Flows ranges

After extmsion, molten polymer is filtered through screen packs. The polymer may be separated iato different melt flow ranges to produce more uniform product grades. 

The Colebrook foriTuila (Colebrook, y. Inst. Civ. Eng. [London], II, 133-156 [1938-39]) gives a good approximation for the/-Re-( /D) data for rough pipes over the entire turbulent flow range ... 

A good approximation to the friction factor in the turbulent flow range is... 

Rotameters require no straight runs of pipe before or after the point of installation. Pressure losses are substantially constant over the whole flow range. In experimental work, for greatest precision, a rotameter should be cahbrated with the flmd which is to be metered. However, most modern rotameters are precision-made so that their performance closely corresponds to a master cahbration plot for the type in question. Such a plot is supphed with the meter upon purchase. 

This design permits variable primaiy nozzles, which enable the attainment of high efficiency over a wide flow range. 

Wide useful flow range by varying stator blade angles... 

Figure 3-10 shows a similar performance map for an axial-flow compressor. Note the smaller operational flow range for the axial-flow compressor as compared to the centrifugal compressor. Figure 3-11 shows a typical compressor map presented from a slightly different viewpoint. On this map. 

The reciprocating compressor is generally in the lower flow end of the compressor spectrum. Inlet flows range from less than 100 to approximately 10,000 cfm per cylinder. It is particularly well-suited for high-pressure service. One of the highest pressure applications is at a discharge pressure of 40,000 psi. Above approximately a 1.5-to- i pressure ratio, the reciprocating compressor is one of the most efficient of all the compressors. 

The Spray tree is used to distribute water over the wet deck in counterflow cooling towers. It can consist of a single header fitted with spray nozzles or, it can utilize spray branches with nozzles for wider coverage. Spray nozzle designers seek minimal pressure requirements and uniform coverage over wide flow ranges. 

In the turbulent flow range, friction loss in glass pipe is 70 to 85 percent of clean steel. 

Frame Nominal Flow Range (cfm) Nominal Max No. of Casing Stages Max Casing Pressure (psig) Nominal Speed (r/min) Nominal Polytropic Efficiency Nominal H/N (per stage) Maximmn Q/N... 

Linked characterized valves. The relationship between angular rotation of the valve spindle and open area of the valve can be adjusted over different portions of the flow range using a series of screws. In this way, the air/gas ratio can be characterized to any desired profile over the whole firing range. These valves are suited to fully modulating systems and are commonly used on steam boilers. 

Most plate heat exchanger designs fall into the viscous flow range. Considering only Newtonian fluids since most chemical duties fall into this category, in laminar ducted flow the flow can be said to be one of three types ... 

Figure 32.46 demonstrates how variable-speed drives will give a wide range of flows. Systems supplied by positive displacement pumps do not usually need wide flow ranges, but the same principle of parallel operation will apply. 

Factory tests establish the pressure head, power, efficiency and NPSH over the complete flow range the pump can deliver running at design speed. British Standard, DIN standard or ANSI standard codes or national variations from such main codes lay down the manner of test procedure, and a minimum requirement is quite often defined by industry codes such as API 610. This is not the place to discuss instrument accuracy, as the codes lay down the limits possible from conventional instruments. There are two main classes of test the commercial requirements normally possible in the maker s test plant and high-accuracy tests that are only possible by using substandard instruments and very sophisticated techniques. 

These steps occur in the sequence shown and the slowest step determines the deposition rate. The rules of the boundary layer apply in most CVD depositions in the viscous flow range where pressure is relatively high. In cases where very low pressure is used (i.e., in the mTorr range), the rules are no longer applicable. 

XlylmnkT/ird ), or h = [TT[i 2RTI2p), as long as substituting the gap-dependent viscosity rather than the bulk viscosity. Because the effective viscosity decreases as the Knudsen number enters the slip flow and transition flow ranges, and thus the mean free path becomes smaller as discussed by Morris [20] on the dependence of slip length on the Knudsen number. 

The power input in stirred tanks can be calculated using the equation P = Ne pnM if the Newton number Ne, which at present still has to be determined by empirical means, is known. For stirred vessels with full reinforcement (bafQes, coils, see e.g. [20]), the only bioreactors of interest, this is a constant in the turbulent flow range Re = nd /v> 5000-10000, and in the non-aerated condition depends only on geometry (see e.g. [20]). In the aerated condition the Newton number is also influenced by the Froude number Fr = n d/g and the gas throughput number Q = q/nd (see e.g. [21-23]). 

Using Eqs. (11) and (2) the stirrer performance and the resultant Newton number Ne for the laminar flow range can be derived with the formula P = 2ti... 

Furthermore, in Searle cylinder systems, secondary currents occur above certain Taylor numbers, resulting in greater power input than that resulting with Eq. (12). Comparison with experimentally determined Ne numbers shows that the laminar flow range in internally driven cylindrical stirrers in the range of radius ratios r2/ri= 1.05-2 is only valid for Taylor numbers Takrit= <400-200 [38]. Above Ta >Takritsecondary currents in the... 

Since many different gas/liquid contactors were used, the experimental conditions differed for each device and the reader is referred to the listing in the original reference [5], The liquid flows range from 10 to 1042 ml h and the gas volume flows from 180 to 25 020 ml h. The corresponding residence times were 0.01-19.58 s. The ratio of carbon dioxide to sodium hydroxide was fixed at 0.4. 

The film diffusion stages (i) and (v) are similar to the external mass transfer stages in leaching and may be dealt similarly (see Section 2.1.3). Solution flow conditions for resin touching the fixed beds are likely to be in the laminar flow range. 

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