Vacuum pumps comparison

Four of the many varieties of these units are illustrated in Figure 7.19. Performances and comparisons of five types are given in Tables 7.8-7.9. All of these types also are commonly used as vacuum pumps when suction and discharge are interchanged. 

Figure 10.8 Comparison of CO2 produced during TAP vacuum pump-probe experiments and atmospheric flow experiments for CO oxidation over single Pt particle with the same composition of reactants, (a) A typical set of pump-probe CO2 responses (m/e = 44) for reaction at 140, 170, and 350 C. There is a shift in the amount of CO2 produced during both CO and oxygen pulses as temperature increases, (b) CO2 production observed from atmospheric flow experiment. The CO2 produced while increasing reactor temperature is less than the CO2 produced during reactor temperature decrease as shown by the counterclockwise hysteresis loop, (c) CO2 production observed from vacuum pump-probe experiment The black line represents the total CO2 yield. The circle and diamond points represent the CO2 yield on the oxygen pulse and CO pulse, respectively.

Figure 9 also gives the neutron wall loadings pw and for NUWMAK the value of the power per unit weight p i of the nuclear islands. The reference value taken for the power density is that prevailing in the pressure vessel of pressurized water reactors (PWR). The structure of a PWR is less complex than that of a DT tokamak reactor would be and the materials required for its construction will, with all probability, entail lower specific energy costs than tokamak materials. In addition, the reference volumes chosen here for the tokamak reactors do not include essential subsystems of the nuclear island (e.g., start-up heating, fuel injection, selective vacuum pumps) because too little is as yet known about these. Power density comparisons made on this basis should therefore hardly lead to a pessimistic assessment of the economic chances of the tokamak as a power reactor principle. 

For the performance data of steam-driven eductors, see Foisy, E.C. and Munkittrick, M.T., "Energy Comparison Vacuum Producing Equipment Mechanical Vacuum Pumps Vs. Steam Ejectors," Proceedings from the Fourth Industrial Energy Technology Conference Houston, TX, April 4 7,1982. 

Manual methods of freeze fracture are often useful in providing specimens for study in the SEM. An example of a freeze shattering method was described by Stoffer and Bone [406] for comparison with microtomy results. Polymers immersed in liquid nitrogen were mechanically shattered with a hammer, mounted, vacuum pumped and sputter coated for observation. This simple method is useful if the materials cannot be sectioned. However, fine structural details are not conclusive when specimens are prepared by such methods. 

The comparison of Figures 10.1 and 10.2 shows that a vacuum plant requires a more sophisticated machine equipment than a pressure plant. On the heating and product side, vacuum pumps are required and liquid pumps are required to discharge the heating steam condensate and the product concentrate. Theoretically, fresh product can be sucked in via vacuum depending on the type of evaporator another pump will be required for the feed. 

For these parameters, the equations predict a much higher vacuum (24.5 in Hg or 230 percent of the shortcut method) than the gravity-discharge case. Of course, different tank dimensions and pump characteristics coiild give different comparisons between cases. If conditions are such that the pump can completely empty the tank before backflow occurs, the vacuum is Rest calculated from Eq. (26-57). 

Lines in vacuum service, 135—141 Line symbols, 17, 23 Numbering, 23 Lined centrifugal pumps, 171 Liquid-solid particle, separators, 228 Baffle type specifications, 248 Baffle type, 247, 248 Centrifugal, 256, 259-261 Chcvron-vanc, 248, 235 Comparison chart, 230 Cyclone, 259 Specification form, 268 Vane, 259 Wire mesh, 246 York-vane, 248 Low pressure storage... 

J. P. Bare, B. Johl, and T. A. Lemke, Comparison of Vacuum-Pressure vs. Pump Dispense Engines for CMP Slurry Distribution, Proceedings of SEMlCONtWesl Contamination in Liquid Chemical Distribution Systems Workshop (July, 1998). 

This experiment presents the measurement of uranium with an inductively coupled plasma mass spectrometer (ICP-MS). In this system, a nebulizer converts the aqueous sample to an aerosol carried with argon gas. A torch heats the aerosol to vaporize and atomize the contents in quartz tubes. The atoms are ionized with an efficiency of about 95% by an RF (radiofrequency) coil. The plasma expands at a differentially-pumped air-vacuum interface into a vacuum chamber. The positive ions are focused and injected into the MS while the rest of the gas is removed by the pump. The ions are then accelerated, collected, and measured as a function of their mass. Losses at various stages, notably the vacuum interface, result in a detection efficiency of about 0.1 %, which is still sufficient to provide great sensitivity. The amounts of uranium isotopes in the sample are determined by comparisons to standards. Because different laboratories have different instruments, the instructor will provide instrument operating instmctions. Do not use the instrument until the instructor has checked the instrument and approved its use. 

Bare J, Johl B, Lemke T. Comparison of vacuum-pressure vs. pump dispense engines for CMP slurry distributionProceedings of SEMICON/West Contamination in Liquid Chemical Distribution Systems Workshop 1998 July. 

The barometer-tube method was improved by Ramsay and Youngs (pig. 3.VIII J). They used a comparison vacuous barometer surrounded by a water-jacket at constant temperature. The barometer tube to contain the liquid was first filled with mercury which was boiled in a water-pump vacuum. Some liquid was introduced and boiled in vacuum to free it from air. More mercury was added and the tube inverted in the mercury trough. The open end had, as shown, a narrower side tube, the wider tube being sealed below. The liquid passed to the top of the mercury.. The tube was heated in a vapour jacket, the liquid being boiled in a bulb at the side under a constant air pressure maintained in a large reservoir. The difference in mercury levels in the two tubes was read, and the level in the vapour tube corrected for temperature and the weight of the small column of liquid above it. 

Shortly after we had run this comparison study, our own aged freeze-drier collapsed into obsolescence. In order to make this method work, the freeze-drier must be specially constructed, without resin in the vacuum chamber and with traps placed in the vacuum line to prevent the back-diffusion of oil vapors from the pump to the vacuum chamber. While we have been awaiting the rejuvenation of our own instrument, rebuilt to these specifications, Michael McKinnon, of our laboratory, has developed a variation of the Russian evaporation method. In this method, as in the freeze-drying method, the great problem is avoiding contamination. Fortimately, when contamination does occur, it seems to affect an entire batch of samples. It is therefore possible to detect the contamination by the judicious use of standards. This method gives values for DOG of the same order as the lowest freeze-drying values or the Sharp (27) direct injection values. 

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