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Near-field evolution and mixing of a negatively buoyant jet consisting of brine from a desalination plant

Sánchez, David (2009) In TVVR09/5011 VVR820 20091
Division of Water Resources Engineering
Abstract
The aim of this study was to investigate the behavior of a dense jet discharged into lighter ambient water. This situation can be found for brine water discharged from desalination plants. Desalination plants discharge heavier brine water, generated in the process of manufacturing fresh water, to the receiving water, usually the sea. Future extended use of desalination technologies implies larger quantities of saline water discharge to the environment. For that reason, it is of importance to study the mixing processes to avoid large concentration of salt, which may produce environmental problems. The most efficient method to increase the dilution rate of the discharged water into the sea is by using a negatively buoyant jet. The design of... (More)
The aim of this study was to investigate the behavior of a dense jet discharged into lighter ambient water. This situation can be found for brine water discharged from desalination plants. Desalination plants discharge heavier brine water, generated in the process of manufacturing fresh water, to the receiving water, usually the sea. Future extended use of desalination technologies implies larger quantities of saline water discharge to the environment. For that reason, it is of importance to study the mixing processes to avoid large concentration of salt, which may produce environmental problems. The most efficient method to increase the dilution rate of the discharged water into the sea is by using a negatively buoyant jet. The design of this type of jet involves a wide range of variables. In this study a mathematical model was developed to simulate the jet behavior in order to determine the optimum discharge conditions for different scenarios. The governing equations for a buoyant jet were employed in the model, including mass conservation for water and salt, and two momentum equations. In addition, several assumptions were introduced to simplify the model, for example, self similarity for the velocity and concentration profiles. The mathematical model was compared with data from previous experimental studies as well as from a new experiment performed within the present study. In the model simulations performed in this study to reproduce the experimental runs it was difficult to observe a close relationship between the model and the experimental data for all experimental runs. For certain parameter ranges (i.e., salinity, nozzle angle, nozzle diameter), model predictions were satisfactory. However, looking at different ranges in the densimetric Froude number there were always some runs that displayed larger discrepancies between the model simulations and the data obtained in the experiment. A main conclusion of this study is that one or several of the assumptions used to derive the mathematical model is not satisfied in the experiment and some modifications of the equations derived are needed. Most likely a modified description of the entrainment coefficient is required that introduces a dependence on salinity and other parameters. (Less)
Please use this url to cite or link to this publication:
author
Sánchez, David
supervisor
organization
course
VVR820 20091
year
type
H2 - Master's Degree (Two Years)
subject
keywords
desalination plants, avsaltningsanläggning, vattenrening, salinitet, saline water, discharged water
publication/series
TVVR09/5011
report number
09/5011
ISSN
1101-9824
language
English
id
1528823
date added to LUP
2010-01-15 12:39:02
date last changed
2019-03-27 10:47:12
@misc{1528823,
  abstract     = {The aim of this study was to investigate the behavior of a dense jet discharged into lighter ambient water. This situation can be found for brine water discharged from desalination plants. Desalination plants discharge heavier brine water, generated in the process of manufacturing fresh water, to the receiving water, usually the sea. Future extended use of desalination technologies implies larger quantities of saline water discharge to the environment. For that reason, it is of importance to study the mixing processes to avoid large concentration of salt, which may produce environmental problems. The most efficient method to increase the dilution rate of the discharged water into the sea is by using a negatively buoyant jet. The design of this type of jet involves a wide range of variables. In this study a mathematical model was developed to simulate the jet behavior in order to determine the optimum discharge conditions for different scenarios. The governing equations for a buoyant jet were employed in the model, including mass conservation for water and salt, and two momentum equations. In addition, several assumptions were introduced to simplify the model, for example, self similarity for the velocity and concentration profiles. The mathematical model was compared with data from previous experimental studies as well as from a new experiment performed within the present study. In the model simulations performed in this study to reproduce the experimental runs it was difficult to observe a close relationship between the model and the experimental data for all experimental runs. For certain parameter ranges (i.e., salinity, nozzle angle, nozzle diameter), model predictions were satisfactory. However, looking at different ranges in the densimetric Froude number there were always some runs that displayed larger discrepancies between the model simulations and the data obtained in the experiment. A main conclusion of this study is that one or several of the assumptions used to derive the mathematical model is not satisfied in the experiment and some modifications of the equations derived are needed. Most likely a modified description of the entrainment coefficient is required that introduces a dependence on salinity and other parameters.},
  author       = {Sánchez, David},
  issn         = {1101-9824},
  keyword      = {desalination plants,avsaltningsanläggning,vattenrening,salinitet,saline water,discharged water},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVVR09/5011},
  title        = {Near-field evolution and mixing of a negatively buoyant jet consisting of brine from a desalination plant},
  year         = {2009},
}