The aspiration of heavy airborne particles into a point sink

1964 ◽  
Vol 279 (1378) ◽  
pp. 413-419 ◽  
Keyword(s):  
Air Flow ◽  
Numerical Results ◽  
Airborne Particles ◽  
Sampling Errors

The particles of an aerosol that is being sucked into a point sink move more slowly than the air as the orifice is approached; this is on account of their inertia. Their weight causes them to deviate from the radial streamlines of air flow at a distance from the orifice. If the circumstances are such that either of these effects operates alone, that is when either the inertia of the particles or their rate of fall due to gravity is negligible, the sample of the aerosol drawn into the orifice will have the correct concentration. Should both factors act together, however, the concentration of the sample will be low. This paper contains an analysis of the problem and a few numerical results which indicate practical steps which can be taken to avoid sampling errors.

scholarly journals Air sampling by pumping through a filter: effects of air flow rate, concentration, and decay of airborne substances

2016 ◽  
Vol 67 (4) ◽  
pp. 326-331
Author(s):  
Marko Šoštarić ◽  
Branko Petrinec ◽  
Dinko Babić
Keyword(s):  
Time Dependence ◽  
Flow Rate ◽  
Particle Concentration ◽  
Air Flow ◽  
Airborne Particles ◽  
Air Flow Rate ◽  
General Applicability ◽  
Compact Expression ◽  
Filter Effects ◽  
Over Time

Abstract This paper tackles the issue of interpreting the number of airborne particles adsorbed on a filter through which a certain volume of sampled air has been pumped. This number is equal to the product of the pumped volume and particle concentration in air, but only if the concentration is constant over time and if there is no substance decomposition on the filter during sampling. If this is not the case, one must take into account the inconstancy of the concentration and the decay law for a given substance, which is complicated even further if the flow rate through the filter is not constant. In this paper, we develop a formalism which considers all of these factors, resulting in a single, compact expression of general applicability. The use of this expression is exemplified by addressing a case of sampling airborne radioactive matter, where the decay law is already well known. This law is combined with three experimentally observed time dependence of the flow rate and two models for the time dependence of the particle concentration. We also discuss the implications of these calculations for certain other situations of interest to environmental studies.

Airborne particles, their use in the respiratory system to measure air flow, function, and clearance

1986 ◽  
Vol 10 (1) ◽  
pp. 7-25 ◽  
Author(s):  
Norton Nelson ◽  
Bernard Altshuler ◽  
Edward D. Palmes ◽  
Roy E. Albert ◽  
Morton Lippmann ◽  
...  
Keyword(s):  
Respiratory System ◽  
Air Flow ◽  
Airborne Particles ◽  
Flow Function

Virtual Height Aided Solar Chimney: A New Design

2011 ◽  
Author(s):  
Khaled I. E. Ahmed ◽  
Ali K. Abdel-Rahman ◽  
Mahmoud Ahmed ◽  
Wael M. Khairaldien
Keyword(s):  
Electric Power ◽  
Co2 Emissions ◽  
Conversion Efficiency ◽  
Numerical Study ◽  
Air Flow ◽  
Flow Speed ◽  
Numerical Results ◽  
Solar Chimney ◽  
Virtual Height ◽  
Wide Range

Renewable energy source deployment is growing rapidly as it reduces CO2 emissions and increases diversity and security of supply. Solar chimney (SC) is a promising large-scale power technology, which absorbs solar radiation and converts parts of solar energy into electric power free of CO2 emissions. A major problem of Solar Chimney Power Plant (SCPP) is its low conversion efficiency as determined by the thermal performance of the system. However, the conversion efficiency of SCPP significantly increases with the SC height increase. The current paper proposes a new design of a virtual height aided solar chimney. In this new system the solar chimney is aided with a passive cooling system at the top of the chimney and a passive solar heater at its base to virtually mimic larger heights of the chimney. The new design has been simulated numerically for development and optimization. The numerical study is done in two stages to examine this concept. In the first stage, numerical results are obtained for the effect of the chimney height on the inside air flow speed. Then, in the second stage, the effect of decreasing the temperature at the chimney exit and the effect of increasing the temperature at the chimney base on the air flow speed are examined separately for small chimney heights. Then the combined effect of the two actions is investigated at a wide range of chimney heights. The numerical results have shown that the localized base heating and exit cooling have significantly enhanced the chimney performance for chimney heights up to 500m. A chimney with height of 300m gains an increase in the air velocity more than 25% due to the heating and cooling actions. Virtual height aided Chimney with original height of 300m acts similarly to a conventional chimney with height of 500m due to the effect of base heating and exit cooling actions. This air flow velocity increase reflects 100% increase in the expected generated electric power. Further detailed results are presented and discussed.

scholarly journals Effects of cough-jet on airflow and contaminant transport in an airliner cabin section

2017 ◽  
Vol 10 (2) ◽  
pp. 72-82 ◽  
Author(s):  
Lin Yang ◽  
Xiangdong Li ◽  
Yihuan Yan ◽  
Jiyuan Tu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Contaminant Transport ◽  
Air Flow ◽  
Numerical Results ◽  
Computational Domain ◽  
Short Period ◽  
Simulation Results ◽  
Precise Representation ◽  
Cabin Environment

The goals of this study were to investigate the effect of cough-jet on local airflow and contaminant transport in a typical cabin environment by using computational fluid dynamics. A fully occupied airliner cabin section was employed as the computational domain. Contaminants were released through coughing passengers from different locations inside the cabin. Numerical results in terms of contaminant transport characteristics were examined and compared. It can be concluded that cough-jet has significant effects on air flow in front of cough passenger in a short period of time. Also, it was found that, without considering the cough-jet model, the simulation results could not be a precise representation of the transport and distribution of cough-generated airborne contaminants.

On the Variation of the Polytropic Exponent in a High Pressure Fan Impeller

2016 ◽  
Vol 841 ◽  
pp. 286-291
Author(s):  
Andrei Dragomirescu
Keyword(s):  
High Pressure ◽  
Variable Exponent ◽  
Air Flow ◽  
Numerical Results ◽  
Strong Variation ◽  
Polytropic Process ◽  
Two Stages ◽  
Spiral Casing ◽  
Polytropic Exponent

Fan impellers are usually designed considering that the pumped air is incompressible and homogeneous, i.e. its density remains constant. When the incompressibility hypothesis can lead to significant errors, as in the case of high pressure fans, the analysis of the air flow can be made by considering that the air undergoes a polytropic process of constant polytropic exponent. In this paper, the concept of polytropic process of variable exponent depending on impeller radius is introduced, in order to better approximate the phenomena that take place inside blade passages. Numerical results obtained for an impeller of a high pressure fan without spiral casing suggest that the pumped air undergoes two different processes: an expansion in the first part of the impeller and the usual compression in the second part. The two processes are reflected in the strong variation of the polytropic exponent, which shows a vertical asymptote where the change of the process takes place. The results also suggest that high pressure fan impellers could consist of two stages, each stage being designed according to the process that takes place inside it: expansion or compression.

Two-Dimensional Model of the Air Flow and Temperature Distribution in a Cavity-Type Heat Receiver of a Solar Stirling Engine

1999 ◽  
Vol 121 (4) ◽  
pp. 210-216 ◽  
Author(s):  
Kh. Kh. Makhkamov ◽  
D. B. Ingham
Keyword(s):  
Free Convection ◽  
Air Flow ◽  
Heat Losses ◽  
Stirling Engine ◽  
Numerical Results ◽  
Physical Models ◽  
Heat Receiver ◽  
Working Cycle ◽  
Side Walls ◽  
Engine Power

A theoretical study on the air flow and temperature in the heat receiver, affected by free convection, of a Stirling Engine for a Dish/Stirling Engine Power System is presented. The standard k-ε turbulence model for the fluid flow has been used and the boundary conditions employed were obtained using a second level mathematical model of the Stirling Engine working cycle. Physical models for the distribution of the solar insolation from the Concentrator on the bottom and side walls of the cavity-type heat receiver have been taken into account. The numerical results show that most of the heat losses in the receiver are due to re-radiation from the cavity and conduction through the walls of the cavity. It is in the region of the boundary of the input window of the heat receiver where there is a sensible reduction in the temperature in the shell of the heat exchangers and this is due to the free convection of the air. Further, the numerical results show that convective heat losses increase with decreasing tilt angle.

Identifying groups of airborne particles by ordination

1994 ◽  
Vol 52 ◽  
pp. 856-857
Author(s):  
M. Shlepr ◽  
C. M. Vicroy
Keyword(s):  
Elemental Analysis ◽  
Energy Dispersive Spectroscopy ◽  
Manufacturing Process ◽  
Spatial Representation ◽  
Airborne Particles ◽  
Common Source ◽  
Data Set ◽  
Microelectronics Industry ◽  
Induced Changes ◽  
Source Materials

The microelectronics industry is heavily tasked with minimizing contaminates at all steps of the manufacturing process. Particles are generated by physical and/or chemical fragmentation from a mothersource. The tools and macrovolumes of chemicals used for processing, the environment surrounding the process, and the circuits themselves are all potential particle sources. A first step in eliminating these contaminants is to identify their source. Elemental analysis of the particles often proves useful toward this goal, and energy dispersive spectroscopy (EDS) is a commonly used technique. However, the large variety of source materials and process induced changes in the particles often make it difficult to discern if the particles are from a common source.Ordination is commonly used in ecology to understand community relationships. This technique usespair-wise measures of similarity. Separation of the data set is based on discrimination functions. Theend product is a spatial representation of the data with the distance between points equaling the degree of dissimilarity.

Unidirectional Air Flow Isolators A Review

1974 ◽  
Vol 30 (1) ◽  
pp. 32-41 ◽  
Author(s):  
E. J. Butler ◽  
B. J. Egan
Keyword(s):  
Air Flow
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