Organic　Rankine　cycle　(ORC)　can　efficiently　recover　exhaust　heat　of　internal　combustion　engines　(ICEs).　Evaporator　is　an　important　component　that　determines　how　much　waste　heat　can　be　recovered.　Enhancing　heat　transfer　performance　and　reducing　flow　resistance　of　the　exhaust　in　the　evaporator　can　improve　not　only　heat-to-work　conversion　efficiency　of　the　ORC　system　but　also　reduce　the　influence　of　the　evaporator　on　the　operation　of　the　ICE.　Experimental　results　of　the　combined　diesel　engine-organic　Rankine　cycle　(DE-ORC)　system　showed　that　the　simulation　model　of　a　fin-and-tube　evaporator　is　established　via　computational　fluid　dynamic　method.　The　heat　transfer　performance　and　flow　state　of　exhaust　are　investigated　by　improving　the　structure　of　the　fin-and-tube　evaporator　under　typical　working　conditions　of　the　diesel　engine.　In　addition,　genetic　algorithm　is　used　to　optimize　the　evaporator　to　obtain　the　nonuniform　structure　of　the　evaporator.　Results　showed　that　the　performance　of　the　evaporator　can　be　improved　using　a　star-shaped　fin　and　appropriately　selected　parameters　of　elliptical　tube.　The　nonuniform　structural　evaporator　can　further　enhance　the　heat　transfer　performance　and　reduce　the　influence　of　the　ORC　system　on　the　operation　of　the　diesel　engine.　The　optimization　results　demonstrated　that　the　area　goodness　factor　(eta)　increases　by　173.76%　while　the　field　synergy　module　average　angle　(theta(phi　m))　and　friction　factor　f　reduces　by　6.17　degrees　and　56.67%,　respectively.　(C)　2021　Elsevier　Ltd.　All　rights　reserved.