Speed factor

DP Speed Factor. Pumping-speed efficiency depends on trap, valve, and system design. For gases having velocities close to the molecular velocity of the DP top jet, system-area utilization factors of 0.24 are the maximum that can be anticipated eg, less than one quarter of the molecules entering the system can be pumped away where the entrance area is the same as the cross-sectional area above the top jet (see Fig. 4). The system speed factor can be quoted together with the rate of contamination from the pump set. Utilization factors of <0.1 for N2 are common. 

An optimized relationship is obtained between the beU jar, 60° swing-leaf valve, LN trap, baffle for the oil, and the plane of action for the diffusion pump (DP) top jet. The valve open area equals 0.38 of the cross-sectional area of the inside diameter of the furnace. The volumetric speed factor for water vapor is thus 0.38 x 0.9 crr 0.34, where 0.9 is the Clausing factor. 

In the latitudes occupied by the US the climate is dominated by westerly winds. The basic wind speed may be adjusted to ensure that the risk of it being exceeded is the same for all directions. This is achieved by the wind speed factor Sa. 

T reatment MOISTURE (%) BAKING LOSS (%) SPEED FACTOR (W/T) TENDERNESS (LB/G) SENSORY SCORE HIGHEST 7 = RATE... 

Among many benefits of press instrumentation, formulation fingerprinting is perhaps the most obvious. Compressibility and ejection profiles, as well as dissolution and disintegration curves related to compression force, are unique for each formulation and can be used as a batch record. For process optimization, one can include compression or precompression force and speed factors in experimental design. Compactibility and ejection profiles can be used for excipient and lubricant evaluation. Other useful product development and optimization tools include response surface, Heckel, and force-thickness plots. 

Model Capacity factor Nominal width (in/cm) Screen area Diameter (in/cm) Number of blades Tip speed factor Maximum rpm Maximum horse power... 

A second index is used to define the propensity of the gas to react. This is called the Weaver flame speed factor. It is defined as the ratio between the laminar flame speed of the gas with relation to hydrogen. Thus hydrogen is considered to have a value of 100. The lower the number the lower the flame speed. Weaver speed factor is greatly influenced by the amount of hydrogen in the mixture. 

In general, the flame speed depends upon the kinetics of combustion and hence varies from gas to gas. The H2 flame is the fastest with the normal velocity having the maximum value of about 2.5 m/s. The CO flame has a lower normal velocity in the range of 0.3 to 0.4 m/s. The flame speed rises if the initial temperature of the combustible mixture is increased or the pressure of the system decreased. If the Wobbe number and Weaver flame speed factor are identical for two gases they are completely interchangeable. 

Speed factor bearing bore, mm X r/min Operating temperatures Viscosity ... 

These are called the mass flow factor and the rotational speed factor, respectively. Other texts call them the non-dimensional mass flow and rotational speed. Charts are then plotted of the efficiency, for different pressure ratios and mass flow factors. Lines are plotted on these charts of constant rotational speed factor. The chart for a typical screw compressor (Lysholm) is shown in Fignre 9.4. The lines of constant efficiency are like the contours of a map. Instead of indicating hiUs, they indicate areas of higher operating efficiency. 

So, the horizontal x-axis of Figure 9.4 corresponds to the airflow needs of fuel cells of power approximately 0 to 250 kW. Similarly, if the rotor speed factor is 1000, this will correspond to a speed of about IVOOOrpm. (Note, these units have to run fast, the centrifugal compressors considered in the next section have to turn even faster ). 

We now find the speed and the efficiency of the compressor using the chart. Find the intercept of a horizontal line drawn from pressure ratio — 3 and a vertical line starting from the x-axis at mass flow factor = 1.9. This will be very close to the 600 rotor speed factor line, and also the / = 0.7 efficiency contour . So we can say that the rotor speed is... 

Note that a rotor speed factor of 4500, the value in the optimum operating region, corresponds to 4500 x V298 78000rpm. These are very high-speed devices. 

Notice that if you pick on a constant mass flow (e.g. 1.5) and move up through the map, the rotor speed factor increases as the pressure ratio increases. This again is what would be expected. 

Using the turbine performance chart in Figure 9.9 we can find the efficiency and speed of the turbine. If we find the intercept np from 0.75 on the jc-axis and 2.8 on the pressure ratio axis, we see that it is very close to the rotor speed factor = 5000 line, and in the r] = 0.70 efficiency region. (More or less optimum operating conditions in fact ) So we can conclude that... 

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