Draft ratio

Filaments about 0.12 mm in diameter were obtained from unfractionated high-density polyethylene (Mi] = 8.0 x 104) by a melt-spinning at 220 ° C with a draft ratio of about 17. They were next stretched at 100 °C in polyethylene glycol with a molecular weight of 380—400 to different draw ratios, which are defined as the ratios of the drawn length to the original. NMR spectroscopy was carried out for the drawn filaments randomly packed into a glass tube 18 mm diameter. The three-component analysis of the spectrum at different temperatures was performed the results are discussed in relation to the phase structure of samples. 

Draft ratio n. The ratio between the weight or length of fiber fed into various machines and that delivered from the machines in spun yarn manufacture. It represents the reduction in bulk and weight of stock, one of the most important principles in the production of yarn from staple fibers. 

Fig. 26.19. Critical UKC /ii,crit/r for different mud layers with stopped propeller for model ship D, where mud layer thickness to draft ratio h2/T (a) 0.11 and (b) 0.22 as a function of Depth Proude Number...

The presented crabbing manoeuvre can be examined for the different combinations of main engines (Dead Slow, Slow) and bow thrusters (50% or 100% of maximum available power) settings at shallow water (water depth to ship draft ratio h/T =1.2) and deep water conditions (h/T = 3) and at different distances from the berth. In Figure 1 the assumed distance to the berth is equal to 0.75 ship beam. 

In ports with bigger water depth to draft ratios assumed for the design (maximum for the port) vessel the three layered granular filter of rip rap, a block mat on geotextile or a stone asphalt mat with riprap can be applied (Gijt Broeken, 2005). 

The effect of water depth to draft ratio and influence of rudder angle examined on big physical model with geometrical scale 1 16 was presented in (Abramowicz-Gerigk, 2010 Abramowicz-Gerigk, 2011). The mean axial velocities v of propeller jet behind the rudder in deep water (water depth to ship draft ratio h/T = 3) and shallow water (h/T = 1.2) conditions related to —jet velocity in deep water with rudder angle 0 are presented in Table 1. 

Figure 2. CFD streamlines prediction in the aft and fore parts of the car-passenger ferry during unberthing. Distance from the berth is equal to 0.1 ship breadth, water depth to draft ratio h/T = 1.2 (Abramowicz-Gerigk Burciu, 2011).

Another developmentt reported on the extrusion of a tough low denier PVDF fiber. Three unstretched monofilaments were made from PVDF with different inherent viscosities at 250°C in a plunger extruder illustrated in Fig. 8.38. The die orifice diameter was 0.5 mm. The fiber was stretched at a 3 1 draw ratio by fast-slow roll combination at 120°C. The stretched fibers were wound up at different draft ratios. 

Draft ratio is defined as the ratio of the linear velocity of wind up to the exit velocity of the filament through the orifice. The oriented (stretched) monofilaments were subsequently heat-set for 1 hour at 150°C under tension with an elongation of 2% to retain the orientation. Table 8.37 gives a summary of the properties of the fibers made with different grades of polyvinylidene fluoride tenacities of the three filaments are well above 5 g/denier. 

Mechanics-draft cooling towers normally are designed for L/Q ratios ranging from 0.75 to 1.50 accordingly, the vSues of KaV/L vaiy from 0.50 to 2.50. With these ranges in mind, an example of the use of the nomograph will readily explain the effecd of changing variables. 

The fluidfoil impellers in large tanks require only two baffles, but three are usually used to provide better flow pattern asymmetiy. These fluidfoil impellers provide a true axial flow pattern, almost as though there was a draft tube around the impeller. Two or three or more impellers are used if tanks with high D/T ratios are involved. The fluidfoil impellers do not vortex vigorously even at relatively low coverage so that if gases or solids are to Be incorporated at the surface, the axial-flow turbine is often required and can be used in combination with the fluidfoil impellers also on the same shaft. 

A basic stirred tank design is shown in Fig. 23-30. Height to diameter ratio is H/D = 2 to 3. Heat transfer may be provided through a jacket or internal coils. Baffles prevent movement of the mass as a whole. A draft tube enhances vertical circulation. The vapor space is about 20 percent of the total volume. A hollow shaft and impeller increase gas circulation (as in Fig. 23-31). A splasher can be attached to the shaft at the hquid surface to improve entrainment of gas. A variety of impellers is in use. The pitched propeller moves the liquid axially, the flat blade moves it radially, and inclined blades move it both axially and radially. The anchor and some other designs are suited to viscous hquids. 

The turndown ratio is an indication of the ability of the burner to maintain a stable flame at lower firing rates, and is a ratio of the maximum and minimum firing rates. Turndown can be low for average burners of both natural-and forced-draft burners, 3 1 being a typical figure with 5 1a maximum although up to 40 1 is possible with special burners. 

In general, a fully modulating burner will be thermally more efficient, particularly if it maintains air/gas ratio accurately at intermediate rates. For natural-draft burners this may not be the case, as, in general, the air is not modulated, leading to progressively more excess air at lower rates. 

The draft-tube airlift bioreactor was studied using water-in-kerosene microemulsions [263], The effect of draft tube area vs. the top-section area on various parameters was studied. The effect of gas flow rates on recirculation and gas carry over due to incomplete gas disengagement were studied [264], Additionally, the effect of riser to downcomer volume was also studied. The effect of W/O ratio and viscosity was tested on gas hold-up and mass transfer coefficient [265], One limitation of these studies was the use of plain water as the aqueous phase in the cold model. The absence of biocatalyst or any fermentation broth from the experiments makes these results of little value. The effect of the parameters studied will greatly depend on the change in viscosity, hold-up, phase distribution caused due to the presence of biocatalyst, such as IGTS8, due to production of biosurfactants, etc., by the biocatalyst. Thus, further work including biocatalyst is necessary to truly assess the utility of the draft-tube airlift bioreactor for biodesulfurization. 

The important design parameters for a recirculating fluidized bed with a draft tube were identified by Yang and Keaims (1978a) as the gas bypassing characteristics of the distributor plate, the area ratio between the downcomer and the draft tube, the diameter ratio between the draft tube and the draft tube gas supply, the distance between the distributor plate and the draft tube inlet, and the area ratio of the draft tube gas supply and the concentric solids feeder. The design and operation of a recirculating fluidized bed with a draft tube are discussed below. 

The gas bypassing results obtained from tracer gas injection studies for a flat and a conical distributor plate are shown in Fig. 4. Theflow ratio, FR, is defined as the total gas flow supplied through the draft tube gas supply and the concentric solids feeder divided by the total gas flow supplied through the downcomer gas supply. The A and Y are the actual amounts of gas passing up the draft tube and the downcomer, respectively, determined from the tracer gas injection studies. If FR equals A Y. there is no gas bypassing. If FR is less than A Y. some of the flow supplied through the downcomer gas supply passes into the draft tube. If FR is larger than A/7, the reverse is true. 

Effect of Draft Tube and Downcomer Area Ratio. When a draft tube of 9.55 cm I.D. (downcomer/draft tube area ratio = 7.8) was changed to a draft tube of 5 cm I.D. (downcomer/draft tube area ratio = 30) with other design parameters being the same, the gas bypassing reversed direction, as shown in Fig. 4. With the smaller draft tube (D/dD = 1), the gas bypasses from the draft tube side into the downcomer side for most experimental conditions, except for jet velocities in excess of 76 m/s at the concentric solids feeder with the larger draft tube (D/dD = 1.9), the gas bypasses from the downcomer side into the draft tube side in most experiments. 

Effect of Distance between the Distributor Plate and the Draft Tube Inlet Figure 4 clearly indicates that the gas bypassing phenomenon depends not only on the design parameters but also on the operating conditions. For the conical plate at a distance from the draft tube inlet of L = 21.7 cm, gas bypasses from the draft tube side to the downcomer side at a high flow ratio and reverses the direction at a low flow ratio. When the conical plate was moved closer to the draft tube inlet atL = 14.1 cm, the gas bypassing direction was exclusively from the downcomer side to the draft tube side. 

If substrate inhibition exists, a well-mixed bioreactor is desirable. Mixing in three-phase fluidized bed bioreactors can be increased by adding an external recycle loop, by inserting a draft tube in the reactor, or by decreasing the height to diameter ratio. 

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