Novel　sinusoidal　wavy　microchannels　with　stepped　expansion　flow　passages　(SWM-SEFPs)　have　been　developed　to　enhance　the　heat　dissipation　and　inhibit　the　flow　boiling　instability　in　the　present　study.　Experiments　of　flow　boiling　in　rectangular　microchannels　(RMs),　sinusoidal　wavy　microchannels　(SWMs)　and　SWM-SEFPs　were　conducted　at　the　mass　flux　G　=　1056　-　2322　kg/(m2s)　and　the　effective　heat　flux　qeff　=　0　to　233.68　W/cm2.　The　working　fluid　is　HFE-7100.　The　measured　flow　boiling　characteristics　in　three　microchannels　are　compared　and　analyzed.　The　novel　SWM-SEFPs　can　dissipate　the　heat　flux　of　202.11　W/cm2　at　the　wall　superheat　of　39.12°C,　which　is　43.4%　greater　than　that　dissipated　by　the　RMs　at　G　=　2322　kg/(m2s).　The　maximum　heat　transfer　coefficient　(HTC)　of　13.84　kW/(m2K)　is　achieved　in　the　SWM-SEFPs.　HTCs　in　the　SWM-SEFPs　is　increased　by　48%　-　89.73%　as　compared　to　those　in　the　RMs.　The　SWMs　can　reduce　the　heating　film　temperatures　as　compared　to　the　RMs.　Furthermore,　the　temperature　oscillations　of　the　heating　film　and　physical　mechanisms　are　discussed　according　to　the　flow　patterns　and　image-based　analysis.　In　general,　the　temperatures　of　the　heating　film　increase　significantly　due　to　the　lack　of　liquid　on　the　inner　walls　of　microchannels　and　thus　significant　wall　temperature　fluctuations　occur.　The　SWM-SEFPs　can　prevent　the　backflow　and　reduce　the　wall　temperature　fluctuations.　©　2024