High turbulence

One of the limitations of the curtain/slot draw process is that the amount of fiber attenuation is constrained due to the short distance generally allowed between the spinnerette and the venturi slot and the use of relatively low pressure air for drawing so as not to induce high turbulence in the area of the laydown. In practical terms this has made the process difficult to adapt for the production of polyester fabrics which inherently require much higher fiber acceleration to attain the desired polyester fiber properties. 

The phase Doppler method utilizes the wavelength of light as the basis of measurement. Hence, performance is not vulnerable to fluctuations in light intensity. The technique has been successfully appHed to dense sprays, highly turbulent flows, and combustion systems. It is capable of making simultaneous measurements of droplet size, velocity, number density, and volume flux. 

Since there are no dead spaces in a SHE, the helical flow pattern combines to entrain any solids and create high turbulence creating a self-cleaning flow passage. 

Breakup in a highly turbulent field (L/velocity) ". This appears to be the dominant breakup process in distillation trays in the spray regime, pneumatic atomizers, and high-velocity pipehne contactors. 

Droplet Breakup—High Turbulence This is the dominant breakup mechanism for many process applications. Breakup results from local variations in turbulent pressure that distort the droplet... 

Flow effects may be pronounced. High-turbulence areas can become preferred attack sites (Fig. 7.17). Erosion-corrosion phenomena are important (Fig. 7.18) (see Chap. 11, Erosion-Corrosion ). 

Spirai Compact, concentric plates no bypassing, high turbulence. Cross-flow, condensing, heating. Process corrosion, suspended materials. 0.8-1.5... 

Impellers should have shapes that minimize high turbulence formation and reduce low-pressure buildup at their tips, which can lead to cavitation. 

Pasquill defined six stabihty classes ranging from highly stable, low-turbulence Class F, to unstable, highly turbulent Class A, and he identified the surfece wind speed, intensity of solar radiation, and nighttime sky cover as being the prime factors controlling atmospheric stabihty. PasquiU then correlated observations of the behavior of plumes in terms of their dispersion with the... 

Wind has a highly turbulent and gusting character. In addition, a time-mean speed varies with the height from the ground and the roughness of the terrain over which the wind passes. The time-mean wind speed profile can be determined using the following expression ... 

One simplified method for determining stack height is a geometric method described in ASHRAE. The geometric method assumes an exhaust plume shape with a lower boundary having a 1 5 slope relative to the horizontal. The stack and plume are raised until the lower plume boundary is above rooftop penthouses, separation zones, and zones of high turbulence. ASHRAE provides equations for the sizes and locations of the separation and turbulence zones. A stack height reduction credit is provided to account for the vertical exhaust momentum. 

High supply air velocities or cool supply air can cause uncomfortable drafts on the worker. Nonuniform supply air velocities with high turbulence intensity may result in decreased capture efficiency, increased contaminant spread, and increased thermal discomfort. 

In industrial ventilation the majority of air velocity measurements are related to different means of controlling indoor conditions, like prediction of thermal comfort contaminant dispersion analysis adjustment of supply airflow patterns, and testing of local exhausts, air curtains, and other devices. In all these applications the nature of the flow is highly turbulent and the velocity has a wide range, from O.l m in the occupied zone to 5-15 m s" in supply jets and up to 30-40 m s in air curtain devices. Furthermore, the flow velocity and direction as well as air temperature often have significant variations in time, which make measurement difficult. 

Attention must be paid to the specific technical problems posed by measuring flow in industrial ventilating systems, such as high turbulence level and long time-variation of mean velocity. The LDA measurement conditions (statistically sufficient number of LDA data, suitably long duration of LDA measurements for recognition of long-term phenomena) must be carefully selected for an appropriate treatment of these problems. 

Operations such as blending, solids-suspension, dissolving, heat transfer and liquid-liquid extraction are typical of systems requiring high flow relative to turbulence, while gas-liquid reactions and some liquid-liquid contacting require high turbulence relative to flow. The case of (1) 100% of suspension—requires head to keep particles suspended and (2) 100% uniformity of distribution of particles—requires head for suspension plus flow for dis-tiibution. 

Generate liguid-liquid dispersions (droplets) Highly Turbulent NRe > 100,000 Low Turbulence Nlie < 100,00 2 six-element modules 3 six-element modules... 

For highly turbulent gas mixing in an enclosure and the vent area is restricted to one end of the elongated enclosure, ratio of length-to-diameter should not exceed 2, or... 

In elongated confined vessels, with one end closed and the opposite end open or removable, when an explosion begins at or near the closed end, the rapid movement of the flame front caused by the high volume from combustion wall cause displacement of the unburnt mixture ahead of it. Apparently this characteristic is independent of the nature of the combustible material [54], and the velocity can reach 80%-90% of the flame velocity, in part due to the high turbulence generated in the unburnt mixtures. 

Other factors to account for topography with regard to valley or hillside sites should include possible inversion and failure to disperse pollutants. Temperature inversion occurs when the temperature at a certain layer of the atmosphere stays constant, or even increases with height, as opposed to decreasing with height, which is the norm for the lower atmosphere. Inversions may occur on still, clear nights when the earth and adjacent air cools more rapidly than the free atmosphere. They may also occur when a layer of high turbulence causes rapid vertical convection so that the top of the turbulent layer may be cooler than the next layer above it at the interface. 

The tube-side inlet to an exchanger, i.e. the tube ends, is a highly turbulent region and nylon ferrules in the tube ends of the inlet pass have been used in cupro-nickel-tubed condensers to prevent erosion. Where the flow is two phase the same rules will apply except that an erosion velocity limit is more difficult to specify. 

So far as possible, components that operate in highly turbulent-flow conditions should be designed with a view to eliminating cavitation and/or impingement erosion attack. 

Fresh water highly turbulent and containing dissolved oxygen 53-8-161-4... 

---