Viscous Power Losses Research Articles

Further Studies of a Low-Melting Point Alloy Used in a Liquid Metal Current Collector

Low-melting point bismuth-based alloys are potential replacements for NaK <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">78</inf> as liquid metal slip ring material because of their lower reactivity and potentially greater hydrodynamic stability. This paper describes experiments of one such alloy in a model of a 300-kW superconducting homopolar motor using close clearance braid-type collectors. Slip ring tip velocities varied from 5 to 20 m/s and currents ranging from 500 to 2500 A. Viscous power losses tend to follow a simple turbulent model. In all, the data supports the use of low-melting point alloys (LMPA) us an alternative to NaK <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">78</inf> .

Magnetohydrodynamic liquid-metal flows and power losses in a rectangular channel with a moving conducting wall

Fully developed, viscous liquid-metal flows and power losses in a rectangular channel in a uniform, external magnetic field were studied for moderate Hartmann numbers and different channel aspect ratios. The channel was assumed to have insulating side walls parallel to the field, a perfectly conducting moving top wall, and a stationary bottom wall perpendicular to the field. Exact series solutions and numerical calculations are presented for velocity profiles, induced magnetic field distributions, current densities, voltage profiles, and viscous and joulean power losses. The joulean and viscous dissipation are computed from squared quantities involving infinite series with double summations for finite M. The diverging series derived for the viscous power losses is made convergent by slightly modifying the velocity profile of the conducting fluid at the moving interface. The effect of the applied field is to produce an eddy current that accelerates the bulk fluid to velocities greater than those without the field, but because of the presence of the side walls, the velocities are less than in one-dimensional couette flow. Except at small aspect ratios and Hartmann number, almost the entire power loss resulted from the component of the induced current parallel to the applied field.

Transmission of Power by Sinusoidal Wave Motion through Hydraulic Oil in a Uniform Pipe

An analysis is made of the viscous power losses in a liquid-filled pipe under oscillatory compressible flow conditions, particular attention being paid to Shell Tellus 27 oil in a 7/8 in diameter pipe, 80 ft long. Using an effective friction coefficient to take into account oscillating flow, the efficiency and the power-carrying capacity of the pipe are calculated for four discrete values of resistive output load. It is shown that if the load is not equal to the characteristic impedance of the pipe, then the efficiency is reduced and the power capacity depends upon the frequency of operation of the pipeline. A mismatched load should be resistive with the pipe preferably tuned to the quarter wavelength frequency supplied from a constant pressure generator. Relative power output increases under these conditions are achieved at the expense of efficiency and increased pipe pressure. Agreement between theory and experiment for the load conditions considered is good.