Experimental Behavior of Falling Liquid Films at High Surface Tension Numbers

Abstract

The work was made possible by the provision of an S.R.C. research grant and by a studentship from the S.R.C. and Thorn Lighting Ltd. d,, diameter of percolating particles ( L ) d,, diameter .~ of largest particle that can percolate spontaneously ( L ) E,, bulk particle diffusion coefficient ( L 2 T 1 ) kf,k,,kh,k$,, constants Nb, number of bulk particles in system N,, number of bulk particles having separation in region q p , probability q, region R , largest distance between surface of bulk particle and extremity of cage containing bulk particle (L) colation ( L ) R*, critical value of R which, if exceeded, will lead to per- Greek LettersThe application of thin, falling liquid films of lithium to cool the inner walls of future laser fusion reactors has been investigated. In order to extend the existing experimental results on falling films to the higher surface tension numbers characberistic of alkali metals such as lithium, experiments using hot water on a vertical plate were run, primarily in the wavy laminar flow regime. Results show that very low minimum flow rates can fully wet the surface provided that the surface is carefully cleaned and preconditioned. Both the wave inception distance and the equilibrium wave arnplitude decrease as the surface tension number increases for a given flow Reynolds number. Based on these results, the scaling laws for the minimum wetting rate, the wave inception distance, and the equilibrium wave amplitude have been extended up to surface tension numbers of about 10 000.A simple algebraic solution is presented for the volume rate of flow of a power-law non-Newtonian fluid through a concentric annulus in laminar flow. This expression is valid for all values of the flow behavior index n (not just reciprocal integers as in previous solutions) and all values of the annulus aspect ratio (T = R , / R . The present solution allows calculation of either volume flow or pressure loss directly using only a pocket calculator. Previous authors obtained their results in terms of a definite integral which they could not evaluate for arbitrary n values. I t is shown how this integral may be evaluated analytically to obtain a simple algebraic result valid for all n , (T in the range.

Scaling criteria for IFE liquid wall protection scheme simulation

“…However, using hot water to simulate liquid lithium was unsuccessful and showed opposite trend to the theoretical prediction. The experiments concluded that further analytical and experimental research is required to explain the observed behavior [7]. For flow conditions of high surface tension and Reynolds numbers, the asymptotic wave velocities and wave growth rates as a function of film Reynolds number (given by Anshus [6]) are shown in Fig.…”

“…For the liquid metals, the values of the surface tension number are appreciably higher than those of room temperature water, as shown in Table 1. To reproduce the surface tension number of lithium, the temperature of water was raised to 80°C to reduce fluid viscosity [7]. However, using hot water to simulate liquid lithium was unsuccessful and showed opposite trend to the theoretical prediction.…”

Research on the HYLIFE liquid-first-wall concept for future laser-fusion reactors. Final report No. 4, September 1977-March 1979

“…Our initial studies of annular liquid jets [ 3] and thin liquid films on the walls [4] indicated that additional experimentation with sheet jets (and also round jets) would provide a valuable data base for the design of a liquid lithium curtain for a future fusion reactor.…”