Herman Branover

Promising applications of the liquid metal MHD energy conversion technology

Applications of the liquid-metal MHD (magnetohydrodynamic) energy conversion technology that could benefit from its unique features are reviewed with emphasis on applications that might be realized in the relatively near future and on the OMACON (optimized magnetohydrodynamic conversion) concept. Included among the promising applications are cogeneration, energy recovery from industrial processes involving the use of molten metals, energy conversion from fluidized bed combustors, supercritical steam cycles, electricity generation at peak demand hours, solar energy utilization and seawater desalination. The diversity of promising applications identified suggests that the liquid metal MHD technology has a good change for improving energy utilization. Further studies are required to quantify the attainable improvement.<<ETX>>

On the universality of large-scale turbulence

Large-scale three-dimensional turbulence is a challenge to researchers, being one of the most complicated aspects of turbulence studies. The universal large scales behavior connected with the inverse energy cascade in two-dimensional turbulence has been known for about 35 years and studied experimentally and numerically. We have revealed the universality of three-dimensional large-scale turbulence properties experimentally and described it theoretically. A rigorous solution of this problem in the presence of an energy source gives scaling exponents −4/3 for velocity correlations and 1/3 for energy spectra of the large-scale turbulence. Such spectra are also observed in atmospheric air flows under different conditions—stable, convective, in cirrus clouds. The revealed physical phenomenon is important for the development of turbulence theory complementing the results obtained for its smaller scales.

Peculiarities of turbulence in a flow with vortices

Abstract In the atmospheric boundary layer there exist groups of roll vortices contributing considerably to the momentum transfer, motion properties, etc. There are data pointing to an important role of such vortices in the formation of such a dangerous extreme weather event (EWE) as a tornado. It is known that helical turbulence mode is the cause of the similarity of atmospheric and magnetohydrodynamic turbulence. To clarify the peculiarities of EWE origination, experimental studies of MHD turbulence were carried out under laboratory conditions.

Local mode of copper-nickel alloy interaction with a turbulent liquid lead flow

The process of local interaction of copper with a turbulent lead flow is described in [1]. The local character of the process is mainly due to two factors, namely, to a decrease in the free energy of copper grain boundaries at the adsorption of liquid lead film [2], and to the presence of pressure fluctuations at the copper/turbulent liquid metal flow interface. The process is characterized by two features—washing-out of copper macroparticles (grains) by the flow and formation of a wavy relief on a copper sample surface due to the action of turbulent flow. As shown experimentally, such a character of copper dissolution is observed when a certain critical flow rate is exceeded, its value being a function of temperature. Here the kinetic mode of the process is realized. For the purpose of further clarification of the nature of the process, we have studied the behavior of nickelcopper alloy (Monel 400—Table I) in a turbulent lead flow. The samples under study had a shape of rings 4 mm thick with the outer and inner diameters of 33 mm and 26 mm, respectively. The samples were polished and degreased with acetone. Tests were carried out by the rotating disk method described in [3]. Test conditions: temperature 450◦C, sample rotation rate −2140 rpm. The test container for molten lead (99.97%) was made of carbon steel. Melt volume was ∼1 liter. Nitrogen (99.7%) was passed through it above the melt surface. Gas flow rate was 4 l min−1. Experiment duration was 1–3 h. The samples were analyzed by optical and scanning electron microscopy (JEOL JSM-35CF with energy dispersive spectrometer). Fig. 1 shows a typical structure of the alloy after its interaction with lead flow. This structure is quite analogous to that of copper samples after a test in similar conditions (see, e.g. [1]). Really, in both cases a wavy relief of the sample surface is formed. The appearing structures of heterogeneous zones adjacent to copper or to the alloy, which consist of lead matrix with metal grains distributed in it, are also similar. As EPMA has shown, this analogy is so profound that metal grains composition in both cases is, on the whole, similar and corresponds to that of practically pure copper. The unexpectedness of the obtained result is mainly due to practically the same solubility of copper and nickel in lead [4, 5]. However, there is an essential difference between the structures under discussion. It consists in the presence of a transition zone on the boundary between monel and the composite layer consisting of lead matrix with metal grains distributed in it (Fig. 1). The changes in the concentrations of main components of the system within the mentioned transition zone and its vicinity