Air turbulence

The air jet textured yam process is based on overfeeding a yam into a turbulent air jet so that the excess length forms into loops that are trapped in the yam stmcture. The air flow is unheated, turbulent, and asymmetrically impinges the yam. The process includes a heat stabilization zone. Key process variables include texturing speed, air pressure, percentage overfeed, filament linear density, air flow, spin finish, and fiber modulus (100). The loops create visual and tactile aesthetics similar to false twist textured and staple spun yams. 

Inlet Piping Configurations. An incorrect piping configuration can create undesirable flow distortions that, especiaUy for double-suction pumps, means turbulence. Air pockets trapped in the pipe can cause uneven flow, vibrations, and pump damage. 

Shells, clams, wood fragments, and other biological materials can also produce concentration cell corrosion. Additionally, fragments can lodge in heat exchanger inlets, locally increasing turbulence and erosion-corrosion. If deposits are massive, turbulence, air separation, and associated erosion-corrosion can occur downstream (see Case History 11.5). 

Shepelev, L A., and M. D. Tarnopolsky. 1965. Turbulent air jet spreading in the confined space. In Heat-, Gas Supply and Ventilation Proceedings of the Conference. Budivelnik, Kiev. 

Randomness.—The word random is used frequently to describe erratic and apparently unpredictable variations of an observed quantity. The noise voltage measured at the terminals of a hot resistor, the amplitude of a radar signal that has been reflected from the surface of the sea, and the velocity measured at some point in a turbulent air flow are all examples of random or unpredictable phenomena. 

Pulverized fuel coal burners (typically turbulent air burners, vertical burners, or nozzle burners) receive hot primary air containing the PF and introduce the mixture to secondary air in such a way that it provides a stable flame. The flow rates of both primary and secondary air are controlled by dampers. An ignitor is required to initiate combustion, and the flame front is maintained close to the burner, with the heat of combustion used to ignite incoming PF. A flame safety device electronically scans the flame and initiates corrective action if required. 

Many of the earlier studies of mass transfer involved measuring the rate of vaporisation of liquids by passing a turbulent air stream over a liquid surface. In addition, some investigations have been carried out in the absence of air flow, under what have been termed still air conditions. Most of these experiments have been carried out in some form of wind tunnel where the rate of flow of air and its temperature and humidity could be controlled and measured. In these experiments it was found to be important to keep the surface of the liquid level with the rim of the pan in order to avoid the generation of eddies at the leading edge. 

Pasoi in. .. F, Proc. Kov. Soc. A 182 (1943) 75. Eva X>ration from a plane free liquid surface into a turbulent air stream. 

Cohen, L. S., andT. J. Hanratty, 1968, Effects of Waves at a Gas-Liquid Interface on a Turbulent Air Flow, J. Fluid Mech. 31 461. (3)... 

The design and necessary calculations for the labyrinth calorimeter with turbulent air flow but low heat losses, have been presented earlier (7). See Figure 1. The advantage over micromethods such as DSC is that effects of sheet density and caliper of fiber entities... 

Sublimation rates of pure solids into turbulent air streams have been successfully correlated by the Gilliland-Sherwood equation(102) ... 

Fluidized-bed combustion systems use a heated bed of sandlike material suspended (fluidized) within a rising column of turbulent air to burn many types and classes of waste fuels. The vendor claims that this technique results in improved combustion efficiency of high moisture content fuels and is adaptable to a variety of waste -type fuels. The scrubbing action of the bed material on the fuel particle is said to enhance the combustion process by stripping away the carbon dioxide and char layers that normally form around the fuel particle. This allows oxygen to reach the combustible material much more readily and increases the rate and efficiency of the combustion process. 

A turbulent air flow should not be present at each area location. 

The vaporization rates and drag coefficients for 2,2,4-trimethylpentane (iso-octane) sprays in turbulent air streams were determined experimentally by Ingebo (40), who reported that the effect of relative velocity on the evaporation rate was represented by the 0.6 power of the Reynolds number and that the drag coefficient varied inversely with the relative velocity of the drops in the spray. By assuming that the evaporation rate was independent of velocity and the drag coefficient for droplets obeyed Stokes s law, the present author derived a mathematical theory for the ballistics of droplets injected into an air stream for which the velocity varied linearly with distance (57) and... 

Turbulent Air Streams, Natl. Advisory Comm. Aeronaut., TN 3265 (1954). 

H6. Hershman, A., The effect of liquid properties on the interaction between a turbulent air stream and a flowing liquid film. Ph.D. thesis, Univ. Illinois, Urbana, Illinois, 1960. 

Figure 5 Turbulent air and aerosol re-entrainment patterns in a spray chamber...

The aspirator s pumping mechanism is quite sophisticated, and it all begins by water streaming past the water jet nozzle. By decreasing the internal diameter at the point where the water leaves the nozzle, there is an increase in water speed passing this point. Because the MFP of the gas and vapor molecules within the aspirator is much less than the pump dimensions, aerodynamic shear causes air movement in the desired direction. This air movement will occur regardless of whether there is direct contact of the air with the water or not. Additionally, because the boundary between the rushing water is quite turbulent, air is physi-... 

Equation 7.1 describes the case in which the leaf temperature is greater than the temperature of the air when the leaf temperature is less than that of the surrounding turbulent air, heat moves into a leaf. Also, when water condenses onto a leaf, the leaf gains heat. In such cases, the appropriate energy terms in Equation 7.1 change sign. 

There are two types of convection, free and forced (Holman, 2009 Incropera et al., 2007 Kreith and Bohn, 2007). Free (natural) convection occurs when the heat transferred from a leaf causes the air outside the unstirred layer to warm, expand, and thus to decrease in density this more buoyant warmer air then moves upward and thereby moves heat away from the leaf. Forced convection, caused by wind, can also remove the heated air outside the boundary layer. As the wind speed increases, more and more heat is dissipated by forced convection relative to free convection. However, even at a very low wind speed of 0.10 m s-1, forced convection dominates free convection as a means of heat loss from most leaves (0.10 m s-1 = 0.36 km hour-1 = 0.22 mile hour-1). We can therefore generally assume that heat is conducted across the boundary layer adjacent to a leaf and then is removed by forced convection in the surrounding turbulent air. In this section, we examine some general characteristics of wind, paying particular attention to the air boundary layers adjacent to plant parts, and introduce certain dimensionless numbers that can help indicate whether forced or free convection should dominate. We conclude with an estimate of the heat conduction/convection for a leaf. 

For spherical symmetry, can vary only in the radial direction and not with any angle. The heat flux density at a sphere s surface for heat conduction across the air boundary layer followed by heat convection in the surrounding turbulent air then is... 

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