Heat　dissipation　was　the　one　of　the　irreversible　losses　of　expanders.　For　small　capacity　expanders,　the　influence　of　it　on　the　performance　of　expanders　might　be　more　significant.　Single　screw　expander　(SSE)　was　a　type　of　volumetric　expander,　which　has　a　certain　advantages　in　the　Organic　Rankine　Cycle　system.　Investigating　the　characteristics　of　heat　transfer　in　SSE　was　necessary　because　of　the　influence　on　the　performance.　This　study　discussed　the　effect　of　heat　transfer　on　thermodynamic　performance　for　a　SSE.　Combined　leakage　and　heat　transfer,　the　thermodynamic　model　of　working　process　was　established　firstly.　Lubricating　oil　heat　absorption　was　considered　in　heat　transfer　model.　For　heat　transfer　in　the　body,　it　was　divided　into　17　parts　and　calculated　the　temperature　distribution　by　lumped　parameter　method.　The　coupling　model　was　computational　programmed　by　the　method　of　multiple　separate　solutions.　Then,　experimental　study　on　heat　dissipation　of　SSE　for　Organic　Rankine　Cycle　was　carried　out　and　verified　the　model.　R123　was　selected　as　working　fluid.　Finally,　the　influence　of　heat　transfer　on　the　performance　of　the　SSE　was　analyzed　from　different　influence　factors.　From　the　simulation　results,　the　range　of　heat　transfer　influence　for　the　power　was　from　1.91%　to　4.51%,　and　that　for　the　efficiency　was　from　2.72%　to　5.78%,　under　the　different　working　conditions.　Moreover,　the　effect　of　heat　transfer　on　performance　at　low　inlet　pressure　was　greater　than　that　at　high　inlet　pressure.　It　can　also　be　seen　that　the　effect　of　heat　transfer　on　the　efficiency　was　greater　than　that　on　the　power.　Therefore,　it　could　be　concluded　that　the　effect　of　heat　transfer　on　the　performance　of　SSEs　was　relatively　small.　(C)　2019　Elsevier　Ltd.　All　rights　reserved.