The　organic　Rankine　cycle　(ORC)　can　be　used　to　recover　waste　heat　from　an　internal　combustion　engine.　In　such　a　system,　the　evaporator　design　is　critical.　Determining　the　amount　of　heat　that　can　be　transferred　in　a　designed　evaporator　is　extremely　important　for　a　successful　ORC　system.　In　this　paper,　the　performance　of　a　finned-tube　evaporator　used　to　recover　exhaust　waste　heat　from　a　diesel　engine　is　presented.　First,　the　exhaust　heat　of　the　chosen　diesel　engine　is　evaluated　based　on　the　measured　data.　Subsequently,　a　mathematical　model　of　the　evaporator　is　created　based　on　the　detailed　geometry　and　the　specific　ORC　working　conditions.　Then,　the　heat　transfer　of　the　evaporator　is　estimated　as　the　diesel　engine　runs　through　all　of　its　operating　regions　defined　by　the　engine　speed　and　the　engine　load.　The　results　show　that　the　exhaust　temperature　at　the　evaporator　outlet　increases　with　engine　speed　and　engine　load.　Although　the　convective　heat　transfer　coefficient　of　the　organic　working　fluid　is　significantly　larger　than　that　of　the　exhaust　gas,　the　overall　heat　transfer　coefficient　is　slightly　greater　than　that　of　the　exhaust　gas.　Furthermore,　the　heat　transfer　rate　is　the　greatest　in　the　preheated　zone　and　least　in　the　superheated　zone.　Consequently,　the　heat　transfer　area　for　the　preheated　zone　is　nearly　half　of　the　total　area.　In　addition,　the　area　of　the　superheated　zone　is　slightly　greater　than　that　of　the　two-phase　zone.　It　is　concluded　that　the　heat　transfer　area　for　a　finned　tube　evaporator　should　be　selected　carefully　based　on　the　engine＇s　most　typical　operating　region.　(C)　2012　Elsevier　Ltd.　All　rights　reserved.