Profiling and modelling of thermal changes in a large waste stabilisation pond

2005 ◽  
Vol 51 (12) ◽  
pp. 163-172 ◽  
Author(s):  
D.G. Sweeney ◽  
J.B. Nixon ◽  
N.J. Cromar ◽  
H.J. Fallowfield
Keyword(s):  
Wind Shear ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Prevailing Wind ◽  
Cfd Model ◽  
Thermal Changes ◽  
Thermal Profiling ◽  
Computational Fluid Dynamics Cfd ◽  
High Degree ◽  
The Impact

A thermal profiling study was undertaken at four depths at each of nine sites, and at the inlets and outlets of a large waste stabilisation pond (WSP). Results were collected simultaneously using a network of 42 thermistors and dataloggers. Profiles at each site were categorised as either “stratified” or “unstratified”, and persistence analysis was used to determine the frequency and persistence of stratification events at each of the nine sites. Stratification was found to persist most strongly at the site furthest upwind in the WSP, with respect to prevailing wind during the study, leading to the conclusion that stratification induced short-circuiting will be greatest in this region of the WSP. A computational fluid dynamics (CFD) model was constructed of the WSP, including an energy balance to predict the bulk stratification gradient in the pond. Environmental conditions and WSP inlet temperature during one day in June 2001 were used as boundary conditions. The pond thermal profiles measured during the profiling study, together with outlet temperature during the day, were used to validate the CFD model results. The model predicted mean pond temperature with a high degree of accuracy (r2=0.92). However it was evident that even modest winds (≥1.5 m/s) partially broke down stratification, leading to poor prediction of the gradient by the CFD model, which did not directly account for the impact of wind shear stress on mixing in the WSP.

Impact of Heat Transfer on Contaminant Dispersion in a Public Building

2006 ◽  
Author(s):  
Sue Ellen Haupt ◽  
Robert F. Kunz ◽  
L. Joel Peltier ◽  
James J. Dreyer ◽  
Howard J. Gibeling
Keyword(s):  
Thermal Effects ◽  
Building Materials ◽  
Time Of Day ◽  
Thermal Coupling ◽  
Cfd Model ◽  
Thermal Heating ◽  
Contaminant Dispersion ◽  
Cfd Models ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

Computational fluid dynamics (CFD) models are effective at predicting dispersion of contaminants in or near a building. It is well known that thermal effects impact the flow around and within structures. This study assesses the importance of time of day, building materials, sky cover, etc. on the local thermal heating of a building. All these features affect the buoyancy, and thus, the resulting flow and dispersion about and inside a building. This study examines that impact through including full thermal coupling with flow calculations for an environmentally friendly building, including thermal radiation, conduction, and convection effects with a CFD model for both the interior and exterior of a building. The emphasis here is on simulating the impact of heating on contaminant dispersion.

Impact of Fuel Flexibility Needs on a Selected GT Performance in IGCC Application

2012 ◽  
Author(s):  
Mohammad Mansouri Majoumerd ◽  
Peter Breuhaus ◽  
Jure Smrekar ◽  
Mohsen Assadi ◽  
Carmine Basilicata ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Operating Conditions ◽  
Parameter Study ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Lumped Model ◽  
Surge Margin ◽  
Fuel Flexibility ◽  
Compressor Inlet ◽  
The Impact

As part of a European Union (EU) funded H2-IGCC project, a baseline IGCC power plant was established; this was presented at the ASME Turbo Expo 2011 (GT2011-45701). The current paper focuses on a detailed investigation of the impact of using various fuels considering different operating conditions on the gas turbine performance, and the identification of technical solutions for the realization of the targeted fuel flexibility. Using a lumped model, based on real engine data, compressor and turbine maps of the targeted engine were generated and implemented into the detailed GT model made in the commercial heat and mass balance program, IPSEpro. The implementation was done in terms of look-up tables. The impact of fuel change on the gas turbine island has been investigated and reported in this paper. Calculation results show that for the given boundary conditions, the surge margin of the compressor was slightly reduced when natural gas was replaced by hydrogen-rich syngas. The use of cleaned syngas instead of hydrogen-rich syngas resulted in a considerable reduction of the surge margin and elevation of the turbine outlet temperature (TOT) at design point conditions, when keeping the turbine inlet temperature (TIT) and compressor inlet mass flow unchanged. To maintain the TOT and improve the surge margin, when operating the engine with cleaned syngas, a combination of adjustment of variable inlet guide vanes (VIGV) and reduced TIT was considered. A parameter study was carried out to provide better understanding of the current limitations of the engine and to identify possible modifications to improve fuel flexibility.

scholarly journals Partial integration of ADM1 into CFD: understanding the impact of diffusion on anaerobic digestion mixing

2020 ◽  
Vol 81 (8) ◽  
pp. 1658-1667 ◽  
Author(s):  
Yohannis Mitiku Tobo ◽  
Usman Rehman ◽  
Jan Bartacek ◽  
Ingmar Nopens
Keyword(s):  
Anaerobic Digestion ◽  
Homogeneous Distribution ◽  
Cfd Model ◽  
Homogeneity Analysis ◽  
Cfd Models ◽  
Mode Of Operation ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Proper Performance ◽  
Partial Integration

Abstract Sufficient mixing is crucial for the proper performance of anaerobic digestion (AD), creating a homogeneous distribution of soluble substrates, biomass, pH, and temperature. The opaqueness of the sludge and mode of operation make it challenging to study AD mixing experimentally. Therefore, hydrodynamics modelling employing computational fluid dynamics (CFD) is often used to investigate this mixing. However, CFD models mostly do not include biochemical reactions and, hence, ignore the effect of diffusion-induced transport on AD heterogeneity. The novelty of this work is the partial integration of Anaerobic Digestion Model no. 1 (ADM1) into the CFD model. The aim is to better understand the effect of advection–diffusion transport on the homogenization of soluble substrates and biomass. Furthermore, AD homogeneity analysis in terms of concentration distribution is proposed rather than the traditional velocity distributions. The computed results indicate that including diffusion-induced transport affects the homogeneity of AD.

scholarly journals Hydrodynamic impact and power production of tidal turbines in a storm surge barrier

2020 ◽  
Vol 3 (3) ◽  
pp. 127-136
Author(s):  
Thomas O'Mahoney ◽  
Anton De Fockert ◽  
Arnout C. Bijlsma ◽  
Pieter De Haas
Keyword(s):  
Storm Surge ◽  
Energy Production ◽  
Field Experiments ◽  
Turbine Blades ◽  
Cfd Model ◽  
Hydrodynamic Impact ◽  
Tidal Turbines ◽  
Gate Opening ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

To estimate the impact on energy production and environment of tidal turbines placed in the Eastern Scheldt Storm Surge Barrier a Computational Fluid Dynamics (CFD) study has been carried out on the additional head differences induced by the turbines. The CFD model focusses on a single gate opening of the Storm Surge Barrier and includes half of the adjoining gates on either side. In this 40 m wide Gate a 1.2 MW array existing of five Tocardo T2 tidal turbines has been installed as part of a demonstration project in 2015. Transient computations of the barrier with and without the turbine array were carried out for a range of quasi stationary tidal phases. The turbines are resolved in detail as rotating equipment: real-time rotation of the turbine blades (involving the displacement of the mesh nodes in an unsteady setting) is implemented, and torque and thrust for the prescribed speed of rotation is provided as output. The results for velocity, power and thrust are compared with field experiments to validate the model. Based on these computations an estimate of the effect of turbines on the discharge capacity of the storm surge barrier is given. This information will be used to parameterize the tidal turbines in the far-field hydrodynamic model of Eastern Scheldt estuary for the ultimate assessment of the effect of tidal turbines on energy production and on the environment.

Aspects of Cooled Gas Turbine Modelling for the Semi-Closed O2/CO2 Cycle With CO2 Capture

2003 ◽  
Author(s):  
Kristin Jordal ◽  
Olav Bolland ◽  
A˚ke Klang
Keyword(s):  
Gas Turbine ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Continuous Process ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Stage Model ◽  
Detailed Model ◽  
The Impact

In order to capture the behaviour of the oxyfuel cycle operating with high combustor-outlet temperature, the impact of blade and vane cooling on cycle performance must be included in the thermodynamic model. As a basis for a future transient model, three thermodynamic models for the cooled gas turbine are described and compared. The first model, known previously from the literature, models expansion as a continuous process with simultaneous heat and work extraction. The second model is a simple stage-by-stage model and the third is a more detailed stage-by-stage model that includes velocity triangles and enables the use of advanced loss correlations. An airbreathing aeroderivative gas turbine is modelled, and the same gas turbine operating in an oxyfuel cycle is studied. The two simple models show very similar performance trends in terms of variation of pressure ratio and turbine inlet temperature in both cases. With the more detailed model, it was found that, without any change of geometry, the turbine rotational speed increases significantly and performance drops for the maintained geometry and pressure ratio. A tentative increase of blade angles or compressor pressure ratio is found to increase turbine performance and decrease rotational speed. This indicates that a turbine will require re-design for operation in the oxyfuel cycle.

Aspects of Cooled Gas Turbine Modeling for the Semi-Closed O2/CO2 Cycle With CO2 Capture

2004 ◽  
Vol 126 (3) ◽  
pp. 507-515 ◽  
Author(s):  
Kristin Jordal ◽  
Olav Bollard ◽  
Ake Klang
Keyword(s):  
Gas Turbine ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Continuous Process ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Stage Model ◽  
Detailed Model ◽  
The Impact

In order to capture the behavior of the oxyfuel cycle operating with high combustor-outlet temperature, the impact of blade and vane cooling on cycle performance must be included in the thermodynamic model. As a basis for a future transient model, three thermodynamic models for the cooled gas turbine are described and compared. The first model, known previously from the literature, models expansion as a continuous process with simultaneous heat and work extraction. The second model is a simple stage-by-stage model and the third is a more detailed stage-by-stage model that includes velocity triangles and enables the use of advanced loss correlations. An airbreathing aeroderivative gas turbine is modeled, and the same gas turbine operating in an oxyfuel cycle is studied. The two simple models show very similar performance trends in terms of variation of pressure ratio and turbine inlet temperature in both cases. With the more detailed model, it was found that, without any change of geometry, the turbine rotational speed increases significantly and performance drops for the maintained geometry and pressure ratio. A tentative increase of blade angles or compressor pressure ratio is found to increase turbine performance and decrease rotational speed. This indicates that a turbine will require redesign for operation in the oxyfuel cycle.

Impact of Tile Design on the Thermal Performance of Open and Enclosed Aisles

2018 ◽  
Vol 140 (1) ◽  
Author(s):  
Sadegh Khalili ◽  
Mohammad I. Tradat ◽  
Kourosh Nemati ◽  
Mark Seymour ◽  
Bahgat Sammakia
Keyword(s):  
Thermal Performance ◽  
Inlet Temperature ◽  
Open Area ◽  
Cfd Simulations ◽  
Physical Separation ◽  
Hot Air ◽  
Airflow Distribution ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Lower Noise

In raised floor data centers, tiles with high open area ratio or complex understructure are used to fulfill the demand of today's high-density computing. Using more open tiles reduces the pressure drop across the raised floor with the potential advantages of increased airflow and lower noise. However, it introduces the disadvantage of increased nonuniformity of airflow distribution. In addition, there are various tile designs available on the market with different opening shapes or understructures. Furthermore, a physical separation of cold and hot aisles (containment) has been introduced to minimize the mixing of cold and hot air. In this study, three types of floor tiles with different open area, opening geometry, and understructure are considered. Experimentally validated detail models of tiles were implemented in computational fluid dynamics (CFD) simulations to address the impact of tile design on the cooling of information technology (IT) equipment in both open and enclosed aisle configurations. Also, impacts of under-cabinet leakage on the IT equipment inlet temperature in the provisioned and under-provisioned scenarios are studied. In addition, a predictive equation for the critical under-provisioning point that can lead to a no-flow condition in IT equipment with weaker airflow systems is presented. Finally, the impact of tile design on thermal performance in a partially enclosed aisle with entrance doors is studied and discussed.

The Effect of Unequal Admission on the Performance and Loss Generation in a Double-Entry Turbocharger Turbine

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Colin D. Copeland ◽  
Peter J. Newton ◽  
Ricardo Martinez-Botas ◽  
Martin Seiler
Keyword(s):  
Cfd Model ◽  
Significant Drop ◽  
Turbine Wheel ◽  
Aerodynamic Loss ◽  
Reduced Frequency ◽  
Wide Range ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd ◽  
Double Entry ◽  
High Degree

The current work investigates a circumferentially divided turbine volute designed such that each gas inlet feeds a separate section of the turbine wheel. Although there is a small connecting interspace formed between the nozzle and the mixed-flow rotor inlet, this design does well to preserve the exhaust gas energy in a pulsed-charged application by largely isolating the two streams entering the turbine. However, this type of volute design produces some interesting flow features as a result of unequal flows driving the turbine wheel. To investigate the influence of unequal flows, experimental data from the turbocharger facility at Imperial College have been gathered over a wide range of steady-state, unequal admission conditions. These test results show a significant drop in turbine performance with increasing pressure difference between inlets. In addition, the swallowing capacities of each gas inlet are interdependent, thus indicating some flow interaction between entries. To understand the flow physics driving the observed performance, a full 3D computational fluid dynamics (CFD) model of the turbine was created. Results show a highly disturbed flow field as a consequence of the nonuniform admission. From these results, it is possible to identify the regions of aerodynamic loss responsible for the measured performance decrease. Given the unequal flows present in a double-entry design, each rotor passage sees an abrupt change in flow conditions as it rotates spanning the two feeding sectors. This operation introduces a high degree of unsteady flow into the rotor passage even when it operates in steady conditions. The amplitude and frequency of this unsteadiness will depend both on the level of unequal admission and the speed of rotor rotation. The reduced frequency associated with this disturbance supports the evidence that the flow in the rotor passage is unsteady. Furthermore, the CFD model indicates that the blade passage flow is unable to fully develop in the time available to travel between the two different sectors (entries).

Prospects for the use of the “model budget” in the distribution of equalization grants in Russia

2019 ◽  
pp. 21-38
Author(s):  
Alexander N. Deryugin ◽  
Ilya A. Sokolov
Keyword(s):  
Intergovernmental Relations ◽  
Unfunded Mandates ◽  
Interregional Inequality ◽  
Alternative Approach ◽  
The Russian Federation ◽  
Regional Authorities ◽  
High Degree ◽  
Equalization Grants ◽  
The Impact ◽  
Budget Expenditure

The paper analyzes the impact of the “model budget” on the problems of intergovernmental relations in the Russian Federation: a high proportion of expenditure obligations of regional and local budgets and a high degree of interregional inequality in fiscal capacity and socio-economic development. It was concluded that the planned broader use of the “model budget” will not solve the problem of unfunded mandates and will lead first to a significant reduction in incentives for regional authorities to develop the territorial revenue base, and then to economic slowdown in the country. As an alternative approach to improving intergovernmental relations, options are being considered for adjusting the parameters of the equalization transfers distribution formula, the procedure for determining their total volume and calculating the budget expenditure index. In solving the problem of unfunded mandates, an equally important role is given to the procedure for preparing a financial and economic rationale for draft laws.

Агрономическая эффективность промышленной (голландской) технологии возделывания картофеля

2018 ◽  
Author(s):  
C. Coy ◽  
A.V. Shuravilin ◽  
O.A. Zakharova
Keyword(s):  
Heavy Metals ◽  
Regression Analysis ◽  
Positive Response ◽  
Growth Yield ◽  
Correlation And Regression Analysis ◽  
Yield And Quality ◽  
Quality Of Products ◽  
High Degree ◽  
The Impact

Приведены результаты исследований по изучению влияния промышленной технологии возделывания картофеля на развитие, урожайность и качество продукции. Выявлена положительная реакция растений на подкормку K2SO4 в период посадки. Корреляционно-регрессионный анализ урожайности и качества клубней выявил высокую степень достоверности результатов опыта. Содержание нитратов и тяжелых металлов в клубнях было ниже допустимых величин.The results of studies on the impact of industrial technology of potato cultivation on growth, yield and quality of products. There was a positive response of plants to fertilizer K2SO4 in the period of planting. Correlation and regression analysis of yield and quality of tubers revealed a high degree of reliability of the results of experience. The contents of nitrates and heavy metals in tubers was below the permissible values.

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