Amount Of Bypass Research Articles

An experimental study on semiconductor process chiller using the digital scroll compressor

This study is about the application of a digital scroll compressor in order to save the energy of a semiconductor process chiller. This study conducted experiments to find characteristics related to the application of a digital scroll compressor to the semiconductor process chiller. In this study, temperature rise and fall experiments designed for rapid response to temperature change and control precision experiments per temperature range depending on the load change were carried out, and then, operational characteristics of each control method were compared with those of the old model. The power consumption and time in the case of temperature rise were 8.36 kW and about 38 min., respectively. The power consumption and time in the case of temperature fall were 5.25 kW and about 27 min., respectively. With regards to control precision based on the bypass of the digital scroll compressor, as the by-pass amount increased, the power consumption of the compressor became less, but the set temperature control was between ±0.1°C and ±0.4°C. As a result of comparing the old model and new model in terms of control precision, the old model’s precision was ±1.5°C and the new model’s precision was ±0.1°C when the temperature was set at 0°C. In addition, with the set temperature of 20°C, the precision of the old model declined to ±1.0°C while the precision of the new model increased to ±0.2°C. It was found that the set temperature increases with a decrease in the power consumption. This study demonstrates that the application of a digital scroll compressor to a semiconductor process chiller is effective, not only in saving energy, but also with improving control precision.

Bypass chromatography – design and analysis of an improved strategy for operating batch chromatography processes

The possibility to improve the performance of batch chromatographic separations by using so-called bypass method is analyzed for the first time. In bypass chromatography, only a part of the feed is introduced into the column and purified to purity larger than the desired value. The resulting fractions are then blended with fresh feed to match the given purity constraints. A general approach is presented for designing bypass batch chromatography. Analytical design equations, based on equilibrium theory of chromatography, are presented for the case of binary systems with linear or competitive Langmuir adsorption isotherms under ideal conditions. The approach allows direct calculation of optimal loading and amount of bypass so that arbitrary purity requirements are satisfied without waste streams. It is shown that the bypass strategy enhances productivity of batch chromatography without an increase in the eluent consumption. In the case of a Langmuir isotherm, maximum productivity and minimum eluent consumption are always obtained when the less retained component is collected from the column at 100% purity. In contrast, the optimal purity of the second fraction from the column is typically less than 100% and depends on the purity constraint of the more retained component. In the case of linear isotherms, operation with touching bands is preferred.

An Experimental Study of Sweepout and Entrainment in the Advanced Reactor Downcomer

Sweepout from the water surface by gas (vapor or air) flow plays an important role in analyzing the mass and momentum transfer in the reactor downcomer of multidimensional geometry during a loss-of-coolant accident by decreasing the water level in the downcomer. The core water level will tend to decrease rapidly if a considerable amount of the entrained water stream and droplets pass through the break in lieu of flooding the reactor. The amount of entrained water is mostly determined by the interacting gas flow rate, the geometric condition, and the interfacial area between the gas and the water. The sweepout is observed to take place in three rather distinct regions: at the beginning of oscillation, at the full wave, and at the wave peak (droplet separation). The beginning of oscillation normally occurs as a result of the Helmholtz instability, which is defined in terms of the difference between the gas and the liquid velocities. The horizontal water surface is waved greatly before the gas flow reaches the critical point of droplet detachment. In the full-wave region, the droplets from the rough wave are swept into the gas flow and driven to the break. The water stream and droplets near the wave-peak region pass through the break at extremely high velocities.In view of these observations this paper investigates the relation between the gas flow rate and the amount of bypass as a function of time. The test facility was constructed in a 1/10 linear scaled-down model from the 1400-MW(electric) Advanced Power Reactor 1400 (APR1400), which has four direct vessel injection lines, four cold legs, and two hot legs. The air was injected through the three intact cold legs and passed through the broken cold leg. The sweepout was visualized from the acrylic test vessel. When the water level was located at the bottom of the break nozzle, the amount of bypass increased at the high Reynolds number of the gas. In the test the downcomer water level rapidly decreased for the initial minute. Then, given the Reynolds number of the gas, the sweepout hardly occurred as the water level approached the critical point 10 min into the test. So far, the experiment and the analysis for the sweepout have been limited to small annuli, flat plates, and T-junctions, which yielded the two-dimensional flow field. The current experimental results shed light on the flow mechanism and the semiempirical relations for the three-dimensional sweepout in a large-diameter annulus such as the reactor downcomer. The sweepout and entrainment are physically understood by visual inspection of flow in the downcomer. An engineering correlation is developed to predict the multidimensional sweepout and entrainment in the annular downcomer.

Investigation of Sweepout Mechanism and Critical Void Height in Annular Downcomer

The APR1400 (Advanced Power Reactor 1,400 MWe) has adopted the direct vessel injection (DVI) in lieu of the conventional cold leg injection for its emergency core cooling system (ECCS). In this reactor, sweepout from the water surface by gas (vapor or air) flow plays an important role in analyzing the mass and momentum transfer in the reactor downcomer of multidimensional geometry during a loss-of-coolant accident (LOCA) by decreasing the water level in the downcomer. The core water level will tend to decrease rapidly if a considerable amount of the entrained water stream and droplets bypasses through the break. The amount of entrained water is mostly determined by the interacting gas flow rate, the geometric condition, and the interfacial area between the gas and the water. The sweepout is observed to take place in three rather distinct steps: the beginning of undulation, the full wave and the wave peak (droplet separation). In view of these observations we investigated the relation between the gas flow rate and the amount of bypass as a function of time. The current experimental results shed light on the flow mechanism and the semi-empirical relations for the three-dimensional sweepout in a large-diameter annulus such as the reactor downcomer. A physico-numerical model is being developed to predict the multidimensional bypass flow rate resulting from the sweepout and entrainment in the downcomer.

Depositional Cycles as a Shelf-to-Basin correlation Tool, Capitan Reef Margin - Ideas from Stratigraphic Computer Modeling: ABSTRACT

Correlations from the Yates shelf through the Capitan reef margin and into the Bell Canyon of the deep Delaware Basin (Guadalupian, Permian Basin) are not known with great detail due to limited biostratigraphic control and the inability to trace beds or time lines from the cyclic shelf deposits, through the massive reef and foreslope, and into basinal siliciclastics. The presence of a strong hierarchy of depositional cycles on the shelf and in the basin suggests that cycles may be useful as a correlation tool. A Yates shelf-to-basin correlation is proposed based on matching 3rd- and 4th-order cycles recognized with a stratigraphic computer model and on cores and outcrop. We believe thick, sand-dominated cycles were deposited in the basin during long-term lowstands; whereas, thin, organic-rich lime mudstone-dominated cycles were deposited during long-term highstands. The correlation scheme hinges on equating 3rd-order condensed intervals of organic mudstone in the basin with thick carbonate {open_quote}banks{close_quote} deposited ad the lower and upper Yates boundaries. Within this tentative large-scale framework, there is a reasonably good match between 4th-order shelf and basin cycles. Some ambiguity remains, however, due to the possibility of missed cycle beats in both the shelf (thin or no cycles, erosion) and basin (nomore » or minor condensed mudstones resulting in sand on sand, erosion) during long-term lowstands. Computer modeling suggests siliciclastics bypassed the Yates shelf and were delivered to the basin as turbidites during high-frequency (5th-order) lowstands, but the amount of bypass during any lowstand was controlled by longer-term cycles. The large-scale basinal cycles are slightly more symmetrical than their shelf counterparts; typically showing a gradual increase in clean sandstone and decrease in siltstone and organic mudstone away from a condensed interval, and the converse towards the next condensed interval.« less

The significance of by-pass in mineral separators

This paper reviews the use of the concept of by-passing applied to the performance curves of the various types of separators. It is concluded that while the concept is valuable and its inclusion in models should be continued, it is unlikely that the amount of by-pass is constant, as has been assumed in the past.