Root diameter

Plate thickness is an important factor in electroplating, in terms of both performance and economics. Corrosion resistance, porosity, wear, appearance, and several other properties are proportional to plate thickness. Minimum plate thicknesses are, or should be, specified as should the location, or check-point, where the thickness is to be measured. In some appHcations, such as threaded fasteners, maximum thicknesses should be specified. Root diameters of finer machine threads can be adversely affected by as Htde as 10 p.m of plating. 

D Diameter for outside D for inside D,. for root diameter of finned m ft... 

R Thermal resistance, equals x/kA, 1/UA, l/hA Ri, Ro, R l, R for thermal resistance of sections 1, 2, 3, and n of a composite body Rj for sum of individual resistances of several resistances in series or parallel R -, and for dirt or scale resistance on inner and outer surface respectively Ratio of total outside surface of finned tube to area of tube having same root diameter (s-K)/J (h- F)/Btu... 

Fig. 6. Spatial distribution of net osmoticum deposition rate per mm of tissue water in the apical 10 mm of maize primary roots growing at various vemiculite water contents (see Fig. 3). The data were obtained by dividing rates per mm length (Fig. 5) by the volume of water in each segment. The inset shows root diameter as a function of distance from the apex in the different treatments. Points are means s.d. ( = 5-6). Modified from Sharp et al. (1988, 1989).

Compression of the rubber compound as it travels up the barrel is developed in the extruder by either decreasing the thread pitch but maintaining a constant root diameter, or alternatively by increasing root diameter whilst maintaining constant thread pitch. Each of these situations increases the pressure as the rubber compound travels up the barrel. The last portion of the screw prior to the die entry, however, is maintained at a constant pitch or root diameter to enable stock to stabilise in characteristics just prior to entering the die head, to ensure uniformity for extrusion through the die. Conventional extruder screws achieve a compression ratio of 2.5 1. 

The material of construction for the ET screw is critical in order to provide the proper strength in the event of an improper start-up procedure and to minimize cost. The maximum stress that the screw will experience during operation will be in the feed section where the root diameter is the smallest and the torque is the greatest. The calculation of the power that a screw can transmit safely is provided in Section 10.4.5. This calculation ignores the strength contribution from the flight. The safety factor for this screw made from three different materiais is provided in Table 9.6. 

Calculation of the Particulate Solids Conveying a Screw Feeder The performance of a feed screw of 1.0-in flight diameter, 0.325-in screw root diameter and 1.2-in lead was experimentally executed for LDPE pellets with a bulk density of 0.45 g/cm3 by measuring the mass flow rate in the rotational speed range of 10-215 rpm. The results are shown in the table below. Construct a particulates drag-flow model that calculates with results that are in close agreement with the experimental results. 

Solids Conveying of Nylon in Screw Extruders Consider a 1.991-in-diameter screw with 2-in lead, 1.375-in root diameter, and 0.2-in flight width, conveying nylon pellets with bulk density of 0.475 g/cm3 and a coefficient of friction of 0.25. Assuming no pressure rise, calculate the solids conveying rate (g/rev) at the following conditions (a) no friction between the screw and the solids (b) no friction... 

Calculate the feeding screw throughput rate capacity assuming plug-flow and LDPE pellet bulk density of 0.45 g/cc. The geometrical variables of the feeder screw are barrel diameter, Dj = 1.66 in screw root diameter, /.L 0.325 in and lead,... 

The main degrees of freedom in twin-screw extruder design are geometry (cross-section profile of screw pair), power (torque capacity) and speed (rpm). The essential geometry of any co-rotating twin-screw extruder is defined by two key parameters 1) centerline distance [a] between the shafts, and 2) outer diameter to inner (root) diameter ratio [OD/ID], see Fig. 3. For a fixed centerline, the OD/ID ratio defines the free volume of the extruder. 

The analysis of fin efficiency in radial, or spiral, fins (Figure 6.6) is substantially more complex because of the changing areas for both conduction and convection heat transfer. Again assuming a uniform heat-transfer coefficient, constant fin thickness, and adiabatic fin tip, Gardner [4] obtained the results shown in Figure 6.10, where D and ) are the outside (tip) and inside (root) diameters of the fin, respectively. 

The plain-tube/-factor curves can be used for the corresponding low-hnned tubes for Reynolds numbers above 1000. At lower Re, the retardation of the flow between the fins reduces the /-factor. It is necessary to calculate taking into account the flow area between the fins. The root diameter of the tube (i.e., the tube diameter at the base of the hns) is used in the Reynolds number. The coefficient thus calculated is based on the entire external tube area including hns, but a hn efficiency (calculated by the method of Section 6.2.4.3) must be applied to the hn area. 

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