The　present　paper　experimentally　investigates　the　thermal　performances　of　an　Organic　Rankine　Cycle　(ORC)　using　a　self-developed　single　screw　expander.　Experiments　were　conducted　to　study　the　net　efficiency　of　the　ORC　under　different　cooling　water　flows　in　different　seasons.　Taking　the　power　consumed　by　the　circulation　pump,　cooling　water　pump,　cooling　tower　fan　and　lubricant　oil　pump　into　account,　the　experimental　results　showed　that　the　maximum　value　of　produced　net　power　and　net　efficiency　achieved　3.27　kW　and　3.04%,　respectively,　obtained　at　a　cooling　water　flow　of　12　m(3)h(-1)　in　winter.　The　experimental　results　also　reported　that　the　shaft　power　and　shaft　efficiency　of　the　expander　increased　gradually　with　growth　of　cooling　water　flow.　Under　the　same　evaporating　temperature,　the　performances　of　the　ORC　system　deteriorated　with　the　increase　of　ambient　temperature,　and　the　net　efficiency　of　the　system　in　summer　was　decreased　by　more　than　16.45%　than　that　in　winter.　In　addition,　the　power　consumption　by　the　cooling　system　was　the　largest　factor　restricting　the　net　efficiency　than　the　power　consumption　by　other　auxiliary　machines.　Therefore,　reducing　the　power　consumption　by　the　cooling　system　can　effectively　enhance　the　net　efficiency　of　the　ORC　system.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.