Pulsating method

Hie pulsating method of cooling a reactor having a liquid reactive composition can also be applied to a reactor using natural uranium. When a uranium oxide slurry is used as the reactive composition, typical data is as follows ... 

As uranium slurnes tend to erode rotating pump parts, the pulsating method of circulation is particularly useful when slurries are used for the reacting composition. 

When the pulsation amplitude is such as to result in a greater-than-permissible metering error, consideration should be given to installation of a pulsation damper between the source of pulsations and the flowmeter. References to methods of pulsation-damper design are given in the subsection Unsteady-State Behavior. ... 

The no-load test is a very informative method to determine the no-load current, core and pulsation losses, friction and windage losses, magnetizing current and the no-load power factor. The test also reveals mechanical imbalance, if any, performance of the bearings, vibration and noise level of the motor. 

For those installations where a detailed pulsation analysis, API 618 Design Approach 2 or 3, is required,. several consulting companies offer these services. Until the 1980s, the most common method was to perform the pulsation analysis on the analog simulator of the Pipeline and Compres.sor Research Council of the Southern Gas Association. The... 

Example 13-3. Sizing a Pulsation Dampener Using Acoustic Method... 

When using this method, it is necessary to assume an allowable pressure drop though the pulsation drum. This pressure drop does not need to be large (V4 -1 lb). However, the higher the allowable pressure drop, the smaller the resulting bottle, because the diameter and the length of the drum vary as (pressure drop) or the volume of the drum varies as (pressure drop) . ... 

Pp = pressure pulsation magnitude, peak-to-peak, psi = pulsation attenuation by area-ratio method, or... 

Pulsation Dampener or Smge Drmn, 581 Common Design Terminology, 582 Applications, 585 Internal Details, 591 Design Method — Smge Drirnis (Nonacoustic), 591 Single-Compression... 

Chain Tension. All chain drives should have some means of controlling the chain sag caused by normal joint wear. This is of utmost importance when the drive is subject to shock or pulsating loads or to reversals in direction of rotation. The most common methods taking up chain slack are (1) drive units mounted on adjustable base plat, slide rails, or similar units these are used extensively in motor-driven applications and (2) the use of adjustable idlers (Figure 3-40) and chain tensioners. 

In order to evaluate pump flow rate reproducibility and pulsation, one method is commonly used to assess gradient formation capability. A certain amount of an analyte with adequate molar absorptivity at the wavelength employed for detection is introduced into one of the mobile phases employed to create the gradient. In the case described, 5% acetone was introduced into the mobile phase, distributed to the system by pump B. No UV-absorbing analyte was introduced into mobile phase A. The fractional flow rate of pump B relative to the total flow rate of the system (mandated by the sum of the flow rates of pumps A and B) was increased in individual steps to account for 0, 3,6,12.5,25, 50, and 100% fractional rates. The total flow for the system was maintained at 300 /jL/ min (for 24 columns), resulting in a per column flow rate of 12.5 /iL/min/column. 

Manufacturers publish their product s performance characteristics as specifications, which are often used by the customer for comparison during the selection process. Table 1 shows the specifications of an Agilent 1100 Series Quaternary Pump, which is quite representative of other high-end analytical pumps. Note pulsation is particularly detrimental to the performance of flow-sensitive detectors (e.g., mass spectrometer, refractive index detector). Differences in dwell volumes and composition accuracy between HPLC systems might cause problems during method transfers. 

The present investigation applies deterministic methods of continuous mechanics of multiphase flows to determine the mean values of parameters of the gaseous phase. It also applies stochastic methods to describe the evolution of polydispersed particles and fluctuations of parameters [4]. Thus the influence of chaotic pulsations on the rate of energy release and mean values of flow parameters can be estimated. The transport of kinetic energy of turbulent pulsations obeys the deterministic laws. 

Taylor (T4, T6), in two other articles, used the dispersed plug-flow model for turbulent flow, and Aris s treatment also included this case. Taylor and Aris both conclude that an effective axial-dispersion coefficient Dzf can again be used and that this coefficient is now a function of the well known Fanning friction factor. Tichacek et al. (T8) also considered turbulent flow, and found that Dl was quite sensitive to variations in the velocity profile. Aris further used the method for dispersion in a two-phase system with transfer between phases (All), for dispersion in flow through a tube with stagnant pockets (AlO), and for flow with a pulsating velocity (A12). Hawthorn (H7) considered the temperature effect of viscosity on dispersion coefficients he found that they can be altered by a factor of two in laminar flow, but that there is little effect for fully developed turbulent flow. Elder (E4) has considered open-channel flow and diffusion of discrete particles. Bischoff and Levenspiel (B14) extended Aris s theory to include a linear rate process, and used the results to construct comprehensive correlations of dispersion coefficients. 

The instruments for polymer HPLC except for the columns (Section 16.8.1) and for some detectors are in principle the same as for the HPLC of small molecules. Due to sensitivity of particular detectors to the pressure variations (Section 16.9.1) the pumping systems should be equipped with the efficient dampeners to suppress the rest pulsation of pressure and flow rate of mobile phase. In most methods of polymer HPLC, and especially in SEC, the retention volume of sample (fraction) is the parameter of the same importance as the sample concentration. The conventional volumeters— siphons, drop counters, heat pulse counters—do not exhibit necessary robustness and precision [270]. Therefore the timescale is utilized and the eluent flow rate has to be very constant even when rather viscous samples are introduced into column. The problems with the constant eluent flow rate may be caused by the poor resettability of some pumping systems. Therefore, it is advisable to carefully check the actual flow rate after each restarting of instrument and in the course of the long-time experiments. A continuous operation— 24h a day and 7 days a week—is advisable for the high-precision SEC measurements. THE or other eluent is continuously distilled and recycled. 

Rotary pumps deliver a nearly constant flow at a given speed, regardless of the pressure. Bypass control is the usual method, with speed control in larger sizes. Reciprocating pumps also may be controlled on bypass if a pulsation damper is provided in the circuit to smooth out pressure fluctuations Figure 3.21(c) shows this mode. 

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