Real pumping speed

The real pumping speed is defined as the pumping speed at the processing chamber, i.e. after the conductance losses. For a pump with a speed, Sp, connected to a chamber with a pipe of conductance, C, the real pumping speed, , 5reai. is given by ... 

This determination is assuming that you have a perfectlydesigned vacuum system with no narrow passageways, no extra chambers, no bends, no contamination, and no traps, baffles, or stopcocks. Not much of a vacuum system, but it sure would be fast. Because you are working in the real world, the real pumping time will be slower. To compensate for this slower time, it can be helpful to multiply the above result by 2 or 3 to ensure that the pump will be adequate to handle your system s needs. However, as a tool for approximating the minimum size needed, the above formula is usually sufficient. The final decision of what pump to purchase, as in all selections, will depend on what you are willing to settle for and/or what you can afford. (More information on pump speeds is provided in Sec. 7.3.10.)... 

Table 11.1. Physical properties of hydrocarbon films deposited with a remote electron cyclotron resonance plasma from three different C2Hz source gases at three different dc self-bias voltages 1% np represents the parallel component of the real part of the refractive index as measured by in situ ellipsometry. The film composition is obtained from ion-beam analysis. The total particle number densities nc and n-H are calculated from the stoichiometry and the film thickness. Deposition parameters pressure p = 0.2 Pa adjusted with gas flow at constant pumping speed, absorbed microwave power density P = 10 kW nT3 [17]...

The output control on the closed-loop machine operates continuously, comparing the set output value of the inverters with the real output as measured by the volumetric flow transducers. The system enables pouring only when the parameter is within the limits set by the operator via the keyboard and when it is possible to change the pump speed in less than half a second. 

For each parameter, the pH, DO (dissolved oxygen), ORP (oxidation-reduction potential), temperature, agitation speed, culture volume and pressure can be measured with sensors located in the fermenter. The output of the individual sensors is accepted by the computer for the on-line, continuous and real-time data analysis. Information stored in the computer control system then regulates the gas flow valves and the motors to the feed pumps. A model of a computer control system is shown in Fig. 11. The computer control systems, like the batch systems for mammalian cell culture, seem to level out at a maximum cell density of 10 cells/ml. It may be impossible for the batch culture method to solve the several limiting factors (Table 10) that set into high density culture where the levels are less than 10 cells/ml. 

The piston is directly attached to a device that is pushed inside a cylinder by means of a constant speed rotating motor. The pump delivers a constant flow (without any pulsation) and check valves are not needed. The performance of a syringe pump is dependent on flow rate, syringe size and the architecture involved [24], In the more sophisticated models, the motor speed and rotation can be varied, which offers real advantages for analytical applications involving multi-reagents, sample stopping or flow reversal. 

Answer by Author A criterion for NPSH computation reliability is its repeatability when using a wealth of data. A three-thermocouple redundancy per measurement and the multiplicity of test runs pinpointed the temperatures selected. Then, by using equivalent vapor pressures, and by judiciously establishing pump inlet head losses, no erroneously-negative values of NPSH were realized. Since related suction specific speed values were neither imaginary nor infinite, and, because no hypothetical approaches were necessary to calculate their real values, the NPSH values were deemed reliable. 

Instead of applying the fundamental conservation equations, as described above, another modeling approach is to characterize gas turbine performance by utilizing real steady state engine performance data, as in (Hung, 1991). It is assumed that transient thermodynamic and flow processes are characterized by a continuous progression along the steady state performance curves. This is known as the quasi-static assumption. The dynamics of the gas turbine, e.g. combustion delay, motor inertia, fuel pump lag etc. are then represented as lumped quantities separate from the steady-state performance curves. Very simple models result if it is further assumed that the gas turbine is operated at all times close to rated speed (Rowen, 1983). 

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