scholarly journals Derivation of flow rate and calibration method for high-volume air samplers

2019 ◽  
Vol 12 (9) ◽  
pp. 4725-4731
Author(s):  
Richard Hann ◽  
Mark Hermanson
Keyword(s):  
Flow Rate ◽  
Organic Contaminants ◽  
Scientific Literature ◽  
Air Flow ◽  
Mechanical Systems ◽  
High Volume ◽  
Calibration Method ◽  
Environmental Matrices ◽  
Flow Through ◽  
Over Time

Abstract. Sampling the atmosphere to analyze contaminants is different from other environmental matrices because measuring the volume of air collected requires a mechanical flow-through device to draw the air and measure its flow rate. The device used must have the capability of concentrating the analytes of interest onto a different substrate because the volumes of air needed are often on the order of hundreds of cubic meters. The use of high-volume air samplers has grown since 1967, when recommended limits of a large number of organic contaminants in air were developed. Equations used for calculating the air flow through the device over time have similarly been developed. However, the complete derivation of those equations has never appeared in the scientific literature. Here a thorough derivation of those equations is provided with definitions of the mechanical systems that are used in the process, along with the method of calibrating and calculating air flow.

scholarly journals Derivation of Flow Rate and Calibration Method for High-Volume Air Samplers

2018 ◽  
Author(s):  
Richard Hann ◽  
Mark Hermanson
Keyword(s):  
Flow Rate ◽  
Organic Contaminants ◽  
Scientific Literature ◽  
Air Flow ◽  
Mechanical Systems ◽  
High Volume ◽  
Calibration Method ◽  
Environmental Matrices ◽  
Flow Through ◽  
Over Time

Abstract. Sampling the atmosphere is different from other environmental matrices because measuring the volume of air sampled requires a mechanical flow-through device to draw the sample and measure its flow rate. The device used must have the capability of concentrating the analytes of interest onto a different substrate because the volumes of air needed are often in the hundreds of cubic meters. The use of high-volume air samplers has grown since 1967, when recommended limits of a larger number or organic contaminants in air were developed. The development of equations used for calculating the air flow through the device over time have similarly been developed. However, the complete derivation of those equations has never appeared in the scientific literature. Here a thorough derivation of those equations is provided with definitions of the mechanical systems that are used in the process, along with the method of calibrating and calculating air flow.

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.

scholarly journals Aeration of the premises of the dairy cows keeping in the light weight design in the warm period of the year

2020 ◽  
pp. 45-47
Author(s):  
Darya Viktorovna Abramkina
Keyword(s):  
Dairy Cows ◽  
Flow Rate ◽  
Significant Contribution ◽  
Air Flow ◽  
Warm Period ◽  
Light Weight ◽  
Exchange Flow ◽  
Weight Design ◽  
Flow Through ◽  
Air Exchange

The purpose of the article is to conduct multivariate calculations of aeration in a building at dairy cows keeping in order to identify the most effective way of ensuring normal air exchange in the stall house. According to the results of studies, it was found out that the supply air flow through the external gate makes a significant contribution to the overall air exchange of the stall house. Keywords: aeration; cowshed; ventilation; air exchange; flow rate.

scholarly journals Fluid mechanical valving of air flow in bird lungs

1988 ◽  
Vol 136 (1) ◽  
pp. 1-12 ◽  
Author(s):  
D. O. Kuethe
Keyword(s):  
High Pressure ◽  
Flow Rate ◽  
Pressure Difference ◽  
Air Flow ◽  
Low Pressure ◽  
Physical Models ◽  
Unidirectional Flow ◽  
Air Sacs ◽  
Caudal Portion ◽  
Flow Through

The unidirectional flow through the gas-exchanging bronchi of bird lungs is known to be effected by (1) the structure of the major bronchi and (2) a pressure difference between the cranial and caudal air sacs. To study the effects of bronchial structure, simple physical models of bird lungs were constructed. They suggested that, to achieve unidirectional flow, air in the caudal portion of the primary bronchus must be directed towards the orifices of the mediodorsal bronchi. To study the effect of air sac pressures, a controllable pressure difference was produced between the air sac orifices of fixed duck lungs. The cranial orifices had a higher pressure than the caudal ones during inhalation and vice versa during exhalation. There was a set of pressure differences for which the paleopulmo received the same flow rate during inhalation as during exhalation. High pressure differences caused more flow in the paleopulmo during exhalation than during inhalation; low pressure differences had the converse effect.

scholarly journals Thermal effects due to air flow and vapor transport in dry snow

1992 ◽  
Vol 38 (129) ◽  
pp. 273-281 ◽  
Author(s):  
M. R. Albert ◽  
W. R. Mcgilvary
Keyword(s):  
Heat Conduction ◽  
Temperature Gradient ◽  
Flow Rate ◽  
Thermal Effects ◽  
Air Flow ◽  
Vapor Transport ◽  
Snow Sample ◽  
Dry Air ◽  
Flow Through

AbstractThe thermal effects of air flow forced through a snow sample are investigated numerically. A new method for calculating vapor transport in snow is presented which allows for the determination of the effects of sublimation. In this method, the snow is not assumed to be saturated with water vapor. Results of the model show very good agreement with analytical and experimental results. The effects of heat conduction, heat advected by the dry air and heat associated with sublimation are examined in a comprehensive theory, and then each effect is isolated to determine its overall contribution. It is demonstrated that the heat transfer associated with vapor transport is significant in the determination of the overall temperature profile of a ventilated snow sample but that the major effects are controlled by the heat carried by the dry air flow through the snow and heat conduction due to the temperatures imposed at the boundaries. The thermal effects of ventilation of snow are more likely to be observed when there is a smaller temperature gradient over the entire snowpack and a greater flow rate of air in the snow than would be observed when there is a greater overall temperature gradient and lesser air-flow rate.

scholarly journals Effects on the Ventilation of a Two-Storey Building under Different Thermal Conditions

2019 ◽  
Vol 111 ◽  
pp. 02009
Author(s):  
Tim Röder ◽  
Paul Mathis ◽  
Dirk Müller
Keyword(s):  
Flow Rate ◽  
Static Pressure ◽  
Air Flow ◽  
Thermal Conditions ◽  
Volume Flow ◽  
Air Flow Rate ◽  
Static Pressure Difference ◽  
Flow Through ◽  
Flow Pressure ◽  
Storey Building

In this paper it is shown how the air flow rate of decentralized ventilation devices can be affected by a staircase of a two-storey building under different thermal conditions. Since these devices need local fans for supplying the requested volume flow, pressure loads have a significant impact on the delivered volume flow rates. Regarding this, the study comprises two analyses: First, a CFD-model is developed to simulate the ventilation air flow through a simplified staircase. By varying parameters for rooms’ temperature and ventilation direction, the hydrostatic pressure in the staircase is evaluated. The simulations – characterized by high Archimedes numbers – are successfully validated with findings from preliminary work. In a second part, the pressure conditions inside the staircase are referred to outside conditions. Consequently, a static pressure difference at the ventilation device on each storey can be observed. We found that the deliverable volume air flow rate can decrease up to 10 % from the nominal flow rate due to temperature differences between the storeys and outside. Therefore, heat recovery and ventilation effectiveness may also be impaired.

scholarly journals Thermal effects due to air flow and vapor transport in dry snow

1992 ◽  
Vol 38 (129) ◽  
pp. 273-281 ◽  
Author(s):  
M. R. Albert ◽  
W. R. Mcgilvary
Keyword(s):  
Heat Conduction ◽  
Temperature Gradient ◽  
Flow Rate ◽  
Thermal Effects ◽  
Air Flow ◽  
Vapor Transport ◽  
Snow Sample ◽  
Dry Air ◽  
Flow Through

AbstractThe thermal effects of air flow forced through a snow sample are investigated numerically. A new method for calculating vapor transport in snow is presented which allows for the determination of the effects of sublimation. In this method, the snow is not assumed to be saturated with water vapor. Results of the model show very good agreement with analytical and experimental results. The effects of heat conduction, heat advected by the dry air and heat associated with sublimation are examined in a comprehensive theory, and then each effect is isolated to determine its overall contribution. It is demonstrated that the heat transfer associated with vapor transport is significant in the determination of the overall temperature profile of a ventilated snow sample but that the major effects are controlled by the heat carried by the dry air flow through the snow and heat conduction due to the temperatures imposed at the boundaries. The thermal effects of ventilation of snow are more likely to be observed when there is a smaller temperature gradient over the entire snowpack and a greater flow rate of air in the snow than would be observed when there is a greater overall temperature gradient and lesser air-flow rate.

scholarly journals Analisis Sudut Lempar Gabah Pada Mesin Pembersihan Gabah Dengan Media Aliran Udara

2015 ◽  
Vol 8 (1) ◽  
pp. 29-40
Author(s):  
Suhendra Suhendra ◽  
Budi Setiawan
Keyword(s):  
Bulk Density ◽  
Flow Rate ◽  
Air Flow ◽  
Prediction Equation ◽  
Cleaning Process ◽  
Air Flow Rate ◽  
Cleaning Machine ◽  
Flow Through ◽  
Grain Bulk ◽  
The Relationship

Abstrak. Penanganan pasca panen padi merupakan salah satu upaya untuk meningkatkan produksi padi, dengan semaksimal mungkin menekan kehilangan hasil panen. Salah satu faktor yang mempengaruhi kehilangan hasil panen padi adalah proses pembersihan gabah. Berdasarkan hal tersebut, diperlukan suatu upaya untuk mendapatkan proses pembersihan gabah yang optimal dengan cara menganalisis variabel yang berpengaruh pada proses pembersihan gabah. Penelitian ini bertujuan untuk menghasilkan suatu persamaan matematika untuk memprediksi besar sudut lempar gabah, mengetahui hubungan antar variabel yang mempengaruhi proses pembersihan gabah secara mekanis serta untuk mendapatkan variabel yang diperlukan dalam rancang bangun mesin pembersih gabah dengan media pembersih berupa aliran udara. Melalui pendekatan analisis dimensi diperoleh persamaan prediksi sudut lempar gabah (θ) sebagai fungsi dari bulk density gabah (ρ), diameter saluran udara (D), laju aliran udara (V), kapasitas (Kp), diameter gabah (d), kadar air gabah (α) serta jarak saluran udara dan gabah jatuh (l) yaitu :       θ = 0,0661.(ρ.d^2.V/Kp)^0,643 . (dxα/t)^0,0618Hasil validasi persamaan prediksi sudut lempar gabah menunjukkan bahwa hasil prediksi tidak berbeda nyata dengan hasil observasi sehingga persamaan prediksi yang dibuat dapat diterima. Hasil simulasi persamaan prediksi menunjukkan bahwa diameter saluran udara dan jarak saluran udara saat gabah jatuh memiliki pengaruh tetapi tidak signifikan terhadap besarnya sudut lempar gabah, sedangkan laju aliran udara dan kapasitas memiliki pengaruh yang signifikan terhadap besarnya sudut lempar gabah. Throw Angle Analysis of Grain on Grain Cleaning Machine With Air FlowAbstract. Post-harvest handling of rice is one of the efforts to increase rice production, with maximum pressing crop yield loss. One of the factors that influence the loss of the harvest is the process of cleaning of the grain. Based on this, we need an effort to obtain optimal grain cleaning process by analyzing the variables that affect in the grain cleaning process. This research aims to produce a mathematical equation to predict the large grain throwing angle, determine the relationship between the variables that affect in the mechanical cleaning process grain and to obtain the necessary variables in the design of grain cleaning machine with cleaning media in the form of air flow. Through the dimensional analysis approach derived prediction equations throwing grain angle (θ) as a function of grain bulk density (ρ), the diameter of the airways (D), the air flow rate (V), capacity (Kp), grain diameter (d), water content grain (α) and distance airways and grain fall (l), namely:θ = 0,0661.(ρ.d^2.V/Kp)^0,643 . (dxα/t)^0,0618The result of prediction equation from grain throwing angle show that prediction result is not different significant with observation result. Simulation result of prediction equation show that the diameter  of airways and distance airways when grain fall has influence but not significant on the value of  grain throwing angle, whereas the air flow rate and capacity has significant influence on the value of  grain throwing angle.

Analytical and Numerical Modeling of Solar Chimney

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Mohammad Raghib Shakeel ◽  
Jihad Al-Sadah ◽  
Esmail M. A. Mokheimer
Keyword(s):  
Flow Rate ◽  
Volume Flow Rate ◽  
Air Flow ◽  
Incident Radiation ◽  
Analytical Models ◽  
Air Flow Rate ◽  
Solar Chimney ◽  
Trombe Wall ◽  
Flow Through ◽  
Induced Flow

Solar chimney or Trombe wall has been studied numerically and analytically. Analytical results available in the literature overestimate air flow rate by 46–97%. While insulated walls are used in the experiments, there might still be loss from the chimney walls, which is not usually considered in the available analytical models. It is found that the overestimation of air flow rate can be reduced to 3–14% by including heat losses from the glass and wall side of the chimney in the analytical model. The presently developed numerical model is validated against experimental data from literature. The conditions within which the analytical solution can give good approximate results regarding the air volume flow rate have been identified and discussed. We found that the analytical method simulates solar chimneys well for gap widths of up to 0.3 m and incident radiation above 500 W/m2. The present numerical results revealed that the optimum value of chimney gap width that maximizes the induced flow through the chimney is 0.3 m.

Sign in / Sign up

Export Citation Format

Share Document