Design and Calibration of Chambers for the Measurement of Housed Dairy Cow Gaseous Emissions

2017 ◽  
Vol 60 (4) ◽  
pp. 1291-1300 ◽  
Author(s):  
Jessica L. Drewry ◽  
J. Mark Powell ◽  
Christopher Y. Choi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Dairy Cows ◽  
Management Practices ◽  
Emission Rates ◽  
Gaseous Emissions ◽  
Gas Emission ◽  
Gas Emissions ◽  
Gas Leakage ◽  
Air Mixing

Abstract. The increased global demand for milk and other dairy products over the past decade has heightened concerns about the potential for increased environmental impacts. Accurate measurement of gas emissions from dairy cows is essential to assess the effects of cow diets and other management practices on both the composition and rate of gas emissions. In this article, methodologies are described to instrument, calibrate, and assess the uncertainty of gas emissions by cows housed in chambers that simulate production settings. The supply and exhaust ducts of each chamber were equipped with pitot tubes, temperature and relative humidity probes, and gas samplers to monitor airflow rates, gas composition, and gas emission rates. A Fourier transform infrared spectroscopy (FTIR) instrument was used to quantify gaseous concentrations in the gas samples on a semi-continuous basis. The measurement uncertainty of the rate of gaseous emission from the chambers was quantified, and gas concentration and differential pressure, as measured by the pitot tubes, were identified as the primary parameters contributing to gas emission uncertainties. Mass recovery tests determined that the recovery of methane from each chamber was within 10% of the released mass. Fan operating curves were experimentally determined to identify optimum differential chamber pressures to minimize gas leakage from the chambers. A computational fluid dynamics model was developed to assess air mixing patterns and define steady-state conditions. The model was validated with experimental data of air velocity within each chamber. These procedures will facilitate accurate measurement of gas emissions from housed dairy cows and provide a laboratory to test various gas mitigation treatments. Keywords: Computational fluid dynamics, Dairy, Emission chamber.

Design Approach for the Development of the Flow Field of Bipolar Plates for a PEMFC Stack Prototype

2014 ◽  
Vol 11 (6) ◽  
Author(s):  
Paolo Sala ◽  
Paola Gallo Stampino ◽  
Giovanni Dotelli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fuel Cell ◽  
Cfd Simulation ◽  
Bipolar Plates ◽  
Flow Rates ◽  
Gas Leakage ◽  
Auxiliary Power ◽  
Computational Fluid Dynamics Cfd ◽  
Enhance Mass

This work is part of a project whose final aim is the realization of an auxiliary power fuel cell generator. It was necessary to design and develop bipolar plates that would be suitable for this application. Bipolar plates have a relevant influence on the final performances of the entire device. A gas leakage or a bad management of the water produced during the reaction could be determinant during operations and would cause the failure of the stack. The development of the bipolar plates was performed in different steps. First, the necessity to make an esteem of the dynamics that happen inside the feeding channels led to perform analytical calculations. The values found were cross-checked performing a computational fluid dynamics (CFD) simulation; finally, it was defined the best pattern for the feeding channels, so that to enhance mass transport and achieve the best velocity profile. The bipolar plates designed were machined and assembled in a laboratory scale two cells prototype stack. Influences of the temperature and of the humidity were evaluated performing experiments at 60 deg and 70 deg and between 60% and 100% of humidity of the reactant gasses. The best operating point achieved in one of these conditions was improved by modifying the flow rates of the reactant, in order to obtain the highest output power, and it evaluated the reliability of the plates in experiments performed for longer times, at fixed voltages.

Review of Computational Fluid Dynamics Studies on Chemical Looping Combustion

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Yali Shao ◽  
Ramesh K. Agarwal ◽  
Xudong Wang ◽  
Baosheng Jin
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Flow Process ◽  
Gas Leakage ◽  
Fuel Reactor ◽  
Energy Penalty

Abstract Chemical looping combustion (CLC) is an attractive technology to achieve inherent CO2 separation with low energy penalty. In CLC, the conventional one-step combustion process is replaced by two successive reactions in two reactors, a fuel reactor (FR) and an air reactor (AR). In addition to experimental techniques, computational fluid dynamics (CFD) is a powerful tool to simulate the flow and reaction characteristics in a CLC system. This review attempts to analyze and summarize the CFD simulations of CLC process. Various numerical approaches for prediction of CLC flow process are first introduced and compared. The simulations of CLC are presented for different types of reactors and fuels, and some key characteristics including flow regimes, combustion process, and gas-solid distributions are described in detail. The full-loop CLC simulations are then presented to reveal the coupling mechanisms of reactors in the whole system such as the gas leakage, solid circulation, redox reactions of the oxygen carrier, fuel conversion, etc. Examples of partial-loop CLC simulation are finally introduced to give a summary of different ways to simplify a CLC system by using appropriate boundary conditions.

Measurement of gaseous emissions from denitrification of applied N-15 .I. Effect of cover duration

Soil Research ◽  
1995 ◽  
Vol 33 (1) ◽  
pp. 77 ◽  
Author(s):  
UK Avalakki ◽  
WM Strong ◽  
PG Saffigna
Keyword(s):  
Close Agreement ◽  
Soil Cover ◽  
Linear Increase ◽  
Gas Analysis ◽  
15N Balance ◽  
Gaseous Emissions ◽  
Gas Emission ◽  
Gas Emissions ◽  
Soil Saturation ◽  
Peak Emission

Measurement of gas emissions from denitrification of applied N has been restricted because of the lack of a convenient method. Recently a method using an electric are to measure 15N contents of dinitrogen (N2) and nitrous oxide (N2;O) in air has been developed. Gas emissions from denitrification of applied 15N were determined using this method for gas analysis of the 15N2 and 15N2O captured beneath an air-tight soil cover. Loss of 15N was calculated from gas emission measurements by two methods, accumulation of daily emissions and from the peak 15N emission value by assuming linear increase and decrease over the period of emissions. Losses estimated at low emissions with incomplete soil saturation were similar (1.9 - 5.6% 15N applied) for the two methods. Losses estimated at higher emissions with complete soil saturation were higher when calculated using peak emission values (14.8 - 28.5%) rather than accumulated daily emissions (9.5 - 18.7%). Losses estimated by emissions were compared with 15N loss estimated by mass balance at the completion of two successive soil saturations. As daily cover duration was shortened, gas emission estimates of loss more closely approximated total gaseous 15N as estimated from unaccounted for 15N in the15N balance. With shortest cover duration (15 min day-1) there was close agreement (94% estimated from peak emissions) with 15N loss estimated by 15N balance. A strategy for quantitatively estimating 15N loss by emission measurements is suggested.

scholarly journals Computational Fluid Dynamics of System Hydrodynamics and Erosion Behavior in Internally Circulating Fluidized Bed Reactor with Inserting Pipe

2020 ◽  
Vol 11 (11) ◽  
pp. 504-508
Author(s):  
D. Thiemsakul ◽  
◽  
R. Piemjaiswang ◽  
P. Piumsomboon ◽  
B. Chalermsinsuwan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluidized Bed ◽  
Solid Particle ◽  
Circulating Fluidized Bed ◽  
Surface Region ◽  
Fluidized Bed Reactor ◽  
Erosion Behavior ◽  
Gas Leakage ◽  
Computational Fluid Dynamics Cfd

Internally circulating fluidized bed reactor (ICFB) is the system with combining the function of reactor, cyclones and loop seal of a conventional circulating fluidized bed reactor (CFB) into a single reactor column. In this type of reactor, the reactor column is separated into two sections (riser and downer) by baffles and is linked together via connecting ports. This system is then considered as compact operation when comparing with the conventional CFB reactor. However, the simplicity of the ICFB reactor is trade-off with a gas leakage which takes place between the two sections through the connecting ports. In addition, the solid particle movement inside the system can cause the erosion on the inserting pipes which are used for heating or cooling this ICFB reactor column. In this study, the system hydrodynamics and erosion behavior inside ICFB reactor with inserting pipe were investigated by computational fluid dynamics (CFD) using two-dimensional Eulerian-Eulerian model. The adjusted Gidaspow drag model was applied to compute the interaction between the gas and solid particle phases. Then, the system hydrodynamics was obtained and the wall shear stress was calculated in the existent of the erosion at the surface region of the inserting pipes. The results from this simulation were used to design the inserting pipe arrangement inside this ICFB reactor.

Three-Dimensional CFD Analysis of Gas Mixing in Large Volumes

2001 ◽  
Author(s):  
Brian L. Smith
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Steady State ◽  
Three Dimensional ◽  
Air Injection ◽  
Cfd Analysis ◽  
Gas Mixing ◽  
Air Mixing ◽  
Computational Fluid Dynamics Cfd ◽  
Pure Steam

Abstract The paper describes three-dimensional Computational Fluid Dynamics (CFD) calculations undertaken in support of analyses of steam/air mixing which takes place in the drywell volumes of the 1/40th-scale ESBWR1 mock-up facility PANDA under conditions of symmetric steam/air injection and asymmetric outflow. Steady-state simulations for pure steam conditions illustrate how the flow streams mix to ensure balanced outflow conditions to the condensers. A transient calculation has also been performed to examine how air released from solution in the PANDA boiler would ultimately accumulate in the separate condenser units. Results provide a possible explanation for the rundown in performance of one of the condensers which was repeatedly observed in some of the PANDA tests.

scholarly journals Numerical analysis of flow characteristics in diesel injector nozzles with convergent-divergent orifices

2017 ◽  
Vol 231 (14) ◽  
pp. 1935-1944 ◽  
Author(s):  
Francisco J. Salvador ◽  
Joaquin de la Morena ◽  
Marcos Carreres ◽  
David Jaramillo
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Steady State ◽  
Flow Characteristics ◽  
Mixing Processes ◽  
Effective Velocity ◽  
Air Mixing ◽  
Cavitation Intensity ◽  
Velocity Decrease

The geometry of diesel injector nozzles is known to significantly affect the characteristic spray behavior and emissions formation. In this paper, a novel nozzle concept, consisting of orifices with a convergent–divergent shape, is investigated through Computational Fluid Dynamics techniques. Three of these nozzles, characterized by different degrees of conicity, are compared to a nozzle with cylindrical orifices, which acts as a baseline. A homogeneous equilibrium model, validated against experimental data in previous works by the authors, is used to calculate the eventual cavitation formation inside these orifices. Additionally, the characteristics of the flow at the orifice outlet are analyzed for the four aforementioned nozzles in terms of their steady-state mass flow, effective outlet velocity and area coefficient. The results show that convergent-divergent nozzles exhibit a high cavitation intensity, located in the transition between the convergent and the divergent sections. This high cavitation intensity tends to compensate for the expected velocity decrease induced by the divergent shape, producing effective velocity values similar to those achieved by the cylindrical nozzle in many of the simulated conditions. The characteristics of the flow, together with the higher spray opening angles expected due to the divergent section of the nozzle, may improve atomization and fuel-air mixing processes.

scholarly journals Improving natural ventilation in renovated free-stall barns for dairy cows: Optimized building solutions by using a validated computational fluid dynamics model

2021 ◽  
Vol 52 (1) ◽  
Author(s):  
Nicoletta Tomasello ◽  
Francesa Valenti ◽  
Giovanni Cascone ◽  
Simona M.C. Porto
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Dairy Cows ◽  
Natural Ventilation ◽  
Time Lapse ◽  
Cfd Model ◽  
North West ◽  
The North ◽  
Livestock Buildings ◽  
Wall Openings

Natural ventilation is the most used system to create suitable conditions, removing gases, introducing oxygen in livestock buildings. Its efficiency depends on several factors and above all on the number, the dimensions and the position of wall openings and internal layout of livestock buildings. The aim of this research was to develop optimized layout solutions for improving natural ventilation effectiveness in free-stall barns for dairy cows by using a CFD approach. A validated computational fluid dynamics (CFD) model was applied in a case study which is highly representative of building interventions for renovating the layout of free-stall barns for dairy cows located in an area of the Mediterranean basin. Firstly, dairy cow behaviour was analysed by visual examination of time-lapse video-recordings. Then, simulations were carried out by using the validated CFD model and changing the position of internal and external building elements (i.e., internal office and external buildings for milking) in order to find the best condition for the thermal comfort of the animals. The results showed that the best conditions were recorded for a new configuration of the building in terms of air velocity distribution within the resting area, the service alley and the feeding alley for dairy cows, and in the pens for calves. In this new layout, the office areas and the north-west wall openings were located by mirroring them along the transversal axis of the barn. Therefore, the CFD approach proposed in this study could be used during the design phase, as a decision support system aimed at improving the natural ventilation within the barn.

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