This　paper　presents　systematic　experiments　and　visualization　on　the　instabilities　of　phase-change　heat　transfer　for　water,　ethanol　and　acetone　in　a　flat　evaporator　of　a　two　phase　closed　system,　respectively.　The　effects　of　the　heat　flux,　filling　ratio,　coolant　temperature　and　working　fluid　type　on　the　instabilities　and　their　mechanisms　have　been　systematically　investigated.　The　experimental　results　show　that　the　instabilities　of　phase-change　heat　transfer　are　strongly　related　to　the　corresponding　heat　transfer　modes.　The　instabilities　of　temperature　and　heat　transfer　coefficient　(HTC)　of　the　evaporator　are　mainly　caused　by　the　bubble　behaviours,　the　physical　properties　and　the　operation　pressures.　Natural　convection,　intermittent　boiling　and　fully　developed　nucleate　boiling　are　the　main　heat　transfer　modes　in　the　present　study.　The　condensate　droplets　may　affect　the　instabilities　due　to　inducing　periodic　boiling　at　lower　heat　fluxes.　The　maximum　standard　deviations　of　the　evaporator　temperature　and　vapor　pressure　fluctuations　can　reach　3.1　degrees　C　and　0.8　kPa　respectively　during　the　intermittent　boiling.　There　is　no　intermittent　boiling　regime　for　ethanol　and　acetone　in　the　present　study.　Therefore,　no　instability　phenomena　of　nucleate　boiling　with　ethanol　and　acetone　are　observed　in　the　present　study.　(C)　2017　Published　by　Elsevier　Ltd.