Eulerian-Eulerian modelling and computational fluid dynamics simulation of wire mesh demisters in MSF plants

Eulerian–Lagrangian modeling and computational fluid dynamics simulation of wire mesh demisters in MSF plants

The present study is applied on the seawater multi-stage flash (MSF) desalination plant that is currently under operation in E-Zuetina operations plant located in Libya. The plant contains 21 evaporator stages at capacity of 10025 (ton/day). The presented operating data has been collected during a visit of the plant, a mathematical model for multistage flash (MSF) desalination plants was developed. The model was based on basic principles of physics and chemistry that describe the stages occurring in the desalination process. The input plant parameters that are known to affect the operation of the MSF desalination plant and its performance were taken into account in the construction of the model. These parameters included make-up flow, brine recycle flow, seawater flow, seawater temperature, seawater concentration, steam temperature and the plant load. For each stage, the developed model was used for predicting the temperatures and pressure of the brine, distillate, cooling brine, and the flow rates of brine outlet and distillate production. The developed model was evaluated with the MSF plant vendor simulation results and its actual operating data. The evaluation indicated that model predictions matched well with the vendor simulation results and the plant operating data. The developed model is sufficiently accurate and model predictions can be relied upon. Therefore, it may be recommended for determining optimum set point of a running MSF desalination plant at different loads to maximize the water production or minimize energy consumption. It can also be used to calculate controller set points for different loads of the plant. Keywords:E-Zuetina MSF Desalination Plant, case study, stage model, brine heater.

In this paper, a mathematical model for multistage flash (MSF) desalination plants was developed. The model was based on basic principles of physics and chemistry that describe the stages occurring in the desalination process. The input plant parameters that are known to affect the operation of the MSF desalination plant and its performance was taken into account in the construction of the model. These parameters included make-up flow, brine recycle flow, seawater flow, seawater temperature, seawater concentration, top brine temperature (TBT), steam temperature and the plant load. For each stage, the developed model was used for predicting the temperatures of the brine, distillate and cooling brine, and the flow rates of brine outlet and distillate production. The developed model was evaluated with the MSF plant vendor simulation results and its actual operating data. The evaluation indicated that model predictions matched well with the vendor simulation results and the plant operating data. The developed model is sufficiently accurate and model predictions can be relied upon. Therefore, it may be recommended for determining optimum set point of a running MSF desalination plant at different loads to maximize the water production or minimize energy consumption. It can also be used to calculate controller set points for different loads of the plant. Copyright © 2011 John Wiley & Sons, Ltd.

CFD Modelling of the Demister in the Multi Stage Flash Desalination plant

Closed greenhouses are crucial buildings for agriculture in controlled environments because they offer the best growing conditions for crops and shield them from outside influences. Researchers can now better optimize design parameters for increased crop output and energy efficiency by simulating airflow and temperature distribution inside closed greenhouses with the use of computational fluid dynamics (CFD) modeling. We examine the temperature distribution and airflow patterns inside the greenhouse under various environmental conditions using CFD simulations. Our findings show that, in comparison to traditional greenhouse constructions, the novel design greatly improves temperature uniformity and lowers energy use. Moreover, the greenhouse's thermal insulation design minimizes heat loss during the colder months, enhancing energy efficiency overall. We offer important insights into how design changes affect airflow dynamics and thermal performance in enclosed greenhouses by utilizing CFD modeling. Our research highlights how effective CFD modeling can be in maximizing crop yields and achieving sustainable agricultural practices through greenhouse design optimization. The integration of novel design components for improved energy efficiency and crop yield is a feasible outcome of this research, which advances the field of closed greenhouse technology overall. The research highlights the value of using CFD modeling to inform the design of next-generation closed greenhouse systems and has important ramifications for sustainable agriculture methods and greenhouse management techniques. The goals were to assess how well various heating/cooling systems maintained the ideal environmental conditions for plant growth. A verified CFD model was used to run the simulations, which took into account a number of variables including the shape of the greenhouse, the outside environment, and the interior heat sources. Important discoveries include understanding temperature gradients, airflow patterns, and possible areas for environmental management enhancement are presented in this paper. Results showed that the species mass transfer of vapor (H2o) will vary over time.

Simulations of pollutant dispersion within idealised urban-type geometries with CFD and integral models

The efficient use of pulverized coal is crucial to the utility industries. The use of computational fluid dynamics (CFD)-based numerical models has an important role in the design of new boiler furnaces or in retrofitting situations. The results of CFD simulations can be used to better understand the complex processes occurring within the boiler furnace. The use of these results to support boiler operation and training of operators requires that the CFD models can be easily accessed and the results are easily analysed. This paper discusses two ways to simulate the heat transfer process in boiler furnaces. The method directly applying CFD results is employed, in which the grid for solving the energy equation is the same as the flow grid in the CFD simulation while radiation heat transfer is solved in another relatively coarse grid. Comparison of the prediction results between CFD and Heat Transfer code (Simple model) is performed under boiler full load (100%) with one side wall fouling, as well as for different boiler loads (100, 98 and 95 per cent boiler full load, respectively). Finally, the flexible use of the results of CFD and the simple model for pulverized coal-fired boilers is presented. To facilitate the use of the system, a user-friendly interface was developed which enables the user to manipulate new calculations and to view results, namely performing ‘what–if’ analysis. Copyright © 2000 John Wiley & Sons, Ltd.

The efficient use of pulverized coal is crucial to the utility industries. The use of computational fluid dynamics (CFD)-based numerical models has an important role in the design of new boiler furnaces or in retrofitting situations. The results of CFD simulations can be used to better understand the complex processes occurring within the boiler furnace. The use of these results to support boiler operation and training of operators requires that the CFD models can be easily accessed and the results are easily analysed. This paper discusses two ways to simulate the heat transfer process in boiler furnaces. The method directly applying CFD results is employed, in which the grid for solving the energy equation is the same as the flow grid in the CFD simulation while radiation heat transfer is solved in another relatively coarse grid. Comparison of the prediction results between CFD and Heat Transfer code (Simple model) is performed under boiler full load (100%) with one side wall fouling, as well as for different boiler loads (100, 98 and 95 per cent boiler full load, respectively). Finally, the flexible use of the results of CFD and the simple model for pulverized coal-fired boilers is presented. To facilitate the use of the system, a user-friendly interface was developed which enables the user to manipulate new calculations and to view results, namely performing ‘what–if’ analysis. Copyright © 2000 John Wiley & Sons, Ltd.

Multi stage flash desalination plant with brine–feed mixing and cooling

A hierarchy of models exists in the literature for the simulation of pipe transients. One-dimensional (1D) water hammer models provide a cost-effective tool for the analysis of such transients. Traditional 1D models implement a quasi-steady approximation of the frictional term, which results in poor modeling of the attenuation of the transient. To improve the modeling of the attenuation phenomenon, alternative unsteady friction models were developed for the 1D water hammer formulation. Moreover, quasi-two-dimensional (quasi-2D) water hammer models were introduced, which allow the computation of the unsteady velocity profile and hence provide improved modeling of the attenuation phenomenon. Recently, interest has developed in the use of computational fluid dynamics (CFD) models based on the Navier–Stokes equations in the simulation of fluid transients. Both axisymmetric and full three-dimensional (3D) CFD models are used in this regard. The aim of the current paper is to carry out a comparative study between the performance of quasi-2D water hammer models, axisymmetric CFD models, and full 3D CFD models. Numerical computations using the three models are performed for both laminar and turbulent flow cases. Present results show that the quasi-2D water hammer model and the axisymmetric CFD model provide near identical results in terms of computing the magnitude, phase, and attenuation of the transient. Reported results also demonstrate the computational efficiency of the quasi-2D model, which provides results that agree reasonably well with the full 3D CFD model results while using a grid density, which is an order of magnitude lower than the grid requirements for the full 3D CFD model.

A compartmental model to describe hydraulics in a full-scale waste stabilization pond

Optimizing hydrocyclone design using advanced CFD model

The use of computational fluid dynamics (CFD) as an engineering tool for the design of storm water retention ponds is a rapidly growing area of interest, but there is a large gap in the literature with regard to validating the CFD models against experimental data for investigation of flow patterns and velocity distributions in storm water retention ponds. This paper assesses a CFD model against experimental flow data from a laboratory-scale physical model of an existing field retention pond. The simulated results were compared to each other and also to the experimental data to test the ability of numerical simulations for this type of problem. A representative and realistic range of flow rates from 0.16 to 1.5 L/s was tested in the physical model for comparison with the CFD model. Also, the vorticity from the physical model tests was compared to that from the numerical model to validate the CFD model. The results confirm previous findings that CFD modeling is a potential engineering tool to simulate hydraulics of storm water retention ponds and can reliably be used in pond design even at moderate computational cost. Also, it was found that CFD is relatively insensitive to the turbulence model used and grid density within a wide range of grid densities for observing general flow patterns. However, it is sensitive to the advection schemes for this particular problem. Higher order differencing schemes (high-resolution scheme) worked better than simple differencing schemes like the upwind differencing scheme (UDS). It was also found that the strength of the vorticity increases with increasing flow rate for both models, and at higher flow rates CFD is more consistent in predicting the vorticity than that of the particle tracking velocimetry (PTV) technique used in physical models.

The chemically aggressive environment generated in some parts of equipment at multi-stage flash (MSF) desalination plants can cause corrosion problems. The proper selection of materials with higher resistance to corrosion is considered as one of the most prospective approaches for smooth and efficient running of the plants. Because of this, the study of the corrosion behavior of selected materials is an important issue in the realm of desalination technology. This paper reviews the performance of materials used in different MSF desalination plants. The corrosion behavior of materials in different sections of plants, under surrounding environmental conditions, is discussed. Various types or forms of corrosion occurring in different units of plant are described and the strong role of local attack is emphasized. Case histories dealing with failure of components in different plants are cited. The criteria for the selection of materials, which depend upon the nature of environment and operating conditions, are exemplified. The merits and demerits of materials currently employed are highlighted and introduction of new materials either in existing plants as the possible replacements or in future plants are discussed.

Coupling fast fluid dynamics and multizone airflow models in Modelica Buildings library to simulate the dynamics of HVAC systems