Live flows

High-viscosity, short-lived flow of cohesionless grains, supported by upward moving pore water Cohesionless sediment supported by upward escape of pore waters as flow collapses and freezes, very short Kved... 

Additional benefits of lower wall angles and smaller outlets may be gained by relaxation of the transverse flow channel to a slot outlet, provided that the slot develops fuUy live flow. 

Even a mass flow hopper has a significant velocity gradient across the converging section of the container and can preferentially draw-down fluidised material through the bed if this velocity differential reaches near the surface. The reason is that flow pressures of a fluidised mass are hydrostatic, whereas the lateral pressures of gravity flow of a normal media are much less than the vertical pressures. A depression in the flow channel that admits a bulk material in a fluid condition will therefore exert radial pressures mush in excess of the non-fluid product and progressively penetrate the flow channel. To counter this tendency, the cross section of the live flow channel should be as large as practical and have minimum velocity differences. Alternatively, an accelerated de-aeration device should be fitted in the centre of the flow channel. 

Exciting developments based on electromagnetic induction raced along from that time, giving us the sophisticated products our everyday lives depend on. During most of the period productive uses for eddy current technology were few and few people believed in it as a usefiil tool eddy currents caused power loss in electrical circuits and, due to the skin effect, currents flowed only in the outer surfaces of conductors when the user had paid for all the copper in the cable. The speedometer and the familiar household power meter are examples of everyday uses that we may tend to forget about. The brakes on some models of exercise bicycle are based on the same principle. 

Most chemically reacting systems tliat we encounter are not tliennodynamically controlled since reactions are often carried out under non-equilibrium conditions where flows of matter or energy prevent tire system from relaxing to equilibrium. Almost all biochemical reactions in living systems are of tliis type as are industrial processes carried out in open chemical reactors. In addition, tire transient dynamics of closed systems may occur on long time scales and resemble tire sustained behaviour of systems in non-equilibrium conditions. A reacting system may behave in unusual ways tliere may be more tlian one stable steady state, tire system may oscillate, sometimes witli a complicated pattern of oscillations, or even show chaotic variations of chemical concentrations. 

Olah and Overchuk also attempted to discover evidence of slow mixing by carrying out reactions in high-speed flow systems. Evidence, including the isolation of dinitro compounds (> i %), was indeed found, but held to show that the effect of imperfect mixing was only minor. The reactions were, unfortunately, too fast to permit determinations of absolute rates (half-lives of about io s). 

Both projects have lives of 10 years and constant positive net annual cash flows Acf of 2069 and 1558 for projec ts J and K respec tively. The corresponding (NPV)s at a discount factor of 10 percent are + 2710 and + 2560 respectively. These data are summarized as follows ... 

In this case, the lives of the machines are unequal, and the comparison is conveniently made on the basis of capitalized cost. This puts lives on the same basis, which is an infinite number of years. The net annual cash flows generated by each machine are equal. 

For many years, companies and countries have lived with the problem of inflation, or the faUing value of money. Costs—in particular, labor costs—tend to rise each year. Failure to account for this trend in predicting future cash flows can lead to serious errors and misleading profitabihty estimates. 

Cork compositions 250 Low cost. Truly compressible materials which permit substantial deflections with negligible side flow. Conform well to irregular surfaces. High resistance to oils good resistance to water, many chemicals. Should not be used with inorganic acids, alkalies, oxidizing solutions, live steam. 

Passive corrosion caused by chemically inert substances is the same whether the substance is living or dead. The substance acts as an occluding medium, changes heat conduction, and/or influences flow. Concentration cell corrosion, increased corrosion reaction kinetics, and erosion-corrosion can he caused by biological masses whose metabolic processes do not materially influence corrosion processes. Among these masses are slime layers. 

Mott played a major part, with his collaborator Frank Nabarro (b. 1917) and in consultation with Orowan, in working out the dynamics of dislocations in stressed crystals. A particularly important early paper was by Mott and Nabarro (1941), on the flow stress of a crystal hardened by solid solution or a coherent precipitate, followed by other key papers by Koehler (1941) and by Seitz and Read (1941). Nabarro has published a lively sequential account of their collaboration in the early days (Nabarro 1980). Nabarro originated many of the important concepts in dislocation theory, such as the idea that the contribution of grain boundaries to the flow stress is inversely proportional to the square root of the grain diameter, which was later experimentally confirmed by Norman Fetch and Eric Hall. 

Kehlhofer explains that the pre-heating loop must be designed so that the heat extracted is. sufficient to raise the temperature of the feed water flow from condenser temperature T to Ta (see Fig. 7.6). The available heat increases with live steam pressure Ipf), for selected 7 b(= Ta) and given gas turbine conditions, but the heat required to preheat the feed water is set by (Ta — T. ). The live steam pressure is thus determined from the heat balance in the pre-heater if the heating of the feed water by bled steam is to be avoided but the optimum (low) live steam pressure may not be achievable because of the requirement. set by this heat balance. 

After closing A and B, the operators were instructed to go outside and close the corresponding hand valves a and b. This destroyed the interlocking. One day an operator could not get A and B to close. He had forgotten to open C. He decided that A and B were faulty and closed a and b. Flow stopped. The tubes in the furnace were overheated. One of them burst, and the lives of the rest were shortened. 

---