Gas entrainment by plunging liquid jets

Abstract

Kosten des Sonncnstromes deutlich ~ber denen des Kohlestroms, und zwar b,~sonders ausgepr~igt bei dem photovoltaischen Verfahren. Dabei ist zu berficksichtigen, dab wegen des Verbundes von Solarkraftwerk und Hilfskapazit~t bereits eine Mischkalkulation f'fir den Sonnenstrom vorliegt und die Investitionskosten niedrig angesetzt wurden. Mit einem unspezifizierten Reserveposten yon 320 Mi.o. DM sch~tzt F.G. Casal [17] die Kosten des reinen Sonnenstroms aus solarthermischen K raftwerken sogar auf 0,51 DM/kWh. Der Durchbruch zur Wirtschaftlichkeit des Sonnenstroms kann nur dann gelingen, wenn sich die Anlagekosten entscheidend senken lassen.

Effects of Salinity on Bubble Cloud Characteristics

“…The bubble cloud in fresh water ( Figure 5) comprises two parts: a part with many large bubbles near the source of bubble formation (i.e., jet), and another part with a few small bubbles further from the source. This observation is consistent with previous experiments, which also showed decreasing bubble sizes away from the air entrainment point [30,38,39]. Comparison of the left-hand sides of panels a, b, and c (fresh water and salinities of 13 and 25 psu) shows that the number of the small bubbles away from the source increases significantly with salinity.…”

“…For example, pouring of water in a tank with a tipping trough or bucket [20,21], or collision of two water waves in a tank [29] simulate intermittent breaking events and episodic (discrete) formation of bubble clouds. In contrast, experimental setups using injection of air through porous media such as glass frits or an aquarium diffuser, vertical or inclined plunging water jets, and weirs (in water jet or waterfall configurations) [15,[30][31][32][33][34], simulate continuous (steady) formation of bubble clouds.…”

“…Thus, bubble clouds produced by episodic mechanisms may contain relatively larger numbers of smaller bubbles than steady, plunging jets. Another concern regarding the use of plunging jets is that the resulting bubble population may reflect the scales of the jet [30].…”

“…The next measurement started only when the salinity values in all volumes (the receiving tank, the supply tank, and the hose) were equal. Our experimental setup does not monitor for the influences of different fluid properties (e.g., density, viscosity, surface tension) on air entrainment [30] as salt is added. However, Chanson et al [36] have shown that such influences are "negligibly small."…”

Bubble Entrainment and Dispersion in Plunging Jet Flows: Freshwatervs.Seawater

“…The mechanisms of bubble entrainment depend upon the jet velocity at impact, the physical properties of fluid, the jet nozzle design, the length of free-falling jet, and the jet turbulence. Basic reviews (BIN, 1993;CHANSON, 1997) highlighted the lack of information on the entrained bubble size distributions. Further, physical modeling of plunging jet flows remains subject to scaling effects, which have not been properly explained.…”