scholarly journals Analysis of the velocity distribution in different types of ventilation system ducts

2018 ◽  
Vol 180 ◽  
pp. 02081
Author(s):  
Kazimierz Peszyński ◽  
Lukasz Olszewski ◽  
Emil Smyk ◽  
Daniel Perczyński
Keyword(s):  
Velocity Distribution ◽  
Ventilation System ◽  
Different Types

scholarly journals Analysis of the velocity distribution in different types of ventilation system ducts

2018 ◽  
Vol 180 ◽  
pp. 02081 ◽  
Author(s):  
Kazimierz Peszyński ◽  
Lukasz Olszewski ◽  
Emil Smyk ◽  
Daniel Perczyński
Keyword(s):  
Velocity Profile ◽  
Velocity Distribution ◽  
Cross Section ◽  
Power Law ◽  
Flow Rate ◽  
Fundamental Problem ◽  
Ventilation System ◽  
Different Types ◽  
Actual Profile ◽  
Ventilation Duct

The paper presents the results obtained during the preliminary studies of circular and rectangular ducts before testing the properties elements (elbows, tees, etc.)of rectangular with rounded corners ducts. The fundamental problem of the studies was to determine the flow rate in the ventilation duct. Due to the size of the channel it was decided to determine the flow rate based on the integration of flow velocity over the considered cross-section. This method requires knowledge of the velocity distribution in the cross section. Approximation of the measured actual profile by the classic and modified Prandtl power-law velocity profile was analysed.

Numerical Simulation of Impacts of Different Types of Air Duct Outlets on Ventilation Efficiency

2013 ◽  
Vol 438-439 ◽  
pp. 1098-1103
Author(s):  
Chun Zi Nan ◽  
Ji Ming Ma ◽  
Luo Zhao
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Velocity Distribution ◽  
Flow Velocity ◽  
Numerical Method ◽  
Concentration Effect ◽  
Mixing Zone ◽  
Mixing Effect ◽  
Ventilation Efficiency ◽  
Different Types

To enhance the exhaust efficiency during ventilation, three types of air duct outlets were imported. According to the characteristics of velocity distribution simulated by numerical method, the flow field is divided into the mixing zone and the exhaust zone. The gradual contracted air duct outlet can enhance the mixing effect between fresh air and smoke. In the exhaust zone, however, the flow velocity on the upper section of the tunnel is weakened, which is unfavorable for smoke exhaust. Gradual expanded air duct outlet, on the contrary, may weaken the concentration effect of the airflow. The flow velocity on the upper section of the tunnel is increased in the exhaust zone, thus the flow field is more homogenized, which is in favor of smoke exhaust.

The Use of Decentralized Ventilation Systems with Heat Recovery in the Historical Buildings of St. Petersburg

2014 ◽  
Vol 635-637 ◽  
pp. 370-376 ◽  
Author(s):  
Vera Murgul ◽  
Dusan Vuksanovic ◽  
Nikolay Vatin ◽  
Viktor Pukhkal
Keyword(s):  
Heat Recovery ◽  
Ventilation System ◽  
Energy Performance ◽  
Saint Petersburg ◽  
Exhaust Ventilation ◽  
Different Types ◽  
Energy Efficiency Standards ◽  
Energy Efficient Building ◽  
Cultural Monuments ◽  
Ventilation Systems

Historic apartment buildings in Saint-Petersburg no longer meet today’s energy efficiency standards and need upgrading to achieve lower energy-consumption. The possibilities to upgrade old buildings – historic and cultural monuments – are initially limited. A controlled heat recovery ventilation system is considered to be an integral part of energy efficient building. Provided engineering facilities of a building are updated and reequipped energy performance increases without any impact on building exteriors. Different types of decentralized intake and exhaust ventilation systems with heat recovery based on various types of heat exchangers are considered in a detailed way.

Influence of disdrometer type on rainfall kinetic energy measurement

2020 ◽  
Author(s):  
Lisbeth Lolk Johannsen ◽  
Nives Zambon ◽  
Peter Strauss ◽  
Tomas Dostal ◽  
Martin Neumann ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Velocity Distribution ◽  
Soil Loss ◽  
Drop Size ◽  
Spatial Separation ◽  
Rain Gauge ◽  
Rainfall Erosivity ◽  
Important Indicator ◽  
Erosion Risk ◽  
Different Types

<p>Rainfall kinetic energy (KE) is an important indicator for the potential soil loss due to rainfall in erosion risk assessment. Kinetic energy-intensity (I) relationships have been developed as a means to calculate the KE of rainfall, when only the rainfall intensity is known. The direct measurement of KE has been enabled due to the use of disdrometers, which measure the size and velocity of raindrops. Previous measurements have shown that rainfall measurements for the same site differed among disdrometer types. Therefore, the best fitting KE-I relationship is likely dependent on the type of disdrometer. In this study, the influence of the disdrometer-specific drop size and velocity measurements on the formulation of new KE-I relationships as well as the fit of existing equations from literature was investigated. Disdrometer rainfall data was collected in 1-minute intervals from six laser-based disdrometers. Two disdrometers of each of the following three types were compared: the PWS100 Present Weather Sensor from Campbell Scientific, the Laser Precipitation Monitor from Thies Clima and the first generation Parsivel from OTT Hydromet. The disdrometers were set up individually at sites in Austria, Czech Republic and New Zealand. Rainfall was measured between 2014 and 2019 with varying amounts of collected data for each site. The results revealed the inherent differences in drop size and velocity distribution estimation between different types of devices. The same pattern of rainfall drop size and velocity distribution could be seen for disdrometers of the same type despite spatial separation. This indicates that actual spatial differences in rainfall characteristics may be difficult to discern when comparing data from different types of disdrometers. New exponential KE-I relationships based on disdrometer data were formulated for each site and device. To confirm the use of the new KE-I equations, one of the equations was validated using rain gauge data from the same site. The best fit of literature KE-I equation varied among sites and devices. The relationship employed in the Revised Universal Soil Loss Equation (RUSLE) always underestimated KE with a percent bias ranging from -2 to -30 %. This study highlights the differences in disdrometer rainfall kinetic energy measurements and how these influence the formulation and evaluation of KE-I relationships, which are important in rainfall erosivity studies.</p>

Secondary Flow Due to the Tip Clearance at the Exit of Centrifugal Impellers

1990 ◽  
Vol 112 (1) ◽  
pp. 19-24 ◽  
Author(s):  
M. Ishida ◽  
Y. Senoo ◽  
H. Ueki
Keyword(s):  
Velocity Distribution ◽  
Secondary Flow ◽  
Shear Force ◽  
Input Power ◽  
Tip Clearance ◽  
The Other ◽  
Centrifugal Impeller ◽  
Meridional Plane ◽  
Flow Angle ◽  
Different Types

The velocity distribution was measured at the exit of two different types of un-shrouded centrifugal impeller under four different tip clearance conditions each; one with 20 radial blades and inducers and the other with 16 backward-leaning blades. The effect of tip clearance on input power was also measured. By increasing the tip clearance, the input power was hardly changed in the radial blade impeller and was reduced in the backward-leaning blade impeller. The velocity distribution normalized by the passage width between hub and shroud wall was hardly changed at the exit of the radial blade impeller by varying the tip clearance. On the other hand, the relative flow angle was reduced significantly and monotonously by an increase of tip clearance in the backward-leaning blade impeller. The change in input power due to the tip clearance was clearly related to the change of flow pattern at the exit of impeller due to the secondary flow. This is most likely caused by the component, normal to the blade, of the shear force to support the fluid in the clearance space against the pressure gradient in the meridional plane without blades.

Secondary Flow due to the Tip Clearance at the Exit of Centrifugal Impellers

1989 ◽  
Author(s):  
Masahiro Ishida ◽  
Yasutoshi Senoo ◽  
Hironobu Ueki
Keyword(s):  
Velocity Distribution ◽  
Secondary Flow ◽  
Shear Force ◽  
Input Power ◽  
Tip Clearance ◽  
The Other ◽  
Meridional Plane ◽  
Flow Angle ◽  
Different Types ◽  
Relative Flow

The velocity distribution was measured at the exit of two different types of unshrouded centrifugal impellers under four different tip clearance conditions each; one with twenty radial blades and inducers and the other with sixteen backward-leaning blades. And the effect of tip clearance on input power was also measured. By increasing the tip clearance, the input power was hardly changed in the radial blade impeller and was reduced in the backward-leaning blade impeller. The velocity distribution normalized by the passage width between hub and shroud wall was hardly changed at the exit of the radial blade impeller by varying the tip clearance, on the other hand, the relative flow angle was reduced significantly and monotonously by an increase of tip clearance in the backward-leaning blade impeller. The change in input power due to the tip clearance was clearly related to the change of flow pattern at the exit of impeller due to the secondary flow, which is most likely caused by the component, normal to the blade, of the shear force to support the fluid in the clearance space against the pressure gradient in the meridional plane without blades.

scholarly journals Building a bridge between industry and theory on the example of a new ventilation system

2019 ◽  
Vol 213 ◽  
pp. 01001 ◽  
Author(s):  
Kazimierz Peszyński
Keyword(s):  
Mathematical Modelling ◽  
Velocity Distribution ◽  
Flow Velocity ◽  
Cross Section ◽  
Flow Rate ◽  
Rectangular Cross Section ◽  
Ventilation System ◽  
Volumetric Flow Rate ◽  
Ventilation Ducts

The paper presents the possibilities of simplified determination of the air volumetric flow rate in ventilation ducts. This problem occurred during the tests of local losses in the elements of a new ventilation system based on ducts with a rounded rectangular cross-section. The presented method requires mathematical modelling of the flow velocity distribution in the ducts. The paper presents four models of the velocity distribution. The necessity of using so many models resulted from the wide coverage of the tested sections: Amax/Amin= 46.88.

Solids separation efficiency of combined sewer overflows

2005 ◽  
Vol 51 (2) ◽  
pp. 71-78 ◽  
Author(s):  
G. Luyckx ◽  
G. Vaes ◽  
J. Berlamont
Keyword(s):  
Velocity Distribution ◽  
Settling Velocity ◽  
Separation Efficiency ◽  
Efficiency Curve ◽  
Combined Sewer Overflows ◽  
Combined Sewer ◽  
Different Types ◽  
Solids Separation ◽  
Settling Velocity Distribution ◽  
The One

The removal of sewer solids at combined sewer overflow locations depends on the flow patterns inside the overflow structure on the one hand and on the sediment characteristics on the other hand. Flow conditions can be described by the residence time distribution; sewer sediments can be characterised by their settling velocity distribution. The combination of both distributions leads to a dimensionless efficiency curve, which gives the removal efficiency as a function of the Hazen number. For field conditions this efficiency curve is mainly influenced by the settling velocity distribution of the sewer sediments and, as a consequence, nearly identical efficiency curves are found for different types of prototype CSO structure. For design purposes, a methodology using return frequency analysis is proposed.

scholarly journals Hydraulic Characteristics of Emerged Rigid and Submerged Flexible Vegetations in the Riparian Zone

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1057
Author(s):  
Xin Meng ◽  
Yubao Zhou ◽  
Zhilin Sun ◽  
Kaixuan Ding ◽  
Lin Chong
Keyword(s):  
Velocity Distribution ◽  
Turbulence Intensity ◽  
Flow Resistance ◽  
Test Method ◽  
Relative Depth ◽  
Distribution Profile ◽  
Experimental Conditions ◽  
Different Types ◽  
Wooden Stick ◽  
Determining Factor

Flow resistance, velocity distribution, and turbulence intensity are significantly influenced by aquatic vegetations (AV) in riparian zones. Understanding the hydraulics of flow with planted floodplains is of great significance for determining the velocity distribution profile and supporting the fluvial processes management. However, the traditional flume experiment method is inefficient. Therefore, the multigroup simultaneous flume test method was carried out to describe the flow patterns affected by emerged rigid (reed and wooden stick) and submerged flexible vegetations (grass and chlorella). The Acoustic Doppler Velocimeter (ADV) was utilized to measure the velocity at one point for different experimental conditions. The results showed that hydraulic features were influenced by different types of vegetation. Furthermore, the relative depth (z/h) was a determining factor of those variations. In addition, the time-averaged velocity distributions of planted floodplains are not logarithmic. Instead, they represented “s-shape” profiles. In detail, for the vegetated floodplains, reed and wood followed an s-shape profile, but for grass and chlorella, they followed reverse s-shape profile. For all cases, turbulence is not isotropic and the change law of turbulence intensity is different in different sections. The flow resistance, turbulence intensities, and Reynold stresses influenced by different types of vegetation were also analyzed.

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