The　effects　of　the　membrane　characteristics　and　operational　conditions　on　the　vapor　flux　and　thermal　efficiency　in　a　direct　contact　membrane　distillation　(DCMD)　process　were　studied　with　a　mathematical　simulation.　The　membrane　temperature,　driving　force　of　vapor　transfer,　membrane　distillation　coefficient,　etc.　were　used　to　analyze　the　effects.　The　operating　conditions　that　increased　the　vapor　flux　improved　the　thermal　efficiency.　The　membrane　characteristics　of　four　microporous　membranes　and　their　performances　in　DCMD　were　compared.　A　polysulfone　(PSf)　membrane　prepared　via　vapor-induced　phase　separation　exhibited　the　lowest　thermal　conductivity.　The　PSf　and　polyvinylidene　difluoride　(PVDF)　membranes　were　modified　using　SiO2　aerogel　blending　and　coating　to　reduce　the　thermal　conductivity　of　the　membrane.　The　coating　process　was　more　effective　than　the　blending　process　toward　this　end.　The　changes　in　the　structure　of　the　modified　membrane　were　observed　with　a　scanning　electron　microscope.　Si　was　found　on　the　modified　membrane　surface　with　an　energy　spectrometer.　The　PVDF　composite　and　support　membranes　were　tested　during　the　DCMD　process;　the　composite　membrane　had　a　higher　vapor　flux　and　a　better　thermal　efficiency　than　the　support.　A　new　method　based　on　a　3o)　technique　was　used　to　measure　the　thermal　conductivity　of　the　membranes.　(C)　2014　Elsevier　BY.　All　rights　reserved.