A Reliable & Novel approach based on Thermodynamic Property estimation of Low to High Salinities Aqueous Sodium Chloride Solutions for Water-Energy Nexus (WEN) Applications

Abstract

There is a significant need for reliable and accurate thermodynamic property data of hypersaline solutions to understand the minimum heat and work of separation required and is quite useful for large scale desalination and water – energy nexus (WEN) applications. WEN related technological developments are posed to dominate the scientific pursuits in the coming decade. In this regard, an understanding on the thermo-acoustical parameters of hypersaline NaCl-water systems has been carried out in this study which may lead to a better understanding of WEN. An analysis of thermodynamic properties such as free volume, intermolecular free length, isothermal compressibility, isobaric expansibility, relaxation time, and internal pressures using ultrasonic velocity, has assisted us in understanding the various interactions occurring in hypersaline solutions (up to 100 g/kg). A new correlation for internal, osmotic and vapour pressure determination has been proposed in this work. The evaluation of relaxation time showed a minimum value around the concentration range of 25-40g/kg, which could explain the observed seawater salt concentrations at ambient temperatures. A linear variation was observed between osmotic pressure and internal pressure, which shed light on their interdependency. A detailed analysis on the energetics of hypersaline NaCl-water solutions has also been done to emphasize the fact that one must work on the extraction of osmotic power from hypersaline solutions. This work presents a comprehensive framework derived from an understanding of thermo-acoustical parameters of hypersaline solutions, their critical analysis and a look into its application in Osmotic Power Generation technologies.