Tests　were　conducted　to　study　the　evaporation　processes　from　nanoporous　membranes　using　FC72.The　heat　transfer　characteristics　of　two　facing　directions:membrane　facing　upward　and　downward,　were　compared.Results　showed　that　the　heat　fluxsuperheat　curves　for　two　directions　presented　a　similar　variation　trend,　and　there　existed　a＇thin　film　evaporation＇　stage　where　heat　flux　increased　while　temperature　remained　constant.The　temperature　was　stable　in　low　heat　flux.The　heat　transfer　performance　of　downwardfacing　membrane　was　better　than　that　of　upwardfacing　membrane　at　different　heat　flux　levels.This　was　caused　by　the　effect　of　gravity　on　the　liquid　supply　and　the　effect　of　liquid　film　thickness　on　thermal　resistance.As　the　heat　flux　increased,　the　temperature　fluctuated　more　sharply,　eventually　a　temperature　peak　appeared.The　critical　heat　flux　reached　59　W/cm2　and　47　W/cm2　for　downward　and　upward　facing　membranes,　respectively.Additionally,　theoretical　modeling　of　the　evaporation　processes　was　carried　out,　and　it　was　found　that　the　evaporation　coefficients　were　0.043　1　and　0.021　9,　respectively.　©　2022,　Editorial　Department　of　Journal　of　Aerospace　Power.　All　right　reserved.