The　visualization　method　in　3D　simulation　is　established　to　investigate　the　spatial　distribution　of　film　thickness　and　local　heat　transfer　coefficient　to　avoid　the　dryout　phenomenon　and　improve　the　heat　transfer　performance.　The　simulated　results　are　in　good　agreement　with　the　experimental　data　in　the　literature.　The　results　indicate　that　the　spatial　distribution　of　liquid　film　is　peak-valley-peak,　and　there　exists　a　minimum　thickness.　The　change　path　of　the　hazardous　area　is　a　space　curve　rather　than　a　plane　curve.　The　film　thickness　with　dimensionless　axial　length　of　0.375　is　closest　to　the　average　film　thickness.　The　hazardous　area　approaches　the　inlet　column　as　the　tube　diameter　increases　in　the　axial　direction.　The　tube　diameter　has　a　great　influence　on　the　hazardous　area,　and　the　large　tube　diameter　promotes　it　to　move　to　the　inlet　column.　The　spatial　distribution　rule　of　the　local　heat　transfer　coefficient　is　the　same　as　that　of　film　thickness.　The　place　with　the　worst　heat　transfer　performance　is　approximately　in　the　same　position　as　the　place　with　the　thinnest　liquid　film.　The　results　provide　a　good　guidance　for　further　study　on　falling　film　process.　©　2019　Elsevier　Ltd