Circulation Patterns

Most ozone is formed near the equator, where solar radiation is greatest, and transported toward the poles by normal circulation patterns in the stratosphere. Consequendy, the concentration is minimum at the equator and maximum for most of the year at the north pole and about 60°S latitude. The equihbrium ozone concentration also varies with altitude the maximum occurs at about 25 km at the equator and 15—20 km at or near the poles. It also varies seasonally, daily, as well as interaimuaHy. Absorption of solar radiation (200—300 nm) by ozone and heat Hberated in ozone formation and destmction together create a warm layer in the upper atmosphere at 40—50 km, which helps to maintain thermal equihbrium on earth. 

Fig. 11. Computer-simulated recirculating patterns in a mixing tank with full baffles (a) elevation view shows circulation patterns generated by turbine blades (b) plane view shows the effect of the baffle on the radial velocity vectors above the turbine blades.

The overall circulating pattern, including the circulation time and the deviation of the circulation times, can never be neglected. No matter what else a mixer does, it must be able to circulate fluid throughout an entire vessel appropriately. If it cannot, then that mixer is not suited for the task being considered. 

In the transition region [Reynolds numbers, Eq. (18-1), from 10 to 10,000], the width of the baffle may be reduced, often to one-half of standard width. If the circulation pattern is satisfactory when the tank is unbaffled but a vortex creates a problem, partial-length baffles may be used. These are standard-width and extend downward from the surface into about one-third of the liquid volume. 

Baffle generally a flat plate attached to and perpendicular to the wall of a mixing vessel to alter the fluid circulation pattern and prevent excessive swirl of the fluid in the vessel. ... 

In the stratification strategy the supply air is used to substitute the outgoing air from the ventilated (in most cases occupied) zone, thus preventing circulation patterns between the zones. The supply air has to be distributed in such a way that the buoyancy flows are not disturbed. Exhaust air openings are to be located downstream in order to avoid reverse currents within the room. The location of the contaminant sources and the heat sources causing density differences must be the same in order to carry out the contaminants with equal or higher density than air. 

Figure 27.12 Room air circulation patterns, (a) Grilles on corridor wall, (b) Sill outlets, (c) Floor outlets, (d) Ceiling slots...

Increasing TZ to values > 1 ( 10 - 20) induces a distinct change in behavior a circulation appears, in the form of two symmetrically positioned vortices behind the cylinder (see figure 9.2). It is believed that the circulation pattern appears suddenly at some threshold value of TZ,. Also notice that the fluid velocity at any given point in space is still constant. 

Stirred tank reactor the most common type of bioreactor used in industry. A draught is fitted which provides a defined circulation pattern. 

The possibility that the climatic future might feature a change in frequency of weather extremes underscores the desirability for climate models capable of predicting the future spectrum of prevailing circulation patterns. Weather extremes such as drought or excessive cold are the products of certain persistent (blocking) planetary wave patterns. In fact, it is reasonable to assume that past climatic... 

Although the general circulation patterns are fairly well known, it is difficult to quantify the rates of the various flows. Abyssal circulation is generally quite slow and variable on short time scales. The calculation of the rate of formation of abyssal water is also fraught with uncertainty. Probably the most promising means of assigning the time dimension to oceanic processes is through the study of the distribution of radioactive chemical tracers. Difficulties associated with the interpretation of radioactive tracer distributions lie both in the models used, nonconservative interactions, and the difference between the time scale of the physical transport phenomenon and the mean life of the tracer. 

Oceanic circulation. The process of ocean circulation described earlier yields an ocean circulation pattern that results in progressively older deep water as the water passes, in sequence from the Atlantic, Indian, to the Pacific Ocean. Surface water returns relatively quickly to the place of origin for the deep water. 

The superposition of the vertical biological cycle on the horizontal ocean circulation pattern leads to three general features in the distribution of the elements involved in this cycle. 

There are two important consequences of this superposition of biological cycling on the ocean circulation pattern that show up in the sediments. 

In the previous studies it was considered that the climate change has been reflected by the changes in ocean circulation pattern, ice volume, albedo, and weathering. Many... 

To solve this problem, we need to make computer calculations on the long-term global carbon cycle including the effect of terrestrial biota, ocean circulation pattern, and metamorphic activities which are not included in Kashiwagi et al. (2000) s computation. 

Henry H.R. and Kahout, F.A., Circulation patterns of saline groundwater affected by geothermal heating as related to waste disposal, in Symposium on Underground Waste Management and Environmental Implications, Houston, TX, Cook, T.D., Ed., American Association of Petroleum Geologists, 18, 1973,... 

The solids circulation pattern and solids circulation rate are important hydrodynamic characteristics of an operating jetting fluidized bed. They dictate directly the solids mixing and the heat and mass transfer between different regions of the bed. 

Solids Circulation Pattern. Yang et al. (1986) have shown that, based on the traversing force probe responses, three separate axial solids flow patterns can be identified. In the central core of the bed, the solid flow direction is all upward, induced primarily by the action of the jets and the rising bubbles. In the outer regions, close to the vessel walls, the solid flow is all downward. A transition zone, in which the solids move alternately upward and downward, depending on the approach and departure of the large bubbles, was detected in between these two regions. 

The solids circulation patterns were investigated with a force probe developed in-house. Typical force probe responses are presented in Figs. 43 and 44 for a probe located at 0.13 m from the jet nozzle and with different penetrations into the bed for an air tube velocity of 45.7 m/s. Sincetheforce probe is directional, the upward solids movement will produce a positive response from the probe and vice versa, the magnitude of the response being an indication of the magnitude of solids circulation rate. The number of major peaks per unit time is closely related to the actual bubble frequency in the bed. 

Yang, W. C., Ettehadieh, B., and Haldipur, G. B., Solids Circulation Pattern and Particles Mixing in a Large Jetting Fluidized Bed, AIChE J., 32 1994 (1986)... 

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