The　need　to　understand　the　flow　behavior　and　film　thickness　in　the　single　screw　expander　is　very　crucial　since　it　is　known　to　be　a　complex　system　due　to　the　existence　of　various　flow　patterns.　The　present　work　reports　a　computational　fluid　dynamic　analysis　of　two-phase　flow　behavior　and　film　thickness　through　a　vertical　helical　rectangular　channel　using　the　volume　of　fluid　(VOF)　model.　The　numerical　model　is　validated　against　available　experimental　data　of　annular　flow　in　the　helical　rectangular　channel.　The　numerical　predictions　of　velocity　field,　pressure　field　and　liquid　phase　distribution　are　presented　as　each　fluid　flows　into　the　helical　channel.　It　is　found　that　the　inlet　flow　inclined　angle　has　a　significant　influence　on　the　liquid　film　distribution　at　the　outer　side　of　the　helical　channel.　The　effects　of　curvature　ratio　and　dimensionless　pitch　on　the　liquid　film　distribution,　film　thickness　and　liquid　holdup　are　illustrated　in　detail.　In　addition,　the　new　relationship　between　the　average　liquid　film　thickness　and　the　liquid　holdup　is　also　given,　and　these　results　are　necessary　for　the　optimization　design　of　the　single　screw　expander　prototype.　©　2020　Elsevier　Ltd