Kishor G. Nayar

Surface Tension of Seawater

New measurements and a reference correlation for the surface tension of seawater at atmospheric pressure are presented in this paper. Surface tension of seawater was measured across a salinity range of 20 ⩽ S ⩽ 131 g/kg and a temperature range of 1 ⩽ t ⩽ 92 °C at atmospheric pressure using the Wilhelmy plate method. The uncertainty within measurements varied from 0.18 to 0.37 mN/m with the average uncertainty being 0.22 mN/m. The experimental procedures were validated with tests conducted on ACS reagent grade water and aqueous sodium chloride solutions. Literature data and present measurements were evaluated and a reference correlation was developed expressing surface tension of seawater as a function of temperature and salinity. The average absolute percentage deviation between measurements and the correlation was 0.19% while the maximum deviation was 0.60%.

Mechanical vapor compression—Membrane distillation hybrids for reduced specific energy consumption

AbstractThe energy efficiency of membrane distillation (MD) systems is low when compared to other thermal desalination systems. This leads to high water production costs when conventional fuels such as natural gas are used. In MD, separation of pure product water from feedwater is driven by differences in vapor pressure between the streams. Thus, the process can occur at low temperature and ambient pressure. As a result, MD is most frequently paired with waste or renewable sources of low temperature heat energy that can be economically more feasible. MD systems with internal heat regeneration have been compared to and modeled similar to counter-flow heat exchangers. In this study, MD is used to replace the preheater heat exchanger used for thermal energy recovery from the brine stream in mechanical vapor compression (MVC). Using MD in place of the heat exchanger results not only in effectively free thermal energy for MD, but also subsidized cost of capital, since the MD module is replacing expensive heat ...

Feasibility Study of an Electrodialysis System for In-Home Water Desalination and Purification in Urban India

Desalination of high salinity water is an effective way of improving the aesthetic quality of drinking water and has been demonstrated to be a characteristic valued by consumers. Across India, 60% of the groundwater, the primary water source for millions, is brackish or contains a high salt content with total dissolved solids (TDS) ranging from 500 parts per million (ppm) to 3,000ppm. The government does not provide sufficient desalination treatment before the water reaches the tap of a consumer. Therefore consumers have turned to in-home desalination. However, current products are either expensive or have low recovery, product water output per untreated feed water, (∼30%) wasting water resources. Electrodialysis (ED) is a promising technology that desalinates water while maintaining higher recovery (up to 95%) compared to existing consumer reverse osmosis (RO) products. This paper first explores the in-home desalination market to determine critical design requirements for an in-home ED system. A model was then used to evaluate and optimize the performance of an ED stack at this scale and designated salinity range. Additionally, testing was conducted in order to validate the model and demonstrate feasibility. Finally, cost estimates of the proposed in-home ED system and product design concept are presented. The results of this work identified a system design that provides consumers with up to 80% recovery of feed water with cost and size competitive to currently available in-home RO products.Copyright