow state can be stabilized and homogenized by magnetization of the fluid and that vapor bubbles can be minutely produced by effective use of the magnetic body force. The axial magnetic field is more effective for stabilization and homogenization of the two-phase magnetic fluid flow than the transverse magnetic field.

The paper presents a new two-dimensional computational approach and results for laminar/laminar internal condensing flows. Accurate numerical solutions of the full governing equations are presented for steady and unsteady film condensation flows on a sidewall inside a vertical channel. It is found that exit conditions and noise sensitivity are important. Even for stable steady solutions obtained for nearly incompressible vapor phase flows associated with unconstrained exit conditions, the noise sensitivity to the condensing surface’s minuscule transverse vibrations is high. The structure of waves, the underlying characteristics, and the “growth/damping rates” for the disturbances are discussed. A resonance condition for high “growth rates” is proposed and its efficacy in significantly enhancing wave motion and heat transfer rates is computationally demonstrated. For the unconstrained exit cases, the results make possible a separately reported study of the effects of shear, gravity, and surface tension on noise sensitive stable solutions.

Internal flow of pure vapor experiencing film condensation on the walls of a straight horizontal duct is studied. The commonly occurring annular case of turbulent (or laminar) vapor flow in the core and laminar flow of the liquid condensate—with or without waves on the interface—is emphasized. We present a new methodology which models interfacial shear with the help of theory, computations, and reliable experimental data on heat transfer rates. The theory—at the point of onset of condensation—deals with issues of asymptotic form of interfacial shear, nonuniqueness of solutions, and selection of the physically admissible solution by a stability type criteria. Other details of the flow are predicted with the help of the proposed modeling approach. These predictions are shown to be in agreement with relevant experimental data. The trends for film thickness, heat transfer rates, and pressure drops are also made available in the form of power-law correlations.

The object of this theoretical investigation is to determine the importance of the nonequilibrium region, which exists at the bubble wall, on the growth of a vapor bubble. All previous investigators concerned with bubble growth have completely neglected this nonequilibrium effect. In another paper [1] Bornhorst and Hatsopoulos investigated the phase-change problem, and the results which were obtained are applied here to solve the special problem of vapor bubble growth. The results are presented in terms of a two-parameter set of curves. These results show that for pressures where experimental results are available, the nonequilibrium effects are within experimental error; however, for pressures which are somewhat lower, the nonequilibrium effects become very important.

The object of this theoretical investigation is to obtain a set of equations which will predict the behavior of a fluid as it changes phase. Irreversible thermodynamics is employed to obtain general rate equations which relate the fluxes and forces across the nonequilibrium region existing at a phase interface. Both plane and spherical interfaces are considered. Experimental means for determining the three transport coefficients which appear in the resulting equations are discussed. Approximate values for the transport coefficients are obtained from kinetic theory arguments. The present analysis is limited to phase-change problems which may be described by linear phenomenological equations; this is so when the change in the driving potentials is small as compared to their value on either side of the phase interface. This restriction is necessary since presently no general theory exists for nonlinear rate processes.

Equations have been developed expressing the critical mass velocity, (G c ) s , and the isentropic expansion coefficient, k, of a single-component, homogeneous vapor-liquid mixture at low pressures in terms of tabulated thermodynamic properties. With these parameters, two-phase flow relations can be developed which are analogous to the relations governing the flow of single-phase compressible fluids, most readily formulated in terms of Mach numbers. The computed values of k for saturated steam agree favorably with those reported in the literature of steam-turbine design.