In　this　paper　an　experimental　study　on　two-phase　flow　pressure　drop　characteristics　has　been　performed　in　a　triangular-array　rod　bundle　geometry　under　various　flow　conditions　(P　=　5–9　MPa　and　G　=　100–350　kg·m−2·s−1).　Total,　gravitational　and　frictional　pressure　drops　are　obtained　by　measurement　methods.　The　effects　of　pressure,　mass　flux　and　thermodynamic　quality　on　pressure　drop　were　investigated　in　detail,　and　the　proportions　of　gravitational　and　frictional　pressure　drop　in　total　pressure　drop　are　analyzed.　Meanwhile,　an　assessment　of　eight　existing　correlations　for　two-phase　friction　multiplier　calculation　is　carried　out　against　the　present　data.　The　results　show　that　Tran　correlation　has　a　relatively　better　performance　when　predicting　the　present　data,　while　the　accuracy　is　still　not　good　enough.　In　views　of　this,　a　newly-developed　correlation　based　on　the　Tran　correlation　has　been　proposed　for　the　two-phase　friction　multiplier　calculation　in　rod　bundle　geometries,　which　is　proved　to　agree　with　the　present　data　well.　©　2021　Elsevier　Ltd