الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
With the increasing demand of fresh water, the disposal of the highly saline water resulting from seawater desalination plants has become a critical environmental problem. Salinity is measured by salt concentration in liter of water and expressed by g/L. Reverse osmosis (RO), the most leading worldwide desalination technique, cannot endure high salinity feed streams higher than 75 g/L (salt concentration). Membrane distillation (MD) techniques have been proving a capability to desalinate efficiently high salinity brines. Although direct contact MD at small lab-scale experiments has proven high productivity, it has experienced a considerable reduction in the desalinate water flux and a higher heat loss to the permeate side when scaled up to a pilot-scale level. The sweeping gas MD (SGMD) technique has a lower heat loss to the permeate side as air is used to carry the water vapor and this technique is rarely evaluated at larger scales. A small pilot-scale desalination device is designed and constructed as a testing facility for MD surface area of 1.17 m2 to analyze the performance of SGMD at a laboratory scale level. The unit is fully automated and consists of three interposed circuits including a feed side cycle for saline water, a permeate side cycle, and a refrigeration cycle to condense the vapor of pure water from the sweeping air. The device gives the flexibility to examine the performance of SGMD while changing the operating conditions independently. The test section in the pilot-scale unit is suitable to test various configurations of the MD (flat sheet, tubular, and hollow fiber bundles). The salinity level approached 140 g/L (approximately four times the seawater level) and the maximum temperature was set at 70℃. The resulted flux reached 13. 2 𝐿 𝑚2 ⁄ ℎ𝑟 and 9. 2 𝐿 𝑚2 ⁄ ℎ𝑟 at feed salinity of 35 g/L and 125 g/L with more than 99. 6% salt rejection, respectively at 70℃. The designed test rig can suit various operating conditions and other MD configurations as well.