Slots, pressure

Solve for the combined riser, reversal, annulus, and slot pressure drop by ... 

The slot pressure drop through the dry cap increases nearly linearly with cap diameter. 

In extmsion coating a polymer is extmded from a slot die into the nip of two roUs where it is bonded to a substrate under pressure (Fig. 6). A corona discharge may be appUed to the substrate just prior to the nip to enhance adhesion. Polyethylene or ionomer are the most common resins used in extmsion coatings. They provide improved moisture barrier (on paper), or sealabUity (on foU, polypropylene, or polyester). When a second substrate is introduced to the nip, laminated stmctures may be produced. 

In a free jet the absence of a pressure gradient makes the momentum flux at any cross section equal to the momentum flux at the inlet, ie, equations 16 and 17 define jet velocity at all points. For a cylindrical jet this leads to a center-line velocity that varies inversely with (x — aig), whereas for slot jets it varies inversely with the square root of (x — Xq As the jet proceeds still further downstream the turbulent entrainment initiated by the jet is gradually subordinated to the turbulence level in the surrounding stream and the jet, as such, disappears. 

Several wick stmctures are in common use. First is a fine-pore (0.14—0.25 mm (100-60 mesh) wire spacing) woven screen which is roUed into an annular stmcture consisting of one or more wraps inserted into the heat pipe bore. The mesh wick is a satisfactory compromise, in many cases, between cost and performance. Where high heat transfer in a given diameter is of paramount importance, a fine-pore screen is placed over longitudinal slots in the vessel wall. Such a composite stmcture provides low viscous drag for Hquid flow in the channels and a small pore size in the screen for maximum pumping pressure. 

In general, once the curtain of filaments has been produced, it is necessary to attenuate the filaments in order to provide strength and resistance to deformation. The most commonly practiced approach is to utilize a single slot, which is at least the width of the curtain, at a point below the spinning plate and above the laydown screen. There are two practical approaches taken. The first utilizes the injection of low pressure air at a point above the slot so that the fibers attain sufficient acceleration in the slot to provide adequate draw (22) (Fig. 7). The second utilizes a low pressure vacuum below a venturi to provide the pressure differential requited for sufficient acceleration and resulting attenuation (30). 

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. 

Increase pressure drop across the slot this can be accomplished by lengthening the lips (Fig. 6-35). 

For large motors, the practice is to wind the stator with formed coils (Figure 9.2). The coils are pre-formed and cured before insertion into the stator slots. They are insulated with resin-rich glass and mica paper tapes. The process of impregnation is therefore termed resin-rich insulation. The completed formed wound stator is then heated to remove trapped moisture and finally impregnated in varnish class F or H as required, under vacuum and pressure. The stator is then cured in an oven as described above. The process of insulation and curing conforms to powerhouse insulation requirements. This practice facili-... 

Total pressure surveys were made downstream of the stators in both the radial and circumferential directions to determine the effect of coolant on stator losses. The wake traces for the stator with discrete holes and the stator with trailing edge slots show that there is a considerable difference in total... 

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