In　order　to　restrict　the　adverse　effects　caused　by　the　heat　transfer　deterioration　of　the　supercritical　fluid　and　to　build　a　cost-effective　Trans-critical　Organic　Ranke　Cycle　(TORC)　system,　the　heat　transfer　of　supercritical　R134a　was　experimentally　investigated　in　a　horizontal　ribbed　tube　for　the　first　time.　Knowledge　that　are　important　for　the　design　of　the　supercritical　heater　and　TORC　system　were　explored　in　detail,　including　the　general　features　of　the　heat　transfer　and　effects　of　heat　fluxes,　pressures,　and　mass　fluxes.　It　was　found　that　large　heat　flux　will　decrease　NU　in　most　cases,　and　the　effects　of　pressure　differed　largely　in　different　working　conditions.　The　working　conditions　with　low　heat　flux,　large　mass　flue　and　pressure　close　to　the　critical　pressure　were　recommended　for　the　design　of　the　supercritical　heater　and　TORC　system.　Compared　with　vertical　smooth　tubes,　the　threshold　for　heat　transfer　deterioration　criterion,　Bo,　was　enlarged　at　least　7.5　times　and　the　heat　transfer　was　improved　around　1.6　times　among　all　the　experimental　data.　Then,　different　types　of　previous　correlations　were　evaluated　and　none　of　them　showed　a　satisfactory　accuracy.　Finally,　new　correlations　with　better　prediction　accuracy　were　built　to　provide　references　for　the　TORC　system　design.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.