Entropy Generation of Desalination Powered by Variable Temperature Waste HeatReport as inadecuate




Entropy Generation of Desalination Powered by Variable Temperature Waste Heat - Download this document for free, or read online. Document in PDF available to download.

Rohsenow Kendall Heat Transfer Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA





*

Author to whom correspondence should be addressed.



Academic Editor: Kevin H. Knuth

Abstract Powering desalination by waste heat is often proposed to mitigate energy consumption and environmental impact; however, thorough technology comparisons are lacking in the literature. This work numerically models the efficiency of six representative desalination technologies powered by waste heat at 50, 70, 90, and 120 °C, where applicable. Entropy generation and Second Law efficiency analysis are applied for the systems and their components. The technologies considered are thermal desalination by multistage flash MSF, multiple effect distillation MED, multistage vacuum membrane distillation MSVMD, humidification-dehumidification HDH, and organic Rankine cycles ORCs paired with mechanical technologies of reverse osmosis RO and mechanical vapor compression MVC. The most efficient technology was RO, followed by MED. Performances among MSF, MSVMD, and MVC were similar but the relative performance varied with waste heat temperature or system size. Entropy generation in thermal technologies increases at lower waste heat temperatures largely in the feed or brine portions of the various heat exchangers used. This occurs largely because lower temperatures reduce recovery, increasing the relative flow rates of feed and brine. However, HDH without extractions had the reverse trend, only being competitive at lower temperatures. For the mechanical technologies, the energy efficiency only varies with temperature because of the significant losses from the ORC. View Full-Text

Keywords: waste heat; entropy generation; Second Law efficiency; desalination; energy efficiency waste heat; entropy generation; Second Law efficiency; desalination; energy efficiency





Author: David M. Warsinger, Karan H. Mistry, Kishor G. Nayar, Hyung Won Chung and John H. Lienhard V *

Source: http://mdpi.com/



DOWNLOAD PDF




Related documents