Improving of ventilation efficiency at air distribution by the swirled air jets

2021 ◽  
Keyword(s):  
Attenuation Coefficient ◽  
Inclination Angle ◽  
Noise Level ◽  
Resistance Coefficient ◽  
Aerodynamic Noise ◽  
Air Distribution ◽  
Air Velocity ◽  
Air Jets ◽  
Local Resistance Coefficient ◽  
Velocity Attenuation

Abstract The article is devoted to decision of actual task of air distribution efficiency increase due to swirled air jets application. The aim of the paper is investigation of swirled air jets, analytical dependencies obtaining for determination of the air velocity attenuation coefficient, aerodynamic local resistance coefficient and noise level from the twisting plates inclination angle; optimization of the twisting plates inclination angle of the air distributor. It has been established that increase of the angle results in the air velocity attenuation coefficient increase and results in decrease of the noise level and resistance coefficient of air distributor. The optimum angle of the plates is determined considering aerodynamic, noise and energy aspects and equals 36°.

scholarly journals FEATURES OF VENTILATION SYSTEMS IN AUDITORIUM

2021 ◽  
Vol 9 (1) ◽  
pp. 11-15
Author(s):  
Dar'ya Abramkina ◽  
Gleb Petrov
Keyword(s):  
Indoor Air ◽  
Air Distribution ◽  
Thermal Mode ◽  
Air Velocity ◽  
Air Jets ◽  
Harmful Emissions ◽  
High Concentrations ◽  
Standard Calculation ◽  
Occupied Zone ◽  
Ventilation Systems

The choice of air distribution scheme is the most important task which determines indoor air quality, comfort thermal mode of the room and effectiveness of ventilation systems. The article presents comparative analysis of displacement and mixing ventilation systems for large premises. The methodology of the study is based on existing theoretical provisions and standard calculation approach of supply air jets. Multivariate calculations of mixing air distribution in cinema hall are presented. Horizontal jets along room surfaces can not provide required air velocity. In the case of vertical air distribution relative jet area beyond the recommended values. This factor had thus determined the possible formation of circulation contours with high concentrations of harmful emissions. The results of the calculation shows that the speed of the fan jet at the entrance of occupied zone lower than maximum permissible air mobility. The required temperature is achieved by using all air-distributing units considered.

Experimental Measurements Research on Internal Micro-Environment of Individually Ventilated Cage System

2013 ◽  
Vol 401-403 ◽  
pp. 1044-1047
Author(s):  
Dong Xie ◽  
Shun Quan Mo
Keyword(s):  
Laboratory Animal ◽  
Close Correlation ◽  
National Standards ◽  
Air Distribution ◽  
Experimental Measurements ◽  
Internal Environment ◽  
Air Velocity ◽  
Cage System ◽  
Environment Parameters ◽  
Edge Side

This paper firstly presents the operation principle of individually ventilated cages (IVC) system. Measurements on micro-environment of IVC system in laboratory animal room at University of South China are conducted to attain the internal environment parameters (Temperature, humidity, air velocity, air cleanliness and noise). Research results show that internal micro-environment parameters basically meet national standards about the barrier environment, but internal air distribution is uneven. In IVC system, air velocities in the edge side are higher than in the middle side, and the maximum air velocity is about 10% larger than the minimum value. Temperature in internal micro-environment depends on indoor temperatures which IVC system located in, and there has a close correlation between air velocity and temperatures. Internal environment evaluation could provide the first-hand research materials for guiding the breeding and management of laboratory animal.

Numerical Investigation of the Influence of Flow Parameters Nonuniformity at the Diffuser Inlet on Characteristics of the GTE Annular Combustion Chamber

2015 ◽  
Author(s):  
Sergey S. Matveev ◽  
Ivan A. Zubrilin ◽  
Mikhail Yu. Orlov ◽  
Sergey G. Matveev
Keyword(s):  
Combustion Chamber ◽  
Dynamic Pressure ◽  
Air Distribution ◽  
Gas Generator ◽  
Air Velocity ◽  
Degree Polynomial ◽  
Flow Dynamic ◽  
Ansys Fluent ◽  
Flow Parameters ◽  
Mode Of Operation

Parameters at a combustion chamber’s inlet significantly vary in an aircraft engine’s transient states of operation. At the same time, there is a significant spatial heterogeneity of flow parameters at a diffuser inlet of a combustion chamber, which is defined by nature of flow in a compressor and an individual for each mode of operation of a specific gas generator. In this paper presented a study of an influence of radial and circumferential nonuniformities of flow parameters on characteristics of a combustion chamber. Multi spray for annular combustion chamber with two rows of burner is considered. Z-shaped sector, which contains two nozzles of outer and two nozzles of inner row, was selected as the calculated domain. Calculations were carried out in ANSYS Fluent 14.5 software package with an implementation of cluster analysis. Nonuniformity at a diffuser inlet was set as fifth degree polynomial, which was derived from a numerical simulation of a compressor. As a result it was established, that radial nonuniformity of flow parameters at an inlet of a combustion chamber influences on characteristics of a combustion chamber. A stretched shape of velocity profile contributes to higher air flow dynamic pressure on dome than using uniform profile air velocity. At that, local equivalents ratio excess are changing, and consequently, sizes and location NOx production zones are changing as well. The residual rotation of flow from the compressor leads to a lesser effect on total pressure drop and air distribution in flame tube. The obtained results showed that, during a design of a combustion chamber, it is necessary to take into account nonuniformity of parameters’ distribution at its inlet.

Experimental Modeling of Air Temperature and Velocity Distribution in an Engine Compartment

2006 ◽  
Author(s):  
A. A. Mozafari ◽  
M. H. Saidi ◽  
J. Neyestani ◽  
A. E. Sany
Keyword(s):  
Heat Transfer ◽  
Velocity Distribution ◽  
Air Temperature ◽  
Gasoline Engine ◽  
Point Of View ◽  
Vehicle Body ◽  
Air Distribution ◽  
Wind Effect ◽  
Engine Compartment ◽  
Air Velocity

Investigation of air distribution and wind effect on a vehicle body from the point of view of underhood heat transfer effect and proper positioning of vehicle elements such cooler, condenser and engine configuration is an important area for engine researchers and manufacturers as well. In this research, the effect of air velocity distribution and wind effect around a vehicle is simulated and temperature and velocity distribution around engine block which is influenced by the wind effect is investigated. Thermal investigation of the engine compartment components is performed using results of underhood air temperature and velocity distribution. The heat transfer from engine surface is calculated from the engine energy balance in which their input data are obtained from a comprehensive experimental study on a four cylinder gasoline engine.

The Influence of the Exit Velocity Profile on the Noise of a Jet

1954 ◽  
Vol 4 (4) ◽  
pp. 341-360 ◽  
Author(s):  
Alan Powell
Keyword(s):  
Velocity Profile ◽  
Noise Level ◽  
Turbulent Pipe Flow ◽  
Aerodynamic Noise ◽  
Noise Levels ◽  
Flow Forming ◽  
Flow Velocity Profile ◽  
Jet Velocity ◽  
Initial Turbulence ◽  
Moving Fluid

SummaryThe noise levels of a jet issuing from a long pipe are compared with those of a jet having a square velocity profile at the exit. A subsonic noise reduction of between 2 and 5 decibels for various conditions is found for the case of the flow emerging with an approximately “turbulent pipe-flow” velocity profile for the same maximum jet velocity, but this is at the expense of a loss in thrust of a quarter. On comparison with a jet of smaller diameter which has an equal thrust for the same maximum jet velocity, it is found that the changes in noise level are rather smaller. For jets of equal diameters, the effects on the subsonic aerodynamic noise generated of a reduction of velocity gradient near the boundary are more than offset by the increased velocities necessary near the centre of the jet to obtain equal thrust. It is concluded that if the effect of differences in initial turbulence can be neglected the use of an auxiliary flow forming a comparatively thin sheath of slower moving fluid at the exit is not likely to result in large decreases in the subsonic noise level, and that a general reduction in jet velocity is more effective.Above the critical pressure larger reductions of up to 10 decibels are found. These are consistent with a delay of the onset of the self-maintained shock-produced noise.

scholarly journals Unsteady RANS Simulation of Air Distribution in a Ventilated Classroom with Numerous Jets

2019 ◽  
Vol 111 ◽  
pp. 02010
Author(s):  
Nikolay Ivanov ◽  
Marina Zasimova ◽  
Evgueni Smirnov ◽  
Alexey Abramov ◽  
Detelin Markov ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Flow Structure ◽  
Air Distribution ◽  
Air Velocity ◽  
3D Flow ◽  
Ansys Fluent ◽  
Test Conditions ◽  
Rectangular Form ◽  
Unsteady Rans

The study is devoted to the Unsteady Reynolds-Averaged Navies-Stokes (URANS) simulation of ventilation in an isothermal room with numerous jets supplied from ceiling diffusers. The computations of the airflow under the test conditions considered were carried out in the classroom of the Technical University of Sofia with no occupants. The room floor has a simple rectangular form, but several columns, beams, window sills, and four radiators are located inside the room that makes the geometry more complex. Air is supplied to the room through four ceiling fan coils, the Reynolds number is 2×104. Calculations were carried out using the ANSYS Fluent 18.2 software with the standard k-ε turbulence model chosen. Computational meshes of up to 33 million hexahedral cells clustered to the inlet and outlet sections were used. The main aim of the study presented is to analyze and discuss the complicated 3D flow structure in the room and to give foundation for future measurements of air velocity field in the room.

scholarly journals Operation Testing of an Advanced Personalized Ventilation System

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1596 ◽  
Author(s):  
Csáky ◽  
Kalmár ◽  
Kalmár
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Distribution System ◽  
Noise Level ◽  
Background Noise ◽  
Ventilation System ◽  
Air Distribution ◽  
Personalized Ventilation

Using personalized ventilation systems in office buildings, important energy saving might be obtained, which may improve the indoor air quality and thermal comfort sensation of occupants at the same time. In this paper, the operation testing results of an advanced personalized ventilation system are presented. Eleven different air terminal devices were analyzed. Based on the obtained air velocities and turbulence intensities, one was chosen to perform thermal comfort experiments with subjects. It was shown that, in the case of elevated indoor temperatures, the thermal comfort sensation can be improved considerably. A series of measurements were carried out in order to determine the background noise level and the noise generated by the personalized ventilation system. It was shown that further developments of the air distribution system are needed.

Experimental Study of Aerodynamic Noise From a Double Shaft Fan

2012 ◽  
Author(s):  
Jafar Madadnia ◽  
Faisal Alshehri ◽  
Kaushik Tilwa
Keyword(s):  
Residential Buildings ◽  
Noise Pollution ◽  
Aerodynamic Noise ◽  
Center Frequency ◽  
Speed Ratio ◽  
Motor Power ◽  
Noise Levels ◽  
Air Velocity ◽  
Double Row ◽  
Minimum Noise

Noise pollution from wind turbines and blowers operating in the vicinity of residential buildings has in recent years been the focus of intensive research. This paper reports on the outcome of an experimental investigation to reduce the noise pollution through design, build and testing of a counter-rotating-double-row-fan with variable spacing. A single-row fan was selected as the benchmark fan. The mechanical noise and the background ambient noise were measured using the system operating with no-blades. The aerodynamic noise from the fan was then focused and air velocity, shaft-revolution, input-electric-power to fan, amplitude (dB) and Center Frequency (CF) in Hz of noise were measured using frequency-weighting of both “A” and “Linear”. Coefficients of performance (COP), dB, CF, Tip speed ratio (TSR) were plotted for a range of spacing between two-blade-rows. It was noticed that double-shaft-fan relative to the benchmark single shaft fan has operated: a) At a lower TSR due to division of the motor power between two shafts. b) At a higher COP of up to 18% due to a higher air velocity generated at the same motor power. c) Quieter at a lower dB (of up to 10 dB). d) At the minimum noise levels (80 dB) at the spacing of 15mm-to-25mm, using the “Lin”-weighting. e) At the minimum noise levels (20 dB) at the spacing of 12mm-to 50 mm when measured at the “A”-weighting. f) With no significant change in frequency of noise when operate at the same TSR.

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