A theoretical and experimental study of seawater desalination using dewvaporation

Seawater desalination was demonstrated using the Dewvaporation technique with an energy reuse factor of 7 and a production flux of 0.05 lb/hrft 2. Plastic materials were used in the construction of the Dewvaporation towers to avoid any corrosion or scaling problems that are associated with conventional desalination technologies. Scaling was not observed in the Dewvaporation technique because evaporation occurs on the air-liquid interface and not on the solid-liquid interface as in normal boiling techniques.; From material and energy balances, a theoretical model was developed which took into account all the resistances involved including liquid films, gas boundary layers, and plastic thickness. This model was compared to experimental data and it was deduced that, with a heat transfer coefficient of 2.7 Btu/hrft2oF, the effective heat transfer area was 25% of the total area. This reduction in area was due to the unbalanced airflow streamlines within the tower.; An economics analysis was performed with a basis of 1000 gallons per day plant to get a capital cost of {dollar}1900 and operating cost of {dollar}3.64. Based on the operating cost, the Dewvaporation technology was superior when compared to the other conventional technologies, which ranged from {dollar}4–{dollar}12 per 1000 gallons per day. Different methods and designs were identified in this study to improve the Dewvaporation technology. One of these methods was to use a desiccant heat exchanger instead of steam as an energy source. Mathematical analysis showed that the energy reuse factor increased by 50% for the Dewvaporation technology with desiccant heat exchanger. Also, a new design has been proposed to correct the unbalanced streamline airflow problem.