Objective investigation of discomfort due to draught in a tangential air distribution system: Influence of air diffuser’s offset ratio

2017 ◽  
Vol 27 (8) ◽  
pp. 1105-1118 ◽  
Author(s):  
Balázs Both ◽  
Zoltán Szánthó
Keyword(s):  
Turbulence Intensity ◽  
Distribution System ◽  
Statistical Tests ◽  
International Standards ◽  
Air Distribution ◽  
Air Velocity ◽  
Average Value ◽  
Velocity Magnitude ◽  
Knee Height ◽  
Head Height

The purpose of this paper is to investigate the influence of air diffuser’s offset ratio on air velocity and turbulence intensity distribution. Air velocity, turbulence intensity and air temperature measurements were performed in a single office full-scale room in isothermal case. Then the draught rate numbers were calculated to evaluate the discomfort due to draught using Fanger’s model. Different statistical tests were applied to evaluate the measured data. Results showed that the average of air velocity magnitude, turbulence intensity and draught rate was independent of the inlet offset ratio at ankle height. At the knee height and head height of seated and standing person, there was a polynomial connection between the average values and the inlet offset ratio. International standards recommend an average turbulence intensity of 40% to calculate draught rate. The results showed that 70%–80% of measured turbulence intensities were less than the standard value in the investigated range of inlet offset ratio. The draught at ankle height was within category C, while at knee height and head height of seated and standing person, the averaged draught rate numbers meet the category A and B and recommendation of CR 1752. Our results could help designers to calculate the average value of air velocity and turbulence intensity for room air distribution and indoor air comfort design.

CFD-Based Parametric Analysis on the Performance of Personalized Partition Air Distribution Systems

Solar Energy ◽  
2006 ◽  
Author(s):  
Kybum Jeong ◽  
Moncef Krarti ◽  
Zhiqiang Zhai
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Distribution System ◽  
Distribution Systems ◽  
Comfort Level ◽  
Cfd Modeling ◽  
Air Distribution ◽  
Air Velocity ◽  
Comfort Index ◽  
System Mode

The partition air distribution systems evaluated in this study allow occupants to control the system mode (on/off) and the supply air velocity and direction with similar flexibility as occupants in automobiles. To find optimal specifications for the partition air distribution systems that are able to achieve comfortable micro-environment, a CFD modeling tool was used to simulate the airflow and thermal performance of the partition air distribution systems in a typical office space. By analyzing the distribution characteristics of indoor air temperature, air velocity and thermal comfort index, the study assessed the performance of the partition air distribution systems with different operating parameters. The simulation results were analyzed and evaluated to assess both occupant’s thermal comfort and system energy consumption. The study shows that space cooling energy can be reduced while maintaining acceptable indoor thermal comfort level using a partition air distribution system with a higher supply air temperature.

Air-fluctuation nozzle and its periodic, wave-like air distribution evaluation

2019 ◽  
Vol 29 (2) ◽  
pp. 196-207
Author(s):  
Yicun Hou ◽  
Angui Li ◽  
Ying Zhang
Keyword(s):  
Power Spectrum ◽  
Turbulence Intensity ◽  
Periodic Wave ◽  
Power Spectrum Density ◽  
Air Distribution ◽  
Air Velocity ◽  
Air Supply ◽  
Spectrum Density ◽  
Velocity Decay ◽  
Natural Wind

In order to investigate dynamic characteristics of fluctuating air, one kind of nozzles of producing periodical fluctuating air is presented in this paper. Assume that the jet is isothermal and free, the typical parameters of the airflow characteristics, such as the maximum jet velocity decay, the non-dimensional velocity profile on different sections and the turbulence intensity have been discussed. In addition, power spectrum density of experimental data was calculated and analysed. The result shows that compared with stable air supply, the fluctuating air velocity decay is slower, thus forming a more uniform velocity field. Furthermore, turbulence intensity of the fluctuating air is larger. The power spectrum density exponent value approaches to the value of typical natural wind when the air velocity decreases to 0.6 m/s. With airflow diffusion, the fluctuation characteristic of airflow changes to that of natural wind gradually.

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.

scholarly journals A CFD analysis of room aspect ratio on the effect of buoyancy and room air flow

2007 ◽  
Vol 11 (4) ◽  
pp. 79-94 ◽  
Author(s):  
Brajesh Tripathi ◽  
Moulic Sandipan ◽  
Late Arora
Keyword(s):  
Temperature Distribution ◽  
Distribution System ◽  
Air Distribution ◽  
Cooling Load ◽  
Cfd Analysis ◽  
Uniform Temperature ◽  
Air Volume ◽  
Recent Developments ◽  
Careful Design ◽  
Occupied Zone

Comfort conditions in air-conditioned rooms require that temperature in the occupied zone should not vary by more than 1?C and velocity, every where in the room, should be less than 0.15 m/s so that occupants do not feel draft. Recent developments in providing effective insulation and making leak tight buildings are considerably reduced the cooling load requirements and the supply airflow rates. Obtaining uniform temperature distribution with reduced air volume flow rates requires careful design of air distribution system. This study aims to find velocity and temperature distribution in the room towards this end.

scholarly journals Numerical Study on Coupled Operation of Stratified Air Distribution System and Natural Ventilation under Multi-Variable Factors in Large Space Buildings

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8130
Author(s):  
Ziwen Dong ◽  
Liting Zhang ◽  
Yongwen Yang ◽  
Qifen Li ◽  
Hao Huang
Keyword(s):  
Thermal Comfort ◽  
Working Conditions ◽  
Distribution System ◽  
Distribution Systems ◽  
Natural Ventilation ◽  
Numerical Study ◽  
Air Distribution ◽  
Large Space ◽  
Air Conditioners ◽  
Air Supply

Stratified air distribution systems are commonly used in large space buildings. The research on the airflow organization of stratified air conditioners is deficient in terms of the analysis of multivariable factors. Moreover, studies on the coupled operation of stratified air conditioners and natural ventilation are few. In this paper, taking a Shanghai Airport Terminal departure hall for the study, air distribution and thermal comfort of the cross-section at a height of 1.6 m are simulated and compared under different working conditions, and the effect of natural ventilation coupling operation is studied. The results show that the air distribution is the most uniform and the thermal comfort is the best (predicted mean vote is 0.428, predicted percentage of dissatisfaction is 15.2%) when the working conditions are 5.9% air supply speed, 11 °C cooling temperature difference and 0° air supply angle. With the coupled operation of natural ventilation, the thermal comfort can be improved from Grade II to Grade I.

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