The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Donald E. Beasley - One of the best experts on this subject based on the ideXlab platform.
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on stairwell and elevator shaft Pressurization for smoke control in tall buildings
Building and Environment, 2009Co-Authors: Richard S. Miller, Donald E. BeasleyAbstract:Elevator shaft and stairwell shaft-Pressurization systems are studied as means of smoke migration prevention through the stack effect in tall buildings using the CONTAM simulation software. A thirty story building model is considered with exterior leakages calibrated to experimental data for both a residential and a commercial building. Stairwell Pressurization is found to be completely feasible in the absence of elevator shaft Pressurization. In contrast, coupled elevator shaft-Pressurization systems are found to produce prohibitively large pressure differences across both the elevator and stairwell doors if (1) minimum pressure differences must be maintained at both open and closed elevator doors and (2) if the system must function properly when the ground floor exterior building doors are closed. Even in these cases situations arise in which smoke may enter the shaft and be actively distributed throughout the building by the fan system. These differences between stairwell and elevator shaft Pressurization are directly attributable to the much larger leakage areas associated with elevator doors. Relatively large flow rates through the open elevator doors act to pressurize the ground floor of the building, indirectly causing large pressure differences across upper floor elevator doors. Furthermore, the results show that there is a strong coupling between the fan speed requirements of the stairwell and elevator shaft-Pressurization systems. Fan requirements are also found to be sensitive to the ambient temperature. Effects of the fan location, louvers, vents, the building height, and the number of elevator cars and/or shafts are also addressed.
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On Smoke Control by Pressurization in Stairwells and Elevator Shafts
2008Co-Authors: Richard S. Miller, Donald E. BeasleyAbstract:Elevator shaft and stairwell shaft Pressurization systems are studied as means of smoke migration prevention through the stack eect in tall buildings using the CONTAM simulation software. Stairwell Pressurization is found to be completely feasible in the absence of elevator shaft Pressurization. In contrast, coupled elevator shaft Pressurization systems are found to produce prohibitively large pressure dierences across both the elevator and stairwell doors if: (1) minimum pressure dierences must be maintained at both open and closed elevator doors, and (2) if the system must function properly when the ground floor exterior building doors are closed. Even in these cases situations arise in which smoke may enter the shaft and be actively distributed throughout the building by the fan system. Furthermore, the results show that there is a strong coupling between the fan speed requirements of the stairwell and elevator shaft Pressurization systems. Fan requirements are also found to be sensitive to the ambient temperature. Eects of the fan location, louvers, vents, the building height, and the number of elevator cars and/or shafts are also addressed.
Yanzhong Li - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic performance of pre Pressurization in a cryogenic tank
Applied Thermal Engineering, 2017Co-Authors: Yanzhong Li, Cui LiAbstract:Abstract To supply more actual initial physical field for launch of cryogenic propellant tank, it is necessary to investigate the thermodynamic performance of propellant tank before launch. As cryogenic propellant tank will experience the ground open parking and ground pre-Pressurization phase, the present study is particularly to investigate the Pressurization performance and temperature distribution in a cryogenic liquid oxygen (LOX) tank for the above parts. One CFD model is established with both the vapor-liquid interface phase change and external forced convection heat exchange considered. The results show that during the ground parking part, the intense nucleate boiling appears in cryogenic tank firstly, then the boiling intensity becomes weak, finally, it tends to be stable. With the high temperature gas oxygen (GOX) injecting into tank, tank pressure fluctuates among the setting pressure limits. The ullage is condensed during the whole pre-Pressurization part. Influenced by heat transferring from the ullage and the external heat leakage, the thermal stratified layer becomes thick with time continuing. With the environmental temperature varying from 253.0 K to 313.0 K, its effect on tank pressure and liquid temperature distribution is not so obvious in this study. The unique large change is that the ullage center line temperature increases with the rise of environmental temperature, while the other parameters have slight changes.
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Pressurization performance and temperature stratification in cryogenic final stage propellant tank
Applied Thermal Engineering, 2016Co-Authors: Yanzhong LiAbstract:Abstract One CFD model is established to investigate the Pressurization performance and thermal stratification in the final stage cryogenic liquid oxygen (LOX) tank, which is subjected to aerodynamic heat and space radiations during launch. Iterative calculation with variable physical properties in each time step, both aerodynamic heat and space radiation have been considered by compiling one UDF and implanting it into the CFD model. It turns out that aerodynamic heat has caused large influence on tank Pressurization performance, while the effect of space radiation on tank Pressurization is not obviously reflected. Influenced by the injection gas, tank pressure fluctuates between the minimum and the maximum pressure limit and the ullage mass decreases due to condensation during the active-Pressurization. Meanwhile, the basic parallel advance trend of temperature distribution is roughly formed. During the pressurized discharge, tank pressure experiences a sharp decline at first, then decreases linearly, finally reduces with a larger rate. The liquid temperature increases gradually to the direction of advance as liquid height declines. Moreover, the residual liquid temperature increases obviously. With the heat continuous transferring from the ullage to the liquid, the ullage is under condensation during the whole process.
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transient thermal and Pressurization performance of lo2 tank during helium Pressurization combined with outside aerodynamic heating
International Journal of Heat and Mass Transfer, 2013Co-Authors: Lei Wang, Yanzhong Li, Zhixiang ZhaoAbstract:Abstract A computational fluid dynamic (CFD) model, which can simultaneously account for the heat exchanges inside the tank and outside aerodynamic heating, is constructed to investigate the transient thermal and Pressurization performance of cryogenic tank during discharge. Besides the fluid and tank wall regions, the foam region is also considered as the computational domain. Reference enthalpy method is used to account for the outside aerodynamic heating effect. The predictive ability of the CFD model is evaluated on the basis of the comparisons between its results and experimental data and a good agreement is obtained. Then the model is used to predict a pressurized discharge event, and the thermal and Pressurization behaviors are obtained and analyzed. The results show that outside aerodynamic heating cannot penetrate the foam layer to facilitate the Pressurization performance. Conversely, a certain proportion of energy might be transferred from heated tank wall to foam layer, which exert a negative effect on the Pressurization behaviors. The aerodynamic heating effect may not be accounted for in the CFD simulation of a foam-insulated tank, if the thermal performance at outer surface of the tank is not particularly concerned. Generally, this paper supplies an effective way to predict Pressurization performance and expresses valid results of the thermal performance inside and outside the cryogenic tank during discharge. It is also stated that the CFD model has a better accuracy in predicting Pressurization characteristics.
J. Vladimir Oliveira - One of the best experts on this subject based on the ideXlab platform.
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Effect of supercritical carbon dioxide processing on Vibrio parahaemolyticus in nutrient broth and in oysters (Crassostrea gigas)
Journal of Food Science and Technology, 2018Co-Authors: Katherine H. O. Matos, Lindomar A. Lerin, Douglas Soares, Lenilton Santos Soares, Marieli Lima, Alcilene R. Monteiro, J. Vladimir OliveiraAbstract:This study aimed to evaluate the technical feasibility of supercritical carbon dioxide (sc-CO_2) treatment for Vibrio parahaemolyticus inactivation in oysters ( Crassostrea gigas ) and in nutrient broth. For this purpose, a variable-volume reactor was used as experimental system and a 2^3 factorial design was adopted considering the mass ratio between carbon dioxide and the product, Pressurization and dePressurization rate and Pressurization cycles. Through statistical analysis of the experimental data, the mass ratio of 1:0.8 (product:carbon dioxide), dePressurization rate of 10.0 MPa/min and one cycle of Pressurization was determined as the best process condition to eliminate V. parahaemolyticus , and this was the condition used for the inactivation kinetic analysis. Comparison between the inactivation kinetics of V. parahaemolyticus showed that the behavior of this microorganism inactivation depends on the environment in which it operates and its initial count. The results confirm that the supercritical carbon dioxide is effective in inactivating microorganisms in oysters, including pathogenic V. parahaemolyticus , demonstrating the potential of this technology in the food industry.
Richard S. Miller - One of the best experts on this subject based on the ideXlab platform.
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on stairwell and elevator shaft Pressurization for smoke control in tall buildings
Building and Environment, 2009Co-Authors: Richard S. Miller, Donald E. BeasleyAbstract:Elevator shaft and stairwell shaft-Pressurization systems are studied as means of smoke migration prevention through the stack effect in tall buildings using the CONTAM simulation software. A thirty story building model is considered with exterior leakages calibrated to experimental data for both a residential and a commercial building. Stairwell Pressurization is found to be completely feasible in the absence of elevator shaft Pressurization. In contrast, coupled elevator shaft-Pressurization systems are found to produce prohibitively large pressure differences across both the elevator and stairwell doors if (1) minimum pressure differences must be maintained at both open and closed elevator doors and (2) if the system must function properly when the ground floor exterior building doors are closed. Even in these cases situations arise in which smoke may enter the shaft and be actively distributed throughout the building by the fan system. These differences between stairwell and elevator shaft Pressurization are directly attributable to the much larger leakage areas associated with elevator doors. Relatively large flow rates through the open elevator doors act to pressurize the ground floor of the building, indirectly causing large pressure differences across upper floor elevator doors. Furthermore, the results show that there is a strong coupling between the fan speed requirements of the stairwell and elevator shaft-Pressurization systems. Fan requirements are also found to be sensitive to the ambient temperature. Effects of the fan location, louvers, vents, the building height, and the number of elevator cars and/or shafts are also addressed.
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On Smoke Control by Pressurization in Stairwells and Elevator Shafts
2008Co-Authors: Richard S. Miller, Donald E. BeasleyAbstract:Elevator shaft and stairwell shaft Pressurization systems are studied as means of smoke migration prevention through the stack eect in tall buildings using the CONTAM simulation software. Stairwell Pressurization is found to be completely feasible in the absence of elevator shaft Pressurization. In contrast, coupled elevator shaft Pressurization systems are found to produce prohibitively large pressure dierences across both the elevator and stairwell doors if: (1) minimum pressure dierences must be maintained at both open and closed elevator doors, and (2) if the system must function properly when the ground floor exterior building doors are closed. Even in these cases situations arise in which smoke may enter the shaft and be actively distributed throughout the building by the fan system. Furthermore, the results show that there is a strong coupling between the fan speed requirements of the stairwell and elevator shaft Pressurization systems. Fan requirements are also found to be sensitive to the ambient temperature. Eects of the fan location, louvers, vents, the building height, and the number of elevator cars and/or shafts are also addressed.
S V Schmitt - One of the best experts on this subject based on the ideXlab platform.
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nucleation and dynamic rupture on weakly stressed faults sustained by thermal Pressurization
Journal of Geophysical Research, 2015Co-Authors: S V Schmitt, Paul Segall, Eric M DunhamAbstract:Earthquake nucleation requires that the shear stress τ locally reaches a fault's static strength, fσeff, the product of the friction coefficient and effective normal stress. Once rupture initiates, shear heating-induced thermal Pressurization can sustain rupture at much lower τ/σeff ratios, a stress condition believed to be the case during most earthquakes. This requires that earthquakes nucleate at heterogeneities. We model nucleation and dynamic rupture on faults in a 2-D elastic medium with rate/state friction and thermal Pressurization, subjected to globally low τ but with local stress heterogeneities that permit nucleation. We examine end-member cases of either high-τ or low-σeff heterogeneities. We find that thermal Pressurization can sustain slip at τ/σeff values as low as 0.13, compared to static friction of ∼0.7. Background τ (and, to lesser extent, heterogeneity width) controls whether ruptures arrest or are sustained, with extremely low values resulting in arrest. For a small range of background τ, sustained slip is pulse-like. Cessation of slip in a pulse tail can result from either diffusive restrengthening of σeff or a wave-mediated stopping phase that follows the rupture tip. Slightly larger background τ leads to sustained crack-like rupture. Thermal Pressurization is stronger at high-τ heterogeneities, resulting in a lower background τ threshold for sustained rupture and potentially larger arresting ruptures. High-stress events also initiate with higher moment rate, although this may be difficult to observe in nature. For arresting ruptures, stress drops and the dependence of fracture energy on mean slip are both consistent with values inferred for small earthquakes.
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shear heating induced thermal Pressurization during earthquake nucleation
Journal of Geophysical Research, 2011Co-Authors: S V Schmitt, Paul Segall, T MatsuzawaAbstract:[1] We model earthquake nucleation (in 2D) on narrow faults with coupled rate-state friction and shear heating-induced thermal Pressurization, including diffusive transport of heat and pore pressure. Thermal Pressurization increases pore pressure p, decreasing frictional resistance. Observed fault core permeability is generally too low to mitigate thermal Pressurization at subseismic slip speeds. Under drained, isothermal conditions, nucleation with the aging law is crack like, with the interior of the slip zone always near maximum slip speed. When thermal Pressurization is included, it can dominate weakening at speeds of 0.02–20 mm/s for hydraulic diffusivities chyd from 10−8 to 10−3 m2/s and nominal material parameters well before seismic radiation occurs. Dramatic along-strike localization of slip occurs due to feedback in which the area of maximum slip experiences the greatest weakening, which in turn favors more slip. With the slip law, however, nucleation is pulse like, with slip speed decaying behind the pulse tip. Thermal Pressurization is diminished relative to the aging law case since most weakening occurs in locations with limited slip, yet we find that it can overwhelm frictional weakening at slip speeds in the range of 1–100 mm/s for chyd from 10−8 to 3 × 10−5 m2/s. At higher slip speeds, the finite thickness of the shear zone becomes significant, reducing thermal Pressurization. Even if not the dominant weakening mechanism, thermal Pressurization is likely to be significant at or before the onset of seismic radiation.
