Polymer　heat　exchangers　are　gaining　increasing　attention　in　the　field　of　air　cooling　applications.　This　paper　aims　to　present　a　parametrical　analysis　on　a　membrane-based　semi-direct　evaporative　cooler　(MSDEC)　with　internal　baffles.　A　mathematical　model　has　been　established　to　achieve　an　in-depth　understanding　of　the　heat　and　mass　transfer　process　of　the　proposed　MSDEC.　An　experimental　system　has　been　employed　to　study　the　evaporative　cooling　performance　of　the　hollow　fiber　module　and　validate　the　mathematical　process.　Simulation　results　demonstrated　that　the　installation　of　baffles　can　improve　the　wet-bulb　effectiveness　by　up　to　32%.　In　addition,　the　developed　model　is　adopted　to　study　the　air　treatment　performance　of　the　MSDEC　with　baffles　by　evaluating　the　influence　of　various　essential　parameters　including　the　fiber　length,　the　number　of　fiber　rows,　the　fiber　row　spacing,　the　geometrical　dimension　of　baffles,　and　the　inlet　air　velocity.　©　2020　Elsevier　B.V.