Entropy Generation Analysis of Desalination Technologies

Increasing global demand for fresh water is driving the development and implementation of a wide variety of seawater desalination technologies. Entropy generation analysis, and specifically, Second Law efficiency, is an important tool for illustrating the influence of irreversibilities within a system on the required energy input. When defining Second Law efficiency, the useful exergy output of the system must be properly defined. For desalination systems, this is the minimum least work of separation required to extract a unit of water from a feed stream of a given salinity. In order to evaluate the Second Law efficiency, entropy generation mechanisms present in a wide range of desalination processes are analyzed. In particular, entropy generated in the run down to equilibrium of discharge streams must be considered. Physical models are applied to estimate the magnitude of entropy generation by component and individual processes. These formulations are applied to calculate the total entropy generation in several desalination systems including multiple effect distillation, multistage flash, membrane distillation, mechanical vapor compression, reverse osmosis, and humidification-dehumidification. Within each technology, the relative importance of each source of entropy generation is discussed in order to determine which should be the target of entropy generation minimization. As given here, the correct application of Second Law efficiency shows which systems operate closest to the reversible limit and helps to indicate which systems have the greatest potential for improvement.

[1]  S. E. Aly.  Gas turbine total energy vapour compression desalination system , 1999 .

[2]  W. Wagner,et al.  The IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use , 2002 .

[3]  Nafiz Kahraman,et al.  Exergy analysis of a MSF distillation plant , 2005 .

[4]  Yunus Cerci,et al.  Exergy analysis of a reverse osmosis desalination plant in California , 2002 .

[5]  Hassan E.S. Fath,et al.  Thermoeconomic design of a multi-effect evaporation mechanical vapor compression (MEE–MVC) desalination process , 2008 .

[6]  S. Kanae,et al.  Global Hydrological Cycles and World Water Resources , 2006, Science.

[7]  Jack Gilron,et al.  Direct Contact Membrane Distillation-Based Desalination: Novel Membranes, Devices, Larger-Scale Studies, and a Model , 2007 .

[8]  Adrian Bejan,et al.  General criterion for rating heat-exchanger performance , 1978 .

[9]  H. Kretzschmar,et al.  The IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam , 2000 .

[10]  K. S. Spiegler,et al.  Principles of desalination , 1966 .

[11]  Karan H. Mistry,et al.  Optimal operating conditions and configurations for humidification–dehumidification desalination cycles , 2011 .

[12]  Karan H. Mistry.  Second law analysis and optimization of humidification-dehumidification desalination cycles , 2010 .

[13]  Linh T. T. Vu,et al.  Modelling the simultaneous heat and mass transfer of direct contact membrane distillation in hollow fibre modules , 2010 .

[14]  John H. Lienhard,et al.  The potential of solar-driven humidification–dehumidification desalination for small-scale decentralized water production , 2009 .

[15]  L. Martinez-diez,et al.  Desalination of brines by membrane distillation , 2001 .

[16]  Y. El-Sayed,et al.  The energetics of desalination processes , 2001 .

[17]  M. Elimelech,et al.  The Future of Seawater Desalination: Energy, Technology, and the Environment , 2011, Science.

[18]  Petra Döll,et al.  Taking into account environmental water requirements in global-scale water resources assessments. , 2004 .

[19]  Raphael Semiat,et al.  Energy issues in desalination processes. , 2008, Environmental science & technology.

[20]  E. Drioli,et al.  MEMBRANE DISTILLATION , 2012 .

[21]  John H. Lienhard,et al.  ENERGY EFFECTIVENESS OF SIMULTANEOUS HEAT AND MASS EXCHANGE DEVICES , 2010 .

[22]  John H. Lienhard,et al.  Thermodynamic analysis of humidification dehumidification desalination cycles , 2009 .

[23]  J. M. Rodŕıguez-Marotoa,et al.  Bulk and measured temperatures in direct contact membrane distillation , 2005 .

[24]  J. Lienhard,et al.  Erratum to Thermophysical properties of seawater: A review of existing correlations and data , 2010 .

[25]  John H. Lienhard,et al.  On exergy calculations of seawater with applications in desalination systems , 2010 .

[26]  John H. Lienhard,et al.  Optimization of multi-pressure himidification-dehumidification desalination using thermal vapor compression and hybridization , 2011 .

[27]  H. Ettouney,et al.  Fundamentals of Salt Water Desalination , 2002 .

[28]  John H. Lienhard,et al.  Effect of entropy generation on the performance of humidification-dehumidification desalination cycles , 2010 .

[29]  Jack Gilron,et al.  Desalination with a Cascade of Cross-Flow Hollow Fiber Membrane Distillation Devices Integrated with a Heat Exchanger , 2011 .

[30]  JoséM. Veza,et al.  Mechanical vapour compression desalination plants : a case study , 1995 .

[31]  Hassan E.S. Fath,et al.  PV and thermally driven small-scale, stand-alone solar desalination systems with very low maintenance needs , 2008 .

[32]  F. N. Alasfour,et al.  Thermal analysis of ME—TVC+MEE desalination systems , 2005 .

[33]  Fawzi Banat,et al.  Desalination by a “compact SMADES” autonomous solarpowered membrane distillation unit , 2007 .

[34]  Alfred Leipertz,et al.  Economical aspects of the improvement of a mechanical vapour compression desalination plant by dropwise condensation , 2010 .

[35]  E. Glueckauf,et al.  Principles of Desalination , 1966 .

[36]  John H. Lienhard,et al.  Second law analysis of reverse osmosis desalination plants: An alternative design using pressure retarded osmosis , 2011 .

[37]  R. Hyland,et al.  Formulations for the thermodynamic properties of dry air from 173.15 K to 473.15 K, and of saturated moist air from 173.15 K to 372.15 K, at pressures to 5 MPa , 1983 .

[38]  J. Georgiadis,et al.  Science and technology for water purification in the coming decades , 2008, Nature.

[39]  J. Lienhard.  A heat transfer textbook , 1981 .

[40]  M. Darwish,et al.  Multi-effect boiling systems from an energy viewpoint , 2006 .

[41]  Mark T. Holtzapple,et al.  An investigation of high operating temperatures in mechanical vapor-compression desalination. , 2008 .