The　effect　of　fin　types-flat,　wavy　and　louver　fins-of　outdoor　fan-supplied　heat　exchanger　on　the　periodic　frosting　and　defrosting　performance　of　a　residential　air-source　heat　pump　was　experimentally　compared.　Six　consecutive　frosting/defrosting　cycles　were　performed　for　each　fin　type,　and　the　frosting/defrosting　durations　were　almost　equal,　about　46.6　min　and　3.9　min　for　each　fin　type,　due　to　the　same　defrosting　control　schemes.　The　time-average　values　during　the　third,　fourth　and　fifth　frosting/defrosting　cycles　were　used　to　compare　the　overall　frosting/defrosting　performance　among　three　fin　types,　and　the　real-time　data　during　the　fourth　cycle　were　analyzed　to　compare　their　dynamic　characteristics.　The　experimental　results　showed　the　flat　fin　had　the　best　thermal　performance　of　the　air-source　heat　pump,　followed　by　wavy　and　louver　fins.　The　time-average　heating　capacity,　COP　and　input　power　for　flat　fin　during　frosting　cycle　were　more　by　17.1%,　9.0%　and　7.6%,　respectively　than　those　for　louver　fin.　The　frosting　curves　for　flat　fin　increased　slightly　and　then　decreased　gradually,　while　the　curves　for　wavy　and　louver　fin　types　increased　slightly　at　first,　then　decreased　rapidly　and　gradually　at　last.　Meanwhile,　the　curves　for　louver　fin　decreased　considerably　earlier　than　those　for　wavy　fin.　The　initial　increases　of　the　frosting　curves　were　ascribed　to　that　the　positive　frost　effect　of　increased　surface　roughness　surpassed　both　the　negative　frost　effects　of　increased　frost　layer　thermal　resistance　and　reduced　fan-supplied　airflow　rate　due　to　frost　blockage.　The　frosting　curves　for　wavy　and　louver　fin　types　decreased　rapidly　because　the　outdoor　axial　fan　experienced　the　stall　zone　caused　by　more　frost　accumulation　and　greater　air　pressure　drop,　and　decreased　slightly　at　last　after　the　stall　zone　was　went　through.　The　frosting　curves　for　flat　fin　decreased　always　slightly　because　the　outdoor　axial　fan　did　not　experience　the　stall　zone　during　the　frosting　duration　of　46.6　min.　The　frosted　finned-tube　heat　exchanger　and　fan　characteristic　should　be　coupled　together　for　the　optimal　design.　(C)　2013　Elsevier　Ltd.　All　rights　reserved.