Multiwall　carbon　nanotube　suspensions　(MWCNT　nanofluids)　are　used　in　an　intertube　falling-film　flow　to　explore　the　nanofluid　effects　on　heat　transfer　characteristics.　Water-based　and　ethylene-glycol-based　nanofluids　are　prepared　at　concentrations　of　0,　0.05,　0.14　and　0.24　vol%.　Thermal　conductivity　and　viscosity　of　these　nanofluids　is　measured.　Falling-film　heat　transfer　behavior　of　these　nanofluids　is　also　investigated　and　the　results　are　compared　to　those　of　the　base　fluids.　Based　on　the　same　liquid　feeding　flow　rate,　it　is　observed　that　the　heat　transfer　coefficients　of　the　water-based　nanofluids　decreases　then　increases　as　the　MWCNT　concentration　increases,　and　the　heat　transfer　coefficient　of　the　ethyleneglycol-based　nanofluids　decreases　with　an　increased　MWCNT　concentration.　A　model　is　provided　for　predicting　the　heat　transfer　enhancement　of　the　nanofluids　in　intertube　falling-film　flow,　and　an　agreement　between　predictions　and　experimental　data　is　obtained　for　nanofluids　with　larger　MWCNT　concentrations.　When　comparing　the　heat　transfer　coefficient　based　on　the　same　Reynolds　number,　up　to　20%　or　higher　heat　transfer　enhancement　can　be　observed　for　ethylene-glycol　based　nanofluids.　(C)　2012　Elsevier　Ltd.　All　rights　reserved.